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Full text of "NEMA MG-1: Motors and Generators"

*********A********* 





By Authority Of 

THE UNITED STATES OF AMERICA 

Legally Binding Document 



By the Authority Vested By Part 5 of the United States Code § 552(a) and 
Part 1 of the Code of Regulations § 51 the attached document has been duly 
INCORPORATED BY REFERENCE and shall be considered legally 
binding upon all citizens and residents of the United States of America. 
HEED THIS NOTICE : Criminal penalties may apply for noncompliance. 




Document Name : NEMA MG- 1 : Motors and Generators 



CFR Section(s) : 1 CFR 43 1 



Standards Body: National Electrical Manufacturers Association 



NEMA MG 1 

Motors 

and 

Generators 



NEMA Standards Publication MG 1-2009 

Motors and Generators 



Published by: 

National Electrical Manufacturers Association 

1300 North 17th Street, Suite 1752 
Rosslyn, VA 22209 

www.nema.org 



© Copyright 2009 by the National Electrical Manufacturers Association. All rights including 
translation into other languages, reserved under the Universal Copyright Convention, the Berne 
Convention for the Protection of Literary and Artistic Works, and the International and Pan 
American Copyright Conventions. 



NOTICE AND DISCLAIMER 

The information in this publication was considered technically sound by the consensus of persons 
engaged in the development and approval of the document at the time it was developed. 
Consensus does not necessarily mean that there is unanimous agreement among every person 
participating in the development of this document. 

The National Electrical Manufacturers Association (NEMA) standards and guideline publications, 
of which the document contained herein is one, are developed through a voluntary consensus 
standards development process. This process brings together volunteers and/or seeks out the 
views of persons who have an interest in the topic covered by this publication. While NEMA 
administers the process and establishes rules to promote fairness in the development of 
consensus, it does not write the document and it does not independently test, evaluate, or verify 
the accuracy or completeness of any information or the soundness of any judgments contained in 
its standards and guideline publications. 

NEMA disclaims liability for any personal injury, property, or other damages of any nature 
whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly 
resulting from the publication, use of, application, or reliance on this document. NEMA disclaims 
and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of 
any information published herein, and disclaims and makes no warranty that the information in 
this document will fulfill any of your particular purposes or needs. NEMA does not undertake to 
guarantee the performance of any individual manufacturer or seller's products or services by 
virtue of this standard or guide. 

In publishing and making this document available, NEMA is not undertaking to render 
professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to 
perform any duty owed by any person or entity to someone else. Anyone using this document 
should rely on his or her own independent judgment or, as appropriate, seek the advice of a 
competent professional in determining the exercise of reasonable care in any given 
circumstances. Information and other standards on the topic covered by this publication may be 
available from other sources, which the user may wish to consult for additional views or 
information not covered by this publication. 

NEMA has no power, nor does it undertake to police or enforce compliance with the contents of 
this document. NEMA does not certify, test, or inspect products, designs, or installations for 
safety or health purposes. Any certification or other statement of compliance with any health or 
safety-related information in this document shall not be attributable to NEMA and is solely the 
responsibility of the certifier or maker of the statement. 



MG 1-2009 
Summary of Changes, Page 1 

Changes made for MG 1-2009 are marked by a red line to the left of the changed 
material 

Note — Where text has been revised in more than one version, only the most recent is color-coded 
1 Example of change made for MG 1-2009 

Section I, Part 1 

1.1 Added: Reference to IEC 60034-30-2008 
1.16 Deleted section 

1.41.3 Added: Premium Efficiency Motor 

Section I, Part 2 

2.2 Added: "To prevent confusion with the numerals 1 and 0, the letters "I" and "O" shall not 
be used." 

Updated footnote references 

Added and revised markings 

Added: Reference to 2.67 for auxiliary devices 
2.60. 1 .2 Revised Figure 2-48B for clarity 

2.67 Added: Auxiliary Devices (entire section) 

Section I, Part 4 

Table 4-2 Dimension revised in column 6 

Section II, Part 10 

Table 10-5 Adjusted table 

Section II, Part 12 

12.41 In table, corrected synchronous speed of the 50 Hz machine 

12.60.3 Added: Additional paragraphs, equation, and table 

Table 12-14 Replaced Table 12-14 

12.62 Revised 12.62a 

For 12.62b and 12.62d, revised minimum insulation resistance 
Added: Note 

12.63 Note 2: Updated reference to 20.8 

Section II, Part 13 

1 3.2 Revised frame size 

Section II, Part 18: 

18.131 Figure 18-16: Dimension revised to 5.875 

Section III, Part 20: 

20.18.1 Revised 20.18.1a 

For 20.18.1b and 20.18.1d, revised minimum insulation resistance 

20.18.2 Revised 20.18.2a 

For 20.18.2b and 20. 18. 2d, revised minimum insulation resistance 
Added: Note 

Section IV, Part 30: 

Table 30-1 Revised footnote G.1 reference to 12.53 



MG 1-2009 

Summary of Changes, Page 2 

Changes made for MG 1-2006 Revision 1, published Nov. 20, 2007 (includes MG 1- 
2006 Errata) are marked by a blue line to the left of the changed material 

Note—Where text has been revised in more than one version, only the most recent is color-coded 
| Example of change made for MG 1-2006 Revision 1 

Contents 

Entire Table of Contents was revised due to added sections and repagination 

Section I, Part 1 

1 16 NEMA PREMIUM® EFFICIENCY ELECTRIC MOTOR 

Changed™ to® 
Deleted general paragraph, added: 

1.16.1 60 Hz 

1.16.2 50 Hz 

Section l f Part 2 

2.2 TERMINAL MARKINGS Footnotes 

2.20.2 Induction Machines 

2.24 DIRECTION OF ROTATION 

2.60.1.1 Terminal Markings Using "T" 

2.60.1 .2 Terminal Markings in Accordance with I EC 60034-8 Using U, V, W 
FIGURE 2-48B Added figure 

2.61.6 Sixth 

Revised text 



Section I, Part 3 

3.1 .8 Accessories and Components 

Inserted sentence 

Section I , Part 4 

4.9.4 Parallelism of Keyseats to Shaft Centerline 

4.9.5 Lateral Displacement of Keyseats 
Figure 4-7 Corrected specifications 

4.9.8 Shaft Extension Key(s) 

Table 4-7 Corrected specifications 

Section II, Part 10 Ratings— AC Motors 

1 0.38 NAMEPLATE TEMPERATURE RATINGS FOR ALTERNATING-CURRENT SMALL AND 

UNIVERSAL MOTORS 
Corrected reference 12.42.3 

10.40.1 Medium Single-Phase and Polyphase Squirrel-Cage Motors 
Corrected references in text and footnote 2 

10.42.2 Polyphase Wound-Rotor Motors 
Corrected references in text 

Section II, Part 10 Ratings— DC Motors 

10.66.2 Small Motors Except Those Rated 1/20 Horsepower and Less 

Corrected footnote references 



MG 1-2009 
Summary of Changes, Page 3 

Section II, Part 12 Ratings Tests and Performance —AC Motors 

12.42.4 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0° C 

(Added section) 
12.43.2 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 

Below 0° C 

(Added section) 
12.60 EFFICIENCY LEVEL OF PREMIUM EFFICIENCY ELECTRIC MOTORS 

(Added ©throughout) 
Tables 12-12 through 12-14 (Added ®) 
12-13 FULL-LOAD EFFICIENCIES FOR 60 HZ NEMA PREMIUM® EFFICIENCY ELECTRIC 

MOTORS (Added ®), edited table title 

12.62 MACHINE WITH ENCAPSULATED OR SEALED WINDINGS— CONFORMANCE 

TESTS 

(Clarified text in b and d) 

Section II, Part 12 Ratings Tests and Performance —DC Motors 

12.67.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0° C 

Added section 

Section II, Part 15 

1 5.41 .2 Temperature Rise for Ambients Higher than 40°C 

Added section 

Section III, Part 20 

20.8.1 Machines with a 1 .0 Service Factor at Rated Load 
Corrected reference in footnote 

20.8.2 Machines with a 1 .15 Service Factor at Service Factor Load 
Corrected reference in footnote 

20. 1 8. 1 Test for Stator Which Can Be Submerged 
Clarified text in b and d 

20.18.2 Test for Stator Which Can Be Submerged 
Clarified text in b and d 

Section III, Part 20 

21.10.5 Temperature Rise for Air-Cooled Motors for Ambients Lower than 40° C, but Not Below 

0°C 
Deleted lower ambients in a and b 

21 .28.3 Unusual Service Conditions 
Corrected references in subclause b. 

21 .37 COMPRESSOR FACTORS 
O o rrscted ref e re nee 

21 .38 SURGE CAPABILITIES OF AC WINDINGS WITH FORM-WOUND COILS 
Corrected reference 

Section III, Part 23 

23.9.3 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0° C 

Added section 

Section HI, Part 24 

24.40.3 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 

Below 0° C 
Added section 



MG 1-2009 

Summary of Changes, Page 4 

Section IV, Part 31 

31.4.1.6 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 

Below 0° C 
Added section 

Section IV, Part 32 

Table 32-3 corrected reference 

32.6.2 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 

Below 0° C 

Added section 
32.26 GENERATOR TERMINAL HOUSING 

Added "housing" 

Section IV, Part 33 

33.3.2.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 

Below 0° C 
Added section 



MG 1-2009 
Summary of Changes, Page 5 

Changes made for MG 1-2003 Revision 2, published as MG 1-2006, are marked by 
a purple line to the left of the changed material 

Note— Where text has been revised in more than one version, only the most recent is color-coded 
1 Example of change made for MG 1-2003 Revision 2, published as MG 1-2006 

Section I, Part 1 

1 .1 Referenced Standards updated to reflect current editions 

1 70 NAMEPLATE MARKING 

Entire section added 

Section I, Part 3 

3.1 .8 Accessories and Components 

Correction 
3.1.11 Tests of an Assembled Group of Machines and Apparatus 

Correction 



Section I, 


Part 4 


4.4.1 


Dimensions for Alternating-Current Foot-Mounted Machines with Single Straight-Shaft 




Extension 




Notes correction 


4.4.2 


Notes correction 


4.4.3 


Notes correction 


4.5.1 


Notes correction 


4.5.2 


Notes correction 


4.5.3 


Notes 


4.9.3 


Bottom of Keyseat to Shaft Surface 


Figure 4-7 


Corrected dimension 


4.9.8 


Shaft Extension Key(s) 




correction 


Section I, 


Part 9 



9.1 SCOPE 

changed "electrical motors" to "machines" 
9.4 METHODS OF MEASUREMENT 

updated references to ANSI standards 

"The" (added; "Either" deleted) method specified in ANSI S12.56 may be used. 

Corrected reference to 9.6.2b 

Updated ANSI standard references; added third column 



9.4.2 


9.6.2 


Table 9-4 


Section I 


10.39 


10.39.6 


10.40.1 



corrected section reference 

deleted 

Medium Single-Phase and Polyphase Squirrel-Cage Motors 

corrected section reference 
10.66 NAMEPLATE MARKING 

correction 
10.66.3 Medium Motors 

correction 

Section II, Part 12 

12.3 HIGH-POTENTIAL TEST VOLTAGES FOR UNIVERSAL, INDUCTION, AND DIRECT- 

CURRENT MOTORS 



MG 1-2009 

Summary of Changes, Page 6 

Corrections to Effective Test Voltage 
Corrections to Note 3 — 80 percent 
12.35 LOCKED-ROTOR CURRENT OF 3-PHASE SMALL AND MEDIUM SQUIRREL-CAGE 

INDUCTION MOTORS 
deleted reference "60-hertz" and "rated at 230 volts" 

12.40.1 Design A and B Motors 

The pull-up torque of Design A and B 
Added: 60- and 50-hertz 

12.40.2 Design C Motors 

The pull-up torque of Design C 

Added: 60- and 50-hertz, single speed, polyphase squirrel-cage medium motors 
12.54.1 Normal Starting Conditions 

12.54.3 Considerations for Additional Starts 
Table 1 2-7 SQUIRREL-CAGE INDUCTION MOTORS 

Revised specifications 

Section II, Part 14 

14.43 ASEISMATIC CAPABILITY 

Table 14-1 MEDIUM MOTORS— POLYPHASE INDUCTION 

Correction to conventional specifications 

Section II, Part 15 

15.12 NAMEPLATE MARKING 

Section II Part 18 

Added and corrected headers throughout (editorial) 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 
SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND 
EVAPORATOR FANS 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 
SMALL MOTORS FOR HOME LAUNDRY EQUIPMENT 
MEDIUM AC POLYPHASE ELEVATOR MOTORS 
MEDIUM AC CRANE MOTORS 

MEDIUM SHELL-TYPE MOTORS FOR WOODWORKING AND MACHINE- 
TOOL APPLICATIONS 
18.9 VARIATIONS 

updated reference to 12.44 
1 8.27 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
1 8.41 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
1 8.52 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
1 8.74 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
18.101 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
18.111 NAMEPLATE MARKING 

18.116 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
18.128 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
18.142 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 



MG 1-2009 
Summary of Changes, Page 7 

18.152 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

18.153 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

18.165 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

18.166 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

18.177 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

18.178 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

1 8.21 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
updated reference to 12.44 

1 8.21 1 NAMEPLATE MARKING 

18.216 NAMEPLATE MARKING (Revised reference) 

1 8.225 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
1 8.230 DIMENSIONS AND TOLERANCES FOR ALTERNATING-CURRENT OPEN AND 

TOTALLY ENCLOSED WOUND-ROTOR CRANE MOTORS HAVING ANTIFRICTION 

BEARINGS 

Deleted note 
1 8.247 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

updated reference to 12.44 
18.264 NAMEPLATE MARKING 

1 8.269. 1 AC Torque Motors 

1 8.269.2 DC Torque Motors 

Section III Part 20 

20.5 VOLTAGE RATINGS (complete replacement of existing text) 

20.7.3.1 General 

20.8.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0°C 

Added section 

20.10.3 Motor Torques When Customer Specifies A Custom Load Curve 
Added 

20.10.4 Motor with 4.5 pu and Lower Locked-Rotor Current 
Added 

20.1 1 LOAD WK2 FOR POLYPHASE SQUIRREL-CAGE INDUCTION MOTORS 

20.24.2 Voltage Unbalance Defined 
Corrected specification in example 

20.25 For some examples of additional information that may be included on the nameplate see 

1.70.2. 

20.25.5 Deleted 

20.27 EMBEDDED TEMPERATURE DETECTORS 

Revised text and dimensions in table 

20.31 .3 Units for Capability Requirements 
20.35.8 Test Voltage Values 

Section III Part 21 

21.5 VOLTAGE RATINGS 

Revised specification 

21.5.1 Voltage Ratings 
Added 

21.5.2 Preferred motor output/voltage rating 
Added 



MG 1-2009 

Summary of Changes, Page 8 

21.8.3.1 General 

21.10.5 Temperature Rise for Air-Cooled Motors for Ambients Lower than 40° C, but not Below 0° 

C 

Added section 
21.11 deleted text 

21.11.1 General 
Added 

21.11.2 Motor Torques When Customer Supplies Load Curve 

21.25 For some examples of additional information that may be included on the nameplate see 

1.70.2. 
Added 

Section III Part 23 

23.13 EFFICIENCY 

23.24 For some examples of additional information that may be included on the nameplate see 

1.70.2. 

Added 

Section III Part 24 

24.61 NAMEPLATE MARKING 

Section IV Part 30 

30. 1 .3 Power Factor Correction 

Figure 30-2 THE EFFECT OF REDUCED COOLING ON THE TORQUE CAPABILITY AT REDUCED 

SPEEDS OF 60 HZ NEMA DESIGN A AND B MOTORS 
30.2.2.2.4 Motor Torque During Operation Above Base Speed 

30.2.2.8 Voltage Stress 

Section IV Part 31 

31 .5.1 Variable Torque Applications 

Section IV Part 30 

32.24 NAMEPLATE MARKING 

Revised additional information 

Section IV Part 30 

33.3.2.2 Embedded Temperature Detectors 

Index 

Revised references throughout 



MG 1-2009 
Summary of Changes, Page 9 

Changes made for MG 1-2003, Revision 1-2004 are marked by a green line to the 
left of the changed material 

Note — Where text has been revised in more than one version, only the most recent is color-coded 
( Example of change made for MG 1-2003 Revision 1-2004 



Contents 



Section I, Part 

5.1 

5.3.4 

5.4.1 

5.6 

5.7 

Table 5-3: 

5.8.1 

5.8.2.1 

5.8.2.2 

Figure 5-1: 

Figure 5-2 

Figure 5-3 

Figure 5-4 

Figure 5-5 

Figure 5-6 



pages vn, vm, xn, xv, xxvn 

5 

Scope 

Table 5-1 

Indication of Degree of Protection 

GENERAL REQUIREMENTS FOR TESTS 

TESTS FOR FIRST CHARACTERISTIC NUMERAL 

TEST AND ACCEPTANCE CONDITIONS FOR FIRST CHARACTERISTIC NUMERAL 

Test Conditions 

Allowable Water Leakage 

Post Water Electrical Test 

STANDARD TEST FINGER NOTES— 



Added 
Added 
Added 
Added 
Added 



(Reproduced with permission of the IEC, which retains the copyright.) 
(Reproduced with permission of the IEC, which retains the copyright.) 
(Reproduced with permission of the IEC, which retains the copyright.) 
(Reproduced with permission of the IEC, which retains the copyright.) 
(Reproduced with permission of the IEC, which retains the copyright.) 



Section II, Part 12 

12.51 .1 General-Purpose Alternating-Current Motors of the Open Type 

Table 12-4 Note: *ln the case of polyphase squirrel-cage motors, these service factors apply only to 
Design A, B, and C motors. 

12.51.2 Other Motors 

12.58.2 Efficiency of Polyphase Squirrel-Cage Medium Motors with Continuous Ratings 

Section II DC SMALL AND MEDIUM MOTORS 

Added Header (editorial) to odd pages 

Section II, Part 14 

14.3 UNUSUAL SERVICE CONDITIONS 

b. Operation where: (revised text) 
1 . There is excessive departure from rated voltage or frequency, or both (see 12.44 

for alternating current motors and 12.68 for direct-current motors) 
3. The alternating-current supply voltage is unbalanced by more than 1 percent 

(see 12.45 and 14.36) 
14.42 APPLICATION OF V-BELT SHEAVES TO ALTERNATING CURRENT MOTORS 

HAVING ANTIFRICTION BEARINGS 

14.42.1 Dimensions 

14.42.1.1 Selected Motor Ratings 

1 4.42. 1 .2 Other Motor Ratings 

14.42.2 Radial Overhung Load Limitations 

Table 14-1 Note: The width of the sheave shall be not greater than that required to transmit the 

indicated horsepower but in no case shall it be wider than 2(N-W) - 0.25. 
Table 14-1 A Added 2004 



Section III, Part 20 

20.17.2 Test Voltage — Primary Windings Footnote 



MG 1-2009 

Summary of Changes, Page 10 



Section III, Part 21 

21.35.1 Undamped Natural Frequency 

Section IV, Part 30 

30.0 SCOPE 



30.2.2.2.2 Torque Derating Based on Reduction in Cooling 

30.2.2.2.4 Motor Torque During Operation Above Base Speed 

Figure 30-4 Notes 

Figure 30-4 Note: a. Standard NEMA Design A and B motors in frames per Part 13. 



Index 



Revised references on pages 3, 4, 5 



MG 1-2009 
Page i 



CONTENTS 



Page No. 

Foreword xxxv 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 1— REFERENCED STANDARDS AND DEFINITIONS 1-1 

1.1 REFERENCED STANDARDS 1-1 

DEFINITIONS , 1-5 

CLASSIFICATION ACCORDING TO SIZE 1-5 

1.2 MACHINE 1-5 

1.3 SMALL (FRACTIONAL) MACHINE 1-5 

1.4 MEDIUM (INTEGRAL) MACHINE , 1-5 

1.4.1 Alternating-Current Medium Machine 1-5 

1.4.2 Direct-Current Medium Machine 1-5 

1.5 LARGE MACHINE 1-5 

1.5.1 Alternating-Current Large Machine 1-5 

1.5.2 Direct-Current Large Machine 1-6 

CLASSIFICATION ACCORDING TO APPLICATION 1-6 

1.6 GENERAL PURPOSE MOTOR 1-6 

1.6.1 General-Purpose Alternating-Current Motor 1-6 

1.6.2 General-Purpose Direct-Current Small Motor 1-6 

1.7 GENERAL-PURPOSE GENERATOR 1-6 

1.8 INDUSTRIAL SMALL MOTOR 1-6 

1.9 INDUSTRIAL DIRECT-CURRENT MEDIUM MOTOR 1-6 

1.10 INDUSTRIAL DIRECT-CURRENT GENERATOR 1-6 

1.11 DEFINITE-PURPOSE MOTOR 1-7 

1.12 GENERAL INDUSTRIAL MOTORS 1-7 

1.13 METAL ROLLING MILL MOTORS 1-7 

1.14 REVERSING HOT MILL MOTORS 1-7 

1.15 SPECIAL-PURPOSE MOTOR 1-7 

CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 1-8 

1.17 GENERAL 1-8 

1.17.1 Electric Motor 1-8 

1.17.2 Electric Generator 1-8 

1.17.3 Electric Machines 1-8 

1.18 ALTERNATING-CURRENT MOTORS 1-9 

1.18.1 Induction Motor 1-9 

1.18.2 Synchronous Motor 1-9 

1.18.3 Series-Wound Motor 1-10 

1.19 POLYPHASE MOTORS 1-10 

1.19.1 Design Letters of Polyphase Squirrel-Cage Medium Motors 1-10 

1.20 SINGLE-PHASE MOTORS 1-10 

1.20.1 Design Letters of Single-Phase Small Motors 1-10 

1.20.2 Design Letters of Single-Phase Medium Motors 1-11 

1.20.3 Single-Phase Squirrel-Cage Motors 1-11 

1 .20.4 Single-Phase Wound-Rotor Motors 1-12 

1.21 UNIVERSAL MOTORS 1-12 

1.21.1 Series-Wound Motor 1-12 

1.21.2 Compensated Series-Wound Motor 1-12 

1.22 ALTERNATING-CURRENT GENERATORS 1-12 

1.22.1 Induction Generator 1-12 

1.22.2 Synchronous Generator 1-13 

1.23 DIRECT-CURRENT MOTORS 1-13 

1.23.1 Shunt-Wound Motor 1-13 

1.23.2 Series-Wound Motor 1-13 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page ii 

1.23.3 Compound-Wound Motor 1-13 

1.23.4 Permanent Magnet Motor 1-13 

1.24 DIRECT-CURRENT GENERATORS 1-13 

1.24.1 Shunt-Wound Generator 1-13 

1.24.2 Compound-Wound Generator 1-13 

CLASSIFICATION ACCORDING TO ENVIRONMENTAL PROTECTION AND METHODS 

OF COOLING 1-14 

1.25 OPEN MACHINE (IP00, IC01) 1-14 

1.25.1 Dripproof Machine (IP1 2, IC01) 1-14 

1.25.2 Splash-Proof Machine (IP13, IC01) 1-14 

1.25.3 Semi-Guarded Machine (IC01) 1-14 

1.25.4 Guarded Machine (IC01) 1-14 

1.25.5 Dripproof Guarded Machine (IC01) 1-17 

1.25.6 Open Independently Ventilated Machine (IC06) 1-17 

125.7 Open Pipe-Ventilated Machine 1-17 

125.8 Weather-Protected Machine 1-17 

126 TOTALLY ENCLOSED MACHINE 1-17 

126.1 Totally Enclosed Nonventilated Machine (IC410) 1-17 

126.2 Totally Enclosed Fan-Cooled Machine 1-17 

1.26.3 Totally Enclosed Fan-Cooled Guarded Machine (IC411) 1-18 

126.4 Totally Enclosed Pipe-Ventilated Machine (IP44) 1-18 

1.26.5 Totally Enclosed Water-Cooled Machine (IP54) 1-18 

1.26.6 Water-Proof Machine (IP55) 1-18 

1.26.7 Totally Enclosed Air-to-Water-Cooled Machine (IP54) 1-18 

1.26.8 Totally Enclosed Air-to-Air-Cooled Machine (IP54) 1-18 

1.26.9 Totally Enclosed Air-Over Machine (IP54, IC417) 1-18 

1.26.10 Explosion-Proof Machine 1-19 

1.26.11 Dust-Ignition-Proof Machine 1-19 

1.27 MACHINE WITH ENCAPSULATED OR SEALED WINDINGS 1-19 

1.27.1 Machine with Moisture Resistant Windings 1-19 

127.2 Machine with Sealed Windings 1-19 

CLASSIFICATION ACCORDING TO VARIABILITY OF SPEED 1-19 

1.30 CONSTANT-SPEED MOTOR 1-19 

1.31 VARYING-SPEED MOTOR 1-19 

132 ADJUSTABLE-SPEED MOTOR 1-20 

133 BASE SPEED OF AN ADJUSTABLE-SPEED MOTOR 1-20 

134 ADJUSTABLE VARYING-SPEED MOTOR 1-20 

1.35 MULTISPEED MOTOR 1-20 

RATING, PERFORMANCE, AND TEST 1-20 

1.40 RATING OF A MACHINE 1-20 

1.40.1 Continuous Rating 1-20 

1.40.2 Short-Time Rating 1-20 

1.41 EFFICIENCY 1-20 

1.41.1 General 1-20 

1.41.2 Energy Efficient Polyphase Squirrel-Cage Induction Motor 1-20 

1.41.3 Premium Efficiency Motor 1-21 

1.42 SERVICE FACTOR— AC MOTORS 1-21 

1.43 SPEED REGULATION OF DC MOTORS 1-21 

143.1 Percent Compounding of Direct-Current Machines 1-21 

1.44 VOLTAGE REGULATION OF DIRECT-CURRENT GENERATORS 1-21 

1.45 SECONDARY VOLTAGE OF WOUND-MOTOR ROTORS 1-21 

1.46 FULL-LOAD TORQUE 1-21 

147 LOCKED-ROTOR TORQUE (STATIC TORQUE) 1-21 

148 PULL-UP TORQUE 1-21 

1.49 PUSHOVER TORQUE 1-21 

1.50 BREAKDOWN TORQUE 1-22 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page iii 

1.51 PULL-OUT TORQUE 1-22 

1.52 PULL-IN TORQUE 1-22 

1.53 LOCKED-ROTOR CURRENT 1-22 

1.54 NO-LOAD CURRENT 1-22 

155 TEMPERATURE TESTS 1-22 

1.56 AMBIENT TEMPERATURE 1-22 

1.57 HIGH-POTENTIAL TESTS 1-22 

1.58 STARTING CAPACITANCE FOR A CAPACITOR MOTOR 1-22 

1.59 RADIAL MAGNETIC PULL AND AXIAL CENTERING FORCE 1-23 

1.59.1 Radial Magnetic Pull 1-23 

1.59.2 Axial Centering Force 1-23 

1.60 INDUCTION MOTOR TIME CONSTANTS 1-23 

1.60.1 General 1-23 

1.60.2 Open-Circuit AC Time Constant 1-23 

1.60.3 Short-Circuit AC Time Constant 1-23 

1.60.4 Short-Circuit DC Time Constant 1-23 

1.60.5 X/R Ratio 1-23 

1.60.6 Definitions (See Figure 1-4) 1-23 

COMPLETE MACHINES AND PARTS 1-24 

1.61 SYNCHRONOUS GENERATOR— COMPLETE 1-24 

1.61.1 Belted Type 1-24 

1.61.2 Engine Type 1-24 

1.61.3 Coupled Type 1-24 

1.62 DIRECT-CURRENT GENERATOR— COMPLETE 1-24 

1.62.1 Belted Type 1-24 

1.62.2 Engine Type 1-24 

1.62.3 Coupled Type 1-24 

1.63 FACE AND FLANGE MOUNTING 1-25 

1.63.1 Type C Face 1-25 

1.63.2 Type D Flange 1-25 

1.63.3 Type P Flange 1-25 

CLASSIFICATION OF INSULATION SYSTEMS 1-25 

1.65 INSULATION SYSTEM DEFINED 1-25 

1.65.1 Coil Insulation with its Accessories 1-25 

1.65.2 Connection and Winding Support Insulation 1-25 

1.65.3 Associated Structural Parts 1-25 

1.66 CLASSIFICATION OF INSULATION SYSTEMS 1-25 

MISCELLANEOUS 1-26 

1.70 NAMEPLATE MARKING 1-26 

1.70.1 Nameplate 1-26 

1.70.2 Additional Nameplate Markings 1-26 

171 CODE LETTER 1-27 

1.72 THERMAL PROTECTOR 1-27 

1.73 THERMALLY PROTECTED 1-27 

1.74 OVER TEMPERATURE PROTECTION 1-27 

1.75 PART-WINDING START MOTOR 1-27 

1.76 STAR (WYE) START, DELTA RUN MOTOR 1-27 

1.77 CONSTANT FLUX 1-27 

1.78 DEVIATION FACTOR 1-28 

1.79 MARKING ABBREVIATIONS FOR MACHINES 1-28 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 
Part 2— TERMINAL MARKINGS 
GENERAL 2-1 

2.1 LOCATION OF TERMINAL MARKINGS 2-1 

2.2 TERMINAL MARKINGS 2-1 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page iv 

2.3 DIRECTION OF ROTATION 2-2 

2.3.1 Alternating-Current Machines 2-2 

2.3.2 Direct-Current Machines 2-2 

2.3.3 Motor-Generator Sets 2-2 

DC MOTORS AND GENERATORS 2-2 

2.10 TERMINAL MARKINGS 2-2 

2.10.1 General 2-2 

2.10.2 Armature Leads 2-2 

2.10.3 Armature Leads— Direction of Rotation 2-2 

2.1 1 TERMINAL MARKINGS FOR DUAL VOLTAGE SHUNT FIELDS 2-2 

2.12 DIRECTION OF ROTATION 2-3 

2.12.1 Direct-Current Motors 2-3 

2.12.2 Direct-Current Generators 2-3 

2.12.3 Reverse Function 2-3 

2.13 CONNECTION DIAGRAMS WITH TERMINAL MARKINGS FOR 
DIRECT-CURRENT MOTORS 2-3 

2.14 CONNECTION DIAGRAMS WITH TERMINAL MARKINGS FOR 
DIRECT-CURRENT GENERATORS 2-7 

AC MOTORS AND GENERATORS 2-9 

2.20 NUMERALS ON TERMINALS OF ALTERNATING-CURRENT 

POLYPHASE MACHINES 2-9 

2.20.1 Synchronous Machines 2-9 

2.20.2 Induction Machines 2-9 

2.21 DEFINITION OF PHASE SEQUENCE 2-9 

2.22 PHASE SEQUENCE 2-9 

2.23 DIRECTION OF ROTATION OF PHASORS 2-9 

2.24 DIRECTION OF ROTATION 2-10 

AC GENERATORS AND SYNCHRONOUS MOTORS 2-10 

2.25 REVERSAL OF ROTATION, POLARITY AND PHASE SEQUENCE 2-10 

2.30 CONNECTION AND TERMINAL MARKINGS— ALTERNATING- 
CURRENT GENERATORS AND SYNCHRONOUS MOTORS- 
THREE-PHASE AND SINGLE-PHASE 2-10 

SINGLE PHASE MOTORS 2-11 

2.40 GENERAL 2-11 

2.40.1 Dual Voltage 2-11 

2.40.2 Single Voltage 2-11 

2.41 TERMINAL MARKINGS IDENTIFIED BY COLOR 2-12 

2.42 AUXILIARY DEVICES WITHIN MOTOR 2-12 

2.43 AUXILIARY DEVICES EXTERNAL TO MOTOR 2-12 

2.44 MARKING OF RIGIDLY MOUNTED TERMINALS 2-12 

2.45 INTERNAL AUXILIARY DEVICES PERMANENTLY CONNECTED 

TO RIGIDLY MOUNTED TERMINALS 2-13 

2.46 GENERAL PRINCIPLES FOR TERMINAL MARKINGS FOR 

SINGLE-PHASE MOTORS 2-13 

2.46.1 First Principle 2-13 

2.46.2 Second Principle 2-13 

2.46.3 Third Principle 2-13 

2.47 SCHEMATIC DIAGRAMS FOR SPLIT-PHASE MOTORS- 
SINGLE VOLTAGE— REVERSIBLE 2-14 

2.47.1 Without Thermal Protector 2-14 

2.47.2 With Thermal Protector 2-14 

2.48 SCHEMATIC DIAGRAMS FOR CAPACITOR-START MOTORS- 
REVERSIBLE 2-15 

2.48.1 Single-Voltage Capacitor-start Motors— Reversible 2-15 

2.48.2 Dual-Voltage Capacitor-start Motors— Reversible 2-16 

2.49 SCHEMATIC DIAGRAMS FOR TWO-VALUE CAPACITOR 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page v 

MOTORS— SINGLE VOLTAGE— REVERSIBLE 2-20 

2.49.1 Without Thermal Protector 2-20 

2.49.2 With Thermal Protector 2-21 

2.50 SCHEMATIC DIAGRAMS FOR PERMANENT-SPLIT CAPACITOR 

MOTORS— SINGLE VOLTAGE— REVERSIBLE 2-22 

2.51 SCHEMATIC DIAGRAMS FOR UNIVERSAL MOTORS- 
SINGLE VOLTAGE 2-23 

2.52 SCHEMATIC DIAGRAMS FOR REPULSION, REPULSION-START 

INDUCTION, AND REPULSION-INDUCTION MOTORS 2-24 

2.53 SHADED-POLE MOTORS— TWO SPEED 2-25 

2.60 GENERAL PRINCIPLES FOR TERMINAL MARKINGS FOR 

POLYPHASE INDUCTION MOTORS 2-25 

2.60.1 Method of Marking 2-25 

2.60.2 Three-Phase, Two Speed Motors 2-27 

2.60.3 Two-Phase Motors 2-27 

2.61 TERMINAL MARKINGS FOR THREE-PHASE SINGLE-SPEED 

INDUCTION MOTORS 2-27 

2.61.1 First 2-27 

2.61.2 Second 2-27 

2.61.3 Third 2-27 

2.61.4 Fourth 2-27 

2.61.5 Fifth 2-27 

2.61.6 Sixth 2-28 

2.62 TERMINAL MARKINGS FOR Y- AND DELTA-CONNECTED 

DUAL VOLTAGE MOTORS 2-28 

2.63 TERMINAL MARKINGS FOR THREE-PHASE TWO-SPEED 

SINGLE-WINDING INDUCTION MOTORS 2-28 

2.64 TERMINAL MARKINGS FOR Y- AND DELTA-CONNECTED 

THREE-PHASE TWO-SPEED SINGLE-WINDING MOTORS 2-28 

2.65 TERMINAL MARKINGS FOR THREE-PHASE INDUCTION 
MOTORS HAVING TWO OR MORE SYNCHRONOUS SPEEDS 

OBTAINED FROM TWO OR MORE INDEPENDENT WINDINGS 2-34 

2.65.1 Each Independent Winding Giving One Speed 2-34 

2.65.2 Each Independent Winding Reconnectible to Give Two 

Synchronous Speeds 2-34 

2.65.3 Two or More Independent Windings at Least One of Which 
Gives One Synchronous Speed and the Other Winding 

Gives Two Synchronous Speeds 2-35 

2.66 TERMINAL MARKINGS OF THE ROTORS OF WOUND-ROTOR 

INDUCTION MOTORS 2-38 

2.67 TERMINAL MARKINGS 2-38 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 
Part 3— HIGH-POTENTIAL TESTS 

3.1 HIGH-POTENTIAL TESTS 3-1 

3.1.1 Safety 3-1 

3.1.2 Definition 3-1 

3.1.3 Procedure 3-1 

3.1.4 Test Voltage 3-1 

3.1.5 Condition of Machine to be Tested 3-1 

3.1.6 Duration of Application of Test Voltage 3-1 

3.1.7 Points of Application of Test Voltage 3-2 

3.1.8 Accessories and Components 3-2 

3.1.9 Evaluation of Dielectric Failure 3-2 

3.1.10 Initial Test at Destination 3-2 

3.1.11 Tests of an Assembled Group of Machines and Apparatus 3-2 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page vi 

3.1.12 Additional Tests Made After Installation 3-3 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 
Part 4— DIMENSIONS, TOLERANCES, AND MOUNTING 

4.1 LETTERING OF DIMENSION SHEETS 4-1 

4.2 SYSTEM FOR DESIGNATING FRAMES 4-10 

4.2.1 Frame Numbers 4-10 

4.2.2 Frame Letters 4-11 

4.3 MOTOR MOUNTING AND TERMINAL HOUSING LOCATION 4-12 

4.4 DIMENSIONS— AC MACHINES 4-14 

4.4.1 Dimensions for Alternating-Current Foot-Mounted 

Machines with Single Straight-Shaft Extension 4-14 

4.4.2 Shaft Extensions and Key Dimensions for Alternating- 
Current Foot-Mounted Machines with Single Tapered or 

Double Straight/Tapered Shaft Extension 4-16 

4.4.3 Shaft Extension Diameters and Key Dimensions for 

Alternating-Current Motors Built in Frames Larger than the 449T Frames 4-17 

4.4.4 Dimensions for Type C Face-Mounting Foot or Footless 

Alternating-Current Motors 4-17 

4.4.5 Dimensions for Type FC Face Mounting for Accessories 

on End of Alternating-Current Motors 4-18 

4.4.6 Dimensions for Type D Flange-Mounting Foot or Footless 
Alternating-Current Motors 4-19 

4.5 DIMENSIONS— DC MACHINES 4-20 

4.5.1 Dimensions for Direct-Current Small Motors with 

Single Straight Shaft Extension 4-20 

4.5.2 Dimensions for Foot-Mounted Industrial Direct-Current Machines 4-21 

4.5.3 Dimensions for Foot-Mounted Industrial Direct-Current Motors 4-25 

4.5.4 Dimensions for Type C Face-Mounting Direct-Current 

Small Motors 4-26 

4.5.5 Dimensions for Type C Face-Mounting Industrial Direct-Current Motors 4-26 

4.5.6 Dimensions for Type C Face-Mounting Industrial Direct-Current Motors 4-27 

4.5.7 Dimensions for Type D Flange-Mounting Industrial Direct-Current Motors 4-27 

4.5.8 Base Dimensions for Type P and PH Vertical Solid-Shaft 

Industrial Direct-Current Motors 4-28 

4.5.9 Dimensions for Type FC Face Mounting for Accessories 

on End Opposite Drive End of Industrial Direct-Current Motors 4-28 

4.6 SHAFT EXTENSION DIAMETERS FOR UNIVERSAL MOTORS 4-28 

4.7 TOLERANCE LIMITS IN DIMENSIONS 4-29 

4.8 KNOCKOUT AND CLEARANCE HOLE DIAMETER FOR MACHINE 

TERMINAL BOXES 4-29 

4.9 TOLERANCES ON SHAFT EXTENSION DIAMETERS AND 

KEYSEATS 4-29 

4.9.1 Shaft Extension Diameter 4-29 

4.9.2 Keyseat Width .'".."'"^..4-29 

4.9.3 Bottom of Keyseat to Shaft Surface 4-29 

4.9.4 Parallelism of Keyseats to Shaft Centerline 4-30 

4.9.5 Lateral Displacement of Keyseats , 4.30 

4.9.6 Diameters and Keyseat Dimensions 4-30 

4.9.7 Shaft Runout 4-30 

4.9.8 Shaft Extension Key(s) 4_31 

4.10 RING GROOVE SHAFT KEYSEATS FOR VERTICAL SHAFT MOTORS 4-32 

4.1 1 METHOD OF MEASUREMENT OF SHAFT RUNOUT AND OF 

ELECTRICITY AND FACE RUNOUT OF MOUNTING SURFACES 4-32 

4.11.1 Shaft Runout 4_32 

4.11.2 Eccentricity and Face Runout of Mounting Surfaces 4-32 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page vii 

4.12 TOLERANCES FOR TYPE C FACE MOUNTING AND TYPE D 

FLANGE MOUNTING MOTORS 4-33 

4.13 TOLERANCES FOR TYPE P FLANGE-MOUNTING MOTORS 4-33 

4.14 MOUNTING BOLTS OR STUDS 4-33 

4.15 METHOD TO CHECK COPLANARITY OF FEET OF FULLY 

ASSEMBLED MOTORS 4-34 

4.16 METHOD OF MEASUREMENT OF SHAFT EXTENSION 

PARALLELISM TO FOOT PLANE 4-34 

4.17 MEASUREMENT OF BEARING TEMPERATURE 4-34 

4.18 TERMINAL CONNECTIONS FOR SMALL MOTORS 4-35 

4.18.1 Terminal Leads 4-35 

4.18.2 Blade Terminals 4-35 

4.19 MOTOR TERMINAL HOUSINGS 4-35 

4.19.1 Small and Medium Motors 4-35 

4.19.2 Dimensions 4-35 

4.20 GROUNDING MEANS FOR FIELD WIRING 4-41 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 6— ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES OF 
PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 

5.1 SCOPE 5-1 

5.2 DESIGNATION 5-1 

5.2.1 Single Characteristic Numeral 5-1 

5.2.2 Supplementary Letters 5-1 

5.2.3 Example of Designation 5-2 

5.2.4 Most Frequently Used 5-2 

5.3 DEGREES OF PROTECTION— FIRST CHARACTERISTIC NUMERAL 5-2 

5.3.1 Indication of Degree of Protection 5-2 

5.3.2 Compliance to Indicated Degree of Protection 5-2 

5.3.3 External Fans 5-2 

5.3.4 Drain Holes 5-3 

Table 5-1 5-3 

5.4 DEGREES OF PROTECTION— SECOND CHARACTERISTIC NUMERAL 5-4 

5.4.1 Indication of Degree of Protection 5-4 

5.4.2 Compliance to Indicated Degree of Protection 5-4 

Table 5-2 5-4 

5.5 MARKING 5-5 

5.6 GENERAL REQUIREMENTS FOR TESTS 5-5 

5.6.1 Adequate Clearance 5-5 

5.7 TESTS FOR FIRST CHARACTERISTIC NUMERAL 5-5 

Table 5-3 5-6 

5.8 TESTS FOR SECOND CHARACTERISTIC NUMERAL 5-7 

5.8.1 Test Conditions 5-7 

Table 5-4 5-8 

5.8.2 Acceptance Conditions 5-10 

5.8.3 Allowable Water Leakage 5-10 

5.9 REQUIREMENTS AND TESTS FOR OPEN WEATHER-PROTECTED MACHINES 5-10 

Figure 5-1 5-11 

Figure 5-2 5-12 

Figure 5-3 5-13 

Figure 5-4 5-14 

Figure 5-5 5-15 

Figure 5-6 5-16 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page viii 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 6— ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 

6.1 SCOPE 6-1 

6.2 DEFINITIONS 6-1 

6.2.1 Cooling 6-1 

6.2.2 Coolant 6-1 

6.2.3 Primary Coolant 6-1 

6.2.4 Secondary Coolant 6-1 

6.2.5 Final Coolant 6-1 

6.2.6 Surrounding Medium 6-1 

6.2.7 Remote Medium 6-2 

6.2.8 Direct Cooled Winding (Inner-cooled Winding) 6-2 

6.2.9 Indirect Cooled Winding 6-2 

6.2.10 Heat Exchange 6-2 

6.2.11 Pipe, Duct 6-2 

6.2.12 Open Circuit 6-2 

6.2.13 Closed Circuit 6-2 

6.2.14 Piped or Ducted Circuit 6-2 

6.2.15 Stand-by or Emergency Cooling System 6-2 

6.2.16 Integral Component 6-2 

6.2.17 Machine-Mounted Component 6-3 

6.2.18 Separate Component 6-3 

6.2.19 Dependent Circulation Component 6-3 

6.2.20 Independent Circulation Component 6-3 

6.3 DESIGNATION SYSTEM 6-3 

6.3.1 Arrangement of the IC Code 6-3 

6.3.2 Application of Designations 6-4 

6.3.3 Designation of Same Circuit Arrangements for Different 

Parts of a Machine 6A 

6.3.4 Designation of Different Circuit Arrangements for Different 

Parts of a Machine 6-4 

6.3.5 Designation of Direct Cooled Winding 6-5 

6.3.6 Designation of Stand-by or Emergency Cooling Conditions 6-5 

6.3.7 Combined Designations 6-5 

6.3.8 Replacement of Characteristic Numerals 6-5 

6.4 CHARACTERISTIC NUMERAL FOR CIRCUIT ARRANGEMENT 6-5 

6.5 CHARACTERISTIC LETTERS FOR COOLANT 6-6 

6.6 CHARACTERISTIC NUMERAL FOR METHOD OF MOVEMENT 6-7 

6.7 COMMONLY USED DESIGNATIONS 6-8 

6.7.1 General Information on the Tables 6-8 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 7— MECHANICAL VIBRATION-MEASUREMENT, EVALUATION AND LIMITS 
(Entire Section Replaced) 

7.1 SCOPE 7-1 

7.2 OBJECT 7-1 

7.3 REFERENCES 7-1 

7.4 MEASUREMENT QUANTITY 7-1 

7.4.1 Bearing Housing Vibration 7-1 

7.4.2 Relative Shaft Vibration 7-1 

7.5 MEASUREMENT EQUIPMENT 7-2 

7.6 MACHINE MOUNTING 7-2 

7.6.1 General 7-2 

7.6.2 Resilient Mounting 7-2 

7.6.3 Rigid Mounting 7-2 

7.6.4 Active Environment Determination 7-3 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page ix 

7.7 CONDITIONS OF MEASUREMENT 7-3 

7.7.1 Shaft Key 7-3 

7.7.2 Measurement Points for Vibration 7-3 

7.7.3 Operating Conditions 7-4 

7.7.4 Vibration Transducer Mounting 7-4 

7.8 LIMITS OF BEARING HOUSING VIBRATION 7-7 

7.8.1 General 7-7 

7.8.2 Vibration Limits for Standard Machines 7-9 

7.8.3 Vibration Limits for Special Machines 7-9 

7.8.4 Vibration Banding for Special Machines 7-9 

7.8.5 Twice Line Frequency Vibration of Two Pole Induction Machines 7-10 

7.8.6 Axial Vibration 7-11 

7.9 LIMITS OF RELATIVE SHAFT VIBRATION 7-11 

7.9.1 General 7-11 

7.9.2 Standard Machines 7-12 

7.9.3 Special Machines 7-12 

Section I GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 9— ROTATING ELECTRICAL MACHINES— SOUND POWER LIMITS 
AND MEASUREMENT PROCEDURES 

9.1 SCOPE 9-1 

9.2 GENERAL 9-1 

9.3 REFERENCES 9-1 

9.4 METHODS OF MEASUREMENT 9-1 

9.5 TEST CONDITIONS 9-2 

9.5.1 Machine Mounting 9-2 

9.5.2 Test Operating Conditions 9-2 

9.6 SOUND POWER LEVEL 9-2 

9.7 DETERMINATION OF SOUND PRESSURE LEVEL 9-3 

Table 9-1 9-4 

Table 9-2 , 9-5 

Table 9-3 9-5 

Table 9-4 9-6 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 10— AC SMALL AND MEDIUM MOTORS 

10.0 SCOPE 10-1 

10.30 VOLTAGES 10-1 

10.31 FREQUENCIES 10-1 

10.31.1 Alternating-Current Motors 10-1 

10.31.2 Universal Motors 10-1 

10.32 HORSEPOWER AND SPEED RATINGS 10-2 

10.32.1 Small Induction Motors, Except Permanent-Split Capacitor 
Motors Rated 1/3 Horsepower and Smaller and Shaded- 

Pole Motors 10-2 

10.32.2 Small induction Motors, permanent-Split Capacitor Motors 

Rated 1/3 Horsepower and Smaller and Shaded-Pole Motors 10-2 

10.32.3 Single-Phase Medium Motors 10-3 

10.32.4 Polyphase Medium Induction Motors 10-3 

10.32.5 Universal Motors 10-4 

10.33 HORSEPOWER RATINGS OF MULTISPEED MOTORS 10-4 

10.33.1 Constant Horsepower 10-4 

10.33.2 Constant Torque 10-5 

10.33.3 Variable Torque 10-5 

10.34 BASIS FOR HORSEPOWER RATING 10-5 

10.34.1 Basis of Rating 10-5 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Pagex 

10.34.2 Temperature 10-5 

10.34.3 Minimum Breakdown Torque 10-5 

10.35 SECONDARY DATA FOR WOUND-ROTOR-MOTORS 10-8 

10.36 TIME RATINGS FOR SINGLE-PHASE AND POLYPHASE 

INDUCTION MOTORS 10-8 

10.37 CODE LETTERS (FOR LOCKED-ROTOR KVA) 10-8 

10.37.1 Nameplate Marking 10-8 

10.37.2 Letter Designation 10-8 

10.37.3 Multispeed Motors 10-8 

10.37.4 Single-Speed Motors 10-9 

10.37.5 Broad- or Dual-Voltage Motors 10-9 

10.37.6 Dual-Frequency Motors 10-9 

10.37.7 Part-Winding-Start Motors 10-9 

10.38 NAMEPLATE TEMPERATURE RATINGS FOR ALTERNATING- 
CURRENT SMALL AND UNIVERSAL MOTORS 10-9 

10.39 NAMEPLATE MARKING FOR ALTERNATING-CURRENT SMALL 

AND UNIVERSAL MOTORS 10-9 

10.39.1 Alternating-Current Single-Phase and Polyphase Squirrel- 
Cage Motors, Except Those Included in 10.39.2, 10.39.3, 

and 10.39.4 10-9 

10.39.2 Motors Rated Less than 1/20 Horsepower 10-10 

10.39.3 Universal Motors 10-10 

10.39.4 Motors Intended for Assembly in a Device Having its 

Own Markings 10-10 

10.39.5 Motors for Dual Voltage 10-10 

1 0.40 NAMEPLATE MARKING FOR MEDIUM SINGLE-PHASE AND 

POLYPHASE INDUCTION MOTORS 10-11 

10.40.1 Medium Single-Phase and Polyphase Squirrel-Cage Motors 10-11 

10.40.2 Polyphase Wound-Rotor Motors 10-12 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 10— DC SMALL AND MEDIUM MOTORS 

10.0 SCOPE 10-13 

10.60 BASIS OF RATING 10-13 

10.60.1 Small Motors 10-13 

10.60.2 Medium Motors 10-13 

10.61 POWER SUPPLY IDENTIFICATION FOR DIRECT-CURRENT 

MEDIUM MOTORS 10-13 

10.60.1 Supplies Designated by a Single Letter 10-13 

10.60.2 Other Supply Types 10-13 

10.62 HORSEPOWER, SPEED, AND VOLTAGE RATINGS 10-14 

10.62.1 Direct-Current Small Motors 10-14 

10.62.2 Industrial Direct-Current Motors 10-15 

10.63 NAMEPLATE TIME RATING 10-15 

1 0.64 TIME RATING FOR INTERMITTENT, PERIODIC, AND VARYING 

DUTY 10-15 

10.65 NAMEPLATE MAXIMUM AMBIENT TEMPERATURE AND 

INSULATION SYSTEM CLASS 10-15 

10.66 NAMEPLATE MARKING 10-17 

10.66.1 Small Motors Rated 1/20 Horsepower and Less 10-17 

10.66.2 Small Motors Except Those Rated 1/20 Horsepower and 

Less 10-18 

10.66.3 Medium Motors 10-18 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xi 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 12— TESTS AND PERFORMANCE— AC AND DC MOTORS 

12.0 SCOPE 12-1 

12.2 HIGH-POTENTIAL TEST— SAFETY PRECAUTIONS 

AND TEST PROCEDURE 12-1 

12.3 HIGH-POTENTIAL TEST VOLTAGES FOR UNIVERSAL, INDUCTION, 

AND DIRECT-CURRENT MOTORS 12-1 

12.4 PRODUCTION HIGH-POTENTIAL TESTING OF SMALL MOTORS 12-2 

12.4.1 Dielectric Test Equipment 12-3 

12.4.2 Evaluation of Insulation Systems by a Dielectric Test 12-3 

12.5 REPETITIVE SURGE TEST FOR SMALL AND MEDIUM MOTORS 12-3 

12.6 MECHANICAL VIBRATION 12-4 

12.7 BEARING LOSSES— VERTICAL PUMP MOTORS 12-4 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 12— TESTS AND PERFORMANCE— AC MOTORS 

12.0 SCOPE 12-5 

12.30 TEST METHODS 12-5 

12.31 PERFORMANCE CHARACTERISTICS 12-5 

12.32 TORQUE CHARACTERISTICS OF SINGLE-PHASE GENERAL- 
PURPOSE INDUCTION MOTORS 12-5 

12.32.1 Breakdown Torque 12-5 

12.32.2 Locked-rotor Torque of Small Motors 12-6 

12.32.3 Locked-rotor Torque of Medium Motors 12-6 

12.32.4 Pull-Up Torque of Medium Motors 12-6 

12.33 LOCKED-ROTOR CURRENT OF SINGLE-PHASE SMALL MOTORS 12-6 

12.33.1 Design O and Design N Motors 12-6 

12.33.2 General-Purpose Motors 12-7 

12.34 LOCKED-ROTOR CURRENT OF SINGLE-PHASE MEDIUM 

MOTORS, DESIGNS L AND M 12-7 

12.35 LOCKED-ROTOR CURRENT OF 3-PHASE 60-HERTZ SMALL AND 
MEDIUM SQUIRREL-CAGE INDUCTION MOTORS RATED AT 

230 VOLTS 12-7 

12.35.1 60-Hertz Design B, C, and D Motors at 230 Volts 12-7 

12.35.2 50-Hertz Design B, C, and D Motors at 380 Volts 12-9 

12.36 INSTANTANEOUS PEAK VALUE OF INRUSH CURRENT 12-9 

12.37 TORQUE CHARACTERISTICS OF POLYPHASE SMALL MOTORS 12-9 

12.38 LOCKED-ROTOR TORQUE OF SINGLE-SPEED POLYPHASE 
SQUIRREL-CAGE MEDIUM MOTORS WITH CONTINUOUS 

RATINGS 12-10 

12.38.1 Design A and B Motors 12-10 

12.38.2 Design C Motors 12-10 

12.38.3 Design D Motors 12-11 

12.39 BREAKDOWN TORQUE OF SINGLE-SPEED POLYPHASE 
SQUIRREL-CAGE MEDIUM MOTORS WITH CONTINUOUS 

RATINGS 12-11 

12.39.1 Design A and B Motors 12-11 

12.39.2 Design C Motors 12-11 

12.40 PULL-UP TORQUE OF SINGLE-SPEED POLYPHASE SQUIRREL- 
CAGE MEDIUM MOTORS WITH CONTINUOUS RATINGS 12-12 

12.40.1 Design A and B Motors 12-12 

12.40.2 Design C Motors 12-13 

12.41 BREAKDOWN TORQUE OF POLYPHASE WOUND-ROTOR MEDIUM 

MOTORS WITH CONTINUOUS RATINGS 12-13 

12.42 TEMPERATURE RISE FOR SMALL AND UNIVERSAL MOTORS 12-14 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
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12.42.1 Alternating-Current Small Motors—Motor Nameplates 
Marked with Insulation System Designation and Ambient 

Temperature 12-14 

12.42.2 Universal Motors 12-15 

12.42.3 Temperature Rise for Ambients Higher than 40°C 12-15 

12.42.4 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C 

but Not Below 0° C 12-16 

12.43 TEMPERATURE RISE FOR MEDIUM SINGLE-PHASE AND 

POLYPHASE INDUCTION MOTORS 12-17 

12.43.1 Temperature Rise for Ambients Higher than 40°C 12-17 

12.43.2 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0° C 12-18 

12.44 VARIATION FROM RATED VOLTAGE AND RATED FREQUENCY 12-19 

12.44.1 Running 12-19 

12.44.2 Starting 12-19 

12.45 VOLTAGE UNBALANCE 12-19 

12.46 VARIATION FROM RATED SPEED 12-19 

12.47 NAMEPLATE AMPERES— ALTERNATING-CURRENT MEDIUM 

MOTORS 12-19 

12.48 OCCASIONAL EXCESS CURRENT 12-19 

12.49 STALL TIME 12-20 

12.50 PERFORMANCE OF MEDIUM MOTORS WITH DUAL VOLTAGE 

RATING (SUGGESTED STANDARD FOR FUTURE DESIGN) 12-20 

12.51 SERVICE FACTOR OF ALTERNATING-CURRENT MOTORS 12-20 

12.51.1 General-Purpose Alternating-Current Motors of the Open Type 12-20 

12.51.2 Other Motors 12-21 

12.52 OVERSPEEDS FOR MOTORS ""!!!!!l2-21 

12.52.1 Squirrel-Cage and Wound-Rotor Motors 12-21 

12.52.2 General-Purpose Squirrel-Cage Induction Motors 12-21 

12.52.3 General-Purpose Design A and B Direct-Coupled Drive Squirrel-Cage 

Induction Motors 12-23 

12.52.4 Alternating-Current Series and Universal Motors 12-23 

12.53 MACHINE SOUND (MEDIUM INDUCTION MOTORS) 12-25 

12.54 NUMBER OF STARTS 12-25 

12.54.1 Normal Starting Conditions 12-25 

12.54.2 Other than Normal Starting Conditions 12-25 

12.54.3 Considerations for Additional Starts 12-25 

12.55 ROUTINE TESTS FOR POLYPHASE MEDIUM INDUCTION MOTORS 12-25 

12.55.1 Method of Testing 12-25 

12.55.2 Typical Tests on Completely Assembled Motors 12-26 

12.55.3 Typical of Tests on Motors Not Completely Assembled 12-26 

12.56 THERMAL PROTECTION OF MEDIUM MOTORS 12-27 

12.56.1 Winding Temperature 12-27 

12.56.2 Trip Current 12-29 

12.57 OVERTEMPERATURE PROTECTION OF MEDIUM MOTORS NOT 

MEETING THE DEFINITION OF 'THERMALLY PROTECTED" 12-29 

12.57.1 Type 1— Winding Running and Locked Rotor Overtemperature 

Protection 12-29 

12.57.2 Type 2 — Winding Running Overtemperature Protection 12-29 

12.57.3 Type 3 — Winding Overtemperature Protection, Nonspecific Type 12-29 

12.58 EFFICIENCY ""! 12-29 

12.58.1 Determination of Motor Efficiency and Losses 12-29 

12.58.2 Efficiency of Polyphase Squirrel-Cage Medium Motors with 

Continuous Ratings 12-30 

12.59 EFFICIENCY LEVELS OF ENERGY EFFICIENT POLYPHASE 

SQUIRREL-CAGE INDUCTION MOTORS 12-31 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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12.60 EFFICIENCY LEVEL OF PREMIUM EFFICIENCY ELECTRIC MOTORS 12-32 

12.60.1 60 Hz Motors Rated 600 Volts or Less (Random Wound) 12-32 

12.60.2 60 Hz Motors Rated Medium Voltage, 5000 Volts or Less (Form Wound) 12-32 

12.60.3 50 Hz Motors Rated 400 Volts or Less (Random Wound) 12-32 

12.61 REPORT OF TEST FOR TESTS ON INDUCTION MOTORS 12-32 

Table 12-11 12-33 

Table 12-12 12-35 

Table 12-13 12-37 

Table 12-14 12-38 

12.62 MACHINE WITH ENCAPSULATED OR SEALED WINDING 

CONFORMANCE TESTS 12-40 

12.63 MACHINE WITH MOISTURE RESISTANT WINDINGS- 
CONFORMANCE TEST 12-40 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 12— TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 

12.0 SCOPE 12-41 

12.65 TEST METHODS 12-41 

12.66 TEST POWER SUPPLY 12-41 

12.66.1 Small Motors 12-41 

12.66.2 Medium Motors 12-41 

12.67 TEMPERATURE RISE 12^3 

12.67.1 Direct-Current Small Motors 12-43 

12.67.2 Continuous-Time-Rated Direct-Current Medium Motors 12-43 

12.67.3 Short-Time-Rated Direct-Current Medium Motors 12-44 

12.67.4 Temperature Rise for Ambients Higher than 40°C 12-44 

12.67.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0° C 12-45 

12.68 VARIATION FROM RATED VOLTAGE 12-46 

12.69 VARIATION IN SPEED DUE TO LOAD 12-46 

12.69.1 Straight-Shunt-Wound, Stabilized-Shunt-Wound, and 

Permanent-Magnet Direct-Current Motors 12-46 

12.69.2 Compound-Wound Direct-Current Motors 12-46 

12.70 VARIATION IN BASE SPEED DUE TO HEATING 12-46 

12.70.1 Speed Variation with Temperature 12-46 

12.70.2 Resistance Variation with Temperature 12-47 

12.71 VARIATION FROM RATED SPEED 12-47 

12.72 MOMENTARY OVERLOAD CAPACITY 12-47 

12.73 SUCCESSFUL COMMUTATION 12-47 

12.74 OVERSPEEDS FOR MOTORS 12-47 

12.74.1 Shunt-Wound Motors 12-47 

12.74.2 Compound-Wound Motors Having Speed Regulation of 

35 Percent or Less 12-47 

12.74.3 Series-Wound Motors and Compound-Wound Motors Having 

Speed Regulation Greater Than 35 Percent 12-47 

12.75 FIELD DATA FOR DIRECT-CURRENT MOTORS 12^8 

12.76 ROUTINE TESTS ON MEDIUM DIRECT-CURRENT MOTORS 12-48 

12.77 REPORT OF TEST FORM FOR DIRECT-CURRENT MACHINES 12-48 

12.78 EFFICIENCY 12-48 

12.78.1 Type A Power Supplies 12-48 

12.78.2 Other Power Supplies 12-49 

12.79 STABILITY 12-49 

12.80 OVER TEMPERATURE PROTECTION OF MEDIUM DIRECT- 
CURRENT MOTORS 12-49 

12.81 DATA FOR DIRECT CURRENT MOTORS 12-50 

12.82 MACHINE SOUND OF DIRECT-CURRENT MEDIUM MOTORS 12-51 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xiv 



Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 13— FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 
INTEGRAL HORSEPOWER INDUCTION MOTORS 

13.0 SCOPE 13-1 

13.1 FRAME DESIGNATIONS FOR SINGLE-PHASE DESIGN L, 
HORIZONTAL, AND VERTICAL MOTORS, 60 HERTZ 
CLASS B INSULATION SYSTEM, OPEN TYPE, 1.15 

SERVICE FACTOR, 230 VOLTS AND LESS 13-1 

13.2 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, 
DESIGNS A, B, AND E, HORIZONTAL AND VERTICAL MOTORS, 
60 HERTZ, CLASS B INSULATION SYSTEM, OPEN TYPE, 1.15 

SERVICE FACTOR, 575 VOLTS AND LESS 13-2 

13.3 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, 
DESIGNS A, B, ND E, HORIZONTAL AND VERTICAL MOTORS, 

60 HERTZ, CLASS B INSULATION SYSTEM, TOTALLY ENCLOSED 

FAN-COOLED TYPE, 1.0 SERVICE FACTOR, 575 VOLTS AND LESS 13-3 

13.4 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, 
DESIGN C, HORIZONTAL AND VERTICAL MOTORS, 60 HERTZ, 
CLASS B INSULATION SYSTEM, OPEN TYPE, 1.15 SERVICE 

FACTOR, 575 VOLTS AND LESS 13-4 

13.5 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, 
DESIGN C, HORIZONTAL AND VERTICAL MOTORS, 60 HERTZ, 
CLASS B INSULATION SYSTEM, TOTALLY ENCLOSED FAN- 
COOLED TYPE, 1.0 SERVICE FACTOR, 575 VOLTS AND LESS 13-5 

SECTION II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL MACHINES) 

Part 14— APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

14.0 SCOPE 14-1 

14.1 PROPER SELECTION OF APPARATUS 14-1 

14.2 USUAL SERVICE CONDITIONS 14-2 

14.2.1 Environmental Conditions 14-2 

14.2.2 Operating Conditions 14-2 

14.3 UNUSUAL SERVICE CONDITIONS 14-2 

14.4 TEMPERATURE RISE 14-3 

14.4.1 Motors with Class A or Class B Insulation Systems 14-3 

14.4.2 Motors with Service Factor 14-3 

14.4.3 Temperature Rise at Sea Level 14-3 

14.4.4 Preferred Values of Altitude for Rating Motors 14-4 

14.5 SHORT-TIME RATED ELECTRICAL MACHINES 14-4 

14.6 DIRECTION OF ROTATION 14-4 

14.7 APPLICATION OF PULLEYS, SHEAVES, SPROCKETS, AND 

GEARS ON MOTOR SHAFTS 14-4 

14.7.1 Mounting 14-4 

14.7.2 Minimum Pitch Diameter for Drives Other than V-Belt 14-4 

14.7.3 Maximum Speed of Drive Components 14-5 

14.8 THROUGH-BOLT MOUNTING 14-5 

14.9 RODENT PROTECTION 14-5 

SECTION II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 14— APPLICATION DATA— AC SMALL AND MEDIUM MOTORS 

14.0 SCOPE 14-7 

14.30 EFFECTS OF VARIATION OF VOLTAGE AND FREQUENCY UPON 

THE PERFORMANCE OF INDUCTION MOTORS 14-7 

14.30.1 General 14-7 

14.30.2 Effects of Variation in Voltage on Temperature 14-7 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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14.30.3 Effect of Variation in Voltage on Power Factor 14-7 

14.30.4 Effect of Variation in Voltage on Starting Torques 14-7 

14.30.5 Effect of Variation in Voltage on Slip 14-7 

14.30.6 Effects of Variation in Frequency 14-8 

14.30.7 Effect of Variations in Both Voltage and Frequency 14-8 

14.30.8 Effect on Special-Purpose or Small Motors 14-8 

14.31 MACHINES OPERATING ON AN UNDERGROUND SYSTEM 14-8 

14.32 OPERATION OF ALTERNATING CURRENT MOTORS FROM 
VARIABLE-FREQUENCY OR VARIABLE-VOLTAGE POWER 

SUPPLIES, OR BOTH 14-8 

14.32.1 Performance 14-8 

14.32.2 Shaft Voltages 14-9 

14.33 EFFECTS OF VOLTAGES OVER 600 VOLTS ON THE PERFORMANCE 

OF LOW-VOLTAGE MOTORS 14-9 

14.34 OPERATION OF GENERAL-PURPOSE ALTERNATING-CURRENT 
POLYPHASE, 2-, 4-, 6-, AND 8-POLE, 60-HERTZ MEDIUM 

INDUCTION MOTORS OPERATED ON 50 HERTZ 14-9 

14.34.1 Speed 14-9 

14.34.2 Torques 14-9 

14.34.3 Locked-Rotor Current 14-10 

14.34.4 Service Factor 14-10 

14.34.5 Temperature Rise 14-10 

14.35 OPERATION OF 230-VOLT INDUCTION MOTORS ON 208-VOLT 

SYSTEMS 14-10 

14.35.1 General 14-10 

14.35.2 Nameplate Marking of Useable® 200 V 14-10 

14.35.3 Effect on Performance of Motor 14-10 

14.36 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE 

OF POLYPHASE INDUCTION MOTORS 14-10 

14.36.1 Effect on Performance — General 14-11 

14.36.2 Unbalance Defined 14-11 

14.36.3 Torques 14-11 

14.36.4 Futl-Load Speed 14-11 

14.36.5 Currents 14-11 

14.37 APPLICATION OF ALTERNATING-CURRENT MOTORS WITH 

SERVICE FACTORS 14-12 

14.37.1 General 14-12 

14.37.2 Temperature Rise— Medium Alternating-Current Motors 14-12 

14.37.3 Temperature Rise— Small Alternating-Current Motors 14-12 

14.38 CHARACTERISTICS OF PART-WINDING-START POLYPHASE 

INDUCTION MOTORS 14-12 

14.39 COUPLING END-PLAY AND ROTOR FLOAT FOR HORIZONTAL 
ALTERNATING-CURRENT MOTORS 14-12 

14.39.1 Preferred Hp Ratings for Motors with Ball Bearings 14-12 

14.39.2 Limits for Motors with Sleeze Bearings 14-13 

14.39.3 Drawing and Shaft Markings 14-13 

14.40 OUTPUT SPEEDS FOR MEDIUM GEAR MOTORS OF PARALLEL 
CONSTRUCTION 14-14 

14.41 APPLICATION OF MEDIUM ALTERNATING-CURRENT SQUIRREL- 
CAGE MACHINES WITH SEALED WINDINGS 14-14 

14.41.1 Usual Service Conditions 14-14 

14.41.2 Unusual Service Conditions 14-14 

14.41.3 Hazardous Locations 14-15 

14.42 APPLICATION OF V-BELT SHEAVES TO ALTERNATING CURRENT MOTORS 

HAVING ANTIFRICTION BEARINGS 14-15 

14.42.1 Dimensions 14-15 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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14.42.2 Radial Overhung Load Limitations 14-15 

14.43 ASEISMATIC CAPABILITY 14-15 

14.44 POWER FACTOR OF THREE-PHASE, SQUIRREL-CAGE, 

MEDIUM MOTORS WITH CONTINUOUS RATINGS 14-17 

14.44.1 Determination of Power Factor from Nameplate Data 14-17 

14.44.2 Determination of Capacitor Rating for Connecting Power 

Factor to Desired Value , 14-17 

14.44.3 Determination of Corrected Power Factor for Specified 

Capacitor Rating 14-18 

14.44.4 Application of Power Factor Correction Capacitors on Power Systems 14-18 

14.44.5 Application of Power Factor Correction Capacitors on Motors 

Operated from Electronic Power Supply 14-18 

14.45 BUS TRANSFER OR RECLOSING 14-18 

14.46 ROTOR INERTIA FOR DYNAMIC BREAKING 14-18 

14.47 EFFECTS OF LOAD ON MOTOR EFFICIENCY 14-18 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 14— APPLICATION DATA— DC SMALL AND MEDIUM MOTORS 

14.0 SCOPE 14-21 

14.60 OPERATION OF SMALL MOTORS ON RECTIFIED ALTERNATING 

CURRENT 14-21 

14.60.1 General 14-21 

14.60.2 Form Factor 14-21 

14.61 OPERATION OF DIRECT-CURRENT MEDIUM MOTORS ON 

RECTIFIED ALTERNATING CURRENT 14-22 

14.62 ARMATURE CURRENT RIPPLE 14-23 

14.63 OPERATION ON A VARIABLE-VOLTAGE POWER SUPPLY 14-23 

14.64 SHUNT FIELD HEATING AT STANDSTILL 14-24 

14.65 BEARING CURRENTS 14-24 

1 4.66 EFFECTS OF 50-HERTZ ALTERNATING-CURRENT POWER 

FREQUENCY 14-24 

14.67 APPLICATION OF OVERHUNG LOADS TO MOTOR SHAFTS 14-25 

14.67.1 Limitations 14-25 

14.67.2 V-Belt Drives '""^^^'''"'""'""!l4-26 

14.67.3 Applications Other Than V-Belts 14-27 

14.67.4 General 14-27 

14.68 RATE OF CHANGE OF ARMATURE CURRENT ^..."!^..^....."l4-28 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 15— DC Generators 

15.0 SCOPE 15^ 

15.10 KILOWATT, SPEED, AND VOLTAGE RATINGS """""Z!!"".!l5-1 

15.10.1 Standard Ratings 15_1 

15.10.2 Exciters 15_2 

15.11 NAMEPLATE TIME RATING, MAXIMUM AMBIENT TEMPERATURE 

AND INSULATION SYSTEM CLASS ' 15.2 

15.12 NAMEPLATE MARKING 15 _ 2 

TESTS AND PERFORMANCE 1 5 _ 2 

15.40 TEST PERFORMANCE 15 _ 2 

15.41 TEMPERATURE RISE !"""!!!l5-2 

15.41.1 Temperature Rise for Maximum Ambient of 40°C 15-2 

15.41 .2 Temperature Rise for Ambients Higher than 40°C 15-3 

15.41.3 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0° C ' 15.3 

15.42 SUCCESSFUL COMMUTATION 15_4 

15.43 OVERLOAD 15.4 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xvii 

15.44 VOLTAGE VARIATION DUE TO HEATING 15-4 

15.45 FLAT COMPOUNDING 15-4 

15.46 TEST FOR REGULATION 15-4 

15.47 OVERSPEEDS FOR GENERATORS 15-5 

15.48 HIGH-POTENTIAL TEST 15-5 

15.48.1 Safety Precautions for Test Procedure 15-5 

15.48.2 Test Voltage 15-5 

15.49 ROUTINE TESTS 15-5 

15.50 FIELD DATA FOR DIRECT-CURRENT GENERATORS 15-5 

15.51 REPORT OF TEST FORM 15-6 

15.52 EFFICIENCY 15-6 

MANUFACTURING 15-7 

15.60 DIRECTION OF ROTATION 15-7 

15.61 EQUALIZER LEADS OF DIRECT-CURRENT GENERATORS 15-7 

Section II SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 
Part 18— DEFINITE PURPOSE MACHINES 

18.1 SCOPE 18-1 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 18-1 

18.2 CLASSIFIED ACCORDING TO ELECTRICAL TYPE 18-2 

RATINGS 18-3 

18.3 VOLTAGE RATINGS 18-3 

18.3.1 Single-Phase Motors 18-3 

18.3.2 Polyphase Induction Motors 18-3 

18.4 FREQUENCIES 18-3 

18.5 SPEED RATINGS 18-3 

TESTS AND PERFORMANCE 18-3 

18.6 OPERATING TEMPERATURE 18-3 

1 8.7 BREAKDOWN TORQUE AND LOCKED-ROTOR CURRENT 

OF 60-HERTZ HERMETIC MOTORS 18-3 

18.7.1 Breakdown Torque 18-3 

18.7.2 Locked-Rotor Current 18-3 

18.8 HIGH-POTENTIAL TEST 18-5 

1 8.9 VARIATIONS FROM RATED VOLTAGE AND RATED 

FREQUENCY 18-5 

18.10 DIRECTION OF ROTATION 18-5 

18.11 TERMINAL LEAD MARKINGS 18-5 

18.12 METHOD TEST FOR CLEANLINESS OF SINGLE-PHASE 
HERMETIC MOTORS HAVING STATOR DIAMETERS OF 6.292 

INCHES AND SMALLER 18-5 

18.12.1 Stators 18-6 

18.12.2 Rotors 18-6 

18.13 METHOD OF TEST FOR CLEANLINESS OF HERMETIC MOTORS 

HAVING STATOR DIAMETERS OF 8.777 INCHES AND SMALLER 18-6 

18.13.1 Purpose 18-6 

18.13.2 Description 18-6 

18.13.3 Sample Storage 18-6 

18.13.4 Equipment 18-6 

18.13.5 Procedure 18-7 

MANUFACTURING 18-7 

18.14 ROTOR BORE DIAMETERS AND KEYWAY DIMENSIONS FOR 

60-HERTZ HERMETIC MOTORS 18-8 

18.15 DIMENSIONS FOR 60-HERTZ HERMETIC MOTORS 18-9 

18.16 FORMING OF END WIRE 18-9 

18.17 THERMAL PROTECTORS ASSEMBLED ON OR IN END 

WINDINGS OF HERMETIC MOTORS 18-9 



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MG 1-2009 
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18.18 LETTERING OF DIMENSIONS FOR HERMETIC MOTORS 

FOR HERMETIC COMPRESSORS 18-10 

SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 18-12 

18.19 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-12 

RATINGS 18-12 

18.20 VOLTAGE RATINGS 18-12 

18.20.1 Single-Phase Motors 18-12 

18.20.2 Polyphase Induction Motors 18-12 

18.21 FREQUENCIES 18-12 

18.22 HORSEPOWER AND SPEED RATINGS 18-12 

18.22.1 Single-Speed Motors 18-12 

18.22.2 Two-Speed Motors 18-12 

TESTS AND PERFORMANCE 18-13 

18.23 TEMPERATURE RISE 18-13 

18.24 BASIS OF HORSEPOWER RATING 18-13 

18.25 MAXIMUM LOCKED-ROTOR CURRENT— SINGLE-PHASE 18-13 

18.26 HIGH-POTENTIAL TESTS 18-13 

18.27 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-13 

18.28 DIRECTION OF ROTATION 18-13 

MANUFACTURING 18-13 

18.29 GENERAL MECHANICAL FEATURES 18-13 

18.30 DIMENSIONS AND LETTERING OF DIMENSIONS FOR MOTORS 

FOR SHAFT-MOUNTED FANS AND BLOWERS 18-13 

18.31 TERMINAL MARKINGS 18-13 

18.32 TERMINAL LEAD LENGTHS 18-14 

SMALL MOTORS FOR BELTED FANS AND BLOWERS BUILT IN 

FRAMES 56 AND SMALLER 18-16 

18.33 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-16 

RATINGS 18-16 

18.34 VOLTAGE RATINGS 18-16 

18.34.1 Single-Phase Motors 18-16 

18.34.2 Polyphase Motors 18-16 

18.35 FREQUENCIES 18-16 

18.36 HORSEPOWER AND SPEED RATINGS 18-16 

18.36.1 Single-Speed Motors 18-16 

18.36.2 Two-Speed Motors 18-16 

TESTS AND PERFORMANCE 18-17 

18.37 TEMPERATURE RISE 18-17 

18.38 BASIS OF HORSEPOWER RATING 18-17 

18.39 MAXIMUM LOCKED-ROTOR CURRENT 18-17 

18.40 HIGH-POTENTIAL TEST 18-17 

18.41 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY . 18-17 

18.42 DIRECTION OF ROTATION 18-17 

MANUFACTURING 18-17 

18.43 GENERAL MECHANICAL FEATURES 18-17 

1 8.44 LETTERING OF DIMENSIONS FOR MOTORS FOR BELTED FANS 

AND BLOWERS 18-18 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND 

EVAPORATOR FANS 18-19 

18.45 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-19 
RATINGS ' 18 . 19 

18.46 VOLTAGE RATINGS 18-19 

18.47 FREQUENCIES 18-19 

18.48 HORSEPOWER AND SPEED RATINGS 18-19 

18.48.1 Horsepower Ratings 18-19 

18.48.2 Speed Ratings ^.'"'.'""!'.""".'l8-19 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
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TESTS AND PERFORMANCE 18-19 

18.49 TEMPERATURE RISE 18-19 

18.50 BASIS OF HORSEPOWER RATINGS 18-19 

18.51 HIGH-POTENTIAL TESTS 18-20 

18.52 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-20 

18.53 VARIATION FROM RATED SPEED 18-20 

18.54 TERMINAL MARKINGS— MULTISPEED SHADED-POLE MOTORS 18-20 
MANUFACTURING 18-20 

18.55 TERMINAL MARKINGS 18-20 

18.56 TERMINAL LEAD LENGTHS 18-21 

18.57 GENERAL MECHANICAL FEATURES 18-21 

1 8.58 TERMINAL MARKINGS FOR NON-POLE-CHANGING MULTISPEED 
SINGLE-VOLTAGE NONREVERSIBLE PERMANENT-SPLIT 

CAPACITOR MOTORS AND SHADED POLE MOTORS 18-22 

1 8.59 DIMENSIONS OF SHADED-POLE AND PERMANENT-SPLIT 
CAPACITOR MOTORS HAVING A P DIMENSION 4.38 INCHES AND 

LARGER 18-24 

1 8.60 DIMENSIONS OF SHADED-POLE AND PERMANENT SPLIT 
CAPACITOR MOTORS HAVING A P DIMENSION SMALLER THAN 

4.38 INCHES 18-25 

1 8.61 DIMENSIONS FOR LUG MOUNTING FOR SHADED-POLE AND 
PERMANENT-SPLIT CAPACITOR MOTORS 18-25 

APPLICATION DATA 18-26 

18.62 NAMEPLATE CURRENT 18-26 

RATINGS 18-26 

1 8.63 EFFECT OF VARIATION FROM RATED VOLTAGE UPON 

OPERATING SPEED 18-26 

18.64 INSULATION TESTING 18-26 

18.64.1 Test Conditions 18-26 

18.64.2 Test Method 18-27 

18.65 SERVICE CONDITIONS 18-27 

SMALL MOTORS AND SUMP PUMPS 18-30 

18.66 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-30 

RATINGS 18-30 

18.67 VOLTAGE RATINGS 18-30 

18.68 FREQUENCIES 18-30 

18.69 HORSEPOWER AND SPEED RATINGS 18-30 

18.69.1 Horsepower Ratings 18-30 

18.69.2 Speed Ratings 18-30 

TESTS AND PERFORMANCE 18-30 

18.70 TEMPERATURE RISE 18-30 

18.71 BASIS OF HORSEPOWER RATINGS 18-30 

18.72 TORQUE CHARACTERISTICS 18-30 

18.73 HIGH-POTENTIAL TESTS 18-31 

1 8.74 VARIATIONS FROM RATED VOLTAGE AND RATED 

FREQUENCY 18-31 

18.75 DIRECTION OF ROTATION 18-31 

MANUFACTURING 18-31 

18.76 GENERAL MECHANICAL FEATURES 18-31 

18.77 DIMENSIONS FOR SUMP PUMP MOTORS, TYPE K 18-31 

18.78 FRAME NUMBER AND FRAME SUFFIX LETTER 18-31 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 18-33 

18.79 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-33 

RATINGS 18-33 

18.80 VOLTAGE RATINGS 18-33 

18.80.1 Single-Phase Motors 18-33 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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18.30.2 Polyphase Induction Motors 18-33 

18.81 FREQUENCIES 18-33 

18.82 HORSEPOWER AND SPEED RATINGS 18-32 

18.82.1 Horsepower Ratings 18-32 

18.82.2 Speed Ratings 18-33 

TESTS AND PERFORMANCE 18-33 

18.83 TEMPERATURE RISE 18-33 

18.84 BASIS OF HORSEPOWER RATINGS 18-34 

18.85 LOCKED-ROTOR TORQUE 18-34 

18.86 LOCKED-ROTOR CURRENT 18-34 

18.87 HIGH-POTENTIAL TEST 18-35 

18.88 VARIATIONS FROM RATED VOLTAGE AND RATED 

FREQUENCY 18-35 

18.89 DIRECTION OF ROTATION 18-35 

MANUFACTURING 18-35 

18.90 GENERAL MECHANICAL FEATURES 18-35 

18.91 FRAME NUMBER AND FRAME SUFFIX LETTER 18-35 

18.92 DIMENSIONS FOR GASOLINE DISPENSING PUMP MOTORS, 

TYPEG 18-36 

SMALL MOTORS FOR OIL BURNERS 18-37 

18.93 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-37 

RATINGS 18-37 

18.94 VOLTAGE RATINGS 18-37 

18.95 FREQUENCIES 18-37 

18.96 HORSEPOWER AND SPEED RATINGS 18-37 

18.96.1 Horsepower Ratings 18-37 

18.96.2 Speed Ratings 18-37 

TESTS AND PERFORMANCE 18-37 

18.97 TEMPERATURE RISE 18-37 

18.98 BASIS OF HORSEPOWER RATING 18-38 

18.99 LOCKED-ROTOR CHARACTERISTICS 18-38 

18.100 HIGH-POTENTIAL TEST 18-38 

18.101 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-38 

18.102 DIRECTION OF ROTATION 18-38 

MANUFACTURING 18-38 

18.103 GENERAL MECHANICAL FEATURES 18-38 

18.104 DIMENSIONS FOR FACE-MOUNTING MOTORS FOR OIL- 
BURNERS, TYPES M AND N 18-39 

18.104.1 Dimensions 18-39 

18.105 TOLERANCES 18-39 

18.106 FRAME NUMBER AND FRAME SUFFIX LETTER 18-39 

18.106.1 Suffix Letter M 18-39 

18.106.2 Suffix Letter N 18-40 

SMALL MOTORS FOR HOME LAUNDRY EQUIPMENT 18-41 

18.107 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-41 

RATINGS 18-41 

18.108 VOLTAGE RATINGS 18-41 

18.109 FREQUENCIES 18-41 

18.110 HORSEPOWER AND SPEED RATINGS 18-41 

18.110.1 Horsepower Ratings 18-41 

18.110.2 Speed Ratings 18-41 

18.111 NAMEPLATE MARKING 18-41 

TESTS AND PERFORMANCE 18-42 

18.112 TEMPERATURE RISE 18.42 

18.113 BASIS OF HORSEPOWER RATING 18-42 

18.1 14 MAXIMUM LOCKED-ROTOR CURRENT 18-42 



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18.115 HIGH-POTENTIAL TEST 18-42 

18.116 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-42 

MANUFACTURING 18-42 

18.117 GENERAL MECHANICAL FEATURES 18-42 

18.118 DIMENSIONS FOR MOTORS FOR HOME LAUNDRY EQUIPMENT 18-43 

MOTORS AND JET PUMPS 18-44 

18.119 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-44 

RATINGS 18-44 

18.120 VOLTAGE RATINGS 18-44 

18.120.1 Single-Phase Motors 18-44 

18.120.2 Polyphase Induction Motors 18-44 

18.121 FREQUENCIES 18-44 

18.122 HORSEPOWER, SPEED, AND SERVICE FACTOR RATINGS 18-44 

TEST AND PERFORMANCE 18-45 

18.123 TEMPERATURE RISE 18-45 

18.124 BASIS OF HORSEPOWER RATING 18-45 

18.125 TORQUE CHARACTERISTICS 18-45 

18.126 MAXIMUM LOCKED-ROTOR CURRENT 18-45 

18.127 HIGH-POTENTIAL TEST 18-45 

18.128 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-45 

18.129 DIRECTION OF ROTATION 18-45 

MANUFACTURING 18-45 

18.130 GENERAL MECHANICAL FEATURES 18-45 

18.131 DIMENSION FOR FACE-MOUNTED MOTORS FOR JET PUMPS 18-46 

18.132 FRAME NUMBER AND FRAME SUFFIX LETTER 18-47 

SMALL MOTORS FOR COOLANT PUMPS 18-48 

18.133 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-48 

RATINGS 18-48 

18.134 VOLTAGE RATINGS 18-48 

18.134.1 Single-Phase Motors 18-48 

18.134.2 Polyphase Induction Motors 18-48 

18.134.3 Direct-current Motors 18-48 

18.135 FREQUENCIES 18-48 

18.136 HORSEPOWER AND SPEED RATINGS 18-49 

TESTS AND PERFORMANCE 18-50 

18.137 TEMPERATURE RISE 18-50 

18.138 BASIS OF HORSEPOWER RATING 18-50 

18.139 TORQUE CHARACTERISTICS 18-50 

18.140 MAXIMUM LOCKED-ROTOR CURRENT 18-50 

18.141 HIGH-POTENTIAL TEST 18-50 

18.142 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-50 

18.143 DIRECTION OF ROTATION 18-50 

MANUFACTURING 18-51 

18.144 GENERAL MECHANICAL FEATURES 18-51 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 4-INCH 18-52 

18.145 CLASSIFICATION TO ELECTRICAL TYPE 18-52 

RATINGS 18-52 

18.146 VOLTAGE RATINGS 18-52 

18.146.1 Single-Phase Motors 18-52 

18.146.2 Polyphase Induction Motors 18-52 

18.147 FREQUENCIES 18-52 

18.148 HORSEPOWER AND SPEED RATINGS 18-52 

18.148.1 Horsepower Ratings 18-52 

18.148.2 Speed Ratings 18-52 

TESTS AND PERFORMANCE 18-53 

18.149 BASIS OF HORSEPOWER RATING 18-53 



i Copyright 2009 by the National Electrical Manufacturers Association. 



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18.150 LOCKED-ROTOR CURRENT 18-53 

18.150.1 Single-Phase Small Motors 18-53 

18.150.2 Single-Phase Medium Motors 18-53 

18.152.3 Three-Phase Medium Motors 18-53 

18.151 HIGH-POTENTIAL TEST 18-53 

18.152 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 18-53 

18.153 VARIATION FROM RATED FREQUENCY 18-53 

18.154 DIRECTION OF ROTATION 18-53 

18.155 THRUST CAPACITY 18-53 

MANUFACTURING 18-53 

18.156 TERMINAL LEAD MARKINGS 18-53 

18.157 GENERAL MECHANICAL FEATURES 18-54 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 6-INCH 18-55 

18.158 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE . 1 8-55 
RATINGS -18-55 

18.159 VOLTAGE RATINGS 18-55 

18.159.1 Single-Phase Motors 18-55 

18.159.2 Polyphase Induction Motors 18-55 

18.160 FREQUENCIES 18-55 

18.161 HORSEPOWER AND SPEED RATINGS 18-55 

18.161.1 Horsepower Ratings 18-55 

TESTS AND PERFORMANCE 18-55 

18.162 BASIS FOR HORSEPOWER RATING 18-55 

18.163 LOCKED-ROTOR CURRENT 18-55 

18.164 HIGH-POTENTIAL TESTS 18-56 

18.165 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 18-56 

18.166 VARIATION FROM RATED FREQUENCY 18-56 

18.167 DIRECTION OF ROTATION 18-56 

18.168 THRUST CAPACITY 18-56 

MANUFACTURING 18-56 

18.169 TERMINAL LEAD MARKINGS 18-56 

18.170 GENERAL-MECHANICAL FEATURES 18-57 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 8-INCH 18-58 

18.171 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-58 

RATINGS 18_ 58 

18.172 VOLTAGE RATINGS 18-58 

18.173 FREQUENCIES 18-58 

18.174 HORSEPOWER AND SPEED RATINGS ^18-58 

18.174.1 Horsepower Ratings 18-58 

18.174.2 Speed Ratings 18-58 

TESTS AND PERFORMANCE 18-58 

18.175 LOCKED-ROTOR CURRENT 18-58 

18.176 HIGH-POTENTIAL TEST 18-58 

18.177 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 18-59 

18.178 VARIATION FROM RATED FREQUENCY 18-59 

18.179 DIRECTION OF ROTATION "l8-59 

18.180 THRUST CAPACITY 18-59 

18.181 GENERAL MECHANICAL FEATURES 18-60 

MEDIUM DC ELEVATOR MOTORS 18-61 

18.182 CLASSIFICATION ACCORDING TO TYPE 18-61 

18.182.1 Class DH 18 -61 

18.182.2 Class DL 18-61 

RATINGS 1M1 

18.183 VOLTAGE RATINGS -\q^-\ 

18.184 HORSEPOWER AND SPEED RATINGS 18-61 

18.184.1 Class DH 18 -61 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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18.184.2 Class DL 18-61 

18.185 BASIS OF RATING 18-62 

18.185.1 Class DH 18-62 

18.185.2 Class DL 18-62 

18.186 NAMEPLATE MARKINGS 18-62 

TESTS AND PERFORMANCE 18-62 

18.187 ACCELERATION AND DECELERATION CAPACITY 18-62 

18.188 VARIATION IN SPEED DUE TO LOAD 18-62 

18.188.1 Class DH 18-62 

18.188.2 Class DL 18-62 

18.189 VARIATION FROM RATED SPEED 18-62 

18.190 VARIATION IN SPEED DUE TO HEATING 18-62 

18.190.1 Open-Loop Control System 18-62 

18.190.2 Closed-Loop Control System 18-63 

18.191 HIGH-POTENTIAL TEST 18-63 

18.192 TEMPERATURE RISE 18-63 

MOTOR-GENERATOR SETS FOR DC ELEVATOR MOTORS 18-64 

RATINGS 18-64 

18.193 BASIS OF RATING 18-64 

18.193.1 Time Rating 18-64 

18.193.2 Relation to Elevator Motor 18-64 

18.194 GENERATOR VOLTAGE RATINGS 18-64 

18.194.1 Value 18-64 

18.194.2 Maximum Value 18-64 

TESTS AND PERFORMANCE 18-64 

18.195 VARIATION IN VOLTAGE DUE TO HEATING 18-64 

18.195.1 Open-Loop Control System 18-64 

18.195.2 Closed-Loop Control System 18-64 

18.196 OVERLOAD 18-64 

18.197 HIGH-POTENTIAL TEST 18-65 

18.198 VARIATION FROM RATED VOLTAGE 18-65 

18.199 VARIATION FROM RATED FREQUENCY 18-65 

18.200 COMBINED VARIATION OF VOLTAGE AND FREQUENCY 18-65 

18.201 TEMPERATURE RISE 18-65 

18.201.1 Induction Motors 18-65 

18.201.2 Direct-Current Adjustable-Voltage Generators 18-65 

MEDIUM AC POLYPHASE ELEVATOR MOTORS 18-66 

18.202 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-66 

18.202.1 AH1 18-65 

18.202.2 AH2 18-66 

18.202.3 AH3 18-66 

RATINGS 18-66 

18.203 BASIS OF RATING— ELEVATOR MOTORS 18-66 

18.204 VOLTAGE RATINGS 18-66 

18.205 FREQUENCY 18-66 

18.206 HORSEPOWER AND SPEED RATINGS 18-67 

TESTS AND PERFORMANCE 18-67 

18.207 LOCKED-ROTOR TORQUE FOR SINGLE-SPEED SQUIRREL- 
CAGE ELEVATOR MOTORS 18-67 

18.208 TIME-TEMPERATURE RATING 18-67 

18.209 HIGH-POTENTIAL TEST 18-67 

18.210 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-67 

MANUFACTURING 18-68 

18.211 NAMEPLATE MARKING 18-68 

MEDIUM AC CRANE MOTORS 18-69 

RATINGS 18-69 



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18.212 VOLTAGE RATINGS 18-69 

18.213 FREQUENCIES 18-69 

18.214 HORSEPOWER AND SPEED RATINGS 18-69 

18.215 SECONDARY DATA FOR WOUND-ROTOR CRANE MOTORS 18-70 

18.216 NAMEPLATE MARKING 18-70 

18.217 FRAME SIZES FOR TWO- AND THREE-PHASE 60-HERTZ 
OPEN AND TOTALLY ENCLOSED WOUND-ROTOR CRANE 

MOTORS HAVING CLASS B INSULATION SYSTEMS 18-71 

TESTS AND PERFORMANCE 18-71 

18.218 TIME RATINGS 18-71 

18.219 TEMPERATURE RISE 18-71 

18.220 BREAKDOWN TORQUE 18-71 

18.220.1 Minimum Value 18-71 

18.221 .2 Maximum Value 18-71 

18.222 HIGH-POTENTIAL TEST 18-71 

18.223 OVERSPEEDS 18-72 

18.224 PLUGGING 18-72 

18.225 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-72 

18.226 ROUTINE TESTS 18-72 

18.227 BALANCE OF MOTORS 18-72 

18.228 BEARINGS 18-72 

18.229 DIMENSIONS FOR ALTERNATING-CURRENT WOUND-ROTOR 

OPEN AND TOTALLY ENCLOSED CRANE MOTORS 18-73 

18.230 DIMENSIONS AND TOLERANCES FOR ALTERNATING- 
CURRENT OPEN AND TOTALLY ENCLOSED WOUND-ROTOR 

CRANE MOTORS HAVING ANTIFRICTION BEARINGS 18-74 

MEDIUM SHELL-TYPE MOTORS FOR WOODWORKING AND 

MACHINE-TOOL APPLICATIONS 18-76 

18.231 DEFINITION OF SHELL-TYPE MOTOR 18-76 

18.232 TEMPERATURE RISE— SHELL-TYPE MOTOR 18-76 

18.233 TEMPERATURE RISE FOR 60-HERTZ SHELL-TYPE MOTORS 

OPERATED ON 50-HERTZ 18-76 

18.234 OPERATION AT OTHER FREQUENCIES— SHELL-TYPE MOTORS 18-76 

18.235 RATINGS AND DIMENSIONS FOR SHELL-TYPE MOTORS 18-76 

18.235.1 Rotor Bore and Keyway Dimensions, Three-Phase 

60-Hertz 40°C Open Motors, 208, 220, 440, and 550 Volts 18-76 

18.235.2 BH and BJ Dimensions in Inches, Open Type Three-Phase 

60-Hertz 40°C Continuous, 208, 220, 440, and 550 Volts 18-77 

18.236 LETTERING FOR DIMENSION SHEETS FOR SHELL-TYPE MOTORS 18-78 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR 

VERTICAL TURBINE PUMP APPLICATIONS 18-78 

18.237 DIMENSION FOR TYPE VP VERTICAL SOLID-SHAFT, SINGLE-PHASE 
AND POLYPHASE, DIRECT CONNECTED SQUIRREL-CAGE 
INDUCTION MOTORS FOR VERTICAL TURBINE PUMP 

APPLICATIONS 18-79 

1 8.238 DIMENSIONS FOR TYPE P AND PH ALTERNATING-CURRENT 
SQUIRREL-CAGE VERTICAL HOLLOW-SHAFT MOTORS FOR 

VERTICAL TURBINE PUMP APPLICATIONS 18-81 

18.238.1 Base Dimensions 18-81 

18.238.2 Coupling Dimensions 18-82 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR 

CLOSE-COUPLED PUMPS 18-83 

RATINGS ""l8-83 

18.239 VOLTAGE RATINGS 18-83 

18.240 FREQUENCIES 18-83 

18.241 NAMEPLATE MARKINGS 18-83 



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18.242 NAMEPLATE RATINGS 18-83 

TESTS AND PERFORMANCE 18-83 

18.243 TEMPERATURE RISE 18-83 

18.244 TORQUES 18-83 

18.245 LOCKED-ROTOR CURRENTS 18-83 

18.246 HIGH-POTENTIAL TEST 18-83 

18.247 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-83 

18.248 BALANCE OF MOTORS 18-83 

MANUFACTURING 18-83 

18.249 FRAME ASSIGNMENTS 18-83 

18.250 DIMENSIONS FOR TYPE JM AND JP ALTERNATING-CURRENT 
FACE-MOUNTING CLOSE-COUPLED PUMP MOTORS HAVING 

ANTIFRICTION BEARINGS 18-84 

18.251 DIMENSIONS FOR TYPE LP AND LPH VERTICAL SOLID-SHAFT 
SINGLE-PHASE AND POLYPHASE DIRECT-CONNECTED SQUIRREL- 
CAGE INDUCTION MOTORS (HAVING THE THRUST BEARING IN THE 

MOTOR) FOR CHEMICAL PROCESS IN-LINE PUMP APPLICATIONS 18-89 

18.252 DIMENSIONS FOR TYPE HP AND HPH VERTICAL SOLID-SHAFT 
SINGLE-PHASE AND POLYPHASE DIRECT-CONNECTED 
SQUIRREL-CAGE INDUCTION MOTORS FOR PROCESS AND 

IN-LINE PUMP APPLICATIONS 18-91 

DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 18-93 

18.253 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-93 

18.254 CLASSIFICATION ACCORDING TO OUTPUT VOLTAGE RATING 18-93 

RATINGS 18-93 

18.255 OUTPUT VOLTAGE RATINGS 18-93 

18.256 CURRENT RATING 18-93 

18.257 SPEED RATINGS 18-93 

TESTS AND PERFORMANCE 18-93 

18.258 TEST METHODS 18-93 

18.259 TEMPERATURE RISE 18-93 

18.260 VARIATION FROM RATED OUTPUT VOLTAGE 18-94 

18.260.1 High-Voltage Type 18-94 

18.260.2 Low-Voltage Type 18-94 

18.261 HIGH-POTENTIAL TESTS 18-94 

18.261.1 Test 18-94 

18.261.2 Application 18-94 

18.262 OVERSPEED 18-94 

18.263 PERFORMANCE CHARACTERISTICS 18-94 

18.263.1 High-Voltage Type 18-94 

18.263.2 Low-Voltage Type 18-95 

MANUFACTURING 18-95 

18.264 NAMEPLATE MARKING 18-95 

18.264.1 High-Voltage Type 18-95 

18.264.2 Low-Voltage Type 18-95 

18.265 DIRECTION OF ROTATION 18-95 

18.266 GENERAL MECHANICAL FEATURES 18-95 

18.266.1 High-Voltage Type 18-96 

18.266.2 Low-Voltage Type 18-96 

18.267 TERMINAL MARKINGS 18-96 

TORQUE MOTORS 18-97 

18.268 DEFINITION 18-97 

18.269 NAMEPLATE MARKINGS 18-97 

18.269.1 AC Torque Motors 18-97 

18.269.2 DC Torque Motors 18-97 

SMALL MOTORS FOR CARBONATOR PUMPS 18-98 



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18.270 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 18-98 

RATINGS 18-98 

18.271 VOLTAGE RATINGS 18-98 

18.272 FREQUENCIES 18-98 

18.273 HORSEPOWER AND SPEED RATING 18-98 

18.273.1 Horsepower Ratings 18-98 

18.273.2 Speed Ratings 18-98 

TESTS AND PERFORMANCE 18-98 

18.274 TEMPERATURE RISE 18-98 

18.275 BASIS OF HORSEPOWER RATING 18-98 

18.276 HIGH-POTENTIAL TEST 18-98 

18.277 MAXIMUM LOCKED-ROTOR CURRENT— SINGLE PHASE 18-98 

18.278 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 18-98 

18.279 DIRECTION OF ROTATION 18-98 

MANUFACTURING 18-99 

18.280 GENERAL MECHANICAL FEATURE 18-99 

18.281 DIMENSIONS FOR CARBONATOR PUMP MOTORS 18-99 

Section III LARGE MACHINES 

Part 20— LARGE MACHINES— INDUCTION MACHINES 

20.1 SCOPE 20-1 

20.2 BASIS OF RATING 20-1 

20.3 MACHINE POWER AND SPEED RATINGS 20-1 

20.4 POWER RATINGS OF MULTISPEED MACHINES 20-2 

20.4.1 Constant Power 20-2 

20.4.2 Constant Torque 20-2 

20.4.3 Variable Torque 20-2 

20.5 VOLTAGE RATINGS 20-3 

20.6 FREQUENCIES 20-3 

20.7 SERVICE FACTOR 20-3 

20.7.1 Service Factor of 1.0 20-3 

20.7.2 Service Factor of 1.15 20-3 

20.7.3 Application of Motors with a Service Factor of 1.15 20-3 

TESTS AND PERFORMANCE 20-4 

20.8 TEMPERATURE RISE 20-4 

20.8.1 Machines with a 1.0 Service Factor at Rated Load 20-4 

20.8.2 Machines with a 1.15 Service Factor at Service Factor Load 20-5 

20.8.3 Temperature Rise for Ambients Higher than 40°C 20-5 

20.8.4 Temperature Rise for Altitudes Greater than 3300 Feet 

(1000 Meters) 20-5 

20.8.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40°C, 

but Not Below 0°C 20-5 

20.9 CODE LETTERS (FOR LOCKED-ROTOR KVA) 20-6 

20.10 TORQUE 20-7 

20.10.1 Standard Torque 20-7 

20.10.2 High Torque 20-8 

20.10.3 Motor Torques When Customer Specifies A Custom Load Curve 20-8 

20.10.4 Motor With 4.5 pu and Lower Locked-Rotor Current 20-8 

20.1 1 LOAD WK 2 FOR POLYPHASE SQUIRREL-CASE INDUCTION 

MOTORS 20-8 

20.12 NUMBER OF STARTS 20-9 

20.12.1 Starting Capability 20-9 

20.12.2 Additional Starts 20-9 

20.12.3 Information Plate 20-9 

20.13 OVERSPEEDS 20-9 

20.14 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 20-11 



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20.14.1 Running 20-11 

20.14.2 Starting 20-11 

20.15 OPERATION OF INDUCTION MACHINES FROM VARIABLE- 
FREQUENCY OR VARIABLE-VOLTAGE POWER SUPPLIES, 

OR BOTH 20-11 

20.16 TESTS 20-12 

20.16.1 Test Methods 20-12 

20.16.2 Routine Tests on Machines Completely Assembled in Factory 20-12 

20.16.3 Routine Tests on Machines Not Completely Assembled in Factory 20-12 

20.17 HIGH-POTENTIAL TESTS 20-12 

20.17.1 Safety Precautions and Test Procedure 20-12 

20.17.2 Test Voltage— Primary Windings 20-12 

20.17.3 Test Voltage— Secondary Windings of Wound Rotors 20-12 

20.18 MACHINE WITH SEALED WINDINGS— CONFORMANCE TESTS 20-13 

20.18.1 Test for Stator Which Can be Submerged 20-13 

20.18.2 Test for Stator Which Cannot be Submerged 20-13 

20.19 MACHINE SOUND 20-13 

20.20 REPORT OF TEST FORM FOR INDUCTION MACHINES 20-14 

20.21 EFFICIENCY 20-14 

20.22 MECHANICAL VIBRATION 20-14 

20.23 REED FREQUENCY OF VERTICAL MACHINES 20-15 

20.24 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE 

OF POLYPHASE SQUIRREL-CAGE INDUCTION MOTORS 20-15 

20.24.1 Effect on Performance— General 20-16 

20.24.2 Voltage Unbalance Defined 20-16 

20.24.3 Torques 20-16 

20.24.4 Full-Load Speed 20-16 

20.24.5 Currents 20-16 

MANUFACTURING 20-16 

20.25 NAMEPLATE MARKING 20-16 

20.25.1 Alternating-Current Polyphase Squirrel-Cage Motors 20-17 

20.25.2 Polyphase Wound-Rotor Motors 20-17 

20.25.3 Polyphase Squirrel-Cage Generators 20-17 

20.25.4 Polyphase Wound-Rotor Generators 20-18 

20.26 MOTOR TERMINAL HOUSINGS AND BOXES 20-18 

20.26.1 Box Dimensions 20-18 

20.26.2 Accessory Lead Terminations 20-18 

20.26.3 Lead Terminations of Accessories Operating at 50 Volts 

or Less 20-18 

20.27 EMBEDDED TEMPERATURE DETECTORS 20-19 

APPLICATION DATA 20-21 

20.28 SERVICE CONDITIONS 20-21 

20.28.1 General 20-21 

20.28.2 Usual Service Conditions 20-21 

20.28.3 Unusual Service Conditions 20-21 

20.29 END PLAY AND ROTOR FLOAT FOR COUPLED SLEEVE BEARING 

HORIZONTAL INDUCTION MACHINES 20-22 

20.29.1 General 20-22 

20.29.2 Limits 20-22 

20.29.3 Marking Requirements 20-22 

20.30 PULSATING STATOR CURRENT IN INDUCTION MOTORS 20-23 

20.31 ASEISMATIC CAPABILITY 20-23 

20.31.1 General 20-23 

20.31.2 Frequency Response Spectrum 20-23 

20.31.3 Units for Capability Requirements 20-23 

20.31.4 Recommended Peak Acceleration Limits 20-23 



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20.32 BELT, CHAIN, AND GEAR DRIVE 20-24 

20.33 BUS TRANSFER OR RECLOSING 20-24 

20.33.1 Slow Transfer or Reclosing 20-24 

20.33.2 Fast Transfer or Reclosing 20-24 

20.34 POWER FACTOR CORRECTION 20-25 

20.35 SURGE CAPABILITIES OF AC WINDINGS WITH FORM- 
WOUND COILS 20-25 

20.35.1 General 20-25 

20.35.2 Surge Sources 20-25 

20.35.3 Factors Influencing Magnitude and Rise Time 20-25 

20.35.4 Surge Protection 20-26 

20.35.5 Surge Withstand Capability for Standard Machines 20-26 

20.35.6 Special Surge Withstand Capability 20-26 

20.35.7 Testing 20-26 

20.35.8 Test Voltage Values 20-26 

20.36 MACHINES OPERATING ON AN UNGROUNDED SYSTEM 20-26 

20.37 OCCASIONAL EXCESS CURRENT 20-27 

Section III LARGE MACHINES 

Part 21— LARGE MACHINES— SYNCHRONOUS MOTORS 

RATINGS 21-1 

21.1 SCOPE 21-1 

21.2 BASIS OF RATING 21-1 

21.3 HORSEPOWER AND SPEED RATINGS 21-2 

21.4 POWER FACTOR 21-2 

21.5 VOLTAGE RATINGS 21-2 

21.5.1 Voltage Ratings 21-2 

21.5.2 Preferred Motor OutputA/oltage Rating 21-3 

21.6 FREQUENCIES 21-3 

21.7 EXCITATION VOLTAGE 21-3 

21.8 SERVICE FACTOR 21-3 

21.8.1 Service Factor of 1.0 21-3 

21.8.2 Service Factor of 1.15 21-3 

21.8.3 Application of Motor with 1.15 Service Factor 21-3 

21 .9 TYPICAL KW RATINGS OF EXCITERS FOR 60-HERTZ 

SYNCHRONOUS MOTORS 21-4 

TESTS AND PERFORMANCE 21-9 

21.10 TEMPERATURE RISE— SYNCHRONOUS MOTORS 21-9 

21.10.1 Machines with 1.0 Service Factor at Rated Load 21-9 

21 .10.2 Machines with 1.15 Service Factor at Service Factor Load 21-9 

21.10.3 Temperature Rise for Ambients Higher than 40°C 21-10 

21.10.4 Temperature Rise for Altitudes Greater than 3300 Feet (1000 Meters) 21-10 

21 .1 0.5 Temperature Rise for Air-Cooled Motors for Ambients Lower than 40°C, 

but Not Below 0°C 21-10 

21.11 TORQUES 21-11 

21.11.1 General ....21-11 

21.11.2 Motor Torques When Customer Supplies Load Curve 21-11 

21.12 NORMAL WK 2 OF LOAD 21-11 

21.13 NUMBER OF STARTS 21-12 

21.13.1 Starting Capability 21-12 

21.13.2 Additional Starts 21-12 

21.13.3 Information Plate 21-12 

21.14 EFFICIENCY 21-12 

2115 OVERSPEED 21-13 

21.16 OPERATION AT OTHER THAN RATED POWER FACTORS 21-13 

21.16.1 Operation of an 0.8 Power-factor Motor at 1.0 Power-factor 21-13 



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21.16.2 Operation of a 1.0 Power-factor Motor at 0.8 Power-factor 21-14 

2117 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 21-14 

21.17.1 Running 21-14 

21.17.2 Starting 21-14 

21.18 OPERATION OF SYNCHRONOUS MOTORS FROM VARIABLE- 
FREQUENCY POWER SUPPLIES 21-14 

21.19 SPECIFICATION FORM FOR SLIP-RING SYNCHRONOUS MOTORS 21-18 

21.20 SPECIFICATION FORM FOR BRUSHLESS SYNCHRONOUS MOTORS 21-19 

21.21 ROUTINE TESTS 21-20 

21.21.1 Motors Not Completely Assembled in the Factory 21-20 

21.21.2 Motors Completely Assembled in the Factory 21-20 

21.22 HIGH-POTENTIAL TESTS 21-20 

21.22.1 Safety Precautions and Test Procedure 21-20 

21.22.2 Test Voltage— Armature Windings 21-20 

21.22.3 Test Voltage— Field Windings, Motors with Slip Rings 21-20 

21 .22.4 Test Voltage — Assembled Brushless Motor Field 

Windings and Exciter Armature Winding 21-20 

21.22.5 Test Voltage— Brushless Exciter Field Winding 21-21 

21.23 MACHINE SOUND 21-21 

21.24 MECHANICAL VIBRATION 21-21 

MANUFACTURING 21-21 

21.25 NAMEPLATE MARKING 21-21 

21.26 MOTOR TERMINAL HOUSINGS AND BOXES 21-22 

21.26.1 Box Dimensions 21-22 

21.26.2 Accessory Lead Terminations 21-22 

21 .26.3 Lead Terminations of Accessories Operating at 50 Volts or Less 21-22 

21.27 EMBEDDED DETECTORS 21-24 

APPLICATION DATA 21-25 

21.28 SERVICE CONDITIONS 21-25 

21.28.1 General 21-25 

21.28.2 Usual Service Conditions 21-25 

21.28.3 Unusual Service Conditions 21-25 

21 .29 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE 

OF POLYPHASE SYNCHRONOUS MOTORS 21-26 

21.29.1 Effect on Performance 21-27 

21 .29.2 Voltage Unbalanced Defined 21-27 

21 .30 COUPLING END PLAY AND ROTOR FLOAT FOR HORIZONTAL 

MOTORS 21-27 

21.31 BELT, CHAIN, AND GEAR DRIVE 21-27 

21.32 PULSATING ARMATURE CURRENT 21-27 

21.33 TORQUE PULSATIONS DURING STARTING OF SYNCHRONOUS 

MOTORS 21-28 

21.34 BUS TRANSFER OR RECLOSING 21-28 

21.34.1 Slow Transfer of Reclosing 21-28 

21.34.2 Fast Transfer of Reclosing 21-28 

21.34.3 Bus Transfer Procedure 21-29 

21 .35 CALCULATION OF NATURAL FREQUENCY OF SYNCHRONOUS 
MACHINES DIRECT-CONNECTED TO RECIPROCATING 

MACHINERY 21-29 

21.35.1 Undamped Natural Frequency 21-29 

21.35.2 Synchronizing Torque Coefficient, P r 21-29 

21.35.3 Factors Influencing P r 21-29 

21.36 TYPICAL TORQUE REQUIREMENTS 21-29 

21.37 COMPRESSOR FACTORS 21-34 

21.38 SURGE CAPABILITIES OF AC WINDINGS WITH FORM-WOUND COILS 21-35 

21.39 MACHINES OPERATING ON AN UNGROUNDED SYSTEM 21-35 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxx 

21.40 OCCASIONAL EXCESS CURRENT 21-35 

Section III LARGE MACHINES 

Part 23— LARGE MACHINES— DC MOTORS LARGER THAN 1 .25 HORSEPOWER PER RPM, 

OPEN TYPE 
CLASSIFICATION 23-1 

23.1 SCOPE 23-1 

23.2 GENERAL INDUSTRIAL MOTORS 23-1 

23.3 METAL ROLLING MILL MOTORS 23-1 

23.3.1 Class N Metal Rolling Mill Motors 23-1 

23.3.2 Class S Metal Rolling Mill Motors 23-1 

23.4 REVERSING HOT MILL MOTORS 23-1 

RATINGS 23-2 

23.5 BASIS OF RATING 23-2 

23.6 HORSEPOWER, SPEED, AND VOLTAGE RATINGS 23-3 

23.6.1 General Industrial Motors and Metal Rolling Mill Motors, 

Classes N and S 23-3 

23.6.2 Reversing Hot Mill Motors 23-4 

23.7 SPEED RATINGS BY FIELD CONTROL FOR 250-VOLT DIRECT- 
CURRENT MOTORS 23-5 

23.8 SPEED RATINGS BY FIELD CONTROL FOR 500- OR 700-VOLT 
DIRECT-CURRENT MOTORS 23-6 

TESTS AND PERFORMANCE 23-8 

23.9 TEMPERATURE RISE 23-8 

23.9.1 Temperature Rise for Ambients Higher than 40°C 23-9 

23.9.2 Temperature Rise for Altitudes Greater than 3300 Feet 

(1000 Meters) 23-9 

23.9.3 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0° C 23-9 

23.10 OVERLOAD CAPABILITY 23-10 

23.10.1 General Industrial Motors 23-10 

23.10.2 Metal Rolling Mill Motors (Excluding Reversing Hot Mill 
Motors)— Open, Forced-Ventilated, and Totally Enclosed Water- 
Air-Cooled 23-10 

23.10.3 Reversing Hot Mill Motors— Forced-Ventilated and Totally 

Enclosed Water-Air-Cooled 23-11 

23.11 MOMENTARY LOAD CAPACITY 23-11 

23.12 SUCCESSFUL COMMUTATION 23-11 

23.13 EFFICIENCY 23-11 

23.14 TYPICAL REVERSAL TIME OF REVERSING HOT MILL MOTORS 23-12 

23.15 IMPACT SPEED DROP OF A DIRECT-CURRENT MOTOR 23-12 

23.16 OVERSPEED 23-12 

23.17 VARIATION FROM RATED VOLTAGE 23-13 

23.17.1 Steady State 23-13 

23.17.2 Transient Voltages of Microsecond Duration 23-13 

23.18 FIELD DATA FOR DIRECT-CURRENT MOTORS 23-13 

23.19 ROUTINE TESTS 23-14 

23.20 HIGH-POTENTIAL TEST 23-14 

23.20.1 Safety Precautions and Test Procedure 23-14 

23.20.2 Test Voltage 23-14 

23.21 MECHANICAL VIBRATION 23-14 

23.22 METHOD OF MEASURING THE MOTOR VIBRATION 23-14 

23.23 CONDITIONS OF TEST FOR SPEED REGULATION 23-14 

MANUFACTURING 23-14 

23.24 NAMEPLATE MARKING 23-14 

APPLICATION DATA 23-15 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxi 

23.25 SERVICE CONDITIONS 23-15 

23.25.1 General , 23-15 

23.25.2 Usual Service Conditions 23-15 

23.25.3 Unusual Service Conditions 23-15 

23.26 OPERATION OF DIRECT-CURRENT MOTORS ON RECTIFIED 

ALTERNATING CURRENT 23-16 

23.26.1 General 23-16 

23.26.2 Operation on Parallel with Power Supply with High Ripple 23-16 

23.26.3 Bearing Currents 23-17 

23.27 OPERATION OF DIRECT-CURRENT MOTORS BELOW BASE SPEED 

BY REDUCED ARMATURE VOLTAGE 23-17 

23.28 RATE OF CHANGE OF LOAD CURRENT 23-17 

Section III LARGE MACHINES 

Part 24— LARGE MACHINES— DC GENERATORS LARGER THAN 1.0 KILOWATT 
PER RPM, OPEN TYPE CLASSIFICATION 

24.0 SCOPE 24-1 

24.1 GENERAL INDUSTRIAL GENERATORS 24-1 

24.2 METAL ROLLING MILL GENERATORS 24-1 

24.3 REVERSING HOT MILL GENERATORS 24-1 

RATINGS 24-1 

24.9 BASIS OF RATING 24-1 

24.10 KILOWATT, SPEED, AND VOLTAGE RATINGS 24-2 

TESTS AND PERFORMANCE 24-3 

24.40 TEMPERATURE RISE 24-3 

24.40.1 Temperature Rise for Ambients Higher than 40°C 24-4 

24.40.2 Temperature Rise for Altitudes Greater than 3300 Feet 

(1000 Meters) 24-4 

24.40.3 Temperature Rise for Air-Cooled Machines for Ambients Lower 

than 40° C, but Not Below 0° C* 24-4 

24.41 OVERLOAD CAPABILITY 24-5 

24.41.1 General Industrial Generators 24-5 

24.41.2 Metal Rolling Mill Generators (Excluding Reversing Hot Mill 
Generators)— Open, Forced-Ventilated, and Totally Enclosed 
Water-Air-Cooled 24-5 

24.41.3 Reversing Hot Mill Generators— Forced-Ventilated and Totally 

Enclosed Water-Air-Cooled 24-5 

24.42 MOMENTARY LOAD CAPACITY 24-5 

24.43 SUCCESSFUL COMMUTATION 24-6 

24.44 OUTPUT AT REDUCED VOLTAGE 24-6 

24.45 EFFICIENCY 24-6 

24.46 OVERSPEED 24-7 

24.47 FIELD DATA FOR DIRECT-CURRENT GENERATORS 24-7 

24.48 ROUTINE TESTS 24-7 

24.49 HIGH POTENTIAL TESTS 24-7 

24.49.1 Safety Precautions and Test Procedure 24-7 

24.49.2 Test Voltage 24-8 

24.50 CONDITIONS OF TESTS FOR VOLTAGE REGULATION 24-8 

24.51 MECHANICAL VIBRATION 24-8 

MANUFACTURING 24-8 

24.61 NAMEPLATE MARKING 24-8 

APPLICATION DATA 24-8 

24.80 SERVICE CONDITIONS 24-8 

24.80.1 General 24-8 

24.80.2 Usual Service Conditions 24-9 

24.80.3 Unusual Service Conditions 24-9 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxii 

24.81 RATE OF CHANGE OF LOAD CURRENT 24-9 

24 82 SUCCESSFUL PARALLEL OPERATION OF GENERATORS 24-10 

24.83 OPERATION OF DIRECT-CURRENT GENERATORS IN PARALLEL 

WITH RECTIFIED ALTERNATING-VOLTAGE POWER SUPPLY 24-10 

24.83.1 General 24-10 

24.83.2 Operation in Parallel with Power Supply with Ripple 24-10 

24.83.3 Bearing Currents 24-10 

24.84 COMPOUNDING 24-11 

24.84.1 Flat Compounding 24-11 

24.84.2 Other 24-11 

Section IV PERFORMANCE STANDARDS APPLYING TO ALL MACHINES 

Part 30— APPLICATION CONSIDERATIONS FOR CONSTANT SPEED MOTORS 
USED ON A SINUSOIDAL BUS WITH HARMONIC CONTENT AND 
GENERAL PURPOSE MOTORS USED WITH ADJUSTABLE-VOLTAGE 
OR ADJUSTABLE-FREQUENCY CONTROLS OR BOTH 

30.0 SCOPE 30-1 

30.1 APPLICATION CONSIDERATIONS FOR CONSTANT SPEED MOTORS 

USED ON A SINUSOIDAL BUS WITH HARMONIC CONTENT 30-1 

30.1.1 Efficiency 30-1 

30.1.2 Derating for Harmonic Content 30-1 

30.1.3 Power Factor Correction 30-2 

30.2 GENERAL PURPOSE MOTORS USED WITH ADJUSTABLE- 
VOLTAGE OR ADJUSTABLE-FREQUENCY CONTROLS OR BOTH 30-2 

30.2.1 Definitions 30-2 

30.2.2 Application Considerations 30-5 

Section IV PERFORMANCE STANDARDS APPLYING TO ALL MACHINES 
Part 31— DEFINITE-PURPOSE INVERTER-FED POLYPHASE MOTORS 

31.0 SCOPE 31-1 

31.1 SERVICE CONDITIONS 31-1 

31.1.1 General 31-1 

31.1.2 Usual Service Conditions 31-1 

31.1.3 Unusual Service Conditions 31-1 

31.1.4 Operation in Hazardous (Classified) Locations 31-2 

31 .2 DIMENSIONS, TOLERANCES, AND MOUNTING FOR 

FRAME DESIGNATIONS 31-2 

31.3 RATING 31-3 

31.3.1 Basis of Rating 31-3 

31.3.2 Base Horsepower and Speed Ratings 31-3 

31.3.3 Speed Range 31-4 

31.3.4 Voltage 31-4 

31 .3.5 Number of Phases 31-4 

31.3.6 Direction of Rotation 31-5 

31.3.7 Service Factor 31-5 

31.3.8 Duty 31-5 

31.4 PERFORMANCE 31-5 

31.4.1 Temperature Rise 31-5 

31 .4.2 Torque 31-9 

31.4.3 Operating Limitations 31-9 

31.4.4 Insulation Considerations 31-10 

31.4.5 Resonances, Sound, Vibration 31-12 

31.4.6 Bearing Lubrication at Low and High Speeds 31-12 

31.5 NAMEPLATE MARKING 31-13 

31.5.1 Variable Torque Applications 31-13 

31 .5.2 Other Applications 31-13 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxiii 

31.6 TESTS 31-13 

31.6.1 Test Method 31-13 

31 .6.2 Routine Tests 31-14 

31 .6.3 Performance Tests 31-14 

31.7 ACCESSORY MOUNTING 31-14 

Section IV PERFORMANCE STANDARDS APPLYING TO ALL MACHINES 
Part 32— SYNCHRONOUS GENERATORS (EXCLUSIVE OF GENERATORS 
COVERED BY ANSI STANDARDS C50.12, C50.13, C50.14, 
AND C50.15 ABOVE 5000 kVA) RATINGS 

32.0 SCOPE 32-1 

32.1 BASIS OF RATING 32-1 

32.2 KILOVOLT-AMPERE (KVA) AND (KW) RATINGS 32-1 

32.3 SPEED RATINGS 32-1 

32.4 VOLTAGE RATINGS 32-3 

32.4.1 Voltage Ratings for 60 Hz Circuits, Volts 32-3 

32.4.2 Voltage Ratings for 50 Hz Circuits, Volts 32-3 

32.5 FREQUENCIES 32-3 

32.6 TEMPERATURE RISE 32-3 

32.6.2 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 

but Not Below 0°C 32-5 

32.7 MAXIMUM MOMENTARY OVERLOADS 32-5 

32.8 OVERLOAD CAPABILITY 32-6 

32.9 OCCASIONAL EXCESS CURRENT 32-6 

32.10 MAXIMUM DEVIATION FACTOR 32-6 

32.11 TELEPHONE INFLUENCE FACTOR (TIF) 32-6 

32.12 EFFICIENCY 32-7 

32.13 SHORT-CIRCUIT REQUIREMENTS 32-8 

32.14 CONTINUOUS CURRENT UNBALANCE 32-8 

32.15 OPERATION WITH NON-LINEAR OR ASYMMETRIC LOADS 32-9 

32.16 OVERSPEEDS 32-9 

32.17 VARIATION FROM RATED VOLTAGE 32-10 

32.17.1 Broad Voltage Range 32-10 

32.17.2 Discrete Voltage 32-10 

32. 1 8 SYNCHRONOUS GENERATOR VOLTAGE REGULATION 

(VOLTAGE DIP) 32-10 

32.18.1 General 32-10 

32.18.2 Definitions 32-10 

32.18.3 Voltage Recorder Performance 32-12 

32.18.4 Examples 32-12 

32.18.5 Motor Starting Loads 32-12 

32.19 PERFORMANCE SPECIFICATION FORMS 32-15 

32.19.1 Slip-ring Synchronous Generators 32-15 

32.19.2 Brushless Synchronous Generators 32-16 

32.20 ROUTINE FACTORY TESTS 32-17 

32.20.1 Generators Not Completely Assembled in the Factory 32-17 

32.20.2 Generators Completely Assembled in the Factory 32-17 

32.21 HIGH-POTENTIAL TESTS 32-17 

32.21.1 Safety Precautions and Test Procedures 32-17 

32.21 .2 Test Voltage— Armature Windings 32-17 

32.21.3 Test Voltage— Field Windings, Generators with Slip Rings 32-17 

32.21.4 Test Voltage — Assembled Brushless Generator Field 

Winding and Exciter Armature Winding 32-17 

32.21.5 Test Voltage — Brushless Exciter Field Winding 32-18 

32.22 MACHINE SOUND SYNCHRONOUS (GENERATORS) 32-18 

32.22.1 Sound Quality 32-18 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxiv 

32.22.2 Sound Measurement 32-18 

32.23 VIBRATION 32-18 

MANUFACTURING DATA 32-19 

32.24 NAMEPLATE MARKING 32-19 

32.25 SHAFT EXTENSION KEY 32-19 

32.26 GENERATOR TERMINAL HOUSING 32-19 

32.27 EMBEDDED TEMPERATURE DETECTORS 32-20 

APPLICATION DATA 32-21 

32.29 PARALLEL OPERATION 32-21 

32.30 CALCULATION OF NATURAL FREQUENCY 32-21 

32.31 TORSIONAL VIBRATION 32-21 

32.32 MACHINES OPERATING ON AN UNGROUNDED SYSTEM 32-21 

32.33 SERVICE CONDITIONS 32-21 

32.33.1 General 32-21 

32.33.2 Usual Service Conditions 32-22 

32.33.3 Unusual Service Conditions 32-22 

32.34 NEUTRAL GROUNDING 32-23 

32.35 STAND-BY GENERATOR 32-23 

32.36 GROUNDING MEANS FOR FIELD WIRING 32-23 

Section IV PERFORMANCE STANDARDS APPLYING TO ALL MACHINES 
Part 33— DEFINITE PURPOSE SYNCHRONOUS GENERATORS FOR 
GENERATING SET APPLICATIONS 

33.0 SCOPE 33-1 

33.1 DEFINITIONS 33-1 

33.1.1 Rated Output Power 33-1 

33.1.2 Rated Speed of Rotation n 33-2 

33.1.3 Voltage Terms 33-2 

33.1.4 Performance Classes 33-4 

33.2 RATINGS 33-5 

33.2.1 Power Factor 33-5 

33.2.2 Kilovolt- Ampere (kVA) and Kilowatt (kW) Ratings 33-5 

33.2.3 Speed 33-6 

33.2.4 Voltage 33-6 

33.2.5 Frequencies 33-7 

33.3 PERFORMANCE 33-7 

33.3.1 Voltage and Frequency Variation 33-7 

33.3.2 Limits of Temperature and Temperature Rise 33-8 

33.3.3 Special Load Conditions 33-11 

33.3.4 Power Quality 33-12 

33.3.5 Overspeed 33-18 

33.3.6 Machine Sound 33-18 

33.3.7 Linear Vibration 33-19 

33.3.8 Testing 33-19 

33.3.9 Performance Specification Forms 33-22 

33.4 APPLICATIONS 33-24 

33.4.1 Service Conditions 33-24 

33.4.2 Transient Voltage Performance 33-25 

33.4.3 Torsional Vibration 33-29 

33.4.4 Generator Grounding .....33-29 

33.4.5 Cyclic Irregularity 33-30 

33.4.6 Application Criteria 33-30 

33.5 MANUFACTURING ^33-32 

33.5.1 Nameplate Marking 33-32 

33.5.2 Terminal Housings 33-33 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxv 



Foreword 

The standards appearing in this publication have been developed by the Motor and Generator Section 
and approved for publication as Standards of the National Electrical Manufacturers Association. They are 
intended to assist users in the proper selection and application of motors and generators. These 
standards are revised periodically to provide for changes in user needs, advances in technology, and 
changing economic trends. At! persons having experience in the selection, use, or manufacture of electric 
motors and generators are encouraged to submit recommendations that will improve the usefulness of 
these standards. Inquiries, comments, and proposed or recommended revisions should be submitted to 
the Motor and Generator Section by contacting: 

Vice President, Technical Services 
National Electrical Manufacturers Association 
1300 North 17th Street, Suite 1752 
Rosslyn, VA 22209 

The best judgment of the Motor and Generator Section on the performance and construction of motors 
and generators is represented in these standards. They are based upon sound engineering principles, 
research, and records of test and field experience. Also involved is an appreciation of the problems of 
manufacture, installation, and use derived from consultation with and information obtained from 
manufacturers, users, inspection authorities, and others having specialized experience. For machines 
intended for general applications, information as to user needs was determined by the individual 
companies through normal commercial contact with users. For some motors intended for definite 
applications, the organizations that participated in the development of the standards are listed at the 
beginning of those definite-purpose motor standards. 

Practical information concerning performance, safety, test, construction, and manufacture of alternating- 
current and direct-current motors and generators within the product scopes defined in the applicable 
section or sections of this publication is provided in these standards. Although some definite-purpose 
motors and generators are included, the standards do not apply to machines such as generators and 
traction motors for railroads, motors for mining locomotives, arc-welding generators, automotive 
accessory and toy motors and generators, machines mounted on airborne craft, etc. 

In the preparation and revision of these standards, consideration has been given to the work of other 
organizations whose standards are in any way related to motors and generators. Credit is hereby given to 
all those whose standards may have been helpful in the preparation of this volume. 

NEMA Standards Publication No. MG 1-2009 revises and supersedes the NEMA Standards Publication 
No. MG 1-2006, Revision 1-2007. Prior to publication, the NEMA Standards and Authorized Engineering 
Information that appear in this publication unchanged since the preceding edition were reaffirmed by the 
Motor and Generator Section. 

The standards or guidelines presented in a NEMA Standards Publication are considered technically 
sound at the time they are approved for publication. They are not a substitute for a product seller's or 
user's own judgment with respect to the particular product referenced in the standard or guideline, and 
NEMA does not undertake to guaranty the performance of any individual manufacturer's products by 
virtue of this standard or guide. Thus, NEMA expressly disclaims any responsibility for damages arising 
from the use, application, or reliance by others on the information contained in these standards or 
guidelines. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Page xxxvi 



This Standards Publication was developed by the Motors and Generator Section. Section approval of the 
standard does not necessarily imply that all section members voted for its approval or participated in its 
development. At the time it was approved, the Motors and Generator Section was composed of the following 
members: 

A.O. Smith Electric Products Co.— Tipp City, OH 

Baldor Electric Company— Fort Smith, AR 

Cummins, Inc. — Minneapolis, MN 

Emerson Motor Technologies — St. Louis, MO 

GE Consumer and Industrial — Ft. Wayne, IN 

Ram Industries — Leesport, PA 

Regal-Beloit Corporation— Beloit, Wl, composed of: 

Leeson Electric — Grafton, Wl 

Lincoln Motors — Cleveland, OH 

Marathon Electric Manufacturing Corporation— Wausau, Wl 

Electra-Gear— Union Grove, Wl 
SEW-Eurodrive, Inc.— Lyman, SC 
Siemens Industry, Inc.— Norcross, GA 
Sterling Electric, Inc.— Indianapolis, IN 
TECO-Westinghouse Motor Co.— Round Rock, TX 
Toshiba International Corporation— Houston, TX 
WEG Electric Motor Corp.— Duluth, GA 



© 2009 Copyright by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 1 



<This page is intentionally left blanks 



MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section I 
Part 1 , Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Parti 
REFERENCED STANDARDS AND DEFINITIONS 



1.1 



REFERENCED STANDARDS 



The following publications are adopted, in whole or in part as indicated, by reference in this standards 
publication. Mailing address of each reference organization is also provided. 

American National Standards institute (ANSI) 

11 West 42nd Street 
New York, NY 10036 



ANSI B92. 1-1970 (R1982) 

ANSI C84 1-1995 

ANSI S12.12-1992 (R1997, R2002) 



ANSIS12.51-2002 
ANSI S12.53-1 -1999 

ANSI S12.53-2-1 999 

ANSI S12.54-1999 
ANSI S12.55-2006 
ANSIS12.56-1999 
ANSI S12.57-2002 



ASTM D149-97a(2004) 



ASTM D635-06 



Involute Splines and Inspection 

Electric Power Systems and Equipment-Voltage Ratings (60 Hz) 
Engineering Method for the Determination of Sound Power 
Levels of Noise Sources Using Sound Intensity 
Acoustics - Determination of Sound Power Levels of Noise 
Sources Using Sound Pressure - Precision Methods for 
Reverberation Rooms 

Acoustics - Determination of Sound Power Levels of Noise 
Sources - Engineering Methods for Small, Movable Sources in 
Reverberant Fields - Part 1: Comparison Method for Hard- 
Walled Test Rooms 

Acoustics - Determination of Sound Power Levels of Noise 
Sources - Engineering Methods for Small, Movable Sources in 
Reverberant Fields - Part 2: Methods for Special Reverberation 
Test Rooms 

Acoustics - Determination of Sound Power Levels of Noise 
Sources Using Sound Pressure - Engineering Method in an 
Essentially Free Field Over a Reflecting Plane 
Acoustics - Determination of Sound Power Levels of Noise 
Sources Using Sound Pressure - Precision Methods for 
Anechoic and Hemi-Anechoic Rooms 
Acoustics - Determination of Sound Power Levels of Noise 
Sources Using Sound Pressure - Survey Method Using an 
Enveloping Measurement Surface Over a Reflecting Plane 
Standard Acoustics - Determination of Sound Power Levels of 
Noise Sources Using Sound Pressure - Comparison Method 
in Situ 



American Society for Testing and Materials (ASTM) 

1916 Race Street 
Philadelphia, PA 19103 

Standard Test Method for Dielectric Breakdown Voltage and Dielectric 

Strength of Solid Electrical Insulating Materials at Commercial Power 

Frequencies 

Standard Test Method for Rate of Burning and/or Extent and Time of 

Burning of Plastics in a Horizontal Position 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section I 
Part 1 , Page 2 



CSA 390-98 



Canadian Standards Association 

178 Rexdate Boulevard 
Toronto, Ontario, Canada M9W1R3 

Energy Efficiency Test Methods for Three-Phase Induction Motors 

Institute of Electrical and Electronics Engineers (IEEE) 1 

445 Hoes Lane 
Piscataway, NJ 08855-1331 



ANSI/IEEE Std 1-2000 

ANSI/IEEE Std 43-2000 

ANSI/IEEE Std 100-2000 
IEEE Std 112-2004 

ANSI/IEEE Std 115-1995 
ANSI/IEEE Std 117-1974 

(R1991.R2000) 
ANSI/IEEE Std 275-1992 (R1998) 

ANSI/IEEE Std 304-1977 (R1991) 
IEEE Std 522-2004 



General Principles for Temperature Limits in the Rating of 
Electric Equipment and for the Evaluation of Electrical Insulation 
Recommended Practice for Testing Insulation Resistance of 
Rotating Machinery 

Standard Dictionary of Electrical and Electronic Terms 
Standard Test Procedure for Polyphase Induction Motors and 
Generators 

Test Procedures for Synchronous Machines 
Standard Test Procedure for Evaluation of Systems of Insulating 
Materials for Random-Wound AC Electric Machinery 
Recommended Practice for Thermal Evaluation of Insulation 
Systems for AC Electric Machinery Employing Form-Wound P re- 
insulated Stator Coils, Machines Rated 6900V and Below 
Test Procedure for Evaluation and Classification of Insulation 
System for DC 

IEEE Guide for Testing Turn to Turn Insulation of Form-Wound 
Stator Coils for Alternating-Current Rotating Electric Machine 



Society of Automotive Engineers (SAE) 

3001 West Big Beaver 
Troy, Ml 48084 

ANSI/SAE J429-1999 Mechanical and Material Requirements for Externally Threaded Fasteners 

International Electrotechnical Commission (IEC) 1 

3 Rue de Varembe, CP 131, CH-1211 
Geneva 20, Switzerland 



IEC 60034-1-2004 
IEC 60034-8-2007 

IEC 60034-14-2003 



i IEC 60034-30-2008 



Rotating Electrical Machines- Part One: Rating and Performance 

Rotating Electrical Machines - Part Eight: Terminal Markings and Direction of 

Rotation 

Rotating Electrical Machines - Part 14: Mechanical Vibration of Certain 

Machines with Shaft Heights 56 mm and Higher— Measurement, Evaluation and 

Limits of Vibration Severity 

Efficiency classes of single-speed, three-phase, cage-induction motors (IE-code) 



1 Also available from ANSI. 
1 Also available from ANSI. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section I 
Part 1 , Page 3 



International Organization for Standardization (ISO) 1 

1, rue de Varembe 

1211 Geneva 20 

Switzerland 



ISO R-1 000-1 992 

ISO 3741: 1999 

ISO 3743-1: 1994(R2004) 

ISO 3743-2: 1994(R2004) 

ISO 3744: 1994 (R2004) 

ISO 3745: 2003 

ISO 3746: 1995(R2004) 

ISO 3747: 2000 
ISO 7919-1: 1996 
ISO 8528-3: 2005 

ISO 8528^:2005 

ISO 8821: 2002 
ISO 9614-1: 1993 

ISO 9614-2: 1996 

ISO 9614-3: 2002 

ISO 10816-3: 1998 



SI Units and Recommendations for the Use of their Multiples and of Certain 

Other Units 

Acoustics - Determination of Sound Power Levels of Noise Sources 

Using Sound Pressure - Precision Methods for Reverberation Rooms 

Acoustics - Determination of Sound Power Levels of Noise Sources - 

Engineering Methods for Small, Movable Sources in Reverberant Fields - 

Part 1: Comparison Method in Hard-Walled Test Rooms 

Acoustics - Determination of Sound Power Levels of Noise Sources - 

Engineering Methods for Small, Movable Sources in Reverberant Fields - 

Part 2: Method for Special Reverberation Test Rooms 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Pressure - Engineering Method Employing an Enveloping 

Measurement Surface in an Essentially Free Field Over a Reflecting Plane 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Pressure - Precision Methods forAnechoic and Hemi-Anechoic 

Rooms 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Pressure - Survey Method Using an Enveloping Measurement 

Surface Over a Reflecting Plane 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Pressure - Comparison Method in Situ 

Mechanical Vibration of Non-Reciprocating Machines - Measurements on 

Rotating Shafts and Evaluation Criteria - Part 1: General Guidelines 

Reciprocating Internal Combustion Engine-Driven Alternating Current 

Generating Sets - Part 3: Alternating Current Generators for Generating 

Sets 

Reciprocating Internal Combustion Engine-Driven Alternating Current 

Generating Sets - Part 4: Controlgear and Switchgear 

Mechanical Vibration - Shaft and Fitment Key Convention 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Intensity - Part 1: Measurement at Discrete Points 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Intensity - Part 2: Measurement by Scanning 

Acoustics - Determination of Sound Power Levels of Noise Sources Using 

Sound Intensity - Part 3: Precision Method for Measurement by Scanning 

Mechanical Vibration - Evaluation of Machine Vibration by Measurements on 

Non-Rotating Parts - Part 3: Industrial Machines with Nominal Power Above 

15 kWand Nominal Speeds Between 120 r/min and 15 000 r/min when 

measured in situ. 



National Electrical Manufacturers Association (NEMA) 

1300 North 17th Street, Suite 1752 
Rosslyn, VA 22209 



NEMA MG 2-1994 (R1999, R2007) 

NEMA MG 3-1974 (R1979, R1984, 
R2000, R2006) 



Safety Standard for Construction and Guide for Selection, 
Installation and Use of Electric Motors and Generators 
Sound Level Prediction for Installed Rotating 
Electrical Machines 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 4 



National Fire Protection Association (NFPA) 

Batterymarch Park 
Quincy, MA 02269 

ANSI/NFPA 70-2005 National Electrical Code 

Rubber Manufacturers Association 

1400 K Street NW 

Suite 300 

Washington, DC 20005 

Engineering Standards-Specifications for Drives Using Classical V-Belts and Sheaves (A, B, C, and D 

Cross-sections), 1988, 3 rd Edition, Pub#IP-20 
Engineering Standards-Specifications for Drives Using Narrow V-Belts and Sheaves 9N/9NX, 15N/15NX, 

25N (metric) and 3V/3VX, 5V/5VX, and 8V (inch-pound) Cross-sections; 1991, 3 rd Edition, Pub #IP-22 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 5 



DEFINITIONS 

(For definitions not found in Part 1, refer to IEEE Std 100, Standard Dictionary of Electrical and Electronic Terms.) 

CLASSIFICATION ACCORDING TO SIZE 

1.2 MACHINE 

As used in this standard a machine is an electrical apparatus which depends on electromagnetic 
induction for its operation and which has one or more component members capable of rotary movement. 
In particular, the types of machines covered are those generally referred to as motors and generators as 
defined in Part 1. 

1 .3 SMALL (FRACTIONAL) MACHINE 

A small machine is either: (1) a machine built in a two digit frame number series in accordance with 4.2.1 
(or equivalent for machines without feet); or (2) a machine built in a frame smaller than that frame of a 
medium machine (see 1.4) which has a continuous rating at 1700-1800 rpm of 1 horsepower for motors 
or 0.75 kilowatt for generators; or (3) a motor rated less than 1/3 horsepower and less than 800 rpm. 

1.4 MEDIUM (INTEGRAL) MACHINE 

1 .4.1 Alternating-Current Medium Machine 

An alternating-current medium machine is a machine: (1) built in a three- or four-digit frame number 
series in accordance with 4.2.1 (or equivalent for machines without feet); and (2) having a continuous 
rating up to and including the information in Table 1-1. 

1.4.2 Direct-Current Medium Machine 

A direct-current medium machine is a machine: (1) built in a three- or four-digit frame number series in 
accordance with 4.2.1 (or equivalent for machines without feet); and (2) having a continuous rating up to 
and including 1 .25 horsepower per rpm for motors or 1 .0 kilowatt per rpm for generators. 

Table 1-1 
ALTERNATING CURRENT MEDIUM MACHINE 







Generators, Kilowatt at 


Synchronous Speed, Rpm 


Motors Hp 


0.8 Power Factor 


1201-3600 


500 


400 


901-1200 


350 


300 


721-900 


250 


200 


601-720 


200 


150 


515-600 


150 


125 


451-514 


125 


100 



1.5 LARGE MACHINE 

1 .5.1 Alternating-Current Large Machine 

An alternating-current large machine is: (1) a machine having a continuous power rating greater than that 
given in 1.4.1 for synchronous speed ratings above 450 rpm; or (2) a machine having a continuous power 
rating greater than that given in 1 .3 for synchronous speed ratings equal to or below 450 rpm. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 6 



1.5.2 Direct-Current Large Machine 

A direct-current large machine is a machine having a continuous rating greater than 1 .25 horsepower per 
rpm for motors or 1 .0 kilowatt per rpm for generators. 

CLASSIFICATION ACCORDING TO APPLICATION 

(Some of the definitions in this section apply only to specific types or sizes of machines.) 

1 .6 GENERAL PURPOSE MOTOR 

1 .6.1 General-Purpose Alternating-Current Motor 

A general-purpose alternating-current motor is an induction motor, rated 500 horsepower and less, which 
incorporates all of the following: 

a. Open or enclosed construction 

b. Rated continuous duty 

c. Service factor in accordance with 12.51 

d. Class A or higher rated insulation system with a temperature rise not exceeding that specified in 12.42 

for Class A insulation for small motors or Class B or higher rated insulation system with a temperature 
rise not exceeding that specified in 12.43 for Class B insulation for medium motors. 

It is designed in standard ratings with standard operating characteristics and mechanical construction for 
use under usual service conditions without restriction to a particular application or type of application. 

1 .6.2 General-Purpose Direct-Current Small Motor 

A general-purpose direct-current small motor is a small motor of mechanical construction suitable for 
general use under usual service conditions and has ratings and constructional and performance 
characteristics applying to direct-current small motors as given in Parts 4, 10, 12, and 14. 

1 .7 GENERAL-PURPOSE GENERATOR 

A general-purpose generator is a synchronous generator of mechanical construction suitable for general 
use under usual service conditions and has ratings and constructional and performance characteristics as 
given in Part 32. 

1 .8 INDUSTRIAL SMALL MOTOR 

An industrial small motor is an alternating-current or direct-current motor built in either NEMA frame 42, 
48, or 56 suitable for industrial use. 

It is designed in standard ratings with standard operating characteristics for use under usual service 
conditions without restriction to a particular application or type of application. 

1 .9 INDUSTRIAL DIRECT-CURRENT MEDIUM MOTOR 

An industrial direct-current motor is a medium motor of mechanical construction suitable for industrial use 
under usual service conditions and has ratings and constructional and performance characteristics 
applying to direct current medium motors as given in Parts 4, 10, 12, and 14. 

1.10 INDUSTRIAL DIRECT-CURRENT GENERATOR 

An industrial direct-current generator is a generator of mechanical construction suitable for industrial use 
under usual service conditions and has ratings and constructional and performance characteristics 
applying to direct current generators as given in Part 4 and 1 5. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 7 



1 .1 1 DEFINITE-PURPOSE MOTOR 

A definite-purpose motor is any motor designed in standard ratings with standard operating 
characteristics or mechanical construction for use under service conditions other than usual or for use on 
a particular type of application. 

1.12 GENERAL INDUSTRIAL MOTORS 

A general industrial motor is a large dc motor of mechanical construction suitable for general industrial 
use (excluding metal rolling mill service), which may include operation at speeds above base speed by 
field weakening, and has ratings and constructional and performance characteristics applying to general 
industrial motors as given in Part 23. 

1.13 METAL ROLLING MILL MOTORS 

A metal rolling mill motor is a large dc motor of mechanical construction suitable for metal rolling mill 
service (except for reversing hot-mill service) and has ratings and constructional and performance 
characteristics applying to metal rolling mill motors as given in Part 23. 

1.14 REVERSING HOT MILL MOTORS 

A reversing hot mill motor is a large dc motor of mechanical construction suitable for reversing hot mill 
service, such as blooming and slabbing mills, and has ratings and constructional and performance 
characteristics applying to reversing hot mill motors as given in Part 23. 

1.15 SPECIAL-PURPOSE MOTOR 

A special-purpose motor is a motor with special operating characteristics or special mechanical 
construction, or both, designed for a particular application and not falling within the definition of a general- 
purpose or definite-purpose motor. 

1.16 

[Section deleted] 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 8 



CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 
1.17 GENERAL 

1 .1 7.1 Electric Motor 

An electric motor is a machine that transforms electric power into mechanical power. 

1.17.2 Electric Generator 

An electric generator is a machine that transforms mechanical power into electric power. 

1.17.3 Electric Machines 
1.17.3.1 Asynchronous Machine 

An asynchronous machine is an alternating-current machine in which the rotor does not turn at a 
synchronous speed. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 9 



1.17.3.2 Direct-Current (Commutator) Machine 

A direct-current (commutator) machine is a machine incorporating an armature winding connected to a 
commutator and magnetic poles which are excited from a direct-current source or permanent magnets. 

1.17.3.3 Induction Machine 

An induction machine is an asynchronous machine that comprises a magnetic circuit interlinked with two 
electric circuits, or sets of circuits, rotating with respect to each other and in which power is transferred 
from one circuit to another by electromagnetic induction. 

1.17.3.4 Synchronous Machine 

A synchronous machine is an alternating-current machine in which the average speed of normal 
operation is exactly proportional to the frequency of the system to which it is connected. 

1 .18 ALTERNATING-CURRENT MOTORS 

Alternating-current motors are of three general types: induction, synchronous, and series-wound and are 
defined as follows. 

1.18.1 Induction Motor 

An induction motor is an induction machine in which a primary winding on one member (usually the 
stator) is connected to the power source, and a polyphase secondary winding or a squirrel-cage 
secondary winding on the other member (usually the rotor) carries induced current. 

1.18.1.1 Squirrel-Cage Induction Motor 

A squirrel-cage induction motor is an induction motor in which the secondary circuit (squirrel-cage 
winding) consists of a number of conducting bars having their extremities connected by metal rings or 
plates at each end. 

1.18.1.2 Wound-Rotor Induction Motor 

A wound-rotor induction motor is an induction motor in which the secondary circuit consists of a 
polyphase winding or coils whose terminals are either short-circuited or closed through suitable circuits. 

1 .1 8.2 Synchronous Motor 

A synchronous motor is a synchronous machine for use as a motor. 

1.18.2.1 Direct-Current-Excited Synchronous Motor 

Unless otherwise stated, it is generally understood that a synchronous motor has field poles excited by 
direct current. 

1.18.2.2 Permanent-Magnet Synchronous Motor 

A permanent-magnet synchronous motor is a synchronous motor in which the field excitation is provided 
by permanent magnets. 

1.18.2.3 Reluctance Synchronous Motor 

A reluctance synchronous motor is a synchronous motor similar in construction to an induction motor, in 
which the member carrying the secondary circuit has a cyclic variation of reluctance providing the effect of 
salient poles, without permanent magnets or direct-current excitation. It starts as an induction motor, is 
normally provided with a squirrel-cage winding, but operates normally at synchronous speed. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 10 



1.18.3 Series-Wound Motor 

A series-wound motor is a commutator motor in which the field circuit and armature are connected in 
series. 

1 .1 9 POLYPHASE MOTORS 

Alternating-current polyphase motors are of the squirrel-cage induction, wound-rotor induction, or 
synchronous types. 

1 .19.1 Design Letters of Polyphase Squirrel-Cage Medium Motors 

Polyphase squirrel-cage medium induction motors may be one of the following: 

1.19.1.1 Design A 

A Design A motor is a squirrel-cage motor designed to withstand full-voltage starting and developing 
locked-rotor torque as shown in 12.38, pull-up torque as shown in 12.40, breakdown torque as shown in 

12.39, with locked-rotor current higher than the values shown in 12.35.1 for 60 hertz and 12.35.2 for 50 
hertz and having a slip at rated load of less than 5 percent. 1 

1.19.1.2 Design B 

A Design B motor is a squirrel-cage motor designed to withstand full-voltage starting, developing locked- 
rotor, breakdown, and pull-up torques adequate for general application as specified in 12.38, 12.39, and 

12.40, drawing locked-rotor current not to exceed the values shown in 12.35.3 for 60 hertz and 12.35.3 
for 50 hertz, and having a slip at rated load of less than 5 percent. 1 

1.19.1.3 Design C 

A Design C motor is a squirrel-cage motor designed to withstand full-voltage starting, developing locked- 
rotor torque for special high-torque application up to the values shown in 12.38, pull-up torque as shown 
in 12.40, breakdown torque up to the values shown in 12.39, with locked-rotor current not to exceed the 
values shown in 12.34.1 for 60 hertz and 12.35.2 for 50 hertz, and having a slip at rated load of less than 
5 percent. 

1.19.1.4 Design D 

A Design D motor is a squirrel-cage motor designed to withstand full-voltage starting, developing high 
locked rotor torque as shown in 12.38, with locked rotor current not greater than shown in 12.35.1 for 60 
hertz and 12.35.2 for 50 hertz, and having a slip at rated load of 5 percent or more. 

1.20 SINGLE-PHASE MOTORS 

Alternating-Current single-phase motors are usually induction or series-wound although single-phase 
synchronous motors are available in the smaller ratings. 

1 .20.1 Design Letters of Single-Phase Small Motors 

1.20.1.1 Design N 

A Design N motor is a single-phase small motor designed to withstand full-voltage starting and with a 
locked-rotor current not to exceed the values shown in 12.33. 

1.20.1.2 Design O 

A Design O motor is a single-phase small motor designed to withstand full-voltage starting and with a 
locked-rotor current not to exceed the values shown in 12.33. 



1 Motors with 10 or more poles shall be permitted to have slip slightly greater than 5 percent. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 1 1 



1 .20.2 Design Letters of Single-Phase Medium Motors 

Single-phase medium motors include the following: 

1.20.2.1 Design L 

A Design L motor is a single-phase medium motor designed to withstand full-voltage starting and to 
develop a breakdown torque as shown in 10.34 with a locked-rotor current not to exceed the values 
shown in 12.34. 

1.20.2.2 Design M 

A Design M motor is a single-phase medium motor designed to withstand full-voltage starting and to 
develop a breakdown torque as shown in 10.34 with a locked-rotor current not to exceed the values 
shown in 12.33. 

1 .20.3 Single-Phase Squirrel-Cage Motors 

Single-phase squirrel-cage induction motors are classified and defined as follows: 

1.20.3.1 Split-Phase Motor 

A split-phase motor is a single-phase induction motor equipped with an auxiliary winding, displaced in 
magnetic position from, and connected in parallel with, the main winding. 

Unless otherwise specified, the auxiliary circuit is assumed to be opened when the motor has attained a 
predetermined speed. The term "split-phase motor," used without qualification, describes a motor to be 
used without impedance other than that offered by the motor windings themselves, other types being 
separately defined. 

1.20.3.2 Resistance-Start Motor 

A resistance-start motor is a form of split-phase motor having a resistance connected in series with the 
auxiliary winding. The auxiliary circuit is opened when the motor has attained a predetermined speed. 

1.20.3.3 Capacitor Motor 

A capacitor motor is a single-phase induction motor with a main winding arranged for direct connection to 
a source of power and an auxiliary winding connected in series with a capacitor. There are three types of 
capacitor motors, as follows. 

1.20.3.3.1 Capacitor-Start Motor 

A capacitor-start motor is a capacitor motor in which the capacitor phase is in the circuit only during the 
starting period. 

1.20.3.3.2 Permanent-Split Capacitor Motor 

A permanent-split capacitor motor is a capacitor motor having the same value of capacitance for both 
starting and running conditions. 

1.20.3.3.3 Two-Value Capacitor Motor 

A two-value capacitor motor is a capacitor motor using different values of effective capacitance for the 
starting and running conditions. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 12 



1.20.3.4 Shaded-Pole Motor 

A shaded-pole motor is a single-phase induction motor provided with an auxiliary short-circuited winding 
or windings displaced in magnetic position from the main winding. 

1 .20.4 Single-Phase Wound-Rotor Motors 

Single-phase wound-rotor motors are defined and classified as follows: 

1.20.4.1 Repulsion Motor 

A repulsion motor is a single-phase motor which has a stator winding arranged for connection to a source 
of power and a rotor winding connected to a commutator. Brushes on the commutator are short-circuited 
and are so placed that the magnetic axis of the rotor winding is inclined to the magnetic axis of the stator 
winding. This type of motor has a varying-speed characteristic. 

1.20.4.2 Repulsion-Start Induction Motor 

A repulsion-start induction motor is a single-phase motor having the same windings as a repulsion motor, 
but at a predetermined speed the rotor winding is short-circuited or otherwise connected to give the 
equivalent of a squirrel-cage winding. This type of motor starts as a repulsion motor but operates as an 
induction motor with constant speed characteristics. 

1.20.4.3 Repulsion-Induction Motor 

A repulsion-induction motor is a form of repulsion motor which has a squirrel-cage winding in the rotor in 
addition to the repulsion motor winding. A motor of this type may have either a constant-speed (see 1.30) 
or varying-speed (see 1.31) characteristic. 

1 .21 UNIVERSAL MOTORS 

A universal motor is a series-wound motor designed to operate at approximately the same speed and 
output on either direct-current or single-phase alternating-current of a frequency not greater than 60 hertz 
and approximately the same rms voltage. 

1 .21 .1 Series-Wound Motor 

A series-wound motor is a commutator motor in which the field circuit and armature circuit are connected 
in series. 

1.21.2 Compensated Series-Wound Motor 

A compensated series-wound motor is a series-wound motor with a compensating field winding. The 
compensating field winding and the series field winding shall be permitted to be combined into one field 
winding. 

1 .22 ALTERNATING-CURRENT GENERATORS 

Alternating-current generators are of two basic types, induction and synchronous, and are defined as 
follows: 

1 .22.1 Induction Generator 

An induction generator is an induction machine driven above synchronous speed by an external source of 
mechanical power for use as a generator. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 1 3 



1 .22.2 Synchronous Generator 

A synchronous generator is a synchronous machine for use as a generator. 

NOTE — Unless otherwise stated it is generally understood that a synchronous generator has field poles excited by 
direct current. 

1 .23 DIRECT-CURRENT MOTORS 

Direct-current motors are of four general types — shunt-wound, series-wound, compound-wound, and 
permanent magnet, and are defined as follows. 

1 .23.1 Shunt-Wound Motor 

A shunt-wound motor is either a straight shunt-wound motor or a stabilized shunt-wound motor. 

1 .23.1 .1 Straight Shunt-Wound Motor 

A straight shunt-wound motor is a direct-current motor in which the field circuit is connected either in 
parallel with the armature circuit or to a separate source of excitation voltage. The shunt field is the only 
winding supplying field excitation. 

1.23.1.2 Stabilized Shunt-Wound Motor 

A stabilized shunt-wound motor is a direct-current motor in which the shunt field circuit is connected either 
in parallel with the armature circuit or to a separate source of excitation voltage and which also has a light 
series winding added to prevent a rise in speed or to obtain a slight reduction in speed with increase in 
load. 

1 .23.2 Series-Wound Motor 

A series-wound motor is a motor in which the field circuit and armature circuit are connected in series. 

1.23.3 Compound-Wound Motor 

A compound-wound motor is a direct-current motor which has two separate field windings-one, usually 
the predominating field, connected as in a straight shunt-wound motor, and the other connected in series 
with the armature circuit. 

1 .23.4 Permanent Magnet Motor 

A permanent magnet motor is a direct-current motor in which the field excitation is supplied by permanent 
magnets. 

1 .24 DIRECT-CURRENT GENERATORS 

Direct-current generators are of two general types — shunt-wound and compound-wound — and are 
defined as follows: 

1 .24.1 Shunt-Wound Generator 

A shunt-wound generator is a direct-current generator in which the field circuit is connected either in 
parallel with the armature circuit or to a separate source of excitation voltage. 

1 .24.2 Compound-Wound Generator 

A compound-wound generator is a direct-current generator which has two separate field windings — one, 
usually the predominating field, connected as in a shunt-wound generator, and the other connected in 
series with the armature circuit. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 14 



CLASSIFICATION ACCORDING TO ENVIRONMENTAL PROTECTION 
AND METHODS OF COOLING 

Details of protection (IP) and methods of cooling (IC) are defined in Part 5 and Part 6, respectively. They 
conform to IEC Standards. 

1.25 OPEN MACHINE (IP00, IC01) 

An open machine is one having ventilating openings which permit passage of external cooling air over 
and around the windings of the machine. The term "open machine," when applied in large apparatus 
without qualification, designates a machine having no restriction to ventilation other than that necessitated 
by mechanical construction. 

1.25.1 Dripproof Machine (IP12, IC01) 

A dripproof machine is an open machine in which the ventilating openings are so constructed that 
successful operation is not interfered with when drops of liquid or solid particles strike or enter the 
enclosure at any angle from to 15 degrees downward from the vertical. 

The machine is protected against solid objects greater than 1.968 inches (50 mm). 

1.25.2 Splash-Proof Machine (IP13, IC01) 

A splash-proof machine is an open machine in which the ventilating openings are so constructed that 
successful operation is not interfered with when drops of liquid or solid particles strike or enter the 
enclosure at any angle not greater than 60 degrees downward from the vertical. 

The machine is protected against solid objects greater than 1.968 inches (50 mm). 

1 .25.3 Semi-Guarded Machine (IC01 ) 

A semi-guarded machine is an open machine in which part of the ventilating openings in the machine, 
usually in the top half, are guarded as in the case of a "guarded machine" but the others are left open. 

1.25.4 Guarded Machine (IC01) 

A guarded machine is an open machine in which all openings giving direct access to live metal or rotating 
parts (except smooth rotating surfaces) are limited in size by the structural parts or by screens, baffles, 
grilles, expanded metal, or other means to prevent accidental contact with hazardous parts. 

The openings in the machine enclosure shall be such that (1) a probe such as that illustrated in Figure 1- 
1, when inserted through the openings, will not touch a hazardous rotating part; (2) a probe such as that 
illustrated in Figure 1-2 when inserted through the openings, will not touch film-coated wire; and (3) an 
articulated probe such as that illustrated in Figure 1-3, when inserted through the openings, will not touch 
an uninsulated live metal part. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section 1 
Parti, Page 15 



R=0.19 



0.75 



ANY 

CONVENIENT 

LENGTH 



4.0 



■j 0.56 *- 



D=0.50 



Figure 1-1* 
PROBE FOR HAZARDOUS ROTATING PARTS 



R=0.25 



t 














0.75 


J 


t 


ANY 


~* a n •- 




"* *KU 






D=0.50 



CONVENIENT 
LENGTH 



Figure 1-2* 
PROBE FOR FILM-COATED WIRE 



* All dimensions in inches. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section 1 
Parti, Page 16 



75 



Both joints of this finger may bend 
through an angle of 90°, but in one 
and the same direction only. 
Dimensions in millimeters. 

Tolerances: 

On angles: +5° 

On linear dimensions: 
Less than 25mm: +0.05 
More than 25 mm: +0.2 



Guard 




Figure 1-3 
ARTICULATED PROBE FOR UNINSULATED LIVE METAL PARTS 
(Reproduced with permission of IEC, which retains the copyright) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1, Page 17 



1 .25.5 Dripproof Guarded Machine (IC01 ) 

A dripproof guarded machine is a dripproof machine whose ventilating openings are guarded in 
accordance with 1.25.4. 

1.25.6 Open Independently Ventilated Machine (IC06) 

An open independently ventilated machine is one which is ventilated by means of a separate motor- 
driven blower mounted on the machine enclosure. Mechanical protection shall be as defined in 1.25.1 to 
1.25.5, inclusive. This machine is sometimes known as a blower-ventilated machine. 

1.25.7 Open Pipe-Ventilated Machine 

An open pipe-ventilated machine is an open machine except that openings for the admission of the 
ventilating air are so arranged that inlet ducts or pipes can be connected to them. Open pipe-ventilated 
machines shall be self-ventilated (air circulated by means integral with the machine) (IC11) or force- 
ventilated (air circulated by means external to and not a part of the machine) (IC17). Enclosures shall be 
as defined in 1.25.1 to 1.25.5, inclusive. 

1.25.8 Weather-Protected Machine 

1.25.8.1 Typel(ICOI) 

A weather-protected Type I machine is a guarded machine with its ventilating passages so constructed as 
to minimize the entrance of rain, snow and air-borne particles to the electric parts. 

1.25.8.2 Typell(ICOI) 

A weather-protected Type II machine shall have, in addition to the enclosure defined for a weather- 
protected Type I machine, its ventilating passages at both intake and discharge so arranged that high- 
velocity air and air-borne particles blown into the machine by storms or high winds can be discharged 
without entering the internal ventilating passages leading directly to the electric parts of the machine itself. 
The normal path of the ventilating air which enters the electric parts of the machine shall be so arranged 
by baffling or separate housings as to provide at least three abrupt changes in direction, none of which 
shall be less than 90 degrees. In addition, an area of low velocity not exceeding 600 feet per minute shall 
be provided in the intake air path to minimize the possibility of moisture or dirt being carried into the 
electric parts of the machine. 
NOTE— Removable or otherwise easy to clean filters may be provided instead of the low velocity chamber. 

1 .26 TOTALLY ENCLOSED MACHINE 

A totally enclosed machine is so enclosed as to prevent the free exchange of air between the inside and 
outside of the case but not sufficiently enclosed to be termed air-tight and dust does not enter in sufficient 
quantity to interfere with satisfactory operation of the machine. 

1 .26.1 Totally Enclosed Nonventilated Machine (IC41 0) 

A totally enclosed nonventilated machine is a frame-surface cooled totally enclosed machine which is 
only equipped for cooling by free convection. 

1.26.2 Totally Enclosed Fan-Cooled Machine 

A totally enclosed fan-cooled machine is a frame-surface cooled totally enclosed machine equipped for 
self exterior cooling by means of a fan or fans integral with the machine but external to the enclosing 
parts. 



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MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 18 



1.26.3 Totally Enclosed Fan-Cooled Guarded Machine (IC411) 

A totally-enclosed fan-cooled guarded machine is a totally-enclosed fan-cooled machine in which all 
openings giving direct access to the fan are limited in size by the design of the structural parts or by 
screens, grilles, expanded metal, etc., to prevent accidental contact with the fan. Such openings shall not 
permit the passage of a cylindrical rod 0.75 inch diameter, and a probe such as that shown in Figure 1-1 
shall not contact the blades, spokes, or other irregular surfaces of the fan. 

1.26.4 Totally Enclosed Pipe-Ventilated Machine (IP44) 

A totally enclosed pipe-ventilated machine is a machine with openings so arranged that when inlet and 
outlet ducts or pipes are connected to them there is no free exchange of the internal air and the air 
outside the case. Totally enclosed pipe-ventilated machines may be self-ventilated (air circulated by 
means integral with the machine (IC31)) or force-ventilated (air circulated by means external to and not 
part of the machine (IC37)). 

1.26.5 Totally Enclosed Water-Cooled Machine (IP54) 

A totally enclosed water-cooled machine is a totally enclosed machine which is cooled by circulating 
water, the water or water conductors coming in direct contact with the machine parts. 

1 .26.6 Water-Proof Machine (IP55) 

A water-proof machine is a totally enclosed machine so constructed that it will exclude water applied in 
the form of a stream of water from a hose, except that leakage may occur around the shaft provided it is 
prevented from entering the oil reservoir and provision is made for automatically draining the machine. 
The means for automatic draining may be a check valve or a tapped hole at the lowest part of the frame 
which will serve for application of a drain pipe. 

1.26.7 Totally Enclosed Air-to-Water-Cooled Machine (IP54) 

A totally enclosed air-to-water-cooled machine is a totally enclosed machine which is cooled by circulating 
air which, in turn, is cooled by circulating water. It is provided with a water-cooled heat exchanger, integral 
(IC7_W) or machine mounted (IC8J/V), for cooling the internal air and a fan or fans, integral with the rotor 
shaft (ICJW) or separate (IC_5W) for circulating the internal air. 

1 .26.8 Totally Enclosed Air-to-Air-Cooled Machine (IP54) 

A totally enclosed air-to-air-cooled machine is a totally enclosed machine which is cooled by circulating 
the internal air through a heat exchanger which, in turn, is cooled by circulating external air. It is provided 
with an air-to-air heat exchanger, integral (IC5J, or machine mounted (IC6_), for cooling the internal air 
and a fan or fans, integral with the rotor shaft (IC_1_) or separate (IC_5J for circulating the internal air 
and a fan or fans, integral with the rotor shaft (IC_1), or separate, but external to the enclosing part or 
parts (IC_6), for circulating the external air. 

1.26.9 Totally Enclosed Air-Over Machine (IP54, IC417) 

A totally enclosed air-over machine is a totally enclosed frame-surface cooled machine intended for 
exterior cooling by a ventilating means external to the machine. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 . Page 1 9 



1.26.10 Explosion-Proof Machine 1 

An explosion-proof machine is a totally enclosed machine whose enclosure is designed and constructed 
to withstand an explosion of a specified gas or vapor which may occur within it and to prevent the ignition 
of the specified gas or vapor surrounding the machine by sparks, flashes, or explosions of the specified 
gas or vapor which may occur within the machine casing. 

1.26.11 Dust-Ignition-Proof Machine 2 

A dust-ignition proof machine is a totally enclosed machine whose enclosure is designed and constructed 
in a manner which will exclude ignitable amounts of dust or amounts which might affect performance or 
rating, and which will not permit arcs, sparks, or heat otherwise generated or liberated inside of the 
enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specific dust on or 
in the vicinity of the enclosure. 

Successful operation of this type of machine requires avoidance of overheating from such causes as 
excessive overloads, stalling, or accumulation of excessive quantities of dust on the machine. 

1 .27 MACHINE WITH ENCAPSULATED OR SEALED WINDINGS 

1 .27.1 Machine with Moisture Resistant Windings 3 

A machine with moisture-resistant windings is one in which the windings have been treated such that 
exposure to a moist atmosphere will not readily cause malfunction. This type of machine is intended for 
exposure to moisture conditions that are more excessive than the usual insulation system can withstand. 

Alternating-current squirrel-cage machines of this type shall be capable of passing the test described in 
12.63 as demonstrated on a representative sample or prototype. 

1 .27.2 Machine with Sealed Windings 1 

A machine with sealed windings is one which has an insulation system which, through the use of 
materials, processes, or a combination of materials and processes, results in windings and connections 
that are sealed against contaminants. This type of machine is intended for environmental conditions that 
are more severe than the usual insulation system can withstand. 

Alternating-current squirrel-cage machines of this type shall be capable of passing the tests described in 
12.62 or 20.18. 

CLASSIFICATION ACCORDING TO VARIABILITY OF SPEED 

1 .30 CONSTANT-SPEED MOTOR 

A constant-speed motor is one in which the speed of normal operation is constant or practically constant; 
for example, a synchronous motor, an induction motor with small slip, or a DC shunt-wound motor. 

1 .31 VARYING-SPEED MOTOR 

A varying-speed motor is one in which the speed varies with the load, ordinarily decreasing when the load 
increases; such as a series-wound or repulsion motor. 



1 See ANSI/NFPA 70, National Electrical Code, Article 500. For Hazardous Locations, Class I, Groups A, B, C, or D. 

2 See ANSt/NFPA 70, National Electrical Code, Article 500. For Hazardous Locations, Class II, Groups E, F, or G. 

3 This machine shall be permitted to have any one of the enclosures described in 1 .25 or 1 .26. 



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REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 20 



1.32 ADJUSTABLE-SPEED MOTOR 

An adjustable-speed motor is one in which the speed can be controlled over a defined range, but when 
once adjusted remains practically unaffected by the load. 

Examples of adjustable-speed motors are: a direct-current shunt-wound motor with field resistance 
control designed for a considerable range of speed adjustment; or an alternating-current motor controlled 
by an adjustable frequency power supply. 

1 .33 BASE SPEED OF AN ADJUSTABLE-SPEED MOTOR 

The base speed of an adjustable-speed motor is the lowest rated speed obtained at rated load and rated 
voltage at the temperature rise specified in the rating. 

1.34 ADJUSTABLE VARYING-SPEED MOTOR 

An adjustable varying-speed motor is one in which the speed can be adjusted gradually, but when once 
adjusted for a given load will vary in considerable degree with change in load; such as a DC compound- 
wound motor adjusted by field control or a wound-rotor induction motor with rheostatic speed control. 

1 .35 MULTISPEED MOTOR 

A multispeed motor is one which can be operated at any one of two or more definite speeds, each being 
practically independent of the load; for example, a DC motor with two armature windings or an induction 
motor with windings capable of various pole groupings. In the case of multispeed permanent-split 
capacitor and shaded pole motors, the speeds are dependent upon the load. 

RATING, PERFORMANCE, AND TEST 

1.40 RATING OF A MACHINE 

The rating of a machine shall consist of the output power together with any other characteristics, such as 
speed, voltage, and current, assigned to it by the manufacturer. For machines which are designed for 
absorbing power, the rating shall be the input power. 

1.40.1 Continuous Rating 

The continuous rating defines the load which can be carried for an indefinitely long period of time. 

1 .40.2 Short-Time Rating 

The short-time rating defines the load which can be carried for a short and definitely specified time, less 
than that required to reach thermal equilibrium, when the initial temperature of the machine is within 5°C 
of the ambient temperature. Between periods of operation the machine is de-energized and permitted to 
remain at rest for sufficient time to re-establish machine temperatures within 5°C of the ambient before 
being operated again. 

1.41 EFFICIENCY 

1.41.1 General 

The efficiency of a motor or generator is the ratio of its useful power output to its total power input and is 
usually expressed in percentage. 

1.41.2 Energy Efficient Polyphase Squirrel-Cage Induction Motor 

An energy efficient polyphase squirrel-cage induction motor is one having an efficiency in accordance 
with 12.59. 



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1 .41 .3 Premium Efficiency Motor 

3 A premium efficiency motor is one having an efficiency in accordance with 12.60. 

1 .42 SERVICE FACTOR—AC MOTORS 

The service factor of an AC motor is a multiplier which, when applied to the rated horsepower, indicates a 
permissible horsepower loading which may be carried under the conditions specified for the service factor 
(see 14.37). 

1 .43 SPEED REGULATION OF DC MOTORS 

The speed regulation of a DC motor is the difference between the steady no-load speed and the steady 
rated-load speed, expressed in percent of rated-load speed. 

1 .43.1 Percent Compounding of Direct-Current Machines 

The percent of the total field-ampere turns at full load that is contributed by the series field. 

NOTES 

1— The percent compounding is determined at rated shunt field current. 

2— Percent regulation of a compound-wound DC motor or generator is related to but not the same as percent 
compounding. 

1 .44 VOLTAGE REGULATION OF DIRECT-CURRENT GENERATORS 

The voltage regulation of a direct-current generator is the final change in voltage with constant field 
rheostat setting when the specified load is reduced gradually to zero, expressed as a percent of rated- 
load voltage, the speed being kept constant. 

NOTE — In practice, it is often desirable to specify the overall regulation of the generator and its driving machine, thus 
taking into account the speed regulation of the driving machine. 

1 .45 SECONDARY VOLTAGE OF WOUND-ROTOR MOTORS 

The secondary voltage of wound-rotor motors is the open-circuit voltage at standstill, measured across 
the slip rings, with rated voltage applied on the primary winding. 

1 .46 FULL-LOAD TORQUE 

The full-load torque of a motor is the torque necessary to produce its rated horsepower at full-load speed. 
In pounds at a foot radius, it is equal to the horsepower times 5252 divided by the full-load speed. 

1.47 LOCKED-ROTOR TORQUE (STATIC TORQUE) 

The locked-rotor torque of a motor is the minimum torque which it will develop at rest for all angular 
positions of the rotor, with rated voltage applied at rated frequency. 

1.48 PULL-UP TORQUE 

The pull-up torque of an alternating-current motor is the minimum torque developed by the motor during 
the period of acceleration from rest to the speed at which breakdown torque occurs. For motors which do 
not have a definite breakdown torque, the pull-up torque is the minimum torque developed up to rated 
speed. 

1.49 PUSHOVER TORQUE 

The pushover torque of an induction generator is the maximum torque which it will absorb with rated 
voltage applied at rated frequency, without an abrupt increase in speed. 



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1 .50 BREAKDOWN TORQUE 

The breakdown torque of a motor is the maximum torque which it will develop with rated voltage applied 
at rated frequency, without an abrupt drop in speed. 

1.51 PULL-OUT TORQUE 

The pull-out torque of a synchronous motor is the maximum sustained torque which the motor will 
develop at synchronous speed with rated voltage applied at rated frequency and with normal excitation. 

1.52 PULL-IN TORQUE 

The pull-in torque of a synchronous motor is the maximum constant torque under which the motor will pull 
its connected inertia load into synchronism, at rated voltage and frequency, when its field excitation is 
applied. 

The speed to which a motor will bring its load depends on the power required to drive it, and whether the 
motor can pull the load into step from this speed, depends on the inertia of the revolving parts, so that the 
pull-in torque cannot be determined without having the i/Wc 2 as well as the torque of the load. 

1 .53 LOCKED-ROTOR CURRENT 

The locked-rotor current of a motor is the steady-state current taken from the line, with the rotor locked 
and with rated voltage (and rated frequency in the case of alternating-current motors) applied to the 
motor. 

1.54 NO-LOAD CURRENT 

No-load current is the current flowing through a line terminal of a winding. 

1.55 TEMPERATURE TESTS 

Temperature tests are tests taken to determine the temperature rise of certain parts of the machine above 
the ambient temperature, when running under a specified load. 

1 .56 AMBIENT TEMPERATURE 

Ambient temperature is the temperature of the surrounding cooling medium, such as gas or liquid, which 
comes into contact with the heated parts of the apparatus. 

NOTE— Ambient temperature is commonly known as "room temperature" in connection with air-cooled apparatus not 
provided with artificial ventilation. 

1 .57 HIGH-POTENTIAL TESTS 

High-potential tests are tests which consist of the application of a voltage higher than the rated voltage for 
a specified time for the purpose of determining the adequacy against breakdown of insulating materials 
and spacings under normal conditions. (See Part 3.) 

1.58 STARTING CAPACITANCE FOR A CAPACITOR MOTOR 

The starting capacitance for a capacitor motor is the total effective capacitance in series with the starting 
winding under locked-rotor conditions. 



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REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 23 

1 .59 RADIAL MAGNETIC PULL AND AXIAL CENTERING FORCE 

1 .59.1 Radial Magnetic Pull 

The radial magnetic pull of a motor or generator is the magnetic force on the rotor resulting from its radial 
(air gap) displacement from magnetic center. 

1.59.2 Axial Centering Force 

The axial centering force of a motor or generator is the magnetic force on the rotor resulting from its axial 
displacement from magnetic center. 

Unless other conditions are specified, the value of radial magnetic pull and axial centering force will be for 
no load, with rated voltage, rated field current, and rated frequency applied, as applicable. 

1 .60 INDUCTION MOTOR TIME CONSTANTS 

1.60.1 General 

When a polyphase induction motor is open-circuited or short-circuited while running at rated speed, the 
rotor flux-linkages generate a voltage in the stator winding. The decay of the rotor-flux linkages, and the 
resultant open-circuit terminal voltage or short-circuit current, is determined by the various motor time 
constants defined by the following equations. 



1 .60.2 Open-Circuit AC Time Constant 

XjyjjkX? 

27ifr 9 



T "do = # " r . 2 (seconds) 



1 .60.3 Short-Circuit AC Time Constant 

T" d =v^V r do (seconds) 

A 1 + A M 



1.60.4 Short-Circuit DC Time Constant 



j a _ _ _s (seconds) 



2nfr<i i 



1.60.5 X/R Ratio 



Xc 

X/R - — — § — =r (radians) 



1 LL s^ 

1 + 2- 

kwjj 

1.60.6 Definitions (See Figure 1-4) 

n = Stator DC resistance per phase corrected to operating temperature 

r 2 = Rotor resistance per phase at rated speed and operating temperature referred to stator 

Xi = Stator leakage reactance per phase at rated current 

X 2 = Rotor leakage reactance per phase at rated speed and rated current referred to stator 

X s = Total starting reactance (stator and rotor) per phase at zero speed and locked-rotor current 

X M = Magnetizing reactance per phase 

LL S = Fundamental-frequency component of stray-load loss in kW at rated current 



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MG 1-2009 Section 1 

REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 24 



kW! = Stator l 2 R loss in kW at rated current and operating temperature 



f = Rated frequency, hertz 

s = Slip in per unit of synchronous speed 



■A/WV — nmnn 




Figure 1-4 
EQUIVALENT CIRCUIT 

COMPLETE MACHINES AND PARTS 

1 .61 SYNCHRONOUS GENERATOR— COMPLETE 

1.61.1 Belted Type 

A belted-type generator consists of a generator with a shaft extension suitable for the driving pulley or 
sheave, with either two or three bearings as required, and with rails or with a sliding base which has 
provision for adjusting belt tension. 

1.61.2 Engine Type 

An engine-type generator consists of a stator, rotor (without shaft), foundation caps or sole plates, and 
brush rigging support. No base, bearings, shaft, shaft keys, or foundation bolts are included in generators 
of this type. 

1.61.3 Coupled Type 

A coupled-type generator consists of a generator with shaft extension for coupling and with one or two 
bearings. 

1 .62 DIRECT-CURRENT GENERATOR—COMPLETE 

1.62.1 Belted Type 

A belted-type generator consists of a generator with a shaft extension suitable for the driving pulley or 
sheave, with either two or three bearings as required, and with rails or with a sliding base which has 
provision for adjusting belt tension. 

1.62.2 Engine Type 

An engine-type generator consists of a field frame, armature (without shaft), foundation caps or sole 
plates (when required), and a brush rigging support. No base, bearings, shaft, shaft keys, or foundation 
bolts are included in generators of this type. 

1.62.3 Coupled Type 

A coupled-type generator consists of a generator with a shaft extension suitable for coupling, with either 
one or two bearings as required. 



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REFERENCED STANDARDS AND DEFINITIONS Part 1 , Page 25 



1 .63 FACE AND FLANGE MOUNTING 

1.63.1 Type C Face 

A Type C face-mounting machine has a male pilot (rabbet) fit with threaded holes in the mounting 
surface. The mounting surface shall be either internal or external to the pilot fit. (See Figure 4-3.) 

1.63.2 Type D Flange 

A Type D flange-mounting machine has a male pilot (rabbet) fit with clearance holes in the mounting 
surface. The mounting surface is external to the pilot fit. (See Figure 4-4.) 

1.63.3 Type P Flange 

A Type P flange-mounting machine has a female pilot (rabbet) fit with clearance holes in the mounting 
surface. The mounting surface is external to the pilot fit. (See Figure 4-5.) 

CLASSIFICATION OF INSULATION SYSTEMS 

1.65 INSULATION SYSTEM DEFINED 

An insulation system is an assembly of insulating materials in association with the conductors and the 
supporting structural parts. All of the components described below that are associated with the stationary 
winding constitute one insulation system and all of the components that are associated with the rotating 
winding constitute another insulation system. 

1.65.1 Coil Insulation with its Accessories 

The coil insulation comprises all of the insulating materials that envelop and separate the current-carrying 
conductors and their component turns and strands and form the insulation between them and the 
machine structure; including wire coatings, varnish, encapsulants, slot insulation, slot fillers, tapes, phase 
insulation, pole-body insulation, and retaining ring insulation when present. 

1 .65.2 Connection and Winding Support Insulation 

The connection and winding support insulation includes all of the insulation materials that envelop the 
connections, which carry current from coil to coil, and from stationary or rotating coil terminals to the 
points of external circuit attachment; and the insulation of any metallic supports for the winding. 

1.65.3 Associated Structural Parts 

The associated structural parts of the insulation system include items such as slot wedges, space blocks 
and ties used to position the coil ends and connections, any non-metallic supports for the winding, and 
field-coil flanges. 

1 .66 CLASSIFICATION OF INSULATION SYSTEMS 

Insulation systems are divided into classes according to the thermal endurance of the system for 
temperature rating purposes. Four classes of insulation systems are used in motors and generators, 
namely, Classes A, B, F, and H. These classes have been established in accordance with IEEE Std 1 . 

Insulation systems shall be classified as follows: 

Class A— An insulation system which, by experience or accepted test, can be shown to have suitable 
thermal endurance when operating at the limiting Class A temperature specified in the temperature rise 
standard for the machine under consideration. 

Class B — An insulation system which, by experience or accepted test, can be shown to have suitable 
thermal endurance when operating at the limiting Class B temperature specified in the temperature rise 
standard for the machine under consideration. 



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Class F — An insulation system which, by experience or accepted test, can be shown to have suitable 
thermal endurance when operating at the limiting Class F temperature specified in the temperature rise 
standard for the machine under consideration. 

Class H— An insulation system which, by experience or accepted test, can be shown to have suitable 
thermal endurance when operating at the limiting Class H temperature specified in the temperature rise 
standard for the machine under consideration. 

"Experience," as used in this standard, means successful operation for a long time under actual operating 
conditions of machines designed with temperature rise at or near the temperature rating limit. 

"Accepted test," as used in this standard, means a test on a system or model system which simulates the 
electrical, thermal, and mechanical stresses occurring in service. 

Where appropriate to the construction, tests shall be made in accordance with the following applicable 
IEEE test procedures: 
a. Std 43 
b.Std117 

c. Std 275 

d. Std 304 

For other constructions for which tests have not been standardized, similar procedures shall be permitted 
to be used if it is shown that they properly discriminate between service-proven systems known to be 
different. 

When evaluated by an accepted test, a new or modified insulation system shall be compared to an 
insulation system on which there has been substantial service experience. If a comparison is made on a 
system of the same class, the new system shall have equal or longer thermal endurance under the same 
test conditions; if the comparison is made with a system of a lower temperature class, it shall have equal 
or longer thermal endurance at an appropriately higher temperature. When comparing systems of 
different classes, an appropriate higher temperature shall be considered to be 25 degrees Celsius per 
class higher than the temperature for the base insulation system class. 

MISCELLANEOUS 

1 .70 NAMEPLATE MARKING 

A permanent marking of nameplate information shall appear on each machine, displayed in a readily 
visible location on the machine enclosure. 

1.70.1 Nameplate 

A permanent marking of nameplate information shall appear on each machine, displayed in a readily 
visible location on the machine enclosure. If the electric machine is so enclosed or incorporated in the 
equipment that its rating plate will not be easily legible, the manufacturer should, on request, supply a 
second rating plate to be mounted on the equipment. 

1.70.2 Additional Nameplate Markings 

In addition to the specific nameplate markings set forth in the various Parts for each particular size or type 
of machine, the following are examples of information that may also be included on a nameplate: 

a. Manufacturer's name, mark, or logo 

b. Manufacturer's plant location 

c. Manufacturer's machine code 

d. Manufacturer's model number or catalog number 



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e. Serial number or date of manufacture 

f. Enclosure or IP code (see Part 5) 

g. Method of cooling or IC code (see Part 6) 

h. Applicable rating and performance standard(s): e.g., NEMA MG 1 or IEC 60034-1 

i. Maximum momentary overspeed 

j. For ac machines, the rated power factor 

k. Maximum ambient if other than 40°C 

I. Minimum ambient temperature 

m. Maximum water temperature for water-air-cooled machines if greater than 25°C 

n. Altitude if greater than 3300 ft (1000 m) 

o. Connection diagram located near or inside the terminal box 

p. Approximate weight of the machine, if exceeding 66 lbs (30 kg) 

q. Direction of rotation for unidirectional machines, indicated by an arrow 

1.71 CODE LETTER 

A code letter is a letter which appears on the nameplate of an alternating-current motor to show its 
locked-rotor kVA per horsepower. The letter designations for locked rotor kVA per horsepower are given 
in 10.37. 

1 .72 THERMAL PROTECTOR 

A thermal protector is a protective device for assembly as an integral part of the machine and which, 
when properly applied, protects the machine against dangerous over-heating due to overload and, in a 
motor, failure to start. 

NOTE— The thermal protector may consist of one or more temperature sensing elements integral with the machine and 
a control device external to the machine. 

1.73 THERMALLY PROTECTED 

The words "thermally protected" appearing on the nameplate of a motor indicate that the motor is 
provided with a thermal protector. 

1.74 OVER TEMPERATURE PROTECTION 

For alternating-current medium motors, see 12.56. 

For direct-current medium motors, see 12.80. 

1 .75 PART-WINDING START MOTOR 

A part-winding start polyphase induction or synchronous motor is one in which certain specialty designed 
circuits of each phase of the primary winding are initially connected to the supply line. The remaining 
circuit or circuits of each phase are connected to the supply in parallel with initially connected circuits, at a 
predetermined point in the starting operation. (See 14.38.) 

1 .76 STAR (WYE) START, DELTA RUN MOTOR 

A star (wye) start, delta run polyphase induction or synchronous motor is one arranged for starting by 
connecting to the supply with the primary winding initially connected in star (wye), then reconnected in 
delta for running operation. 

1.77 CONSTANT FLUX 

Constant flux operation at any point occurs when the value of air gap magnetic flux is equal to the value 
which would exist at the base rating (i.e. rated voltage, frequency, and load). 



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1 .78 DEVIATION FACTOR 

The deviation factor of a wave is the ratio of the maximum difference between corresponding ordinates of 
the wave and of the equivalent sine wave to the maximum ordinate of the equivalent sine wave when the 
waves are superimposed in such a way as to make this maximum difference as small as possible. The 
equivalent sine wave is defined as having the same frequency and the same rms value as the wave being 
tested. 

1 .79 MARKING ABBREVIATIONS FOR MACHINES 

When abbreviations are used for markings which are attached to the motor or generator (rating plates, 
connection, etc.), they shall consist of capital letters because the conventional marking machines provide 
only numbers and capital letters and shall be in accordance with the following: 



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MG 1-2009 

REFERENCED STANDARDS AND DEFINITIONS 



Section 1 
Parti, Page 29 



Abbreviation 


Marking Indicated 


Abbreviation 


Marking Indicated 


A 


Ampere 


MAX 


Maximum 


AC 


Alternating-current 


MFD 


Microfarad 


AMB 


Ambient 


MG 


Motor-generator 


AO 


Air over 


MH 


Milihenry 


ARM 


Armature 


MHP 


Milihorsepower 


BB 


Ball bearing 


MIN 


Minimum 


BRG 


Bearing 


MIN 


Minute 


C 


Celsius (Centigrade) degrees 


MTR 


Motor 


CAP 


Capacitor 


NEMAorDES 


NEMA Design Letter 


CCW 


Counterclockwise 


NOor# 


Number 


CL 


Class or Classification 


OZ-FT 


Ounce-feet 


CODE 


Code Letter 


OZ-IN 


Ounce-inch 


CONN 


Connection 


PF 


Power factor 


CONT 


Continuous 


PH 


Phase, Phases or Number of Phases 


CFM 


Cubic feet per minute 


PM 


Permanent magnet 


COMM 


Commutating (interpole) 


RB 


Roller bearing 


COMP 


Compensating 


RECT 


Rectifier or rectified 


CPD 


Compound 


RES 


Resistance 


C/S 


Cycles per second 


RHEO 


Rheostat 


CW 


Clockwise 


RMS 


Root mean square 


DC 


Direct-current 


ROT 


Rotation 


DIAG 


Diagram 


RPM 


Revolutions per minute 


EFF 


Efficiency 


RTD 


Resistance temperature detector 


ENCL 


Enclosure 


SB 


Sleeve bearing 


EXC 


Exciter or Excitation 


SEC 


Second (time) 


F 


Fahrenheit, degrees 


SEC 


Secondary 


FF 


Form factor 


SER 


Serial or Serial number 


FHP 


Fractional horsepower 


SF 


Service factor 


FLA 


Full load amperes 


SFA 


Service factor amperes 


FLD 


Field 


SH 


Shunt 


FR 


Frame 


SPL 


Special 


FREQ 


Frequency 


STAB 


Stabilized or stabilizing 


GEN 


Generator 


STD 


Standard 


GPM 


Gallons per minute 


TACH 


Tachometer 


GPS 


Gallons per second 


TC 


Thermocouple 


H 


Henry 


TEMP 


Temperature 


HI 


High 


TEMP RISE 


Temperature rise 


HP 


Horsepower 


TERM 


Terminal 


HR 


Hour 


TH 


Thermometer 


HZ 


Hertz 


TIME 


Time rating 


IND 


Inductance or Induction 


TORQ 


Torque 


INS 


Insulation System Class 


TYPE 


Type 


KVA 


Kilovolt-ampere 


V 


Volt(s) or Voltage 


KVAR 


Reactive Kilovolt-ampere 


VA 


Volt-amperes 


KW 


Kilowatt 


VAR 


Reactive volt-amperes 


L* 


Line 


W 


Watt 


LB-FT 


Pound-feet 


WDG 


Winding 


LO 


Low 


WT 


Weight 


LRA 


Locked rotor amperes 






Shall be permitted to be used in conjunction with a 


number **Used in 


conjunction with a letter. 



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MG 1-2009 
Part 2 



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Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 2 
TERMINAL MARKINGS 

GENERAL 

2.1 LOCATION OF TERMINAL MARKINGS 

Terminal markings shall be placed on or directly adjacent to terminals to which connections must be 
made from outside circuits or from auxiliary devices which must be disconnected for shipment. Wherever 
specified, color coding shall be permitted to be used instead of the usual letter and numeral marking. 

2.2 TERMINAL MARKINGS 

A combination of capital letters or symbols and an Arabic numeral shall be used to indicate the character 

or function of the windings which are brought to the terminal. 

To prevent confusion with the numerals 1 and 0, the letters T and "O" shall not be used. 

The following letters and symbols shall be used for motors and generators and their auxiliary devices 

when they are included within or mounted on the machine: 

a. Armature - A1 , A2, A3, A4, etc. 

b. Alternating-current rotor windings (collector rings) 1 - M1, M2, M3, M4, etc. 

c. Control signal lead attached to commutating winding - C 

d. Dynamic braking resistor - BR1, BR2, BR3, BR4, etc. 

e. Field (series) - S1, S2, S3, S4, etc. 

f. Field (shunt) - F1 , F2, F3, F4, etc. 

g. Line-L1,L2, L3, L4, etc. 

h. Magnetizing winding (for initial and maintenance magnetization and demagnetization of 
permanent magnet fields) - E1 , E2, E3, E4, etc. 

NOTE — E1 , E3, or other odd-numbered terminals should be attached to the positive terminal of the magnetizing power supply for 
magnetization and to the negative terminal for demagnetization. 

k. Resistance (armature and miscellaneous) - R1 , R2, R3, R4, etc. 

I. Resistance 2 (shunt field adjusting) - V1 , V2, V3, V4, etc. 

m. Shunt braking resistor - DR1, DR2, DR3, DR4, etc. 

| n. Stator 1 - T1 , T2, T3, T4, etc.; U1 , U2, U3, U4, etc.; V1 , V2, V3, V4, etc.; W1 , W2, W3, W4, etc. 

o. Starting switch - K 

p. Thermal protector - P1 , P2, P3, P4, etc. 

q. Equalizing lead - = (equality sign) 

r. Neutral connection - Terminal letter with numeral 

s. AC brakes - BA1 , BA2, BA3, BA4, B1 , B2, B3, B4, etc. 

t. DC brakes - BD1, BD2, BD3, BD4, B1, B2, B3, B4, etc. 

u. Brush-wear detector - BW1 , BW2, BW3, BW4, etc. 

v. Capacitors - CA1, CA2, CA3, CA4, etc.; J1, J2, J3, J4, etc. 



1 For alternating-current machines only. 

2 For direct current machines only. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 2 TERMINAL MARKINGS 

w. Current transformer - CT1 , CT2, CT3, CT4, etc. 

x. Space Heaters - HE1, HE2, HE3, HE4, etc.; H1, H2, H3, H4 t etc. 

y. Lightning arrestor - LA1, LA2, LA3, LA4, etc. 

z. Potential transformer - PT1 , PT2, PT3, PT4, etc. 

aa. Resistance thermometer - RT1 , RT2, RT3, RT4, etc. 

bb. Surge capacitor- SC1, SC2, SC3, SC4, etc. 

cc. Surge protector- SP1, SP2, SP3, SP4, etc. 

dd. Switch, including plugging switch - SW1, SW2, SW3, SW4, etc. 

ee. Thermostat opening on increase of temperature - TB1, TB2, TB3, TB4, etc. 

ff. Thermocouple - TC1 , TC2, TC3, TC4, etc. 

gg. Thermostat closing on increase of temperature - TM1, TM2, TM3, TM4, etc. 

hh. Thermistor with negative temperature coefficient - TN1 , TN2, TN3, TN4, etc. 

ii. Thermistor with positive temperature coefficient - TP1 , TP2, TP3, TP4, etc. 

For the significance of the Arabic numeral, see 2.10 for direct-current machines, 2.20 for alternating- 
current machines, and 2.67 for auxiliary devices. 

2.3 DIRECTION OF ROTATION 

2.3.1 Alternating-Current Machines 

See 2.24. 

2.3.2 Direct-Current Machines 

See 2.12. 

2.3.3 Motor-Generator Sets 

When one motor and one generator are coupled together at their drive ends, the standard direction of 
rotation for both machines shall be as given for that type of machine and will apply to the motor generator 
set without a change in connections. 

The correct direction of rotation shall be clearly indicated on a motor-generator set. 

When two or more machines are coupled together but not at their drive ends, the standard direction of 
rotation cannot apply to all machines in the set. Changes in connections will be necessary for those 
machines operating in the opposite direction of rotation. 

DC MOTORS AND GENERATORS 

2.10 TERMINAL MARKINGS 

2.10.1 General 

The markings comprising letters and numbers on the terminals of a direct-current machine shall indicate 
the relation of circuits within the machine. 

2.10.2 Armature Leads 

When an armature lead passes through the commutating or compensating field, or any combination of 
these fields, before being brought out for connection to the external circuit, the terminal marking of this 
lead shall be an "A." When an armature lead passes through a series field and all internal connections 
are permanently made, the lead brought out shall be marked with an appropriate "S" designation. If an 
equalizer lead for paralleling purposes is brought out, it shall be marked with an = (equality sign). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 3 

2.10.3 Armature Leads— Direction of Rotation 

All numerals shall be determined on the following fundamental basis, the numerals of all the terminals of 
direct-current machines shall be selected so that when the direction of current in any single excitation 
winding is from a lower to a higher numeral, the voltage generated (counter electromotive force in a 
motor) in the armature from this excitation shall, for counterclockwise rotation facing the end opposite the 
drive, make armature terminal A1 positive and A2 negative. With excitation applied in the same manner, 
the opposite rotation wilt result in A2 being positive and A1 negative. 

2.11 TERMINAL MARKINGS FOR DUAL VOLTAGE SHUNT FIELDS 

When a separately excited shunt field winding is reconnectable series-parallel for dual voltage, the 
terminal markings shall be as shown in Figure 2-1. 

F1 F2 F3 F4 

c o o o 

I 



i T I 

.immm__! i qoooooooq I 



Figure 2-1 
SEPARATELY EXCITED SHUNT FIELD WINDING FOR SERIES-PARALLEL DUAL VOLTAGE 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 4 TERMINAL MARKINGS 



Voltage Join Connect to Supply 

Low (F1,F3)(F2, F4) 

High (F2, F3) (F1,F4) 

2.12 DIRECTION OF ROTATION 

2.12.1 Direct-Current Motors 

The standard direction of shaft rotation for direct-current motors shall be counterclockwise facing the end 
opposite the drive end. 

The direction of shaft rotation of direct-current motors depends on the relative polarities of the field and 
armature and, therefore, if the polarities of both are reversed, the direction of rotation will be unchanged. 
Since the field excitation of direct-current motors is obtained from an external source, residual magnetism 
has no practical effect on polarity except for those with permanent magnet excitation. Reversal of the 
shaft rotation of a direct-current motor is obtained by a transposition of the two armature leads or by a 
transposition of the field leads. With such reversed shaft rotation (clockwise) and when the polarity of the 
power supply is such that the direction of the current in the armature is from terminal 2 to terminal 1 , the 
current will be flowing in the field windings from terminal 1 to terminal 2, and vice versa. 

2.1 2.2 Direct-Current Generators 

The standard direction of shaft rotation for direct-current generators shall be clockwise facing the end 
opposite the drive end. 

The direction of rotation of a generator mounted as a part of an engine-generator set is usually 
counterclockwise facing the end opposite the drive end. 

Self-excited direct-current generators, with connections properly made for standard direction of shaft 
rotation (clockwise), will not function if driven counterclockwise as any small current delivered by the 
armature tends to demagnetize the fields and thus prevent the armature from delivering current. If the 
conditions call for reversed direction of shaft rotation, connections should be made with either the 
armature leads transposed or the field leads transposed. The polarity of a self-excited direct-current 
generator, with accompanying direction of current flow in the several windings, is determined by the 
polarity of the residual magnetism. An accidental or unusual manipulation may reverse this magnetic 
polarity. Though the generator itself will function as well with either polarity, an unforeseen change may 
cause disturbance or damage to other generators or devices when the generator is connected to them. 

2.12.3 Reverse Function 

A direct-current machine can be used either as a generator or as a motor if the field design is suitable for 
such operation. (The manufacturer should be consulted regarding this.) For the desired direction of 
rotation, connection changes may be necessary. The conventions for current flow in combination with the 
standardization of opposite directions of rotation for direct current generators and direct-current motors 
are such that any direct-current machine can be called "generator' or "motor" without a change in terminal 
markings. 

2.13 CONNECTION DIAGRAMS WITH TERMINAL MARKINGS FOR DIRECT-CURRENT MOTORS 

The connection diagrams with terminal markings for direct-current motors shall be as shown in Figures 2- 
2 through 2-9. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 5 



-nnrr\ 




A2 F2 



Figure 2-2 

SHUNT MOTOR— COUNTERCLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

CLOCKWISE ROTATION FACING DRIVE END 



■t' 



SHUNT 
FIELD 






"w^COMP 

1 FIELD 
1 


COMM 
FIELD 




1 
+ 1 


|M n 


_ _ 



A2 



A1 F2 



Figure 2-3 

SHUNT MOTOR— CLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

COUNTERCLOCKWISE ROTATION FACING DRIVE END 



F1 



O 

LU 

I 



i 



/YYY\. 
SHUNT 
FIELD 



COMP 
FIELD 



COMM 
FIELD 



SERIES 
FIELD 



A1 



A2 



S1 



S2 F2 



Figure 2-4 
COMPOUND OR STABILIZED SHUNT MOTOR— COUNTERCLOCKWISE ROTATION FACING 
END OPPOSITE DRIVE END, CLOCKWISE ROTATION FACING DRIVE END 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 6 

F1 



O 

LU 

I 



I 



Section I 
TERMINAL MARKINGS 



/YYY\ 

SHUNT 
FIELD 



K> 



A2 



COMM 
FIELD 



COMP 
FIELD 



SERIES 
FIELD 



A1 



S1 



S2 F2 



Figure 2-5 

COMPOUND OR STABILIZED SHUNT MOTOR— CLOCKWISE ROTATION FACING END OPPOSITE 

DRIVE END, COUNTERCLOCKWISE ROTATION FACING DRIVE END 



COMP 
FIELD 



COMM 
FIELD 



A1 



A2 



SERIES 
FIELD 



S1 



S2 



Figure 2-6 

SERIES MOTOR— COUNTERCLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

CLOCKWISE ROTATION FACING DRIVE END 



COMP 
FIELD 



COMM 
FIELD 



A2 



A1 



SERIES 
FIELD 



S1 



S2 



Figure 2-7 

SERIES MOTOR— CLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, COUNTER 

CLOCKWISE ROTATION FACING DRIVE END 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 7 



O 



A1 



A2 



Figure 2-8* 

PERMANENT MAGNET MOTOR— COUNTERCLOCKWISE ROTATION FACING END OPPOSITE 

DRIVE END, CLOCKWISE ROTATION FACING DRIVE END 

'When magnetizing windings are provided, see 2.2. 



o 



A2 



A1 



Figure 2-9* 

PERMANENT MAGNET MOTOR— CLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

COUNTERCLOCKWISE ROTATION FACING DRIVE END 

*When magnetizing windings are provided, see 2.2. 

When connections between different windings are made permanently inside the machine, any lead 
brought out of the machine from the junction (except a control lead) shall bear the terminal markings of all 
windings to which it is connected except that no markings shall be included for commutating and 
compensating fields. 

These connection diagrams show all leads from the armature, the shunt field, and the series (or 
stabilizing) field brought out of the machines. The same diagram is, therefore, applicable for reversing the 
nonrevers j n g motors. The dotted connections may be made inside the machine or outside the machine 
as conditions require. The relationship between the terminal marking numbers, the relative polarity of the 
windings, and the direction of rotation is in accordance with 2.12, but the polarities shown in these 
connection diagrams, while preferred, are not standardized. 

NOTES 

1— See 2.2 for terminal letters assigned to different types of windings and 2.10.3 for the significance of the numerals. 

2— The connections shown are for cumulative series fields. Differential connection of the series field in direct-current 
motors is very seldom used but when required, no change should be made on the field leads or terminal markings on 
the machine, but the connection of the series field to the armature should be shown reversed. 

3— Commutating, compensating, and series field windings are shown on the A1 side of the armature but this location 
while preferred, is not standardized. If sound engineering, sound economics, or convenience so dictates, these 
windings may be connected on either side of the armature or may be divided part on one side and part on the other. 

4— For shunt-wound, stabilized-shunt-wound, and compound-wound motors, the shunt field may be either connected in 
parallel with the armature as shown by the dotted lines or may be separately excited. When separately excited, the 
shunt field is usually isolated from the other windings of the machine, but the polarity of the voltage applied to the 
shunt field should be as shown for the particular rotation and armature and series field polarities. 

5— When the compensation field or both the commutating and the compensating fields are omitted from any machine, 
the terminal markings do not change. 

6— The lead designated by C, if used, is for control purposes and would not be used in any machine which has neither 
commutating nor compensating fields. In utilizing this terminal, the location of the commutating or compensating field 
should be known. See Note 3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 8 TERMINAL MARKINGS 

7— The position of the field rheostat shown in these diagrams does not indicate any preference. The field rheostat may 
be attached to either terminal of the shunt field. 

2.14 CONNECTION DIAGRAMS WITH TERMINAL MARKINGS FOR DIRECT-CURRENT 
GENERATORS 

The connection diagrams with terminal markings for direct-current generators shall be as shown in 
Figures 2-10 through 2-13. 

When connections between different windings are made permanently inside the machine, any lead 
brought out of the machine from the junction (except an equalizer or control lead) shall bear the terminal 
markings of all windings to which it is connected except that no markings shall be included for 
commutating and compensating fields. 

These connection diagrams show all leads from the armature, the shunt field, and the series field brought 
out of the machines. The dotted connections may be made inside the machine or outside the machine as 
conditions require. The relationship between the terminal marking numbers, the relative polarity of the 
windings, and the direction of rotation is in accordance with 2.12, but the polarities shown in these 
connection diagrams, while preferred, are not standardized. 

NOTES 

1— See 2.2 for terminal letters assigned to different types of windings and 2.10.3 for the numerals. 

2— The connections shown are for cumulative series fields. For differential connection of the series fields, no change 
should be made on the field leads or terminal markings on the machine, but the connection of the series field to the 
armature should be shown reversed. 

3— Commutating, compensating, and series field windings are shown on the A1 side of the armature, but this location, 
while preferred, is not standardized. If sound engineering, sound economics, or convenience so dictates, these 
windings may be connected on either side of the armature or may be divided part on one side and part on the other. 

4— Figures 2-12 and 2-13 show the shunt field connected either inside or outside the series field. Either may be used 
depending upon the desired characteristics. 

5— For shunt-wound generators and compound-wound generators, the shunt-field may be either self-excited or 
separately excited. When self-excited, connections should be made as shown by the dotted lines. When separately 
excited, the shunt field is usually isolated from the other windings of the machine, but the polarity or the voltage 
applied to the shunt field should be as shown for the particular rotation and armature polarity. 

6— When the compensating field or commutating field, or both, and the compensating fields are omitted from any 
machine, the terminal markings do not change. 

7— The terminal designated by C, if used, is for control purposes and would not be used in any machine which has 
neither commutating nor compensating fields. In utilizing this terminal, the location of the commutating or 
compensating field should be known. See Note 3. 

8— The position of the field rheostat shown in these diagrams does not indicate any preference. The field rheostat may 
be attached to either terminal of the shunt field. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 9 



F1 



O 

LU 

X 






SHUNT 
FIELD 



-- + 
A2 



I 
I 
I 
I 
C 



COMM 
FIELD 



COMP 
FIELD 



A1 F2 



Figure 2-10 

SHUNT GENERATOR— CLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 
COUNTERCLOCKWISE ROTATION FACING DRIVE END 




A2 F2 



Figure 2-11 
SHUNT GENERATOR— COUNTERCLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

CLOCKWISE ROTATION FACING DRIVE END 



F1 



Ol 
Ui ■ 
X ■ 

ttl 



_TYVW 

SHUNT 
FIELD 



F2 



COMP 
FIELD 



COMP 
FIELD 



I TT 



A1 



A2 



SERIES 
FIELD 



I S2 S1 

= (EQUALIZER IF USED) 

Figure 2-12 

COMPOUND GENERATOR— CLOCKWISE ROTATION FACING END OPPOSITE DRIVE END, 

COUNTERCLOCKWISE ROTATION FACING DRIVE END 



) Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 10 

F1 



Section I 
TERMINAL MARKINGS 



/YYY\ 
SHUNT 
FIELD 



F2 



O I 

Si 

£ I 



COMP 
FIELD 



COMM 
FIELD 



A1 



A2 



SERIES 
FIELD 



"T - 

I S2 S1 

= (EQUALIZER IF USED) 



Figure 2-13 

COMPOUND GENERATOR— COUNTERCLOCKWISE ROTATION FACING END OPPOSITE DRIVE 

END, CLOCKWISE ROTATION FACING DRIVE END 

AC MOTORS AND GENERATORS 

2.20 NUMERALS ON TERMINALS OF ALTERNATING-CURRENT POLYPHASE MACHINES 

2.20.1 Synchronous Machines 

The numerals 1, 2, 3, etc., indicate the order in which the voltages at the terminals reach their maximum 
positive values (phase sequence) with clockwise shaft rotation when facing the connection end of the coil 
windings; hence, for counterclockwise shaft rotation (not standard) when facing the same end, the phase 
sequence will be 1, 3, 2. 

2.20.2 Induction Machines 

The numerals 1, 2, 3, etc. used for terminal markings of polyphase induction machines do not define a 
relationship between the phase sequence, the connection end of the coil windings, and the direction of 
shaft rotation. 

2.21 DEFINITION OF PHASE SEQUENCE 

Phase sequence is the order in which the voltages successively reach their maximum positive values 
between terminals. 

2.22 PHASE SEQUENCE 

The order of numerals on terminal leads does not necessarily indicate the phase sequence, but the 
phase sequence is determined by the direction of shaft rotation relative to the connection end of the coil 
winding. 

2.23 DIRECTION OF ROTATION OF PHASORS 

Phasor diagrams shall be shown so that advance in phase of one phasor with respect to another is in the 
counter-clockwise direction. See Figure 2-14 in which phasor 1 is 120 degrees in advance of phasor 2 
and the phase sequence is 1, 2, 3. (See 2.21) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 1 1 




Figure 2-14 
ROTATION OF PHASORS 

2.24 DIRECTION OF ROTATION 

The standard direction of rotation for all alternating-current single-phase generators, all synchronous 
generators, and all universal generators shall be clockwise when facing the end of the machine opposite 
the drive end. 

The direction of rotation of a generator mounted as a part of an engine-generator set is usually 
counterclockwise when facing the end opposite the drive end. 

The standard direction of rotation for all alternating-current single-phase motors, all synchronous motors, 
and all universal motors shall be counterclockwise when facing the end of the machine opposite the drive 
end. 

The standard direction of rotation for polyphase induction motors and generators, when only the terminal 
markings U, V, W are used, in accordance with 2.60.1 .2 and are connected to L1, L2, and L3 respectively 
shall be counterclockwise when facing the end opposite the drive end, unless otherwise marked on the 
machine. No direction of rotation is defined when terminal markings T1, T2, T3 are used, either alone or 
in addition to the markings U, V, W. 

CAUTION - In some cases where field modification of the lead location of polyphase induction machines 
is required (i.e. from F1 to F2 mounting), it may be necessary to retag the leads with proper terminal 
markings, replace the leads for proper terminal markings, or otherwise mark the machine with the 
direction of rotation. 

AC GENERATORS AND SYNCHRONOUS MOTORS 

2.25 REVERSAL OF ROTATION, POLARITY AND PHASE SEQUENCE 

Alternating-current generators driven counterclockwise when facing the connection end of the coil 
windings will generate without change in connections, but the terminal phase sequence will be 1, 3, 2. 

Synchronous condensers and synchronous motors may be operated with counterclockwise shaft rotation 
viewed from the connection end of the coil windings by connecting them to leads in which the phase 
sequence is 1, 2, 3, in the following manner: 

a. Power leads 1, 2, 3 

b. Machine terminals 1, 3, 2 

2.30 CONNECTIONS AND TERMINAL MARKINGS-ALTERNATING— CURRENT GENERATORS 
AND SYNCHRONOUS MOTORS— THREE-PHASE AND SINGLE-PHASE 

The alternating-current windings of three-phase alternating-current generators and synchronous motors 
shall have terminal markings as given in 2.61 for three-phase single-speed induction motors. 

The alternating-current windings of single-phase alternating-current generators and synchronous motors 
shall have terminal markings as given in Figure 2-15. 

The terminal markings of direct-current field windings shall be F1 and F2. 

NOTE— See 2.2 for terminal tetters assigned to different types of windings and 2.20 for the significance of the numerals. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 12 



Section I 
TERMINAL MARKINGS 



F1 



F2 




T1 



■T2 



Figure 2-15 
SINGLE-PHASE 



SINGLE-PHASE MOTORS 

2.40 GENERAL 
2.40.1 Dual Voltage 

Regardless of type, when a single-phase motor is reconnectible series-parallel for dual voltage, the 

terminal marking shall be determined as follows. 

For the purpose of assigning terminal markings, the main winding is assumed to be divided into two 

halves, and T1 and T2 shall be assigned to one half and T3 and T4 to the other half. 

For the purpose of assigning terminal markings, the auxiliary winding (if present) is assumed to be 

divided into two halves, and T5 and T6 shall be assigned to one half and T7 and T8 to the other half. 

Polarities shall be established so that the standard direction of rotation (counterclockwise facing the end 

opposite the drive end) is obtained when the main winding terminal T4 and the auxiliary winding terminal 

T5 are joined or when an equivalent circuit connection is made between the main and auxiliary winding. 

The terminal marking arrangement is shown diagrammaticaliy in Figure 2-16. 

T1 T2 T3 T4 



uu 
O 



E 



T8 

T7 
T6 

T5 



Figure 2-16 
DUAL VOLTAGE 

2.40.2 Single Voltage 

If a single-phase motor is single voltage or if either winding is intended for only one voltage, the terminal 

marking shall be determined as follows. 

T1 and T4 shall be assigned to the main winding and T5 and T8 to the auxiliary winding (if present) with 

the polarity arrangement such that the standard direction of rotation is obtained if T4 and T5 are joined to 

one line and T1 and T8 to the other. 

The terminal marking arrangement is shown diagrammaticaliy in Figure 2-17. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 13 

NOTES 

1— It has been found to be impracticable to follow this standard for the terminal markings of some definite-purpose 

motors. See Part 18. 

2— No general standards have been developed for terminal markings of multispeed motors because of the great 
variety of methods employed to obtain multiple speeds. 

T1 T4 



u 




T8 
T5 

Figure 2-17 
SINGLE VOLTAGE 

2.41 TERMINAL MARKINGS IDENTIFIED BY COLOR 

When single-phase motors use lead colors instead of letter and number markings to identify the leads, 
the color assignment shall be determined from the following: 

a. T1 -Blue 

b. T2- White 

c. T3 - Orange 

d. T4- Yellow 

e. T5- Black 

f. T8-Red 

g. P1 - No color assigned 

h. P2 - Brown 

NOTE— It has been found to be impracticable to follow this standard for the lead markings of some definite-purpose 
motors. See Part 18. 

2.42 AUXILIARY DEVICES WITHIN MOTOR 

The presence of an auxiliary device or devices, such as a capacitor, starting switch, thermal protector, 

etc., permanently connected in series between the motor terminal and the part of the winding to which it 

ultimately connects, shall not affect the marking unless a terminal is provided at the junction. 

Where a terminal is provided at the junction, the terminal marking of this junction shall be determined by 

the part of the winding to which it is connected. Any other terminals connected to this auxiliary device 

shall be identified by a letter indicating the auxiliary device within the motor to which the terminal is 

connected. 

2.43 AUXILIARY DEVICES EXTERNAL TO MOTOR 

Where the capacitors, resistors, inductors, transformers, or other auxiliary devices are housed separately 
from the motor, the terminal markings shall be those established for the device. 

2.44 MARKING OF RIGIDLY MOUNTED TERMINALS 

On a terminal board, the identification of rigidly mounted terminals shall be either by marking on the 
terminal board or by means of a diagram attached to the machine. When all windings are permanently 
connected to rigidly-mounted terminals, these terminals may be identified in accordance with the terminal 
markings specified in this publication. When windings are not permanently attached to rigidly mounted 
terminals on a terminal board, the rigidly mounted terminals shall be identified by numbers only, and the 
identification need not coincide with that of the terminal leads connected to the rigidly mounted terminals. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 14 TERMINAL MARKINGS 

2.45 INTERNAL AUXILIARY DEVICES PERMANENTLY CONNECTED TO RIGIDLY MOUNTED 
TERMINALS 

If the motor design is such that the starting switch, thermal protector, or other auxiliary device is 
permanently connected to a rigidly mounted terminal, some variation from the connection arrangements 
illustrated in 2.47 through 2.53 will be required. However, any variations shall be based on the provisions 
of 2.46. 

2.46 GENERAL PRINCIPLES FOR TERMINAL MARKINGS FOR SINGLE-PHASE MOTORS 

The terminal marking and connection procedure given in 2.40 through 2.45 and in the schematic 
diagrams which follow are based on the following principles. 

2.46.1 First Principle 

The main winding of a single-phase motor is designate by T1 , T2, T3, and T4 and the auxiliary winding by 
T5, T6, T7, and T8 to distinguish it from a quarter-phase motor which uses odd numbers for one phase 
and even numbers for the other phase. 

2.46.2 Second Principle 

By following the first principle, it follows that odd-to-odd numbered terminals of each winding are joined 
for lower voltage (parallel) connection and odd-to-even numbered terminals of each winding are joined for 
higher voltage (series) connection. 

2.46.3 Third Principle 

The rotor of a single-phase motor is represented by a circle, even though there are no external 
connections to it. It also serves to distinguish the single-phase motor schematic diagram from that of the 
quarter-phase motor in which the rotor is never represented. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 1 5 



-This page is intentionally left blank. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 25 



2.51 SCHEMATIC DIAGRAMS FOR UNIVERSAL MOTORS— SINGLE VOLTAGE 



NON-REVERSIBLE 




A1 



A2 



L1 TO A1 
L2TOA2 



Figure 2-44.a 



REVERSIBLE 






L1 


L2 


Join 


Counter- 
clockwise 
rotation 


A1 


S2 


A2.S1 


Clockwise 
rotation 


A1 


S1 


A2.S2 



Figure 2-44.b 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 26 



Section I 
TERMINAL MARKINGS 



2.52 SCHEMATIC DIAGRAMS FOR REPULSION, REPULSION-START INDUCTION, AND 
REPULSION-INDUCTION MOTORS 



Reversible by Shifting Brushes 

SINGLE VOLTAGE 




T1 

T4 




L1 TO T1 
L2 TO T4 

Figure 2-45.a 



DUAL VOLTAGE 

T1 

T2 

T3 



T4 



Figure 2-45.b 





L1 


L2 


Join 


Higher nameplate voltage 


T1 


T4 


T2.T3 


Lower nameplate voltage 


T1.T3 


T2.T4 



Single Voltage - Externally Reversible 

T1 

T4 



E> 



I l~ T5 



L1 



L2 



Counter- 
clockwise 
rotation 



T1 



T5 



Clockwise 
rotation 



T1 



T8 



Figure 2-46.a 




■T5 
"T1 

■T8 



Counter- 
clockwise 
rotation 



Clockwise 
rotation 



L1 



L2 



T1 



T5 



T1 



T8 



Figure 2-46.b 



Join 



T4.T8 



T4.T5 



Insulate 
T8 



T5 



» Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 27 



2.53 SHADED-POLE MOTORS - TWO SPEED 

WHITE 



L1 L2 Open 



Highspeed White Black Red 
BLACK Low Speed White Red Black 



RED 



o 



Figure 2-47 
POLYPHASE INDUCTION MOTORS 

2.60 GENERAL PRINCIPLES FOR TERMINAL MARKINGS FOR POLYPHASE INDUCTION 
MOTORS 

2.60.1 Method of Marking 

2.60.1.1 Terminal Markings Using "T" 

The markings of the terminals of a motor serve their purpose best if they indicate the electrical relations 
between the several circuits within the motor. The windings of a motor are seldom accessible, and the 
arrangement of the terminal numbers varies with the combinations of connections which are required. 
However, if a definite system of numbering is used, the marking of the terminals may be made to tell the 
exact relations of the windings within the motor. As far as practicable, 2.61 is formulated to embody such 
a system, which system employs as one of its fundamental points a clockwise rotating spiral with T1 at 
the outer end and finishing with the highest number at its inner end as a means for determining the 
sequence of the numerals. See Figure 2-48A. Such numbering of the terminals on polyphase induction 
motors does not imply standardization of the direction of rotation of the motor shaft. 

IT4 N 

^ ^ _ - - / 

Figure 2-48A 
CLOCKWISE ROTATING SPIRAL WITH T1 AT THE OUTER END 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 28 TERMINAL MARKINGS 

2.60.1.2 Terminal Markings in Accordance with IEC 60034-8 Using U, V, W 

When terminal markings are required to be in accordance with IEC 60034-8, they can be per 2.60.1.2 
instead, (for single speed only), or in addition to those as numbered in 2.60.1.1. The markings of the 
terminals of a motor serve their purpose best if they indicate the electrical relations between the several 
circuits within the motor. The windings of a motor are seldom accessible and the arrangement of the 
terminal numbers varies with the combinations of connections which are required. However, if a definite 
system of numbering is used the marking of the terminals may be made to tell the exact relations of the 
windings within the motor. As far as practicable, 2.60 is formulated to embody such a system, which 
system employs as one of its fundamental points a clockwise rotating spiral with U1 at the outer end 
followed by V1 and W1 and finishing with the highest number for W at its inner end as a means for 
determining the sequence of the numerals. See Figure 2-48B in contrast to terminal marking shown in 
Figure 2-48A. The numbering of the terminals on polyphase induction motors in accordance with IEC 
60034-8 does imply standardization of the direction of the rotation of the motor shaft as described in 2.24 
The terminal marking in Figure 2-48B can be appropriately substituted for those shown in Figure 2-48A, 
when used as described in Figures 2-49 through 2-57. 

Motors having three leads may be marked U, V, W with the numeral 1 omitted. 



U1 



_L» 



U2 ^ \ 



\ 



X U3 N N 

t * * W4 w- . 



[ 

i . |W2^ W3 



/ W4 ,V4 , . | 

W3 ^ / 



i | vv ^ W3 ' / 

^ " / 



FIGURE 2-48B 

CLOCKWISE ROTATING SPIRAL WITH U1 AT THE OUTER END, SAME AS 2-48A EXCEPT 
USING TERMINAL MARKINGS IN ACCORDANCE WITH IEC 60034-8. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

TERMINAL MARKINGS Part 2, Page 29 

2.60.2 Three-Phase, Two Speed Motors 

For three-phase motors having two synchronous speeds obtained from a reconnectible winding it is 
undesirable to adhere to the clockwise system of numbering for all terminals as this would cause the 
motor to run with clockwise shaft rotation on one speed and counterclockwise on the other speed if the 
power lines are connected to each set of terminals in the same sequence. This feature may be 
considered an advantage as a winding with part of its terminals following a clockwise sequence and part 
following a counterclockwise sequence can be recognized immediately as a two-speed motor with a 
reconnectible winding. 

2.60.3 Two-Phase Motors 

For two-phase motors, the terminal markings are such that all odd numbers are in one phase and all even 
numbers are in the other phase. The markings of all motors except those for two-speed motors using a 
single reconnectible winding are based, as are three-phase windings, on a clockwise spiral system of 
rotation in the sequence of terminal numbering. 

2.61 TERMINAL MARKINGS FOR THREE-PHASE SINGLE-SPEED INDUCTION MOTORS 

The terminal markings for three-phase single-speed induction motors shall be as shown in Figures 2-49, 
2-50, 2-51, and 2-52. These terminal markings were developed in accordance with the following 
procedure which shall be used in developing terminal markings for other combinations of motor stator 
circuits: 

2.61.1 First 

A schematic phasor diagram shall be drawn showing an inverted Y connection with the individual circuits 
in each phase arranged for series connection with correct polarity relation of circuits. The diagram for two 
circuits per phase, for example, is as shown in Figure 2-53. 

2.61.2 Second 

Starting with T1 or U1 at the outside and top of the diagram, the ends of the circuit shall be numbered 
consecutively in a clockwise direction proceeding on a spiral towards the center of the diagram. For two 
circuits per phase, for example, the terminals are marked as shown in Figure 2-48A or 2-48B. 

2.61.3 Third 

A schematic phasor diagram shall be drawn showing the particular interconnection of circuits for the 
motor under consideration, and the terminal markings determined in accordance with 2.61.1 and 2.61.2 
shall be arranged to give the correct polarity relation of circuits. For example, if the winding shown in 
Figure 2-48 A or 2-48B is to be connected with two circuits in multiple per phase, the diagram and 
markings shall be as shown in Figure 2-54. 

2.61.4 Fourth 

The highest numbers shall be dropped and only the lowest number shall be retained where two or more 
terminals are permanently connected together. For example, if the winding shown in Figure 2-54 is to 
have two circuits in each phase permanently connected together with three line leads and three neutral 
leads brought out, the terminal marking shall be as shown in Figure 2-55 or, if the winding shown in 
Figures 2-48A or 2-48B is to be arranged for either a series or a multiple connection with the neutral point 
brought out, the vector diagram and terminal markings shall be as shown in Figure 2-56. 

2.61.5 Fifth 

Where the ends of three coils are connected together to form a permanent neutral, the terminal markings 
of the three leads so connected shall be dropped. If the neutral point is brought out, it shall always be 
marked TO. See Figure 2-56. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 30 TERMINAL MARKINGS 

2.61.6 Sixth 

If a winding is to be delta-connected, the inverted Y diagram (Figure 2-53) shall be rotated 30 degrees 
counter-clockwise. T1 or U shall be assigned to the outer end of the top leg and the balance of the 
numbering in accordance with 2.60.1.1 and Figure 2-48A or in accordance with 2.60.1.2 and Figure 2- 
48B. A schematic delta shall then be constructed in which the T1 or U leg of the rotated Y becomes the 
right hand side of the delta, the T2 or V leg becomes the bottom (horizontal) side, and the T3 or W leg 
becomes the left side of the delta. 2.60.1.1 or 2.60.1.2 shall be applied insofar as it applies to a delta 
connection. See Figure 2-57. 

2.62 TERMINAL MARKINGS FOR Y- AND DELTA-CONNECTED DUAL VOLTAGE MOTORS 

Figures 2-49 through 2-52 illustrate the application of 2.61 in determining terminal markings of Y- and 
delta-connected dual-voltage motors. 

2.63 TERMINAL MARKINGS FOR THREE-PHASE TWO-SPEED SINGLE-WINDING INDUCTION 
MOTORS 

The general principles for terminal markings for polyphase induction motors given in 2.60.1.1 are not 
applicable to three-phase two-speed single-winding induction motors because, if followed and the 
terminals are connected in the same sequence, the direction of rotation at the two speeds will be 
different. 

2.64 TERMINAL MARKINGS FOR Y- AND DELTA-CONNECTED THREE-PHASE TWO-SPEED 
SINGLE-WINDING MOTORS 

The terminal markings for Y- and delta-connected three-phase two-speed single-winding three-phase 
induction motors shall be in accordance with Figures 2-58 through 2-62. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 

T1 T7 




Figure 2-49 
Y-CONNECTED, DUAL VOLTAGE 



MG 1-2009 
Part 2, Page 31 



T9/\t4 

7 ^ 



T8 T5 

Figure 2-51 
DELTA-CONNECTED, DUAL VOLTAGE 



Voltage 



Low 

High 



L1 



L2 



L3 



(T1 ] T6,T7)(T2,T4 J T8)(T3,T5J9) 
T1 T2 T3 



Join 



(T4,T7) (T5.T8) (T6J9) 



Voltage L1 L2 



L3 



Low (T1.T7) (T2.T8) (T3.T9) 
High I T1 T2 T3 



Join 



... (T4.T5J6) ... 
(T4J7) (T5.T8) (T6J9) 





Figure 2-50 

TERMINAL MARKINGS FOR THREE-PHASE 

DUAL-VOLTAGE SINGLE-SPEED INDUCTION 

MOTOR WITH PROTECTOR IN NEUTRAL 



T5 T2 

Figure 2-52 
-CONNECTED START, DELTA-CONNECTED 
RUN, SINGLE VOLTAGE 




L1 L2 L3 


Join 


Start 
Run 


T1 T2 T3 
(T1J6) (T2,T4) (T3.T5) 


(T4.T5.T6) 



Y-DELTA-CONNECTED, DUAL VOLTAGE 
(VOLTAGE RATIO -/3 TO 1) 



S \ 



\ 



Figure 2-53 
DIAGRAM FOR TWO CURCUITS PER PHASE 



i Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 32 



Section I 
TERMINAL MARKINGS 



T4 T10 
T9^0£_ _nNwT2 



T6 Tlf 
T3 T8 



■1>^> T: 



Figure 2-54 

TERMINAL MARKINGS FOR TWO 

CIRCUITS IN MULTIPLE PER PHASE 



T1 
T5. 



T3 T2 



Figure 2-55 

TERMINAL MARKINGS FOR TWO 

CIRCUITS IN MULTIPLE PER PHASE, 

PERMANENTLY CONNECTED 



T1 T7 




Figure 2-56 

TERMINAL MARKINGS WITH NEUTRAL POINT 

BROUGHT OUT 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 




tii\| T11 T8 T5 T2 

T12 



MG 1-2009 
Part 2, Page 33 



T12 T1 




T11 



T10 



T8 T5 



T2 



Figure 2-57 
TERMINAL MARKINGS FOR TWO CIRCUITS PER PHASE, DELTA CONNECTED 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 34 



Section I 
TERMINAL MARKINGS 





Figure 2-58 
VARIABLE TORQUE MOTORS 
FOR ONE OR MORE WINDINGS 



Figure 2-60 
CONSTANT TORQUE MOTORS FOR TWO OR 
MORE INDEPENDENT WINDINGS 



Speed 


L1 


L2 


L3 


Insulate 
Separately 


Join 


Low 

High 


T1 
T6 


T2 
T4 


T3 
T5 


T4-T5-T6 


(T1, T2, T3) 



Speed 


L1 


L2 


L3 


Insulate 
Separately 


Join 


Low 
High 


T1 

T6 


T2 
T4 


(T3. T7) 
T5 


T4-T5-T6 


(T1, T2, T3, T7) 





Figure 2-59 
CONSTANT TORQUE MOTORS FOR 
SINGLE WINDING ONLY 



Figure 2-61 
CONSTANT HORSEPOWER MOTORS FOR 
TWO OR MORE INDEPENDENT WINDINGS 



Speed 


L1 


L2 


L3 


Insulate 
Separately 


Join 


Low 
High 


T1 
T6 


T2 
T4 


T3 
T5 


T4-T5-T6 


(T1, T2, T3) 



Speed 


L1 


L2 


L3 


Insulate 
Separately 


Join 


Low 
High 


T1 
T6 


T2 
T4 


T3 

(T5, T7) 


T1-T2-T3 


(T4, T5, T6, T7) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 35 




Figure 2-62 
CONSTANT HORSEPOWER MOTORS FOR SINGLE WINDING ONLY 



Speed 


L1 


L2 


L3 


Insulate 
Separately 


Join 


Low 
High 


T1 
T6 


T2 
T4 


T3 

T5 


T1-T2-T3 


(T4, T5, T6) 



T1 




T13 




T21 




T17 



T12 



T23 



T22 



Speed 



Low 

Second 

High 



Figure 2-63 
THREE-SPEED MOTOR USING THREE WINDINGS 



L1 


L2 


T1 


T2 


T11 


T12 


T21 


T22 



L3 



T3 

(T13, T17) 

T23 



Insulate Separately 



T11-T12-T13-T17-T21-T22-T23 

T1-T2-T3-T21-T22-T23 

T1-T2-T3-T11-T12-T13-T17 



Join 



) Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 36 



Section I 
TERMINAL MARKINGS 




T14 



T15 




T16 



Figure 2-64 
FOUR-SPEED MOTOR USING TWO WINDINGS 



Speed 


L1 


L2 


L3 


Insulate Separately 


Join 


Low 


T1 


T2 


T3 


T4-T5-T6-T11-T12-T13-T14-T15-T16 




Second 


T11 


T12 


T13 


T1 -T2-T3-T4-T5-T6-T1 4-T1 5-T1 6 




Third 


T6 


T4 


T5 


T11-T12-T13-T14-T15-T16 


(T1, T2, T3) 


High 


T16 


T14 


T15 


T1-T2-T3-T4-T5-T6 


(T11, T12, T13) 



2.65 TERMINAL MARKINGS FOR THREE-PHASE INDUCTION MOTORS HAVING TWO OR MORE 
SYNCHRONOUS SPEEDS OBTAINED FROM TWO OR MORE INDEPENDENT WINDINGS 

2.65.1 Each Independent Winding Giving One Speed 

The winding giving the lowest speed shall take the same terminal markings as determined from 2.61 for 
the particular winding used. The terminal markings for the higher speed windings shall be obtained by 
adding 10, 20, or 30, etc., to the terminal markings as determined from 2.61 for the particular winding 
used, the sequences being determined by progressing each time to the next higher speed. The terminal 
markings for a three speed motor using three windings are given in Figure 2-63. 

2.65.2 Each Independent Winding Reconnectible to Give Two Synchronous Speeds 

2.65.2.1 First 

Phasor diagrams of the windings to be used shall be drawn and each winding given the terminal 
markings shown in accordance with Figures 2-58 through 2-60. The neutral terminal, if brouqht out shall 
be marked TO. 

2.65.2.2 Second 

No change shall be made in any of the terminal markings of the winding giving the lowest speed 
irrespective of whether the other speed obtained from this winding is an intermediate or the hiqhest 
speed. a 

2.65.2.3 Third 

Ten shall be added to all terminal markings of the winding giving the next higher speed, and an additional 
10 shall be added to all the terminal markings for each consecutively higher speed winding. An example 
of terminal markings for a four-speed motor using two windings are given in Figure 2-64. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 37 



2.65.3 Two or More Independent Windings at Least One of Which Gives One Synchronous Speed 
and the Other Winding Gives Two Synchronous Speeds 

2.65.3.1 First 

Each winding shall be given the markings determined in accordance with 2.65.2.1 . 

2.65.3.2 Second 

No change shall be made in any of the terminal markings of the winding giving the lowest speed. 

2.65.3.3 Third 

Ten shall be added to all terminal markings of the winding giving the next higher speed, and an additional 
10 shall be added to all the terminal markings for each consecutively higher speed winding. A typical 
marking for a three-speed motor using two windings where one of the windings is used for the high speed 
only is given in Figure 2-65. 

NOTES 

1— If, under any of the provisions of this standard, the addition of 10, 20, 30, etc. to the basic terminal markings 
causes a duplication of markings due to more than nine leads being brought out on any one winding, then 20, 40, 60, 
etc. should be added instead of 10, 20, 30, etc., to obtain the markings for the higher speeds. 

2— The illustrative figures in this standard apply when all leads are brought out on the same end of the motor. When 
one or more of the windings have some leads brought out on one end of the motor and some on the other end, the 
rotation of the terminal markings for leads brought out on one end may be shown on the diagram as shown in the 
illustrative figures, and the terminal markings for those brought out on the opposite end may be shown reversed in 
rotation. When diagrams use this reversed rotation of markings, an explanatory note should be included for the benefit 
of the control manufacturer and user to inform them that, when L1, L2, and L3 are connected to any winding with the 
same sequence of numbers (T1, T2, T3; or T4, T5, T6; orT11, T12, T13, etc.), the shaft rotation will be the same. 

T4 T11 





Figure 2-65 
THREE-SPEED MOTOR USING TWO WINDINGS 



Speed 


L1 


L2 


L3 


Insulate Separately 


Join 


Low 
Second 

High 


T1 
T6 

T11 


T2 
T4 
T12 


(T3, T7) 
T5 
T13 


T4-T5-T6-T11-T12-T13 

T11-T12-T13 

T1-T2-T3-T4-T5-T6-T7 


(T1,T2,T3,T7) 



) Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 38 



Section I 
TERMINAL MARKINGS 



2.66 TERMINAL MARKINGS OF THE ROTORS OF WOUND-ROTOR INDUCTION MOTORS 

See Figures 2-66 and 2-67. 






Figure 2-66 
THREE-PHASE WOUND ROTOR 



Figure 2-67 
TWO-PHASE WOUND ROTOR 



AUXILIARY DEVICES 

2.67 TERMINAL MARKINGS 

2.67.1 General 

All auxiliary devices with more than two terminals shall have connecting instructions. 
Each auxiliary circuit shall be assigned a letter symbol(s). 

2.67.2 Auxiliary terminal marking rules 

The marking of auxiliary terminals shall be according to 2.67.1, with 2.2 identifying the type of auxiliary 
device, together with 

- a numerical prefix identifying the individual circuit or device; 

- a numerical suffix identifying the lead function. 

The addition of letters and/or numbers to the auxiliary symbol shall wherever possible, be based on the 
rules given in 2.67.1. 

When there is a large number of terminals for a given type of device (e.g., thermocouples), the leads may 
be grouped by device code and the terminals identified by a prefix 1-99) and followed by a sinqle diqit 
suffix (1-9). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 39 



The manufacturer should identify the function of these devices in the written instructions. 

When only one device of a certain type exists, the prefix may be omitted. 

2.67.3 Examples of Marking 

2.67.3.1 Power related devices 

Devices such as BA, BD, BW, CA, DC, HE, LA, SC and SP shall be marked and connected in 
accordance with 2.67.3.1.1 to 2.67.3.1.4 where 



** indicates the device coding and I 1 represents the device. 

2.67.3.1 .1 Single-phase, single voltage 



** 1 



**2 



Figure 2-68 - Single-phase, single voltage 



kl 


L2 


**1 


**2 



2.67.3.1 .2 Single-phase, dual voltage 



**2 



"<k: 



-CZ3- 



**4 



Figure 2-69 - Single-phase dual voltage 



Voltage 


L1 


L2 


Join 


Isolate 


High 


**1 


**4 


- 


**2 


Low 


**1 


**2 


[**1, **4] 


- 



2.67.3.1 .3 Three-phase, single voltage 



"*T1 




*T1 



*T3 




*T2 



Figure 2-70 - Three-phase, single voltage 



L1 


L2 


L3 


Connection 


**T1 


**T2 


**T3 


Delta 



L1 


L2 


L3 


Connection 


**T1 


**T2 


**T3 


Y 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 2, Page 40 



Section I 
TERMINAL MARKINGS 



2.67.3.1.4 Three-phase, dual voltage 



*T1*T7 




Figure 2-71 
Y-CONNECTED, DUAL VOLTAGE 



Voltage 


L1 L2 L3 


Join 


Low 


(**T1 ,**T7) (**T2,**T8) (**T3,**T9) 


(**T4,**T5,**T6) 


High 


**T1 **T2 **T3 


(**T4,**T7) (**T5,**T8) 
(**T6,**T9) 



**T9/ \T4 

**T(y VT7 
*%ZL JTT2 



Figure 2-72 
DELTA-CONNECTED, DUAL VOLTAGE 



Voltage 


L1 L2 L3 


Join 


Low 


(**T1,**T6,**T7) (**T2,**T4,**T8) (**T3,**T5,**T9) 




High 


**T1 **T2 **T3 


(**T4,**T7) (**T5,**T8) 
(**T6,**T9) 



Alternate marking of U, V, W rather than T1 , T2, T3, etc. shall be in accordance with 2.60.1 .2. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

TERMINAL MARKINGS 



MG 1-2009 
Part 2, Page 41 



I 2.67.3.2 Thermal and measurement devices 



Devices CT, PT, RT, TB, TC, TN, TM and TP shall be marked and connected in accordance with 
2.67.3.2.1 to 2.67.3.2.3 where 



indicates the device coding and I 1 represents the device. 

NOTE: For TC devices, the leads are color coded by the manufacturer to denote polarity. 



2.67.3.2.1 Two-lead devices of types RT, TB, TC, TM, TN, and TP 



1**1 



> 



1**2 



2**1 



2**2 



Figure 2-73 - Two-lead devices 



2.67.3.2.2 Three-lead devices of type RT 



1RT1 




1RT2 


2RT1 




2RT2 




r> 




o 


o 


o — 

1%T2 


2%T2 



Figure 2-74 - Three-lead devices of type RT 

Terminal *RT1 is connected to the lead on one side of the measurement bridge. One terminal *RT2 is 
connected to center lead and the second terminal *RT2 is connected to the opposite side lead of the 
measurement bridge. 



2.67.3.2.3 Four-lead devices of type RT 



1RT1 
o 



1£I1_ 



1RT2 
— o 



2RT1 
o 



1&T2 



2£LL 



2RT2 
— o 



M 12 



Figure 2-75 - Four-lead devices of type RT 

The two terminals *RT1 are connected to leads on one side of the measurement bridge and the two 
terminals *RT2 are connected to leads on the opposite side of the measurement bridge. 

2.67.3.3 Switches 

Switches shall be marked as shown in Figure 2-76 where * denotes the switch number. 

I *S1 
. o 



*S2 
o — 



Figure 2-76 - Switch connections 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 2, Page 42 TERMINAL MARKINGS 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 3 



<This page is intentionally left blank > 



Section I MG 1-2009 

HIGH-POTENTIAL TESTS Part 3, Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 3 
HIGH-POTENTIAL TESTS 

3.1 HIGH-POTENTIAL TESTS 

3.1.1 Safety 

WARNING: Because of the high voltages used, high potential tests should be conducted only by trained 
personnel, and adequate safety precautions should be taken to avoid injury to personnel and damage to 
property. Tested windings should be discharged carefully to avoid injury to personnel on contact. See 
2.10 in NEMA Publication No. MG 2. 

3.1.2 Definition 

High-potential tests are tests which consist of the application of a voltage higher than the rated voltage for 
a specified time for the purpose of determining the adequacy against breakdown of insulating materials 
and spacings under normal conditions. 

3.1.3 Procedure 

High-potential tests shall be made in accordance with the following applicable IEEE Publications: 

a. Std 112 

b. Std 113 

c. Std 114 

d. Std 115 

3.1.4 Test Voltage 

The high-potential test shall be made by applying a test voltage having the magnitude specified in the 
part of this publication that applies to the specific type of machine and rating being tested. 

The frequency of the test circuit shall be 50 to 60 hertz, 1 and the effective value of the test voltage shall 
be the crest value of the specified test voltage divided by the square root of two. The wave shape shall 
have a deviation factor not exceeding 0.1 . 

The dielectric test should be made with a dielectric tester which will maintain the specified voltage at the 
terminals during the test. 

3.1 .5 Condition of Machine to be Tested 

The winding being tested shall be completely assembled (see 3.1.10). The test voltage shall be applied 
when, and only when, the machine is in good condition and the insulation resistance is not impaired due 
to dirt or moisture. (See IEEE Std 43.) 

3.1 .6 Duration of Application of Test Voltage 

The specified high-potential test voltage shall be applied continuously for 1 minute. Machines for which 
the specified test voltage is 2500 volts or less shall be permitted to be tested for 1 second at a voltage 
which is 1.2 times the specified 1 -minute test voltage as an alternative to the 1 -minute test, if desired. 
To avoid excessive stressing of the insulation, repeated application of the high-potential test voltage is 
not recommended. 



1 A direct instead of an alternating voltage may be used for high-potential test. In such cases, a test voltage of 1.7 
times the specified alternating voltage (effective voltage) as designated in 12.3 is required. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 3, Page 2 HIGH-POTENTIAL TESTS 

3.1 .7 Points of Application of Test Voltage 

The high-potential test voltage shall be successively applied between each electric circuit and the frame 
or core. All other windings or electric circuits not under test and all external metal parts shall be 
connected to the frame or core. All leads of each winding, phase, or electric circuit shall be connected 
together, whether being tested or connected to the frame or core. 

An electric circuit consists of all windings and other live parts which are conductively connected to the 
same power supply or load bus when starting or running. A winding which may be connected to a 
separate power supply, transformer, or load bus any time during normal operation is considered to be a 
separate circuit and must be high-potential tested separately. For example, fields of direct-current 
machines shall be considered to be separate circuits unless they are permanently connected in the 
machine. Unless otherwise stated, interconnected polyphase windings are considered as one circuit and 
shall be permitted to be so tested. 

3.1.8 Accessories and Components 

All accessories such as surge capacitors, lightning arresters, current transformers, etc., which have leads 
connected to the rotating machine terminals shall be disconnected during the test, with the leads 
connected together and to the frame or core. These accessories shall have been subjected to the high- 
potential test applicable to the class of apparatus at their point of manufacture. Capacitors of capacitor- 
type motors must be left connected to the winding in the normal manner for machine operation (running 
or starting). 

i. Component devices and their circuits such as space heaters and temperature sensing devices in 
contact with the winding (thermostats, thermocouples, thermistors, resistance temperature 
detectors, etc.), connected other than in the line circuit, shall be connected to the frame or core 
during machine winding high-potential tests. Each of these component device circuits, with leads 
connected together, shall then be tested by applying a voltage between the circuit and the frame 
or core, equal to 1500 volts. During each device circuit test all other machine windings and 
components shall be connected together and to the frame or core. 
When conducting a high-potential test on an assembled brushless exciter and synchronous machine field 
winding, the brushless circuit components (diodes, thyristors, etc.) shall be short circuited (not grounded) 
during the test. 

3.1 .9 Evaluation of Dielectric Failure 

Insulation breakdown during the application of the high-potential test voltage shall be considered as 
evidence of dielectric failure, except that in the production testing of small motors dielectric failure shall be 
indicated by measurement of insulation resistance below a specified value (see 12.4). 

3.1.10 Initial Test at Destination 

When assembly of a winding is completed at the destination, thus precluding the possibility of making 
final high-potential tests at the factory, it is recommended that high-potential tests be made with the test 
voltages specified in the applicable section of this publication immediately after the final assembly and 
before the machine is put into service. The test voltage should be applied when, and only when, the 
machine is in good condition and the insulation resistance is not impaired due to dirt or moisture. (See 
IEEEStd43.) 

3.1 .1 1 Tests of an Assembled Group of Machines and Apparatus 

Repeated application of the foregoing test voltage is not recommended. When a motor is installed in 
other equipment immediately after manufacture and a high-potential test of the entire assembled motor 
and equipment is required, the test voltage shall not exceed 80 percent of the original test voltage or, 
when the motor and equipment are installed in an assembled group, the test voltage shall not exceed 80 
percent of the lowest test voltage specified for that group. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

HIGH-POTENTIAL TESTS Part 3, Page 3 

3.1.12 Additional Tests Made After Installation 

When a high-potential test is made after installation on a new machine which has previously passed its 
high-potential test at the factory and whose windings have not since been disturbed, the test voltage shall 
be 75 percent of the test voltage specified in the part of this publication that applies to the type of 
machine and rating being tested. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 3, Page 4 HIGH-POTENTIAL TESTS 



< This page is intentionally left blank. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4 



<This page is intentionally left blank > 



Section I MG 1_2009 

DIMENSIONS, TOLERANCES, AND MOUNTING Part 4, Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 4 
DIMENSIONS, TOLERANCES, AND MOUNTING 

4.1 LETTER SYMBOLS FOR DIMENSION SHEETS 

Dimensions shall be lettered in accordance with Table 4-1 . See also Figures 4-1 through 4-5. 

Any letter dimension normally applying to the drive end of the machine will, when prefixed with the letter 
F, apply to the end opposite the drive end. 

Letter dimensions other than those listed below used by individual manufacturers shall be designated by 
the prefix letter X followed by A, B, C, D, E, etc. 

Table 4-1 
LETTER SYMBOLS FOR DIMENSION SHEETS 

Dimension Indicated 



NEMA 


IEC 


Letter 


Letter 


A 


AB 


B 


BB 


C 


L 


D 


H 


E 




2E 


A 


2F 


B 


G 


HA 


H 


K 


J 


AA 


K 


BA 


N 




N-W 


E 





HC 


P 


AC 


R 


G 


S 


F 


T 


HD-HC 


T+O 


HD 



Overall dimension across feet of horizontal machine (end view) 

Overall dimension across feet of horizontal machine (side view) 

Overall length of single shaft extension machine (For overall length of double shaft extension 
machine, see letter dimension FC.) 

Centerline of shaft to bottom of feet 

Centerline of shaft to centerline of mounting holes in feet (end view) 

Distance between centerlines of mounting holes in feet or base of machine (end view) 

Distance between centerlines of mounting holes in feet or base of machine (side view) 

Thickness of mounting foot at H hole or slot 

Diameter of holes or width of slot in feet of machine 

Width of mounting foot at mounting surface 

Length of mounting foot at mounting surface 

Length of shaft from end of housing to end of shaft, drive end 

Length of the shaft extension from the shoulder at drive end 

Top of horizontal machine to bottom of feet 

Maximum width of machine (end view) including pole bells, fins, etc., but excluding terminal 

housing, lifting devices, feet, and outside diameter of face or flange 

Bottom of keyseat or flat to bottom side of shaft or bore 

Width of keyseat 

Height of lifting eye, terminal box, or other salient part above the surface of the machine. 

Distance from the top of the lifting eye, the terminal box or other most salient part mounted on the 
top of the machine to the bottom of the feet 

U D Diameter of shaft extension. (For tapered shaft, this is diameter at a distance V from the threaded 

portion of the shaft.) 

U-R GE Depth of the keyway at the crown of the shaft extension at drive end 

V ... Length of shaft available for coupling, pinion, or pulley hub, drive end. (On a straight shaft 

extension, this is a minimum value.) 

W ... For straight and tapered shaft, end of housing to shoulder. (For shaft extensions without shoulders, 

it is a clearance to allow for all manufacturing variations in parts and assembly.) 
X Length of hub of pinion when using full length of taper, drive end 

Y ... Distance from end of shaft to outer end of taper, drive end 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 4, Page 2 DIMENSIONS, TOLERANCES, AND MOUNTING 

Table 4-1 (Continued) 
LETTER SYMBOLS FOR DIMENSION SHEETS 



NEMA IEC 

Letter Letter Dimension Indicated 



z 




AA 




AB 


AD 


AC 




AD 




AE 




AF 




AG 


LB 


AH 


E+R 


AJ 


M 


AK 


N 


AL 




AM 




AN 




AO 




AP 




AR 




AT 




AU 




AV 




AW 




AX 




AY 




AZ 




BA 


C 


BB 


T 


BC 


R 


BD 


P 


BE 


LA 


BF 


S 


BH 




BJ 




BK 




BL 




BM 




BN 




BO 




BP 





Width across corners of nut or diameter of washer, or tapered shaft, drive end 

Threaded or clearance hole for external conduit entrance (expressed in conduit size) to terminal 

housing 

Centerline of shaft to extreme outside part of terminal housing (end view) 

Centerline of shaft to centerline of hole AA in terminal housing (end view) 

Centerline of terminal housing mounting to centerline of hole AA (side view) 

Centerline of terminal housing mounting to bottom of feet (end view) 

Centerline of terminal housing mounting to hole AA (end view) 

Mounting surface of face, flange, or base of machine to opposite end of housing (side view) 

Mounting surface of face, flange, or base of machine to end of shaft 

Diameter of mounting bolt circle in face, flange, or base of machine 

Diameter of male or female pilot on face, flange, or base of machine 

Overall length of sliding base or rail 

Overall width of sliding base or outside dimensions of rails 

Distance from centerline of machine to bottom of sliding base or rails 

Centerline of sliding base or rail to centerline of mounting bolt holes (end view) 

Centerline of sliding base or rails to centerline of inner mounting bolt holes (motor end view) 

Distance between centerlines of mounting holes in sliding base or distance between centerlines of 

rail mounting bolt holes (side view) 

Thickness of sliding base or rail foot 

Size of mounting holes in sliding base or rail 

Bottom of sliding base or rail to top of horizontal machine 

Centerline of rail or base mounting hole to centerline of adjacent motor mounting bolt 

Height of sliding base or rail 

Maximum extension of sliding base (or rail) adjusting screw 

Width of slide rail 

Centerline of mounting hole in nearest foot to the shoulder on drive end shaft (For machines 

without a shaft shoulder, it is the centerline of mounting hole in nearest foot to the housing side of 

N-W dimension.) 

Depth of male or female pilot of mounting face, flange, or base of machine 

Distance between mounting surface of face, flange, or base of machine to shoulder on shaft. (For 

machine without a shaft shoulder, it is the distance between the mounting surface of face, flange, 

or base of machine to housing side of N-W dimension) 

Outside diameter of mounting face, flange or base of machine 

Thickness of mounting flange or base of machine 

Threaded or clearance hole in mounting face, flange, or base of machine 

Outside diameter of core or shell (side view) 

Overall length of coils (side view). Actual dimensions shall be permitted to be less depending on 

the number of poles and winding construction 

Distance from centerline of stator to lead end of coils 

Diameter over coils, both ends (BL = two times maximum radius) 

Overall length of stator shell 

Diameter of stator bore 

Length of rotor at bore 

Length of rotor over fans 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTING Part 4, Page 3 

Table 4-1 {Continued) 
LETTER SYMBOLS FOR DIMENSION SHEETS 

Dimension Indicated 

Diameter of finished surface or collar at ends of rotor 

Centerline of foot mounting hole, shaft end, to centerline of terminal housing mounting (side view) 

Movement of horizontal motor on base or rail 

Angle between centerline of terminal housing mounting and reference centerline of motor (end 

view) 

Centerline of terminal housing mounting to mounting surface of face or flange (side view) 

Inside diameter of rotor fan or end ring for shell-type and hermetic motors 

Diameter of bore in top drive coupling for hollow-shaft vertical motor 

Diameter of mounting holes in top drive coupling for hollow-shaft vertical motor 

Diameter of bolt circle for mounting holes in top drive coupling for hollow-shaft vertical motor 

Rotor bore diameter 

Rotor counterbore diameter 

Depth of rotor counterbore 

Distance from the top coupling to the bottom of the base on Type P vertical motors. 

Overall diameter of mounting lugs 

Distance from the end of the stator shell to the end of the motor quill at compressor end. Where 

either the shell or quill is omitted, the dimension refers to the driven load end of the core. 

Distance from the end of the stator shell to the end of the stator coil at compressor end. 

Distance from the end of the stator shell to the end of the stator coil at end opposite the 

compressor. 

Distance between clamp-bolt centers for two-hole clamping of universal motor stator cores. 

Clearance hole for maximum size of clamp bolts for clamping universal motor stator cores. 

Outside diameter of rotor core. 

Distance from the end of stator shell (driven load end) to the end of rotor fan or end ring (driven 

load end). Where the shell is omitted, the dimensions is to the driven load end of the stator core. 
DD ... Distance from the end of stator shell (driven load end) to the end of rotor fan or end ring (driven 

load end). Where the shell is omitted, the dimension is to the driven load end of the stator core. 
DE ... Diameter inside coils, both ends (DE = 2 times minimum radius). 

DF ... Distance from driven load end of stator core or shell to centerline of mounting hole in lead clip or 

end of lead if no clip is used. 
DG ... Distance from driven load end of stator core or shell to end of stator coil (opposite driven load 

end). 
DH ... Centerline of foot mounting hole (shaft end) to centerline of secondary terminal housing mounting 

(side view). 
DJ ... Centerline of secondary lead terminal housing inlet to bottom of feet (horizontal). 

DK ... Center of machine to centerline of hole "DM" for secondary lead conduit entrance (end view). 

DL ... Centerline of secondary lead terminal housing inlet to entrance for conduit. 

DM ... Diameter of conduit (pipe size) for secondary lead terminal housing. 

DN ... Distance from the end of stator shell to the bottom of rotor counterbore (driven load end). Where 

the shell is omitted, the dimension is to the driven load end of the stator core. 
DO ... Dimension between centerlines of base mounting grooves for resilient ring mounted motors or, on 

base drawings, the dimension of the base which fits the groove. 
DP ... Radial distance from center of Type C face at end opposite drive to center of circle defining the 

available area for disc brake lead opening(s). 
DQ ... Centerline of shaft to extreme outside part of secondary terminal housing (end view). 

EL ... Diameter of shaft after emergence from the mounting surface of face or flange. 

EM ... Diameter of shaft first step after EL. 



NEMA 


IEC 


Letter 


Letter 


BR 




BS 




BT 




BU 




BV 




BW 




BX 




BY 




BZ 




CA 




CB 




CC 




CD 




CE 




CF 




CG 




CH 




CL 




CO 




DB 




DC 





© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 4, Page 4 DIMENSIONS, TOLERANCES, AND MOUNTING 

Table 4-1 (Continued) 
LETTER SYMBOLS FOR DIMENSIONS 

Dimension Indicated 

Internal threaded portion of shaft extension. 

Top of coupling to underside of canopy of vertical hollow-shaft motor, 

Diameter of shaft at emergence from bearing (face or flange end). 

Length of shaft from mounting surface of face or flange to EL-EM interface. 

Length of shaft from EP-EL interface to end of shaft. 

Usable length of keyseat. 

Length of shaft from mounting surface of face or flange to EM-U interface. 

Diameter of shaft at bottom of ring groove. 

Distance between centerline of H hole and end of motor foot at shaft end (side view). 

Width of the ring groove or gib head keyseat. 

Distance from end of shaft to opposite side of ring groove keyseat. 

Distance from the shoulder of the shaft at opposite drive end to the center-line of the mounting 
holes in the nearest feet. 

FC LC Overall length of double shaft extension machine (For overall length of single shaft extension, see 

letter dimension C.) 

Length of the shaft extension from the shoulder at opposite drive end. 

Distance from the bottom of the keyway to the opposite surface of the shaft extension at opposite 

drive end. 

Width of the keyway of the shaft extension at opposite drive end. 

Diameter of the shaft extension at opposite drive end. 

Depth of the keyway at the crown of the shaft extension at opposite drive end. 



NEMA 


IEC 


Letter 


Letter 


EN 




EO 




EP 




EQ 




ER 




ES 




ET 




EU 




EV 




EW 




EX 




FBA 


CA 



FN-FW 


EA 


FR 


GB 


FS 


FA 


FU 


DA 


FU-FR 


GH 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTING 



MG 1-2009 
Part 4, Page 5 



KEY SEAT 



U 



-FS -~| 



FR V 

T 



2) 



frc; 



FLAT 



FN-FW —h — FBA 




KEY SEAT 

-1— S 




FLAT 



T 



AX | 




J 




4 


2F - 

p BASE TYPE q 


* 


AX| 


I 




O 




AT 


"r i _^ 


AW- 




l" AR 

AM - 



w- — 




-V^Y^- 

TAPERED SHAFT 
EXTENSION 



Figure 4-1 
LETTER SYMBOLS FOR FOOT-MOUNTED MACHINES— SIDE VIEW 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 6 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTING 




- — BT- 


— ^- 




-So \ 







Figure 4-2 
LETTER SYMBOLS FOR FOOT-MOUNTED MACHINES—DRIVE END VIEW 



© Copyright 2009 by the National Electrical Manufacturers Association. 



O 
o 

C\J 



CO 



o 



Q 

UJ £a . 

% ~'i_ LU ^ til 

LU Q < O t 

_j Q N -2 

O < CO £ LU 

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X UJ Ij O ~ 



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z 



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Q 

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CO 
LU 

o 

z 

LU 




CO 

UJ 

z 

X 
O 
< 

s 

CO 
CO 

LU 



o 
o 

u. 
a: 
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lis 

QllC 



>- 
CO 

en 
m 

H 
I- 
LU 



c 
g 

"55 
"o 
o 

to 

< 



<D 



o 

.TO 



o 


3 


o 


c 

CO 


LJ_ 


2 







<o? 


CO 

o 


V h- 


L_ 


*z 


o 


£3 


CD 


30 


LU 


.5»S 


"CO 


U- UJ 

O 


C 

.Q 


< 


CO 


u. 


z: 


O 





UJ 


*■• 


a. 

> 




H 


O 


oc 


O 
O 


o 


CM 


U- 


jC 


co 


O) 


—1 


l_ 


o 


Q_ 


OQ 


o 



o 

© 



C 

g 

: 
05 i 



CO 

Z 

o 

CO 

z 

LU 



o ^ 
d) Z 

o 



CO 
LU 
O 

z 



LU 

_l 

o 

h- 

CO 

Z 

o 

CO 

z 

LU 
Q 




CO 
LU 

z 
I 
o 
< 

CO 
CO 
LU 



o 
o 

O 

I- 

o 
o 

LL 

o 



g 
*-*— » 
eg 
o 
o 

< 





c 

CO 



CO 

CD 
o ro 

O Q. 
<N „ 

2 CL 




q> O 
il o 



LU 
CL 



0£ 

o 

Li. 
CO 

■J 
O 
CQ 

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CO 

DC 
LU 



LU 



CO 

o 



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LU 

16 

c 
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TO 

Z 

<L> 

JC 
■*- • 

O) 
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O 
CM 

j£ 

Q. 
O 
O 

<0> 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTING 



MG 1-2009 
Part 4, Page 9 




,. L 




DRIVEN HALF OF COUPLING 
VERTICAL HOLLOW SHAFT 



EW 



ES 



EX 



T 



i 



K 



■4- EU 
u 



MAX 



R H 



FT 



SHAFT EXTENSION 
VERTICAL SOLID SHAFT 



AH 



^ j J*^0.03R I j y 



Figure 4-5 
LETTER SYMBOLS FOR VERTICAL MACHINES 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 10 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTING 



4.2 SYSTEM FOR DESIGNATING FRAMES 

The system for designating frames of motors and generators shall consist of a series of numbers in 
combination with letters, defined as follows: 

4.2.1 Frame Numbers 

The frame number for small machines shall be the D dimension in inches multiplied by 16. 

The system for numbering the frames of other machines shall be according to Table 4-2, as follows: 

a. The first two digits of the frame number are equal to four times the D dimension in inches. When 

this product is not a whole number, the first two digits of the frame number shall be the next higher 
whole number. 

b. The third and, when required, the fourth digit of the frame number is obtained from the value of 2F 

in inches by referring to the columns headed 1 to 15, inclusive. 

As an example, a motor with a D dimension of 6.25 inches and 2F of 10 inches would be designated as 
frame 256. 

Table 4-2 
MACHINE FRAME NUMBERING 



Frame 




















Number 






Third/Fourth 


Digit in Frame Number 








Series 


D 


1 


2 


3 


4 


5 


6 


7 






3.50 








2 F Dimensions 








140 


3.00 


3.50 


4.00 


4.50 


5.00 


5.50 


6.25 




160 


4.00 


3.50 


4.00 


4.50 


5.00 


5.50 


6.25 


7.00 




180 


4.50 


4.00 


4.50 


5.00 


5.50 


6.25 


7.00 


8.00 




200 


5.00 


4.50 


5.00 


5.50 


6.50 


7.00 


8.00 


9.00 




210 


5.25 


4.50 


5.00 


5.50 


6.25 


7.00 


8.00 


9.00 




220 


5.50 


5.00 


5.50 


6.25 


6.75 


7.50 


9.00 


10.00 




250 


6.25 


5.50 


6.25 


7.00 


8.25 


9.00 


10.00 


11.00 




280 


7.00 


6.25 


7.00 


8.00 


9.50 


10.00 


11.00 


12.50 




320 


8.00 


7.00 


8.00 


9.00 


10.50 


11.00 


12.00 


14.00 




360 


9.00 


8.00 


9.00 


10.00 


11.25 


12.25 


14.00 


16.00 




400 


10.00 


9.00 


10.00 


11.00 


12.25 


13.75 


16.00 


18.00 




440 


11.00 


10.00 


11.00 


12.50 


14.50 


16.50 


18.00 


20.00 




I 500 


12.50 


11.00 


12.50 


14.00 


16.00 


18.00 


20.00 


22.00 




580 


14.50 


12.50 


14.00 


16.00 


18.00 


20.00 


22.00 


25.00 




680 


17.00 


16.00 


18.00 


20.00 


22.00 


25.00 


28.00 


32.00 




Frame 




















Number 


D 






Third/Fourth Dig 


it in Frame Number 






Series 


8 


9 


10 


11 


12 


13 


14 


15 




3.50 








2F Dimensions 








140 


7.00 


8.00 


9.00 


10.00 


11.00 


12.50 


14.00 


16.00 


160 


4.00 


8.00 


9.00 


10.00 


11.00 


12.50 


14.00 


16.00 


18.00 


180 


4.50 


9.00 


10.00 


11.00 


12.50 


14.00 


16.00 


18.00 


20.00 


200 


5.00 


10.00 


11.00 














210 


5.25 


10.00 


11.00 


12.50 


14.00 


16.00 


18.00 


20.00 


22.00 


220 


5.50 


11.00 


12.50 














250 


6.25 


12.50 


14.00 


16.00 


18.00 


20.00 


22.00 


25.00 


28.00 


280 


7.00 


14.00 


16.00 


18.00 


20.00 


22.00 


25.00 


28.00 


32.00 


320 


8.00 


16.00 


18.00 


20.00 


22.00 


25.00 


28.00 


32.00 


36.00 


360 


9.00 


18.00 


20.00 


22.00 


25.00 


28.00 


32.00 


36.00 


40.00 


400 


10.00 


20.00 


22.00 


25.00 


28.00 


32.00 


36.00 


40.00 


45.00 


440 


11.00 


22.00 


25.00 


28.00 


32.00 


36.00 


40.00 


45.00 


50.00 


500 


12.50 


25.00 


28.00 


32.00 


36.00 


40.00 


45.00 


50.00 


56.00 


580 


14.50 


28.00 


32.00 


36.00 


40.00 


45.00 


50.00 


56.00 


63.00 


680 


17.00 


36.00 


40.00 


45.00 


50.00 


56.00 


63.00 


71.00 


80.00 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTING Part 4, Page 1 1 

4.2.2 Frame Letters 

Letters shall immediately follow the frame number to denote variations as follows: 

A— Industrial direct-current machine 

B— Carbonator pump motors (see 18.270 through 18.281) 

C— Type C face-mounting on drive end 

When the face mounting is at the end opposite the drive end, the prefix F shall be used, making the 
suffix letters FC. 

CH — Type C face-mounting dimensions are different from those for the frame designation having the 

suffix letter C (the letters CH are to be considered as one suffix and shall not be separated) 
D— Type D flange-mounting on drive end 

When the flange mounting is at the end opposite the drive end, the prefix F shall be used, making 
the suffix letters FD 

E — Shaft extension dimensions for elevator motors in frames larger than the 326T frame 

G— Gasoline pump motors (see 18.91) 

H — Indicates a small machine having an F dimension larger than that of the same frame without the 
suffix letter H (see 4.4.1 and 4.5.1) 

HP and HPH — Type P flange mounting vertical solid shaft motors having dimensions in accordance with 
18.252 (the letters HP and HPH are to be considered as one suffix and shall not be separated) 

J — Jet pump motors (see 18.132) 

JM — Type C face-mounting close-coupled pump motor having antifriction bearings and dimensions in 
accordance with Table 1 of 18.250 (the letters JM are to be considered as one suffix and shall not 
be separated) 

jp — 7yp e c face-mounting close-coupled pump motor having antifriction bearings and dimensions in 
accordance with Table 2 of 18.250 (the letters JP are to be considered as one suffix and shall not be 
separated) 

K— Sump pump motors (see 18.78) 

LP and LPH — Type P flange-mounting vertical solid shaft motors having dimensions in accordance with 
18.251 (the letters LP and LPH are to be considered as one suffix and shall not be separated) 

M— Oil burner motors (see 18.106) 

N — Oil burner motors (see 18.106) 

P and PH — Type P flange-mounting vertical hollow shaft motors having dimensions in accordance with 
18.238 

R— Drive end tapered shaft extension having dimensions in accordance with this part (see 4.4.2) 

S — Standard short shaft for direct connection (see dimension tables) 

T — Included as part of a frame designation for which standard dimensions have been established (see 
dimension tables) 

U— Previously used as part of a frame designation for which standard dimensions had been established 
(no longer included in this publication) 

V — Vertical mounting only 

VP — Type P flange-mounting vertical solid-shaft motors having dimensions in accordance with 18.237 

(The letters VP are to be considered as one suffix and shall not be separated.) 
X— Wound-rotor crane motors with double shaft extension (see 18.229 and 18.230) 
Y— Special mounting dimensions (dimensional diagram must be obtained from the manufacturer) 

Z — All mounting dimensions are standard except the shaft extension(s)(also used to designate machine 
with double shaft extension) 

Note — For their own convenience manufacturers may use any letter in the alphabet preceding the frame number, but such 
a letter will have no reference to standard mounting dimensions. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 4, Page 12 DIMENSIONS, TOLERANCES, AND MOUNTING 

Suffix letters shall be added to the frame number in the following sequence: 



Suffix Letters 


Sequence 


A, H 


1 


G, J, M, N, T, U, HP, HPH, JM, JP, LP, LPH and VP 


2 


R and S 


3 


C, D, P and PH 


4 


FC, FD 


5 


V 


6 


E, X, Y, Z 


7 



4.3 MOTOR MOUNTING AND TERMINAL HOUSING LOCATION 

The motor mounting and location of terminal housing shall be as shown in assembly symbol F-1 of Figure 

4-6. Where other motor mountings and terminal housing locations are required, they shall be designated 

in accordance with the symbols shown in Figure 4-6. 

Assembly symbols F-1, W-2, W-3, W-6, W-8, and C-2 show the terminal housing in the same relative 

location with respect to the mounting feet and the shaft extension. 

All mountings shown may not be available for all methods of motor construction. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTING 



MG 1-2009 
Part 4, Page 13 



FLOOR MOUNTINGS 



& 



ASSEMBLY F-1 



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ASSEMBLY F2 



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Ma — L* 



ASSEMBLY f3 



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ASSEMBLY W-5 ASSEMBLY W-6 



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tw — wr 



ASSEMBLY W-7 



a 






ASSEMBLY W-1 ASSEMBLY W^ ASSEMBLY W3 ASSEMBLY W4 




ASSEMBLY W-8 



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ASSEMBLY W-9 ASSEMBLY W-10 ASSEMBLY W-11 



ASSEMBLY W-12 



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D 



h 



ASSEMBLY C-1 



CEILING MOUNTINGS 

yip— tv 

ASSEMBLY C4 



HP — "IK 



H 



ASSEMBLY C3 



Figure 4-6 
MACHINE ASSEMBLY SYMBOLS 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 
Part 4, Page 18 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTING 



4.4.5 Dimensions for Type FC Face Mounting for Accessories on End Opposite Drive End 
of Alternating-Current Motors 















FBFHole 














Bolt 


Hole for 
















Penetration 


Accessory 




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Number 


Tap Size 


Allowance 




Leadsft 


Frame Designations 


DP 


Diameter 


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3.81 


0.62 


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0.62 


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11.25 


4 


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0.75 


4.50 


0.62 


324TFC and 326TFC 


11.000 


12.500 


0.25 


14.00 


4 


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0.94 


5.25 


0.62 



The tolerance on this FBB dimension shall be +0.00, -0.06 inch. 

fThis BD dimension is a nominal dimension. 

tfWhen a hole is required in the Type C face for accessory leads, the hole shall be located within the available area defined by a circle 

located in accordance with the figure and the table. 

NOTES— 

1 . For the meaning of the letter dimensions, see 4. 1 . 

2. For tolerances on FAK dimensions, face runout, and permissible eccentricity of mounting rabbits, see 4.12. For permissible shaft 
runout see 4.9. 

3. Standards have not been developed for the FU, FAH, FBC, and keys at dimensions. 




OPENING FOR LEADS 
TO ACCESSORY 



FBF 



■FBF 
143TFC to 184TFC frames, incl. 

All dimensions in inches. 




213TFC to 326TFC frames, Incl. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 Section I 

Part 4, Page 28 DIMENSIONS, TOLERANCES, AND MOUNTINGS 

4.5.8 Base Dimensions for Types P and PH Vertical Solid-Shaft 
Industrial Direct-Current Motors 1 





AK 


BB Min 


BD Max 


BF Clearance Hole 


AJ 


Number 


Size 


9.125 


8.250 


0.19 


10 


4 


0.44 


9.125 


8.250 


0.19 


12 


4 


0.44 


14.750 


13.500 


0.25 


16.5 


4 


0.69 


14.750 


13.500 


0.25 


20 


4 


0.69 


14.750 


13.500 


0.25 


24.5 


4 


0.69 



All dimensions in inches. 
Tolerances (See 4.13.) 
AK Dimension — 

For 8.250 inches, +0.003 inch, 0.000 inch. 

For 13.500 inches, +0.005 inch, -0.000 inch. 
Face runout — 

For AJ of 9.125 inches, 0.004-inch indicator reading. 

For AJ of 14.750 inches, 0.007-inch indicator reading. 
Permissible eccentricity of mounting rabbet — 

For AK of 8.250 inches, 0.004-inch indicator reading. 

For AK of 13.500 inches, 0.007-inch indicator reading. 

4.5.9 Dimensions for Type FC Face Mounting for Accessories 

on End Opposite Drive End of Industrial Direct-Current Motors2,3 





FBB* 


FBC 




FBF Hole 




FAJ FAK 


Number 


Tap Size 


Bolt 
Penetration 
Allowance 


5.875 4.500 
7.250 8.500 
9.000 10.500 
11.000 12.500 


0.16 
0.31 
0.31 
0.31 


0.12 
0.25 
0.25 
0.25 


4 
4 
4 
4 


3/8-16 
1/2-13 
1/2-13 
5/8-11 


0.56 
0.75 
0.75 

0.94 


All dimensions in inch. 

*Tolerances 

FBB Dimension— 

For 0.16 inch, +0.00 inch, 
For 0.31 inch, +0.00 inch, 


-0.03 inch. 
-0.06 inch. 











4.6 SHAFT EXTENSION DIAMETERS FOR UNIVERSAL MOTORS 

The shaft extension diameters, 4 in inches shall be: 



0.2500 0.3750 0.6250 

0.3125 0.5000 0.7500 



1 For the meaning of the letter dimensions, see 4.1 and Figure 4-5 

2 For the meaning of the letter dimensions, see 4.1 and Figure 4-3 

3 For tolerance on FAK dimensions, face runout, and permissible eccentricity of mounting rabbet, see 4.12. For 
permissible runout, see 4.9. 

4 For tolerances on shaft extension diameters and keyseats, see 4.9. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTINGS Part 4, Page 29 

4.7 TOLERANCE LIMITS IN DIMENSIONS 

The dimensions from the shaft center to the bottom of the feet shall be not greater than the dimensions 
shown on the manufacturer's dimension sheet. When the machine is coupled or geared to the driven (or 
driving) machines, shims are usually required to secure accurate alignment. 

4.8 KNOCKOUT AND CLEARANCE HOLE DIAMETER FOR MACHINE TERMINAL BOXES 

The diameter of the knockout, excluding any projection of breakout ears or tabs, and the clearance hole 
in the terminal box of a machine shall be in accordance with the following: 



Conduit 


Knockout or 


Clearance Hole Diameter, Inches 


Size, Inches 


Nominal 


Minimum 


Maximum 


1/2 


0.875 


0.859 


0.906 


3/4 


1.109 


1.094 


1.141 


1 


1.375 


1.359 


1.406 


1-1/4 


1.734 


1.719 


1.766 


1-1/2 


1.984 


1.969 


2.016 


2 


2.469 


2.453 


2.500 


2-1/2 


2.969 


2.953 


3.000 


3 


3.594 


3.578 


3.625 


3-1/2 


4.125 


4.094 


4.156 


4 


4.641 


4.609 


4.672 


5 


5.719 


5.688 


5.750 


6 


6.813 


6.781 


6.844 



4.9 TOLERANCES ON SHAFT EXTENSION DIAMETERS AND KEYSEATS 
4.9.1 Shaft Extension Diameter 

The tolerances on shaft extension diameters shall be: 



Tolerances, Inches 


Shaft Diameter, Inches 


Plus Minus 




0.1875 to 1.5000, incl. 
Over 1.5000 to 6.500, incl. 


0.000 0.0005 
0.000 0.001 





4.9.2 Keyseat Width 

The tolerance on the width of shaft extension keyseats shall be: 





Tolerances, Inches 


Width of Keyseat, Inches 


Plus Minus 


0.188 to 0.750, incl. 
Over 0750 to 1.500, incl. 


0.002 0.000 
0.003 0.000 



4.9.3 Bottom of Keyseat to Shaft Surface 

The tolerance from the bottom of the keyseat to the opposite side of a cylindrical shaft extension shall be 
+0.000 inch, -0.015 inch. 

The tolerance on the depth of shaft extension keyseats for tapered shafts shall be +0.015 inch, -0.000 
inch. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 30 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTINGS 



4.9.4. Parallelism of Keyseats to Shaft Centerline 

The tolerance for making keyseats parallel to the centerline of the shaft shall be as follows (also See 
Figure 4-7): 

a. For ES dimensions up to and including 4.00 in. - .002 in. 

b. For ES dimensions greater than 4.00 in. up to and including 10.00 in - .0005 in. per in. of ES 
dimension 

c. For ES dimensions exceeding 10.00 in. - .005 in. 



4.9.5 Lateral Displacement of Keyseats 

Keyseat lateral displacement is defined as the greatest distance at any point along the usable length of 
keyseat from the centerline of the keyseat to the plane through the centerline of the shaft extension 
perpendicular to the true position of the bottom of the keyseat. 

Keyseat lateral displacement shall not exceed ±0.010 in. (0.25mm), or 0.020 in. (0.51mm) total zone. 
See Figure 4-7. 

4.9.6 Diameters and Keyseat Dimensions 

The cylindrical shaft extension diameters and keyseat dimensions for square keys shall be as shown in 
Table 4-3. 

4.9.7 Shaft Runout 

The tolerance for the permissible shaft runout, when measured at the end of the shaft extension, shall be 
(see 4.11): 

a. For 0.1875- to 1.625-inch diameter shafts, inclusive— 0.002-in. indicator reading. 

b. For over 1 .625- to 6.500-inch diameter shafts, inclusive— 0.003-in. indicator reading. 

NOTE— Standards have not been established for shaft runouts where the shaft extension length exceeds the standard. 
However, runouts for shafts longer than standard are usually greater than those indicated above. 







A 


.020 in (0.51 mm) Total 


// 


A 


* 





PARALLELISM 
.002 IN (0.051 mm) 

.0005 IN (0.013 mm) per inch of ES Dim 
.005 IN (0.127 mm) 



TRUE POSITION 

// PARALLELISM 
-A- | DATUM 



LENGTH OF KEYSEAT 
ES<4IN(102mm) 
4IN<ES<10IN 
ES> 10 IN (250 mm) 



Figure 4-7 
KEYSEAT LATERAL DISPLACEMENT AND PARALLELISM 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTINGS 



MG 1-2009 
Part 4, Page 31 



Table 4-3 
CYLINDRICAL SHAFT EXTENSION DIAMETERS AND KEYSEAT DIMENSIONS FOR 

SQUARE KEYS 







Bottom of Keyseat to Opposite Side of 


Shaft Diameter, U 


Keyseat Width, S 


Cylindrical Shaft, R 


Inches 


Inches 


Inches 


0.1875 


Flat 


0.178 


0.2500 


Flat 


0.235 


0.3125 


Flat 


0.295 


0.3750 


Flat 


0.328 


0.5000 


Flat 


0.453 


0.6250 


0.188 


0.517 


0.7500 


0.188 


0.644 


0.8750 


0.188 


0.771 


1.0000 


0.250 


0.859 


1.1250 


0.250 


0.986 


1.2500 


0.250 


1.112 


1.3750 


0.312 


1.201 


1.5000 


0.375 


1.289 


1.625 


0.375 


1.416 


1.750 


0.375 


1.542 


1.875 


0.500 


1.591 


2.000 


0.500 


1.718 


2.125 


0.500 


1.845 


2.250 


0.500 


1.972 


2.375 


0.625 


2.021 


2.500 


0.625 


2.148 


2.625 


0.625 


2.275 


2.750 


0.625 


2.402 


2.875 


0.750 


2.450 


3.000 


0.750 


2.577 


3.125 


0.750 


2.704 


3.250 


0.750 


2.831 


3.375 


0.875 


2.880 


3.500 


0.875 


3.007 


3.625 


0.875 


3.134 


3.750 


0.875 


3.261 


3.875 


1.000 


3.309 


4.000 


1.000 


3.436 


4.250 


1.000 


3.690 


4.375 


1.000 


3.817 


4.500 


1.000 


3.944 


Over 4.500 to 5.500 


1.250 


* 


Over 5.500 to 6.500 


1.500 


* 








,_ u-s + Vu 2 -s 2 

R= 





4.9.8 Shaft Extension Key(s) 

When a machine shaft extension is provided with one or more straight keyseats, each shall be provided 
with a full key of normal shape and length, unless otherwise specified by the customer. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 32 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTINGS 



4.10 RING GROOVE SHAFT KEYSEATS FOR VERTICAL SHAFT MOTORS 

Dimensions and tolerances for ring groove shaft keyseats shall be in accordance with Table 4-4. 

Table 4-4 
DIMENSIONS AND TOLERANCES FOR RING GROOVE KEYSEATS 



U, Inches 




EU*, Inches 


EW, Inch 


BS 




EX, Inches 


0.8750 through 1.0000 




U-(0.1875) 


0.377 
0.375 






0.750 
0.745 


1.1250 through 1.5000 




U-(0.250) 


0.377 
0.375 






0.750 

0.745 


1.625 through 2.500 




U-C0.375) 


0.377 
0.375 






0.750 
0.745 


2.625 through 4.500 




U-{0.500) 


0.503 
0.500 






1.000 
0.990 


4.625 through 6.000 




U-(0.750) 


0.755 
0.750 






1.500 
1.485 


*Tolerance on ring keyseat diameter 


(EU) 












Nominal Shaft Diameter, 


Inches 




To 


lerances, Inches 


0.875 to 2.500 


incl. 








+0.000/-0.005 




2.625 to 4.500 


incl. 








+0.000/-0.010 




4.625 to 6.000 


incl. 








+0.000/-0.015 





4.1 1 METHOD OF MEASUREMENT OF SHAFT RUNOUT AND OF ECCENTRICITY AND FACE 
RUNOUT OF MOUNTING SURFACES 

4.11.1 Shaft Runout 

The shaft runout shall be measured with the indicator stationary with respect to the motor and with its 
point at the end of the finished surface of the shaft. See Figures 4-8 and 4-9 for typical fixtures. 
Read the maximum and minimum values on the indicator as the shaft is rotated slowly through 360 
degrees. The difference between the readings shall not exceed the specified value. 

4.1 1 .2 Eccentricity and Face Runout of Mounting Surfaces 

The eccentricity and face runout of the mounting surfaces shall be measured with indicators mounted on 
the shaft extension. The point of the eccentricity indicator shall be at approximately the middle of the 
rabbet surface, and the point of the face runout indicator shall be at approximately the outer diameter of 
the mounting face. See Figure 4-10 for typical fixture. 

Read the maximum and minimum values on the indicators as the shaft is rotated slowly through 360 
degrees. The difference between the readings shall not exceed the specified value. 

NOTE— On ball-bearing motors, it is recommended that the test be made with the shaft vertical to minimize the 
effect of bearing clearances. 

4.12 TOLERANCES FOR TYPE C FACE MOUNTING AND TYPE D FLANGE MOUNTING MOTORS 

For Type C face-mounting and Type D flange-mounting motors, the tolerance on the mounting rabbet 
diameter, the maximum face runout, and the maximum eccentricity of the mounting rabbet shall be as in 
Table 4-5 when measured in accordance with 4.1 1 . 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTINGS 



MG 1-2009 
Part 4, Page 33 



Table 4-5 
MAXIMUM ECCENTRICITY OF MOUNTING RABBET 



Maximum 

Permissible 

Eccentricity of 



AK Dimension, 
Inches 


Tolerance 
Plus 


on 


AK Dimension, Inches 
Minus 


Maximum Face 
Runout, Inches 


Mo 


unting Rabbet 
Inches 


<12 


0.000 






0.003 


0.004 




0.004 


>12to24 


0.000 






0.005 


0.007 




0.007 


>24 to 40 


0.000 






0.007 


0.009 




0.009 



4.13 TOLERANCES FOR TYPE P FLANGE-MOUNTING MOTORS 

For Type P flange-mounting motors (see Figure 4-5), the tolerance on the mounting rabbet diameter, the 
maximum face runout, and the maximum eccentricity of the mounting rabbet shall be as in Table 4-6 
when measured in accordance with 4.11. 



AK Dimension, 
Inches 



Table 4-6 
MAXIMUM ECCENTRICITY OF MOUNTING RABBET 



Tolerance on AK Dimension, Inches 
Plus Minus 



Maximum Face 
Runout, Inches 



Maximum 

Permissible 

Eccentricity of 

Mounting Rabbet 

Inches 



<12 
>12to24 
>24 to 40 
>40 to 60 



0.003 
0.005 
0.007 
0.010 



0.000 
0.000 
0.000 
0.000 



0.004 
0.007 
0.009 
0.012 



0.004 
0.007 
0.009 
0.012 



4.14 MOUNTING BOLTS OR STUDS 

Bolts or studs used for installing foot-mounting machines may be one size smaller than the maximum size 
permitted by the foot hole diameter if Grade 5 or 8 fasteners and heavy duty washers are used. Doweling 
after alignment is recommended. 

NOTE— For the definition of Grade 5 or 8 fasteners refer to ANSI/SAE Standard J429. 



k. 



r 




Figure 4-8 
SHAFT RUNOUT 



Figure 4-9 
SHAFT RUNOUT 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 34 



ECCENTRICITY OF 
MOUNTING RABBET 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTINGS 

MOUNTING RABBET 



MOUNTING FACE 




FACE RUNOUT 



Figure 4-10 
ECCENTRICITY AND FACE RUNOUT OF MOUNTING SURFACES 



4.15 METHOD TO CHECK COPLANARITY OF FEET OF FULLY ASSEMBLED MOTORS 

To check the flatness of the feet of a fully assembled motor, the motor shall be placed on a flat surface 
plate (tool room grade "B"), and a feeler gauge inserted between the surface plate and the motor feet at 
each bolt mounting hole. A feeler gauge of the required coplanar tolerance shall not penetrate any gap 
between the bottom of the feet and the surface plate within a circular area about the centerline of the bolt 
hole with a diameter equal to 3 times the bolt hole diameter or 1 inch, whichever is greater. The motor 
must not be allowed to shift or rock, changing points of contact during these measurements. If the room 
temperature is not controlled the surface plate shall be a granite block. Alternate methods using lasers or 
co-ordinate measuring machines can be used provided they are shown to provide equivalent results. 

4.16 METHOD OF MEASUREMENT OF SHAFT EXTENSION PARALLELISM TO FOOT PLANE 

When measuring the parallelism of the shaft extension with respect to the foot mounting surface, the 
motor shall be mounted on a flat surface satisfying the requirements of the coplanar test (see 4.15) and 
the parallelism measured by determining the difference between the distances from the mounting surface 
to the top or bottom surface of the shaft, at the end of the shaft, and to the top or bottom surface of the 
shaft, at the position on the shaft corresponding to the BA dimension. Alternate methods using lasers or 
co-ordinate measuring machines can be used provided they are shown to provide equivalent results. 

4.17 MEASUREMENT OF BEARING TEMPERATURE 

Either thermometers, thermocouples, resistance temperature devices (RTD), or other temperature 
detectors may be used. The measuring point shall be located as near as possible to one of the two 
locations specified in the following table: 



Type of Bearing 



Location Measuring Point 



Ball or roller 



Sleeve 



Preferred In the bearing housing at the outer ring of the bearing, or if not practical, not more 
than 1/2 inch from the outer ring of the bearing. 

Alternate Outer surface of the bearing housing as close as possible to the outer ring of the 

bearing. 

Preferred In the bottom of the bearing shell and not more than 1/2 inch from the oil-film. 
Alternate Elsewhere in the bearing shell. 



Thermal resistance between the temperature detector and the bearing to be measured shall be 
minimized. For example, any gaps could be packed with a suitable thermal conductive material. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTINGS Part 4, Page 35 

4.18 TERMINAL CONNECTIONS FOR SMALL MOTORS 

4.18.1 Terminal Leads 

The terminal leads of small motors shall be brought: (1) out of the end shield at the end opposite the drive 
end and at the right-hand side when viewing this end; or (2) out of the frame at the right-hand side when 
viewing the end opposite the drive end and as close to this end as is practicable. 

4.18.2 Blade Terminals 

Except where other dimensions for blade terminals are specified in Part 18, blade terminals when used 
for external connection of small motors shall have the following dimensions: 

Frame Size Width, Inches Thickness, Inches 

48 and larger 0.250 0.031 

Smaller than 48 0.187 0.020 



4.19 MOTOR TERMINAL HOUSINGS 

4.19.1 Small and Medium Motors 

Terminal housings shall be of metal and of substantial construction. For motors over 7 inches in diameter, 
the terminal housings shall be capable of withstanding without failure a vertical loading on the horizontal 
surfaces of 20 pounds per square inch of horizontal surface up to a maximum of 240 pounds. This load 
shall be applied through a 2-inch-diameter flat metal surface. Bending or deforming of the housing shall 
not be considered a failure unless it results in spacings between the housing and any rigidly mounted live 
terminals less than those given in 4.19.2.2. 

In other than hazardous (classified) locations, substantial, non-metallic, non-burning 1 terminal housings 
shall be permitted to be used on motors and generators provided internal grounding means between the 
machine frame and the equipment grounding connection is incorporated into the housing. 

4.19.2 Dimensions 

4.19.2.1 Terminal Housings for Wire-to-Wire Connections— Small and Medium Machines 

When these terminal housings enclose wire-to-wire connections, they shall have minimum dimensions and 
usable volumes in accordance with the following. Auxiliary leads for such items as brakes, thermostats, 
space heaters, exciting fields, etc., shall be permitted to be disregarded if their current-carrying area does 
not exceed 25 percent of the current-carrying area of the machine power leads. 

TERMINAL HOUSING— MINIMUM DIMENSIONS AND VOLUMES FOR MOTORS 
11 INCHES IN DIAMETER* OR LESS 





Cover 


Opening, 


Minimum 


Useable Volume Minimum, 


Hp 


Dimensions, 


Inches 


Cubic Inches 


1 and smaller** 




1.62 




10.5 


1 1/2, 2, and 3f 




1.75 




16.8 


5 and 7 1/2 




2.00 




22.4 


10 and 15 




2.50 




36.4 



*This is a diameter measured in the plane of lamination of the circle circumscribing the stator 
frame, excluding lugs, fins, boxes, etc., used solely for motor cooling, mounting, assembly, or 
connection. 

**For motors rated 1 horsepower and smaller and with the terminal housing partially or wholly 
integral with the frame or end shield, the volume of the terminal housing shall be not less than 
1.1 cubic inch per wire-to-wire connection. The minimum cover opening dimension is not 
specified. 

fFor motors rated 1-1/2, 2, and 3 horsepower and with the terminal housing partially or wholly 
integral with the frame or end shield, the volume of the terminal housing shall be not less than 
1.4 cubic inch per wire-to-wire connection. The minimum cover opening dimension is not 
specified. 



1 See American Society for Testing and Materials— Test for Flammability of Self-Supporting Plastics, ASTM D635-81, over 0.050 inch 
(0.127 cm) in thickness, for the non-burning test. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 36 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTINGS 



TERMINAL HOUSING— MINIMUM DIMENSIONS AND VOLUMES FOR MOTORS 
OVER 11 INCHES IN DIAMETER* 



Alternating-current Motors 


Maximum 

Full-Load 

Current for 

Three-Phase 

Motors with 

Maximum of 

Twelve Leads, 


Terminal Box 

Cover Opening 

Minimum 

Dimension, 

Inches 


Usable Volume, 

Minimum, 

Cubic Inches 


Typical Maximum Three Phase 
Horsepower 


Amperes 


230 Volts 460 Volts 


45 

70 


2.5 
3.3 


36.4 
77 


15 30 
25 50 


110 


4.0 


140 


40 75 


160 


5.0 


252 


60 125 


250 


6.0 


450 


100 200 


400 


7.0 


840 


150 300 


600 


8.0 


1540 
Direct Current Motors 


250 500 


Maximum 

Full-Load 

Current for 

Motors with 

Maximum of Six 

Leads 


Terminal 

Housing 

Minimum 

Dimension, 

Inches 


Usable Volume, 

Minimum, 

Cubic Inches 




68 
105 


2.5 
3.3 


26 
55 




165 


4.0 


100 




240 


5.0 


180 




375 


6.0 


330 




600 


7.0 


600 




900 


8.0 


1100 





*This is a diameter measured in the plane of lamination of the circle circumscribing the stator frame, 
excluding lugs, fins, boxes, etc., used solely for motor cooling, mounting, assembly, or connection. 

4.19.2.2 Terminal Housings for Rigidly-Mounted Terminals — Medium Machines 

When the terminal housings enclose rigidly-mounted motor terminals, the terminal housings shall be of 
sufficient size to provide minimum terminal spacings and usable volumes in accordance with the 
following: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTINGS Part 4, Page 37 

TERMINAL SPACINGS 





Minimum Spacing, Inches 


Volts 


Between Line Terminals 
and Other Uninsulated 
Between Line Terminals Metal Parts 


250 or less 
251—600, inci. 


0.25 0.25 
0.38 0.38 


USABLE VOLUMES 


Power Supply Conductor 


Minimum Usable Volume per Power 
Size, AWG Supply Conductor, Cubic Inches 


14 
12 and 10 

8 and 6 


1.0 
1.25 
2.25 



For larger wire sizes or when motors are installed as a part of factory-wired equipment, without additional 
connection being required at the motor terminal housing during equipment installation, the terminal 
housing shall be of ample size to make connections, but the foregoing provisions for the volumes of 
terminal housings need not apply. 

4.19.2.3 Terminal Housings for Large AC Motors 

When large motors are provided with terminal housings for line cable connections 1 , the minimum 

dimensions and usable volume shall be as indicated in Table 4-6 for Type I terminal housings or Figure 4- 

1 1 for Type II terminal housings. 

Unless otherwise specified, when induction motors are provided with terminal housings, a Type I terminal 

housing shall be supplied. 

For motors rated 601 volts and higher, accessory leads shall terminate in a terminal box or boxes 

separate from the machine terminal housing. As an exception, current and potential transformers located 

in the machine terminal housing shall be permitted to have their secondary connections terminated in the 

machine terminal housing if separated from the machine leads by a suitable physical barrier. 

For motors rated 601 volts and higher, the termination of leads of accessory items normally operating at a 

voltage of 50 volts (rms) or less shall be separated from leads of higher voltage by a suitable physical 

barrier to prevent accidental contact or shall be terminated in a separate box. 



1 Terminal housings containing stress cones, surge capacitors, surge arresters, current transformers, or potential 
transformers require individual consideration. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 4, Page 38 DIMENSIONS, TOLERANCES, AND MOUNTINGS 



Table 4-6 

TYPE I TERMINAL HOUSING 

UNSUPPORTED AND INSULATED TERMINATIONS 







Minimum 


Minimum 


Minimum 






Useable 


Internal 


Centerline 




Maximum Full- 


Volumes, Cubic 


Dimensions, 


Distance/ 


Voltage 


Load Current 


Inches 


Inches 


Inches 


0-600 


400 


900 


8 


___ 




600 


2000 


8 


... 




900 


3200 


10 


___ 




1200 


4600 


14 


... 


601-2400 


160 


180 


5 







250 


330 


6 


~_ 




400 


900 


8 


... 




600 


2000 


8 


12.6 




900 


3200 


10 


12.6 




1500 


5600 


16 


20.1 


2401-4800 


160 


2000 


8 


12.6 




700 


5600 


14 


16 




1000 


8000 


16 


20 




1500 


10740 


20 


25 




2000 


13400 


22 


28.3 


4801-6900 


260 


5600 


14 


16 




680 


8000 


16 


20 




1000 


9400 


18 


25 




1500 


11600 


20 


25 




2000 


14300 


22 


28.3 


6901-13800 


400 


44000 


22 


28.3 




900 


50500 


25 


32.3 




1500 


56500 


27.6 


32.3 




2000 


62500 


30.7 


32.3 



'Minimum distance from the entrance plate for conduit entrance to the centerline of machine leads. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

DIMENSIONS, TOLERANCES, AND MOUNTINGS 



MG 1-2009 
Part 4, Page 39 




' SHIELD 
GROUND 
SCREW 



DISTANCE FROM THE 
MANUFACTURER 
SUPPLIED TERMINAL 
TO THE BOTTOM OF 
THE BOX 





MACHINE 7 
BASE 
























Minimum Dimensions (Inches) 








Machine 
Voltage 


L 


W 


D 


ABC 


X 


E 


F 


G 


460-600 


24 


18 


18 


9-1/2 8-1/2 4 


5 


2-1/2 


4 


12 


2300-4800 


26 


27 


18 


9-1/2 8-1/2 5-1/2 


8 


3-1/2 


5 


14 


6600-6900 


36 


30 


18 


9-1/2 8-1/2 6 


9 


4 


6 


30 


13200-13800 


48 


48 


25 


13-1/2 11-1/2 8-1/2 


13-1/2 


6-3/4 


9-1/2 


36 



Figure 4-11 

TYPE II MACHINE TERMINAL HOUSING STAND-OFF-INSULATOR-SUPPORTED 

INSULATED OR UNINSULATED TERMINATIONS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 4, Page 40 



Section I 
DIMENSIONS, TOLERANCES, AND MOUNTINGS 



4.19.2.4 Terminal Housings for Large AC Synchronous Generators 

When large ac synchronous generators are provided with terminal housings for wire-to-wire 
connections, 1 the housings shall have the following dimensions and useable volumes: 







Minimum 




Minimum 






Usable 


Minimum 


Centerline 






Volume 


Dimension, 


Distance/ 


Voltage 


kVA 


Cu. In. 


Inches 


Inches 


0-599 


<20 


75 


2.5 






21-45 


250 


4 






46-200 


500 


6 




480 


201-312, incl. 


600 


7 






313-500, incl. 


1100 


8 






501-750, incl. 


2000 


8 






751-1000, incl. 


3200 


10 




600 -2399 


201-312, incl.. 


600 


7 






313-500, incl. 


1100 


8 






501-750, incl. 


2000 


8 






751-1000, incl. 


3200 


10 




2400-4159 


251-625, incl. 


180 


5 






626-1000, incl. 


330 


6 






1000-1563, incl. 


600 


7 






1564-2500, incl. 


1100 


8 






2501-3750, incl. 


2000 


8 




4160-6899 


351-1250, incl. 


2000 


8 


12.5 




1251-5000, incl. 


5600 


14 


16 




5001-7500, incl. 


8000 


16 


20 


6900-13800 


876-3125, incl. 


5600 


14 


16 




3126-8750, incl. 


8000 


16 


20 



*Minimum distance from the entrance plate for conduit entrance to the centerline of generator leads. 



1 Terminal housings containing surge capacitors, surge arresters, current transformers, or potential transformers 
require individual consideration. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

DIMENSIONS, TOLERANCES, AND MOUNTINGS Part 4, Page 41 

4.20 GROUNDING MEANS FOR FIELD WIRING 

When motors are provided with terminal housings for wire-to-wire connections or fixed terminal 
connections, a means for attachment of an equipment grounding conductor termination shall be provided 
inside, or adjacent with accessibility from, the terminal housing. Unless its intended use is obvious, it shall 
be suitably identified. The termination shall be suitable for the attachment and equivalent fault current 
ampacity of a copper grounding conductor as shown in Table 4-7. A screw, stud, or bolt intended for the 
termination of a grounding conductor shall be not smaller than shown in Table 4-7. For motor full-load 
currents in excess of 30 amperes ac or 45 amperes dc, external tooth lockwashers, serrated screw 
heads, or the equivalent shall not be furnished for a screw, bolt, or stud intended as a grounding 
conductor termination. 

When a motor is provided with a grounding terminal, this terminal shall be the solderless type and shall 
be on a part of the machine not normally disassembled during operation or servicing. 

When a terminal housing mounting screw, stud, or bolt is used to secure the grounding conductor to the 
main terminal housing, there shall be at least one other equivalent securing means for attachment of the 
terminal housing to the machine frame. 







Table 4-7 








MINIMUM SIZE GROUNDING CONDUCTOR TERMINATION 








Minimum Size of Grounding 






Motor Full Load C 


urrent ^ 


Conductor Termination 
Attachment Means, AWG 


Minimum Size of Screw, 


Stud, or Bolt 


ac 


dc 




Steet 


Bronze 


12 


12 


14 


#6 


— 


16 


16 


12 


#8 


— 


30 


40 


10 


#10 


— 


45 


68 


8 


#12 


#10 


70 


105 


6 


5/16" 


#12 


110 


165 


4 


5/16" 


5/16" 


160 


240 


3 


3/8" 


5/16" 


250 


375 


1 


1/2" 


3/8" 


400 


600 


2/0 


... 


1/2" 


600 


900 


3/0 


— 


1/2" 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 4, Page 42 DIMENSIONS, TOLERANCES, AND MOUNTINGS 



< This page is intentionally left blank. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 5 



<This page is intentionally left blank.: 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES Part 5, Page 1 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 

Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

PartS 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



5.1 SCOPE 

This Standard applies to the classification of degrees of protection provided by enclosures for rotating 
electrical machines. It defines the requirements for protective enclosures that are in all other respects 
suitable for their intended use and which, from the point of view of materials and workmanship, ensure 
that the properties dealt with in this standard are maintained under normal conditions of use. 

This standard does not specify: 

• degrees of protection against mechanical damage of the machine, or conditions such as moisture 
(produced for example by condensation), corrosive vapours, fungus or vermin; 

• types of protection of machines for use in an explosive atmosphere; 

• the requirements for barriers external to the enclosure which have to be provided solely for the safety 
of personnel. 

In certain applications (such as agricultural or domestic appliances), more extensive precautions against 
accidental or deliberate contact may be specified. 

This standard gives definitions for standard degrees of protection provided by enclosures applicable to 
rotating electrical machines as regards the: 

a) protection of persons against contacts with or approach to live parts and against contact with moving 
parts (other than smooth rotating shafts and the like) inside the enclosure and protection of the machine 
against ingress of solid foreign objects; 

b) protection of machines against the harmful effects due to ingress of water. 

It gives designations for these protective degrees and tests to be performed to check that the machines 
meet the requirements of this standard. 

5.2 DESIGNATION 

The designation used for the degree of protection consists of the letters IP followed by two characteristic 
numerals signifying conformity with the conditions indicated in the tables of 5.3 and 5.4 respectively. 

5.2.1 Single Characteristic Numeral 

When it is required to indicate a degree of protection by only one characteristic numeral, the omitted 
numeral shall be replaced by the letter X, for example IPX5 or IP2X. 

5.2.2 Supplementary Letters 

Additional information may be indicated by a supplementary letter following the second characteristic 
numeral. If more than one letter is used, the alphabetic sequence shall apply. 

5.2.2.1 Letters Following Numerals 

In special applications (such as machines with open circuit cooling for ship deck installation with air inlet 
and outlet openings closed during stand-still) numerals may be followed by a letter indicating whether the 
protection against harmful effects due to ingress of water was verified or tested for the machine not 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 5, Page 2 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 

running (letter S) or the machine running (letter M). In this case the degree of protection in either state of 
the machine shall be indicated, for example IP55S/IP20M. 

The absence of the letters S and M shall imply that the intended degree of protection will be provided 
under all normal conditions of use. 

5.2.2.2 Letters Placed Immediately after the Letters IP 

For air-cooled open machines suitable for specific weather conditions and provided with additional 
protective features or processes (as specified in 5.10), the letter W may be used. 

5.2.3 Example of Designation 

IP 4 4 

Characteristic letters | 

1st characteristic numeral 

(see Table 5-1) 

2nd characteristic numeral 

(see Table 5-2) 



5.2.4 Most Frequently Used 

The most frequently used degrees of protection for electrical machines are given in Appendix A. 

5.3 DEGREES OF PROTECTION— FIRST CHARACTERISTIC NUMERAL 

5.3.1 Indication of Degree of Protection 

The first characteristic numeral indicates the degree of protection provided by the enclosure with respect 
to persons and also to the parts of the machine inside the enclosure. 

Table 5-1 gives, in column 3, brief details of objects which will be "excluded" from the enclosure for each 
of the degrees of protection represented by the first characteristic numeral. 

The term "excluded" implies that a part of the body, or a tool or a wire held by a person, either will not 
enter the machine or if it enters, that adequate clearance will be maintained between it and the live parts 
or dangerous moving parts (smooth rotating shafts and the like are not considered dangerous). 

Column 3 of Table 5-1 also indicates the minimum size of solid foreign objects which will be excluded. 

5.3.2 Compliance to Indicated Degree of Protection 

Compliance of an enclosure with an indicated degree of protection implies that the enclosure will also 
comply with all lower degrees of protection in Table 5-1. In consequence, the tests establishing these 
lower degrees of protection are not required, except in case of doubt. 

5.3.3 External Fans 

The blades and spokes of fans external to the enclosure shall be protected against contact by means of 
guards complying with the following requirements: 



Protection of machine Test of fan 

IP 1X 1 .968 inch (50 mm) sphere test 
IP2X to IP6X Finger test 



For the test, the rotor shall be slowly rotated, for example by hand when possible. 
Smooth rotating shafts and similar parts are not considered dangerous. 



► Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



MG 1-2009 
Part 5, Page 3 



5.3.4 Drain Holes 

If the machine is provided with drain holes, the following shall apply: 

a. Drain holes intended normally to be open on site shall be kept open during testing. 

b. Drain holes intended normally to be closed on site shall be kept closed during testing. 

c. If machines with protection IP3X or IP4X are intended to be run with open drain holes, the drain 
holes may comply with protection IP 2X. 

d. If machines with protection IP5X are intended to be run with open drain holes, the drain holes 
shall comply with protection IP4X. 



Table 5-1 
DEGREES OF PROTECTION INDICATED BY THE FIRST CHARACTERISTIC NUMERAL 


First 

Characteristic 

Numeral 


Degree of Protection 




Brief Description 

(Notel) 


Definition 


Test 
Condition 





Non-protected machine 


No special protection 


No test 


1 

(Note 2) 


Machine protected against 
solid objects greater than 
1.968 in. (50 mm) 


Accidental or inadvertent contact with or approach to live and moving 
parts inside the enclosure by a large surface of the human body, 
such as a hand (but no protection against deliberate access). 

Ingress of solid objects exceeding 1 .968 in. (50 mm) in diameter 


Table 5-3 


2 
(Note 2) 


Machine protected against 
solid objects greater than 

0.4724 in. (12 mm) 


Contact with or approach to live or moving parts inside the enclosure 
by fingers or similar objects not exceeding 3.15 inch (80 mm) in 
length. 

Ingress of solid objects exceeding 0.4724 in. (12 mm) in diameter. 


Table 5-3 


3 
(Note 2) 


Machine protected against 
solid objects greater than 
0.0984 in. (2.5 mm) 


Contact with or approach to live or moving parts inside the enclosure 
by tools or wires exceeding 0.0984 inch (2.5 mm) in diameter. 

Ingress of solid objects exceeding 0.0984 in. (2.5 mm) in diameter. 


Table 5-3 


4 
(Note 2) 


Machine protected against 
solid objects greater than 

0.0394 in. (1 mm) 


Contact with or approach to live or moving parts inside the enclosure 
by wires or strips of thickness greater than 0.0394 in. (1 mm). 

Ingress of solid objects exceeding 0.0394 in. (1 mm) in diameter 


Table 5-3 


5 
(Note 3) 


Dust-protected machine 


Contact with or approach to live or moving parts inside the enclosure. 

Ingress of dust is not totally prevented but dust does not enter in 
sufficient quantity to interfere with satisfactory operation of the 
machine. 


Table 5-3 


6 
(Note 3) 


Dust-tight machine 


Contact with or approach to live or moving parts inside the enclosure. 
No ingress of dust 


Table 5-3 


NOTES— 

1 . The brief des< 

2. Machines ass 
that three norma 

3. The degree o 
particles, their m 
manufacturer an 


sription given in column 2 in thi 

igned a first characteristic nurr 
ly perpendicular dimensions ol 

f protection against dust define 
iture, for instance fibrous partic 
d user. 


s table should not be used to specify the type of protection. 

eral 1 , 2, 3, or 4 will exclude both regularly or irregularly shaped solid o 
\ the object exceed the appropriate figure in column "Definition." 

d by this standard is a general one. When the nature of the dust (dimen 
les) is specified, test conditions should be determined by agreement be 


bjects provided 

sions of 
tween 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 5, Page 4 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



5.4 DEGREES OF PROTECTION— SECOND CHARACTERISTIC NUMERAL 

5.4.1 Indication of Degree of Protection 

The second characteristic numeral indicates the degree of protection provided by the enclosure with 
respect to harmful effects due to ingress of water. 

Table 5-2 gives, in column 3, details of the type of protection provided by the enclosure for each of the 
degrees of protection represented by the second characteristic numeral. 

An air-cooled open machine is weather-protected when its design reduces the ingress of rain, snow, and 
airborne particles, under specified conditions, to an amount consistent with correct operation. This 
degree of protection is designated by the letter "W" placed after the two characteristic numerals. 

5.4.2 Compliance to Indicated Degree of Protection 

For second characteristic numerals up to and including 6, compliance of an enclosure with an indicated 
degree of protection implies that the enclosure will also comply with ai! lower degrees of protection in 
Table 5-2. 

In consequence, the tests establishing these lower degrees of protection are not required, except in case 
of doubt. 

For IPX7 and IPX8, it shall not be assumed that compliance of the enclosure implies that the enclosure 
will also comply with all lower degrees of protection in Table 5-2. 



Table 5-2 
DEGREES OF PROTECTION INDICATED BY THE SECOND CHARACTERISTIC NUMERAL 



Second 

Characteristic 

Numeral 


Degree of Protection 




Brief Description 

(Notel) 


Definition 


Test Condition 





Non-protected machine 


No special protection 


No test 


1 


Machine protected 
against dripping water 


Dripping water (vertically falling drops) shall have no harmful 
effect. 


Table 5-4 


2 


Machine protected 
against dripping water 
when tilted up to 15 
degrees 


Vertically dripping water shall have no harmful effect when the 
machine is tilted at any angle up to 15 degrees from its normal 

position. 


Table 5-4 


3 


Machine protected 
against spraying water 


Water falling as a spray at an angle up to 60 degrees from the 
vertical shall have no harmful effect. 


Table 5-4 


4 


Machine protected 
against splashing water 


Water splashing against the machine from any direction shall 
have no harmful effect. 


Table 5-4 


5 


Machine protected 
against water jets 


Water projected by a nozzle against the machine from any 
direction shall have no harmful effect. 


Table 5-4 


6 


Machine protected 
against heavy seas 


Water from heavy seas or water projected in powerful jets shall 
not enter the machine in harmful quantities. 


Table 5-4 


7 


Machine protected 
against the effects of 
immersion 


Ingress of water in the machine in a harmful quantity shall not 
be possible when the machine is immersed in water under 
stated conditions of pressure and time. 


Table 5-4 


8 


Machine protected 
against continuous 
submersion (Note 2) 


The machine is suitable for continuous submersion in water 
under conditions which shall be specified by the manufacturer. 


Table 5-4 



NOTES— 

1 . The brief description given in column 2 

2. Normally, this means that the machine 
can enter but only in such a manner that it 



in this table should not be used to specify the type of protection. 

is hermetically sealed. However, with certain types of machines it can mean that water 

produces no harmful effect. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section! MG 1-2009 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES Part 5, Page 5 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 

5.5 MARKING 

It is recommended that the characteristic letters and numerals be marked on the machine preferably on 
the rating plate, or, if this is not practicable, on the enclosure. 

When all parts of a machine do not have the same degree of protection, at least the designation of the 
lowest degree shall be shown, followed, if necessary, by the higher designation with clear reference to 
the part to which it applies. 

NOTE— Space limitations on the rating plate usually only allow the lowest IP code to be marked. Parts or components 
having a higher degree of protection should then be specified in the documentation and/or in the operating 
instructions. 

The lower degree of protection of: 

• guards for external fans (as allowed in 5.4.3); 

• drain holes (as allowed in 5.4.4); 

• need not be specified on the rating plate or in the documentation. 

Where the mounting of the machine has an influence on the degree of protection, the intended mounting 
arrangements shall be indicated by the manufacturer on the rating plate or in the instructions for 
mounting. 

5.6 GENERAL REQUIREMENTS FOR TESTS 

The tests specified in this standard are type tests. They shall be carried out on standard products or 
models of them. Where this is not feasible, verification either by an alternative test or by examination of 
drawings shall be the subject of an agreement between manufacturer and user. 

Unless otherwise specified, the machine for each test shall be clean with all the parts in place and 
mounted in the manner stated by the manufacturer. 

In the case of both first and second characteristic numerals 1, 2, 3, and 4, a visual inspection may, in 
certain obvious cases, show that the intended degree of protection is obtained. In such cases, no test 
need be made. However, in case of doubt, tests shall be made as prescribed in 5.7 and 5.8. 

5.6.1 Adequate Clearance 

For the purpose of the following test clauses in this standard, the term "adequate clearance" has the 
following meaning: 

5.6.1.1 Low-Voltage Machines (Rated Voltages Not Exceeding 1000 V AC and 1500 V DC) 

The test device (sphere, finger, wire, etc.) does not touch the live parts or moving parts other than non- 
dangerous parts such as smooth rotating shafts. 

5.6.1.2 High-Voltage Machines (Rated Voltages Exceeding 1000 V AC and 1500 V DC) 

When the test device is placed in the most unfavorable position, the machine shall be capable of 
withstanding the dielectric test applicable to the machine. 

This dielectric test requirement may be replaced by a specified clearance dimension in air which would 
ensure that this test would be satisfactory under the most unfavorable electrical field configuration. 

5.7 TESTS FOR FIRST CHARACTERISTIC NUMERAL 

Test and acceptance conditions for the first characteristic numeral are given in Table 5-3. 

The dust test for numerals 5 and 6 shall be performed with the shaft stationary, provided that the 
difference in pressure between running and stationary (caused by fan effects) is lower than 2 kPa. If the 
pressure difference is greater than 2 kPa, the internal machine pressure during the dust test shall be 
depressed accordingly. Alternatively, the machine may be tested with the shaft rotating at rated speed. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section! 

Part 5, Page 6 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



Table 5-3 

TEST AND ACCEPTANCE CONDITIONS FOR FIRST CHARACTERISTIC NUMERAL 

First Characteristic 

Numeral Test and Acceptance Conditions 

No test is required. 

1 The test is made with a rigid sphere of 1 .968 +.002/-0 inches (50 +0.05/-0 mm) diameter applied against the 
opening(s) in the enclosure with a force of 1 1 .2 Ibf (50 N) ±1 percent. 

The protection is satisfactory if the sphere does not pass through any opening and adequate clearance is 
maintained to parts which are normally live in service or moving parts inside the machine. 

2 a. Finger test 

The test is made with a metallic test finger as shown in Figure 1-3 or 5-1. Both joints of this finger may be 
bent through an angle of 90 degrees with respect to the axis of the finger, but in one and the same direction 
only. The finger is pushed without undue force (not more than 2.24 Ibf (10 N)) against any openings in the 
enclosure and, if it enters, it is placed in every possible position. 

The protection is satisfactory if adequate clearance is maintained between the test finger and live or moving 
parts inside the enclosure. However, it is permissible to touch smooth rotating shafts and similar non- 
dangerous parts. 

For this test, the internal moving parts may be operated slowly, where this is possible. 

For tests on low-voltage machines, a low-voltage supply (of not less than 40V) in series with a suitable lamp 
may be connected between the test finger and the live parts inside the enclosure. Conducting parts covered 
only with varnish or paint, or protected by oxidation or by a similar process, shall be covered with a metal 
foil electrically connected to those parts that are normally live in service. The protection is satisfactory if the 
lamp does not light. 

For high-voltage machines, adequate clearance is verified by a dielectric test, or by a measurement of 
clearance distance in accordance with the principles of 5.6.1 .2. 

b. Sphere test 

The test is made with a rigid sphere of 0.4724 +.002/-0 inch (12.0 +0.05/-0 mm) diameter applied to the 
openings of the enclosure with a force of 6.74 Ibf (30 N) ±10 percent. 

The protection is satisfactory if the sphere does not pass through any opening and adequate clearance is 
maintained to live or moving parts inside the machine. 

3 The test is made with a straight rigid steel wire or rod of .0984 +.002/-0 inch (2.5 +0.05/-0 mm) diameter 
applied with a force of 0.674 Ibf (3 N) ±1 percent. The end of the wire or rod shall be free from burrs and at 
right angles to its length. 

The protection is satisfactory if the wire or rod cannot enter the enclosure. 

4 The test is made with a straight rigid steel wire of 0.0394 +.002/-0 inch (1 +0.05/-0 mm) diameter applied 
with a force of 0.224 Ibf (1 N) ±10 percent. The end of the wire shall be free from burrs and at right angles to 
its length. 

The protection is satisfactory if the wire cannot enter the enclosure. 

5 a. Dust test 

The test is made using equipment incorporating the basic principles shown in Figure 5-2, in which talcum 
powder is maintained in suspension in a suitable closed test chamber. The talcum powder used shall be 
able to pass through a square-meshed sieve having a nominal wire diameter of SO^m and a nominal width 
between wires of 75jim. The amount of talcum powder to be used is 2 kg per cubic meter of the test 
chamber volume. It shall not have been used for more than 20 tests. 

Electrical machines have an enclosure where the normal operating cycle of the machine causes reductions 
in the air pressure within the enclosure in relation to the ambient atmospheric pressure. These reductions 
may be due, for example, to thermal cycling effects (category I). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES Part 5, Page 7 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 

Table 5-3 

TEST AND ACCEPTANCE CONDITIONS FOR FIRST CHARACTERISTIC NUMERAL 

First Characteristic 

Numeral Test and Acceptance Conditions 

For this test the machine is supported inside the test chamber and the pressure inside the machine is 
maintained below atmospheric pressure by a vacuum pump. If the enclosure has a single drain hole, the 
suction connection shall be made to one hole specially provided for the purpose of the test, except if the 
drain hole is intended normally to be closed on site (see 5.3.4). 

The object of the test is to draw into the machine, if possible, at least 80 times the volume of air in the 
enclosure without exceeding an extraction rate of 60 volumes per hour with a suitable depression. In no 
event shall the depression exceed 20 mbar (2kPa) on the manometer shown in Figure 5-2. 

If an extraction rate of 40 to 60 volumes per hour is obtained, the test is stopped after 2 hours. 

If, with a maximum depression of 20 mbar (2 kPa), the extraction rate is less than 40 volumes per hour, the 
test is continued until 80 volumes have been drawn through, or a period of 8 hours has elapsed. 

If it is impracticable to test the complete machine in the test chamber, one of the following procedures shall 
be applied. 

1. Testing of individually enclosed sections of the machine (terminal boxes, slip-ring housings, etc.) 

2. Testing of representative parts of the machine, comprising components such as doors, ventilating 
openings, joints, shaft seals, etc. with the vulnerable parts of the machine, such as terminals, slip-rings, 
etc., in position at the time of testing. 

3. Testing of a smaller machine having the same full scale design details. 

4. Testing under conditions determined by agreement between manufacturer and user. 

In the second and third cases, the volume of air to be drawn through the machine under test is as specified 

for the whole machine in full scale. 

The protection is satisfactory if, on inspection, talcum powder has not accumulated in a quantity or location 
such that, as with any kind of ordinary dust (i.e., dust that is not conductive, combustible, explosive or 
chemically corrosive) it could interfere with the correct operation of the machine. 

b. Wire test 

If the machine is intended to run with open drain holes, these shall be tested in the same manner as the first 
characteristic numeral 4, i.e., using a 0.0394 inch (1 mm) diameter wire. 
6 Test in accordance with 5 a). 

The protection is satisfactory if, on inspection, there is no ingress of talcum powder. 



5.8 TESTS FOR SECOND CHARACTERISTIC NUMERAL 
5.8.1 Test Conditions 

Test conditions for the second characteristic numeral are given in Table 5-4. 

The test shall be conducted with fresh water. During the test, the moisture contained inside the enclosure 
may be partly condensed. The dew which may thus be deposited should not be mistaken for an ingress 
of water. 

For the purpose of the tests, the surface area of the machine shall be calculated with an accuracy of 10 
percent. 

When possible, the machine shall be run at rated speed. This can be achieved by mechanical means or 
by energization. If the machine is energized, adequate safety precautions shall be taken. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 5 Page 8 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



Table 5-4 
TEST CONDITIONS FOR SECOND CHARACTERISTIC NUMERAL 



Second 

Characteristic 

Numeral 


Test conditions 





No test is required. 


1 


The test is made by means of an equipment, the principle of which is shown in Figure 5-3. The rate of 
discharge shall be reasonably uniform over the whole area of the apparatus and shall produce a rainfall of 
between 3 mm and 5 mm of water per minute (in the case of equipment according to Figure 5-3, this 
corresponds to a fall in water level of 3 mm to 5 mm per minute). 

The machine under test is placed in its normal operating position under the dripping equipment, the base of 
which shall be larger than that of the machine. Except for machines designed for wall or ceiling mounting, 
the support for the enclosure under test should be smaller than the base of the enclosure. 

The machine normally fixed to a wall or ceiling is fixed in its normal position of use to a wooden board 
having dimensions that are equal to those of that surface of the machine which is in contact with the wall or 
ceiling when the machine is mounted as in normal use. 

The duration of the test shall be 10 minutes. 


2 


The dripping equipment is the same as that specified for the second characteristic numeral 1 and is 
adjusted to give the same rate of discharge. 

The machine is tested for 2.5 minutes in each of four fixed positions of tilt. These positions are 15 degrees 
either side of the vertical in two mutually perpendicular planes. 

The total duration of the test shall be 10 minutes. 


3 


The test shall be made using equipment such as is shown in Figure 5-4, provided that the dimensions and 
shape of the machine to be tested are such that the radius of the oscillating tube does not exceed 1 m. 
Where this condition cannot be fulfilled, a hand-held spray device, as shown in Figure 5-5, shall be used. 

a. Conditions when using test equipment as shown in Figure 5-4. 

The total flow rate shall be adjusted to an average rate of 0.067 to 0.074 liter/min. per hole multiplied by the 
number of holes. The total flow rate shall be measured with a flowmeter. 

The tube is provided with spray holes over an arc of 60 degrees either side of the center point and shall be 
fixed in a vertical position. The test machine is mounted on a turntable with a vertical axis and is located at 
approximately the center point of the semicircle. 

The minimum duration of the test shall be 10 minutes. 

b. Conditions when using test equipment as shown in Figure 5-5. 

The moving shield shall be in place for this test. 

The water pressure is adjusted to give a delivery rate of 10 ± 0.5 liters/min. (pressure approximately 80-100 
kPa [0.8-1.0 bar]). 

The test duration shall be 1 minute per m 2 of calculated surface area of the machine (excluding any 
mounting surface and cooling fin) with a minimum duration of 5 minutes. 


4 


The conditions for deciding whether the apparatus of Figure 5-4 or that of Figure 5-5 should be used are the 
same as stated for the second characteristic numeral 3. 



a. Using the equipment of Figure 5-4. 

The oscillating tube has holes drilled over the whole 180 degrees of the semicircle. The test duration and 
the total water flow rate are the same as for degree 3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



MG 1-2009 
Part 5, Page 9 



The support for the machine under test shall be perforated so as to avoid acting as a baffle and the 
enclosure shall be sprayed from every direction by oscillating the tube at a rate of 60 degrees/s to the limit 
of its travel in each direction. 

b. Using the equipment of Figure 5-5. 

The moving shield is removed from the spray nozzle and the machine is sprayed from all practicable 
directions. 

Th e rate of water delivery and the spraying time per unit area are the same as for degree 3. 

The test is made by spraying the machine from all practicable directions with a stream of water from a 
standard test nozzle as shown in Figure 5-6. The conditions to be observed are as follows. 

1. Nozzle internal diameter: 6.3 mm 

2. Delivery rate: 1 1 .9 - 1 3.2 liters/min 

3. Water pressure at the nozzle: approximately 30 kPa (0.3 bar) (see Note 1) 

4. Test duration per m 2 of surface area of machine: 1 minute 

5. Minimum test duration: 3 minutes 

6. Distance from nozzle to machine surface: approximately 3 m (see Note 2). (This distance may be reduced if 
necessary to ensure proper wetting when spraying upwards.) 



The test is made by spraying the machine from all practicable directions with a stream of water from a 
standard test nozzle as shown in Figure 5-6. The conditions to be observed are as follows. 

1. Nozzle internal diameter: 12.5 mm 

2. Delivery rate: 100 liters/min. ± 5 percent 

3. Water pressure at the nozzle: approximately 100 kPa (1 bar) (see Note 1) 

4. Test duration per m 2 of surface area of machine: 1 minute 

5. Minimum test duration: 3 minutes 

6. Distance from nozzle to machine surface: approximately 3 m (see Note 2) 



NOTES— 



The test is made by completely immersing the machine in water so that the following conditions are 
satisfied: 

1 . The surface of the water shall be at least 150 mm above the highest point of the machine 

2. The lowest portion of the machine shall be at least 1 m below the surface of the water 

3. The duration of the test shall be at least 30 minutes 

4. The water temperature shall not differ from that of the machine by more than 5°C 

By agreement between manufacturer and user, this test may be replaced by the following procedure: 

The machine should be tested with an inside air pressure of about 10 kPa (0.1 bar). The duration of the test 
is 1 minute The test is deemed satisfactory if no air leaks out during the test. Air leakage may be detected 
either by submersion, the water just covering the machine, or by the application on to it of a solution of soap 
in water. 



The test conditions are subject to agreement between manufacturer and user, but they shall not be less 
severe than those prescribed for degree 7. 



Jlb5 — 

The measurement of the water pressure may be replaced by that of the height to which the spray of the nozzle freely rises: 

Pressure Height 

30 kPa (0.3 bar) 2.5 m 

100kPa(1bar) 8 m 

The distance of the nozzle to the machine under test, for degrees 5 and 6, was set at 3 m for practical reasons; it may be 
reduced in order to test the machine from every direction. 



) Copyright 2009 by the National Electrical Manufacturers Association. 



MG1 " 2009 Section I 

Part 5, Page 10 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



5.8.2 Acceptance Conditions 

After the test in accordance with Table 5-4 has been carried out, the machine shall be inspected for 
ingress of water and subjected to the following verifications and tests. 

5.8.2.1 Allowable Water Leakage 

The amount of water which has entered the machine shall not be capable of interfering with its 
satisfactory operation. The windings and live parts not designed to operate when wet shall not be wet and 
no accumulation of water which could reach them shall occur inside the machine. 

It is, however, permissible for the blades of fans inside rotating machines to be wet and leakage along the 
shaft is allowable if provision is made for drainage of this water. 

5.8.2.2 Post Water Electrical Test 

a. In the case of a test on a machine not running, the machine shall be operated under no-load 
conditions at rated voltage for 15 minutes, then submitted to a high-voltage test, the test voltage 
being 50 percent of the test voltage for a new machine (but not less than 125 percent of the rated 
voltage). 

b. In the case of a test on a running machine, only the high-voltage test is made, in accordance with 
Item a. above. 

The test is deemed satisfactory if these checks show no damage according to Part 3. 

5.9 REQUIREMENTS AND TESTS FOR OPEN WEATHER-PROTECTED MACHINES 

The degree of protection "W" is intended for air-cooled open machines with open circuit cooling, that is, 
machines with cooling systems designated by ICOX to IC3X according to Part 6. 

Weather-protected machines shall be so designed that the ingress of rain, snow, and airborne particles 
into the electrical parts is reduced. 

Other measures providing weather protection (such as encapsulated windings or total enclosure) are not 
designated by "W". 

Machines with degree of protection "W* shall have ventilation passages constructed such that: 

a. At both intake and discharge, high-velocity air and airborne particles are prevented from entering 
the internal passages leading directly to the electrical parts of the machine. 

b. The intake air path, by baffling or use of separate housings, provide at least three abrupt changes 
in direction of the intake air, each of which is at least 90 degrees. 

c. The intake air path shall provide an area of average velocity not exceeding 3 m/s enabling any 
particles to settle. Removable or otherwise easy to clean filters or any other arrangement for the 
separation of particles may be provided instead of a settling chamber. 

The protection of the machine against contact, foreign objects and water shall comply with the conditions 
and tests specified for the stated degree of protection. 

The design of the terminal box shall ensure a degree of protection of at least IP54. 

If necessary, arrangements to provide protection against icing, moisture, corrosion or other abnormal 
conditions shall be made by agreement (e.g. by using anti-condensation heating). 

For verification of weather-protection "W" a study of drawings is generally sufficient. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section! MG 1-2009 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES Part 5, Page 1 1 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



75 



Handle 




NOTES— 

Both joints of this finger may be bent through an angle of 90° +10°/-0°, but in one and the same direction only. 

Dimensions in millimeters. 

Tolerances on dimensions without specific tolerance: 

on angles: +07-10° 
on dimensions: 

up to 25mm: +0/-0.05 mm 

over 25 mm: +0.2 mm 
Material for finger: e.g. heat-treated steel. 

Using the pin and groove solution is only one of the possible approaches in order to limit the bending angle to 90°. For this reason, 
dimensions and tolerances of these details are not given in the drawing. The actual design shall ensure a 90° bending angle with a 
0° to +10° tolerance. 

Figure 5-1 
STANDARD TEST FINGER 

(Reproduced with permission of the IEC which retains the copyright.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 5, Page 12 



Section I 
ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 
OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



S&T- 



/Z> ) t 



Valve 




Circulating pump 



Figure 5-2 
EQUIPMENT TO PROVE PROTECTION AGAINST DUST 

(Reproduced with permission of the IEC which retains the copyright.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



MG 1-2009 
Parts, Page 13 



8 






u u'u u u 




Dimensions in milSrneires 
Key 



—A— 



rainwiOTJtimiL^^ 



vaiammmm!^^ 




the ni2??m 



1 Layers of sand and gravel to regulate flew of water, these layers 
being separated by metallic gauze and blotting paper 

2 Machine under test 



Figure 5-3 
EQUIPMENT TO PROVE PROTECTION AGAINST DRIPPING WATER 

(Reproduced with permission of the I EC which retains the copyright.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Parts, Page 14 



Section I 
ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 
OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



1 000 max. 




IEC 243V2000 



Dimensions in millimetres 



Key 

1 Holes 00.4 

2 Machine under test 

3 Counterweight 



Figure 5-4 
EQUIPMENT TO PROVE PROTECTION AGAINST SPRAYING AND SPLASHING WATER 

SHOWN WITH SPRAYING HOLES 
IN THE CASE OF SECOND CHARACTERISTIC NUMERAL 3 

(Reproduced with permission of the IEC which retains the copyright.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



MG 1-2009 
Parts, Page 15 




EC 2434/2000 



Dimensions in nvHayi sires 
Key 

1 Cock 

2 Pressure gauge 

3 Hose 

4 Moving shield 

5 Spray nozzle 

6 Counterweight 

7 Machine under test 



Moving shield - aluminium 

Sprav nozzle - brass with 

121 holes O0.5: 

1 hole in center 

2 i n n e r c i re I e s o f 1 2 hoi es at 3 p i tc h 
4 outer circles of 24 holes at 15 pitch 



Figure 5-5 

HAND-HELD EQUIPMENT TO PROVE PROTECTION 

AGAINST SPRAYING AND SPLASHING WATER 

(Reproduced with permission of the IEC which retains the copyright.) 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Parts, Page 16 



Section I 
ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 
OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 




!EC 243&2QOQ 



Dimensions in millimetres 

D is 6,3 mm for the tests of table 5 numeral 5 
D is 12.5 mm for the tests of (able 5 numeral 6 



Figure 5-6 
STANDARD NOZZLE FOR HOSE TESTS 

(Reproduced with permission of the IEC which retains the copyright.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



MG 1-2009 
Part 5, Page 17 



Appendix A 
MOST FREQUENTLY USED DEGREES OF PROTECTION FOR ELECTRICAL MACHINES 





Second 

Characteristic 

Numeral 





1 


2 


3 


4 


5 


6 


7 


8 


First 

Characteristic 

Numeral 













































1 








IP12 














2 






IP21 


IP22 


IP23 












3 






















4 












IP44 










5 












IP54 


IP55 









NOTE— The above list comprises the most frequently used degrees of protection, on the international level, in 
accordance with the description given in 5.3 and 5.4. It may be altered or completed for special needs, or according to 
the necessities of national standards. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 5, Page 18 ROTATING ELECTRICAL MACHINES— CLASSIFICATION OF DEGREES 

OF PROTECTION PROVIDED BY ENCLOSURES FOR ROTATING MACHINES 



< This page is intentionally left blank. > 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 6 



<This page is intentionally left blank.: 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) Part 6, Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 6 
ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 

6.1 SCOPE 

This Part identifies the circuit arrangements and the methods of movement of the coolant in rotating 
electrical machines, classifies the methods of cooling and gives a designation system for them. 

The designation of the method of cooling consists of the letters "IC," followed by numerals and letters 
representing the circuit arrangement, the coolant and the method of movement of the coolant. 

A complete designation and a simplified designation are defined. The complete designation system is 
intended for use mainly when the simplified system is not applicable. 

The complete designations, as well as the simplified designations, are illustrated in the tables of 6.7 for 
some of the most frequently used types of rotating machines, together with sketches of particular 
examples. 

6.2 DEFINITIONS 

For the purposes of this part, the following definitions apply. 

6.2.1 Cooling 

A procedure by means of which heat resulting from losses occurring in a machine is given up to a primary 
coolant which may be continuously replaced or may itself be cooled by a secondary coolant in a heat 
exchanger. 

6.2.2 Coolant 

A medium, liquid or gas, by means of which heat is transferred. 

6.2.3 Primary Coolant 

A medium, liquid or gas which, being at a lower temperature than a part of a machine and in contact with 
it, removes heat from that part. 

NOTE — A machine may have more than one primary coolant. 

6.2.4 Secondary Coolant 

A medium, liquid or gas which, being at a lower temperature than the primary coolant, removes the heat 

given up by this primary coolant by means of a heat exchanger or through the external surface of the 

machine. 

NOTE— Each primary coolant in a machine may have its own secondary coolant. 

6.2.5 Final Coolant 

The last coolant to which the heat is transferred. 

NOTE— In some machines the final coolant is also the primary coolant. 

6.2.6 Surrounding Medium 

The medium, liquid or gas, in the environment surrounding the machine. 
NOTE— The coolant may be drawn from and/or be discharged to this environment. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 6, Page 2 ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 

6.2.7 Remote Medium 

A medium, liquid or gas, in an environment remote from the machine and from which a coolant is drawn 
and/or to which it is discharged through inlet and/or outlet pipe or duct, or in which a separate heat 
exchanger may be installed. 

6.2.8 Direct Cooled Winding (Inner Cooled Winding) 

A winding in which the coolant flows through hollow conductors, tubes or channels which form an integral 
part of the winding inside the main insulation. 

6.2.9 Indirect Cooled Winding 

A winding cooled by any method other than that of 6.2.8. 

NOTE— In all cases when "indirect" or "direct" is not stated, an indirect cooled winding is implied. 

6.2.10 Heat Exchanger 

A component intended to transfer heat from one coolant to another while keeping the two coolants 
separate. 

6.2.11 Pipe, Duct 

A passage provided to guide the coolant. 

NOTE-— The term duct is generally used when a channel passes directly through the floor on which the machine is 
mounted. The term pipe is used in all other cases where a coolant is guided outside the machine or heat exchanger. 

6.2.12 Open Circuit 

A circuit in which the final coolant is drawn directly from the surrounding medium or is drawn from a 
remote medium, passes over or through a heat exchanger, and then returns directly to the surrounding 
medium or is discharged to a remote medium. 

NOTE— The final coolant will always flow in an open circuit (see also 6.2.13). 

6.2.13 Closed Circuit 

A circuit in which a coolant is circulated in a closed loop in or through the machine and possibly through a 
heat exchanger, while heat is transferred from this coolant to the next coolant through the surface of the 
machine or in the heat exchanger. 

NOTES 

1— A general cooling system of a machine may consist of one or more successively acting closed circuits and always 
a final open circuit. Each of the primary, secondary and/or final coolants may have its own appropriate circuit. 

2— The different kinds of circuits are stated in Clause 6.4 and in the tables of 6.7. 

6.2.14 Piped or Ducted Circuit 

A circuit in which the coolant is guided either by inlet or outlet pipe or duct, or by both inlet and outlet pipe 
or duct, these serving as separators between the coolant and the surrounding medium. 

NOTE— The circuit may be an open or a closed circuit (see 6.2.12 and 6.2.13). 

6.2.15 Stand-by or Emergency Cooling System 

A cooling system which is provided in addition to the normal cooling system and which is intended to be 
used when the normal cooling system is not available. 

6.2.16 Integral Component 

A component in the coolant circuit which is built into the machine and which can only be replaced by 
partially dismantling the machine. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) Part 6, Page 3 

6.2.17 Machine-Mounted Component 

A component in the coolant circuit which is mounted on the machine and forms part of it but which can be 
replaced without disturbing the main machine. 

6.2.18 Separate Component 

A component in the coolant circuit which is associated with a machine but which is not mounted on or 
integral with the machine. 

NOTE — This component may be located in the surrounding or a remote medium. 

6.2.19 Dependent Circulation Component 

A component in the coolant circuit which for its operation is dependent on (linked with) the rotational 
speed of the rotor of the main machine (e.g. fan or pump on the shaft of the main machine or fan unit or 
pump unit driven by the main machine). 

6.2.20 Independent Circulation Component 

A component in the coolant circuit which for its operation is independent of (not linked with) the rotational 
speed of the rotor of the main machine, (e.g. design with its own drive motor). 

6.3 DESIGNATION SYSTEM 

The designation used for the method of cooling of a machine consists of letters and numerals as stated 
below: 

6.3.1 Arrangement of the IC Code 

The designation system is made up as follows, using the examples IC8A1W7 for complete designation 
and IC81Wfor simplified designation. 

NOTE — The following rule may be applied to distinguish between complete and simplified designations: 

1 — Complete designation can be recognized by the presence (after the letters IC) of three or five numerals and letters 
in the regular sequence - numeral, letter, numeral (letter, numeral). 

Examples: IC3A1, IC4A1A1 or IC9A1W7 

2— A simplified designation has two or three consecutive numerals, or a letter in the final position. 

Examples: IC31, IC411, or IC71W. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 6, Page 4 



Section I 
ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



Complete designation 
Simplified designation 



IC 

IC 



8 
8 



W 
W 



6.3.1.1 Code Letters 

(International Cooling) 



6.3.1.2 Circuit Arrangement 

Designated by a characteristic numeral in accordance with 6.4. 



6.3.1.3 Primary Coolant 

Designated by a characteristic letter in accordance with 6.5. 
Omitted for simplified designation if it is A for air. 

6.3.1 .4 Method of Movement of Primary Coolant 

(higher temperature) 

Designated by a characteristic numeral in accordance with 6.6. 



6.3.1.5 Secondary Coolant 

If applicable, designated by a 
characteristic letter in accordance with 6.5. 
Omitted for simplified designation if it is A for air. 



6.3.1 .6 Method of Movement of Secondary Coolant 

(lower temperature) 

If applicable, designated by a characteristic numeral in accordance with 6.6. Omitted in case of the 

simplified designation if it is 7 with water (W7) for secondary coolant. 

6.3.2 Application of Designations 

The simplified designation should preferably be used (i.e., the complete designation system is intended 
for use mainly when the simplified system is not applicable). 

6.3.3 Designation of Same Circuit Arrangements for Different Parts of a Machine 

Different coolants or methods of movement may be used in different parts of a machine. These shall be 
designated by stating the designations as appropriate after each part of the machine. 

An example for different circuits in rotor and stator is as follows: 

Rotor IC7H1W Stator IC7W5W (simplified) 

Rotor IC7H1W7 Stator IC7W5W7 (complete) 

An example for different circuits in a machine is as follows: 

Generator IC7H1 W Exciter IC75W (simplified) 

Generator IC7H1VW Exciter IC7A5W7 (complete) 

6.3.4 Designation of Different Circuit Arrangements for Different Parts of a Machine 

Different circuit arrangements may be used on different parts of a machine. These shall be designated by 
stating the designations as appropriate after each part of the machine, separated by a stroke (/). 

Example: 

Generator IC81W Exciter IC75W (simplified) 

Generator IC8A1W7 Exciter IC7A5W7 (complete) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section! MG 1-2009 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) Part 6, Page 5 

6.3.5 Designation of Direct Cooled Winding 

In the case of machines with direct cooled (inner cooled) windings, the part of the designation related to 
this circuit shall be put between brackets. 

Example: 

Rotor IC7H1W Stator IC7(W5)W (simplified) 

Rotor IC7H1W7 Stator IC7(W5)W7 (complete) 

6.3.6 Designation of Stand-by or Emergency Cooling Conditions 

Different circuit arrangements may be used depending on stand-by or emergency cooling conditions. 
These shall be designated by the designation for the normal method of cooling, followed by the 
designation of the special cooling system enclosed in brackets, including the words "Emergency" or 
"Stand-by" and the code letters IC. 

Example: 

IC71W (Emergency IC01) (simplified) 

IC7A1W7 (Emergency IC0A1) (complete) 

6.3.7 Combined Designations 

When two or more of the conditions of 6.3.3 to 6.3.6, inclusive, are combined, the appropriate 
designations described above can be applied together. 

6.3.8 Replacement of Characteristic Numerals 

When a characteristic numeral has not yet been determined or is not required to be specified for certain 
application, the omitted numeral shall be replaced by the letter "X." 

Examples: IC3X, IC4XX 

6.3.9 Examples of Designations and Sketches 

In 6.7, the different designations, together with appropriate sketches, are given for some of the most 
commonly used types of rotating machines. 

6.4 CHARACTERISTIC NUMERAL FOR CIRCUIT ARRANGEMENT 

The characteristic numeral following the basic symbol "IC" designates the circuit arrangement (see 
6.3.1.2) for circulating the coolant(s) and for removing heat from the machine in accordance with Table 
6-1. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 6, Page 6 



Section I 
ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



Table 6-1 
CIRCUIT ARRANGEMENT 



Characteristic 
Numeral 



Brief Description 



Definition 



0* 
1* 

2* 



6** 



9**t 



Free circulation 

Inlet pipe or inlet duct 
circulated 

Outlet pipe or outlet duct 
circulated 

Inlet and outlet pipe or 
duct circulated 



Frame surface cooled 



Integral heat exchanger 
(using surrounding 
medium) 

Machine-mounted heat 
exchanger (using 
surrounding medium) 

Integral heat exchanger 
(using remote medium) 

Machine-mounted heat 
exchanger (using 
remote medium) 

Separate heat 
exchanger (using 
surrounding or remote 
medium) 



The coolant is freely drawn directly from the surrounding medium, cools the 

machine, and then freely returns directly to the surrounding medium (open circuit). 

The coolant is drawn from a medium remote from the machine, is guided to the 

machine through an inlet pipe or duct, passes through the machine and returns 

directly to the surrounding medium (open circuit). 

The coolant is drawn directly from the surrounding medium, passes through the 

machine and is then discharged from the machine through an outlet pipe or duct to 

a medium remote from the machine (open circuit). 

The coolant is drawn from a medium remote from the machine, is guided to the 

machine through an inlet pipe or duct, passes through the machine and is then 

discharged from the machine through an outlet pipe or duct to a medium remote 

from the machine (open circuit). 

The primary coolant is circulated in a closed circuit in the machine and gives its 

heat through the external surface of the machine (in addition to the heat transfer via 

the stator core and other heat conducting parts) to the final coolant which is the 

surrounding medium. The surface may be plain or ribbed, with or without an outer 

shell to improve the heat transfer. 

The primary coolant is circulated in a closed circuit and gives its heat via a heat 

exchanger, which is built into and forms an integral part of the machine, to the final 

coolant which is the surrounding medium. 

The primary coolant is circulated in a closed circuit and gives its heat via a heat 

exchanger, which is mounted directly on the machine, to the final coolant which is 

the surrounding medium. 

The primary coolant is circulated in a closed circuit and gives its heat via a heat 

exchanger, which is built into and forms an integral part of the machine, to the 

secondary coolant which is the remote medium. 

The primary coolant is circulated in a closed circuit and gives its heat via a heat 

exchanger, which is mounted directly on the machine, to the secondary coolant 

which is the remote medium. 

The primary coolant is circulated in a closed circuit and gives its heat via a heat 

exchanger, which is separate from the machine, to the secondary coolant which is 

either the surrounding or the remote medium. 



6.5 CHARACTERISTIC LETTERS FOR COOLANT 

6.5.1 The coolant (see 6.3.1.3 and 6.3.1.5) is designated by one of the characteristic letters in 

accordance with Table 6-2. 



* Filters or labyrinths for separating dust, suppressing noise, etc., may be mounted in the frame or ducts. Characteristic numerals 

to 3 also apply to machines where the cooling medium is drawn from the surrounding medium through a heat exchanger in order to 

provide cooler medium than the surrounding medium, or blown out through a heat exchanger to keep the ambient temperature 

lower. 

** The nature of the heat exchanger is not specified (ribbed or plain tubes, etc.). 

t A separate heat exchanger may be installed beside the machine or in a location remote from the machine. A gaseous secondary 

coolant may be the surrounding medium or a remote medium (see also 6.7, Table 6-6). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) Part 6, Page 7 

Table 6-2 
COOLANT 



Characteristic Letter 


Coolant 


A (see 6.5.2) 


Air 


F 


Refrigerant 


H 


Hydrogen 


N 


Nitrogen 


C 


Carbon Dioxide 


W 


Water 


U 


Oil 


S (See 6.5.3) 


Any other coolant 


Y (See 6.5.4) 


Coolant not yet selected 



6.5.2 When the single coolant is air or when in case of two coolants either one or both are air, the 
letter(s) "A" stating the coolant is omitted in the simplified designation. 

6.5.3 For the characteristic letter "S," the coolant shall be identified elsewhere. 

6.5.4 When the coolant is finally selected, the temporarily used letter T shall be replaced by the 
appropriate final characteristic letter. 

6.6 CHARACTERISTIC NUMERAL FOR METHOD OF MOVEMENT 

The characteristic numeral following (in the complete designation) each of the letters stating the coolant 
designates the method of movement of this appropriate coolant (see 6.3.1.4 and 6.3.1.6) in accordance 
with Table 6-3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 6, Page 8 ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 

Table 6-3 
METHOD OF MOVEMENT 

Characteristic Brief 

Numeral Description Definition 

Free convection The coolant is moved by temperature differences. The fanning action of the rotor is 

negligible. 

1 Self-circulation The coolant is moved dependent on the rotational speed of the main machine, either 

by the action of the rotor alone or by means of a component designed for this purpose 
and mounted directly on the rotor of the main machine, or by a fan or pump unit 
mechanically driven by the rotor or the main machine. 

2-4 Reserved for future use. 

5* Integral The coolant is moved by an integral component, the power of which is obtained in 

independent such a way that it is independent of the rotational speed of the main machine, e.g. an 

component internal fan or pump unit driven by its own electric motor. 

6* Machine-mounted The coolant is moved by a component mounted on the machine, the power of which is 

independent obtained in such a way that it is independent of the rotational speed of the main 

component machine, e.g. a machine-mounted fan unit or pump unit driven by its own electric 

motor. 

T Separate and The coolant is moved by a separate electrical or mechanical component not mounted 

independent on the machine and independent of it or is produced by the pressure in the coolant 

component or circulating system, e.g. supplied from a water distribution system, or a gas main under 

coolant system pressure, 
pressure 

8* Relative The movement of the coolant results from relative movement between the machine 

displacement and the coolant, either by moving the machine through the coolant or by flow of the 
surrounding coolant (air or liquid). 

9 All other The movement of the coolant is produced by a method other than defined above and 

components shall be fully described. 



6.7 COMMONLY USED DESIGNATIONS 

Following are simplified and complete designations for some of the most commonly used types of rotating 
electrical machines: 

6.7.1 General Information on the Tables 

In Tables 6-4, 6-5, and 6-6 the columns show the characteristic numerals for circuit arrangements and 
the rows show the characteristic numerals for the method of movement of the coolant. 

Circuit Arrangement Table 

Characteristic numerals 0, 1,2,3 (open circuits using surrounding medium or remote medium) 6-4 

Characteristic numerals 4, 5, 6 (primary circuit closed, secondary circuit open using surrounding medium) 6-5 

Characteristic numerals 7, 8, 9 (primary circuit closed, secondary circuit open and using remote or 6-6 

surrounding medium) 

The sketches show examples with cooling air flowing from non-drive end to drive-end. The air flow may 
be in the opposite direction, or the air inlet may be at both ends with discharge at the center, depending 
on the design of the machine, the arrangement and number of fans, fan units, inlet and outlet pipes or 
ducts. 

The top line of each box gives the simplified designation on the left and the complete designation on the 
right with air and/or water as coolant (see 6.3.2 and 6.5.1). 

Symbols used in sketches: \ 

a. Integral or machine-mounted dependent fan ^ 

b. Independent circulation component . 

c. Duct or pipe, not part of the machine. ' 



* The use of an independent component as a principal source for movement does not exclude the fanning action of the rotor or the 
existence of a supplementary fan mounted directly on the rotor of the main machine. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



MG 1-2009 
Part 6, Page 9 



Table 6-4 
EXAMPLES OF OPEN CIRCUIT USING SURROUNDING OR REMOTE MEDIUM* 



Characteristic numeral for circuit arrangement (See 6.4) 



Free circulation 

(using surrounding 

medium) 



1 

Inlet pipe or inlet 

duct circulated 

(using remote 

medium) 



Outlet pipe or outlet 

duct circulated 

(using surrounding 

medium) 



Inlet and outlet pipe 

or duct circulated 

(using remote 

medium) 



Characteristic 

numeral for method 

of movement of 

coolant 

(see 6.6) 



tcoo 



Free convection 



IC01 



IC0A1 



&■ 



u * r 




IC21 



IC2A1 



IC31 



IC3A1 



£ 



«ft-fp- 



Self-circulation 



«l 



b 



IC05 IC0A5 



rC15 ICIAfi 

4U_ 



<3 



* f J 



L + , 



IC25 IC2A6 



1C35 IC3A5 



-z? — %" 



Circulation by integral 
independent 
component 



IC06 IC0A6 



IC16 IC1A0 



*+~ 



IC26 IC2A6 



IC36 IC3A6 



-?L*=' 



Circulation by machine- 
mounted independent 
component 



IC17 IC1A7 



IC27 1C2A7 




I +• 




Circulation by separate 

and independent 

component or by 

coolant pressure 

system 



(COS ICOAS 



l«a JC3AS 



H 1 



7% 

e 



Circulation by relative 
displacement 



*For arrangement of the IC Codes, see 6.3.1 . 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 6, Page 10 



Section I 
ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



Table 6-5 
EXAMPLES OF PRIMARY CIRCUITS CLOSED, SECONDARY CIRCUITS OPEN USING 

SURROUNDING MEDIUM* 



Characteristic numeral for circuit arrangement 
(See 6.4) 



Free circulation 

cooled (Using 

surrounding 

medium) 



Integral heat 

exchanger (Using 

surrounding 

medium) 



Machine-Mounted 

heat exchanger 

(Using surrounding 

medium) 



Characteristic numeral for method of 
movement (See 6.6) 



of primary coolant 
(See note) 



of secondary 
coolant 



10*10 



IC4A1A0 



IC510 IC5A1A0 



IC810 IC6A1A0 



Free convection 



IC411 IC4A1A1 



IC511 IC5A1A1 



IC811 IC8A1A1 



*& 



-t 



is 



Self-circulation 



Circulation by integral 
independent component 



JC416 IC4A1A6 



IC616 



IC5A1A6 



IC611 IC6A1A1 



H 



J 




■I 



O 



6 

Circulation by machine- 
mounted independent 
component 



Circulation by separate 
and independent 

component or by coolant 
pressure system 



IC410 IC4A1A8 



IC818 IC5A1A8 




IC610 1C6A1A8 



4 



8 

Circulation by relative 
displacement 



*For arrangement of the IC Codes, see 6.3.1 . 

NOTE— The shown examples in this table are related to the movement of the secondary coolant. The characteristic numeral for the 
movement of the primary coolant in this table is assumed to be "1." Obviously, other designs not shown can also be specified by 
means of the IC Code, e.g., design with machine-mounted independent fan unit for primary coolant: IC666 (IC6A6A6) instead of 
IC616(IC6A1A6) 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



MG 1-2009 
Part 6, Page 11 



Table 6-6 
EXAMPLES OF PRIMARY CIRCUITS CLOSED, SECONDARY CIRCUITS OPEN USING REMOTE OR 

SURROUNDING MEDIUM* 



Characteristic numeral for circuit arrangement 
(See 6.4) 



Integral heat 

exchanger 

(Using remote 

medium) 



8 

Machine-mounted 

heat exchanger 

(Using remote 

medium) 



(Secondary 

coolant: gas, 

remote medium or 

surrounding 

medium) 



Characteristic numeral for 

method of movement 

(See 6.6) 



of primary 
coolant 



of 
secondary 

coolant 
(See note) 



IC70W IC7AOW7 



Free convection 



IC71W IC7A1W7 



IC81W ICBA1W7 



IC91W IC9A1W7 



iSl 



«=E 



£} 



IC017 IC9A1A7 




Self-circulation 



1 



1C75W IC7A5W7 



IC85W 1C8ASW7 



f^L 



IC95W IC9A5W7 



& 



IC957 IC8A5A? 



Circulation by 

integral 
independent 
component 



IC76W IC7A6WT 



ICB6W 1C8A6W7 



r 



pSf 



IC9€W JC9A6W7 



& 



IC067 IC9A6A7 

r4- 



m 



f 



6 

Circulation by 
machine-mounted 

independent 
component 



IC97W IC9A7W7 



}£? 



IC677 IC9A7A7 

4- 



M 



Circulation by 
separate and 
independent com- 
ponent or by coolant 
pressure system 



8 

Circulation by 

relative 
displacement 



*For arrangement of the IC Codes, see 6.3.1. 

NOTE— The shown examples in this table are related to the movement of the secondary coolant. The characteristic numeral for the 

movement of the secondary coolant in this table is assumed to be "7." Obviously, other designs not shown can also be specified by 

means of the IC Code, e.g., design with machine-mounted independent pump unit for primary coolant: IC71W6 (IC7A1W6) instead of 

IC71W(IC7A1W7) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 6, Page 12 ROTATING ELECTRICAL MACHINES— METHODS OF COOLING (IC CODE) 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 7 



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Section I MG 1-2009 

MECHANICAL VIBRATION Part 7, Page 1 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 7 
MECHANICAL VIBRATION-MEASUREMENT, EVALUATION AND LIMITS 



7.1 SCOPE 

This standard is applicable to direct-current machines tested with direct-current power and to polyphase 
alternating-current machines tested with sinusoidal power, in frame sizes 42 and larger and at rated 
power up to 100,000 HP or 75 MW, at nominal speeds up to and including 3600 rev/min. 

For vertical and flange-mounting machines, this standard is only applicable to those machines that are 
tested in the intended orientation. 

This standard is not applicable to single-bearing machines, machines mounted in situ, single-phase 
machines, three-phase machines operated on single-phase systems, vertical water power generators, 
permanent magnet generators or to machines coupled to prime movers or driven loads. 

NOTE — For machines measured in situ refer to ISO 10816-3. 

7.2 OBJECT 

This standard establishes the test and measurement conditions of, and fixes the limits for, the level of 
vibration of an electrical machine, when measurements are made on the machine alone in a test area 
under properly controlled conditions. Measurement quantities are the vibration levels (velocity, 
displacement and/or acceleration) at the machine bearing housings and the shaft vibration relative to the 
bearing housings within or near the machine bearings. Shaft vibration measurements are recommended 
only for machines with sleeve bearings and speeds equal to or greater than 1000 rev/min and shall be the 
subject of prior agreement between manufacturer and user with respect to the necessary provisions for 
the installation of the measurement probes. 

7.3 REFERENCES 

Referenced documents used in this Part are, ISO 8821, ISO 7919-1, ISO 10816-3, and IEC 60034-14. 

7.4 MEASUREMENT QUANTITY 

7.4.1 Bearing Housing Vibration 

The criterion adopted for bearing housing vibration is the peak value of the unfiltered vibration velocity in 
inches per second. The greatest value measured at the prescribed measuring points (see 7.7.2) 
characterizes the vibration of the machine. 

7.4.2 Relative Shaft Vibration 

The criterion adopted for relative shaft vibration (relative to the bearing housing) is the peak-to-peak 
vibratory displacement (S p _ p ) in inches in the direction of measurement (see ISO 7919-1). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 7, Page 2 MECHANICAL VIBRATION 



7.5 MEASURING EQUIPMENT 

Equipment used to measure vibration shall be accurate to within ±10 percent of the allowable limit for the 
vibration being measured. 

7.6 MACHINE MOUNTING 

7.6.1 General 

Evaluation of vibration of rotating electrical machines requires measurement of the machines under 
properly determined test conditions to enable reproducible tests and to provide comparable 
measurements. The vibration of an electrical machine is closely linked with the mounting of the machine. 
The choice of the mounting method will be made by the manufacturer. Typically, machines with shaft 
heights of 1 1 inches or less use resilient mounting. 

NOTE— The shaft height of a machine without feet, or a machine with raised feet, or any vertical machine, is to be 
taken as the shaft height of a machine in the same basic frame, but of the horizontal shaft foot-mounting type. 

7.6.2 Resilient Mounting 

Resilient mounting is achieved by suspending the machine on a spring or by mounting it on an elastic 
support (springs, rubber, etc.). 

The vertical natural oscillation frequency of the suspension system and machine should be less than 33 
percent of the frequency corresponding to the lowest speed of the machine under test, as defined in 
7.7.3.3. For an easy determination of the necessary elasticity of the suspension system, see Figure 7-1 . 

The effective mass of the elastic support shall be no greater than 1 percent of that of the machine, to 
reduce the influence of the mass and the moments of inertia of these parts on the vibration level. 

7.6.3 Rigid Mounting 

Rigid mounting is achieved by fastening the machine directly to a massive foundation. 

A massive foundation is one that has a vibration (in any direction or plane) limited, during testing, to 0.02 
in/s peak (0.5 mm/s peak) above any background vibrations. The natural frequencies of the foundation 
should not coincide within ±10 percent of the rotational frequency of the machine, within ±5 percent of two 
times rotational frequency, or within ±5 percent of one- and two-times electrical-line frequency. 

The vibration velocity of the foundation in the horizontal and vertical directions near the machine feet 
should not exceed 25 percent of the maximum velocity at the adjacent bearing in either the horizontal or 
vertical direction at rotational frequency and at twice line frequency (if the latter is being evaluated). 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section 1 

MECHANICAL VIBRATION 



MG 1-2009 
Part 7, Page 3 



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100 



1000 



1200 1800 



3600 



10000 



Test Speed - RPM 



Figure 7-1 
MINIMUM ELASTIC DISPLACEMENT AS A FUNCTION OF NOMINAL TEST SPEED 

7.6.4 Active Environment Determination 

The support systems mentioned in 7.6.2 and 7.6.3 are considered passive, admitting insignificant 
external disturbances to the machine. If the vibration with the machine stationary exceeds 25 percent of 
the value when the machine is running, then an active environment is said to exist. Vibration criteria for 
active support systems are not given in this Part. 



7.7 



CONDITIONS OF MEASUREMENT 



7.7.1 Shaft Key 

For the balancing and measurement of vibration on machines provided with a shaft extension keyway, 
the keyway shall contain a half key. 

A full length rectangular key of half height or a half length key of full height (which should be centered 
axially in the keyway) is acceptable (reference Clause 3.3 of ISO 8821). 



7.7.2 



Measurement Points for Vibration 



7.7.2.1 Bearing Housing 

The location of the measurement points and directions to which the levels of vibration severity apply are 
shown in Figure 7-2 for machines with end-shield bearings and in Figure 7-4 for machines with pedestal 
bearings. Figure 7-3 applies to those machines where measurement positions according to Figure 7-2 
are not possible without disassembly of parts, or where no hub exists. 

7.7.2.2 Shaft 

Non-contacting transducers, if used, shall be installed inside the bearing, measuring directly the relative 
shaft journal displacement, or near the bearing shell when mounting inside is not practical. The preferred 
radial positions are as indicated in Figure 7-5. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 7, Page 4 MECHANICAL VIBRATION 



7.7.3 Operating Conditions 

7.7.3.1 General 

For machines that are bi-directional, the vibration limits apply for both directions of rotation, but need to be 
measured in only one direction. 

Measurement of the vibration shall be made with the machine at no load and uncoupled. 

7.7.3.2 Power Supply 

Alternating current machines shall be run at rated frequency and rated voltage with a virtually sinusoidal 
wave form. The power supply shall provide balanced phase voltages closely approaching a sinusoidal 
waveform. The voltage waveform deviation factor 1 shall not exceed 10 percent. The frequency shall be 
maintained within ±0.5 percent of the value required for the test being conducted, unless otherwise 
specified. Tests shall be performed where the voltage unbalance does not exceed 1 percent. The percent 
voltage unbalance equals 100 times the maximum voltage deviation from the average voltage divided by 
the average voltage. 

Direct current machines shall be supplied with the armature voltage and field current corresponding to the 
speed at which vibration is being measured. Vibration limits are based upon the use of low ripple power 
supply A (see 12.66.2.1) type power sources. Other types of power supplies may be used for testing 
purposes at the discretion of the manufacturer. 

7.7.3.3 Operating Speed 

Unless otherwise specified for machines having more than one fixed speed the limits of this Part shall not 
be exceeded at any operational speed. For machines with a range of speeds, tests shall be performed at 
least at base and top speeds. Series DC motors shall be tested only at rated operating speed. For 
inverter-fed machines, it shall be acceptable to measure the vibration at only the speed corresponding to 
a 60 Hz power supply. 

7.7.4 Vibration Transducer Mounting 

Care should be taken to ensure that a contact between the vibration transducer and the machine surface 
is as specified by the manufacturer of the transducer and does not disturb the vibratory condition of the 
machine under test. The total coupled mass of the transducer assembly shall be less than 2 percent of 
the mass of the machine. 



The deviation factor of a wave is the ratio of the maximum difference between corresponding ordinates of the wave and of the 
equivalent sine wave to the maximum ordinate of the equivalent sine wave when the waves are superposed in such a way as to 
make this maximum difference as small as possible. The equivalent sine wave is defined as having the same frequency and the 
same root mean square value as the wave being tested. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I 

MECHANICAL VIBRATION 



MG 1-2009 
Part 7, Page 5 




*Delete axial direction if not accessible 

Figure 7-2 

PREFERRED POINTS OF MEASUREMENT APPLICABLE TO ONE OR 

BOTH ENDS OF THE MACHINE 




1H 



'Delete axial direction if not accessible 



Figure 7-3 

MEASUREMENT POINTS FOR THOSE ENDS OF MACHINES WHERE MEASUREMENTS PER 

FIGURE 7-2 ARE NOT POSSIBLE WITHOUT DISASSEMBLY OF PARTS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 7, Page 6 



Section I 
MECHANICAL VIBRATION 




Looking 
toward 
the machine 
stator 



*Delete axial direction if not accessible 




Machine 
stator 
this 
side 



777777777/ 



Figure 7-4 
MEASUREMENT POINTS FOR PEDESTAL BEARINGS 



Transducer 




Figure 7-5 
PREFERRED CIRCUMFERENTIAL POSITION OF TRANSDUCERS FOR THE MEASUREMENT OF 

RELATIVE SHAFT DISPLACEMENT 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

MECHANICAL VIBRATION Part 7, Page 7 



7.8 LIMITS OF BEARING HOUSING VIBRATION 

7.8.1 General 

The following limits of vibration are for machines running at no load, uncoupled, and resiliently mounted 
according to paragraph 7.6.1. For machines tested with rigid mounting, these values shall be reduced by 
multiplying them by 0.8. 

Vibration levels shown in the following paragraphs represent internally excited vibration only. Machines as 
installed (in situ) may exhibit higher levels. This is generally caused by misalignment or the influence of the 
driven or driving equipment, including coupling, or a mechanical resonance of the mass of the machine with 
the resilience of the machine or base on which it is mounted. 

Figure 7-6 establishes the limits for bearing housing vibration levels of machines resiliently mounted for both 
unfiltered and filtered measurements. 

For unfiltered vibration the measured velocity level shall not exceed the limit for the appropriate curve on 
Figure 7-6 corresponding to the rotational frequency. 

For filtered vibration the velocity level at each component frequency of the spectrum analysis shall not 
exceed the value for the appropriate curve in Figure 7-6 at that frequency. 

Unfiltered measurements of velocity, displacement, and acceleration may be used in place of a spectrum 
analysis to determine that the filtered vibration levels over the frequency range do not exceed the limits of 
the appropriate curve in Figure 7-6. For example, for the top curve in Figure 7-6 the unfiltered velocity should 
not exceed 0.15 in/s peak (3.8 mm/s), the displacement should not exceed 0.0025 inch (p-p)-(63.5 microns), 
and the acceleration should not exceed 1g (peak). 

NOTE — International Standards specify vibration velocity as rms in mm/s. To obtain an approximate metric rms 
equivalent, multiply the peak vibration in in/s by 18. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 7, Page 8 



Section I 
MECHANICAL VIBRATION 



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Frequency, Hz 



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NOTE — The intersection of constant displacement lines with constant velocity lines occurs at approximately 20 Hz. 
The intersection of constant velocity lines with constant acceleration lines occurs at approximately 400, 700, and 1500 
Hz for limits 0.15, 0.08, and other, respectively. 



Vibration Limit, in/s peak 



Machine Type — General examples 



0.15 

0.08 

0.04 

0.02 
0.01 



Standard industrial motors. 

Motors for commercial/residential use 

Machine tool motors. 

Medium /large motors with special requirements 

Grinding wheel motors. 

Small motors with special requirements. 

Precision spindle and grinder motors. 

Precision motors with special requirements. 



Figure 7-6 
MACHINE VIBRATION LIMITS (RESILIENTLY MOUNTED) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1 - 2009 

MECHANICAL VIBRATION Part 7, Page 9 



7.8.2 Vibration Limits for Standard Machines 

Unfiltered vibration shall not exceed the velocity levels as shown in the top curve of Figure 7-6 for standard 
(no special vibration requirements) machines resiliency mounted. 

For example, the limits at rotational frequency are as shown in Table 7-1 . 

Table 7-1 
UNFILTERED VIBRATION LIMITS 





Rotational 


Velocity, in./s peak 


Speed, rpm 


Frequency, Hz 


(mm/s) 


3600 


60 


0.15(3.8) 


1800 


30 


0.15(3.8) 


1200 


20 


0.15(3.8) 


900 


15 


0.12(3.0) 


720 


12 


0.09 (2.3) 


600 


10 


0.08 (2.0) 



7.8.3 Vibration Limits for Special Machines 

For machines requiring vibration levels lower than given in 7.8.2 for standard machines, recommended limits 
are given in Figure 7-6 for the general types indicated. Machines to which these lower limits apply (e.g., 
0.08, 0.04, 0.02 or 0.01) shall be by agreement between manufacturer and purchaser. 

NOTE— It is not practical to achieve all vibration limits in Figure 7-6 for all machine types in all sizes. 

7.8.4 Vibration Banding for Special Machines 

Banding is a method of dividing the frequency range into frequency bands and applying a vibration limit to 
each band. Banding recognizes that the vibration level at various frequencies is a function of the source of 
excitation (bearings, for example) and is grouped (banded) in multiples of rotational frequency. 

Figure 7-7 demonstrates three examples of banding. Profile 'A' has a band permitting a higher level at 
rotational frequency but with all other bands equivalent to Profile 'B' limits. Profiles *B' and 'C are examples 
of banding limits for machines requiring lower vibration levels. 

Compliance is based on plots from a spectrum analyzer with a resolution of 400 lines or more and a flat 
response over the frequency range being tested in which the peak velocities do not exceed the limits 
specified for the corresponding frequency bands. 

This Part does not specify vibration limits and bands for this procedure. These shall be by agreement 
between the manufacturer and purchaser. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 7, Page 10 



Section I 
MECHANICAL VIBRATION 



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Multiples of Motor Speed 



Figure 7-7 

EXAMPLES OF SPECIAL MACHINE VIBRATION LIMITS 

PEAK VELOCITY BANDING PROFILES 

7.8.5 Twice Line Frequency Vibration of Two Pole Induction Machines 

7.8.5.1 General 

If the unfiltered vibration level of the machine exceeds the unfiltered limit in Figure 7-6 the modulation of 
the unfiltered vibration at twice electrical line frequency can be examined following the procedure in 

7.8.5.2 to determine if the machine is acceptable. 

Mechanical vibration at a frequency equal to twice the electrical line frequency is produced by the 
magnetic field within the airgap of two-pole three-phase AC induction machines. The magnitude of this 
twice electrical line frequency vibration can modulate at a rate equal to the slip frequency of the rotor 
multiplied by the number of poles. This modulation can have an adverse effect on the proper evaluation 
of the level of vibration in the machine when unfiltered measurements are taken. To evaluate the effect of 
this modulation it is generally necessary to monitor the unfiltered vibration of the machine during a 
complete slip cycle (i.e., the time required for one revolution at the slip frequency). AC induction 
machines running at a very low slip value at no load may require 10 minutes or longer for such 
measurements to be completed at each vibration measuring position. 

7.8.5.2 Filtered Vibration 

A filtered measurement of vibration can be performed on a representative sample of a machine design for 
the purpose of determining whether or not that design has a significant level of twice electrical line 
frequency vibration in the machine and to determine if there is any merit to evaluating the magnitude of 
the modulation of the unfiltered vibration following the procedure in 7.8.5.3. 



) Copyright 2009 by the National Electrical Manufacturers Association. 



Section! MG 1-2009 

MECHANICAL VIBRATION Part 7, Page 1 1 



If the filtered twice electrical line frequency component of the vibration of the machine does not exceed 90 
percent of the unfiltered limit in Figure 7-6 then the machine is considered to have failed the vibration test 
and corrective action is required. 

If the filtered twice electrical line frequency component of the vibration of the machine exceeds 90 percent 
of the unfiltered limit in Figure 7-6 then the procedure in 7.8.5.3 may be used to evaluate the modulation 
of the vibration and determine if any machine of that design may be acceptable. 

7.8.5.3 Evaluation of Modulation of Unfiltered Vibration 

The machine is to be rigidly mounted and the unfiltered vibration monitored for a complete slip cycle for 
the purpose of determining the maximum and minimum values of the unfiltered peak vibration over the 
slip cycle. A value of effective vibration velocity is to be determined using the relationship: 



Veff 



i Vmax + V m j n 



2 

where 

V e ff is the effective vibration velocity 
V max is the maximum unfiltered vibration velocity 
v min is the minimum unfiltered peak vibration velocity 

If the level of the effective vibration velocity V eff does not exceed 80 percent of the values in Figure 7-6 
then the machine complies with the vibration requirements of this Part 7. 

7.8.6 Axial Vibration 

The level of axial bearing housing or support vibration depends on the bearing installation, bearing 
function and bearing design, plus uniformity of the rotor and stator cores. Machines designed to carry 
external thrust may be tested without externally applied thrust. In the case of thrust bearing applications, 
axial vibrations correlate with thrust loading and axial stiffness. Axial vibration shall be evaluated per 7.7 
and the limits of Figure 7-6 apply. 

Where bearings have no axial load capability or function, axial vibration of these configurations should be 
judged in the same manner as vibration levels in 7.8.1 and 7.8.2. 

7.9 LIMITS OF RELATIVE SHAFT VIBRATION 

7.9.1 General 

Shaft vibration limits are applicable only when probe mounting for non-contacting proximity probes is 
provided as part of the machine. Proximity probes are sensitive to mechanical and magnetic anomalies of 
the shaft. This is commonly referred to as "electrical and mechanical probe-track runout." The combined 
electrical and mechanical runout of the shaft shall not exceed 0.0005 inch peak-to-peak (6.4 jim peak- 
to-peak) or 25 percent of the vibration displacement limit, whichever is greater. The probe-track runout is 
measured with the rotor at a slow-roll (100-400 rpm) speed, where the mechanical unbalance forces on the 
rotor are negligible. It is preferred that the shaft be rotating on the machine bearings, positioned at running 
axial center (magnetic center), when the runout determinations are made. 

NOTES— 

1 . Special shaft surface preparation (burnishing and degaussing) may be necessary to obtain the required peak-to-peak runout 
readings. 

2. Shop probes may be used for tests when the actual probes are not being supplied with the machine. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 7, Page 12 MECHANICAL VIBRATION 



7.9.2 Standard Machines 

When specified, the limits for the relative shaft vibration of standard machines with sleeve bearings, inclusive 
of electrical and mechanical runout, shall not exceed the limits in Table 7-2. 

Table 7-2 

LIMITS FOR THE UNFILTERED MAXIMUM RELATIVE SHAFT 

DISPLACEMENT (S PP ) FOR STANDARD MACHINES 

Synchronous Maximum Relative Shaft Displacement 

Speed, rpm (Peak-to- Peak) 

1801-3600 0.0028 in. (70 jim) 

<1800 0.0035 in. (90 urn) 

7.9.3 Special Machines 

When specified, the limits for the relative shaft vibration of rigidly mounted special machines with sleeve 
bearings requiring lower relative shaft vibration levels than shown in Table 7-2, inclusive of electrical and 
mechanical runout, shall not exceed the limits in Table 7-3. 

Table 7-3 

LIMITS FOR THE UNFILTERED MAXIMUM RELATIVE SHAFT 

DISPLACEMENT (S PP ) FOR SPECIAL MACHINES 

Synchronous Maximum Relative Shaft Displacement 

Speed, rpm (Peak-to- Peak) 

1801-3600 0.0020 in. (50 urn) 

1201 - 1800 0.0028 in. (70|um) 

<1200 0.0030 in. (75 urn) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 9 



<This page is intentionally left blank > 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— Part 9, Page 1 

SOUND POWER LIMITS AND MEASUREMENT PROCEDURES 



Section I 
GENERAL STANDARDS APPLYING TO ALL MACHINES 

Part 9 

ROTATING ELECTRICAL MACHINES— SOUND POWER LIMITS AND 

MEASUREMENT PROCEDURES 



9.1 SCOPE 

This Part specifies maximum no-load A-weighted sound power levels for factory acceptance testing of 
rotating machines in accordance with this Standard and having the following characteristics: 

a. motors with rated output from 0.5 HP through 5000 HP; 

b. speed not greater than 3600 RPM; 

c. 140 frame size and larger; 

d. enclosures of the ODP, TEFC, or WPII type. 

Sound power levels for motors under load are for guidance only. 

This Part also specifies the method of measurement and the test conditions appropriate for the 
determination of the sound power level of electrical motors. 

Excluded are ac motors supplied by inverters (see Part 31), series wound d.c. motors, generators and 
single-bearing motors. 

9.2 GENERAL 

The limits specified in Tables 9-1 and 9-2 of this Standard are applicable to motors operated at rated 
voltage without load. Usually, load has some influence on noise, which is recognized in Table 9-3 for 
single-speed, three-phase ac induction motors. 

Acoustic quantities can be expressed in sound pressure terms or sound power terms. The use of a sound 
power level, which can be specified independently of the measurement surface and environmental 
conditions, avoids the complications associated with sound pressure levels which require additional data 
to be specified. Sound power levels provide a measure of radiated energy and have advantages in 
acoustic analysis and design. 

Sound pressure levels at a distance from the motor, rather than sound power levels, may be required in 
some applications, such as hearing protection programs. However, this Part is only concerned with the 
physical aspect of noise and expresses limits in terms of sound power level. Guidance is given for 
calculation of sound pressure levels at a distance, derived from the sound power values (see 9.7). In situ 
sound pressure calculations require knowledge of motor size, operating conditions, and the environment 
in which the motor is to be installed. Information for making such calculations taking into account 
environmental factors can be found, if needed, in classical textbooks on acoustics. 

9.3 REFERENCES 

Reference standards are listed in Part 1 of this Standard. 

9.4 METHODS OF MEASUREMENT 

9.4.1 Sound level measurements and calculation of sound power level produced by the motor shall be 
in accordance with either ANSI S12.12, S12.51, S12.53, S12.54, or S12.35, unless one of the methods 
specified in 9.4.2 is used. 
NOTE— An overview of applicable measurement standards is provided in Table 9-4. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section I 

Part 9, Page 2 ROTATING ELECTRICAL MACHINES- 

SOUND POWER LIMITS AND MEASUREMENT PROCEDURES 

9.4.2 The method specified in ANSI S12.56 may be used. 

However, to prove compliance with this standard, unless a correction due to inaccuracy of the 
measurement has already been applied to the values determined by the method in accordance with ANSI 
S12.56, the levels of Tables 9-1 and 9-2 shall be decreased by 2 dB. 

9.4.3 When testing under load conditions, the methods of ANSI S12.12 are preferred. However, other 
| methods are allowed when the connected motor and auxiliary equipment are acoustically isolated or 
I located outside the test environment. 

9.5 TEST CONDITIONS 

9.5.1 Machine Mounting 

Care should be taken to minimize the transmission and the radiation of structure-borne noise from all 
mounting elements, including the foundation. This minimizing may be achieved by the resilient mounting 
of smaller motors. Larger motors can usually only be tested under rigid mounting conditions. If 
practicable, when testing, the motor should be as it would be in normal usage. 

Motors tested under load conditions shall be rigidly mounted. 

9.5.1.1 Resilient mounting 

The natural frequency of the support system and the motor under test shall be lower than 33 percent of 
the frequency corresponding to the lowest rotational speed of the motor. 

9.5.1.2 Rigid Mounting 

The motor shall be rigidly mounted to a surface with dimensions adequate for the motor type. The motor 
shall not be subject to additional mounting stresses from incorrect shimming or fasteners. 

9.5.2 Test Operating Conditions 

The following test conditions shall apply: 

a. The motor shall be operated at rated voltage(s), rated frequency or rated speed(s), and with 
appropriate field current(s), where applicable. These shall be measured with instruments of an 
accuracy of 1 .0% or better. 

1 . The standard load condition shall be no-load. 

2. When required by agreement, the motor may be operated at a load condition. 

b. A motor designed to operate with a vertical axis shall be tested with the axis in a vertical position. 

c. For an ac motor, the waveform and the degree of unbalance of the supply system shall comply 
with the requirements of this Standard. 

NOTE— Any increase in voltage (and current) waveform distortion and unbalance will result in an increase in noise and vibration. 

d. A synchronous motor shall be run with appropriate excitation to obtain unity power factor; 

e. A dc motor suitable for variable speed shall be evaluated at base speed; 

f. A motor designed to operate at two or more discrete speeds shall be tested at each speed; 

g. A motor intended to be reversible shall be operated in both directions unless no difference in the 
sound power level is expected. A unidirectional motor shall be tested in its design direction only. 

h. A dc motor shall be evaluated when connected to a low-ripple Type A power supply. 

9.6 SOUND POWER LEVEL 

9.6.1 The maximum sound power levels specified in Tables 9-1 and 9-2, or adjusted by Table 9-3, relate 
to measurements made in accordance with 9.4. 1 . 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section I MG 1-2009 

ROTATING ELECTRICAL MACHINES— Part 9, Page 3 

SOUND POWER LIMITS AND MEASUREMENT PROCEDURES 

9.6.2 When a motor is tested under the conditions specified in 9.5, the sound power level of the motor 
shall not exceed the relevant value(s) specified as follows: 

I a. For all TEFC, ODP, and WPII motors, other than those specified in 9.6.2b, operating at no-load, 
see Table 9-1 . 

b. For dc motors of ODP construction with outputs from 1 HP through 200 HP, operating at no-load, 
see Table 9-2. 

9.6.3 When a single-speed, three-phase, squirrel-cage, induction motor of ODP, TEFC or WPII 
construction, with outputs from 0.5 HP through 500 HP is tested under rated load, the sound power level 
should not exceed the sum of the values specified in Tables 9-1 and 9-3. 

NOTES 

1 — The limits of Tables 9-1 and 9-2 recognize class 2 accuracy grade levels of measurement uncertainty and production 
variations. See 9.4.2. 

2 — Sound power levels under load conditions are normally higher than those at no-load. Generally, if ventilation noise is 
predominant the change may be small, but if the electromagnetic noise is predominant the change may be significant. 

3 — For dc motors the limits in Tables 9-1 and 9-2 apply to base speed. For other speeds, or where the relationship between 
noise level and load is important, limits should be agreed between the manufacturer and the purchaser. 

9.7 DETERMINATION OF SOUND PRESSURE LEVEL 

No additional measurements are necessary for the determination of sound pressure level, L p , in dB, since 
it can be calculated directly from the sound power level, L W a, in dB, according to the following: 

27rr d 2 1 



Lp^LWA" 1 0^910 

Where: 

L p is the average sound pressure level in a free-field over a reflective plane on a hemispherical 

surface at 1m distance from the motor 
r d = 1 .0m + 0.5 times the maximum linear dimension of the motor in meters 
S = 1.0m 2 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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Section I 

ROTATING ELECTRICAL MACHINES- 
SOUND POWER LIMITS AND MEASUREMENT PROCEDURES 



MG 1-2009 
Part 9, Page 5 



Table 9-2 

MAXIMUM A-WEIGHTED SOUND POWER LEVELS L WA (dB) OF 

DRIP-PROOF INDUSTRIAL DIRECT-CURRENT MOTORS, AT NO-LOAD 



Rated Power, P N 


Base Speed, Rpm 


HP 


2500 


1750 


1150 


850 




1 


81 


72 


63 


60 




1.5 


81 


72 


63 


60 




2 


81 


72 


64 


61 




3 


82 


72 


66 


62 




5 


84 


75 


68 


66 




7.5 


86 


77 


71 


69 




10 


88 


79 


73 


71 




15 


90 


82 


77 


74 




20 


92 


84 


79 


75 




25 


94 


86 


81 


77 




30 


95 


88 


82 


78 




40 


96 


90 


84 


79 




50 


-- 


91 


85 


80 




60 


-- 


92 


86 


81 




75 


- 


93 


87 


82 




100 


.. 


94 


88 


83 




125 


- 


95 


88 


83 




150 


-- 


95 


89 


84 




200 


-- 


96 


90 


85 





Table 9-3 

INCREMENTAL EXPECTED INCREASE OVER NO-LOAD CONDITION, IN A-WEIGHTED 

SOUND POWER LEVELS AL WA (dB) , FOR RATED LOAD CONDITION FOR SINGLE-SPEED, 

THREE-PHASE, SQUIRREL-CAGE, INDUCTION MOTORS 



Rated Output, P N 










HP 


2 Pole 


4 Pole 


6 Pole 


8 Pole 


1.0<P N < 15 


2 


5 


7 


8 


15<P N <50 


2 


4 


6 


7 


50 < P N < 150 


2 


3 


5 


6 


150<P N <500 


2 


3 


4 


5 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 
Part 10 



<This page is intentionally left blank > 



Section II 
RATINGS- 



-AC SMALL AND MEDIUM MOTORS 



MG 1-2009 
Part 10, Page 1 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 10 
RATINGS— AC SMALL AND MEDIUM MOTORS 



10.0 



SCOPE 



The standards in this Part 10 of Section II cover alternating-current motors up to and including the ratings 
built in frames corresponding to the continuous open-type ratings given in the table below. 





Motors 










Squirrel-Cage 


Motors, Synchronous, Hp 


Synchronous 


and Wound 




Power Factor 




Speed 


Rotor, Hp 


Unity 




0.8 


3600 


500 


500 




400 


1800 


500 


500 




400 


1200 


350 


350 




300 


900 


250 


250 




200 


720 


200 


200 




150 


600 


150 


150 




125 


514 


125 


125 




100 



10.30 VOLTAGES 

a. Universal motors— 1 15 and 230 volts 

b. Single-phase motors 

1 . 60 hertz— 1 15, 200, and 230 volts 

2. 50 hertz— 110 and 220 volts 

c. Polyphase motors 

1. 60 hertz— 115*, 200, 230, 460, 575, 2300, 4000, 4600, and 6600 volts 

2. Three phase, 50 hertz - 220 and 380 volts 

NOTE— It is not practical to build motors of all horsepower ratings for all of the standard voltages. 
*Applies only to motors rated 15 horsepower and smaller. 

10.31 FREQUENCIES 

10.31.1 Alternating-Current Motors 

The frequency shall be 50 and 60 hertz. 

10.31.2 Universal Motors 

The frequency shall be 60 hertz/direct-current. 

NOTE— Universal motors will operate successfully on all frequencies below 60 hertz and on direct-current. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 2 



Section II 
RATINGS— AC SMALL AND MEDIUM MOTORS 



Table 10-1 
HORSEPOWER AND SPEED RATINGS, SMALL INDUCTION MOTORS 





All Motors Except Shaded-Pole 
and Permanent-Split Capacitor 


Permanent-Split 

Capacitor 

Motors 


All Motors Except Shaded- 
Pole and Permanent-Sptit 
Capacitor 


Permanent- 
Split 
Capacitor 


Hp 


60-Hertz 

Synchronous 

Rpm 


Approximate 

Rpm at 
Rated Load 


50-Hertz 

Synchronous 

Rpm 


Approximate 

Rpm at 
Rated Load 


1,1.5,2,3,5,7.5, 10, 


3600 


3450 






3000 


2850 




15,25, and 35 
millihorsepower 


1800 
1200 
900 


1725 
1140 






1500 

1000 


1425 
950 




1/20,1/12, and 1/8 


3600 


3450 






3000 


2850 




horsepower 


1800 


1725 






1500 


1425 






1200 


1140 






1000 


950 






900 


850 












1/6, 1/4, and 1/3 


3600 


3450 






3000 


2850 




horsepower 


1800 


1725 






1500 


1425 






1200 


1140 






1000 


950 






900 


850 












1/2 horsepower 


3600 


3450 


3250 


3000 


2850 


2700 




1800 


1725 


1625 


1500 


1425 


1350 




1200 


1140 


1075 


1000 


950 


900 


3/4 horsepower 


3600 


3450 


3250 


3000 


2850 


2700 




1800 


1725 


1625 


1500 


1425 


1350 


1 horsepower 


3600 


3450 


3250 


3000 


2850 


2700 



10.32 HORSEPOWER AND SPEED RATINGS 



10.32.1 Small Induction Motors, Except Permanent-Split Capacitor Motors Rated 1/3 Horsepower 
and Smaller and Shaded-Pole Motors 

Typical horsepower and speed ratings for small induction motors rated 115, 200, and 230 volts single- 
phase and 115, 200, 1 and 230 volts polyphase are given in Table 10-1 . 

10.32.2 Small Induction Motors, Permanent-Split Capacitor Motors Rated 1/3 Horsepower and 
Smaller and Shaded-Pole Motors 

Typical horsepower and speed ratings for small induction motors rated 115, 200, and 230 volts single- 
phase are given in Table 10-2. 



1 Applies to 60-Hertz circuits only 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

RATINGS— AC SMALL AND MEDIUM MOTORS 



MG 1-2009 
Part 10, Page 3 



Table 10-2 
HORSEPOWER AND SPEED RATINGS, PERMANENT-SPLIT CAPACITOR AND SHADED POLE MOTORS 







Permanent-Split Capacitor Motors 






Hp 


60-Hertz Synchronous 
Rpm 


Approximate Rpm at 
Rated Load 


50-Hertz synchronous 
Rpm 


Approximate Rpm at 
Rated Load 


1,1.25, 1.5,2,2.5,3,4, 

5,6,8, 10,12.5,16,20, 

25, 30, and 40 

millihorsepower 


3600 
1800 
1200 
900 




3000 

1550 
1050 
800 




3000 
1500 
1000 


2500 
1300 
875 


1/20, 1/15, 1/12, 1/10, 

1/8, 1/6, 1/5, 1/4, and 

1/3 horsepower 


3600 
1800 
1200 
900 




3250 
1625 
1075 
825 




3000 
1500 
1000 


2700 
1350 
900 


Shaded-Pole Motors 




60-Hertz Synchronous 
Rpm 


Approximate Rpm at 
Rated Load 


50-Hertz Synchronous 
Rpm 


Approximate Rpm at 
Rated Load 


1, 1.25, 1.5,2,2.5,3,4, 

5,6,8, 10, 12.5, 16,20, 

25, 30, and 40 

millihorsepower 


1800 
1200 

900 




1550 
1050 
800 




1500 
1000 


1300 
875 


1/20, 1/15, 1/12, 1/10, 

1/8, 1/6, 1/5, and 1/4 

horsepower 


1800 
1200 

900 




1550 
1050 
800 




1500 
1000 


1300 
875 



10.32.3 Single-Phase Medium Motors 

The horsepower and synchronous speed ratings of single-phase medium motors rated 115, 200, and 230 
volts shall be as shown in Table 10-3. 

Table 10-3 
HORSEPOWER AND SPEED RATINGS, MEDIUM MOTORS 







60-Hertz 






50-Hertz 




Hp 




Synchronous Rpm 






Synchronous Rpm 




1/2 








900 






1000 


750 


3/4 






1200 


900 




1500 


1000 


750 


1 




1800 


1200 


900 


3000 


1500 


1000 


750 


1-1/2 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 


2 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 


3 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 


5 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 


7-1/2 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 


10 


3600 


1800 


1200 


900 


3000 


1500 


1000 


750 



10.32.4 Polyphase Medium Induction Motors 

The horsepower and synchronous speed ratings of polyphase medium induction motors shall be as 
shown in Table 10-4. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 4 



Section II 
RATINGS— AC SMALL AND MEDIUM MOTORS 



Table 10-4* 
HORSEPOWER AND SPEED RATINGS, POLYPHASE MEDIUM INDUCTION MOTORS 











60-Hertz 










50-Hertz 




Hp 






Synchronous Rpm 








Synchronous Rpm 




1/2 








900 


720 


600 


514 








750 


3/4 






1200 


900 


720 


600 


514 






1000 


750 


1 




1800 


1200 


900 


720 


600 


514 




1500 


1000 


750 


1-1/2 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


2 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


3 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


5 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


7-1/2 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


10 


3600* 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


15 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


20 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


25 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


30 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


40 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


50 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


60 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


75 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


100 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


125 


3600** 


1800 


1200 


900 


720 


600 


514 


3000 


1500 


1000 


750 


150 


3600** 


1800 


1200 


900 


720 


600 




3000 


1500 


1000 


750 


200 


3600** 


1800 


1200 


900 


720 






3000 


1500 


1000 


750 


250 


3600** 


1800 


1200 


900 








3000 


1500 


1000 


750 


300 


3600** 


1800 


1200 










3000 


1500 


1000 




350 


3600** 


1800 


1200 










3000 


1500 


1000 




400 


3600** 


1800 












3000 


1500 






450 


3600** 


1800 












3000 


1500 






500 


3600** 


1800 












3000 


1500 







*For frame assignments, see Part 13. 
**Applies to squirrel-cage motors only. 

10.32.5 Universal Motors 

Horsepower ratings shall be 10, 15, 25, and 35 millihorsepower and 1/20, 1/12, 1/8, 1/6, 1/4, 1/3, 1/2, 3/4, 
and 1 horsepower at a rated speed of 5000 rpm or above. 

NOTE— At speeds less than 5000 rpm, there will be a marked difference in performance characteristics between 
operation on alternating-current and operation on direct-current. 

10.33 HORSEPOWER RATINGS OF MULTISPEED MOTORS 

The horsepower rating of multispeed motors shall be selected as follows: 

1 0.33.1 Constant Horsepower 

The horsepower rating for each rated speed shall be selected from 10.32. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

RATINGS— AC SMALL AND MEDIUM MOTORS Part 10, Page 5 



1 0.33.2 Constant Torque 

The horsepower rating for the highest rated speed shall be selected from 10.32. The horsepower rating 
for each lower speed shall be determined by multiplying the horsepower rating at the highest speed by 
the ratio of the lower synchronous speed to the highest synchronous speed. 

1 0.33.3 Variable Torque 

The horsepower rating for the highest rated speed shall be selected from 10.32. The horsepower rating 
for each lower speed shall be determined by multiplying the horsepower rating at the highest speed by 
the square of the ratio of the synchronous speed to the highest synchronous speed. 

10.34 BASIS OF HORSEPOWER RATING 

10.34.1 Basis of Rating 

The horsepower rating of a small or medium single-phase induction motor is based upon breakdown 
torque (see 1 .51). The value of breakdown torque to be expected by the user for any horsepower and 
speed shall fall within the range given in Tables 10-5 and 10-6. 

10.34.2 Temperature 

The breakdown torque which determines the horsepower rating is that obtained in a test when the 
temperature of the winding and other parts of the machine are at approximately 25°C at the start of the 
test. 

10.34.3 Minimum Breakdown Torque 

The minimum value of breakdown torque obtained in the manufacture of any design will determine the 
rating of that design. Tolerances in manufacturing will result in individual motors having breakdown torque 
from 100 percent to approximately 115 percent (125 percent for motors rated millihorsepower and for all 
shaded-pole motors) of the value on which the rating is based, but this excess torque shall not be relied 
upon by the user in applying the motor to its load. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 6 



Section II 
RATINGS— AC SMALL AND MEDIUM MOTORS 



Table 10-5*t 
BREAKDOWN TORQUE FOR INDUCTION MOTORS, EXCEPT SHADED-POLE AND PERMANENT-SPLIT 

CAPACITOR MOTORS 



60 


50 


60 


50 


60 


50 


60 


50 




Frequencies, Hertz 


3600 


3000 


1800 


1500 


1200 


1000 


900 


750 




Synchronous 
Speeds, Rpm 




















Small Motors, 


3450** 


2850** 


1725** 


1425** 


1140** 


950** 


850** 




Hp 


Nominal Speeds, 
Rpm 


0.35-0.55 


0.42-0.66 


0.7-1.1 


0.85-1.3 


1.1-1.65 








Millihp 

1 


The figures at the left 
are for motors rated 


0.55-0.7 

0.7-1.1 
1.1-1.8 


0.66-0.85 
0.85-1.3 
1.3-2.2 


1.1-1.45 
1.45-2.2 
2.2-3.6 


1.3-1.75 
1.75-2.6 
2.6-4.3 


1.65-2.2 
2.2-3.3 
3.3-5.4 










1.5 

2 

3 


less than 1/20 

horsepower. 

Breakdown torques in 

oz-in. 


1.8-27 


2.2-3.2 


3.6-5.4 


4.3-6.6 


5.4-8.1 










5 




2.7-3.6 


3.2-4.3 


5.4-7.2 


6.6-8.6 


8.1-11 










7.5 




3.6-5.5 


4.3-6.6 


7.2-11 


8.6-13 


11-17 










10 




5.5-9.5 


6.6-11.4 


11-19 


13-23 


17-29 










15 




9.5-15 


11.4-18 


19-30 


23-36 


29-46 










25 




15-24 


18-28.8 


30-48 


36-57.6 


46-72 










35 




2.0-3.7 


2.4-4.4 


4.0-7.1 


4.8-8.5 


6.0-10.4 


7.2-12.4 


8.0-13.5 




Hp 

1/20 


The figures at left are 
for small motors. 


3.7-6.0 


4.4-7.2 


7.1-11.5 


8.5-13.8 


10.4-16.5 


12.4-19.8 


13.5-21.5 




1/12 


Breakdown torques in 


6.0-8.7 


7.2-10.5 


11.5-16.5 


13.8-19.8 


16.5-24.1 


19.8-28.9 


21.5-31.5 




1/8 


oz-ft. 


8.7-11.5 


10.5-13.8 


16.5-21.5 


19.8-25.8 


24.1-31.5 


28.9-37.8 


31.5-40.5 




1/6 




11.5-16.5 


13.8-19.8 I 


21.5-31.5 


25.8-37.8 


31.5-44.0 


37.8-53.0 


40.5-58.0 




1/4 




16.5-21.5 


19.8-25.8 
25.8-37.8 
37.8-53.0 
53.0-69.5 


31.5-40.5 
40.5-58.0 
58.0-82.5 


37.8-48.5 
48.5-69.5 
69.5-99.0 


44.0-58.0 
58.0-82.5 


53.0-69.5 
69.5-99.0 


58.0-77.0 




1/3 




21.5-31.5 


tt 
tt 
tt 
tt 




1/2 

3/4 

1 

1-1/2 




31 .5-44.0 


5.16-6.9 
6.9-9.2 
9.2-13.8 


tt 
tt 
tt 


The figures at left are 


44.0-58.0 


5.16-6.8 
6.8-10.1 


6.19-8.2 
8.2-12.1 


for medium motors. 

Breakdown torques in 

Ib-ft. 


3.6-4.6 


4.3-5.5 


4.6-6.0 


5.5-7.2 


10.1-13.0 


12.1-15.6 


13.8-18.0 


tt 


tt 




2 




6.0-8.6 


7.2-10.2 


13.0-19.0 


15.6-22.8 


18.0-25.8 


tt 


tt 




3 




8.6-13.5 


10.2-16.2 


19.0-30.0 


22.8-36.0 


25.8-40.5 


tt 


tt 




5 




13.5-20.0 


16.2-24.0 


30.0-45.0 


36.0-54.0 


40.5-60.0 


tt 


tt 




7-1/2 




20.0-27.0 


24.0--32.4 


45.0-60.0 


54.0-72.0 


tt 


tt 


tt 




10 





**These approximate full-load speeds apply only for small motor ratings. 

fThe horsepower ratings of motors designed to operate on two or more frequencies shall be determined by the torque at the highest rated 
frequency. 

ttThese are ratings for which no torque values have been established. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 
RATINGS- 



-AC SMALL AND MEDIUM MOTORS 



MG 1-2009 
Part 10, Page 7 



Table 10-6*t 
BREAKDOWN TORQUE FOR SHADED-POLE AND PERMANENT-SPLIT CAPACITOR MOTORS FOR FAN 

AND PUMP APPLICATIONS 
(For permanent-split capacitor hermetic motors, see 18.7) 



60 


50 


60 


50 


60 




Frequencies, Hertz 


1800 


1500 


1200 


1000 


900 




Synchronous Speeds, 
Rpm 


* See 10.32.1 and 10.32.2. 


Hp 


Small Motors, 

Approximate Full-Load 

Speeds, Rpm 












Millihp 




0.89-1.1 


1.1-1.3 


1.3-1.6 


1.6-1.9 


1.7-2.1 


1 




1.1-1.4 


1.3-1.7 


1.6-2.1 


1.9-2.5 


2.1-2.7 


1.25 




1.4-1.7 


1.7-2.0 


2.1-2.5 


2.5-3.0 


2.7-3.3 


1.5 




1.7-2.1 


2.0-2.5 


2.5-3.1 


3.0-3.7 


3.3-4.1 


2 




2.1-2.6 


2.5-3.1 


3.1-3.8 


3.7-4.6 


4.1-5.0 


2.5 




2.6-3.2 


3.1-3.8 


3.8-4.7 


4.6-5.7 


5.0-6.2 


3 




3.2-4.0 


3.8-4.8 


4.7-5.9 


5.7-7.1 


6.2-7.8 


4 




4.0-4.9 


4.8-5.8 


5.9-7.2 


7.1-8.7 


7.8-9.5 


5 




4.9-6.2 
6.2-7.7 


5.8-7.4 
7.4-9.2 


7.2-9.2 

9.2-11.4 


8.7-11.0 
11.0-13.6 


9.5-12.0 
12.0-14.9 


6 
8 


The figures at left are 
breakdown torques in oz-in. 


7.7-9.6 


9.2-11.4 


11.4-14.2 


13.6-17.0 


14.9-18.6 


10 




9.6-12.3 


11.4-14.7 


14.2-18.2 


17.0-218 


18.6-23.8 


12.5 




12.3-15.3 


14.7-18.2 


18.2-22.6 


21.8-27.1 


23.8-29.6 


16 




15.3-19.1 


18.2-22.8 


22.6-28.2 


27.1-33.8 


29.6-37.0 


20 




19.1-23.9 


22.8-28.5 


28.2-35.3 


33.8-42.3 


37.0-46.3 


25 




23.9-30.4 


28.5-36.3 


35.3-44.9 


42.3-53.9 


46.3-58.9 


30 




30.4-38.2 


36.3-45.6 


44.9-56.4 


53.9-68.4 


58.9-74.4 


40 














HP 




3.20-4.13 


3.8-4.92 


4.70-6.09 


5.70-7.31 


6.20-8.00 


1/20 




4.13-5.23 


4.92-6.23 


6.09-7.72 


7.31-9.26 


8.00-10.1 


1/15 




5.23-6.39 


6.23-7.61 


7.72-9.42 


9.26-11.3 


10.1-12.4 


1/12 




6.39-8.00 


7.61-9.54 


9.42-11.8 


11.3-14.2 


12.4-15.5 


1/10 




8.00-10.4 
10.4-12.7 


9.54-12.4 
12.4-15.1 


11.8-15.3 
15.3-18.8 


14.2-18.4 
18.4-22.5 


15.5-20.1 
20.1-24.6 


1/8 
1/6 


The figures at left are 
breakdown torques in oz-ft. 


12.7-16.0 


15.1-19.1 


18.8-23.6 


22.5-28.3 


24.6-31.0 


1/5 




16.0-21.0 


19.1-25.4 


23.6-31.5 


28.3-37.6 


31.0-41.0 


1/4 




21.0-31.5 


25.4-37.7 
37.7-57.3 
57.3-76.5 


31.5-47.0 
47.0-70.8 


37.6-56.5 
56.5-84.8 


41.0-61.0 


1/3 




31.5-47.5 


3.81-5.81 
5.81-7.62 

7.62-11.6 


1/2 

3/4 

1 


The figures at left are 


47.5-63.5 


4.42-5.88 
5.88-8.88 


5.30-7.06 

7.06-10.6 


breakdown torques in Ib-ft. 


3.97-5.94 


4.78-7.06 




5.94-7.88 


7.06-9.56 


8.88-11.8 


10.6-14.1 


11.6-15.2 


1-1/2 





*The breakdown torque range includes the higher figure down to, but not including, 

fThe horsepower rating of motors designed to operate on two or more frequencies 
rated frequency. 



the lower figure. 

shall be determined by the torque at the highest 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 8 



Section II 
RATINGS— AC SMALL AND MEDIUM MOTORS 



10.35 SECONDARY DATA FOR WOUND-ROTOR MOTORS 



Hp 


Secondary Volts* 


Maximum 

Secondary 

Amperes 


Hp 


Secondary Volts* 


Maximum 
Secondary 
Amperes 


1 


90 


6 


25 


220 


60 


1!4 


110 


7.3 


30 


240 


65 


2 


120 


8.4 


40 


315 


60 


3 


145 


10 


50 


350 


67 


5 


140 


19 


60 


375 


74 


7% 


165 


23 


75 


385 


90 


10 


195 


26.5 


100 


360 


130 


15 


240 


32.5 


125 


385 


150 


20 


265 


38 


150 


380 


185 



*Toierance - plus or minus 10 percent. 

10.36 TIME RATINGS FOR SINGLE-PHASE AND POLYPHASE INDUCTION MOTORS 

The time ratings for single-phase and polyphase induction motors shall be 5, 15, 30 and 60 minutes and 
continuous. 

All short-time ratings are based upon a corresponding short-time load test which shall commence only 
when the winding and other parts of the machine are within 5°C of the ambient temperature at the time of 
the starting of the test. 

1 0.37 CODE LETTERS (FOR LOCKED-ROTOR KVA) 

10.37.1 Nameplate Marking 

When the nameplate of an alternating-current motor is marked to show the locked-rotor kVA per 
horsepower, it shall be marked with the caption "Code" followed by a letter selected from the table in 
10.37.2. 

10.37.2 Letter Designation 

The letter designations for locked-rotor kVA per horsepower as measured at full voltage and rated 
frequency are as follows: 



Letter Designation 


kVA 


per Horsepower* 


Letter Designation 


kVA 


per Horsepower* 


A 




0.00-3.15 


K 




8.0-9.0 


B 




3.15-3.55 


L 




9.0-10.0 


C 




3.55-4.0 


M 




10.0-11.2 


D 




4.0-4.5 


N 




11.2-12.5 


E 




4.5-5.0 


P 




12.5-14.0 


F 




5.0-5.6 


R 




14.0-16.0 


G 




5.6-6.3 


S 




16.0-18.0 


H 




6.3-7.1 


T 




18.0-20.0 


J 




7.1-8.0 


U 




20.0-22.4 








V 




22.4-and up 



*Locked kVA per horsepower range includes the lower figure up to, but not including, the higher figure. For example, 3.14 is 
designated by letter A and 3.15 by letter B. 

10.37.3 Multispeed Motors 

Multispeed motors shall be marked with the code letter designating the locked-rotor kVA per horsepower 
for the highest speed at which the motor can be started, except constant-horsepower motors which shall 
be marked with the code letter for the speed giving the highest locked-rotor kVA per horsepower. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

RATINGS-AC SMALL AND MEDIUM MOTORS Part 1 0, Page 9 

10.37.4 Single-Speed Motors 

Single-speed motors starting on Y connection and running on delta connection shall be marked with a 
code letter corresponding to the locked-rotor kVA per horsepower for the Y connection. 

10.37.5 Broad- or Dual-Voltage Motors 

Broad- or dual-voltage motors which have a different locked-rotor kVA per horsepower on the different 
voltages shall be marked with the code letter for the voltage giving the highest locked-rotor kVA per 
horsepower. 

1 0.37.6 Dual-Frequency Motors 

Motors with 60- and 50-hertz ratings shall be marked with a code letter designating the locked-rotor kVA 
per horsepower on 60-hertz. 

10.37.7 Part-Winding-Start Motors 

Part-winding-start motors shall be marked with a code letter designating the locked-rotor kVA per 
horsepower that is based upon the iocked-rotor current for the full winding of the motor. 

10.38 NAMEPLATE TEMPERATURE RATINGS FOR ALTERNATING-CURRENT SMALL AND 
UNIVERSAL MOTORS 

Alternating-current motors shall be rated on the basis of a maximum ambient temperature and the 
insulation system class. 

The rated value of the maximum ambient temperature shall be 40°C unless otherwise specified, and the 
insulation system shall be Class A, B, F, or H. All such ratings are based upon a rated load test with 
temperature rise values (measured by either method when two methods are listed) not exceeding those 
shown for the designated class of insulation system in the appropriate temperature rise table in 12.43. 
Ratings of alternating-current motors for any other value of maximum ambient temperature shall be 
based on temperature rise values as calculated in accordance with 12.42.3. 

10.39 NAMEPLATE MARKING FOR ALTERNATING-CURRENT SMALL AND UNIVERSAL 
MOTORS 1 

The following information shall be given on all nameplates. For motors with dual ratings, see 10.39.5. For 
abbreviations, see 1.79. For some examples of additional information that may be included on the 
nameplate see 1.70.2. 

10.39.1 Alternating-Current Single-Phase and Polyphase Squirrel-Cage Motors, Except Those 
Included in 10.39.2, 10.39.3, and 10.39.4 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Maximum ambient temperature for which motor is designed (see Note 1 of 12.43.1) 

e. Insulation system designation. (If stator and rotor use different classes of insulation systems, both 
insulation system designations shall be given on the nameplate, that for stator being given first.) 

f. Rpm at full load 2 

g. Frequency 

h. Number of phases 

i. Voltage 

j. Full-load amperes 



1 When air flow is required over the motor from the driven equipment in order to have the motor conform to temperature rise 
standards, "air over" shall appear on the nameplate. When the heat dissipating characteristics of the driven equipment, other than 
air flow, are required in order to have the motor conform to temperature rise standards, "auxiliary cooling" shall appear on the 
nameplate. 

2 This speed is the approximate rpm at rated load (see 10.32.1 and 10.32.2). 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section tl 

Part 10, Page 10 RATINGS— AC SMALL AND MEDIUM MOTORS 

k. Locked-rotor amperes or code letter for locked-rotor kVA per horsepower for motors 1/2 

horsepower or larger (see 10.37) 
I. For motors equipped with thermal protection, the words 'thermally protected" and, for motors rated 

more than 1 horsepower, a type number (see 12.58) (For their own convenience, motor 

manufacturers shall be permitted to use letters, but not numbers, preceding or following the words 

"thermally protected" for other identification purposes.) 

10.39.2 Motors Rated Less Than 1/20 Horsepower 

a. Manufacturer's type and frame designation 

b. Power output 

c. Full-load speed 1 

d. Voltage rating 

e. Frequency 

f. Number of phases-polyphase only (this shall be permitted to be designated by a number showing 
the number of phases following the frequency). 

g. The words "thermally protected" for motors equipped with a thermal protector 2 (see 1 .72 and 1 .73) 
(For their own convenience, motor manufacturers shall be permitted to use letters, but not 
numbers, preceding or following the words "thermally protected" for other identification purposes.) 
Thermally-protected motors rated 100 watts or less and complying with 430-32(c)(2) of the 
National Electrical Code, shall be permitted to use the abbreviated making, "T.P." 

h. The words "impedance protected" for motors with sufficient impedance within the motors so that 
they are protected from the dangerous overheating due to overload or failure to start. Impedance- 
protected motors rated 100 watts or less and complying with 430-32(c)(4) of the National 
Electrical Code, shall be permitted to use the abbreviated marking, "Z.P." 

1 0.39.3 Universal Motors 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Rpm at full load 

e. Voltage 

f. Full-load amperes (on 60-hertz) 

g. Frequency (60/dc is recommended form) 

10.39.4 Motors Intended for Assembly in a Device Having its Own Markings 

a. Voltage rating 

b. Frequency 

c. Number of phases-polyphase only (this shall be permitted to be designated by a number showing 
the number of phases following the frequency) 

1 0.39.5 Motors for Dual Voltage 

a. Broad Voltage (no reconnection of motor leads) 

1 . Use dash between voltages (i.e., 200-300) 

b. Dual Voltage (reconnection of motor leads) 

1. Use slash between voltages (i.e., 230/460) 

2. Use slash between amperes (i.e., 4.6/2.3) 

c. Dual Frequency and Single voltage 

1. Use ampersand (&) between values for each frequency 

a) Hz(i.e.,60&50) 

b) Volt(i.e., 115&110) 

c) Rpm (i.e., 1725&1450) 

d) Amp (i.e., 5.0&6.0) 



This speed is the approximate rpm at rated load (see 10.32.1 and 10.32.2). 
2 This shall be permitted to be shown on a separate plate or decalcomania. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



a) 


Hz 


(i.e. 


b) 


Volt 


(i.e. 


c) 


Rpm 


(i.e. 


d) 


Amp 


(i.e. 



Section II MG 1-2009 

RATINGS— AC SMALL AND MEDIUM MOTORS Part 10, Page 11 

NOTE— If spacing in standard location on nameplate is not adequate, the values of alternative frequency and 
associated volts, rpm and amps shall be permitted to be specified at a different location on the nameplate. 

d. Dual Frequency and Dual Voltage 

1 . Use slash between voltages for one frequency and ampersand (&) between values for 
each frequency. 

, 60&50) 

. 115/230&1 10/220) 
, 1725&1450) 
, 5.0/2.5&6.0/3.0) 

NOTE — If spacing in standard location on nameplate is not adequate, the values of alternative frequency and 
associated volts, rpm, and amps shall be permitted to be specified at a different location on the nameplate. 

e. Dual Pole-Changing, Single Frequency and Single Voltage 
1. Use slash between values of hp, rpm, and amps 

a) Hp(i.e., 1/4/1/12) 

b) Rpm (i.e., 1725/1140) 

c) Amp (i.e., 4.2/2.6) 

NOTE — Horsepowers shall be permitted to be designated in decimals rather than fractions for clarity. 

f. Single-Phase-Tapped Winding 

Use marking for high speed connection only with designation for number of speeds following high 
speed rpm value and separated by a slash. 
Rpm (i.e., 1725/5SPD) 

10.40 NAMEPLATE MARKING FOR MEDIUM SINGLE-PHASE AND POLYPHASE INDUCTION 
MOTORS 

The following information shall be given on all nameplates of single-phase and polyphase induction 
motors. For motors with broad range or dual voltage, see 10.39.5. For abbreviations, see 1.79. For some 
examples of additional information that may be included on the nameplate, see 1.70.2. 

1 10.40.1 Medium Single-Phase and Polyphase Squirrel-Cage Motors 1 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating (see 10.36) 

d. Maximum ambient temperature for which motor is designed (see Note 1 of 12.43) 2 

e. Insulation system designation. (If stator or rotor use different classes of insulation systems, both 
insulation system designations shall be given on the nameplate, that for the stator being given 
first.) 2 

f. Rpm at rated load 

g. Frequency 3 
h. Number of phases 
I. Rated-load amperes 
j. Voltage 
k. Locked-rotor amperes or code letter for locked-rotor kVA per horsepower for motors 1 12 

horsepower or greater (see 10.37) 
I. Design letter for medium motors (see 1.19 and 1.20) 



1 When air flow is required over the motor from the driven equipment in order to have the motor conform to temperature rise 
standards, "air over" shall appear on the nameplate. When the heat dissipating characteristics of the driven equipment, other than 
air flow, are required in order to have the motor conform to temperature rise standards, "auxiliary cooling" shall appear on the 
nameplate. 

2 As an alternative to items d and e, the temperature rise by resistance as shown in 12.43 shall be permitted to be given. 

3 If two frequencies are stamped on the nameplate, the data covered by items b, c, d, f, i, j, and m, if different, shall be given for both 
frequencies. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 10, Page 12 RATINGS— AC SMALL AND MEDIUM MOTORS 

m. NEMA nominal efficiency when required by 12.58 

n. Service factor 

0. Service factor amperes when service factor exceeds 1.15 
p. For motors equipped with thermal protectors, the words "thermally protected" if the motor provides 

all the protection described in 12.57 (see 1.72 and 1.73) 1 
q. For motors rated above 1 horsepower equipped with over-temperature devices or systems, the 
words "OVER TEMP PROT-" followed by a type number as described in 12.57 

1 10.40.2 Polyphase Wound-Rotor Motors 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating (see 10.36) 

d. Maximum ambient temperature for which motor is designed (see Note 1 of 12.43) 2 

e. Insulation system designation. (If stator or rotor use different classes of insulation systems, both 
insulation system designations shall be given on the nameplate, that for the stator being given 
first.) 2 

f. Rpm at rated load 

g. Frequency 2 
h. Number of phases 

1. Rated-load amperes 
j. Voltage 

k. Secondary amperes at full load 

I. Secondary voltage 



This shall be permitted to be shown on a separate plate or decalcomania. 
2 If two frequencies are stamped on the nameplate, the data covered by items b, c, d, f, i, and j, if different, shall be given for both 
frequencies. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

RATINGS— DC SMALL AND MEDIUM MOTORS Part 1 0, Page 1 3 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 10 
RATINGS— DC SMALL AND MEDIUM MACHINES 

10.0 SCOPE 

The standards in this Part 10 of Section II cover direct-current motors built in frames with continuous 
dripproof ratings, or equivalent capacities, up to and including 1 .25 horsepower per rpm, open type. 

10.60 BASIS OF RATING 

10.60.1 Small Motors 

The basis of rating for a direct-current small motor shall be a rated form factor. 

If the direct-current is low ripple, the form factor is 1 .0. As the ripple increases, the form factor increases. 
A small motor is not intended to be used on a power supply that produces a form factor at the rated load 
in conjunction with the motor greater than the rated form factor of the motor. 

10.60.2 Medium Motors 

While direct-current medium motors may be used on various types of power supplies, the basis for 
demonstrating conformance of the motor with these standards shall be a test using a power supply 
described in 12.66.2. The power supply identification shall be indicated on the nameplate as an essential 
part of the motor rating in accordance with 1 0.66. 

It may not be practical to conduct tests on motors intended for use on power supplies other than those 
specified in 12.66.2. In such cases, the performance characteristics of a motor may be demonstrated by a 
test using the particular power supply or by a combination of tests on an available power supply and the 
calculation of the predicted performance of the motor from the test data. 

10.61 POWER SUPPLY IDENTIFICATION FOR DIRECT-CURRENT MEDIUM MOTORS 

10.61.1 Supplies Designated by a Single Letter 

When the test power supply used as the basis of rating for a direct-current medium motor is one of those 
described in 12.66.2, a single letter shall be used to identify the test power supply. 

1 0.61 .2 Other Supply Types 

When a direct-current medium motor is intended to be used on a power supply other than those 
described in 12.66.2, it shall be identified as follows: 

M/N F-V-H-L 

Where: 

M = a digit indicating total pulses per cycle 

N = a digit indicating controlled pulses per cycle 

F = free wheeling (this letter appears only if free wheeling is used) 

V = three digits indicating nominal line-to-line alternating-current voltage to the rectifier 

H = two digits indicating input frequency in hertz 

L = one, two, or three digits indicating the series inductance in millihenries (may be zero) to be 
added externally to the motor armature circuit 

If the input frequency is 60 hertz and no series inductance is added externally to the motor armature 
circuit, these quantities need not be indicated and shall be permitted to be omitted from the identification 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 14 



Section II 
RATINGS— DC SMALL AND MEDIUM MOTORS 



of the power supply. However, if one of these quantities is indicated, then both of them shall appear to 
avoid confusion. 

EXAMPLE: "6/3 F-380-50-12" defines a power supply having six total pulses per cycle, three controlled 
pulses per cycle, with free wheeling, with 380 volts alternating-current input at 50 hertz input, and 12 
millihenries of externally added series inductance to the motor armature circuit inductance. 

10.62 HORSEPOWER, SPEED, AND VOLTAGE RATINGS 

10.62.1 Direct-Current Small Motors 

10.62.1.1 Operational From Low Ripple (1.0 Form Factor) Power Supplies 

The horsepower and speed ratings for direct-current small constant speed motors rated 1 1 5 and 230 
volts shall be: 



Hp 




Approximate 


Full Load, Rpm 




1/20 


3450 


2500 


1725 


1140 


1/12 


3450 


2500 


1725 


1140 


1/8 


3450 


2500 


1725 


1140 


1/6 


3450 


2500 


1725 


1140 


1/4 


3450 


2500 


1725 


1140 


1/3 


3450 


2500 


1725 


1140 


1/2 


3450 


2500 


1725 


1140 


3/4 


3450 


2500 


1725 




1 


3450 


2500 







10.62.1. 2 Operation From Rectifier Power Supplies 

The horsepower, speed, voltage, and form factor ratings of direct-current small motors intended for use 
on adjustable-voltage rectifier power supplies shall be as shown in Table 10-7. 

Table 10-7 
MOTOR RATINGS FOR OPERATION FROM RECTIFIED POWER SUPPLIES 



_HfL 



Approximate Rated-Load Speed, Rpm* 



Rated Voltages, Average Direct-Current 

Values 

Armature Voltages Field Voltages Rated Form Factor 



Single-Phase Primary Power Source 



1/20 


3450 


2500 


1725 


1140 


1/15 


3450 


2500 


1725 


1140 


1/12 


3450 


2500 


1725 


1140 


1/8 


3450 


2500 


1725 


1140 


1/6 


3450 


2500 


1725 


1140 


1/4 


3450 


2500 


1725 


1140 


1/3 


3450 


2500 


1725 


1140 


1/2 


3450 


2500 


1725 


1140 



75 volts 50 or 100 volts 

90 volts 50 or 100 volts 

150 volts 100 volts 



See Notes 1 and 2 



3/4 

1 



3450 
3450 



2500 
2500 



1725 



90 volts 
180 volts 



50 or 100 volts 
100 or 200 volts 



Three-Phase Primary Power Source 



1/4 


3450 


2500 


1725 


1140 


1/3 


3450 


2500 


1725 


1140 


1/2 


3450 


2500 


1725 


1140 


3/4 


3450 


2500 


1725 




1 


3450 


2500 







240 volts 1 00, 1 50, 240 volts See Notes 1 and 2 



NOTES 

1— The rated form factor of a direct-current motor is the armature current form factor at rated load and rated speed and is an 

essential part of the motor rating. 

2— The rated form factor of a direct-current motor is determined by the motor manufacturer; see 14.60. Recommended rated form 

factors are given in Table 14-2 of 14.60. 

*Motors rated 1/20 to 1 horsepower, inclusive, are not suitable for speed control by field weakening. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

RATINGS— DC SMALL AND MEDIUM MOTORS Part 10, Page 15 



10.62.2 Industrial Direct-Current Motors 

The horsepower, voltage, and base speeds for industrial direct-current motors shall be in accordance 
with Tables 10-8, 10-9 and 10-10. The speed obtained by field control of straight shunt-wound or 
stabilized shunt-wound industrial direct-current motors shall be as shown in the tables. 

Table 10-8 

HORSEPOWER, SPEED, AND VOLTAGE RATINGS FOR INDUSTRIAL DIRECT-CURRENT MOTORS— 180 

VOLTS ARMATURE VOLTAGE RATING*, POWER SUPPLY K 

Base Speed, Rpm 



3500 2500 1750 1150 850 

"~ ~~ " Field Voltage, 

Hp Speed by Field Control, Rpm 



1/2* 








3/4* 








1* 






2050 


VA 


3850 


2750 


2050 


2 


3850 


2750 


2050 


3 


3850 


2750 


2050 


5 


3850 


2750 


2050 


TA 


3850 


2750 


2050 



940 
1380 940 
1380 94Q_ 



Volts 



50, 100, or 200 



1380 


940 




1380 


940 




1380 


940 


-► 100 or 200 


1380 


940 




1380 


940 





Tor these ratings, the armature voltage rating shall be 90 or 180 volts. 



10.63 NAMEPLATE TIME RATING 



Direct-current motors shall have a continuous rating unless otherwise specified. When a short-time rating 
is used, it shall be for 5, 15, 30, or 60 minutes. All short-time ratings are based upon a corresponding 
short-time load test which shall commence only when the windings and other parts of the machine are 
within 5°C of the ambient temperature at the time of starting the test. 

10.64 TIME RATING FOR INTERMITTENT, PERIODIC, AND VARYING DUTY 

For application on intermittent, periodic, or varying duty, the time rating shall be continuous or short- time, 
based on the thermal effects being as close as possible to those which will be encountered in actual 
service. 

10.65 NAMEPLATE MAXIMUM AMBIENT TEMPERATURE AND INSULATION SYSTEM CLASS 

Direct-current motors shall be rated on the basis of a maximum ambient temperature and the insulation 
system class. 

The rated value of the maximum ambient temperature shall be 40°C unless otherwise specified, and the 
insulation system shall be Class A, B, F, or H. All such ratings are based upon a load test with 
temperature rise values (measured by either method when two methods are listed) not exceeding those 
shown for the designated class of insulation system in the appropriate temperature rise table in 12.67. 
Ratings of direct-current motors for any other value of maximum ambient temperature shall be based on 
temperature rise values as calculated in accordance with 12.67.4. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 10, Page 16 



Section II 
RATINGS— DC SMALL AND MEDIUM MOTORS 



Table 10-9 

HORSEPOWER, SPEED, AND VOLTAGE RATINGS FOR INDUSTRIAL DIRECT-CURRENT MOTORS— 240 

VOLTS ARMATURE VOLTAGE RATING, POWER SUPPLY A, C, D, OR E 











Base Speed, Rpm 
















3500 


2500 


1750 


1150 


850 


650 


500 


400 


31 


)0 

1 




Hp 








Speed by 


Field Control 


Rpm 








= ie!d Voltage Volts 


1/2 








2000 


1700 
1700 














3/4 












1 






2300 


2000 


1700 














_► 100, 150, or 240 


1-1/2 


3850 


3000 


2300 


2000 


1700 
















2 


3850 


3000 


2300 


2000 


1700 
















3 


3850 


3000 


2300 


2000 


1700 
















5 


3850 


3000 

3000 
3000 


2300 

2300 
2300 


2000 

2000 
2000 


1700 

1700 
1700 


1600 
1600 


1500 
1500 












7-1/2 


1200 
1200 


12 
12 


00 






10 


00 






15 




3000 


2300 


2000 


1700 


1600 


1500 


1200 


1200 






20 




3000 


2300 


2000 


1700 


1600 


1500 


1200 


1200 






25 




3000 


2300 


2000 


1700 


1600 


1500 


1200 


1200 






30 




3000 


2300 


2000 


1700 


1600 


1500 


1200 


1200 






40 




3000 


2100 


2000 


1700 


1600 


1500 


1200 


1200 






50 






2100 


2000 


1700 


1600 


1500 


1200 


1200 




_► 150 or 240 


60 






2100 


2000 


1700 


1600 


1500 


1200 


1200 






75 






2100 


2000 


1700 


1600 


1500 


1200 


1200 






100 






2000 


2000 


1700 


1600 


1500 


1200 


1200 






125 






2000 


2000 


1700 


1600 


1500 


1200 


1200 






150 






2000 


2000 


1700 


1600 


1500 


1200 


1100 






200 






1900 


1800 


1700 


1600 


1500 


1200 


1100 






250 




,!..!..".... 


1900 


1700 


1600 















© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 



MG 1-2009 
Part 10, Page 17 





Table 10-10 

HORSEPOWER, SPEED, AND VOLTAGE RATINGS FOR INDUSTRIAL DIRECT-CURRENT MOTORS - 500 

OR 550* VOLTS ARMATURE VOLTAGE RATING, POWER SUPPLY A, C, OR D 










1 


3ase Speed, Rpm 












Hp 


2500 


1750 


1150 


850 


650 


500 


400 


300 










Speed by Field Control, 


Rpm 


Field Voltage Volts 






3000 


2300 


2000 


1700 












J-MZ 






10 


3000 


2300 


2000 


1700 












15 


3000 


2300 


2000 


1700 














20 


3000 


2300 


2000 


1700 














25 


3000 


2300 


2000 


1700 












30 


3000 


2300 


2000 


1700 












40 


3000 


2100 


2000 


1700 














50 






2100 


2000 


1700 


1600 


1500 


1200 


1200 






60 






2100 


2000 


1700 


1600 


1500 


1200 


1200 






75 






2100 


2000 


1700 


1600 


1500 


1200 


1200 




100 






2000 


2000 


1700 


1600 


1500 


1200 


1200 


240 or 300 


125 






2000 


2000 


1700 


1600 


1500 


1200 


1200 






150 






2000 


2000 


1700 


1600 


1500 


1200 


1100 






200 






1900 


1800 


1700 


1600 


1500 


1200 


1100 






250 






1900 


1700 


1600 


1600 


1400 


1200 


1100 




300 






1900 


1600 


1500 


1500 


1300 


1200 


1000 




400 






1900 


1500 


1500 


1400 


1300 


1200 








500 






1900 


1500 


1400 


1400 


1250 


1100 








600 








1500 


1300 


1300 


1200 










700 








1300 


1300 


1250 










800 








1250 


1250 


1200 












900 








1250 
1250 


1200 
1200 














1000 


















*550 Volts 


is a 


n alternate voltage rating 















10.66 NAMEPLATE MARKING 

The following minimum amount of information shall be given on all nameplates. For abbreviations, see 
1 .79. For some examples of additional information that may be included on the nameplate see 1 70.2. 

10.66.1 Small Motors Rated 1/20 Horsepower and Less 

a. Manufacturer's type designation 

b. Power output (millihorsepower - mhp) 

c. Full-load speed (see 10.62.1) 

d. Voltage rating 

e. The words "thermally protected" 1 for motors equipped with a thermal protector. (See 1 72 and 
173.) 

(For their own convenience, motor manufacturers shall be permitted to use letters, but not 
numbers, preceding or following the words "thermally protected" for other identification purposes.) 



1 These words shall be permitted to be shown on a separate plate or decalcomania. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 10, Page 18 RATINGS— DC SMALL AND MEDIUM MOTORS 

f. The words "impedance protected" for motors with sufficient impedance within the motors so that 
they are protected from dangerous overheating due to overload or failure to start. 1 

10.66.2 Small Motors Except Those Rated 1/20 Horsepower and Less 

a. Manufacturer's type designation 

b. Horsepower output at rated speed 

c. Time rating at rated speed 
I d. Maximum ambient temperature for which motor is designed 2 

e. Insulation system designation (if field and armature use different classes of insulation systems, 
both insulation system designations shall be given on the nameplate, that for the field being given 
first.) 

f. Speed in rpm 
I g. Rated armature voltage 3 
I h. Rated field voltage (PM for permanent magnet motors) 4, 5 

I. Armature rated-load amperes at rated speed 4 

j. Rated form factor when operated from rectifier power supply (see Table 10-7, Notes 1 and 2) 

k. The words "thermally protected" for motors equipped with a thermal protector (see 1 .72 and 1 .73) 

| 10.66.3 Medium Motors 

a. Manufacturer's type and frame designation 

b. Horsepower or kW output at base speed 

c. Time rating at rated speed 

d. Maximum safe rpm for all series-wound motors and for those compound-wound motors whose 
variation in speed from rated load to no-load exceeds 35 percent with the windings at the 
constant temperature attained when operating at its rating 

e. Maximum ambient temperature for which the motor is designed 2 

f. Insulation system designation (If field and armature use different classes of insulation systems, 
both insulation systems shall be given, that for the field being given first.) 2 

g. Base speed at rated load 
h. Rated armature voltage 3 



^ These words shall be permitted to be shown in a separate plate or decalcornania. 

2 As an alternative, these items shall be permitted to be replaced by a single item reading "Rated temperature rise " 

These are average direct-current quantities. 
4 As an alternative, this item shall be permitted to be replaced by the following: 

a. Field resistance in ohms at 25°C 

b. Rated field current in amperes 

For separately excited, series-parallel, dual voltage windings, the two values of rated voltage shall both be shown. If a single value 
of current and resistance is shown, the data applies to the high voltage connection. If values of current and resistance for each 
voltage is shown, the voltage connection for which this data applies shall be indicated as well. A slash is permitted to indicate dual 
voltage and currents and they may be respectively high volt/low volt, high current/low current. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

RATINGS— DC SMALL AND MEDIUM MOTORS Part 1 0, Page 1 9 

i. Rated field voltage (not applicable for permanent magnet motors 1, 2 ' 3 

j. Armature rated-load current in amperes at base speed 1 

k. Power supply identification in accordance with 10.61 

I. Winding - straight shunt, stabilized shunt, compound, series, or permanent magnet 

m. Direct-current or dc 

n. (Optional) Enclosure or IP code (see Part 5) 

o. (Optional) Manufacturer's name, mark, or logo 

p. (Optional) Manufacturer's plant location 

q. (Optional) Serial number or date of manufacture 

r. (Optional) Model number or catalog number 



These are average direct-current quantities 

2 As an alternative, this item shall be permitted to be replaced by the following: 

a. Field resistance in ohms at 25°C 

b. Rated field current in amperes. A single value of field current corresponds to the base speed. Two values correspond to the 
base speed and the highest speed obtained by field control. 

3 For separately excited, series-parallel, dual voltage windings, the two values of rated voltage shall both be shown. If a single value 
of current and resistance is shown, the data applies to the high voltage connection. If values of current and resistance for each 
voltage is shown, the voltage connection for which this data applies shall be indicated as well. A slash is permitted to indicate dual 
voltage and currents and they may be respectively high volt/low volt, high current/low current. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 10, Page 20 RATINGS— DC SMALL AND MEDIUM MOTORS 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12 



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Section II MG 1-2009 

TESTS AND PERFORMANCE— AC AND DC MOTORS Part 12, Page 1 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 12 
TESTS AND PERFORMANCE— AC AND DC MOTORS 

12.0 SCOPE 

The standards in this Part 12 of Section II cover the following machines: 

a. Alternating-Current Motors: Alternating-current motors up to and including the ratings built in frames 
corresponding to the continuous open-type ratings given in the table below. 





Motors 
Squirrel- 
Cage and 

Wound 
Rotor, Hp 


Motors, 


Synchronous, Hp 




Power Factor 


Synchronous 
Speed 


Unity 




0.8 


3600 


500 


500 




400 


1800 


500 


500 




400 


1200 


350 


350 




300 


900 


250 


250 




200 


720 


200 


200 




150 


600 


150 


150 




125 


514 


125 


125 




100 



b. Direct-Current Motors: Direct-current motors built in frames with continuous dripproof ratings, or 
equivalent capacities, up to and including 1.25 horsepower per rpm, open type. 

1 2.2 HIGH-POTENTIAL TEST— SAFETY PRECAUTIONS AND TEST PROCEDURE 

See 3.1. 

12.3 HIGH-POTENTIAL TEST VOLTAGES FOR UNIVERSAL, INDUCTION, AND DIRECT- 
CURRENT MOTORS 

The high-potential test voltage specified in the following table shall be applied to the windings of each 
new machine in accordance with the test procedures specified in 3.1. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 2 TESTS AND PERFORMANCE— AC AND DC MOTORS 



Category Effective Test Voltage 

a. Universal Motors (rated for operation on circuits not 
exceeding 250 volts) 

1 . Motors rated greater than 1/2 horsepower and all motors for 

portable tools 1000 v0 | ts + 2 tjmes the rated v0 | tage of the motor but jn no 

case less than 1 500 volts 

2. All other motors* 1500 volts 

b. Induction and Nonexcited Synchronous Motors 

1. Motors rated greater than 1/2 horsepower 

a) Stator windings 1000 volts + 2 times the rated voltage of the motor, but in no 

case less than 1 500 volts 

b) For secondary windings of wound rotors of induction 

motors 1000 volts + 2 times the maximum voltage induced between 

collector rings on open circuit at standstill (or running if under 
this condition the voltage is greater) with rated primary voltage 
applied to the stator terminals, but in no case less than 1 500 
volts 
c. For secondary windings of wound rotors of reversing 

motors 1000 volts + 4 times the maximum voltage induced between 

collector rings on open circuit at standstill with rated primary 
voltage applied to the stator terminals, but in no case less than 
1500 volts 

2. Motors rated 1/2 horsepower and less 

a. Rated 250 volts or less 1500 volts 

b. Rated above 250 volts 1000 volts + 2 times the rated voltage of the motor, but in no 

case less than 1 500 volts 

c. Direct-Current Motors 

1. Motors rated greater than 1/2 horsepower 

a) Armature or field windings for use on adjustable-voltage 

electronic power supply 1000 vo|ts + 2 tjmes the gc | ine „ t0 „| jne v0 , tage of the power 

supply selected for the basis of rating, but in no case less than 
1500 volts 

b) All other armature or field windings 1000 volts + 2 times the rated voltage** of the motor, but in no 

case less than 1 500 volts 

2. Motors rated 1/2 horsepower and less 

a) 240 volts or less 1500 volts 

b) Rated above 240 volts See C.1.a and C.1 .b above (Direct-Current Motors) 



*Complete motors 1/2 horsepower and less shall be in the "all other" category unless marked to indicate that they are motors for 
portable tools. 

**Where the voltage rating of a separately excited field of a direct-current motor or generator is not stated, it shall be assumed to be 

1 .5 times the field resistance in ohms at 25°C times the rated field current. 

NOTES— 

1 —Certain applications may require a high-potential test voltage higher than those specified. 

2— The normal production high-potential test voltage may be 1 2 times the specified 1 -minute high-potential test-voltage, applied for 
1 second. (See 3.1.6.) 

3— To avoid excessive stressing of the insulation, repeated application of the high-potential test-voltage is not recommended. 
Immediately after manufacture, when equipment is installed or assembled with other apparatus and a high-potential test of the entire 
assembly is required, it is recommended that the test voltage not exceed 80 percent of the original test voltage or, when in an 
assembled group, not exceed 80 percent of the lowest test voltage of that group. (See 3. 1 . 1 1 .) 

12.4 PRODUCTION HIGH-POTENTIAL TESTING OF SMALL MOTORS 

Dielectric failure in high-potential production testing of small motors shall be indicated by a measurement 
of insulation resistance less than 1 megohm when tested in accordance with 12.2 and 12.3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG i_2009 

TESTS AND PERFORMANCE— AC AND DC MOTORS Part 12, Page 3 



12.4.1 Dielectric Test Equipment 

The dielectric test equipment should indicate a failure by visual or audible means, or both. The test 
equipment should preferably be designed to limit the level of applied current to a nondestructive value at 
the high-potential voltage. 

12.4.2 Evaluation of Insulation Systems by a Dielectric Test 

The definition of dielectric failure per ASTM D 149 is based upon observation of actual rupture of 
insulation as positive evidence of voltage breakdown. In small motors, a suitable evaluation of insulation 
quality in production testing may be made without complete rupture of the insulation to ground. As a 
quality control procedure during manufacture, measurement of the insulation resistance may be taken as 
a true evaluation of the effectiveness of the insulation system. 

12.5 REPETITIVE SURGE TEST FOR SMALL AND MEDIUM MOTORS 

Many manufacturers use a repetitive test as a quality control test for the components of motors; for 
example, stators and rotors. When a large number of motors of a single design are to be tested, a 
repetitive surge test is a quick and economical test to make to detect the following faults: 

a. Grounded windings 

b. Short circuits between turns 

c. Short circuits between windings 

d. Incorrect connections 

e. Incorrect number of turns 

f. Misplaced conductors or insulation 

The repetitive surge test compares an unknown winding with a known winding or a winding assumed to 
be satisfactory. This is accomplished by superimposing on an oscilloscope the traces of the surge voltage 
at the terminals of the windings. Major faults are easily detected but a skilled operator is required to 
distinguish between minor faults; for example, a slipped slot cell and the harmless deviations in the traces 
which occur when windings are produced by two or more operators who place the coils or form the end 
turns in slightly different ways. 

Unfortunately, the repetitive surge test has disadvantages which limit its general usage, such as the 
necessity for elaborate preliminary tests before a surge test can be made on production units. For 
example, voltage distribution through the winding should be investigated because resonant conditions 
may exist which would cause abnormally high or low stresses at some point in the insulation system of 
the motor component. Elaborate preliminary tests can seldom be justified when a small number of 
components is involved because comparatively small changes in design may require additional 
preliminary tests. When a repetitive surge test is made, the surge voltage level and other test conditions 
should be based upon data obtained from laboratory tests made on the particular design (or designs) of 
the motors involved. 

When a rotor or stator has two or more identical windings, for example, a polyphase stator, each winding 
may be tested against the other because it is unlikely that any two of the windings will have identical 
faults. To make it practicable to surge test rotors or stators of similar motor designs one at a time, it is 
essential that sufficient data be accumulated by the preliminary tests on several individual designs. When 
a rotor or stator does not have two identical windings, for example, single-phase stators and direct- 
current armatures, a minimum of two of the same component is required for the repetitive surge test. In 
the event that a fault is disclosed by the test, a minimum of three units is required to determine which one 
had the fault. 

It should be noted that, except by undertaking extensive comparative breakdown tests, there is at present 
no satisfactory way of determining the surge test voltage equivalent to a 60-hertz high-potential test. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 4 TESTS AND PERFORMANCE— AC AND DC MOTORS 



12.6 MECHANICAL VIBRATION 

See Part 7. 

1 2.7 BEARING LOSSES— VERTICAL PUMP MOTORS 

The added losses in horsepower in angular contact bearings used on vertical pump motors, due to added 
load over that incurred by the motor rotor, should be calculated by the following formula: 

Added losses in horsepower = 2.4 x 10" 8 x added load in lbs. x revolutions per minute x pitch 
diameter in inches of the balls in the ball bearing. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 5 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

PART 12 
TESTS AND PERFORMANCE— AC MOTORS 



12.0 SCOPE 

The standards in this Part 12 of Section II cover alternating-current motors up to and including the ratings 
built in frames corresponding to the continuous open-type ratings given in the table below. 





Motors 
Squirrel- 
Cage and 

Wound 
Rotor, Hp 


Motors, 


Synchronous, Hp 






Power 


Factor 




Synchronous 
Speed 


Unity 




0.8 


Generators, 
Synchronous 

Revolving 
Field Type, 

kW at 0.8 
Power Factor 


3600 


500 


500 




400 


400 


1800 


500 


500 




400 


400 


1200 


350 


350 




300 


300 


900 


250 


250 




200 


200 


720 


200 


200 




150 


150 


600 


150 


150 




125 


125 


514 


120 


125 




100 


100 


TEST METHODS 













12.30 

Tests to determine performance characteristics shaii be made in accordance with the following: 

a. For single-phase motors-IEEE Std 114 

b. For polyphase induction motors - IEEE Std 112 

1 2.31 PERFORMANCE CHARACTERISTICS 

When performance characteristics are provided, they should be expressed as follows: 

a. Current in amperes or percent of rated current 

b. Torque in pound-feet, pound-inches, ounce-feet, ounce-inches, or percent of full-load torque 

d. Output in horsepower or percent of synchronous speed 

e. Efficiency in percent 

f. Power factor in percent 

g. Voltage in volts or percent of rated voltage 
h. Input power in watts or kilowatts 

NOTE— If SI units are used, they should be in accordance with ISO Publication No. R-1000. 

12.32 TORQUE CHARACTERISTICS OF SINGLE-PHASE GENERAL-PURPOSE INDUCTION 
MOTORS 

12.32.1 Breakdown Torque 

The breakdown torque of single-phase general-purpose small and medium induction motors shall be 
within the torque range as given in Table 10-5, subject to tolerances in manufacturing and ail other 
conditions given in 10.34. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 6 



TESTS AND PERFORMANCE- 



Section II 
-AC MOTORS 



1 2.32.2 Locked-Rotor Torque of Small Motors 

The locked-rotor torque of single-phase general-purpose small motors, with rated voltage and frequency 
applied, shall be not less than the following: 







Minimum 


Locked-Rotor Torque, 


ounce-feet* 






60-Hertz 


Synchronous Speed, Rpm 


50- Hertz 


Synchronous 


Speed, Rpm 


HP 


3600 


1800 


1200 


3000 


1500 


1000 


1/8 




24 


32 




29 


39 


1/6 


15 


33 


43 


18 


39 


51 


1/4 


21 


46 


59 


25 


55 


70 


1/3 


26 


57 


73 


31 


69 


88 


1/2 


37 


85 


100 


44 


102 


120 


3/4 


50 


119 




60 


143 




1 


61 






73 







*On the high voltage connection of dual voltage motors, minimum locked-rotor torques up to 
10% less than these values may be expected. 

1 2.32.3 Locked-Rotor Torque of Medium Motors 

The locked-rotor torque of single-phase general-purpose medium motors, with rated voltage and 
frequency applied, shall be not less than the following: 





Minimum Locked-Rotor Torque, po 


jnd-feet 






Synchi 


onous Speed, 


Rpm 




HP 


3600 




1800 




1200 


3/4 










8.0 


1 






9.0 




9.5 


VA 


4.5 




12.5 




13.0 


2 


5.5 




16.0 




16.0 


3 


7.5 




22.0 




23.0 


5 


11.0 




33.0 






VA 


16.0 




45.0 






10 


21.0 




52.0 







12.32.4 Pull-Up Torque of Medium Motors 

The pull-up torque of single-phase general-purpose alternating-current medium motors, with rated 
voltage and frequency applied, shall be not less than the rated load torque. 

12.33 LOCKED-ROTOR CURRENT OF SINGLE-PHASE SMALL MOTORS 
12.33.1 Design O and Design N Motors 

The locked-rotor current of 60-hertz, single-phase motors shall not exceed the values given in the 
following table: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 7 



2-, 4- 


6-, and 8-Pole, 


60-Hertz Motors 


Single Phase 






Locked-Rotor C 


urrent, Amperes 




115 Volts 


230 Volts 


Hp 


Design 


Design N 


Design O 


Design N 


1/6 and smaller 


50 


20 




25 


12 


1/4 




50 


26 




25 


15 


1/3 




50 


31 




25 


18 


1/2 




50 


45 




25 


25 


3/4 






61 






35 


1 






80 






45 



12.33.2 General-Purpose Motors 

The locked-rotor currents of single-phase general-purpose motors shall not exceed the values for Design 
N motors. 

12.34 LOCKED-ROTOR CURRENT OF SINGLE-PHASE MEDIUM MOTORS, DESIGNS L AND M 

The locked-rotor current of single-phase, 60-hertz, Design L and M motors of att types, when measured 
with rated voltage and frequency impressed and with the rotor locked, shall not exceed the following 
values: 





Locked-Roto 


r Current 


Amperes 


Design L 
Motors 


Design 

M 
Motors 


HP 


115 
Volts 


230 
Volts 


230 
Volts 


1/2 


45 


25 




3/4 


61 


35 




1 


80 


45 




1 1 / 2 




50 


40 


2 




65 


50 


3 




90 


70 


5 




135 


100 


TA 




200 


150 


10 




260 


200 



12.35 LOCKED-ROTOR CURRENT OF 3-PHASE SMALL AND MEDIUM SQUIRREL-CAGE 
INDUCTION MOTORS 

12.35.1 60-Hertz Design B, C, and D Motors at 230 Volts 

The locked-rotor current of single-speed, 3-phase, constant-speed induction motors rated at 230 volts, 
when measured with rated voltage and frequency impressed and with rotor locked, shall not exceed the 
values listed on the next page. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 8 TESTS AND PERFORMANCE— AC MOTORS 

MAXIMUM LOCKED-ROTOR CURRENT FOR 60-Hz 
DESIGN B, C, AND D MOTORS AT 230 VOLTS 

Locked-Rotor 
Hj> Current, Amperes* Design Letters 



1/2 20 B, D 

3/4 25 B, D 

1 30 B, C, D 
1-1/2 40 B, C, D 

2 50 B, C, D 

3 64 B, C, D 
5 92 B, C, D 

7-1/2 127 B, C, D 

10 162 B, C, D 

15 232 B, CD 

20 290 B, C, D 

25 365 B, C, D 

30 435 B, C, D 

40 580 B, C, D 

50 725 B, C, D 

60 870 B, C, D 

75 1085 B,C, D 

100 1450 B,C, D 

125 1815 B, C, D 

150 2170 B, C, D 

200 2900 B, C 

250 3650 B 

300 4400 B 

350 5100 B 

400 5800 B 

450 6500 B 

500 7250 B 



*The locked-rotor current of motors designed for voltages other than 230 
volts shall be inversely proportional to the voltages. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section tl 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 9 



12.35.2 50-Hertz Design B, C, and D Motors at 380 Volts 

The locked-rotor current of single-speed, 3-phase, constant-speed induction motors rated at 380 volts, 
when measured with rated voltage and frequency impressed and with rotor locked, shall not exceed the 
values shown in Table 12-1. 

Table 12-1 

MAXIMUM LOCKED-ROTOR CURRENT FOR 50-Hz 

DESIGN B, C, AND D MOTORS AT 380 VOLTS 





Locked-Rotor 






Current, 




Hp 


Amperes* 


Design Letters 


3/4 or less 


20 


B, D 


1 


20 


B, C, D 


1-1/2 


27 


B, C, D 


2 


34 


B.C, D 


3 


43 


B, C, D 


5 


61 


B, C, D 


7-1/2 


84 


B, C, D 


10 


107 


B, C, D 


15 


154 


B, C, D 


20 


194 


B, C, D 


25 


243 


B, C, D 


30 


289 


B, C, D 


40 


387 


B, C,D 


50 


482 


B, CD 


60 


578 


B, C, D 


75 


722 


B, C, D 


100 


965 


B, CD 


125 


1207 


B, C,D 


150 


1441 


B, CD 


200 


1927 


B, C 


250 


2534 


B 


300 


3026 


B 


350 


3542 


B 


400 


4046 


B 


450 


4539 


B 


500 


5069 


B 



*The locked-rotor current of motors designed for voltages other 
than 380 volts shall be inversely proportional to the voltages. 

12.36 INSTANTANEOUS PEAK VALUE OF INRUSH CURRENT 

The values in the previous tables are rms symmetrical values, i.e. average of the three phases. There will 
be a one-half cycle instantaneous peak value which may range from 1 .8 to 2.8 times the above values as 
a function of the motor design and switching angle. This is based upon an ambient temperature of 25°C. 

12.37 TORQUE CHARACTERISTICS OF POLYPHASE SMALL MOTORS 

The breakdown torque of a general-purpose polyphase squirrel-cage small motor, with rated voltage and 
frequency applied, shail be not less than 140 percent of the breakdown torque of a single-phase general- 
purpose small motor of the same horsepower and speed rating given in 12.32. 

NOTE — The speed at breakdown torque is ordinarily much lower in small polyphase motors than in small single-phase 
motors. Higher breakdown torques are required for polyphase motors so that polyphase and single-phase motors will 
have interchangeable running characteristics, rating for rating, when applied to normal single-phase motor loads. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 10 



Section II 
TESTS AND PERFORMANCE— AC MOTORS 



12.38 LOCKED-ROTOR TORQUE OF SINGLE-SPEED POLYPHASE SQUIRREL-CAGE MEDIUM 
MOTORS WITH CONTINUOUS RATINGS 

12.38.1 Design A and B Motors 

The locked-rotor torque of Design A and B, 60- and 50-hertz, single-speed polyphase squirrel-cage 
medium motors, with rated voltage and frequency applied, shall be not less than the values shown in 
Table 12-2 which are expressed in percent of full-load torque. For applications involving higher torque 
requirements, see 12.38.2 and 12.38.3 for locked-rotor torque values for Design C and D motors. 



Table 12-2 
LOCKED-ROTOR TORQUE OF DESIGN A AND B, 60- AND 50-HERTZ SINGLE-SPEED 

POLYPHASE SQUIRREL-CAGE MEDIUM MOTORS 

Synchronous Speed, Rpm 



60 Hertz 3600 


1800 


1200 


900 


Hp 50 Hertz 3000 


1500 


1000 


750 


1/2 








140 


3/4 






175 


135 


1 




275 


170 


135 


1-1/2 


175 


250 


165 


130 


2 


170 


235 


160 


130 


3 


160 


215 


155 


130 


5 


150 


185 


150 


130 


7-1/2 


140 


175 


150 


125 


10 


135 


165 


150 


125 


15 


130 


160 


140 


125 


20 


130 


150 


135 


125 


25 


130 


150 


135 


125 


30 


130 


150 


135 


125 


40 


125 


140 


135 


125 


50 


120 


140 


135 


125 


60 


120 


140 


135 


125 


75 


105 


140 


135 


125 


100 


105 


125 


125 


125 


125 


100 


110 


125 


120 


150 


100 


110 


120 


120 


200 


100 


100 


120 


120 


250 


70 


80 


100 


100 


300 


70 


80 


100 




350 


70 


80 


100 




400 


70 


80 






450 


70 


80 






500 


70 


80 







720 



600 



514 



140 
135 
135 
130 
125 

125 

125 
120 
120 
120 

120 
120 
120 
120 
120 

120 
120 
120 
115 
115 

115 



115 
115 
115 

115 
115 

115 
115 
115 
115 
115 

115 
115 
115 
115 
115 

115 
115 
115 
115 
115 



110 

110 
110 
110 
110 

110 

110 
110 
110 
110 

110 
110 
110 
110 
110 

110 
110 
110 
110 



12.38.2 Design C Motors 

The locked-rotor torque of Design C, 60- and 50-hertz, single-speed polyphase squirrel-cage medium 
motors, with rated voltage and frequency applied, shall be not less than the values shown in Table 12-3 
which are expressed in percent of full-load torque. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 1 1 



Table 12-3 
LOCKED-ROTOR TORQUE OF DESIGN C MOTORS 



Synchronous Speed, Rpm 



60 Hz 1800 1200 900 

Hp 50 Hz 1500 1000 750 

1 285 255 225 
1.5 285 250 225 

2 285 250 225 

3 270 250 225 
5 255 250 225 

7.5 250 225 200 

10 250 225 200 

15 225 210 200 

20-200 Inclusive 200 200 200 



12.38.3 Design D Motors 

The locked-rotor torque of Design D, 60- and 50-hertz, 4-, 6-, and 8-pole, single-speed polyphase 
squirrel-cage medium motors rated 150 horsepower and smaller, with rated voltage and frequency 
applied, shall be not less than 275 percent, expressed in percent of full-load torque. 

12.39 BREAKDOWN TORQUE OF SINGLE-SPEED POLYPHASE SQUIRREL-CAGE MEDIUM 
MOTORS WITH CONTINUOUS RATINGS 

12.39.1 Design A and B Motors 

The breakdown torque of Design A and B, 60- and 50-hertz, single-speed polyphase squirrel-cage 
medium motors, with rated voltage and frequency applied, shall be not less than the following values 
which are expressed in percent of full-load torque: 









Synchronous 


Speed, Rpm 








60 Hertz 


3600 


1800 


1200 


900 


720 


600 


514 


Hp 50 Hertz 


3000 


1500 


1000 


750 








1/2 








225 


200 


200 


200 


3/4 






275 


220 


200 


200 


200 


1 




300 


265 


215 


200 


200 


200 


1-1/2 


250 


280 


250 


210 


200 


200 


200 


2 


240 


270 


240 


210 


200 


200 


200 


3 


230 


250 


230 


205 


200 


200 


200 


5 


215 


225 


215 


205 


200 


200 


200 


7-1/2 


200 


215 


205 


200 


200 


200 


200 


10-125, inclusive 


200 


200 


200 


200 


200 


200 


200 


150 


200 


200 


200 


200 


200 


200 




200 


200 


200 


200 


200 


200 






250 


175 


175 


175 


175 








300-350 


175 


175 


175 










400-500, inclusive 


175 


175 













12.39.2 Design C Motors 

The breakdown torque of Design C, 60- and 50-hertz, single-speed polyphase squirrel-cage medium 
motors, with rated voltage and frequency applied, shall be not less than the following values which are 
expressed in percent of full-load torque: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 12 



Section II 
TESTS AND PERFORMANCE— AC MOTORS 



Hp 



60 Hz 
50 Hz 



Synchronous Speed, Rpm 



1800 
1500 



1200 
1000 



900 
750 



1 

1-1/2 

2 

3 

5 

7-1/2-20 

25-200 Inclusive 



200 
200 
200 
200 
200 
200 
190 



225 
225 
225 
225 
200 
190 
190 



200 
200 
200 
200 
200 
190 
190 



12.40 



PULL-UP TORQUE OF SINGLE-SPEED POLYPHASE SQUIRREL-CAGE MEDIUM MOTORS 
WITH CONTINUOUS RATINGS 



12.40.1 Design A and B Motors 

The pull-up torque of Design A and B, 60- and 50-hertz single-speed, polyphase squirrel-cage medium 
motors, with rated voltage and frequency applied, shall be not less than the following values which are 
expressed in percent of full-load torque: 











Synchronous 


Speed, Rpm 








60 Hertz 


3600 


1800 


1200 


900 


720 


600 


514 


Hp 


50 Hertz 


3000 


1500 


1000 


750 








1/2 










100 


100 


100 


100 


3/4 








120 


100 


100 


100 


100 


1 






190 


120 


100 


100 


100 


100 


1-1/2 




120 


175 


115 


100 


100 


100 


100 


2 




120 


165 


110 


100 


100 


100 


100 


3 




110 


150 


110 


100 


100 


100 


100 


5 




105 


130 


105 


100 


100 


100 


100 


7-1/2 




100 


120 


105 


100 


100 


100 


100 


10 




100 


115 


105 


100 


100 


100 


100 


15 




100 


110 


100 


100 


100 


100 


100 


20 




100 


105 


100 


100 


100 


100 


100 


25 




100 


105 


100 


100 


100 


100 


100 


30 




100 


105 


100 


100 


100 


100 


100 


40 




100 


100 


100 


100 


100 


100 


100 


50 




100 


100 


100 


100 


100 


100 


100 


60 




100 


100 


100 


100 


100 


100 


100 


75 




95 


100 


100 


100 


100 


100 


100 


100 




95 


100 


100 


100 


100 


100 


100 


125 




90 


100 


100 


100 


100 


100 


100 


150 




90 


100 


100 


100 


100 


100 




200 




90 


90 


100 


100 


100 






250 




65 


75 


90 


90 








300 




65 


75 


90 










350 




65 


75 


90 










400 




65 


75 












450 




65 


75 












500 




65 


75 













© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 13 



12.40.2 Design C Motors 

The pull-up torque of Design C 60- and 50-hertz, single speed, polyphase squirrel-cage medium motors, 
with rated voltage and frequency applied, shall be not less than the following values which are expressed 
in percent of full-load torque: 





Synchronous Speed, 


Rpm 




60 Hz 1800 


1200 


900 


Hp 


50 Hz 1500 


1000 


750 


1 


195 


180 


165 


1-1/2 


195 


175 


160 


2 


195 


175 


160 


3 


180 


175 


160 


5 


180 


175 


160 


7-1/2 


175 


165 


150 


10 


175 


165 


150 


15 


165 


150 


140 


20 


165 


150 


140 


25 


150 


150 


140 


30 


150 


150 


140 


40 


150 


150 


140 


50 


150 


150 


140 


60 


140 


140 


140 


75 


140 


140 


140 


100 


140 


140 


140 


125 


140 


140 


140 


150 


140 


140 


140 


200 


140 


140 


140 



12.41 BREAKDOWN TORQUE OF POLYPHASE WOUND-ROTOR MEDIUM MOTORS WITH 
CONTINUOUS RATINGS 

The breakdown torques of 60- and 50-hertz, polyphase wound-rotor medium motors, with rated voltage 
and frequency applied, shall be not less than the following values which are expressed in percent of full- 
load torque: 







Breakdown 


Torque, Percent of Full- 
Load Torque 






Synchronous Speed, 


Rpm 


l H. 


60 Hz 
50 Hz 


1800 
1500 


1200 
1000 


900 
750 


1 








250 


1-1/2 








250 


2 




275 


275 


250 


3 




275 


275 


250 


5 




275 


275 


250 


7-1/2 




275 


275 


225 


10 




275 


250 


225 


15 




250 


225 


225 


20-200 Inclusive 




225 


225 


225 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 14 TESTS AND PERFORMANCE— AC MOTORS 

12.42 TEMPERATURE RISE FOR SMALL AND UNIVERSAL MOTORS 

Temperatures for 12.42.1 and 12.42.2 shall be determined in accordance with the following: 

a. For single-phase motors - IEEE Std 114 

b. For polyphase induction motors - IEEE Std 112 

12.42.1 Alternating-Current Small Motors — Motor Nameplates Marked with Insulation System 
Designation and Ambient Temperature 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of the 
motor shall not exceed the values given in the following table when tested in accordance with the rating, 
except that for motors having a service factor greater than 1 .0, the temperature rise shall not exceed the 
values given in the following table when tested at the service factor load: 



Class of Insulation System (see 1.65) A B F* H* 

Time Rating (see 10.36) 

Temperature Rise (based on a maximum ambient temperature of 40°C), Degrees C 
a. Windings 

1. Open motors other than those given in items a. 2 and a.5-resistance or 

thermocouple 60 80 105 125 

2. Open motors with 1 . 1 5 or higher service factor - resistance or 

thermocouple 70 90 115 

3. Totally enclosed nonventilated motors, including variations thereof - 

resistance or thermocouple 55 85 110 130 

4. Totally enclosed fan-cooled motors, including variations thereof - 

resistance or thermocouple 65 85 110 135 

5. Any motor in a frame smaller than the 42 frame - resistance or 

thermocouple 65 85 110 135 

*Where a Class F or H insulation system is used, special consideration should be given to bearing temperatures, lubrication, etc. 

NOTES 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular 

operation. See 12.42.3. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. 
For temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 15 

12.42.2 Universal Motors 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of the 
motor, when tested in accordance with the rating, shall not exceed the values given in the following table: 



Class of Insulation System (see 165) A B F* H* 

Time Rating (see 10.36) 

Temperature Rise (based on a maximum ambient temperature of 40°C) Degrees C 
a. Windings 

1. Open motors - thermocouple or resistance 60 80 105 125 

2. Totally enclosed nonventilated motors, including variations thereof - 

thermocouple or resistance 65 85 110 130 

3. Totally enclosed fan-cooled motors, including variations thereof - 

resistance or thermocouple 65 85 11Q 135 

*Where a Class F or H insulation system is used, special consideration should be given to bearing temperatures, lubrication, etc. 

NOTES— 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular 
operation. See 12.42.3. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. 
For temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 

12.42.3 Temperature Rise for Ambients Higher than 40°C 

The temperature rises given in 12.42.1 and 12.42.2 are based upon a reference ambient temperature of 
40°C. However, it is recognized that induction machines may be required to operate in an ambient 
temperature higher than 40°C. For successful operation of induction machines in ambient temperatures 
higher than 40°C, the temperature rises of the machines given in 12.42.1 and 12.42.2 shall be reduced by 
the number of degrees that the ambient temperature exceeds 40°C. When a higher ambient temperature 
than 40°C is required, preferred values of ambient temperatures are 50°C, 65°C, 90°C, and 1 1 5°C. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 16 TESTS AND PERFORMANCE—AC MOTORS 

12.42.4 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0°C* 

The temperature rises given in 12.42.1 and 12.42.2 are based upon a reference ambient temperature of 
40°C to cover most general environments. However, it is recognized that air-cooled induction machines 
may be operated in environments where the ambient temperature of the cooling air will always be less 
than 40°C. When an air-cooled induction machine is marked with a maximum ambient less than 40°C 
then the allowable temperature rises in 12.42,1 and 12.42.2 shall be increased according to the following: 

a) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.42.1 and 12.42.2 is less than or equal to 5°C then the 
temperature rises given in 12.42.1 and 12.42.2 shall be increased by the amount of the difference 
between 40°C and the lower marked ambient temperature. 

b) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.42.1 and 12.42.2 is greater than 5°C then the temperature rises 
given in 12.42.1 and 12.42.2 shall be increased by the amount calculated from the following expression: 

Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 

Where: 



Class of Insulation System 




A B F 


H 


Reference Temperature for SF less than 
1.15, Degrees C 

Reference Temperature for 1.15 SF or 
higher, Degrees C 


105 130 155 
115 140 165 


180 
190 



*Note — This requirement does not include water-cooled machines. 

Temperature Rise Limit = maximum allowable temperature rise according to 12.42.1 and 12.42.2 

For example: A 1 .0 service factor rated open motor with a Class F insulation system is marked for 
use in an ambient with a maximum temperature of 25°C. From the Table above the Reference 
Temperature is 155°C and from 12.42.1 the Temperature Rise Limit is 105°C. The allowable 
Increase in Rise to be added to the Temperature Rise Limit is then: 

i • d- Lnor ^riit 155°C~(40 Q C + 105 Q c) ] 0r 
Increase in Rise = 140 C-25 C^l * — - }~*3 C 

l[ 80°C Ij 

The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then 
equal to the sum of the Temperature Rise Limit from 12.42.1 and the calculated Increase in Rise. 
For this example that total is 105°C + 13°C = 118°C. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 17 

12.43 TEMPERATURE RISE FOR MEDIUM SINGLE-PHASE AND POLYPHASE INDUCTION 
MOTORS 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of the 
motor shall not exceed the values given in the following table when tested in accordance with the rating, 
except that for motors having a service factor 1.15 or higher, the temperature rise shall not exceed the 
values given in the following table when tested at the service factor load. Temperatures shall be 
determined in accordance with the following: 

a. For single-phase motors - IEEE Std 1 14 

b. For polyphase induction motors - IEEE Std 112 



Class of Insulation System (see 1.65) A B F* H*t 

Time Rating (shall be continuous or any short-time rating given in 10.36) 
Temperature Rise (based on a maximum ambient temperature of 40°C), Degrees C 

a. Windings, by resistance method 

1 . Motors with 1 .0 service factor other than those given in items 

a.3and a.4 60 80 105 125 

2. All motors with 1.15 or higher service factor 70 90 115 

3. Totally-enclosed nonventilated motors with 1.0 service factor 65 85 110 130 

4. Motors with encapsulated windings and with 1.0 service factor, all 

enclosures 65 85 110 

b. The temperatures attained by cores, squirrel-cage windings, and miscellaneous 

parts (such as brushholders, brushes, pole tips , etc.) shall not injure the insulation 

or the machine in any respect r ^__ = ___ = ^__ === ^^ 

*Where a Class F or H insulation system is used, special consideration should be given to bearing temperatures, lubrication, etc. 

fThis column applies to polyphase motors only. 

NOTES 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular 

operation. See 12.43.1. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. 

For temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 

12.43.1 Temperature Rise for Ambients Higher than 40°C 

The temperature rises given in 12.43 are based upon a reference ambient temperature of 40°C. 
However, it is recognized that induction machines may be required to operate in an ambient temperature 
higher than 40°C. For successful operation of induction machines in ambient temperatures higher than 
40°C, the temperature rises of the machines given in 12.43 shall be reduced by the number of degrees 
that the ambient temperature exceeds 40°C. When a higher ambient temperature than 40°C is required, 
preferred values of ambient temperatures are 50°C, 65°C, 90°C, and 1 1 5°C. 



» Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 18 TESTS AND PERFORMANCE— AC MOTORS 

12.43.2 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0°C* 

The temperature rises given in 12.43 are based upon a reference ambient temperature of 40°C to cover 
most general environments. However, it is recognized that air-cooled induction machines may be 
operated in environments where the ambient temperature of the cooling air will always be less than 40°C. 
When an air-cooled induction machine is marked with a maximum ambient less than 40°C then the 
allowable temperature rises in 12.43 shall be increased according to the following: 

a) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.43 is less than or equal to 5°C then the temperature rises given in 
12.43 shall be increased by the amount of the difference between 40°C and the lower marked ambient 
temperature. 

b) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.43 is greater than 5°C then the temperature rises given in 12.43 
shall be increased by the amount calculated from the following expression: 

Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 

Where: 



Class of Insulation System 



B F H 



Reference Temperature for SF less than 


105 


130 


155 


180 


1.15, Degrees C 










Reference Temperature for 1 . 1 5 SF or 


115 


140 


165 


190 


higher, Degrees C 











*NOTE-— This requirement does not include water-cooled machines. 

Temperature Rise Limit = maximum allowable temperature rise according to 12.43 

For example: A 1 .0 service factor rated open motor with a Class F insulation system is marked for 
use in an ambient with a maximum temperature of 25°C. From the Table above the Reference 
Temperature is 155°C and from 12.43 the Temperature Rise Limit is 105°C. The allowable Increase 
in Rise to be added to the Temperature Rise Limit is then: 



Increase in Rise = 



:{ 4 0»C-25°c}xL 155OC -( 40Oc + 1Q5Oc )l = 1 3 Oc 
l[ 80°C Ij 



The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then 
equal to the sum of the Temperature Rise Limit from 12.43 and the calculated Increase in Rise. For 
this example that total is 105°C + 1 3°C = 1 18°C. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 1 2, Page 1 9 



1 2.44 VARIATION FROM RATED VOLTAGE AND RATED FREQUENCY 

12.44.1 Running 

Alternating-current motors shall operate successfully under running conditions at rated load with a 
variation in the voltage or the frequency up to the following: 

a. Plus or minus 10 percent of rated voltage, with rated frequency for induction motors. 

b. Plus or minus 6 percent of rated voltage, with rated frequency for universal motors. 

c. Plus or minus 5 percent of rated frequency, with rated voltage. 

d. A combined variation in voltage and frequency of 10 percent (sum of absolute values) of the rated 
values, provided the frequency variation does not exceed plus or minus 5 percent of rated 
frequency, and the voltage variation of universal motors (except fan motors) does not exceed plus 
or minus 6 percent of rated voltage. 

Performance within these voltage and frequency variations will not necessarily be in accordance with the 
standards established for operation at rated voltage and frequency. 

12.44.2 Starting 

Medium motors shall start and accelerate to running speed a load which has a torque characteristic and 
an inertia value not exceeding that listed in 12.54 with the voltage and frequency variations specified in 
12.44.1. 

The limiting values of voltage and frequency under which a motor will successfully start and accelerate to 
running speed depend on the margin between the speed-torque curve of the motor at rated voltage and 
frequency and the speed-torque curve of the load under starting conditions. Since the torque developed 
by the motor at any speed is approximately proportional to the square of the voltage and inversely 
proportional to the square of the frequency, it is generally desirable to determine what voltage and 
frequency variations will actually occur at each installation, taking into account any voltage drop resulting 
from the starting current drawn by the motor. This information and the torque requirements of the driven 
machine define the motor-speed-torque curve, at rated voltage and frequency, which is adequate for the 
application. 

12.45 VOLTAGE UNBALANCE 

Alternating-current polyphase motors shall operate successfully under running conditions at rated load 
when the voltage unbalance at the motor terminals does not exceed 1 percent. Performance will not 
necessarily be the same as when the motor is operating with a balanced voltage at the motor terminals 
(see 14.36). 

12.46 VARIATION FROM RATED SPEED 

The variation from the nameplate or published data speed of alternating-current, single-phase and 
polyphase, medium motors shall not exceed 20 percent of the difference between synchronous speed 
and rated speed when measured at rated voltage, frequency, and load and with an ambient temperature 
of25°C. 

12.47 NAMEPLATE AMPERES— ALTERNATING-CURRENT MEDIUM MOTORS 

When operated at rated voltage, rated frequency, and rated horsepower output, the input in amperes 
shall not vary from the nameplate value by more than 10 percent. 

1 2.48 OCCASIONAL EXCESS CURRENT 

Polyphase motors having outputs not exceeding 500 horsepower (according to this part) and rated 
voltages not exceeding 1kV shall be capable of withstanding a current equal to 1.5 times the full load 
rated current for not less than two minutes when the motor is initially at normal operating temperature. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 20 



Section II 
TESTS AND PERFORMANCE— AC MOTORS 



Repeated overloads resulting in prolonged operation at winding temperatures above the maximum values 
given by 12.43 will result in reduced insulation life. 

12.49 STALL TIME 

Polyphase motors having outputs not exceeding 500 horsepower and rated voltage not exceeding 1 kV 
shall be capable of withstanding locked-rotor current for not less than 12 seconds when the motor is 
initially at normal operating temperatures. 

Motors specially designed for inertia loads greater than those in Table 12-7 shall be marked on the 
nameplate with the permissible stall time in seconds. 

1 2.50 PERFORMANCE OF MEDIUM MOTORS WITH DUAL VOLTAGE RATING 

When a medium motor is marked with a broad range or dual voltage the motor shall meet all performance 
requirements of MG 1 over the marked voltage range. 

1 2.51 SERVICE FACTOR OF ALTERNATING-CURRENT MOTORS 

1 2.51 .1 General-Purpose Alternating-Current Motors of the Open Type 

When operated at rated voltage and frequency, general-purpose alternating-current motors of the open 
type shall have a service factor in accordance with Table 12-4 (see 14.37). 

Table 12-4 
SERVICE FACTORS 



Service Factor 



Synchronous Speed, Rpm 



JlE_ 



3600 



1800 



1200 



900 



720 



600 



514 



1/20 
1/12 

1/8 

1/6 

1/4 

1/3 

1/2 

3/4 

1 

1-1/2-125 

150 
200 
250 
300 
350 
400 
450 
500 



1.4 


1.4 


1.4 


1.4 




1.4 


1.4 


1.4 


1.4 




1.4 


1.4 


1.4 


1.4 


Small 


1.35 


1.35 


1.35 


1.35 


Motors 


1.35 


1.35 


1.35 


1.35 




1.35 


1.35 
1.25 
1.25 


1.35 
1.25 


1.35 




1.25 


1.15* 

1.15* 
1.15* 


Medium 


1.25 


1.15* 
1.15* 


Motors 


1.25 


1.15* 





1.15* 
1.15* 
1.15* 
1.0 
1.0 
1.0 
1.0 
1.0 
1.0 



1.15* 
1.15* 
1.15* 
1.15* 
1.15* 
1.15* 
1.15* 
1.15* 
1.15* 



1.15* 
1.15* 

1.15* 
1.15* 
1.15* 
1.15* 



1.15* 
1.15* 
1.15* 
1.15* 



1.15* 
1.15* 
1.15* 



1.15* 
1.15* 



1.15* 



*ln the case of polyphase squirrel-cage motors, these service factors apply only to Design A, B, and C motors 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 21 



12.51.2 Other Motors 

When operated at rated voltage and frequency, other open-type and all totally enclosed alternating- 
current motors shall have a service factor of 1 .0. 

In those applications requiring an overload capacity, the use of a higher horsepower rating, as given in 
10.32.4, is recommended to avoid exceeding the temperature rises for the class of insulation system 
used and to provide adequate torque capacity. 

1 2.52 OVERSPEEDS FOR MOTORS 

12.52.1 Squirrel-Cage and Wound-Rotor Motors 

Squirrel-cage and wound-rotor induction motors, except crane motors, shall be so constructed that, in an 
emergency not to exceed 2 minutes, they will withstand without mechanical injury overspeeds above 
synchronous speed in accordance with the following. During this overspeed condition the machine is not 
electrically connected to the supply. 



Hp 


Synchronous 
Speed, Rpm 


Overspeed, Percent 

of Synchronous 

Speed 


200 and smaller 


1801 and over 


25 




1201 to 1800 


25 




1200 and below 


50 


250-500, incl. 


1801 and over 


20 




1800 and below 


25 



12.52.2 General-Purpose Squirrel-Cage Induction Motors 

General-purpose squirrel-cage induction motors for the ratings specified in Table 12-5 and horsepower 
per frame assignments per Part 1 3 shall be mechanically constructed so as to be capable of operating 
continuously at the rated load at speeds not less than the speed indicated in Table 12-5 when directly 
coupled. Those motors for which this speed is greater than synchronous speed at 60 Hz shall be capable 
of withstanding overspeed, not to exceed 2 minutes, of 10 percent above the speed indicated in Table 12- 
5 without mechanical damage. For motors where the speed in Table 12-5 is equal to synchronous speed 
at 60 Hz, the overspeed limits in 12.52.1 shall apply, assuming the motor is not energized when the 
overspeed occurs. 

Table 12-5 does not apply to motors used in belted applications. For belted applications, consult the 
motor manufacturer. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 22 



Section II 
TESTS AND PERFORMANCE— AC MOTORS 



Table 12-5 

CONTINUOUS SPEED CAPABILITY FOR GENERAL-PURPOSE SQUIRREL-CAGE INDUCTION MOTORS 

IN DIRECT COUPLED APPLICATIONS, EXCEPT THOSE MOTORS IN TABLE 12-6 





Totally 


Enclosed Fan 


-Cooled 






Open Dripproof 




* 


Synchronous Speed at 60 Hz 




3600 


1800 


1200 




3600 


1800 


1200 




Horsepower 






Minimum 


Design 


Speed 








1/4 


5200 


3600 


2400 




5200 


3600 


2400 




1/3 


5200 


3600 


2400 




5200 


3600 


2400 




1/2 


5200 


3600 


2400 




5200 


3600 


2400 




3/4 


5200 


3600 


2400 




5200 


3600 


2400 




1 


5200 


3600 


2400 




5200 


3600 


2400 




1.5 


5200 


3600 


2400 




5200 


3600 


2400 




2 


5200 


3600 


2400 




5200 


3600 


2400 




3 


5200 


3600 


2400 




5200 


3600 


2400 




5 


5200 


3600 


2400 




5200 


3600 


2400 




7.5 


4500 


2700 


2400 




5200 


2700 


2400 




10 


4500 


2700 


2400 




4500 


2700 


2400 




15 


4500 


2700 


2400 




4500 


2700 


2400 




20 


4500 


2700 


2400 




4500 


2700 


2400 




25 


4500 


2700 


1800 




4500 


2700 


1800 




30 


4500 


2700 


1800 




4500 


2700 


1800 





(Table continued on following page.) 
Table 12-5 (Continued) 
CONTINUOUS SPEED CAPABILITY FOR GENERAL-PURPOSE SQUIRREL-CAGE INDUCTION MOTORS 
IN DIRECT COUPLED APPLICATIONS, EXCEPT THOSE MOTORS IN TABLE 12-6 





Totally 


Enclosed Fan 


-Cooled 






Open Dripproof 




Synchronous Speed at 60 Hz 




3600 


1800 


1200 




3600 


1800 


1200 


Horsepower 






Minimum 


Design 


Speed 






40 


3600 


2300 


1800 




4500 


2300 


1800 


50 


3600 


2300 


1800 




3600 


2300 


1800 


60 


3600 


2300 


1800 




3600 


2300 


1800 


75 


3600 


2300 


1800 




3600 


2300 


1800 


100 


3600 


2300 


1800 




3600 


2300 


1800 


125 


3600 


2300 


1800 




3600 


2300 


1800 


150 


3600 


2300 


1800 




3600 


2300 


1800 


200 


3600 


2300 


1800 




3600 


2300 


1800 


250 


3600 


2300 


1200 




3600 


2300 


1200 


300 


3600 


1800 


1200 




3600 


2300 


1200 


350 


3600 


1800 


1200 




3600 


1800 


1200 


400 


3600 


1800 


- 




3600 


1800 


. 


450 


3600 


1800 


- 




3600 


1800 


_ 


500 


3600 


1800 


" 




3600 


1800 


- 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 23 

12.52.3 General-Purpose Design A and B Direct-Coupled Squirrel-Cage Induction Motors 

General-purpose Design A and B (TS shaft for motors above the 250 frame size) squirrel-cage induction 
motors for the ratings specified in Table 12-6 and horsepower per frame assignments per Part 13 shall be 
capable of operating mechanically constructed so as to be capable of operating continuously at the rated 
load at speeds not less than the speed indicated in Table 12-6 when directly coupled. Those motors for 
which this speed is greater than the synchronous speed at 60 Hz shall be capable of withstanding 
overspeeds, not to exceed 2 minutes, of 10 percent above the speed indicated in Table 12-6without 
mechanical damage. For motors where the speed in Table 12-6 is equal to synchronous speed at 60 Hz, 
the overspeed limits in 12.52.1 shall apply, assuming the motor is not energized when the overspeed 
occurs. 

Table 12-6 does not apply to motors used in belted applications. For belted applications consult the motor 
manufacturer. 

12.52.4 Alternating-Current Series and Universal Motors 

Alternating-current series and universal motors shall be so constructed that, in an emergency not to 
exceed 2 minutes, they will withstand without mechanical injury an overspeed of 10 percent above the 
no-load speed 1 at rated voltages. 



1 For motors which are integrally attached to loads that cannot become accidentally disconnected, the words "no-load speed" shall 
be interpreted to mean the lightest load condition possible with the load. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 24 TESTS AND PERFORMANCE— AC MOTORS 



Table 12-6 

CONTINUOUS SPEED CAPABILITY FOR GENERAL-PURPOSE DESIGN A AND B DIRECT COUPLED (TS 

SHAFT FOR MOTORS ABOVE THE 250 FRAME SIZE) SQUIRREL-CAGE INDUCTION MOTORS 



Totally Enclosed Fan-Cooled 


Open Dripproof 




Synchronous Speed at 60 Hz 


3600 1800 1200 3600 


1800 


1200 



Horsepower Minimum Design Speed 



1/4 


7200 


3600 


2400 


7200 


3600 


2400 


1/3 


7200 


3600 


2400 


7200 


3600 


2400 


1/2 


7200 


3600 


2400 


7200 


3600 


2400 


3/4 


7200 


3600 


2400 


7200 


3600 


2400 


1 


7200 


3600 


2400 


7200 


3600 


2400 


1.5 


7200 


3600 


2400 


7200 


3600 


2400 


2 


7200 


3600 


2400 


7200 


3600 


2400 


3 


7200 


3600 


2400 


7200 


3600 


2400 


5 


7200 


3600 


2400 


7200 


3600 


2400 


7.5 


5400 


3600 


2400 


7200 


3600 


2400 


10 


5400 


3600 


2400 


5400 


3600 


2400 


15 


5400 


3600 


2400 


5400 


3600 


2400 


20 


5400 


3600 


2400 


5400 


3600 


2400 


25 


5400 


2700 


2400 


5400 


2700 


2400 


30 


5400 


2700 


2400 


5400 


2700 


2400 


40 


4500 


2700 


2400 


5400 


2700 


2400 


50 


4500 


2700 


2400 


4500 


2700 


2400 


60 


3600 


2700 


2400 


4500 


2700 


2400 


75 


3600 


2700 


2400 


3600 


2700 


2400 


100 


3600 


2700 


1800 


3600 


2700 


1800 


125 


3600 


2700 


1800 


3600 


2700 


1800 


150 


3600 


2700 


1800 


3600 


2700 


1800 


200 


3600 


2300 


1800 


3600 


2700 


1800 


250 


3600 


2300 


1800 


3600 


2300 


1800 


300 


3600 


2300 


1800 


3600 


2300 


1800 


350 


3600 


1800 


1800 


3600 


1800 


1800 


400 


3600 


1800 


. 


3600 


1800 


- 


450 


3600 


1800 


- 


3600 


1800 


- 


500 


3600 


1800 


- 


3600 


1800 


- 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 25 



12.53 MACHINE SOUND (MEDIUM INDUCTION MOTORS) 

See Part 9 for Sound Power Limits and Measurement Procedures. 

12.54 NUMBER OF STARTS 

12.54.1 Normal Starting Conditions 

Design A and B squirrel-cage induction motors having horsepower ratings given in 10.32.4 and 
performance characteristics in accordance with this Part 12 shall be capable of accelerating without 
injurious heating load Wk 2 referred to the motor shaft equal to or less than the values listed in Table 12-7 
under the following conditions: 

a. Applied voltage and frequency in accordance with 12.44. 

b. During the accelerating period, the connected load torque is equal to or less than a torque which 
varies as the square of the speed and is equal to 100 percent of rated-load torque at rated speed. 

c. Two starts in succession (coasting to rest between starts) with the motor initially at the ambient 
temperature or one start with the motor initially at a temperature not exceeding its rated load 
operating temperature. 

!The values of Wk 2 of connected load given in Table 12-7 were calculated from the following formula and 
larger values rounded to three significant figures: 



Load Wk^ 



Hp' 



0.95 



[lOOOJ j 



-0.0685 



Hp 



1.5 



fRPMV" 8 

JjoooJ J 



Where: 

A = 24 for 300 to 1800 rpm, inclusive, motors 

A = 27 for 3600 rpm motors 



12.54.2 Other than Normal Starting Conditions 

If the starting conditions are other than those stated in 12.54.1, the motor manufacturer should be 
consulted. 

1 2.54.3 Considerations for Additional Starts 

When additional starts are required, it is recommended that none be made until all conditions affecting 
operation have been thoroughly investigated and the apparatus examined for evidence of excessive 
heating. It should be recognized that the number of starts should be kept to a minimum since the life of 
the motor is affected by the number of starts. 

12.55 ROUTINE TESTS FOR POLYPHASE MEDIUM INDUCTION MOTORS 
1 2.55.1 Method of Testing 

The method of testing polyphase induction motors shall be in accordance with IEEE Std 112. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

p art 12, Page 26 TESTS AND PERFORMANCE— AC MOTORS 

12.55.2 Typical Tests on Completely Assembled Motors 

Typical tests which may be made on motors completely assembled in the factory and furnished with shaft 
and complete set of bearings are as follows: 

a. Measurement of winding resistance. 

b. No-load readings of current and speed at normal voltage and frequency. On 50 hertz motors, 
these readings may be taken at 60 hertz. 

c. Current input at rated frequency with rotor at standstill for squirrel-cage motors. This may be taken 
single-phase or polyphase at rated or reduced voltage. (When this test is made single-phase, the 
polyphase values of a duplicate machine should be given in any report.) On 50 hertz motors, 
these readings may be taken at 60 hertz. 

d. Measurement of open-circuit voltage ratio on wound-rotor motors. 

e. High-potential test in accordance with 3.1 and 12.3. 

12.55.3 Typical of Tests on Motors Not Completely Assembled 

Typical tests which may be made on all motors not completely assembled in the factory are as follows. 

a. Measurement of winding resistance. 

b. High-potential test in accordance with 3.1 and 12.3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 27 



HP 



1 

VA 
2 
3 
5 

VA 
10 
15 



3600 



1.8 
2.4 
3.5 
5.7 

8.3 
11 
16 



Table 12-7 
SQUIRREL-C AGE INDUCTION MOTORS 

Synchronous Speed, Rpm 



1800 



1200 



900 



720 



600 



Load Wk* (Exclusive of Motor Wk'), Lb-Ft 



5.8 
8.6 
11 

17 
27 

39 

51 
75 



15 
23 
30 
44 

71 

104 
137 
200 



31 
45 
60 
87 
142 

208 
273 
400 



20 


21 


99 


262 


525 


25 


26 


122 


324 


647 


30 


30 


144 


384 


769 


40 


40 


189 


503 


1010 


50 


49 


232 


620 


1240 


60 


58 


275 


735 


1470 


75 


71 


338 


904 


1810 


100 


92 


441 


1180 


2370 


125 


113 


542 


1450 


2920 


150 


133 


640 


1720 


3460 


200 


172 


831 


2240 


4510 


250 


210 


1020 


2740 


5540 


300 


246 


1200 


3240 




350 


281 


1370 


3720 




400 


315 


1550 






450 


349 


1710 






500 


381 


1880 







53 
77 
102 
149 
242 

355 

467 
684 
898 
1110 

1320 
1720 
2130 
2520 
3110 

4070 
5010 
5940 
7750 



82 
120 
158 
231 

375 

551 
723 

1060 
1390 
1720 

2040 
2680 
3300 
3920 
4830 

6320 
7790 
9230 



514 



118 
174 
228 
335 

544 

799 
1050 
1540 
2020 
2490 

2960 
3890 
4790 
5690 
7020 

9190 
11300 



12.56 THERMAL PROTECTION OF MEDIUM MOTORS 

The protector in a thermally protected motor shall limit the winding temperature and the ultimate trip 
current as follows: 

12.56.1 Winding Temperature 
12.56.1.1 Running Load 

When a motor marked "Thermally Protected" is running at the maximum continuous load which it can 
carry without causing the protector to open the circuit, the temperature of the windings shall not exceed 
the temperature shown in Table 12-8. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 2, Page 28 TESTS AND PERFORMANCE— AC MOTORS 



Table 12-8 
WINDING TEMPERATURES 



Insulation System Class 


Maximum Winding Temperature, 
Degrees C 


A 


140 


B 


165 


F 


190 


H 


215 



Tests shall be conducted at any ambient temperature within the range of 10°C to 40°C. 

The temperature of the windings shall be measured by the resistance method except that, for motors 
rated 15 horsepower and smaller, the temperature shall alternatively per permitted to be measured by the 
thermocouple method. 

Short-time rated motors and motors for intermittent duty shall be permitted to be run at no-load and 
reduced voltage, if necessary, for a continuous running test to verify that the protector limits the 
temperatures to those given in the foregoing table. 

12.56.1.2 Locked Rotor 

When a motor marked "Thermally Protected" is under locked-rotor conditions, the thermal protector shall 
cycle to limit the winding temperature to the values given in Table 12-9. 

The test for motors with automatic-reset thermal protectors shall be run until temperature peaks are 
constant or for 72 hours, whichever is shorter. 

The test for motors with manual-reset thermal protectors shall be 10 cycles, the protector being reclosed 
as quickly as possible after it opens. If ten cycles are completed in less than 1 hour, only the "during first 
hour" limits given in Table 12-9 apply. 

Table 12-9 
WINDING TEMPERATURE UNDER LOCKED-ROTOR CONDITIONS, DEGREES C 



Maximum Temperature, Degrees C* Average Temperature, **Degrees C* 

Insulation System Class Insulation System Class 

Type of 

Protector A B F H A B F H 

Automatic reset 
During first hour 200 225 250 275 

After first hour 175 200 225 250 1 50 1 75 200 225 



Manual reset 










During first hour 


200 


225 


250 


275 


After first hour 


175 


200 


225 


250 



* Test shall be permitted to be conducted at any ambient temperature within the range of 10°C to 40°C. 

**The average temperature is the average of the average peak and average reset winding temperatures. The average temperature 
shall be within limits during both the second and last hours of the test. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 1 2, Page 29 

12.56.2 Trip Current 

A motor rated more than 1 horsepower and marked "Thermally Protected" shall have an ultimate trip 
current, based on a 40°C ambient temperature, not in excess of the following percentages of motor full- 
load currents: 



Motor Full-Load Amperes 


Trip Current as a Percent of 
Motor Full-Load Current 


9.0 and less 


170 


Over 9.0 but not over 20.0 


156 


Over 20.0 


140 



Dual-voltage motors shall comply with the ultimate trip current requirements for both voltages. 

12.57 OVERTEMPERATURE PROTECTION OF MEDIUM MOTORS NOT MEETING THE 
DEFINITION OF "THERMALLY PROTECTED" 

Motors rated above 1 horsepower and marked "OVER TEMP PROT-" are provided with winding 
overtemperature protection devices or systems which do not meet the definition of "Thermally Protected." 

The motors marked "OVER TEMP PROT-" shall be followed by the numeral 1 , 2, or 3 stamped in the 
blank space to indicate the type of winding overtemperature protection provided. For each type, the 
winding overtemperature protector shall limit the temperature of the winding as follows. 

12.57.1 Type 1 — Winding Running and Locked Rotor Overtemperature Protection 

12.57.1.1 Winding Running Temperature 

When the motor is marked "OVER TEMP PROT-1" and is running at the maximum continuous load which 
it can carry without causing the winding overtemperature protector to operate, the temperature of the 
windings shall not exceed the temperature shown in Table 12-8. 

The temperature of the windings shall be measured by the resistance method except that, for motors 
rated 15 horsepower and smaller, the temperature shall be permitted to be measured by the 
thermocouple method. 

12.57.1.2 Winding Locked-Rotor Temperature 

In addition, when the motor is marked "OVER TEMP PROT-1" and is under locked-rotor conditions, the 
winding overtemperature protector shall limit the temperature of the windings to the values shown in 
Table 12-8. 

12.57.2 Type 2 — Winding Running Overtemperature Protection 

When the motor is marked "OVER TEMP PROT-2" and is running at the maximum continuous load which 
it can carry without causing the winding overtemperature protector to operate, the temperature of the 
windings shall not exceed the temperature shown in Table 12-8. 

When the motor is so marked, locked-rotor protection is not provided by the winding overtemperature 
protector. 

12.57.3 Type 3 — Winding Overtemperature Protection, Nonspecific Type 

When the motor is marked "OVER TEMP PROT-3," the motor manufacturer shall be consulted for details 
of protected conditions or winding temperatures, or both. 

12.58 EFFICIENCY 

12.58.1 Determination of Motor Efficiency and Losses 

Efficiency and losses shall be determined in accordance with IEEE Std 1 12 or Canadian Standards 
Association Standard C390. The efficiency shall be determined at rated output, voltage, and frequency. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 30 TESTS AND PERFORMANCE— AC MOTORS 



Unless otherwise specified, horizontal polyphase, squirrel-cage medium motors rated 1 to 500 
horsepower shall be tested by dynamometer (Method B) 1 as described in Section 6.4 of IEEE Std 112. 
Motor efficiency shall be calculated using form B of IEEE Std 1 12 or the equivalent C390 calculation 
procedure. Vertical motors of this horsepower range shall also be tested by Method B if bearing 
construction permits; otherwise they shall be tested by segregated losses (Method E) 2 as described in 
Section 6.6 of IEEE Std 1 12, including direct measurement of stray-loss load. 

The following losses shall be included in determining the efficiency: 

a. Stator l 2 R 

b. Rotor l 2 R 

c. Core loss 

d. Stray load loss 

e. Friction and windage loss 3 

f. Brush contact loss of wound-rotor machines 

Power required for auxiliary items, such as external pumps or fans, that are necessary for the operation 
of the motor shall be stated separately. 

In determining l 2 R losses at all loads, the resistance of each winding shall be corrected to a temperature 
equal to an ambient temperature of 25°C plus the observed rated load temperature rise measured by 
resistance. When the rated load temperature rise has not been measured, the resistance of the winding 
shall be corrected to the following temperature: 



Class of Insulation System 


Temperature, Degrees C 


A 


75 


B 


95 


F 


115 


H 


130 



If the rated temperature rise is specified as that of a lower class of insulation system, the temperature for 
resistance correction shall be that of the lower insulation class. 

12.58.2 Efficiency of Polyphase Squirrel-Cage Medium Motors with Continuous Ratings 

The full-load efficiency of Design A and B single-speed polyphase squirrel-cage medium motors in the 
range of 1 through 400 horsepower for frames assigned in accordance with Part 13, above 400 
horsepower up to and including 500 horsepower, and equivalent Design C ratings shall be identified on 
the nameplate by a nominal efficiency selected from the Nominal Efficiency column in Table 12-10 which 
shall be not greater than the average efficiency of a large population of motors of the same design. 

The efficiency shall be identified on the nameplate by the caption "NEMA Nominal Efficiency" or "NEMA 
Norn. Eff." 

The full-load efficiency, when operating at rated voltage and frequency, shall be not less than the 
minimum value associated with the nominal value in Table 12-10. 



1 CSA Std C390 Method 1. 

2 CSA Std C390 Method 2. 

3 In the case of motors which are furnished with thrust bearings, only that portion of the thrust bearing loss produced by the motor 
itself shall be included in the efficiency calculation. Alternatively, a calculated value of efficiency, including bearing loss due to 
external thrust load, shall be permitted to be specified. 

In the case of motors which are furnished with less than a full set of bearings, friction and windage losses, which are representative 
of the actual installation, shall be determined by calculation or experience with shop test bearings, and shall be included in the 
efficiency calculation. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 31 







Table 12-10 
EFFICIENCY LEVELS 




Nominal 
Efficiency 


Minimum Efficiency 

Based on 20% Loss 

Difference 


Nominal 
Efficiency 


Minimum Efficiency 

Based on 20% Loss 

Difference 


99.0 




98.8 


91.0 


89.5 


98.9 




98.7 


90.2 


88.5 


98.8 




98.6 


89.5 


87.5 


98.7 




98.5 


88.5 


86.5 


98.6 




98.4 


87.5 


85.5 


98.5 




98.2 


86.5 


84.0 


98.4 




98.0 


85.5 


82.5 


98.2 




97.8 


84.0 


81.5 


98.0 




97.6 


82.5 


80.0 


97.8 




97.4 


81.5 


78.5 


97.6 




97.1 


80.0 


77.0 


97.4 




96.8 


78.5 


75.5 


97.1 




96.5 


77.0 


74.0 


96.8 




96.2 


75.5 


72.0 


96.5 




95.8 


74.0 


70.0 


96.2 




95.4 


72.0 


68.0 


95.8 




95.0 


70.0 


66.0 


95.4 




94.5 


68.0 


64.0 


95.0 




94.1 


66.0 


62.0 


94.5 




93.6 


64.0 


59.5 


94.1 




93.0 


62.0 


57.5 


93.6 




92.4 


59.5 


55.0 


93.0 




91.7 


57.5 


52.5 


92.4 




91.0 


55.0 


50.5 


91.7 




90.2 


52.5 

50.5 


48.0 
46.0 



Variations in materials, manufacturing processes, and tests result in motor-to-motor efficiency variations 
for a given motor design; the full-load efficiency for a large population of motors of a single design is not a 
unique efficiency but rather a band of efficiency. Therefore, Table 12-10 has been established to indicate 
a logical series of nominal motor efficiencies and the minimum associated with each nominal. The 
nominal efficiency represents a value which should be used to compute the energy consumption of a 
motor or group of motors. 

12.59 EFFICIENCY LEVELS OF ENERGY EFFICIENT POLYPHASE SQUIRREL-CAGE INDUCTION 
MOTORS 

The nominal full-load efficiency of polyphase squirrel-cage induction motors rated 600 volts or less 
determined in accordance with 12.58.1, identified on the nameplate in accordance with 12.58.2, and 
having a corresponding minimum efficiency in accordance with Table 12-10 shall equal or exceed the 
values listed in Table 12-1 1 for the motor to be classified as "energy efficient." 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 32 TESTS AND PERFORMANCE— AC MOTORS 



12.60 EFFICIENCY LEVEL OF PREMIUM EFFICIENCY ELECTRIC MOTORS 

12.60.1 60 Hz MOTORS RATED 600 VOLTS OR LESS (RANDOM WOUND) 

The nominal full-load efficiency of random wound premium efficiency electric motors rated 600 volts or 
less determined in accordance with 12.58.1, identified on the nameplate in accordance with 12.58.2, and 
having a minimum efficiency in accordance with Table 12-10 shall equal or exceed the values listed in 
Table 12-12. 

12.60.2 60 Hz MOTORS RATED MEDIUM VOLTAGE, 5000 VOLTS OR LESS (FORM WOUND) 

The nominal full-load efficiency of form wound premium efficiency electric motors rated at a medium 
voltage of 5000 volts or less determined in accordance with 12.58.1, identified on the nameplate in 
accordance with 12.58.2, and having a minimum efficiency in accordance with Table 12-10 shall equal or 
exceed the values listed in Table 12-13. 

12.60.3 50 Hz MOTORS RATED 600 VOLTS OR LESS (RANDOM WOUND) 

The nominal full-load efficiency of random wound 50 Hz premium efficiency electric motors rated 600 
volts or less determined in accordance with 12.58.1, identified on the nameplate in accordance with 
12.58.2, and having a minimum efficiency in accordance with Table 12-10 shall equal or exceed the 
values listed in Table 12-14. 

| The values of efficiency in Table 12-14 for (0.7457»Hp) < 200 kW were derived based on the following 
equation 1 : 

%Efficiency = A*[log 10 (0.7457» Hp)] 3 + B*[log ]0 (0.7457* Hp)] 2 + O log 10 (0.7457* Hp)+ D 
I where the values of A, B, C, and D are as given in the following table: 



2 Pole 4 Pole 6 Pole 

"A 0.3569 0.0773 0.1252 

B -3.3076 -1.8951 -2.613 

C 11.6108 9.2984 11.9963 

D 82.2503 83.7025 80.4769 



The above relationship can be used to calculate the efficiency in percent for Hp levels which are not given 
| specifically in Table 12-14. 

12.61 REPORT OF TEST FOR TESTS ON INDUCTION MOTORS 

For reporting routine tests on induction motors, see IEEE Standard 112, Appendix A. 



1 Based on efficiency level IE3 in IEC 60034-30 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 33 



Table 12-11 
FULL-LOAD EFFICIENCIES OF ENERGY EFFICIENT MOTORS 



OPEN MOTORS 




2 POLE 


4 POLE 


6 POLE 


8 POLE 




Nominal 


Minimum 


Nominal 


Minimum 


Nominal 


Minimum 


Nominal 


Minimum 


Hp 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


1 






82.5 


80.0 


80.0 


77.0 


74.0 


70.0 


1.5 


82.5 


80.0 


84.0 


81.5 


84.0 


81.5 


75.5 


72.0 


2 


84.0 


81.5 


84.0 


81.5 


85.5 


82.5 


85.5 


82.5 


3 


84.0 


81.5 


86.5 


84.0 


86.5 


84.0 


86.5 


84.0 


5 


85.5 


82.5 


87.5 


85.5 


87.5 


85.5 


87.5 


85.5 


7.5 


87.5 


85.5 


88.5 


86.5 


88.5 


86.5 


88.5 


86.5 


10 


88.5 


86.5 


89.5 


87.5 


90.2 


88.5 


89.5 


87.5 


15 


89.5 


87.5 


91.0 


89.5 


90.2 


88.5 


89.5 


87.5 


20 


90.2 


88.5 


91.0 


89.5 


91.0 


89.5 


90.2 


88.5 


25 


91.0 


89.5 


91.7 


90.2 


91.7 


90.2 


90.2 


88.5 


30 


91.0 


89.5 


92.4 


91.0 


92.4 


91.0 


91.0 


89.5 


40 


91.7 


90.2 


93.0 


91.7 


93.0 


91.7 


91.0 


89.5 


50 


92.4 


91.0 


93.0 


91.7 


93.0 


91.7 


91.7 


90.2 


60 


93.0 


91.7 


93.6 


92.4 


93.6 


92.4 


92.4 


91.0 


75 


93.0 


91.7 


94.1 


93.0 


93.6 


92.4 


93.6 


92.4 


100 


93.0 


91.7 


94.1 


93.0 


94.1 


93.0 


93.6 


92.4 


125 


93.6 


92.4 


94.5 


93.6 


94.1 


93.0 


93.6 


92.4 


150 


93.6 


92.4 


95.0 


94.1 


94.5 


93.6 


93.6 


92.4 


200 


94.5 


93.6 


95.0 


94.1 


94.5 


93.6 


93.6 


92.4 


250 


94.5 


93.6 


95.4 


94.5 


95.4 


94.5 


94.5 


93.6 


300 


95.0 


94.1 


95.4 


94.5 


95.4 


94.5 






350 


95.0 


94.1 


95.4 


94.5 


95.4 


94.5 






400 


95.4 


94.5 


95.4 


94.5 










450 


95.8 


95.0 


95.8 


95.0 










500 


95.8 


95.0 


95.8 


95.0 











Table 12-11 continued next page 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 34 








TESTS AND PERFORMANCE- 


Section II 
AC MOTORS 


Table 12-11 (Continued) 
FULL-LOAD EFFICIENCIES OF ENERGY EFFICIENT MOTORS 




ENCLOSED MOTORS 




2 POLE 


4 POLE 


6 POLE 


8 POLE 


Hp 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


1.0 


75.5 


72.0 


82.5 


80.0 


80.0 


77.0 


74.0 


70.0 


1.5 


82.5 


80.0 


84.0 


81.5 


85.5 


82.5 


77.0 


74.0 


2.0 


84.0 


81.5 


84.0 


81.5 


86.5 


84.0 


82.5 


80.0 


3.0 


85.5 


82.5 


87.5 


85.5 


87.5 


85.5 


84.0 


81.5 


5.0 


87.5 


85.5 


87.5 


85.5 


87.5 


85.5 


85.5 


82.5 


7.5 


88.5 


86.5 


89.5 


87.5 


89.5 


87.5 


85.5 


82.5 


10.0 


89.5 


87.5 


89.5 


87.5 


89.5 


87.5 


88.5 


86.5 


15.0 


90.2 


88.5 


91.0 


89.5 


90.2 


88.5 


88.5 


86.5 


20.0 


90.2 


88.5 


91.0 


89.5 


90.2 


88.5 


89.5 


87.5 


25.0 


91.0 


89.5 


92.4 


91.0 


91.7 


90.2 


89.5 


87.5 


30.0 


91.0 


89.5 


92.4 


91.0 


91.7 


90.2 


91.0 


89.5 


40.0 


91.7 


90.2 


93.0 


91.7 


93.0 


91.7 


91.0 


89.5 


50.0 


92.4 


91.0 


93.0 


91.7 


93.0 


91.7 


91.7 


90.2 


60.0 


93.0 


91.7 


93.6 


92.4 


93.6 


92.4 


91.7 


90.2 


75.0 


93.0 


91.7 


94.1 


93.0 


93.6 


92.4 


93.0 


91.7 


100.0 


93.6 


92.4 


94.5 


93.6 


94.1 


93.0 


93.0 


91.7 


125.0 


94.5 


93.6 


94.5 


93.6 


94.1 


93.0 


93.6 


92.4 


150.0 


94.5 


93.6 


95.0 


94.1 


95.0 


94.1 


93.6 


92.4 


200.0 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


94.1 


93.0 


250.0 


95.4 


94.5 


95.0 


94.1 


95.0 


94.1 


94.5 


93.6 


300.0 


95.4 


94.5 


95.4 


94.5 


95.0 


94.1 






350.0 


95.4 


94.5 


95.4 


94.5 


95.0 


94.1 






400.0 


95.4 


94.5 


95.4 


94.5 










450.0 


95.4 


94.5 


95.4 


94.5 










500.0 


95.4 


94.5 


95.8 


95.0 











> Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 35 



Table 12-12 

FULL-LOAD EFFICIENCIES FOR 60 HZ PREMIUM EFFICIENCY ELECTRIC MOTORS 

RATED 600 VOLTS OR LESS (RANDOM WOUND) 



OPEN MOTORS 




2 POLE 


4 POLE 


6 POLE 


HP 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


1 


77.0 


74.0 


85.5 


82.5 


82.5 


80.0 


1.5 


84.0 


81.5 


86.5 


84.0 


86.5 


84.0 


2 


85.5 


82.5 


86.5 


84.0 


87.5 


85.5 


3 


85.5 


82.5 


89.5 


87.5 


88.5 


86.5 


5 


86.5 


84.0 


89.5 


87.5 


89.5 


87.5 


7.5 


88.5 


86.5 


91.0 


89.5 


90.2 


88.5 


10 


89.5 


87.5 


91.7 


90.2 


91.7 


90.2 


15 


90.2 


88.5 


93.0 


91.7 


91.7 


90.2 


20 


91.0 


89.5 


93.0 


91.7 


92.4 


91.0 


25 


91.7 


90.2 


93.6 


92.4 


93.0 


91.7 


30 


91.7 


90.2 


94.1 


93.0 


93.6 


92.4 


40 


92.4 


91.0 


94.1 


93.0 


94.1 


93.0 


50 


93.0 


91.7 


94.5 


93.6 


94.1 


93.0 


60 


93.6 


92.4 


95.0 


94.1 


94.5 


93.6 


75 


93.6 


92.4 


95.0 


94.1 


94.5 


93.6 


100 


93.6 


92.4 


95.4 


94.5 


95.0 


94.1 


125 


94.1 


93.0 


95.4 


94.5 


95.0 


94.1 


150 


94.1 


93.0 


95.8 


95.0 


95.4 


94.5 


200 


95.0 


94.1 


95.8 


95.0 


95.4 


94.5 


250 


95.0 


94.1 


95.8 


95.0 


95.4 


94.5 


300 


95.4 


94.5 


95.8 


95.0 


95.4 


94.5 


350 


95.4 


94.5 


95.8 


95.0 


95.4 


94.5 


400 


95.8 


95.0 


95.8 


95.0 


95.8 


95.0 


450 


95.8 


95.0 


96.2 


95.4 


96.2 


95.4 


500 


95.8 


95.0 


96.2 


95.4 


96.2 


95.4 



Table 12-12 continued next page 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 36 



Section It 
TESTS AND PERFORMANCE— AC MOTORS 



Table 12-12 (Continued) 

FULL-LOAD EFFICIENCIES FOR 60 HZ PREMIUM EFFICIENCY ELECTRIC MOTORS 

RATED 600 VOLTS OR LESS (RANDOM WOUND) 



ENCLOSED MOTORS 






2 POLE 


4 POLE 






6 POLE 




Nominal 


Minimum 


Nominal 


Minimum 


Nominal 


Minimum 


HP 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


Efficiency 


1 


77.0 


74.0 


85.5 


82.5 


82.5 


80.0 


1.5 


84.0 


81.5 


86.5 


84.0 


87.5 


85.5 


2 


85.5 


82.5 


86.5 


84.0 


88.5 


86.5 


3 


86.5 


84.0 


89.5 


87.5 


89.5 


87.5 


5 


88.5 


86.5 


89.5 


87.5 


89.5 


87.5 


7.5 


89.5 


87.5 


91.7 


90.2 


91.0 


89.5 


10 


90.2 


88.5 


91.7 


90.2 


91.0 


89.5 


15 


91.0 


89.5 


92.4 


91.0 


91.7 


90.2 


20 


91.0 


89.5 


93.0 


91.7 


91.7 


90.2 


25 


91.7 


90.2 


93.6 


92.4 


93.0 


91.7 


30 


91.7 


90.2 


93.6 


92.4 


93.0 


91.7 


40 


92.4 


91.0 


94.1 


93.0 


94.1 


93.0 


50 


93.0 


91.7 


94.5 


93.6 


94.1 


93.0 


60 


93.6 


92.4 


95.0 


94.1 


94.5 


93.6 


75 


93.6 


92.4 


95.4 


94.5 


94.5 


93.6 


100 


94.1 


93.0 


95.4 


94.5 


95.0 


94.1 


125 


95.0 


94.1 


95.4 


94.5 


95.0 


94.1 


150 


95.0 


94.1 


95.8 


95.0 


95.8 


95.0 


200 


95.4 


94.5 


96.2 


95.4 


95.8 


95.0 


250 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 


300 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 


350 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 


400 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 


450 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 


500 


95.8 


95.0 


96.2 


95.4 


95.8 


95.0 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— AC MOTORS 



MG 1-2009 
Part 12, Page 37 



Table 12-13 



FULL-LOAD EFFICIENCIES FOR 60 HZ PREMIUM EFFICIENCY ELECTRIC MOTORS 
RATED 5000 VOLTS OR LESS (FORM WOUND) 



OPEN MOTORS 




2 POLE 


4 POLE 


6 POLE 


HP 


Nominal Minimum 
Efficiency Efficiency 


Nominal Minimum 
Efficiency Efficiency 


Nominal Minimum 
Efficiency Efficiency 



250 
300 
350 
400 
450 
500 



94.5 
94.5 

94.5 
94.5 
94.5 
94.5 



93.6 
93.6 
93.6 
93.6 
93.6 
93.6 



95.0 
95.0 
95.0 
95.0 
95.0 
95.0 



94.1 
94.1 
94.1 
94.1 
94.1 
94.1 



95.0 
95.0 
95.0 
95.0 
95.0 
95.0 



94.1 
94.1 
94.1 
94.1 
94.1 
94.1 



ENCLOSED MOTORS 



2 POLE 



4 POLE 



6 POLE 



HP 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


Nominal 
Efficiency 


Minimum 
Efficiency 


250 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


300 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


350 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


400 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


450 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 


500 


95.0 


94.1 


95.0 


94.1 


95.0 


94.1 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 2, Page 38 TESTS AND PERFORMANCE— AC MOTORS 







Table 12-14 




| FULL-LOAD EFFICIENCIES FOR 50 HZ PREMIUM EFFICIENCY ELECTRIC MOTORS RATED 


1 


600 VOLTS OR LESS (RANDOM WOUND) 




i 

1 HP 


2 POLE 


4 POLE 


6 POLE 


Efficiency 


Efficiency 


Efficiency 


1 1 


80.7 


82.5 


78.9 


I 1-5 


82.8 


84.2 


81.1 


2 

1 


84.2 


85.3 


82.5 


1 3 


85.9 


86.7 


84.4 


1 5 

1 


87.9 


88.4 


86.5 


1 

I 7.5 


89.2 


89.6 


88.0 


1 10 


90.1 


90.4 


89.0 


I 15 


91.2 


91.5 


90.3 


I 20 


91.9 


92.1 


91.2 


I 25 


92.4 


92.6 


91.8 


f 30 


92.8 


93.0 


92.2 


40 


93.3 


93.5 


92.9 


50 


93.7 


93.9 


93.4 


60 


94.0 


94.2 


93.7 


75 


94.3 


94.6 


94.1 


| 100 


94.7 


95.0 


94.6 


125 


95.0 


95.3 


94.9 


150 


95.2 


95.5 


95.2 


200 


95.5 


95.8 


95.5 


250 


95.7 


95.9 


95.7 


300 


95.8 


96.0 


95.8 


350 


95.8 


96.0 


95.8 


400 


95.8 


96.0 


95.8 


450 


95.8 


96.0 


95.8 


500 


95.8 


96.0 


95.8 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— AC MOTORS Part 12, Page 39 



12.62 MACHINE WITH ENCAPSULATED OR SEALED WINDINGS—CONFORMANCE TESTS 

An alternating-current squirrel-cage machine with encapsulated or sealed windings shall be capable of 
passing the tests listed below. 

After the stator winding is completed, join all leads together leaving enough length to avoid creepage to 
terminals and perform the following tests in the sequence indicated: 

i. The encapsulated or sealed stator shall be tested while all insulated parts are submerged in a 
tank of water containing a wetting agent. The wetting agent shall be non-ionic and shall be added 
in a proportion sufficient to reduce the surface tension of water to a value of 31 dyn/cm (31 x 1 3 
MN/m)orlessat25°C. 

>. Using 500 volts direct-current, take a 10 minute insulation resistance measurement following the 
procedure as outlined in IEEE Std 43. The minimum insulation resistance in megohms shall be > 
5 times the machine rated kilovolts plus 5. 

c. Subject the winding to a 60-hertz high potential test of 1 .1 5 times the rated line-to-line rms voltage 
for 1 minute. Water must be at ground potential during this test. 

Id. Using 500 volts direct-current, take a 1 minute insulation resistance measurement following the 
procedure as outlined in IEEE Std 43. The minimum insulation resistance in megohms shall be > 
5 times the machine rated kilovolts plus 5. 

e. Remove winding from water, rinse if necessary, dry, and apply other tests as may be required. 

NOTE — The above test is recommended as a test on a representative sample or prototype and should not be 
1 construed as a production test. 

12.63 MACHINE WITH MOISTURE RESISTANT WINDINGS— CONFORMANCE TEST 

An alternating-current squirrel-cage machine with moisture resistant windings shall be capable of passing 
the following test: 

a. After the stator is completed, join all leads together and place it in a chamber with 100 percent 
relative humidity and 40°C temperature for 168 hours, during which time visible condensation 
shall be standing on the winding. 

b. After 168 hours remove the stator winding from the chamber and within 5 minutes using 500 volt 
direct-current take a 1 minute insulation resistance measurement following the procedure as 
outlined in IEEE Std 43. The insulation resistance value shall be not less than 1.5 megohms. 

NOTES 

1— The above test is recommended as a test on a representative sample or prototype and should not be construed as 
a production test. 

2— The sealed winding conformance test in 20.18 shall be permitted to be used in place of this test procedure to 
demonstrate moisture resistance of a prototype. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 2, Page 40 TESTS AND PERFORMANCE— AC MOTORS 



< This page is intentionally left blank. > 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS Part 12, Page 41 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

PART 12 
TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 

12.0 SCOPE 

The standards in this Part 12 of Section II cover direct-current motors built in frames with continuous 
dripproof ratings, or equivalent capacities, up to and including 1 .25 horsepower per rpm, open type. 

12.65 TEST METHODS 

Tests to determine performance characteristics shall be made in accordance with IEEE Std 1 1 3. 

12.66 TEST POWER SUPPLY 

12.66.1 Small Motors 

Performance tests on direct-current small motors intended for use on adjustable-voltage rectifier power 
supplies shall be made with an adjustable power supply, derived from a 60-hertz source, that will provide 
rated voltage and rated form factor at rated load. 

12.66.2 Medium Motors 

See Figure 12-1. 

12.66.2.1 Low-Ripple Power Supplies — Power Supply A 

The rating of direct-current motors intended for use on low-ripple power supplies shall be based on the 
use of one of the following test power supplies: 

a. Direct-current generator 

b. Battery 

c. A polyphase rectifier power supply having more than six pulses per cycle and 1 5 percent or less 
phase control 

d. Any of the power supplies listed in 12.66.2.2 provided sufficient series inductance is used to 
obtain 6 percent, or less, peak-to-peak armature current ripple. 

12.66.2.2 Other Rectifier Power Supplies 

The rating of direct-current motors intended for use on rectifier power supplies other than those described 
in 12.66.2.1 shall be based on the use of a test power supply having the characteristics given in 12.66.2.3 
and defined in 12.66.2.4. 

12.66.2.3 Power Supply Characteristics 
12.66.2.3.1 Input 

a. Single phase or three phase, as specified 

b. Specified frequency. Unless otherwise specified, the frequency shall be 60 hertz 

c. Specified alternating-current voltage, plus 2 percent, minus percent 

d. Power source shall not introduce significant series impedance 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 42 



Section II 
TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 



o 



GENERATOR 
_M Q A L 

MOTOR 









MOTOR 



3-PHASE 

TRANSFORMER 

SECONDARY 



-Kh 



**- 



* 



MOTOR 



H4- 




MOTOR 



H4- 



■Kh 



» 



MOTOR 



POWER SUPPLY A POWER SUPPLY C POWER SUPPLY D POWER SUPPLY E POWER SUPPLY K 

Figure 12-1 
TEST POWER SUPPLIES 
12.66.2.3.2 Output 

a. Rated direct-current motor voltages 

b. Adequate direct current for all required tests 

c. The difference between the highest and lowest peak amplitudes of the current pulses over one 
cycle shall not exceed 2 percent of the highest pulse amplitude 

12.66.2.4 Supplies Designated by a Single Letter 

A test power supply designated by a single letter shall have all of the characteristics listed in 12.66.2.3 
and, in addition, the following. 

12.66.2.4.1 Power Supply C 

Power supply identification letter "C" designates a three-phase full-wave power supply having six total 
pulses per cycle and six controlled pulses per cycle, without free wheeling, with 60-hertz input, with no 
series inductance being added externally to the motor armature circuit inductance. The input line-to-line 
alternating-current voltage to the rectifier shall be 230 volts for motor ratings given in Table 10-9 of 10.62 
and 460 volts for motor ratings given in Table 10-10 of 10.62. 

12.66.2.4.2 Power Supply D 

Power supply identification letter "D" designates a three-phase semibridge having three controlled pulses 
per cycle, with free wheeling, with 60-hertz input, with no series inductance being added externally to the 
motor armature circuit inductance. The input line-to-line alternating-current voltage to the rectifier shall be 
230 volts for motor ratings given in Table 10-9 of 10.62 and 460 volts for motor ratings given in Table 10- 
10 of 10.62. 

12.66.2.4.3 Power Supply E 

Power supply identification letter "E" designates a three-phase single-way power supply having three total 
pulses per cycle and three controlled pulses per cycles, without free wheeling, with 60-hertz input, and 
with no series inductance being added externally to the motor armature circuit inductance. The input line- 
to-line alternating-current voltage to the rectifier shall be 460 volts for motor ratings given in Table 10-10 
of 10.62. 

12.66.2.4.4 Power Supply K 

Power supply identification letter "K" designates a single-phase full-wave power supply having two total 
pulses per cycle and two controlled pulses per cycle, with free wheeling, with 60-hertz input, with no 
series inductance being added externally to the motor armature circuit inductance. The input alternating- 
current voltage to the rectifier shall be 230 volts for motors with armature voltage ratings of 180 volts in 
Table 10-8 and 1 15 volts for motors with armature voltage ratings of 90 volts. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 



MG 1-2009 
Part 12, Page 43 



1 2.67 TEMPERATURE RISE 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of the 
motor, when tested in accordance with the rating at base speed, shall not exceed the values given in the 
following tables. 

12.67.1 Direct-Current Small Motors 

All temperature rises in the following table are based on a maximum ambient temperature of 40°C. 
Temperatures measured by either the thermometer or resistance method shall be determined in 
accordance with IEEE Std. 113. 



All Enclosures 

Class of Insulation System (See 1.65) A B F 

Time Rating (See 10.63) 
Temperature Rise, Degrees C 

a. Armature windings and all windings other than those given in item b - resistance 70 100 130 

b. Shuntfield windings - resistance 70 100 130 

c. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) shall 
not injure the insulation or the machine in any respect. 

NOTES — _____ _____ 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular operation. See 
12.67.4. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. For 
temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 



12.67.2 Continuous-Time-Rated Direct-Current Medium Motors 

All temperature rises in the following table are based on a maximum ambient temperature of 40°C. 
Temperatures shall be determined in accordance with IEEE Std. 113. 



Totally Enclosed Nonventilated 

and Totally Enclosed Fan-Cooled 

Motors, Including Variations 

Thereof 


Motors with all Other Enclosures 


Class of Insulation System (see 1.65) 




A... 


B F.. 


H 


A 


B 


F H 


Time Rating 






Continuous 






Continuous 


Temperature Rise, Degrees C 
a. Armature windings and all windings other 
than those given in items b and c - 
















resistance 


70.. 




..100 130 


....155 


70 


100 


130 155 


b. Multi-layer field windings - resistance 


70. 




...100 130 


155 


70 


100 


130 155 


c. Single-layer field windings with exposed 
uninsulated surfaces and bare copper 
















windings - resistance 


...70... 




.100 130 


...155 


70 


100 


130 155 



d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) shall 
not injure the insulation or the machine in any respect. 



NOTES 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular operation. See 
12.67.4. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. For 
temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 12, Page 44 



Section II 
TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 



1 2.67.3 Short-Time-Rated Direct-Current Medium Motors 

All temperature rises in the following tables are based on a maximum ambient temperature of 40°C. 
Temperatures shall be determined in accordance with IEEE Std. 113. 









Motors Rated 5 


and 15 minutes* 




Totally Enclosed Nonventilated 

and Totally Enclosed Fan-Cooled 

Motors, Including Variations 

Thereof 


Dripproof, Forced-Ventilated,** 
and Other Enclosures 


Class of Insulation System (see 1 .65) 


A 


B 


F 


H 


A 


B 


F H 


Temperature Rise, Degrees C* 
a. Armature windings and all windings other 
than those given in items b and c - 
resistance 


90 


125 


155 


185 


80 


115 


145 175 


b. Multi-layer field windings - resistance 


90 


125 


155 


155 


80 


115 


145 175 


c. Single-layer field windings with exposed 
uninsulated surfaces and bare copper 
windings - resistance 


90 


125 


155 


185 


80 


115 


145 175 



d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) shall 
not injure the insulation or the machine in any respect. 









Motors Rated 30 


and 60 Minutes* 




Totally Enclosed Nonventilated 

and Totally Enclosed Fan-Cooled 

Motors, Including Variations 

Thereof 


Dripproof, Forced-Ventilated,** 
and Other Enclosures 


Class of Insulation System (see 1.65) 


A 


B 


F 


H 


A 


B 


F H 


Temperature Rise, Degrees C* 
a. Armature windings and all windings other 
than those given in items b and c - 
resistance 


80 


110 


140 


165 


70 


100 


130 155 


b. Multi-layer field windings - resistance 


80 


110 


140 


165 


70 


100 


130 155 


c. Single-layer field windings with exposed 
uninsulated surfaces and bare copper 
windings - resistance 


80 


110 


140 


165 


70 


100 


130 155 



d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) shall 
not injure the insulation or the machine in any respect. 
*See 10.63. 

**Forced-ventilated motors are defined in 1.25.6, 1.25.7, and 1.26.4. 
NOTES 

1— Abnormal deterioration of insulation may be expected if the ambient temperature of 40°C is exceeded in regular operation. See 
12.67.4. 

2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. For 
temperature rises for motors intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 



12.67.4 Temperature Rise for Ambients Higher than 40°C 

Temperature rises given in 12.67.1, 12.67.2, and 12.67.3 are based upon a reference ambient 
temperature of 40°C. However, it is recognized that dc machines may be required to operate in an 
ambient temperature higher than 40°C. For successful operation of dc machines in ambient temperatures 
higher than 40°C, the temperature rises of the machines given in 12.67.1, 12.67.2, and 12.67.3 shall be 
reduced by the number of degrees that the ambient temperature exceeds 40°C. When a higher ambient 
temperature than 40°C is required, preferred values of ambient temperatures are 50°C, and 65°C. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS Part 12, Page 45 

12.67.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0°C* 

The temperature rises given in 12.67.1, 12.67.2, and 12.67.3 are based upon a reference ambient 
temperature of 40°C to cover most general environments. However, it is recognized that air-cooled dc 
machines may be operated in environments where the ambient temperature of the cooling air will always 
be less than 40°C. When an air-cooled dc machine is marked with a maximum ambient less than 40°C 
then the allowable temperature rises in 12.67.1, 12.67.2, and 12.67.3 shall be increased according to the 
following: 

a) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.67.1, 12.67.2, and 12.67.3 is less than or equal to 5°C then the 
temperature rises given in 12.67.1, 12.67.2, and 12.67.3 shall be increased by the amount of the 
difference between 40°C and the lower marked ambient temperature. 

b) For machines for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 12.67.1, 12.67.2, and 12.67.3 is greater than 5°C then the 
temperature rises given in 12.67.1, 12.67.2, and 12.67.3 shall be increased by the amount calculated 
from the following expression: 

I Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 

Where: 





Class of Insulation System 






A B F 


H 


Reference Temperature, Degrees C 


120 150 180 


205 



*NIOTE — This requirement does not include water-cooled machines. 

Temperature Rise Limit = maximum allowable temperature rise according to 12.67.1, 12.67.2, and 
12.67.3 

For example: An open medium dc motor with a Class F insulation system is marked for use in an 
ambient with a maximum temperature of 25°C. From the Table above the Reference Temperature is 
180°C and from 12.67.2 the Temperature Rise Limit is 130°C. The allowable Increase in Rise to be 
added to the Temperature Rise Limit is then: 

t • d- L*°r ^o r lL 180°C-(40 O C + 130 Q c) ] 

Increase in Rise =40 C-25 CU<\ i — ,r = 13 <- 

1 ; l[ 80°C Ij 

The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then 
equal to the sum of the Temperature Rise Limit from 12.67.2 and the calculated Increase in Rise. 
For this example that total is 130°C + 13°C = 143°C. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 46 TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 

12.68 VARIATION FROM RATED VOLTAGE 

Motors shall operate successfully, using the power supply selected for the basis of rating, up to and 
including 110 percent of rated direct-current armature and field voltages and, in the case of motors 
operating from a rectifier power supply, with a variation of plus or minus 10 percent of rated alternating- 
current line voltage. 

Performance within this voltage variation will not necessarily be in accordance with the standards 
established for operation at rated voltage. For operation below base speed, see 14.63. 

12.69 VARIATION IN SPEED DUE TO LOAD 

12.69.1 Straight-Shunt-Wound, Stabilized-Shunt-Wound, and Permanent-Magnet Direct-Current 
Motors 

The variation in speed from rated load to no load of a straight-shunt-wound, stabilized-shunt-wound, or 
permanent-magnet direct-current motor having a rating listed in 10.62 shall not exceed the following 
when the motor is operated at rated armature voltage, with the winding at the constant temperature 
attained when operating at base speed rating, and the ambient temperature is within the usual service 
range given in 14.2.1, item a. 



Hp 


Speed Regulation, 

Percent (at Base 

Speed) 


Less than 3 


25 


3-50 


20 


51-100 


15 


101 and larger 


10 



Variation in speed due to loads when operating at speeds higher than base speeds may be greater than 
the values in the above table. 

1 2.69.2 Compound-Wound Direct-Current Motors 

The variation in speed from rated load to no load of a compound-wound direct-current motor having a 
rating listed in 10.62 shall not exceed the values given in the following table for small motors and shall be 
approximately 30 percent of the rated load speed for medium motors when the motor is operated at rated 
voltage, with the windings at the constant temperature attained when operating at its rating, and the 
ambient temperature is within the usual service range given in 14.2.1, item a. 



Hp 


Speed, 
Rpm 


Speed Regulation, 
Percent 


1/20to 1/8 incl. 


1725 


30 


1/20 to 1/8, incl. 


1140 


35 


1/6 to 1/3, incl. 


1725 


25 


1/6 to 1/3, incl. 


1140 


30 


1/2 to 3/4, incl. 


1725 


22 


1/2 


1140 


25 



12.70 VARIATION IN BASE SPEED DUE TO HEATING 

12.70.1 Speed Variation with Temperature 

The variation in base speed of straight-shunt-wound, stabilized-shunt-wound, and permanent magnet 
direct-current motors from that at rated load at ambient temperature to that at rated load at the 
temperature attained at rated load armature and field voltage following a run of the specified duration 
shall not exceed the following percentage of the rated base speed. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 



MG 1-2009 
Part 12, Page 47 



Percentage Variation of Rated Load Base Speed 



Insulation System Class 



Enclosure Type 



B 



Open 

Totally Enclosed 



10 
15 



15 
20 



20 
25 



25 
30 



12.70.2 Resistance Variation with Temperature 

When the temperature of the motor winding changes from ambient temperature to that attained when the 
motor is operating at its rating, the resistance of the motor windings will increase approximately 30 
percent for motors having Class A insulation systems, 40 percent for motors having Class B insulation 
systems, and 50 percent for motors having Class F insulation systems. With a constant voltage power 
supply, this will result in a speed change as large as that given in 12.70.1. Considering all factors, the 
speed of direct-current motors may either decrease or increase as the motor winding temperature 
increases. For small motors, the armature current form factor will also increase slightly with increasing 
motor winding temperature, but only with a single-phase rectifier is this likely to be significant. 

1 2.71 VARIATION FROM RATED SPEED 

The variation above or below the rated full-field speed of a direct-current motor shall not exceed 7-1/2 
percent when operated at rated load and voltage and at full field with the windings at the constant 
temperature attained when operating at its ratings. 

1 2.72 MOMENTARY OVERLOAD CAPACITY 

Direct-current motors shall be capable of carrying successfully for 1 minute an armature current at least 
50 percent greater than the rated armature current at rated voltage. For adjustable-speed motors, this 
capability shall apply for all speeds within the rated speed range when operated from the intended power 
supply. 

12.73 SUCCESSFUL COMMUTATION 

Successful commutation is attained if neither the brushes nor the commutator are burned or injured in the 
conformance test or in normal service to the extent that abnormal maintenance is required. The presence 
of some visible sparking is not necessarily evidence of unsuccessful commutation. 

1 2.74 OVERSPEEDS FOR MOTORS 

12.74.1 Shunt-Wound Motors 

Direct-current shunt-wound motors shall be so constructed that, in an emergency not to exceed 2 
minutes, they will withstand without mechanical injury an overspeed of 25 percent above the highest 
rated speed or 15 percent above the corresponding no-load speed, whichever is greater. 

12.74.2 Compound-Wound Motors Having Speed Regulation of 35 Percent or Less 

Compound-wound motors shall be so constructed that, in an emergency not to exceed 2 minutes, they 
will withstand without mechanical injury an overspeed of 25 percent above the highest rated speed or 15 
percent above the corresponding no-load speed, whichever is greater, but not exceeding 50 percent 
above the highest rated speed. 

12.74.3 Series-Wound Motors and Compound-Wound Motors Having Speed Regulation Greater 
Than 35 Percent 

Since these motors require special consideration depending upon the application for which they are 
intended, the manufacturer shall assign a maximum safe operating speed which shall be stamped on the 
nameplate. These motors shall be so constructed that, in an emergency not to exceed 2 minutes, they 
will withstand without mechanical injury an overspeed which is 10 percent above the maximum safe 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 48 TESTS AND PERFORMANCE—DC SMALL AND MEDIUM MOTORS 

operating speed. The safe operating speed marking is not required on the nameplates of small motors 
which are capable of withstanding a speed which is 10 percent above the no-load speed. 

12.75 FIELD DATA FOR DIRECT-CURRENT MOTORS 
See 12.81. 

12.76 ROUTINE TESTS ON MEDIUM DIRECT-CURRENT MOTORS 

Typical tests which may be made on medium direct-current motors are listed below. All tests should be 
made in accordance with IEEE Std. 113. 

a. No-load readings 1 at rated voltage on all shunt-, stabilized-shunt, compound-wound, and 
permanent magnet motors; quarter-load readings 1 on all series-wound motors. 

b. Full-load readings 1 at base and highest rated speed on all motors having a continuous torque 
rating greater than that of a 1 5-horsepower 1750-rpm motor. Commutation should be observed 
when full-load readings 1 are taken. 

c. High-potential test in accordance with 3.1 and 12.3. 

12.77 REPORT OF TEST FORM FOR DIRECT-CURRENT MACHINES 

For typical test forms, see IEEE Std. 113. 

12.78 EFFICIENCY 

1 2.78.1 Type A Power Supplies 

Efficiency and losses shall be determined in accordance with IEEE Std. 113 using the direct 
measurement method or the segregated losses method. The efficiency shall be determined at rated 
output, voltage, and speed. In the case of adjustable-speed motors, the base speed shall be used unless 
otherwise specified. 

The following losses shall be included in determining the efficiency: 

a. I 2 R loss of armature 

b. I 2 R loss of series windings (including commutating, compounding, and compensating fields, where 
applicable) 

c. I 2 R loss of shunt field 2 

d. Core loss 

e. Stray load loss 

f. Brush contact loss 

g. Brush friction loss 

h. Exciter loss if exciter is supplied with and driven from the shaft of the machine 

i. Ventilating losses 

j. Friction and windage loss 3 



1 The word "readings" includes the following: 

a. Speed in revolutions per minute 

b. Voltage at motor terminals 

c. Amperes in armature 

d. Amperes in shunt field 

2 For separately excited motors, the shunt field l 2 R loss shall be permitted to be omitted from the efficiency calculation if so stated. 

3 In the case of motors furnished with thrust bearings, only that portion of the thrust bearing loss produced by the motor itself shall be 
included in the efficiency calculations. Alternatively, a calculated value of efficiency, including bearing loss due to external thrust 
load, shall be permitted to be specified. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS Part 12, Page 49 



In determining l 2 R losses, the resistance of each winding shall be corrected to a temperature equal to an 
ambient temperature of 25°C plus the observed rated load temperature rise measured by resistance. 
When the rated load temperature rise has not been measured, the resistance of the winding shall be 
corrected to the following temperature: 



Class of Insulation System Temperature, Degrees C 

A 85 

B 110 

F 135 

H 155 

If the temperature rise is specified as that of a lower class of insulation system, the temperature for 
resistance correction shall be that of the lower insulation class. 

1 2.78.2 Other Power Supplies 

It is not possible to make a simulated test which will determine motor efficiency in a particular rectifier 
system. Only by directly measuring input watts (not the product of average volts and average amperes) 
using the power supply to be used in an application can the motor efficiency in that system be accurately 
determined. The extra losses due to the ripple in the current, and especially those due to magnetic 
pulsations, are a function not only of the magnitude of the armature current ripple but, also, of the actual 
wave shape. 

12.79 STABILITY 

When motors are operated in feedback control systems, due attention should be paid to stability 
problems. Any such problems would necessarily have to be solved by the joint efforts of the system 
designer, the motor manufacturer, and the manufacturer of the power supply. 

12.80 OVER TEMPERATURE PROTECTION OF MEDIUM DIRECT-CURRENT MOTORS 

Over-temperature protection of the various windings in a direct-current motor, especially the armature 
winding which rotates, is considerably more complex than the protection of the stator winding of an 
alternating-current motor. The wide range of load and speed (ventilation) in the typical direct-current 
motor application adds to the difficulty. Current-sensing devices located remotely from the motor 
(frequently in control panels) cannot match the thermal characteristics of direct-current motors over a 
wide speed range because of these variable motor cooling conditions. 

In order to improve the degree of over-temperature protection, a temperature sensing protector may be 
installed in a direct-current motor. However, the precision of protection in over-temperature protected 
direct-current motors is less than that possible in alternating-current motors. In over temperature- 
protected direct-current motors, the protector is usually mounted on or near the commutating coil. Since 
this winding carries armature load current, its temperature tends to rise and fall with changes in load in a 
manner similar to the temperature of the armature winding. 

The motor manufacturer should choose the protector and its mounting arrangement to prevent excessive 
temperatures of either the commutating field or the armature winding under most conditions of operation. 
However, under unusual loading conditions, the over-temperature protector may not be able to prevent 



In the case of motors furnished with less than a full set of bearings, friction and windage losses which are representative of the 
actual installation shall be determined by (1) calculation or (2) experience with shop test bearings and shall be included in the 
efficiency calculations. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 50 TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 

the armature winding from reaching excessive temperatures for short periods. Maximum winding 

temperatures at operation of the over-temperature protector may exceed the rated temperature rise. 

Repeated operation of the over-temperature protector indicates a system installation which should be 

investigated. 

If a direct-current motor is specified to be over-temperature protected, the user should inform the motor 

manufacturer whether a normally open or a normally closed contact device is required and the voltage, 

current, and frequency rating of the circuit which this device is intended to open or close. 

1 2.81 DATA FOR DIRECT-CURRENT MOTORS 

The following may be used in supplying data for direct-current motors: 

a. Manufacturer's type 

and frame designation 

b. Requisition or order number 

c. Rated horsepower 

d. Time rating 

e. Enclosure type 

f Insulation system 

g. Maximum ambient temperature 

h. Intended for use on power supply 

i. (Check one) Straight-shunt wound ( ), stabilized-shunt wound ( ), compound 
wound ( ), series wound ( ), or permanent magnet ( ) 

j. Rated voltage 

1. Armature volts, average 

2. Shunt field volts, average 

k. Rated armature current amperes, average 

I. Rated form factor or rms current amperes 

m. Resistance of windings at 25° 

1. Armature ohms 

2. Commutating (and compensating, if used) ohms 

3. Series ohms 

4. Shunt ohms 

n. Field amperes to obtain the following speeds at rated load amperes: 

1. Base speed rpm amperes 

2. 150 percent of base speed, if applicable rpm amperes 

3. Highest rated speed rpm amperes 

o. Saturated inductances 

1. Total armature circuit millihenries 

2. Highest rated speed millihenries 

p. Armature inertia (Wk 2 ) Ib-ft 2 

q. If separately ventilated, minimum cubic feet per minute and static pressure cfm inches of water 

r. Maximum safe operating speed (for all series-wound and compound-wound motors 
having speed regulation greater than 35 percent) 

s. Temperature protection data 



NOTE— For permanent-magnet motors and other motor designs, some of the above listed items may not be applicable. Other data may 
be given. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS Part 12, Page 51 



1 2.82 MACHINE SOUND OF DIRECT-CURRENT MEDIUM MOTORS 

See Part 9 for Sound Power Limits and Measurement Procedures. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 12, Page 52 TESTS AND PERFORMANCE— DC SMALL AND MEDIUM MOTORS 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 13 



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Section II MG 1-2009 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT Part 13, Page 1 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 13 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



13.0 SCOPE 

This standard covers frame assignments for the following classifications of alternating current integral- 
horsepower induction motors: 

Single-phase, Design L, horizontal and vertical motors, open type 

Polyphase, squirrel-cage, Designs A, B, and C, horizontal and vertical motors, open type and totally 

enclosed fan-cooled type. 

13.1 FRAME DESIGNATIONS FOR SINGLE-PHASE DESIGN L, HORIZONTAL, AND VERTICAL 
MOTORS, 60 HERTZ, CLASS B INSULATION SYSTEM, OPEN TYPE, 1.15 SERVICE 
FACTOR, 230 VOLTS AND LESS 

HE 

3/4 

1 
1-1/2 

2 

3 

5 
7-1/2 

NOTE — See 4.4.1 for the dimensions of the frame designations. 





Speed, Rpm 




3600 


1800 


1200 






145T 




143T 


182T 


143T 


145T 


184T 


145T 


182T 




182T 


184T 




184T 


21 3T 




21 3T 


21 5T 





' Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 13, Page 2 



Section II 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



13.2 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, DESIGNS A AND B, 

HORIZONTAL AND VERTICAL MOTORS, 60 HERTZ, CLASS B INSULATION SYSTEM, 
OPEN TYPE, 1.15 SERVICE FACTOR, 575 VOLTS AND LESS* 







Speed, Rprti 






HP 


3600 


1800 


1200 


900 


1/2 








143T 


3/4 






143T 


145T 


1 




1 143T 


145T 


182T 


1-1/2 


143T 


145T 


182T 


184T 


2 


145T 


145T 


184T 


21 3T 


3 


145T 


182T 


21 3T 


21 5T 


5 


182T 


184T 


21 5T 


254T 


7-12 


184T 


213T 


254T 


256T 


10 


21 3T 


21 5T 


256T 


284T 


15 


21 5T 


254T 


284T 


286T 


20 


254T 


256T 


286T 


324T 


25 


256T 


284T 


324T 


326T 


30 


284TS 


286T 


326T 


364T 


40 


286TS 


324T 


364T 


365T 


50 


324TS 


326T 


365T 


404T 


60 


326TS 


364TS** 


404T 


405T 


75 


364TS 


365TS" 


405T 


444T 


100 


365TS 


404TS** 


444T 


445T 


125 


404TS 


405TS** 


445T 


447T 


150 


405TS 


444TS** 


447T 


449T 


200 


444TS 


445TS** 


449T 




250f 


445TS 


447TS** 






300t 


447TS 


449TS** 






350t 


449TS 









* The voltage rating of 115 Volts applies only to motors rated 15 horsepower and smaller. 

** When motors are to be used with V-belt or chain drives, the correct frame size is the frame size shown but with the suffix letter S 

omitted. For the corresponding shaft extension dimensions, see 4.4.1. 
t The 250, 300, and 350 horsepower ratings at the 3600 rpm speed have a 1 .0 service factor. 
NOTE — See 4.4.1 for the dimensions of the frame designations. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



MG 1-2009 
Part 13, Page 3 



13.3 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, DESIGNS A AND B, 
HORIZONTAL AND VERTICAL MOTORS, 60 HERTZ, CLASS B INSULATION SYSTEM, 
TOTALLY ENCLOSED FAN-COOLED TYPE, 1.0 SERVICE FACTOR, 575 VOLTS AND 

LESS* 









Speed, Rpm 




HP 


3600 


1800 


1200 


900 


1/2 








143T 


3/4 






143T 


145T 


1 




143T 


145T 


182T 


1-1/2 


143T 


145T 


182T 


184T 


2 


145T 


145T 


184T 


21 3T 


3 


182T 


182T 


21 3T 


21 5T 


5 


184T 


184T 


21 5T 


254T 


7-12 


213T 


21 3T 


254T 


256T 


10 


21 5T 


21 5T 


256T 


284T 


15 


254T 


254T 


284T 


286T 


20 


256T 


256T 


286T 


324T 


25 


284TS 


284T 


324T 


326T 


30 


286TS 


286T 


326T 


364T 


40 


324TS 


324T 


364T 


365T 


50 


326TS 


326T 


365T 


404T 


60 


364TS 


364TS** 


404T 


405T 


75 


365TS 


365TS" 


405T 


444T 


100 


405TS 


405TS" 


444T 


445T 


125 


444TS 


444TS** 


445T 


447T 


150 


445TS 


445TS" 


447T 


449T 


200 


447TS 


447TS" 


449T 




250 


449TS 


449TS 







* The voltage rating of 1 15 Volts applies only to motors rated 15 horsepower and smaller. 

**When motors are to be used with V-belt or chain drives, the correct frame size is the frame size shown but with the suffix letter S 
omitted. For the corresponding shaft extension dimensions, see 4.4.1 . 

NOTE — See 4.4.1 for the dimensions of the frame designations. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 1 3, Page 4 



Section II 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



13.4 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, DESIGN C, HORIZONTAL 
AND VERTICAL MOTORS, 60 HERTZ, CLASS B INSULATION SYSTEM, OPEN TYPE, 1.15 
SERVICE FACTOR, 575 VOLTS AND LESS* 



HP 



1800 



Speed, Rpm 



1200 



900 



1 
1.5 

2 

3 

5 

7.5 
10 
15 
20 
25 
30 
40 
50 
60 
75 
100 
125 
150 
200 



143T 

145T 

145T 

182T 

184T 

21 3T 

21 5T 

254T 

256T 

284T 

286T 

324T 

326T 

364TS* 

365TS* 

404TS* 

405TS* 

444TS* 

445TS* 



145T 
182T 
184T 
21 3T 
21 5T 
254T 
256T 
284T 
286T 
324T 
326T 
364T 
365T 
404T 
405T 
444T 
445T 
447T 
449T 



182T 
184T 
21 3T 
21 5T 
254T 
256T 
284T 
286T 
324T 
326T 
364T 
365T 
404T 
405T 
444T 
445T 
447T 
449T 



* The voltage rating of 1 1 5 Volts applies only to motors rated 1 5 horsepower and smaller. 

"When motors are to be used with V-belt or chain drives, the correct frame size is the frame size shown but with the suffix letter S 
omitted. For the corresponding shaft extension dimensions, see 4.4.1 . 



NOTE— See 4.4.1 for the dimensions of the frame designations. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



MG 1-2009 
Part 13, Page 5 



13.5 FRAME DESIGNATIONS FOR POLYPHASE, SQUIRREL-CAGE, DESIGN C, HORIZONTAL 
AND VERTICAL MOTORS, 60 HERTZ, CLASS B INSULATION SYSTEM, TOTALLY 
ENCLOSED FAN-COOLED TYPE, 1.0 SERVICE FACTOR, 575 VOLTS AND LESS* 



HP 



1 

1.5 
2 
3 
5 

7.5 

10 

15 

20 

25 

30 

40 

50 

60 

75 

100 

125 

150 

200 



1800 



143T 

145T 

145T 

182T 

184T 

213T 

21 5T 

254T 

256T 

284T 

286T 

324T 

326T 

364TS** 

365TS** 

405TS** 

444TS" 

445TS" 

447TS** 



Speed, Rpm 



1200 



145T 
182T 
184T 
21 3T 
21 5T 
254T 
256T 
284T 
286T 
324T 
326T 
364T 
365T 
404T 
405T 
444T 
445T 
447T 
449T 



900 



182T 
184T 
21 3T 
21 5T 
254T 
256T 
284T 
286T 
324T 
326T 
364T 
365T 
404T 
405T 
444T 
445T 
447T 
449T 



* The voltage rating of 1 1 5 Volts applies only to motors rated 15 horsepower and smaller. 

"When motors are to be used with V-belt or chain drives, the correct frame size is the frame size shown but with the suffix letter S 
omitted. For the corresponding shaft extension dimensions, see 4.4. 1 . 

NOTE— See 4.4.1 for the dimensions of the frame designations. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 3 Page 6 FRAME ASSIGNMENTS FOR ALTERNATING CURRENT 

INTEGRAL HORSEPOWER INDUCTION MOTORS 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 14 



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Section II 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



MG 1-2009 
Part 14, Page 1 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 14 
APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

14.0 SCOPE 

The standards in this Part 14 of Section II cover the following machines: 

a. Alternating-Current Machines— Alternating-current machines up to and including the ratings built 
in frames corresponding to the continuous open-type ratings given in the table below. 



Synchronous 


Motors, 

Squirrel-Cage 

and Wound 

Rotor, Hp 


Motors. Synchronous. Ho 
Power Factor 


Generators, 
Synchronous, 

Revolving 

Field Type kW 

at 0.8 


Speed 


Unity 




0.8 


Power Factor 


3600 


500 


500 




400 


400 


1800 


500 


500 




400 


400 


1200 


350 


350 




300 


300 


900 


250 


250 




200 


200 


720 


200 


200 




150 


150 


600 


150 


150 




125 


125 


514 


125 


125 




100 


100 



14.1 



Direct-Current Machines— Direct-current machines built in frames with continuous dripproof 
ratings, or equivalent capacities, up to and including: 

1 . motors — 1 .25 horsepower per rpm, open type 

2. generators— 1 .0 kilowatt per rpm, open type 

PROPER SELECTION OF APPARATUS 



Machines should be properly selected with respect to their service conditions, usual or unusual, both of 
which involve the environmental conditions to which the machine is subjected and the operating 
conditions. Machines conforming to Parts 10 through 15 of this publication are designed for operation in 
accordance with their ratings under usual service conditions. Some machines may also be capable of 
operating in accordance with their ratings under one or more unusual service conditions. Definite purpose 
or special-purpose machines may be required for some unusual conditions. 

Service conditions, other than those specified as usual, may involve some degree of hazard. The 
additional hazard depends upon the degree of departure from usual operating conditions and the severity 
of the environment to which the machine is exposed. The additional hazard results from such things as 
overheating, mechanical failure, abnormal deterioration of the insulation system, corrosion, fire, and 
explosion. 

Although experience of the user may often be the best guide, the manufacturer of the driven or driving 
equipment or the manufacturer of the machine, or both, should be consulted for further information 
regarding any unusual service conditions which increase the mechanical or thermal duty on the machine 
and, as a result, increase the chances for failure and consequent hazard. This further information should 
be considered by the user, consultants, or others most familiar with the details of the application involved 
when making the final decision. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 2 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



1 4.2 USUAL SERVICE CONDITIONS 

14.2.1 Environmental Conditions 

Machines shall be designed for the following operating site conditions, unless other conditions are 
specified by the purchaser: 

a. Exposure to an ambient temperature in the range of -1 5°C to 40°C or, when water cooling is used, 
an ambient temperature range of 5°C (to prevent freezing of water) to 40°C, except for machines 
rated less than 3/4 hp and all machines other than water cooled having commutator or sleeve 
bearings for which the minimum ambient temperature is 0°C 

b. Exposure to an altitude which does not exceed 3300 feet (1000 meters) 

c. Installation on a rigid mounting surface 

d. Installation in areas or supplementary enclosures which do not seriously interfere with the 
ventilation of the machine 

14.2.2 Operating Conditions 

a. V-belt drive in accordance with 14.42 for alternating-current motors and with 14.67 for industrial 
direct-current motors 

b. Flat-belt, chain, and gear drives in accordance with 14.7 

14.3 UNUSUAL SERVICE CONDITIONS 

The manufacturer should be consulted if any unusual service conditions exist which may affect the 
construction or operation of the motor. Among such conditions are: 

a. Exposure to: 

1 . Combustible, explosive, abrasive, or conducting dusts 

2. Lint or very dirty operating conditions where the accumulation of dirt may interfere with normal 
ventilation 

3. Chemical fumes, flammable or explosive gases 

4. Nuclear radiation 

5. Steam, salt-laden air, or oil vapor 

6. Damp or very dry locations, radiant heat, vermin infestation, or atmospheres conducive to the 
growth of fungus 

7. Abnormal shock, vibration, or mechanical loading from external sources 

8. Abnormal axial or side thrust imposed on the motor shaft 

Ib. Operation where: 
1 . There is excessive departure from rated voltage or frequency, or both (see 12.44 for alternating 
current motors and 12.68 for direct-current motors) 
2. The deviation factor of the alternating-current supply voltage exceeds 10 percent 

!3. The alternating-current supply voltage is unbalanced by more than 1 percent (see 12.45 and 
14.36) 

4. The rectifier output supplying a direct-current motor is unbalanced so that the difference 
between the highest and lowest peak amplitudes of the current pulses over one cycle exceed 10 
percent of the highest pulse amplitude at rated armature current 

5. Low noise levels are required 

6. The power system is not grounded (see 14.31) 

c. Operation at speeds above the highest rated speed 

d. Operation in a poorly ventilated room, in a pit, or in an inclined position 

e. Operation where subjected to: 

1 . Torsional impact loads 

2. Repetitive abnormal overloads 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG ^2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 3 

3. Reversing or electric braking 

4. Frequent starting (see 12.55) 

5. Out-of-phase bus transfer (see 14.45) 

6. Frequent short circuits 

f. Operation of machine at standstill with any winding continuously energized or of short-time-rated 
machine with any winding continuously energized 

g. Operation of direct-current machine where the average armature current is less than 50 percent of 
the rated full-load amperes over a 24-hour period, or continuous operation at armature current 
less than 50 percent of rated current for more than 4 hours 

14.4 TEMPERATURE RISE 

The temperature rises given for machines in 12.43, 12.44, 12.67, and 15.41 are based upon operation at 
altitudes of 3300 feet (1000 meters) or less and a maximum ambient temperature of 40°C. It is also 
recognized as good practice to use machines at altitudes greater than 3300 feet (1000 meters) as 
indicated in the following paragraphs. 

14.4.1 Ambient Temperature at Altitudes for Rated Temperature Rise 

Machines having temperature rises in accordance with 12.43, 12.44, 12.67, and 15.41 will operate 
satisfactorily at altitudes above 3300 feet (1000 meters) in those locations where the decrease in ambient 
temperature compensates for the increase in temperature rise, as follows: 



Maximum Altitude, Feet (Meters) Ambient Temperature, Degrees C 

3300(1000) 40 
6600 (2000) 30 
9900 (3000) 20 

14.4.2 Motors with Service Factor 

Motors having a service factor of 1.15 or higher will operate satisfactorily at unity service factor at an 
ambient temperature of 40°C at altitudes above 3300 feet (1000 meters) up to 9000 feet (2740 meters). 

14.4.3 Temperature Rise at Sea Level 

Machines which are intended for use at altitudes above 3300 feet (1000 meters) at an ambient 
temperature of 40°C should have temperature rises at sea level not exceeding the values calculated from 
the following formula: 

When altitude in feet: 

(Alt -3300)1 



Trsl = Tra 



1 



33000 "J 



When altitude in meters: 

(Alt -1000)] 



T RSL = T RA 



1- 



10000 'J 
Where: 

Trsl = test temperature rise in degrees C at sea level 

Tra = temperature rise in degrees C from the appropriate table in 12.43,12.44, 12.67, 15.41 

Alt = altitude above sea level in feet (meters) at which machine is to be operated 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 4 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



1 4.4.4 Preferred Values of Altitude for Rating Motors 

Preferred values of altitude are 3300 feet (1000 meters), 6600 feet (2000 meters), 9900 feet (3000 
meters), 13200 feet (4000 meters), and 16500 feet (5000 meters). 

14.5 SHORT-TIME RATED ELECTRICAL MACHINES 

Short-time rated electrical machines (see 10.36 and 10.63) should be applied so as to ensure 
performance without damage. They should be operated at rated load for the specified time rating only 
when the motor is at ambient temperature prior to the start of operation. They should not be used (except 
on the recommendation of the manufacturer) on any application where the driven machine may be left 
running continuously. 

1 4.6 DIRECTION OF ROTATION 

Facing the end of the machine opposite the drive end, the standard direction of rotation for all 
nonreversing direct-current motors, ail alternating-current single-phase motors, all synchronous motors, 
and all universal motors shall be counterclockwise. For alternating- and direct-current generators, the 
rotation shall be clockwise. 

This does not apply to polyphase induction motors as most applications on which they are used are of 
such a nature that either or both directions of rotation may be required, and the phase sequence of the 
power lines is rarely known. 

Where two or more machines are mechanically coupled together, the foregoing standard may not apply 
to all units. 

14.7 APPLICATION OF PULLEYS, SHEAVES, SPROCKETS, AND GEARS ON MOTOR SHAFTS 

14.7.1 Mounting 

In general, the closer pulleys, sheaves, sprockets, or gears are mounted to the bearing on the motor 
shaft, the less will be the load on the bearing. This will give greater assurance of trouble-free service. 

The center point of the belt, or system of V-belts, should not be beyond the end of the motor shaft. 

The inner edge of the sheave or pulley rim should not be closer to the bearing than the shoulder on the 
shaft but should be as close to this point as possible. 

The outer edge of a chain sprocket or gear should not extend beyond the end of the motor shaft. 

14.7.2 Minimum Pitch Diameter for Drives Other Than V-Belt 

To obtain the minimum pitch diameters for flat-belt, timing-belt, chain, and gear drives, the multiplier given 
in the following table should be applied to the narrow V-belt sheave pitch diameters in 14.41 for 
alternating-current general-purpose motors or to the V-belt sheave pitch diameters as determined from 
14.67 for industrial direct-current motors: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 5 



Drive Multiplier 



Flat belt* 1.33 

Timing belt** 0.9 

Chain sprocket 0.7 

Spur gear 0.75 

Helical gear 0.85 



*The above multiplier is intended for use with conventional single-ply flat belts. 
When other than single-ply flat belts are used, the use of a larger multiplier is 
recommended. 

**lt is often necessary to install timing belts with a snug fit. However, tension 
should be no more than that necessary to avoid belt slap or tooth jumping. 

14.7.3 Maximum Speed of Drive Components 

The maximum speed of drive components should not exceed the values recommended by the 
component manufacturer or the values specified in the industry standards to which the component 
manufacturer indicates conformance. Speeds above the maximum recommended speed may result in 
damage to the equipment or injury to personnel. 

14.8 THROUGH-BOLT MOUNTING 

Some motor users have found it to their advantage to case the motor drive end shield as an integral part 
of the driven machine and, consequently, they purchase the motors without the drive-end shield. In view 
of the considerable range and variety of stator rabbet diameters, clamp bolt diameters, circle diameters, 
and clamp bolt sizes among motors of differing manufacture, this type of driven machine construction 
may seriously limit users' choice of motors suppliers unless adequate machining flexibility has been 
provided in the design of this end shield. 

In order to assist the machine designer in providing such flexibility, the following data have been compiled 
to give some indication of the range of motor rabbet and clamp bolt circle diameters which may be 
involved. The following table is based on information supplied by member companies of the NEMA Motor 
and Generator Section that build motors in these frame sizes: 



48 Frame, 56 Frame, 

Inches Inches 



Motor Rabbet Diameter: 

Smallest diameter reported 

Largest diameter reported 

Over 75 percent of respondents 

reported diameters within range of 
Motor Clamp Bolt Circle Diameter: 

Smallest diameter reported 

Largest diameter reported 

Over 75 percent of respondents 

reported diameters within range of . 
Motor Clamp Bolt Size: 

Smallest diameter reported 

Largest diameter reported 



5.25 


5.875 


5.625 


6.5 


5.34-5.54 


6.03-6.34 


4.875 


5.5 


5.250 


6.25 


5.00-5.25 


5.65-5.94 


#8 


#10 


#10 


#10 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 6 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



14.9 RODENT PROTECTION 

It is often desirable to provide rodent protection in an open machine in order to retard the entrance of 
small rodents into the machine. Protection may be provided by limiting the size of the openings giving 
direct access to the internal parts of the machine by means of screens, baffles, grills, expanded metal, 
structural parts of the machine, or by other means. The means employed may vary with the size of the 
machine. In such cases, care should be taken to assure adequate ventilation since restricting the air flow 
could cause the machine to exceed its temperature rating. Before applying screens, baffles, expanded 
metal, etc., to a machine for rodent protection, the motor or generator manufacturer should be consulted. 

A common construction restricts the openings giving direct access to the interior of the machine so that a 
0.31 2-in. diameter rod cannot enter the opening. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 7 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 14 
APPLICATION DATA— AC SMALL AND MEDIUM MOTORS 

14.0 SCOPE 

The standards in this Part 14 of Section II cover alternating-current motors up to and including the ratings 
built in frames corresponding to the continuous open-type ratings given in the table below: 



Synchronous 


Motors, 

Squirrel-Cage 

and Wound 


Motors, Synchronous, Ho 
Power Factor 


Speed 


Rotor, Hp 


Unity 




0.8 


3600 


500 


500 




400 


1800 


500 


500 




400 


1200 


350 


350 




300 


900 


250 


250 




200 


720 


200 


200 




150 


600 


150 


150 




125 


514 


125 


125 




100 



14.30 EFFECTS OF VARIATION OF VOLTAGE AND FREQUENCY UPON THE PERFORMANCE 
OF INDUCTION MOTORS 

14.30.1 General 

Induction motors are at times operated on circuits of voltage or frequency other than those for which the 
motors are rated. Under such conditions, the performance of the motor will vary from the rating. The 
following are some of the operating results caused by small variations of voltage and frequency and are 
indicative of the general character of changes produced by such variation in operating conditions. 

14.30.2 Effects of Variation in Voltage on Temperature 

With a 10 percent increase or decrease in voltage from that given on the nameplate, the heating at rated 
horsepower load may increase. Such operation for extended periods of time may accelerate the 
deterioration of the insulation system. 

14.30.3 Effect of Variation in Voltage on Power Factor 

In a motor of normal characteristics at full rated horsepower load, a 10 percent increase of voltage above 
that given on the nameplate would usually result in a decided lowering in power factor. A 10 percent 
decrease of voltage below that given on the nameplate would usually give an increase in power factor. 

14.30.4 Effect of Variation in Voltage on Starting Torques 

The locked-rotor and breakdown torque will be proportional to the square of the voltage applied. 

14.30.5 Effect of Variation in Voltage on Slip 

An increase of 10 percent in voltage will result in a decrease of slip of about 17 percent, while a reduction 
of 10 percent will result in an increase of slip of about 21 percent. Thus, if the slip at rated voltage were 5 
percent, it would be increased to 6.05 percent if the voltage were reduced 10 percent. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 8 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

14.30.6 Effects of Variation in Frequency 

A frequency higher than the rated frequency usually improves the power factor but decreases locked 
rotor torque and increases the speed and friction and windage loss. At a frequency lower than the rated 
frequency, the speed is decreased, locked-rotor torque is increased, and power factor is decreased. For 
certain kinds of motor load, such as in textile mills, close frequency regulation is essential. 

14.30.7 Effect of Variations in Both Voltage and Frequency 

If variations in both voltage and frequency occur simultaneously, the effect will be superimposed. Thus, if 
the voltage is high and the frequency low, the locked-rotor torque will be very greatly increased, but the 
power factor will be decreased and the temperature rise increased with normal load. 

14.30.8 Effect on Special-Purpose or Small Motors 

The foregoing facts apply particularly to general-purpose motors. They may not always be true in 
connection with special-purpose motors, built for a particular purpose, or for very small motors. 

14.31 MACHINES OPERATING ON AN UNGROUNDED SYSTEM 

Alternating-current machines are intended for continuous operation with the neutral at or near ground 
potential. Operation on ungrounded systems with one line at ground potential should be done only for 
infrequent periods of short duration, for example as required for normal fault clearance. If it is intended to 
operate the machine continuously or for prolonged periods in such conditions, a special machine with a 
level of insulation suitable for such operation is required. The motor manufacturer should be consulted 
before selecting a motor for such an application. 

Grounding of the interconnection of the machine neutral points should not be undertaken without 
consulting the System Designer because of the danger of zero-sequence components of currents of all 
frequencies under some operating conditions and the possible mechanical damage to the winding under 
line-to-neutral fault conditions. 

Other auxiliary equipment connected to the motor such as, but not limited to, surge capacitors, power 
factor correction capacitors, or lightning arresters, may not be suitable for use on an ungrounded system 
and should be evaluated independently. 

14.32 OPERATION OF ALTERNATING CURRENT MOTORS FROM VARIABLE-FREQUENCY OR 
VARIABLE-VOLTAGE POWER SUPPLIES, OR BOTH 

14.32.1 Performance 

Alternating-current motors to be operated from solid state or other types of variable-frequency or variable- 
voltage power supplies, or both, for adjustable-speed-drive applications may require individual 
consideration to provide satisfactory performance. Especially for operation below rated speed, it may be 
necessary to reduce the motor torque load below the rated full-load torque to avoid overheating the 
motors. The motor manufacturer should be consulted before selecting a motor for such applications (see 
Parts 30 and 31). 

WARNING: Motors operated from variable frequency or variable voltage power supplies, or both, should not be used in any Division 
1 hazardous (classified) locations unless: 

a. The motor is identified on the nameplate as acceptable for variable speed operation when used in 
Division 1 hazardous (classified) locations. 

b. The actual operating speed range is not outside of the permissible operating speed range marked 
on the motor nameplate. 

c. The actual power supply is consistent with the type of power supply identified in information which 
is supplied by the motor manufacturer 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 9 

For motors to be used in any Division 2 hazardous (classified) locations, the motor manufacturer should 
be consulted. 

High frequency harmonics of inverters can cause an increase in the level of leakage current in the motor. 
Therefore, users are cautioned to follow established grounding practices for the motor frame. 

Failure to comply with this warning could result in an unsafe installation that could cause damage to 
property, serious injury or death to personnel, or both. 

14.32.2 Shaft Voltages 

Additional shaft voltages may occur from voltage and current peaks which are superimposed on the 
symmetrical phase quantities during inverter operation. Experience shows that while this is generally not 
a problem on this class of machines, shaft voltages higher than 500 millivolts (peak), when tested per 
IEEE Std 112, may necessitate grounding the shaft and/or insulating a bearing. 

14.33 EFFECTS OF VOLTAGES OVER 600 VOLTS ON THE PERFORMANCE OF LOW-VOLTAGE 
MOTORS 

Polyphase motors are regularly built for voltage ratings of 575 volts or less (see 10.30) and are expected 
to operate satisfactorily with a voltage variation of plus or minus 10 percent. This means that motors of 
this insulation level may be successfully applied up to an operating voltage of 635 volts. 

Based on motor manufacturers' high-potential tests and performance in the field, it has been found that 
where utilization voltage exceed 635 volts, the safety factor of the insulation has been reduced to a level 
inconsistent with good engineering procedure. 

In view of the foregoing, motors of this insulation level should not be applied to power systems either with 
or without grounded neutral where the utilization voltage exceeds 635 volts, regardless of the motor 
connection employed. 

However, there are some definite-purpose motors that are intended for operation on a grounded 830-volt 
system. Such motors are suitable for460-volt operation when delta connected and for 796-volt operation 
when wye connected when the neutral of the system is solidly grounded. 

14.34 OPERATION OF GENERAL-PURPOSE ALTERNATING-CURRENT POLYPHASE, 2-, 4-, 6-, 
AND 8-POLE, 60-HERTZ MEDIUM INDUCTION MOTORS OPERATED ON 50 HERTZ 

While general-purpose alternating-current polyphase, 2-, 4-, 6-, and 8-pole, 60-hertz medium induction 
motors are not designed to operate at their 60-hertz ratings on 50-hertz circuits, they are capable of being 
operated satisfactorily on 50-hertz circuits if their voltage and horsepower ratings are appropriately 
reduced. When such 60-hertz motors are operated on 50-hertz circuits, the applied voltage at 50 hertz 
should be reduced to 5/6 of the 60-hertz voltage rating of the motor, and the horsepower load at 50 hertz 
should be reduced to 5/6 of the 60-hertz horsepower rating of the motor. 

When a 60-hertz motor is operated on 50 hertz at 5/6 of the 60-hertz voltage and horsepower ratings, the 
other performance characteristics for 50-hertz operation are as follows: 

14.34.1 Speed 

The synchronous speed will be 5/6 of the 60-hertz synchronous speed, and the slip will be 5/6 of the 60- 
hertz slip. 

14.34.2 Torques 

The rated load torque in pound-feet will be approximately the same as the 60-hertz rated load torque in 
pound-feet. The locked-rotor and breakdown torques in pound-feet of 50-hertz motors will be 
approximately the same as the 60-hertz locked-rotor and breakdown torques in pound-feet. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 10 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

14.34.3 Locked-Rotor Current 

The locked-rotor current (amperes) will be approximately 5 percent less than the 60-hertz locked-rotor 
current (amperes). The code letter appearing on the motor nameplate to indicate locked-rotor kVA per 
horsepower applies only to the 60-hertz rating of the motor. 

14.34.4 Service Factor 

The service factor will be 1 .0. 

14.34.5 Temperature Rise 

The temperature rise will not exceed 90°C (see 14.30). 

14.35 OPERATION OF 230-VOLT INDUCTION MOTORS ON 208-VOLT SYSTEMS 

14.35.1 General 

Induction motors intended for operation on 208-volt systems should be rated for 200 volts. 

Operation of a motor rated 230 volts on a 208-volt system is not recommended (except as described in 
14.35.2) because utilization voltages are commonly encountered below the -10 percent tolerance on the 
voltage rating for which the motor is designed. Such operation will generally result in overheating and 
serious reduction in torques. 

14.35.2 Nameplate Marking of Useable @ 200 V 

Motors rated 230 volts, but capable of operating satisfactorily on 208 volt systems shall be permitted to 
be labeled "Usable at 200 Volts." Motors so marked shall be suitable for operation at rated (1.0 service 
factor) horsepower at a utilization voltage of 200 volts at rated frequency, with a temperature rise not 
exceeding the values given in 12.44, item a.2., for the class of insulation system furnished. The service 
factor, horsepower, and corresponding value of current shall be marked on the nameplate; i.e. "Usable @ 
200 V. hp, amps, 1 .0 S.F." 

14.35.3 Effects on Performance of Motor 

When operated on a 208 volt system the motor slip will increase approximately 30% and the motor 
locked-rotor, pull-up and breakdown torque values will be reduced by approximately 20-30%. Therefore, it 
should be determined that the motor will start and accelerate the connected load without injurious 
heating, and that the breakdown torque is adequate for the application. 

NOTE— Utilization voltage tolerance is 200 minus 5% (190 volts) - Ref. ANSI C84.1. "Voltage Range A." Performance within this 
voltage tolerance will not necessarily be in accordance with that stated in 14.35.2. 

14.36 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE OF POLYPHASE 
INDUCTION MOTORS 

When the line voltages applied to a polyphase induction motor are not equal, unbalanced currents in the 
stator windings will result. A small percentage voltage unbalance will result in a much larger percentage 
current unbalance. Consequently, the temperature rise of the motor operating at a particular load and 
percentage voltage unbalance will be greater than for the motor operating under the same conditions with 
balanced voltages. 

Voltages preferably should be evenly balanced as closely as can be read on a voltmeter. Should voltages 
be unbalanced, the rated horsepower of the motor should be multiplied by the factor shown in Figure 14 
to reduce the possibility of damage to the motor. Operation of the motor above a 5-percent voltage 
unbalance condition is not recommended. 

When the derating curve of Figure 14-1 is applied for operation on unbalanced voltages, the selection 
and setting of the overload device should take into account the combination of the derating factor applied 
to the motor and increase in current resulting from the unbalanced voltages. This is a complex problem 
involving the variation in motor current as a function of load and voltage unbalance in addition to the 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 
APPLICATION DATA- 



-AC AND DC SMALL AND MEDIUM MACHINES 



MG 1-2009 
Part 14, Page 11 



characteristics of the overload devices relative to !„ 



or l a 



In the absence of specific information, 



it is recommended that overload devices be selected or adjusted, or both, at the minimum value that does 
not result in tripping for the derating factor and voltage unbalance that applies. When unbalanced 
voltages are anticipated, it is recommended that the overload devices be selected so as to be responsive 
to Imaximum in preference to overload devices responsive to Lerage- 



1.0 




































DERATING FA 
z> o c 
■^ bo cc 





































12 3 4 5 

PERCENT VOLTAGE UNBALANCE 

Figure 14-1 
MEDIUM MOTOR DERATING FACTOR DUE TO UNBALANCED VOLTAGE 



14.36.1 Effect on Performance — General 

The effect of unbalanced voltages on polyphase induction motors is equivalent to the introduction of a 
"negative sequence voltage" having a rotation opposite to that occurring with balanced voltages. This 
negative sequence voltage produces in the air gap a flux rotating against the rotation of the rotor, tending 
to produce high currents. A small negative-sequence voltage may produce in the windings currents 
considerably in excess of those present under balanced voltage conditions. 

14.36.2 Unbalance Defined 

The voltage unbalance in percent may be defined as follows: 



percent voltage unbalance = 1 00 x 



max imum voltage deviation from average voltage 
average voltage 



EXAMPLE: With voltages of 460, 467, and 450, the average is 459, the maximum deviation from average is 9, and the percent 
9 

unbalance = 1 00 x = 1 .96 percent . 

459 

14.36.3 Torques 

The locked-rotor torque and breakdown torque are decreased when the voltage is unbalanced. If the 
voltage unbalance should be extremely severe, the torques might not be adequate for the application. 

14.36.4 Full-Load Speed 

The full-load speed is reduced slightly when the motor operates with unbalanced voltages. 

14.36.5 Currents 

The iocked-rotor current will be unbalanced to the same degree that the voltages are unbalanced, but the 
locked-rotor kVA will increase only slightly. 

The currents at normal operating speed with unbalanced voltages will be greatly unbalanced in the order 
of approximately 6 to 10 times the voltage unbalance. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 12 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



14.37 APPLICATION OF ALTERNATING-CURRENT MOTORS WITH SERVICE FACTORS 

14.37.1 General 

A general-purpose alternating-current motor or any alternating-current motor having a service factor in 
accordance with 12.52 is suitable for continuous operation at rated load under the usual service 
conditions given in 14.2. When the voltage and frequency are maintained at the value specified on the 
nameplate, the motor may be overloaded up to the horsepower obtained by multiplying the rated 
horsepower by the service factor shown on the nameplate. 

When the motor is operated at any service factor greater than 1 , it may have efficiency, power factor, and 
speed different from those at rated load, but the locked-rotor torque and current and breakdown torque 
will remain unchanged. 

A motor operating continuously at any service factor greater than 1 will have a reduced life expectancy 
compared to operating at its rated nameplate horsepower. Insulation life and bearing life are reduced by 
the service factor load. 

14.37.2 Temperature Rise — Medium Alternating-Current Motors 

When operated at the service-factor load, the motor will have a temperature rise as specified in 12.44, 
item a. 2. 

14.37.3 Temperature Rise — Small Alternating-Current Motors 

When operated at the service-factor load, the motor will have a temperature rise as specified in 12.43. 1 . 

14.38 CHARACTERISTICS OF PART-WINDING-START POLYPHASE INDUCTION MOTORS 

The result of energizing a portion of the primary windings of a polyphase induction motor will depend 
upon how this portion is distributed in the motor and, in some cases, may do nothing more than overload 
the portion of the winding so energized (i.e., result in no noticeable reduction of current or torque). For 
this reason, a standard 230/460 volt dual voltage motor may or may not be satisfactory for part-winding 
starting on a 240-volt circuit. 

When the winding is distributed so as to be satisfactory for part-winding starting, a commonly used 
connection results in slightly less than 50 percent of normal locked-rotor torque and approximately 60 
percent of normal locked-rotor current. It is evident that the torque may be insufficient to start the motor if 
it has much friction load. This is not important in applications where it is permissible to draw the full- 
winding starting current from the system in two increments. (If actual values of torque and current are 
important, they should be obtained from the motor manufacturer.) 

When the partial winding is energized, the motor may not accelerate to full speed. On part winding, it can 
at best develop less than half the torque it is capable of on full winding and usually the speed-torque 
characteristic is adversely affected by harmonics resulting from the unbalanced magnetic circuit. Further, 
the permissible accelerating time on part winding may be less than on full winding because of the higher 
current in the portion of the winding energized. However, in the usual application, the remainder of the 
winding is energized a few seconds after the first portion, and the motor then accelerates and runs 
smoothly. During the portion of the accelerating period that the motor is on part winding, it may be 
expected to be noisier than when on full winding. 



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Section II 
APPLICATION DATA- 



-AC AND DC SMALL AND MEDIUM MACHINES 



MG 1-2009 
Part 14, Page 13 



14.39 COUPLING END-PLAY AND ROTOR FLOAT FOR HORIZONTAL 
ALTERNATING-CURRENT MOTORS 

14.39.1 Preferred Ratings for Motors with Ball Bearings 

It is recommended that motors be provided with ball bearings wherever applicable, particularly for the 
ratings indicated in the following table. 



Motor Hp 



Synchronous Speed of Motors, Rpm 



500 and below 
350 and below 
250 and below 
200 and below 



3600,3000, 1800, and 1500 

1200 and 1000 

900 and 750 

720 and below 



14.39.2 Limits for Motors with Sleeve Bearing 

Where motors are provided with sleeve bearings, the motor bearings and limited-end float coupling 
should be applied as indicated in the following table: 



Motor Hp 



Synchronous 

Speed of Motors, 

Rpm 



Min. Motor Rotor 
End Float, Inch 



Max. Coupling 
End Float, Inch 



125 to 250, incl. 
300 to 500, incl. 
125 to 500, incl. 



3600 and 3000 
3600 and 3000 
1800 and below 



0.25 
0.50 
0.25 



0.09 
0.19 
0.09 



14.39.3 Drawing and Shaft Markings 

To facilitate the assembly of driven equipment sleeve bearing motors on frames 440 and larger, the motor 
manufacturer should: 

a. Indicate on the motor outline drawing the minimum motor rotor end-play in inches 

b. Mark rotor end-play limits on motor shaft 

NOTE— The motor and the driven equipment should be assembled and adjusted at the installation site so that there will be 
some endwise clearance in the motor bearing under all operating conditions. The difference between the rotor end-play and the 
end-float in the coupling allows for expansion and contraction in the driven equipment, for clearance in the driven equipment 
thrust bearing, for endwise movement in the coupling, and for assembly. 



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MG 1-2009 Section II 

Part 14, Page 14 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



14.40 OUTPUT SPEEDS FOR MEDIUM GEAR MOTORS OF PARALLEL CONSTRUCTION 

Output Speeds 
(Based on Assumed Operating Speed of 1750 rpm) 

Nominal Gear Output Nominal Gear Output 

Ratios Speeds Ratios Speeds 



1.225 


1430 


25.628 


68 


1.500 


1170 


31.388 


56 


1.837 


950 


38.442 


45 


2.250 


780 


47.082 


37 


2.756 


640 


57.633 


30 


3.375 


520 


70.623 


25 


4.134 


420 


86.495 


20 


5.062 


350 


105.934 


16.5 


6.200 


280 


129.742 


13.5 


7.594 


230 


158.900 


11.0 


9.300 


190 


194.612 


9.0 


11.390 


155 


238.350 


7.5 


13.950 


125 


291.917 


6.0 


17.086 


100 


357.525 


5.0 


20.926 


84 


437.875 


4.0 



These output speeds are based on an assumed operating speed of 1750 rpm and certain nominal gear 
ratios and will be modified: 

a. By the variation in individual motor speeds from the basic operating speed of 1750 rpm 

(The same list of output speeds may be applied to 50-hertz gear motors when employing motors 
of 1500 rpm synchronous speed if an assumed motor operating speed of 1430 rpm is used.) 
(This list of output speeds may be applied to 60-hertz gear motors when employing motors of 
1200 rpm synchronous speed if an assumed motor operating speed of 1 165 rpm is used.) 

b. By a variation in the exact gear ratio from the nominal, which variation will not change the output 
speed by more than plus or minus 3 percent 

14.41 APPLICATION OF MEDIUM ALTERNATING-CURRENT SQUIRREL-CAGE MACHINES 
WITH SEALED WINDINGS 

14.41.1 Usual Service Conditions 

Medium alternating-current squirrel-cage machines with sealed windings are generally suitable for 
exposure to the following environmental conditions: 

a. High humidity 

b. Water spray and condensation 

c. Detergents and mildly corrosive chemicals 

d. Mildly abrasive nonmagnetic air-borne dust in quantities insufficient to impede proper ventilation or 
mechanical operation 

14.41 .2 Unusual Service Conditions 

For environmental conditions other than those listed in 14.41.1, the machine manufacturer should be 
consulted. Such conditions may include the following: 

a. Salt spray 

b. Oils, greases, fats, and solvents 

c. Severely abrasive nonmagnetic dusts 



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Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 15 



d. Vibration 

e. Occasional submergence in water with the motor not running 

1 4.41 .3 Hazardous Locations 

The use of machines with sealed windings in hazardous areas does not obviate the need for other 
constructional features dictated by requirements for the areas involved. 

NOTE— See 12.44, item a. 4, for temperature rating. 

14.42 APPLICATION OF V-BELT SHEAVES TO ALTERNATING CURRENT MOTORS 
HAVING ANTIFRICTION BEARINGS 

14.42.1 Dimensions 

14.42.1 .1 Selected Motor Ratings 

Alternating-current motors having antifriction bearings and a continuous time rating with the frame sizes, 
horsepower, and speed ratings listed in Table 14-1 are designed to operate with V-belt sheaves within 
the limited dimensions listed. Selection of V-belt sheave dimensions is made by the V-belt drive vendor 
and the motor purchaser but, to ensure satisfactory motor operation, the selected diameter shall be not 
smaller than, nor shall the selected width be greater than, the dimensions listed in Table 14-1 . 

14.42.1 .2 Other Motor Ratings 

For motors having speeds and ratings other than those given in Table 14-1, the motor manufacturer 
should be consulted. 

14.42.2 Radial Overhung Load Limitations 

The maximum allowable radial overhung load for horizontal motors with antifriction ball bearings are 
given in Table 14-1A. These limits should not be exceeded. Bearing and shaft failure constitute a safety 
hazard and safeguards suitable to each application should be taken. 

Table 14-1 A shows limits for loads applied at the center of the N-W dimension and a reduction factor for 
loads applied at the end of the shaft. See 14.7 for further information on the mounting of sheaves. 

Applications which result in a thrust or axial load component including vertical motors, are not covered by 
Table 14-1A. The motor manufacturer should be consulted concerning these applications, as well as 
applications which exceed the specified radial overhung load limit or for which a B-10 life other than 
26,280 hours is required. 

14.43 ASEISMATIC CAPABILITY 

See 20.31. 



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MG 1-2009 
Part 14, Page 16 



APPLICATION DATA- 



Section II 
-AC AND DC SMALL AND MEDIUM MACHINES 



Table 14-1 
MEDIUM MOTORS— POLYPHASE INDUCTIONS 

V-belt Sheave* 







Horsepower at 




Conventional 


Narrow 






Synchronous Speed, Rpm 




A, B, C, 


and D ft 


3V, 5V, and 8V*** 












Minimum 




Minimum 












Pitch 


Maximum 


Outside Maximum 


Frame 










Diameter, 


Width 


Diameter, Width, 


Number 


3600 


1800 


1200 


900 


Inches 


Inches* 


Inches Inches 


143T 


1-1/2 


1 


3/4 


1/2 


2.2 




2.2 


145T 


2-3 


1-1/2-2 


1 


3/4 


2.4 




2.4 


182T 


3 


3 


1-1/2 


1 


2.4 




2.4 


182T 


5 








2.6 




2.4 


184T 






2 


1-1/2 


2.4 




2.4 


184T 


5 








2.6 




2.4 


184T 


7-1/2 


5 






3.0 




3.0 


21 3T 


7-1/2-10 


7-1/2 


3 


2 


3.0 




3.0 


21 5T 


10 




5 


3 


3.0 




3.0 


21 5T 


15 


10 






3.8 




3.8 


254T 


15 




7-1/2 


5 


3.8 




3.8 


254T 


20 


15 






4.4 




4.4 


256T 


20-25 




10 


7-1/2 


4.4 




4.4 


256T 




20 






4.6 




4.4 


284T 






15 


10 


4.6 




4.4 


284T 




25 






5.0 




4.4 


286T 




30 


20 


15 


5.4 




5.2 


324T 




40 


25 


20 


6.0 




6.0 


326T 




50 


30 


25 


6.8 




6.8 


364T 






40 


30 


6.8 




6.8 


364T 




60 






7.4 




7.4 


365T 






50 


40 


8.2 




8.2 


365T 




75 






9.0 




8.6 


404T 






60 




9.0 




8.0 


404T 








50 


9.0 




8.4 


404T 




100 






10.0 




8.6 


405T 






75 


60 


10.0 




10.0 


405T 




100 






10.0 




8.6 


405T 




125 






11.5 




10.5 


444T 






100 




11.0 




10.0 


444T 








75 


10.5 




9.5 


444T 




125 






11.0 




9.5 


444T 




150 










10.5 


445T 






125 




12.5 




12.0 


445T 








100 


12.5 




12.0 


445T 




150 










10.5 


445T 




200 










13.2 



*For the maximum speed of the drive components, see 14.7.3. 

fFor the assignment of horsepower and speed ratings to frames, see Part 13. 

**Sheave dimensions are based on the following: 

a. Motor nameplate horsepower and speed 

b. Belt service factor of 1 .6 with belts tightened to belt manufacturers' recommendations 

c. Speed reduction of 5:1 

d. Mounting of sheave on motor shaft in accordance with 14.7 

e. Center-to-center distance between sheaves approximately equal to the diameter of the larger sheave 

f. Calculations based upon standards covered by the tt and *** footnotes, as applicable 

♦ The width of the sheave shall be not greater than that required to transmit the indicated horsepower but in no case shall it be 

wider than 2(N-W) - 0.25. 

*** As covered by Standard Specifications for Drives Using Narrow V-Belts (3V, 5V, and 8V) 1 . 

#The width of the sheave shall be not greater than that required to transmit the indicated horsepower but in no case shall it be wider 

than (N-W). 

ttAs covered by Engineering Standards Specifications for Drives Using Multiple V-Belts (A, B, C, and D Cross Sections) 1 

1 See 1.1, The Rubber Manufacturers Association. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 
APPLICATION DATA- 



-AC AND DC SMALL AND MEDIUM MACHINES 



MG 1-2009 
Part 14, Page 17 



Table 14-1 A 

SHAFT LOADING FOR AC INDUCTION HORIZONTAL MOTORS WITH 

BALL BEARINGS - MAXIMUM RADIAL OVERHUNG LOAD, IN POUNDS, 

AT CENTER OF N-W DIMENSION 

Synchronous Speed 





Frame 
Number 

143T 


3600 1800 1200 

106 154 179 


900 

192 




145T 


109 154 176 


196 




182T 


180 227 260 


287 




184T 


180 227 260 


289 




21 3T 


230 300 350 


380 




21 5T 


230 300 350 


380 




254T 


470 593 703 


774 




256T 


470 589 705 


776 




284T 


570 735 838 


929 




286T 


570 735 838 


929 




324T 


660 860 990 


1100 




326T 


660 850 980 


1090 




364T 


820 1080 1240 


1390 




365T 


820 1080 1240 


1370 




404T 


1270 1450 


1600 




405T 


1290 1480 


1630 




444T 


1560 1760 


1970 




445T 


1520 1760 


1970 




447T 


1450 1660 


1880 




449T 


1490 1660 


1880 


NOTES— 

1 . AH belt loads are considered to act in vertically downward direction. 

2. Overhung loads include belt tension and weight of sheave. 

3. For load at end of the shaft subtract 1 5%. 

4. Radial overhung load limits based on bearing L-10 life of 26,280 hours. 

5. Overhung load limits do not include any effect of unbalanced magnetic pull. 

6. See 14.42 for additional application information 





14.44 POWER FACTOR OF THREE-PHASE, SQUIRREL-CAGE, MEDIUM MOTORS WITH 
CONTINUOUS RATINGS 



14.44.1 Determination of Power Factor from Nameplate Data 

The approximately full-load power factor can be calculated from published or nameplate data as follows: 



PF = 



431 x hp 
E x I x Eff 



Where: 

PF = Per unit power factor at full load 



per unit PF^ 



Percent PF 



100 
hp = Rated horsepower 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 18 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

E = Rated voltage 
I = Rated current 

Eff = Per unit nominal full-load efficiency from published data or as marked on the motor 
nameplate 

., _„ Percent Eff 

per unit Eff = 

100 

14.44.2 Determination of Capacitor Rating for Correcting Power Factor to Desired Value 

For safety reasons, it is generally better to improve power factor for multiple loads as a part of the plant 
distribution system. In those cases where local codes or other circumstances require improving the power 
factor of an individual motor, the KVAR rating of the improvement capacitor may be calculated as follows: 



KVAR= 0.746xHP x 
Eff 



( 



Vm^F Vm^t 



PF PR 



Where: 

KVAR = Rating of three-phase power factor improvement capacitor 

hp = As defined in 14.44.1 

Eff = As defined in 14.44.1 

PF = As defined in 14.44.1 

PFj = Improved per unit power factor for the motor-capacitor combination 

14.44.3 Determination of Corrected Power Factor for Specified Capacitor Rating 

In some cases, it may be desirable to determine the resultant power factor, PFj, where the power factor 
improvement capacitor selected within the maximum safe value specified by the motor manufacturer is 
known. The resultant full-load power factor, PFj, may be calculated from the following: 

PFj 



-(PF) 2 KVAR x Eff 



\ 2 



PF 0.746 x HP 



+ 1 



WARNING: In no case should power factor improvement capacitors be applied in ratings exceeding the 
maximum safe value specified by the motor manufacturer. Excessive improvement may cause 
overexcitation resulting in high transient voltages, currents, and torques that can increase safety hazards 
to personnel and cause possible damage to the motor or to the driven equipment. 

14.44.4 Application of Power Factor Correction Capacitors on Power Systems 

The proper application of power capacitors to a bus with harmonic currents requires an analysis of the 
power system to avoid potential harmonic resonance of the power capacitors in combination with 
transformer and circuit inductance. For power distribution systems which have several motors connected 
to a bus, power capacitors connected to the bus rather than switched with individual motors is 
recommended to minimize the potential combinations of capacitance and inductance, and to simplify the 
application of any tuning filters that may be required. This requires that such bus-connected capacitor 
bands be sized so that proper bus voltage limits are maintained. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



MG 1-2009 
Part 14, Page 19 



14.44.5 Application of Power Factor Correction Capacitors on Motors Operated from Electronic 
Power Supply 

The use of power capacitors for power factor correction on the load side of an electronic power supply 
connected to an induction motor is not recommended. The proper application of such capacitors requires 
an analysis of the motor, electronic power supply, and load characteristics as a function of speed to avoid 
potential overexcitation of the motor, harmonic resonance, and capacitor overvoltage. For such 
applications the drive manufacturer should be consulted. 

14.45 BUS TRANSFER OR RECLOSING 

See 20.34. 



14.46 ROTOR INERTIA FOR DYNAMIC BRAKING 

The rotor inertia (Wk 2 ) in lb-ft 2 for the application of medium ac induction motors with dynamic braking 
equipment may be estimated by the following formula: 



Wk 2 = 



0.02x2 



Poles 1 
~2~1jxHP 



1.35- 0.05 x 



Poles]] 



14.47 EFFECTS OF LOAD ON MOTOR EFFICIENCY 

The efficiency of polyphase induction motors varies from zero at no load to a maximum value near rated 
load and then decreases as load increases further. The efficiency versus load curves in Figure 14-2 
illustrate the typical profile of efficiency variation for various motor ratings from no load to 125% of rated 
load. Actual values of motor efficiencies at various load levels can be obtained by consulting the motor 
manufacturer. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 14, Page 20 



O 

UJ 

o 

LL 
U- 
LU 



APPLICATION DATA- 




Section II 
-AC AND DC SMALL AND MEDIUM MACHINES 



100 HP 



10 HP 
1 HP 



NOTE - THE CURVES INDICATE 
A GENERAL RELATIONSHIP. 
VALUES WILL VARY WITH 
INDIVIDUAL MOTOR TYPE AND 
MANUFACTURER. 



25 50 75 100 

PERCENT RATED LOAD 



125 



Figure 14-2 
TYPICAL EFFICIENCY VERSUS LOAD CURVES FOR 1800-RPM THREE-PHASE 60-HERTZ DESIGN 

B SQUIRREL-CAGE INDUCTION MOTORS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 21 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 14 
APPLICATION DATA— DC SMALL AND MEDIUM MOTORS 



14.0 SCOPE 

The standards in this Part 14 of Section II cover direct-current motors built in frames with continuous 
dripproof ratings, or equivalent capacities, up to and including 1 .25 horsepower per rpm, open-type. 

14.60 OPERATION OF SMALL MOTORS ON RECTIFIED ALTERNATING CURRENT 

14.60.1 General 

When direct-current small motors intended for use on adjustable-voltage electronic power supplies are 
operated from rectified power sources, the pulsating voltage and current wave forms affect motor 
performance characteristics (see 14.61). Because of this, the motors should be designed or specially 
selected to suit this type of operation. 

A motor may be used with any power supply if the combination results in a form factor at rated load equal 
to or less than the motor rated form factor. 

A combination of a power supply and a motor which results in a form factor at rated load greater than the 
motor rated form factor will cause overheating of the motor and will have an adverse effect on 
commutation. 

There are many types of power supplies which can be used; including: 

a. Single-phase, half-wave 

b. Single-phase, half-wave, back rectifier 

c. Single-phase, half-wave, alternating-current voltage controlled 

d. Single-phase, full-wave, firing angle controlled 

e. Single-phase, full-wave, firing angle controlled, back rectifier 

f. Three-phase, half-wave, voltage controlled 

g. Three-phase, half-wave, firing angle controlled 

It is impractical to design a motor or to list a standard motor for each type of power supply. The 
combination of power supply and motor must be considered. The resulting form factor of the combination 
is a measure of the effect of the rectified voltage on the motor current as it influences the motor 
performance characteristics, such as commutation and heating. 

14.60.2 Form Factor 

The form factor of the current is the ratio of the root mean-square value of the current to the average 
value of the current. 

Armature current form factor of a motor-rectifier circuit may be determined by measuring the rms 
armature current (using an electrothermic instrument, 1 electrodynamic instrument, or other true rms 
responding instrument) and the average armature current (using a permanent-magnet moving-coil 
instrument). 1 The armature current form factor will vary with changes in load, speed, and circuit 
adjustment. 



1 These terms are taken from IEEE Std 100. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG1 " 2009 Section II 

Part 14, Page 22 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

Armature current form factor of a motor-rectifier circuit may be determined by calculation. For this 
purpose, the inductance of the motor armature circuit should be known or estimated, including the 
inductance of any components in the power supply which are in series with the motor armature. The 
value of the motor inductance will depend upon the horsepower, speed, and voltage ratings and the 
enclosure of the motor and should be obtained from the motor manufacturer. The method of calculation of 
the armature current form factor should take into account the parameters of the circuit, such as the 
number of phases, the firing angle, half-wave, with or without back rectifier, etc., and whether or not the 
current is continuous or discontinuous. Some methods of calculation are described in 14.62. 

Ranges of armature current form factors on some commonly used motor-rectifier circuits and 
recommended rated form factors of motors associated with these ranges are given in Table 14-2. 

Table 14-2 
RECOMMENDED RATED FORM FACTORS 



Typical Combination of Power source 
and Rectifier Type 


Range of Armature 
Current Form Factors* 


Recommended Rated 
Form Factors of Motors 


Single-phase thyristor (SCR) or 
thyratron with or without back 
rectifiers: 






Half-wave 


1 .86-2 


2 


Half-wave 


1.71-1.85 


1.85 


Half-wave or full-wave 


1.51-1.7 


1.7 


Full-wave 


1.41-1.5 


1.5 


Full-wave 


1.31-1.4 


1.4 


Full-wave 


1.21-1.3 


1.3 


Three-phase thyristor (SCR) or 
Thyratron with or without back 
rectifiers: 






Half-wave 


1.11-1.2 


1.2 


Full-wave 


1.0-1.1 


1.1 



*The armature current form factor may be reduced by filters or other circuit means which will allow 
the use of a motor with a lower rated form factor. 

14.61 OPERATION OF DIRECT-CURRENT MEDIUM MOTORS ON RECTIFIED ALTERNATING 
CURRENT 

When a direct-current medium motor is operated from a rectified alternating-current supply its 
performance may differ materially from that of the same motor when operated from a low-ripple direct- 
current source of supply, such as a generator or a battery. The pulsating voltage and current waveforms 
may increase temperature rise and noise and adversely affect commutation and efficiency. Because of 
these effects, it is necessary that direct-current motors be designed or specially selected to operate on 
the particular type of rectified supply to be used. 

Part 10.60 describes the basis of rating direct-current motors intended for use with rectifier power 
supplies. These ratings are based upon tests of the motors using a test power supply specified in 12 66 
because these power supplies are in common use. It is impractical to design a motor or develop a 
standard for every type of power supply. 

A motor may, under some conditions, be applied to a power supply different from that used for the test 
power supply as the basis of rating. All direct-current motors intended for use on rectifier power supplies 
may be used on low-ripple power supplies such as a direct-current generator or a battery. 

Because the letters used to identify the power supplies in common use have been chosen in alphabetical 
order of increasing magnitude of ripple current, a motor rated on the basis of one of these power supplies 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 23 

may be used on any power supply designated by a lower letter of the alphabet. For example, a motor 
rated on the basis of an "E" power supply may be used on a "C" or "D" power supply. 

If it is desired to use a motor on a power supply designated by a higher letter of the alphabet than the one 
on which it was rated, it may be necessary to add an inductance external to the motor to limit the ripple 
current to the magnitude implied by the motor rating. 

For operation of direct-current motors on power supplies other than those described in 12.65, the 
combination of the power supply and the motor should be considered in consultation with the motor 
manufacturer. 

14.62 ARMATURE CURRENT RIPPLE 

Peak-to-peak armature current ripple is defined as the difference between the maximum value of the 
current waveform and the minimum value. The peak-to-peak armature current ripple may be expressed 
as a percent of the average armature current. The peak-to-peak armature current ripple is best measured 
on an oscilloscope incorporating capability for reading both direct-current and alternating-current values. 
An alternative method is to use a peak-to-peak-reading voltmeter, reading the voltage drop across a non- 
inductive resistance in series with the armature circuit. 

The rms value of the ripple current cannot be derived from peak-to-peak values with any degree of 
accuracy because of variations in current waveform, and the converse relationship of deriving peak-to- 
peak values from rms values is at least equally inaccurate. 

Armature current ripple of a motor-rectifier circuit may be estimated by calculation. For this purpose, the 
inductance of the motor armature circuit must be known or estimated, including the inductance of any 
components in the power supply which are in series with the motor armature. The value of the motor 
inductance will depend upon the horsepower, speed and voltage rating and the enclosure of the motor 
and must be obtained from the motor manufacturer. The method of calculation of the armature current 
ripple should take into account the parameters of the circuit, such as the number of phases, the firing 
angle, half-wave, with or without back rectifier, etc., and whether or not the current is continuous or 
discontinuous. Some methods of calculation are described in the following references: 

"Characteristics of Phase-controtled Bridge Rectifiers with DC Shunt Motor Load" by R.W. Pfaff, AIEE 
Paper 58-40, AIEE Transactions, Vol. 77, Part II, pp. 49-53. 

"The Armature Current Form Factor of a DC Motor Connected to a Controlled Rectifier" by E.F. Kubler, 
AIEE Paper 59-128, AIEE Transactions, Vol. 78, Part IMA, pp. 764-770. 

The armature current ripple may be reduced by filtering or other circuit means. A reduction in the rms 
armature current ripple reduces the heating of a motor, while a reduction in peak-to-peak armature 
current ripple improves the commutating ability of the motor. 

14.63 OPERATION ON A VARIABLE-VOLTAGE POWER SUPPLY 

The temperature rise of motors, when operated at full-load torque and at reduced armature voltage, will 
vary with the construction, with the enclosure, with the percentage of base speed and with the type of 
power supply. All self-ventilated and totally-enclosed motors suffer a loss of heat dissipating ability as the 
speed is reduced below the rated base speed, and this may require that the torque load be reduced to 
avoid overheating of the motor. In addition to this effect, it is characteristic of some rectifier circuits that 
the armature current ripple at rated current increases as the armature voltage is reduced, and this may 
require further load torque reduction. In general, such motors are capable of operation at 67 percent of 
rated torque at 50 percent of base speed without injurious heating. It is impractical to develop a standard 
for motors so operated, but derating data can be obtained from the motor manufacturer to determine if 
the motor will be satisfactory for a particular application. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 14, Page 24 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 

WARNING: Motors operated from variable voltage power supplies, should not be used in any Division 1 
hazardous (classified) locations unless: 

a. The motor is identified on the nameplate as acceptable for variable speed operation when used in 
Division 1 hazardous (classified) locations. 

b. The actual operating speed range is not outside of the permissible operating speed range marked 
on the motor nameplate. 

c. The actual power supply is consistent with the type of power supply identified in information which 
is supplied by the motor manufacturer. 

For motors to be used in any Division 2 hazardous (classified) locations, the motor manufacturer should 
be consulted. 

Failure to comply with this warning could result in an unsafe installation that could cause damage to 
property, serious injury or death to personnel, or both. 

14.64 SHUNT FIELD HEATING AT STANDSTILL 

In some applications of direct-current motors, the user may want to apply voltage to the shunt field 
winding during periods when the motor is stationary and the armature circuit is not energized. The 
percent of rated shunt field voltage and the duration of standstill excitation which a direct-current motor is 
capable of withstanding without excessive temperature will vary depending upon the size, enclosure, 
rating, and type of direct-current motor. 

Some direct-current motors are designed to be capable of continuous excitation of the shunt field at 
standstill with rated field voltage applied. Under this condition, the shunt field temperature may exceed 
rated temperature rise, and prolonged operation under this condition may result in reduced insulation life. 

Other direct-current motors require that the excitation voltage applied be reduced below the rated value if 
prolonged standstill excitation is planned to avoid excessive shunt field temperature. 

The motor manufacturer should be consulted to obtain the heating capability of a particular direct-current 
motor. 

14.65 BEARING CURRENTS 

When a direct-current motor is operated from some unfiltered rectifier power supplies, bearing currents 
may result. Ripple currents, transmitted by capacitive coupling between the rotor winding and the core, 
may flow through the ground path to the transformer secondary. While these currents are small in 
magnitude, they may cause damage to either antifriction or sleeve bearings under certain circumstances. 

14.66 EFFECT OF 50-HERTZ ALTERNATING-CURRENT POWER FREQUENCY 

If a direct-current medium motor is to be applied to a rectifier system having a 50-hertz input frequency 
where the test power supply used as the basis of rating has a 60-hertz input frequency, the magnitude of 
the current ripple may be affected. In general, when other factors are equal, the ripple magnitude will be 
in approximate inverse ratio of the frequencies. A number of methods exist for compensating for the 
increase in ripple: 

a. Add an external inductance equal to 20 percent of the original armature circuit inductance 
(including the motor) to obtain the same magnitude of ripple current as is obtained with the test 
power supply. 

b. Utilize a motor designed for use on a 50-hertz test power supply. 

c. Derate the horsepower rating of the motor. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG -|_2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 25 

d. Select a different power supply such that the current ripple at 50 hertz will not exceed the current 
ripple of the test power supply. 

Data should be obtained from the motor manufacturer to determine if the motor will be satisfactory for a 
particular application. 

14.67 APPLICATION OF OVERHUNG LOADS TO MOTOR SHAFTS 
14.67.1 Limitations 

Figure 14-3 shows minimum design limits for overhung loads for dc motors having shaft extensions 
designated by the frame subscript AT. These limits should not be exceeded. Bearing and shaft failure 
constitute a safety hazard and safeguards suitable to each application should be taken. 

Figure 14-3 shows limits for loads applied at the end of the shaft and at the center of the N-W dimension. 
In general, the closer the load is applied to the motor bearing the less will be the load on the bearing and 
the greater the assurance of trouble-free service. The center of the load should not be beyond the end of 
the shaft. 

In the case of a sheave or pulley, the inner edge should not be closer to the bearing than the shoulder on 
the shaft but should be as close to this point as possible. 

In the case of chain sprocket or gears, the outer edge of the sprocket or gear should not extend beyond 
the end of the motor shaft. 

Shaft loads due to the weight of flywheels or other heavy shaft mounted components are not covered by 
Figure 14-3. Such loads affect system natural frequencies and should only be undertaken after 
consultation with the motor manufacturer. 

Applications which result in a thrust or axial component of load such as helical gears are also not covered 
by Figure 14-3. The motor manufacturer should be consulted concerning these applications. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 14, Page 26 



Section II 
APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



POUNDS 
4.5 



4.0 



3.5 

CO 
UJ 

X 

o 

! 3.0 

uj 



1000 



2000 



3000 



4000 



5000 



UJ 

< 

Q 

Z 

9 
to 

z 

UJ 
UJ 

t 

< 

I 

CO 



2.5 



2.0 



1.5 



1.0 



0.5 

POUNDS 



■■■■■■ " 














D E 














C 
















k__l 
















A 


























A- 


3600 RPM 
















B-2500RPM 

C- 1800/1750 RPM 


























D- 1200/1150 RPM 

E- 900/850 RPM 








T REAu i ur~ ovyftLE 






















It/ 












' I 


1 










^^ 


>^ 




I READ 










>^ 






BOTTOM SCALE/ 


















ABCf 


D E 



























100 



200 



300 



400 



500 



Figure 14-3 
SHAFT LOADING FOR DC MOTORS HAVING "AT" FRAME DESIGNATION- 
RADIAL OVERHUNG LOAD— END OF SHAFT 

NOTES 

1 — F 0r load at center of N-W dimensions add 10%. 

2 — For intermediate speeds interpolate between curves. 

3— ATS shafts are excluded. Consult manufacturer for load capabilities. 

4_See 14.67 for additional application information. 

14.67.2 V-Belt Drives 

The most common application that results in an overhung load on the shaft is a V-belt drive. V-belts are 
friction devices and depend on tension in the belts to prevent slipping. The following equation may be 
used to calculate the shaft load due to belt pull. Should the load exceed the values shown in Figure 14-3 
the load should be reduced by reducing the belt tension, which may cause belt slippage, or by increasing 
the sheave diameter. 



L R = 



2N, 



0.9 



16P* 



Y- 



MV 2 

10 6 



Where: 

L B = Shaft overhung load due to belt tension, lb 

N B = Number of belts 

P A = Force required to deflect one belt 1/64 inch per inch of span, lbs 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES Part 14, Page 27 

Y =2 (f avg ) — where f is a strain constant based on the type and section of belt. Available 

from belt manufacturer 
M = 0.9 m where m is the weight per unit length, lb/in., of the type and section of belt. Available 
from belt manufacturer. 

V = Belt speed, ft/min 

F v = Vector sum correction factor. Corrects tight side and slack side tension vectors for unequal 
driver/driven sheave diameter. Assumes 5:1 tension ratio. Available in belt manufacturer's 
catalogs. 

The above calculation should be made after all parameters are known and P A measured on the actual 
installation. Pre-installation calculations may be made by calculating the belt static tension required by the 
application and the value of P A necessary to attain that tension. 



15 



2.5-G 



DHPxIO 3 ^ 



VN 



>B 



+ - 



MV 



2 



10* 



Where: 

T s = Belt static tension required by the application, lb 

G = Arc of contact correction factor. Available from belt manufacturer 

DHP = Drive horsepower, belt service factor x motor hp 

Having calculated the required belt static tension, the minimum value of P A to attain the required static 
tension is: 



P A (MIN) = 



16 



This value may now be used in the first equation for pre-installation application calculations. In actual 
practice, a value up to 50% greater than P A (MIN) is sometimes used. In this case, the higher value 
should be used in the first equation. 

14.67.3 Applications Other Than V-Belts 

Shaft loads may also occur from applications other than V-belts. Examples are timing belts, sprocket 
chains and gears. Generally these will have little or no static tensioning and shaft overhung load will be a 
function of the transmitted torque. The shaft overhung load may be calculated by making a proper 
geometric analysis taking into account the parameters of the particular drive. Some of these parameters 
might be pitch diameter, tooth pressure angle, amount of pretensioning and anticipated transmitted 
torque. 

14.67.4 Genera! 

The limits established in Figure 14-3 are maximums for acceptable service. For greater assurance of 
trouble-free service, it is recommended that lesser loads be used where possible. Larger pitch diameters 
and moving the load as close to the bearing as possible are helpful factors. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG1 - 2009 Section II 

Part 14, Page 28 APPLICATION DATA— AC AND DC SMALL AND MEDIUM MACHINES 



14.68 RATE OF CHANGE OF ARMATURE CURRENT 

Direct current motors can be expected to operate successfully with repetitive changes in armature current 
such as those which occur during a regular duty cycle provided that, for each change in current, the factor 
K, as defined in the following equation, does not exceed 25. In the equation, the equivalent time for the 
current change to occur is the time which would be required for the change if the current increased or 
decreased at a uniform rate equal to the maximum rate at which it actually increases or decreases 
(neglecting any high-frequency ripple). 

K _ (Change in armature current / rated armature current) 2 
Equivalent time in seconds for current change to occur 

For adjustable-speed motors, this capability applies for all speeds within the rated speed range by 
armature voltage control when operated from the intended power supply. Reduced limits may apply when 
operated in the field control (field weaken) range and the manufacturer should be consulted. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 15 



<This page is intentionally left blank; 



Section II 

DC GENERATORS 



MG 1-2009 
Part 15, Pagel 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 15 
DC GENERATORS 



15.0 SCOPE 

The standards in this Part 15 of Section II cover direct-current generators built in frames with continuous 
dripproof ratings, or equivalent capacities, rated 3/4 kilowatt at 3600 rpm up to and including generators 
having a continuous rating of 1.0 kW per rpm, open type. 

15.10 KILOWATT, SPEED, AND VOLTAGE RATINGS 
15.10.1 Standard Ratings 

The kilowatt, speed, and voltage ratings of industrial direct-current generators and exciters shall be in 
accordance with Table 15-1 . 

Table 15-1 
KILOWATT, SPEED, AND VOLTAGE RATINGS 



Rating 














Rating, 


kW 






Speed, Rpm 








Volts 


3/4 


3450 


1750 


1450 


1150 


850 




125 and 250 


1 


3450 


1750 


1450 


1150 


850 




125 and 250 


1-1/2 


3450 


1750 


1450 


1150 


850 




125 and 250 


2 


3450 


1750 


1450 


1150 


850 




125 and 250 


3 


3450 


1750 


1450 


1150 


850 




125 and 250 


4-1/2 


3450 


1750 


1450 


1150 


850 




125 and 250 


6-1/2 


3450 


1750 


1450 


1150 


850 




125 and 250 


9 


3450 


1750 


1450 


1150 


850 




125 and 250 


13 


3450 


1750 


1450 


1150 


850 




125 and 250 


17 


3450 


1750 


1450 


1150 


850 




125 and 250 


21 


3450 


1750 


1450 


1150 


850 




125 and 250 


25 


3450 


1750 


1450 


1150 


850 




125 and 250 


33 


3450 


1750 


1450 


1150 


850 




125 and 250 


40 


3450 


1750 


1450 


1150 


850 




125 and 250 


50 


3450 


1750 


1450 


1150 


850 




125 and 250 


65 




1750 


1450 


1150 


850 




250 


85 




1750 


1450 


1150 


850 




250 


100 




1750 


1450 


1150 


850 




250 


125 




1750 


1450 


1150 


850 




250 


170 




1750 


1450 


1150 


850 




250 


200 




1750 


1450 


1150 


850 


720 


250 and 500 


240 




1750 


1450 


1150 


850 


720 


250 and 500 


320 






1450 


1150 


850 


720 


250 and 500 


400 








1150 


850 


720 


250 and 500 


480 












720 


500 


560 










850 


720 


500 


640 










850 


720 


500 


720 










850 


720 


500 


800 








1150 


850 




500 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 15, Page 2 DC GENERATORS 



15.10.2 Exciters 

Kilowatt ratings for direct-connected exciters shall be in accordance with 15.10.1. The speed must 
necessarily be that of the machine to which the exciter is coupled. 

15.11 NAMEPLATE TIME RATING, MAXIMUM AMBIENT TEMPERATURE, AND INSULATION 
SYSTEM CLASS 

Industrial direct-current generators shall have a continuous time rating. 

Industrial direct-current generators shall be rated on the basis of a maximum ambient temperature and 
the insulation system class. The rated value of the maximum ambient temperature shall be Class A, B, F, 
or H. All such ratings are based upon a load test with temperature rise values not exceeding those shown 
for the designated class of insulation system in 15.41. Ratings of direct-current generators for any other 
value of maximum ambient temperature shall be based on temperature rise values calculated in 
accordance with 15.41.2. 

15.12 NAMEPLATE MARKING 

The following minimum amount of information shall be given on all nameplates. For abbreviations see 
1.79. For some examples of additional information that may be included on the nameplate see 1 .70.2. 

a. Manufacturer's type designation and frame number 

b. Kilowatt output 

c. Time rating (see 15.11) 

d. Maximum ambient temperature for which the generator is designed (see Note for 15.41.1 
table)i 

e. Insulation system designation (if field and armature use different classes of insulation 
systems, both insulation systems shall be given, that for the field being given first) 1 

f. Rated speed in rpm 

g. Rated load voltage 

h. Rated field voltage when different from rated armature voltage 2 

I. Rated current in amperes 

j. Windings - series, shunt, or compound 

TESTS AND PERFORMANCE 

15.40 TEST METHODS 

Test to determine performance characteristics shall be made in accordance with IEEE Std 1 1 3. 

15.41 TEMPERATURE RISE 

15.41 .1 Temperature Rise for Maximum Ambient of 40°C 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of 
direct-current generators, when tested in accordance with the rating, shall not exceed the values given in 
the following table. All temperature rises are based on a maximum ambient temperature of 40°C. 
Temperatures shall be determined in accordance with IEEE Std. 113. 



1 As an alternative, these items shall be permitted to be replaced by a single item reading "Temperature rise for rated continuous 
load." 

2 As an alternative, this item shall be permitted to be replaced by the following: 

a. Field resistance in ohms at 25°C (optional) 

b. Rated field current in amperes at rated load and speed 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DC GENERATORS Part 1 5, Page 3 





Totally 


Enclosed Nonventilated 










and Totally Enclosed Fan-Cooled 


Generators with all Other 




Generators, Including Variations 




Enclosures 






Thereof 










Class of Insulation System (see 1.65) 


A 


B 


F 


H 


A 


B 


F H 


Time Rating - Continuous 
















Temperature Rise, Degrees C 
















a. Armature windings and all windings other than 
















those given in items b and c - resistance 


70 


100 


130 


155 


70 


100 


130 155 


b. Multi-layer field windings - resistance 


70 


100 


130 


155 


70 


100 


130 155 


c. Single-layer field windings with exposed 
















uninsulated surfaces and bare copper windings - 
















resistance 


70 


100 


130 


155 


70 


100 


130 155 



d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) shall 
not injure the insulation or the machine in any respect. 

NOTES 

1— Abnormal deterioration of insulation may be expected if ambient temperature of 40°C is exceeded in regular operation. 
2— The foregoing values of temperature rise are based upon operation at altitudes of 3300 feet (1000 meters) or less. For 
temperature rises for generators intended for operation at altitudes above 3300 feet (1000 meters), see 14.4. 



15.41.2 Temperature Rise for Ambients Higher than 40°C 

The temperature rises given in 15.41.1 are based upon a reference ambient temperature of 40°C. 
However, it is recognized that dc machines may be required to operate in an ambient temperature higher 
than 40°C. For successful operation of dc machines in ambient temperatures higher than 40°C, the 
temperature rises of the machines given in 15.41.1 shall be reduced by the number of degrees that the 
ambient temperature exceeds 40°C. When a higher ambient temperature than 40°C is required, preferred 
values of ambient temperatures are 50°C, and 65°C. 

15.41.3 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, but Not 
Below 0°C* 

The temperature rises given in 15.41.1 are based upon a reference ambient temperature of 40°C to cover 
most general environments. However, it is recognized that air-cooled dc generators may be operated in 
environments where the ambient temperature of the cooling air will always be less than 40°C. When an 
air-cooled dc generator is marked with a maximum ambient less than 40°C then the allowable 
temperature rises in 15.41 .1 shall be increased according to the following: 

a) For dc generators for which the difference between the Reference Temperature and the sum of 40°C 
and the Temperature Rise Limit given in 15.41.1 is less than or equal to 5°C then the temperature rises 
given in 15.41.1 shall be increased by the amount of the difference between 40°C and the lower marked 
ambient temperature. 

b) For dc generators for which the difference between the Reference Temperature and the sum of 40°C 
and the Temperature Rise Limit given in 15.41.1 is greater than 5°C then the temperature rises given in 
15.41 .1 shall be increased by the amount calculated from the following expression: 

Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 15, Page 4 



Section II 
DC GENERATORS 



Where: 





Class of Insulation System 






A B F 


H 


Reference Temperature, Degrees C 


120 150 180 


205 



*Note: This requirement does not include water-cooled machines. 



Temperature Rise Limit = maximum allowable temperature rise according to 15.41.1 



For example: A dc generator with a Class F insulation system is marked for use in an ambient with a 
maximum temperature of 25°C. From the Table above the Reference Temperature is 180°C and 
from 15.41.1 the Temperature Rise Limit is 130°C. The allowable Increase in Rise to be added to 
the Temperature Rise Limit is then: 



Increase in Rise = }40 C 



:_ 25 «c}< l-i^ 



-(40°C + 1 



30°C 



80° C 




The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then 
equal to the sum of the Temperature Rise Limit from 15.41.1 and the calculated Increase in Rise. 
For this example that total is 1 30°C + 1 3°C = 1 43°C. 

15.42 SUCCESSFUL COMMUTATION 

See 12.73. 

15.43 OVERLOAD 

The generators shall be capable of carrying for 1 minute, with successful commutation as defined in 
12.73, loads of 150 percent of the continuous-rated amperes, with rheostat set for rated-load excitation. 
No temperature limit applies at this overload. 

15.44 VOLTAGE VARIATION DUE TO HEATING 

For flat-compound-wound dripproof direct-current generators rated 50 kilowatts and smaller and 
employing a class B insulation system, the voltage at rated load, with the windings at ambient 
temperature within the usual service range, shall not exceed 112 percent of the voltage at rated load with 
the windings at the constant temperature attained when the generator is operating continuously at its 
rating and with the field rheostat set to obtain rated voltage at rated load. 

15.45 FLAT COMPOUNDING 

Flat-compounded generators shall have windings which will give approximately the same voltage at no 
load as at full load when operated at rated speed at a temperature equivalent to that which would be 
attained after a continuous run at rated load, and the field rheostat set to obtain rated voltage at rated 
load and left unchanged. 

15.46 TEST FOR REGULATION 

Combined regulation shall be measured in accordance with IEEE Std 113. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DC GENERATORS Part 1 5, Page 5 



1 5.47 OVERSPEEDS FOR GENERATORS 

Direct-current generators shall be so constructed that, in an emergency not to exceed 2 minutes, they will 
withstand without mechanical injury an overspeed of 25 percent above rated speed. 

15.48 HIGH-POTENTIAL TEST 

15.48.1 Safety Precautions and Test Procedure 

See 3.1. 

15.48.2 Test Voltage 

The effective value of the high-potential test voltages for direct-current generators shall be: 

a. Generators of 250 watts output or more - 1000 volts plus twice the rated voltage 1 of the 
generator. 

b. Generators of less than 250 watts output having rated voltages not exceeding 250 volts - 1000 
volts. (Generators rated above 250 volts shall be tested in accordance with item a.) 

Exception — Armature or field windings for connections to circuits of 35 volts or less shall be 
tested with 500 volts. 

15.49 ROUTINE TESTS 

Typical tests which may be made on direct-current generators are listed below: 
All tests should be made in accordance with IEEE Std 113. 

a. Full-load readings 2 at rated voltage 

b. No-load readings 2 with rheostat set as in item a 

c. High-potential test in accordance with 15.48 

1 5.50 FIELD DATA FOR DIRECT-CURRENT GENERATORS 

The following field data for direct-current generators may be used in supplying data to control 
manufacturers. 

a. Manufacturer's name 

b. Requisition or order number 

c. Frame designation 

d. Serial number 



. e. 


kW output 


f. 


Shunt or compound-wound 


g 


Rated speed in rpm 


h. 


Rated voltage 


i. 


Rated current 


j- 


Excitation voltage, or self excited 


k. 


Resistance of shunt field at 25°C 



1 Where the voltage rating of a separately excited field of a generator is not stated, it shall be assumed to be 1.5 times the field 
resistance in ohms at 25°C times the rated field current. 

2 The word "readings" includes the following: 

a. Speed in revolutions per minute 

b. Voltage at generator terminals 

c. Amperes in armature 

d. Amperes in shunt field 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 5, Page 6 DC GENERATORS 



I. Recommended value of resistance for rheostat for hand or regulator control 
m. N.L. saturation 



Percent Rated Field Current, 

Armature Voltage Amperes 

Max. field rheostat out — — 



100 
50 



Shunt field current at 
rated voltage and load . 



1 5.51 REPORT OF TEST FORM 

For typical test forms, see IEEE Std 113. 

15.52 EFFICIENCY 

Efficiency and losses shall be determined in accordance with IEEE Std 1 13 using the direct measurement 
method or the segregated losses method. The efficiency shall be determined at rated output, voltage, and 
speed. 

The following losses shall be included in determining the efficiency: 

a. I 2 R loss of armature 

b. I 2 R loss of series windings (including commutating, compounding, and compensating fields, 
where applicable) 

c. I 2 R loss of shunt field 1 

d. Core loss 

e. Stray load loss 

f. Brush contact loss 

g. Brush friction loss 

h. Exciter loss if exciter is supplied with and driven from the shaft of the machine 

I. Ventilating losses 

j. Friction and windage loss 2 

In determining l 2 R losses, the resistance of each winding shall be corrected to a temperature equal to an 
ambient temperature of 25°C plus the observed rated load temperature rise measured by resistance. 
Where the rated load temperature rise has not been measured, the resistance of the winding shall be 
corrected to the following temperature: 



Class of Insulation System Temperature, Degrees C 



1 For separately excited generators, the shunt field l 2 R loss shall be permitted to be omitted from the efficiency calculation if so 
stated. 

2 In the case of generators furnished with thrust bearings, only that portion of the thrust bearing loss produced by the generator itself 
shall be included in the efficiency calculations. Alternatively, a calculated value of efficiency, including bearing loss due to external 
thrust load, shall be permitted to be specified. 

In the case of generators furnished with less than a full set of bearings, friction and windage losses which are representative of the 
actual installation shall be determined by calculation and experience with shop test bearings, and shall be included in the efficiency 
calculations. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DC GENERATORS 



A 
B 
F 

H 





MG 1-2009 




Part 15, Page 7 


85 




110 




135 




155 





If the temperature rise is specified as that of a lower class of insulation system, the temperature for 
resistance correction shall be that of the lower insulation class. 



MANUFACTURING 

1 5.60 Dl RECTION OF ROTATION 

See 14.6. 

15.61 EQUALIZER LEADS OF DIRECT-CURRENT GENERATORS 

Between any two compound-wound generators, the equalizer connection circuit should have a resistance 
not exceeding 20 percent of the resistance of the series field circuit of the smaller generator. However, 
lower values of resistance are desirable. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 15, Page 8 DC GENERATORS 



< This page is intentionally left blank. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18 



<This page is intentionally left blank.> 



Section II 

DEFINITE PURPOSE MACHINES 



MG 1-2009 
Part 18, Page 1 



Section II 
SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MACHINES 

Part 18 
DEFINITE PURPOSE MACHINES 

18.1 SCOPE 

The standards in this Part 18 of Section II cover the following machines: 

a. Alternating-Current Machines— Alternating-current machines up to and including the ratings built 
in frames corresponding to the continuous open-type ratings given in the table. 



Direct-Current Machines— Direct-current motors, generators and motor-generator sets (direct- 
current output) built in frames with continuous dripproof ratings, or equivalent capacities, up to 
and including: 

1. motors: 1.25 horsepower per rpm, open type 

2. generators: 1 .0 kilowatt per rpm, open type 

Motors, Synchronous Hp 



Synchronous 
Rpm 


Speed, 


Motors Squirrel-Cage 
and Wound Rotor, Hp 


3600 




500 


1800 




500 


1200 




350 


900 




250 


720 




200 


600 




150 


514 




125 



Power Factor 
Unity 0.8 


Generators 

Synchronous, 

Revolving Field 

Type, kW at 0.8 

Power Factor 


200 


150 




200 


150 


150 


200 


150 


150 


150 


125 


100 


125 


100 


100 


100 


75 


75 


75 


60 


60 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 2 DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 

(A hermetic motor consists of a stator and rotor without shaft, end shields, or bearings for installation in refrigeration compressors of 
the hermetically sealed type.) 

18.2 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single phase 

1. Split phase 

2. Capacitor start 

3. Two-value capacitor 

4. Permanent-split capacitor 

b. Polyphase induction: Squirrel cage, constant speed 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 3 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



RATINGS 



18.3 VOLTAGE RATINGS 



18.3.1 Single-Phase Motors 

The voltage ratings of single phase motors shall be: 

a. 60 hertz - 1 1 5, 200, and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.3.2 Polyphase Induction Motors 

The voltage ratings for polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.4 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.5 SPEED RATINGS 

Synchronous speed ratings shall be 1800 rpm and 3600 rpm for 60-hertz hermetic motors and 1500 rpm 
and 3000 rpm for 50-hertz hermetic motors. 

TESTS AND PERFORMANCE 

18.6 OPERATING TEMPERATURE 

The operating temperature of a hermetic motor depends on the design of the cooling system as well as 
the motor losses. Therefore, the driven-device manufacturer has control of the operating temperature of 
the hermetic motor, and the motor manufacturer should be consulted on this phase of the application. 

18.7 BREAKDOWN TORQUE AND LOCKED-ROTOR CURRENT OF 60-HERTZ HERMETIC 
MOTORS 

18.7.1 Breakdown Torque 

The breakdown torques of 60-hertz hermetic motors, with rated voltage and frequency applied, shall be in 
accordance with the values given in the following tables which represent the upper limit of the range of 
application for these motors. 

18.7.2 Locked-Rotor Current 

The locked-rotor currents of 60-hertz hermetic motors, with rated voltage and frequency applied and with 
rotor locked, shall not exceed the values given in the following tables: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 4 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



SINGLE-PHASE HERMETIC MOTORS 



1800 


Synchronous 


Rpm 




3600 Synchr 

Breakdown 

Torque, 
Ounce-feet 


onous Rpm 


Breakdown 

Torque, 
Ounce-feet 


Locked-Rotor Current, 
Amperes at 115 Volts 


Locked- 
Rotor 
Current, 
Amperes at 
115 Volts 


10.5 


20 






5.25 


20 


12.5 


20 








6.25 


20 


15 


20 








7.5 


20 


18 


20 








9.0 


20 


21.5 


20 








10.75 


21 


26 


21.5 








13.0 


23 


31 


23 








15.5 


26 


37 


28 




23* 


18.5 


29 


44.5 


34 




23* 


22.0 


33 


53.5 


40 






27.0 


38 


64.5 


48 




46* 


32.0 


43 


77 


57 




46* 


38.5 


49 


92.5 


68 




46* 


46.0 


56 



*Motors having locked-rotor currents within these values usually have lower locked- 
rotor torques than motors with the same breakdown torque ratings and the higher 
locked-rotor current values. 



SINGLE-PHASE HERMETIC MOTORS (Continued) 



1800Synchi 


onous Rpm 
Locked- 
Rotor 
Current, 
Amperes at 
230 Volts 


3600 Synchronous Rpm 


Breakdown 

Torque, 
Pound-feet 


Breakdown 

Torque, 
Pound-feet 


Locked- 
Rotor 
Current, 
Amperes at 
230 Volts 


7 


36 


3.5 


32 


9 


38 


4.5 


39 


11 


44 


5.5 


46 


14 


56 


7.0 


56 


18 


68 


9.0 


69 


23 


85 


11.5 


85 


29 


104 


14.5 


104 


36 


126 


18.0 


126 


45 


155 


22.5 


154 



POLYPHASE SQUIRREL-CAGE INDUCTION HERMETIC MOTORS 



1800 Synchronous Rpm 



3600 Synchronous Rpm 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



MG 1-2009 
Part 18, Page5 



Breakdown 
Torque, Pound- 
feet 



Locked-Rotor 

Current, 

Amperes at 230 

Volts 



Breakdown 
Torque, Pound- 
feet 



Locked-Rotor 

Current, 

Amperes at 230 

Volts 



9 


24 


4.5 


24 


11 


30 


5.5 


30 


14 


38 


7.0 


38 


28 


48 


9.0 


48 


23 


59 


11.5 


59 


29 


71 


14.5 


71 


36 


85 


18.0 


85 


45 


102 


22.5 


102 


56 


125 


28.0 


125 


70 


153 






88 


189 







The temperature of the motor at the start of the test for breakdown torque shall be approximately 25°C. 

Where either single-phase or polyphase motors may be used in the same compressor, it is 
recommended that the polyphase motor used have at least the next larger breakdown torque rating than 
that of the single-phase motor selected. 

1 8.8 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 

18.9 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

See 12.44. 

18.10 DIRECTION OF ROTATION 

The direction of rotation for single-phase hermetic motors shall be counter-clockwise facing the lead end. 

18.11 TERMINAL LEAD MARKINGS 

The terminal lead markings for single-phase hermetic motors shall be as follows: 

a. Start winding - white 

b. Common start and main - white with black tracer 

c. Main winding - white with red tracer 

18.12 METHOD OF TEST FOR CLEANLINESS OF SINGLE-PHASE HERMETIC MOTORS HAVING 
STATOR DIAMETERS OF 6.292 INCHES AND SMALLER 

When a test for cleanliness of a single-phase hermetic motor having a stator outside diameter of 6.292 
inches or smaller is made, the following extraction test procedure shall be used in determining the 
weights of residue: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 6 DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



18.12.1 Stators 

a. Place a sample stator in a cylindrical metal or porcelain enamel container having an inside 
diameter 0.50 to 1.5 inches larger than the outside diameter of the stator. Use a perforated or 
otherwise open spacer to support the stator so that the solvent may circulate freely. 

b. Add sufficient methanol at room temperature (70° to 90°F) to completely cover the stator, 
including windings 

c. Rotate the stator for 1 minutes at 200-240 rpm 

d. Remove the stator, evaporate the liquid in the container to dryness, and heat the residue to 
constant weight at 220° to 230°F. The residue must be essentially free from metal particles. 

18.12.2 Rotors 

a. Place two rotors in a container holding 2 liters of toluol. Bring the solution to boil, and boil for 15 
minutes. 

b. Remove the rotors, evaporate the liquid in the container to dryness, and heat the residue to 
constant weight at 220° to 230°F. The residue shall be essentially free from metal particles. 

18.13 METHOD OF TEST FOR CLEANLINESS OF HERMETIC MOTORS HAVING STATOR 
DIAMETERS OF 8.777 INCHES AND SMALLER 

18.13.1 Purpose 

The purpose of this test is to evaluate the cleanliness of a hermetic stator and rotor by determining the 
amount, for which weights are not specified, of insoluble residue (metallic chips, lint, dust, etc.) and 
soluble residue (winding oil, machining oil, etc.) present as a result of the various manufacturing 
processes. It is not the purpose of this particular procedure to determine the extractables present in an 
insulation system or to determine the suitability of an insulation system to resist the various refrigerants 
and oils present in a hermetic unit. 

18.13.2 Description 

The stator or rotor is vertically agitated in room-temperature Refrigerant 1 13 at a rate of forty to fifty 2.5- 
inch strokes per minute for 30 minutes. The Refrigerant 113 washes out insoluble and soluble residues 
with negligible solvent or chemical action on the insulation or metals present. The insoluble residue is 
separated from the Refrigerant 113 and the Refrigerant 113 is reduced to near dryness by distillation. 
Both the insoluble and the soluble residues are dried for 15 minutes at 125°C and weighed. 

18.13.3 Sample Storage 

The stator or rotor sample shall be placed in a plastic bag which shall be sealed at the site where the 
sample is taken. The sample shall be stored in this container until it is tested. 

18.13.4 Equipment 

a. Stator agitation equipment 

b. Distilling equipment 

c. Hot plate 

d. Oven 

e. Aluminum weighing dishes 

f. Glass beakers 

g. Stainless steel containers 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 7 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



18.13.5 Procedure 

a. Select a stainless steel container with a diameter which is 0.50 to 1 .5 inches larger than the stator 
or rotor diameter and at least 4 inches higher than the total stator or rotor heights. 

b. Position the stator or rotor on a holder so that there will be a 0.50-inch clearance between the 
stator or rotor and the bottom of the container at the bottom of the stroke. With the stator or rotor 
positioned in the container, pour in enough Refrigerant 113 so that there will be a minimum of 1 
inch of liquid above the upper end wire or end ring with the supporting holder at the top of the 
stroke. 

The total residue content of the Refrigerant 113 used in the stator cleanliness test shall be 0.0010 
grams per liter maximum. This shall be determined by transferring 1000 milliliters of Refrigerant 
1 13 to a 4000-miililiter Erlenmeyer flask connected to a distilling condenser. 

Distill over the Refrigerant 113 until a volume of less than 100 milliliters remains in the flask. 
Transfer this portion to a tared aluminum dish which is to be carefully warmed on a hot plate until 
between 0.25 and 0.50 centimeters of liquid remains. Dry the dish and residue for 15 minutes at 
125°C, cool for 15 minutes in a desiccator, and weigh to the nearest 0.001 gram. 

c. Agitate vertically the stator or rotor in Refrigerant 1 1 3 at 25°C plus or minus 5°C at a rate of forty 
to fifty 2.5 inch strokes per minute for 30 minutes. After 30 minutes of agitation, lift the stator or 
rotor above the surface of the Refrigerant 1 1 3 and allow it to drain until the dripping stops. 

d. Transfer the Refrigerant 1 1 3 containing the soluble and insoluble residue (from item c.) to a 4000- 
milliliter Erlenmeyer flask connected to a distilling condenser. Wash the stainless steel container 
with clean Refrigerant 113 several times and add the washings to the flask. Distill over the 
Refrigerant 113 until approximately 200 milliliters remain in the flask. Filter this portion through a 
pre-weighed high-retention filter. Wash the flask with clean Refrigerant 113 several times and filter 
these washings. Remove the filter and dry it for 15 minutes at 125°C, cool for 15 minutes in a 
desiccator, and weigh to the nearest 0.001 gram. The following information shall be reported: 

1. Weight of the residue 

2. Description of the residue 

e. Transfer the filtered Refrigerant 113 to a 250-milliliter glass beaker. Wash the filtering flask 
several times with clean Refrigerant 113 and transfer these washings to the beaker . Carefully 
warm the beaker and the soluble residue until a volume of less than 100 milliliters remains in the 
beaker. Transfer the contents of the beaker to a tared aluminum dish. Carefully warm the 
aluminum dish on a hot plate until between 0.25 and 0.50 centimeters of liquid remains. Dry the 
dish and soluble residue for 15 minutes at 125°C, cool for 15 minutes in a desiccator, and weigh 
to the nearest 0.001 gram. The following information shall be reported: 

1. Weight of residue 

2. Description of residue 

f. The report shall also include the date, stator or rotor type, and the outside diameter and the 
height of the lamination stacking. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 8 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



MANUFACTURING 



18.14 ROTOR BORE DIAMETERS AND KEYWAY DIMENSIONS FOR 60-HERTZ HERMETIC 
MOTORS 1 

The rotor bore diameters and keyway dimensions for 60-hertz hermetic motors shall be: 



CA Dimension 



Tolerance, Inches 



Keyway Dimensions, Inches 



Rotor Bore 






Diameter, Inches 


Plus 


Minus 


0.625 


0.0005 


0.0000 


0.750 


0.0005 


0.0000 


0.875 


0.0005 


0.0000 


1.000 


0.0005 


0.0000 


1.125 


0.0008 


0.0000 


1.250 


0.0008 


0.0000 


1.375 


0.001 


0.000 


1.500 


0.001 


0.000 


1.875 


0.001 


0.000 


2.125 


0.001 


0.000 



Width 


Depth Plus 
Diameter of Bore 


0.1885 


0.9645 


0.1905 


0.9795 


0.1885 


1.0908 


0.1905 


1.1058 


0.251 


1.242 


0.253 


1.257 


0.251 


1.367 


0.253 


1.382 


0.313 


1.519 


0.315 


1.534 


0.376 


1.669 


0.378 


1.684 


0.501 


2.125 


0.503 


2.140 


0.501 


2.375 


0.503 


2.390 



1 For lettering of dimension sheets, see 18.18. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



MG 1-2009 
Part 18, Page 9 



18.15 DIMENSIONS FOR 60-HERTZ HERMETIC MOTORS 1 

To assist the designer of the hermetic compressor, the following parametric dimensions for 60-hertz 
hermetic motors have been compiled; they are based upon information supplied by member companies 
of the NEMA Motor and Generator Section that build hermetic motors. 





Number 


CG (Max) and CH (Max) 
Three-Phase Single-Phase 


BL 




CB 




Stud 




Lead 


Opposite 


Lead 


Opposite 




Diameter 


BH 


of Poles 


End 


Lead End 


End 


Lead End 


(Max) 


DE (Min) 


(Max)* 


Circle 


of Pin 


4.792 


2 






1.25 


1.25 


4.28 


2.50 


1.12 


4.593 


0.175 


5.480 


2 






1.25 


1.22 


4.75 


2.75 


1.31 


5.280 


0.255 


round 






















5.480 


4 






1.19 


1.19 


4.88 


3.38 


1.31 


5.280 


0.199 


round 






















5.480 


2 






1.19 


1.19 


4.69 


2.75 


1.31 


5.280 


0.199 


square 






















5.480 


4 






1.06 


1.06 


4.56 


3.12 


1.38 


5.280 


0.199 


square 






















6.292 


2 


1.62 


1.50 


1.50 


1.38 


5.75 


3.25 


1.62 


5.719 


0.255 


6.292 


4 


1.25 


1.19 


1.38 


1.25 


5.75 


4.06 


1.97 


5.719 


0.255 


7.480 


2 


2.12 


2.00 


2.00 


1.88 


6.75 


3.88 


2.00 


6.969 


0.255 


7.480 


4 


1.88 


1.75 


1.88 


1.75 


6.75 


4.50 


2.25 


6.969 


0.255 


8.777 


2 


2.50 


2.25 


2.25 


2.12 


8.00 


4.69 


2.25 


8.250 


0.255 


8.777 


4 


2.12 


2.00 


2.00 


1.88 


8.00 


5.44 


2.75 


8.250 


0.255 


10.125 


2 


3.00 


3.00 


2.50 


2.25 


9.38 


5.50 


2.50 


9.500 


0.380 


10.125 


4 


2.75 


2.38 


2.75 


2.12 


9.75 


6.38 


3.00 


9.500 


0.380 


12.375** 






















15.562** 























Tolerances for BH Dimensions: 

4.792, 5.480, 6.282, 7.480, - +0.000 inch, -0.002 inch 

8.777, 10.125, 12.375, 15.562 - +0.000 inch, -0.003 inch 

*Applies to punched counterbores. When a sleeve is used, the dimension should be reduced by 0.25 inch. A rotor counterbore will 
weaken the structure of the rotor core and will also tend to adversely affect performance by the removal of active material. It is 
therefore recommended that the counterbore be eliminated where possible and held to a minimum where required. 

**With or without shell 

18.16 FORMING OF END WIRE 

The dimensions of end wires shown in 18.15 are suggested values for preliminary design work. Before 
housing dimensions are finalized, it is recommended that the motor manufacturer be consulted. In any 
particular motor, dimensions larger or smaller than those shown may be the practicable limit with normal 
end-wire forming practice. The forming of end wires should be evaluated carefully as excessive forming 
may tend to damage the stator insulation. 

18.17 THERMAL PROTECTORS ASSEMBLED ON OR IN END WINDINGS OF HERMETIC 
MOTORS 

When thermal protectors are used with hermetic motors, the protectors are usually assembled on or in 
the motor end windings and located so that the best possible heat transfer between the winding and 
protector can be afforded without abusing the insulation on the motor winding or on the protector. Care 
must be exercised in assembly as additional forming of the motor winding for location of the protector 
may weaken or destroy the motor winding insulation. 



1 For lettering of dimension sheets, see 18.18. For rotor bore diameters and keyway dimensions, see 18.14. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 1 DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 

It is usual practice for the thermal protector to be assembled on or in the winding by the motor 
manufacturer, or for the motor manufacturer to provide a formed pocket on or in the end winding for 
insertion of the protector. 

Additional forming of the winding after installation of the protector is to be avoided. This forming may 
weaken the winding insulation, the protective insulation between the protector and the winding, or may 
change the protector calibration. 

As the protector case is often a live current-carrying part, additional insulation between the protector and 
the winding may be necessary in addition to the motor conductor insulation. The motor manufacturer 
should be consulted. 

End winding dimensions given in 18.15 are for motors without provision for thermal protectors; these 
dimensions must be increased when thermal protectors are provided. As thermal protectors of different 
sizes and shapes are available, the motor manufacturer should be consulted for end winding dimensions 
when thermal protectors are used. 



18.18 LETTERING OF DIMENSIONS FOR HERMETIC MOTORS FOR HERMETIC 
COMPRE: 

See Figure 18-1. 



COMPRESSORS 1,2 



1 For the meaning of the letter dimensions, see 4.1 . 

2 The dimensions given in 18.15 apply only when the leads are located as shown by solid lines. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR HERMETIC REFRIGERATION COMPRESSORS 



MG 1-2009 
Part 18, Page 11 




Figure 18-1 
LETTERING OF DIMENSIONS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 12 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 



SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 

(Motors in this classification are designed for propeller fans or centrifugal blowers mounted on the motor shaft, with or without air 
drawn over the motors [not suitable for belted loads].) 

18.19 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single-phase - 1/20 horsepower and larger 

1. Split-phase 

2. Permanent-split capacitor 

3. Shaded-pole 

b. Polyphase induction - 1/8 horsepower and larger; squirrel cage, constant speed 

RATINGS 

18.20 VOLTAGE RATINGS 

18.20.1 Single-Phase Motors 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz- 115 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.20.2 Polyphase Induction Motors 

The voltage ratings of polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.21 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.22 HORSEPOWER AND SPEED RATINGS 

18.22.1 Single-Speed Motors 

See 10.32.1 and 10.32.2. 

18.22.2 Two-Speed Motors 

a. Speed ratings 

1. Split-phase, pole-changing motors 

a) 1800/1200 rpm synchronous speeds, 1725/1 140 rpm approximate full-load speeds 

b) 1200/900 rpm synchronous speeds, 1 140/850 rpm approximate full-load speeds 

c) 1800/900 rpm synchronous speeds, 1725/850 rpm approximate full-load speeds 

2. Non-pole changing, single-voltage permanent-split-capacitor and shaded-pole motors shall be 
designed so that, when loaded by a fan or blower, they will operate at approximately the 
following speeds: 

a) High-speed connection - the full load rpm indicated in 10.32.2 

b) Low-speed connection - 66 percent of synchronous speed 

b. Polyphase pole-changing motors - the speed ratings shall be the same as those listed for single- 
phase motors in item a.1. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 13 

SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 



TESTS AND PERFORMANCE 

18.23 TEMPERATURE RISE 

Motors for shaft-mounted fans and blowers shall have Class A insulation. 1 The temperature rise above 
the temperature of the cooling medium shall be in accordance with 12.43. 2 

18.24 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.25 MAXIMUM LOCKED-ROTOR CURRENT— SINGLE-PHASE 
See 12.33. 

18.26 HIGH-POTENTIAL TESTS 
See 3.1 and 12.3. 

18.27 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
1 See 12.44. 

18.28 DIRECTION OF ROTATION 

The direction of rotation for motors for shaft-mounted fans and blowers shall be counterclockwise facing 
the end opposite the drive end. 

MANUFACTURING 

18.29 GENERAL MECHANICAL FEATURES 

Motors for shaft-mounted fans and blowers shall be constructed with the following mechanical features 
(see dimension diagrams in 18.30): 

a. Totally enclosed or open 

b. Horizontal motors shall have sleeve bearings and shall have provision for taking axial thrust. 
Vertical motors, depending on application, shall be permitted to be provided with either ball or 
sleeve bearings. 

c. End-shield clamp bolts shall have a threaded extension which extends a minimum of 0.38 inch 
beyond the nut. 

d. The shaft extension shall be in accordance with 4.4.1 . 

18.30 DIMENSIONS AND LETTERING OF DIMENSIONS FOR MOTORS FOR SHAFT-MOUNTED 
FANS AND BLOWERS 

See Figures 18-2, 18-3, and 18-4. 

18.31 TERMINAL MARKINGS 

See 18.58. 



1 See 1 .66 for description of Class A insulation. 

2 Where air flow is required over the motor from the driven fan or blower in order not to exceed the values given in 12.43, the motor 
nameplate shall state "air over" and sufficient air shall be provided to meet the required temperature rise limit. The nameplate rating 
is then dependent upon sufficient air flow over the motor in the final application. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 14 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 



18.32 TERMINAL LEAD LENGTHS 

See 18.56. 



!— ■ — N-W 




Figure 18-2 
MOTORS WITH BASE 




THIS DIA. FITS A2.44DIA.- 
CRADLE 



0.4995 450 

(MAX) 




n 



2.50 DIA. 



- 0.140 MIN. 



* When this dimension is greater or less than 4.12 inches, it shall vary in increments of 0.25 inch. 

Figure 18-3 

MOTORS WITHOUT BASE 

(P DIMENSION 438 INCHES AND LARGER) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR SHAFT-MOUNTED FANS AND BLOWERS 



MG 1-2009 
Part 18, Page 15 




THISDIA. FITSA1.75DIA. 
CRADLE 




1.81 DIA. 



k- 0.109 MIN. 



*When this dimension is greater or less than 4.00 inches, it shall vary in increments of 0.25 inch 



P, Inches 



U, Inches 



Over 3.5 
3.5 and smaller 



0.3120-0.3125 
Standard not yet developed 



Figure 18-4 

MOTORS WITHOUT BASE 

(P DIMENSION SMALLER THAN 4.38 INCHES) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 c .. M 

n^* 4o n -10 Section II 

' ^ 6 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR BELTED FANS AND BLOWERS BUILT IN FRAMES 56 AND SMALLER 

SMALL MOTORS FOR BELTED FANS AND BLOWERS BUILT IN FRAMES 56 AND SMALLER 

(Belted fan and blower motors are motors for operating belt-driven fans or blowers such as are commonly used in conjunction with 
hot-air-heating and refrigeration installations and attic ventilators.) uunuiun wim 

18.33 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single- and two-speed 

1. Split phase 

2. Capacitor start 

3. Polyphase 

RATINGS 

18.34 VOLTAGE RATINGS 

18.34.1 Single-Phase Motors 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.34.2 Polyphase Motors 

The voltage ratings of polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.35 FREQUENCIES 

Frequencies shall be 50 and 60 hertz 

1 8.36 HORSEPOWER AND SPEED RATINGS 

18.36.1 Single-Speed Motors 

a. Speed ratings 

1. 60 hertz - 1800 rpm synchronous speed, 1725 rpm approximate full-load speed 

2. 50 hertz - 1500 rpm synchronous speed, 1425 rpm approximate full-load speed 

b. Horsepower ratings 

1. Split-phase- 1/6, 1/4, 1/3, 1/2, and 3/4 horsepower 

2. Capacitor-start- 1/3, 1/2, 3/4, and 1 horsepower 

3. Polyphase- 1/3, 1/2, 3/4, and 1 horsepower 

18.36.2 Two-Speed Motors 

a. Speed Ratings 

1 " ?SrSl" 1800/1200 f P m synchronous speeds, 1725/1140 rpm approximate full-load speeds 

1800/900 rpm synchronous speeds, 1725/850 rpm approximate full-load speeds 
2. 50 hertz - 1500/1000 rpm synchronous speeds, 1425/950 rpm approximate full-load speeds 

b. Horsepower ratings 

1. Split-phase- 1/6, 1/4, 1/3, 1/2, and 3/4 horsepower 

2. Capacitor-start - 1/3, 1/2, 3/4, and 1 horsepower at highest speed 

3. Polyphase - 1/3, 1/2, 3/4, and 1 horsepower at highest speed 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II o*« G d 1 " 20 ?? 

DEFINITE PURPOSE MACHINES Part 18 > Pa 9 e 17 

SMALL MOTORS FOR BELTED FANS AND BLOWERS BUILT IN FRAMES 56 AND SMALLER 



TESTS AND PERFORMANCE 

1 8.37 TEMPERATURE RISE 

Motors for belted fans and blowers shall have either Class A or B insulation. The temperature rise above 
the temperature of the cooling medium shall be in accordance with 12.43. 

1 8.38 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

1 8.39 MAXIMUM LOCKED-ROTOR CURRENT 

See 12.33 for single-phase motors and 12.35 for three-phase motors. 

1 8.40 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.41 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

1 See 12.44. 

1 8.42 DIRECTION OF ROTATION 

Single-phase motors for belted fans and blowers shall be adaptable for either direction of rotation and 
shall be arranged for counter-clockwise rotation when facing the end opposite the drive. 

MANUFACTURING 

18.43 GENERAL MECHANICAL FEATURES 

Motors for belted fans and blowers shall have the following mechanical features (see 18.44): 

a. Open ordripproof 

b. Resilient mounting 

c. Automatic reset thermal overload protector 

d. Mounting dimensions and shaft extensions in accordance with 4.4.1 . 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 18 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR BELTED FANS AND BLOWERS BUILT IN FRAMES 56 AND SMALLER 



18.44 LETTERING OF DIMENSIONS FOR MOTORS FOR BELTED FANS AND BLOWERS 1 

See Figure 18-5. 




Figure 18-5 
LETTERING OF DIMENSIONS 



1 For meaning of letter dimensions, see4.1. for general mechanical features, see 18.43. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 19 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 

18.45 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Shaded pole 

b. Permanent-split capacitor 

RATINGS 

18.46 VOLTAGE RATINGS 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5, 200, 230, and 265 volts 

b. 50 hertz - 1 1 and 220 volts 

18.47 FREQUENCIES 

Frequencies shall be 60 and 50 hertz. 

18.48 HORSEPOWER AND SPEED RATINGS 

18.48.1 Horsepower Ratings 

a. Shaded-pole motors- 1/20, 1/15, 1/12, 1/10, 1/8, 1/6, 1/5, 1/4, and 1/3 horsepower 

b. Permanent-split capacitor motors- 1/20, 1/15, 1/12, 1/10, 1/8, 1/6, 1/5, 1/4, 1/3, and 1/2 
horsepower 

18.48.2 Speed Ratings 





60 Hertz 




50 Hertz 


Synchronous 
Rpm 


Approximate 
Full-Load Rpm 


Synchronous 
Rpm 


Approximate 
Full-Load Rpm 


1800 




1550 


1500 




1300 


1200 




1050 


1000 




875 


900 




800 









TESTS AND PERFORMANCE 



18.49 TEMPERATURE RISE 



Shaded-pole and permanent-split capacitor motors for air conditioning condensers and evaporator fans 
shall have a Class A or B insulation system. 1 The temperature rise above the temperature of the cooling 
medium shall be in accordance with 12.43. 2 



1 8.50 BASIS OF HORSEPOWER RATINGS 

See 10.34, Table 10-6. 



See 1 .66 for description of classes of insulation. 

Where air flow is required over the motor from the driven fan in order not to exceed the values given in 12.43, the motor nameplate 
shall state "air over." 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 20 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 



1 8.51 HIGH-POTENTIAL TESTS 

See 3.1 and 12.3. 

The high-potential test voltage for the compressor motor is frequently higher than that for the fan motor. 
In such cases, the high-potential test voltage applied to the air conditioning unit should be made without 
the fan motor being connected; or, if the fan motor has been connected, the high-potential test voltage 
applied to the air conditioning unit should not exceed 85 percent of the high-potential test voltage for the 
fan motor. 

18.52 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

i See 12.44. 

18.53 VARIATION FROM RATED SPEED 

The variation from specified operating speed for permanent-split capacitor motors shall not exceed plus 
or minus 20 percent of the difference between synchronous speed and the specified speed for operating 
speeds above 65 percent of synchronous speed. 

The variation from specified operating speed for shaded-pole motors shall not exceed plus or minus 20 
percent of the difference between synchronous speed and the specified operating speed for operating 
speeds above 85 percent of synchronous speed and shall not exceed plus or minus 30 percent of the 
difference between synchronous speed and the specified operating speed for operating speeds between 
75 percent and 85 percent of synchronous speed. 

In determining the variation from rated speed, the motor shall be tested with a fan which requires the 
specified torque at the specified operating speed. This variation in specified operating speed shall be 
measured with rated voltage and frequency applied to the motor. The test shall be made after the motor 
windings have attained a temperature of 65°C or the operating temperature, whichever temperature is 
lower. 

If capacitors, speed control, or other auxiliary devices are not provided by the motor manufacturer, 
nominal values of impedance for these devices shall be used during the test. 

At operating speeds below the foregoing percentages of synchronous speeds, greater variations from the 
specified operating speed may be expected. At operating speeds much below the foregoing, starting 
performance, bearing life, and speed variation are very likely to be unsatisfactory to the user. 

18.54 TERMINAL MARKINGS— MULTISPEED SHADED-POLE MOTORS 
See 18.55. 

MANUFACTURING 

18.55 TERMINAL MARKINGS 

See 18-58. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 21 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 



18.56 TERMINAL LEAD LENGTHS 

When shaded-pole and permanent-split capacitor motors are provided with terminal leads, the lead length 
shall be 12 in., including 0.75 in. of bare wire at the end. 1 

Tolerances for leads shall be in accordance with the following. 







Tolerances, 


Inches 






Lengths 


Plus 






Minus 




075 inch stripped length 


0.06 






0.06 




12 to 36 inches, inclusive, lead 


2 











lengths 












Above 36 inches lead length 


3 













18.57 GENERAL MECHANICAL FEATURES 

Shaded-pole and permanent-split capacitor motors shall be constructed with the following mechanical 
features: 

a. Open or totally enclosed 

b. Sleeve or ball bearing 

c. Shaft extension and mounting dimensions in accordance with 18.59 through 18.61 and the 

following. 

1 . Maximum shaft extension length shall be 8.00 in. 

2. Maximum overall length of a shaft with double extensions shall be 20.00 in. 

3. The tolerance for the permissible shaft runout, when measured at the end of the shaft extension 
(See 4.11), shall be 0.002-in. indicator reading on extensions up to 2.00 in. long with a 0.001-in. 
additional allowance for each 1 .00-in. increment of the extension over the 2.00-in. length. 



1 Where longer leads are required, the lead length shall vary in 3-inch increments up to 36 inches and in 6-inch increments for 
lengths over 36 inches. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 Section II 

Part 1 8, Page 24 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 

18.59 DIMENSIONS OF SHADED-POLE AND PERMANENT-SPLIT CAPACITOR MOTORS HAVING 
A P DIMENSION 4.38 INCHES AND LARGER 

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DIMENSIONS 

*When this dimension is greater or less than 4.12 inches, it shall varying increments of 0.25 inch. 
NOTE -The shaft extension length should be in 0.25-inch increments. 

For motors with double shaft extensions the overall length of the shaft should also be in 0.25-inch increments. 
For motors having shaft extensions of 3.00 inches and longer, the recommended maximum usable length of 
flat is 2.50 inches. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 Section II 

Part 18 Page 26 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 



APPLICATION DATA 

1 8.62 NAMEPLATE CURRENT 

The input current of shaded-pole and permanent-split capacitor motors when operating at rated load, or 
rated speed with rated voltage and frequency applied, may be expected to vary plus or minus 10-percent 
from the average value for the particular motor design. Since usual practice is to mark motor nameplates 
with rated currents approximately 5 percent above the average full-load values, some motors may be 
expected to have input currents 5 percent greater than the nameplate value. In those cases where the 
capacitors are not provided by the motor manufacturer, larger tolerances in input current may be 
expected. 

18.63 EFFECT OF VARIATION FROM RATED VOLTAGE UPON OPERATING SPEED 

The effect of variation from rated voltage upon the operating speed of typical designs of shaded-pole and 
permanent-split capacitor motors used for fan drives is shown by speed-torque curves in Figures 18-10 
and 18-11, respectively. In each set of curves the solid curve intersecting the torque axis near 100 
percent of synchronous speed illustrates the speed-torque characteristic of an average motor of a typical 
design. The dashed curves enveloping the solid curve illustrate the variation in speed-torque 
characteristics of the typical motor design when tested at rated voltage and frequency. The dot-dash 
curves illustrate the variation in speed-torque characteristics within plus or minus 10-percent variation in 
line voltage for motors of the typical design when operated at rated frequency. 

In order to illustrate the variation in motor speed when driving a specified fan, a family of typical fan speed 
torque curves are shown, intersecting the typical average motor speed-torque curve at operating speeds 
of 95, 90, 85, 80, 75, and 70 percent of synchronous speed. 

A study of the curves shows that, when the operating speed is too low a percentage of synchronous 
speed, extremely wide variations in operating speed of motors of a particular design may be expected 
within the plus or minus 10-percent variation from rated voltage that may be encountered in service. 
Variation in air flow characteristics of the fan of a particular design are not included. Care should be 
exercised in applying the motor and fan to an air conditioner application, particularly where two- or three- 
speed operation is desired, so that the operating speed is kept within the range where tolerable starting 
characteristics and variations in operating speed may be obtained. Close cooperation among the motor 
manufacturer, fan manufacturer, and air conditioner manufacturer is recommended. 

18.64 INSULATION TESTING 

Motors for air conditioner condenser and evaporator fans are subjected to unusual application conditions 
requiring special care in the testing of insulation systems. 

18.64.1 Test Conditions 

18.64.1.1 Water Present 

One general class of test conditions results in liquid water remaining in the motor or on the windings. This 
tends to produce erratic and non-repeatable results due to variations in actual contact of water drops with 
weak or damaged spots in the insulation system. In testing, the motor must be electrically disconnected 
from all other components of the air conditioning unit and connected to a separate power source. Where 
short-time tests of this type are used, it should be recognized that they may adequately detect weak or 
damaged insulation systems, but they are of doubtful significance in measuring the effect of longtime 
exposure of a particular system to moisture. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 1 8, Page 27 

SMALL MOTORS FOR AIR CONDITIONING CONDENSERS AND EVAPORATOR FANS 



18.64.1.2 High Humidity 

The second general class of test conditions subjects the motor to high humidity without liquid water being 
present. This type of test, when conducted over longer periods of time, is more indicative of the relative 
life expectancy of various motor insulation systems, as they are more uniformly exposed to the 
deteriorating conditions. To be significant, these tests should be conducted at close to 100-percent 
relative humidity and continued as long as practicable. Testing time may be shortened by increasing the 
ambient temperature. 

18.64.2 Test Method 

IEEE Std 117 describes a suitable test method for evaluating insulation systems. Due to environmental 
conditions experienced in certain air conditioner applications, it may be desirable to modify the humidity, 
temperature, contaminants, and vibration specified in IEEE Std 1 17 to suit known application conditions. 

It must be recognized that test conditions and methods of measuring the effects of short-time accelerated 
insulation tests result in only comparative data between different designs or insulation systems. Extended 
life tests in the air conditioner under actual service conditions on at least one motor design are necessary 
to relate test results to actual life. 

When comparing insulation systems by any test, a method of determining the end point of the life of the 
system should be established. The repetitive surge test described in IEEE Std 117 between windings and 
between windings and ground is a suitable test for this purpose. 

Neither a direct-current insulation resistance test or an alternating-current leakage current test give 
dependable comparisons between insulation systems in determining the end point in life under test 
conditions and should not be used for this purpose. The measurements may provide an indication of 
deterioration of a particular insulation system under test or in service, but comparisons of absolute values 
are frequently misleading. Measurement of alternating-current leakage current to ground is a check of 
shock hazard conditions. It is used as such in some testing laboratory specifications. 

18.65 SERVICE CONDITIONS 

Motors for air conditioning condenser and evaporator fans are subjected to environmental conditions 
such as high humidity, high and low ambient temperatures, water from condensation or rain, and salt air. 
Extreme care should be used in the proper application of these motors in order that successful operation 
and good service will result. The following factors should be considered: 

a. The motor should be enclosed or adequately shielded to prevent splashing of condensate or rain 
water into the motor. The wiring to the motor should be arranged to prevent water on the wires 
from draining into the motor enclosure. 

b. The flow of air through the air conditioning unit should be controlled to minimize carrying 
excessive amounts of moisture or rain over and into the motor. 

c. The air conditioning unit should be designed to prevent the possibility of water entering the motor 
lubrication system. 

d. When the ambient temperature of the motor is higher than 40°C for long periods of time, the motor 
should be derated or abnormal deterioration of the insulation may be expected. 

e. When the motor ambient temperature is below 10°C, particular care must be given to the motor 
starting characteristics and bearing lubricant. 

f. Speed stability of air conditioning fan motors may be poor when operating at low speeds. See 
18.53 for variations to be expected in motor speeds. 



• Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 Section II 

Part 18 Page 30 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR SUMP PUMPS 

SMALL MOTORS FOR SUMP PUMPS 

(A sump pump motor is one which furnishes power for operating a pump used for draining basements, pits or sumps.) 

18.66 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Single-phase — Split-phase 

RATINGS 

1 8.67 VOLTAGE RATINGS 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.68 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

1 8.69 HORSEPOWER AND SPEED RATINGS 

18.69.1 Horsepower Ratings 

Horsepower ratings shall be 1/4, 1/3, and 1/2 horsepower. 

18.69.2 Speed Ratings 

Full-load speed ratings shall be: 

a. 60- hertz - 1800 rpm synchronous speed, 1725 rpm approximate full-load speed 

b. 50 hertz - 1500 rpm synchronous speed, 1425 rpm approximate full-load speed 

TESTS AND PERFORMANCE 

18.70 TEMPERATURE RISE 

Sump pump motors shall have either Class A or Class B insulation. 1 The temperature rise above the 
temperature of the cooling medium for each of the various parts of the motor, when tested in accordance 
with the rating, shall not exceed the following values: 

Class of Insulation A B 

Coil Windings, Degrees C 

Single phase 

thermometer 50 70 

resistance 60 80 

The temperature attained by cores and squirrel-cage windings shall not injure the 
i nsulation or the machine in any respect. 

18.71 BASIS OF HORSEPOWER RATINGS 

Ratings of single-phase induction motors shall be in accordance with 10.34. 

18.72 TORQUE CHARACTERISTICS 

For60-hertz motors, the breakdown and locked-rotor torques (see 1.50 and 1.47) shall be not less than 
the following: 



1 See 1 .66 for description of classes of insulation. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG -j_2009 

DEFINITE PURPOSE MACHINES p art 18 Paqe 31 

SMALL MOTORS FOR SUMP PUMPS 



Torque, Oz-ft 



Hp Breakdown Locked Rotor 

"iM 21^5 l7o 

1/3 31.5 20.0 



1/2 40.5 20.0 

The temperature of the motor at the start of the test shall be approximately 25°C. 

18.73 HIGH-POTENTIAL TESTS 

See 3.1 and 12.3. 

18.74 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

I See 12.44. 

1 8.75 DIRECTION OF ROTATION 

The direction of rotation for sump pump motors shall be clockwise facing the end opposite the drive end. 

MANUFACTURING 

18.76 GENERAL MECHANICAL FEATURES 

Sump pump motors shall be constructed with the following mechanical features (see Figure 18-12): 

a. Open construction. Top end bracket to be totally enclosed or to have ventilating openings 
protected by louvers, or the equivalent. 

b. Bearings shall be suitable for vertical operation. 

c. Bottom end bracket to have hub machined for direct mounting on support pipe. 

d. Motors shall be permitted to be equipped with automatic thermal protector. 

e. Motor frame shall have provision for connection of ground lead. 

f. When provided, supply cords shall be three-conductor of at least 1 8 AWG cord. 

18.77 DIMENSIONS FOR SUMP PUMP MOTORS, TYPE K 
See Figure 18-12. 

18.78 FRAME NUMBER AND FRAME SUFFIX LETTER 

When a motor built in a frame given in 4.4.1 is designed in accordance with the standards for sump pump 
motors, the frame number shall be followed by the suffix letter K to indicate such construction. Sump 
pump motors are normally built in 48 or 56 frame sizes. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 32 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR SUMP PUMPS 




ECCENTRICITY OF THESE SURFACES 
WITH INDICATOR MOUNTED STATIONARY 
RELATIVE TO SHAFT MUST NOT EXCEED 0.010 T.I.R. 



All dimensions in inches 



Figure 18-12 
SUMP PUMP MOTOR DIMENSIONS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 33 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 

(A motor of Class I, Group D explosion-proof construction as approved by Underwriters Laboratories Inc. for belt or direct-couple 
drive of gasoline dispensing pumps of the size commonly used in automobile service stations.) 

1 8.79 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single-phase 

1. Capacitor start 

2. Repulsion-start induction 

b. Polyphase: Squirrel-cage, constant speed 

RATINGS 

18.80 VOLTAGE RATINGS 

18.80.1 Single-Phase Motors 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5/230 volts 

b. 50 hertz- 110/220 volts 

18.80.2 Polyphase Induction Motors 

The voltage ratings of polyphase motors shall be: 

a. 60 hertz - 200 and 230 volts 

b. 50 hertz - 220 volts 

18.81 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.82 HORSEPOWER AND SPEED RATINGS 

18.82.1 Horsepower Ratings 

The horsepower ratings shall be 1/3, 1/2, and 3/4 horsepower. 

18.82.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 1800 rpm synchronous speed, 1725 rpm approximate full-load speed 

b. 50 hertz - 1 500 rpm synchronous speed, 1425 rpm approximate full-load speed 

TESTS AND PERFORMANCE 

18.83 TEMPERATURE RISE 

Gasoline dispensing pump motors shall have Class A insulation. They shall be rated 30 minutes or 
continuous, and the temperature rise above the temperature of the cooling medium for each of the 
various parts of the motor, when tested in accordance with the rating, shall not exceed the following 
values: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 34 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 



Coil Windings, Degrees C 

Single-phase and polyphase 

thermometer 55 

resistance 65 

The temperature attained by cores and squirrel-cage windings shall not injure 
the insulation or the machine in any respect. 

NOTE— All temperature rises are based on an ambient temperature of 40°C. 
Abnormal deterioration of insulation may be expected if this ambient 
temperature is exceeded in regular operation. 



NOTE— See 1 .66 for description of classes of insulation. 
18.84 BASIS OF HORSEPOWER RATINGS 

The horsepower ratings of single-phase motors is based upon breakdown torque (see 1.50). For small 
motors for gasoline dispensing pumps, the value of breakdown torque to be expected by the user for any 
horsepower shall fall within the range given in the following table: 



Torque, Oz-ft 







115 Volts 


110 Volts 


Hp 




60 Hertz 


50 Hertz 


1/3 




46.0-53.0 


55.0-64.0 


1/2 




53.0-73.0 


64.0-88.0 


3/4 




73.0-100.0 


88.0-120.0 



The minimum value of breakdown torque obtained in the manufacture of any design will determine the 
rating of the design. Tolerances in manufacturing will result in individual motors having breakdown torque 
from 100 percent to approximately 115 percent of the value on which the rating is based, but this excess 
torque shall not be relied upon by the user in applying the motor to its load. 

The temperature of the motor at the start of the test shall be approximately 25°C. 

18.85 LOCKED-ROTOR TORQUE 

The locked-rotor torques (see 1.47) of single-phase small motors for gasoline dispensing pumps shall be 
not less than those shown in the following table: 



Torque, Oz-ft 




115 Volts 




110 Volts 


Hp 


60 Hertz 




50 Hertz 


1/3 


46.0 




55.0 


1/2 


61.0 




73.0 


3/4 


94.0 




101.0 



The temperature of the motor at the start of the test shall be approximately 25°C. 

18.86 LOCKED-ROTOR CURRENT 

See 12.33 for Design N motors. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 35 

SMALL MOTORS FOR GASOLINE DISPENSING PUMPS 



1 8.87 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 

18.88 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

See 12.44. 

1 8.89 DIRECTION OF ROTATION 

The direction of rotation shall be clockwise facing the end opposite the drive end. 

MANUFACTURING 

18.90 GENERAL MECHANICAL FEATURES 

Gasoline dispensing pump motors shall be constructed with the following mechanical features: 
(see 18.92) 

a. Totally enclosed, explosion proof, Class I, Group D 

b. Rigid base mounting 

c. Built-in line switch and operating lever (optional) 

d. A motor that may exceed its maximum safe temperature under any operating condition (including 
locked rotor and single phasing) shall be provided with a temperature-limiting device within the 
motor enclosure. The temperature-limiting device shall not open under full-load conditions within 
its time rating and shall prevent dangerous temperatures from occurring on the exterior surface of 
the rotor enclosure with respect to ignition of the explosion atmosphere involved. The maximum 
safe temperature is 280°C (536°F) for Class I, Group D. The temperature limiting device shall 
open the motor circuit directly. 

e. Voltage selector switch built in on the same end as the swivel connector on single-phase motors 

f. Line leads 36 inches long brought out through the swivel connector 

g. Swivel connector and line switch shall be permitted to be furnished in locations 90 and 180 
degrees from that shown in 18.92 

18.91 FRAME NUMBER AND FRAME SUFFIX LETTER 

When a motor having the dimensions given in 18.92 is designated in accordance with the standards for 
gasoline dispensing pump motors, the frame number shall be followed by the letter G. See Figure 18-13. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 37 

SMALL MOTORS FOR OIL BURNERS 

SMALL MOTORS FOR OIL BURNERS 

(A motor for operating mechanical-draft oil burners for domestic installations.) 

1 8.93 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Single-phase - Split-phase 

RATINGS 

18.94 VOLTAGE RATINGS 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.95 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.96 HORSEPOWER AND SPEED RATINGS 

18.96.1 Horsepower Ratings 

The horsepower ratings shall be 1/12, 1/8, and 1/6 horsepower. 

18.96.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 1800 and 3600 rpm synchronous speed, 1725 and 3450 rpm approximate full-load 
speed 

b. 50 hertz - 1500 and 3000 rpm synchronous speed, 1425 and 2850 rpm approximate full-load speed 

TESTS AND PERFORMANCE 

1 8.97 TEMPERATURE RISE 

Oil-burner motors shall have either Class A or Class B insulation. 1 The temperature rise above the 
temperature of the cooling medium for each of the various parts of the motor, when tested in accordance 
with the rating, shall not exceed the following values: 

Class of Insulation A B 

Coil Windings, Degrees C* 

Guarded motors 

thermometer 50 70 

resistance 60 80 

Totally enclosed motors 

thermometer 55 75 

resistance 65 85 

The temperatures attained by cores and squirrel-cage windings shall not injure the insulation or the 
machine in any respect. 

*Where two methods of temperature measurement are listed, a temperature rise within the values listed in 
the table, measured by either method, demonstrates conformity with the standard. 

NOTE— All temperature rises are based on an ambient temperature of 40°C. Abnormal deterioration of 
insulation may be expected if this ambient temperature is exceeded in regular operation. 



1 See 1 .66 for description of classes of insulation. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 38 



1 8.98 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

1 8.99 LOCKED-ROTOR CHARACTERISTICS 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR OIL BURNERS 



The locked-rotor torque (see 1.47) and locked-rotor current (see 1.53) of 60-hertz motors, with rated 
voltage and frequency applied, shall be in accordance with the following table: 







Maximum 




Minimum 


Current 


Hp 


Torque, Oz-ft 


Amperes* 




1800 Synchronous Rpm 




1/12 


7.0 


20.0 


1/8 


10.0 


23.0 


1/6 


12.0 


25.0 




3600 Synchronous Rpm 




1/12 


4.0 


20.0 


1/8 


6.0 


22.0 


1/6 


7.0 


24.0 



*1 1 5-volt values. 

18.100 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 

18.101 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
I See 12.44. 

1 8.1 02 DIRECTION OF ROTATION 

The direction of rotation of oil burner motors shall be clockwise facing the end opposite the drive end. 

MANUFACTURING 

18.103 GENERAL MECHANICAL FEATURES 

Oil burner motors shall be constructed with the following mechanical features: (see Figure 18-14) 

a. Guarded or totally enclosed 

b. Motors are to be supplied with nameplate in accordance with 10.39 and in addition marked with 
the words "oil burner motor." 

c. Motors are to be equipped with manual reset inherent thermal overload protector provided with 
suitable marking to so indicate and with directions for resetting. 

d. Motors shall be supplied with: 

1. Terminal leads consisting of two 20-inch lengths of flexible single-conductor wire which enter 
the enclosure through a hole tapped for 1/2-inch conduit located at 3 o'clock facing the end of 
the motor opposite the drive end. 

2. A 1 2-inch maximum length of two-wire 1 8 AWG Type SO cable brought out of the enclosure at 
5 o'clock facing the end of the motor opposite the drive end. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR OIL BURNERS 



MG 1-2009 
Part 18, Page 39 



0.50 




SHAFT END VIEW 



0.34DIA.(2)HOLES- 



ALTERNATE LEAD 
PROVISIONS SEE 18.288 

All dffnenstons in inches 

*lf the shaft extension length of the motor is not suitable for the applications, it is recommended that deviations from this length be in 0.25 inch increments. 

Figure 18-14 
MECHANICAL FEATURES FOR OIL BURNER MOTOR CONSTRUCTION 

All dimensions in inches. 

*lf the shaft extension length of the motor is not suitable for the application, it is recommended that deviations from this length be in 

0.25 inch increments 

18.104 DIMENSIONS FOR FACE-MOUNTING MOTORS FOR OIL BURNERS, TYPES M AND N 

Dimensions and tolerances for face-mounted small motors for oil burners shall be as follows: 
18.104.1 Dimensions 



AJ 



AK 



BD 
Max 



CE 
Max 



6.750 
7.250 



5.500 
6.375 



6.25 
7.00 



7.75 
8.25 



18.105 TOLERANCES 

a. Maximum face runout - 0.008-in. indicator reading 

b. Maximum pilot eccentricity - 0.008-in. indicator reading 

c. AK dimension - +0.000, -0.005 in. 

18.106 FRAME NUMBER AND FRAME SUFFIX LETTER 

18.106.1 Suffix Letter M 

When a motor of a frame size given in 4.4.1 is designed in accordance with the standards for oil burner 
motors and has an AK dimension of 5.500 inches, the frame number shall be followed by the suffix letter 
M to indicate such construction. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 40 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR OIL BURNERS 



18.106.2 Suffix Letter N 

When a motor of a frame size given in 4.4.1 is designed in accordance with the standards for oil burner 
motors and have an AK dimension of 6.375 inches, the frame number shall be followed by the suffix letter 
N to indicate such construction. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 41 

SMALL MOTORS FOR HOME LAUNDRY EQUIPMENT 

SMALL MOTORS FOR HOME LAUNDRY EQUIPMENT 

(A home laundry equipment motor is one which furnishes power for driving a home washing machine, dryer, or a combination 
washer-dryer.) 

18.107 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Single phase 

a. Split phase 

b. Capacitor start 

RATINGS 

18.108 VOLTAGE RATINGS 

The voltage ratings of single-phase motors shall be: 

a. 60 hertz - 1 1 5 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.109 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.110 HORSEPOWER AND SPEED RATINGS 

18.110.1 Horsepower Ratings 

Horsepower ratings shall be 1/12, 1/8, 1/6, 1/4, 1/3, 1/2, and 3/4 horsepower. 

18.110.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz 

1 . Single speed - 1800 rpm synchronous speed, 1725 rpm approximate full-load speed 

2. Two speed - 1800/1200 rpm synchronous speeds, 1725/1140 rpm approximate full-load 
speeds 

b. 50 hertz 

1 . Single speed - 1500 rpm synchronous speed, 1425 rpm approximate full-load speed 

2. Two speed - 1500/1000 rpm synchronous speeds, 1425/950 rpm approximate full-load speeds 

18.111 NAMEPLATE MARKING 

The following information shall be given on all nameplates. For abbreviation see 1.79. For some 
examples of additional information that may be included on the nameplate see 1.70.2. 

a. Manufacturer's name (shall be permitted to be coded) 

b. Manufacturer's type and frame designation 

c. Horsepower output (optional if amperes is marked) 

d. Insulation system designation (if other than Class A) 

e. Rpm at full-load 

f. Frequency 

g. Voltage 

h. Full-load amperes (optional if horsepower is marked) 
I. For motors equipped with thermal protection, the words "thermally protected" or "thermally 

protected L," whichever is applicable (L designates locked rotor protection only) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 42 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR HOME LAUNDRY EQUIPMENT 



TESTS AND PERFORMANCE 



18.112 TEMPERATURE RISE 



Motors for home laundry equipment shall have either Class A, Class B, or Class F insulation. 1 The 
temperature rise, above the temperature of the cooling medium, for each of the various parts of the motor 
when tested in accordance with the rating shall not exceed the following values: 

Coil Windings - Resistance, Degrees C* 

Class A Insulation 60 

Class B insulation 80 

Class F insulation 105 

The temperature attained by cores and squirrel-cage windings shall not injure 
the insulation or the machine in any respect. 

*These temperature rises are based on an ambient temperature of 40°C 

18.113 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34, Table 10-5. 

18.114 MAXIMUM LOCKED-ROTOR CURRENT 

The locked-rotor current of 1 1 5-volt laundry equipment motors shall not exceed 50 amperes when tested 
in accordance with IEEE Std 114 with the current value being read at the end of the 3-second period. 

18.115 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.116 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

| See 12.44. 

MANUFACTURING 

18.117 GENERAL MECHANICAL FEATURES 

Motors for home laundry equipment shall be constructed with the following mechanical features: 

a. Open 

b. Sleeve bearing 

c. Mounting 

The motors shall be provided with one of the following 

1. Mounting rings for resilient mounting. The mounting rings dimensions and the spacing between 
mounting rings shall be as shown in 18.118. 

2. Extended studs. Stud spacing dimensions shall be as shown in 18.118 

d. Shaft extension in accordance with 18.1 18 

e. When blade terminals are used, the blade shall be 0.25 inch wide and 0.03 inch thick. 



1 See 1 .66 for description of classes of insulation. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 Section II 

Part 1 8, Page 44 DEFINITE PURPOSE MACHINES 

MOTORS FOR JET PUMPS 

MOTORS FOR JET PUMPS 

(A jet-pump motor is an open dripproof-type motor built for horizontal or vertical operation for direct-driven centrifugal ejector 
pumps.) 

18.119 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single-phase 

1. Split phase 

2. Capacitor start 

b. Polyphase induction; Squirrel-cage 

RATINGS 

18.120 VOLTAGE RATINGS 

18.120.1 Single-Phase Motors 

The voltage ratings for single-phase motors shall be: 

a. 60 hertz 

1 . Split-phase - 1 1 5 and 230 volts 

2. Capacitor start - 1 1 5/230 volts 1 

b. 50 hertz 

1 . Split-phase - 1 1 and 220 volts 

2. Capacitor start - 1 1 0/220 volts 2 

18.120.2 Polyphase Induction Motors 

The voltage ratings for polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.121 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.122 HORSEPOWER, SPEED, AND SERVICE FACTOR RATINGS 

The horsepower ratings shall be 1/3, 1/2, 3/4, 1, 1-1/2, 2, and 3 horsepower. 
The service factor and minimum rpm at service factor shall be: 

Minimum Rpm at Service 

Hj) Service Factor Factor* 

60 Hertz 

1/3 1.75 3450 

1/2 1.60 3450 

3/4 1.50 3450 

1 1.40 3450 
1-1/2 1.30 3450 

2 1.20 3450 
3 115 3450 

50 Hertz 
All 1.0 2850 

*This speed is obtained in a test at rated voltage when the temperature of the winding 
and the other parts of the machine are at approximately 25°C at the start of the test. 



1 Single-phase three-horsepower are rated for 230-volt operation only. 

2 Single-phase three-horsepower motors are rated for 220-volt operation only. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 1 8, Page 45 

MOTORS FOR JET PUMPS 

TEST AND PERFORMANCE 

1 8.1 23 TEMPERATURE RISE 

Motors for jet pumps shall have a Class A or Class B insulation system. 1 The temperature rise above the 
temperature of the cooling medium shall be in accordance with 12.43 for small ac motors and 12.44 for 
medium ac motors. 

18.124 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.125 TORQUE CHARACTERISTICS 

For breakdown torque, see 12.32 for single-phase induction motors and 12.37 for polyphase induction 
motors. 

18.126 MAXIMUM LOCKED-ROTOR CURRENT 

See 12.33, 12.34, or 12.35, depending on type and rating of motor. 

18.127 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 

18.128 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

i See 12.44. 

18.129 DIRECTION OF ROTATION 

The direction of rotation for jet-pump motors shall be clockwise facing the end opposite the drive end. 

MANUFACTURING 

18.130 GENERAL MECHANICAL FEATURES 

Jet-pump motors shall be constructed with the following mechanical features: 
(See Figures 18-16 and 18-17.) 

a. Open dripproof construction 

b. Grease-lubricated ball bearing on one end suitable for taking axial thrust and with either oil- 
lubricated sleeve bearing or a bail bearing on the other end suitable for horizontal or vertical 
position. The axial thrust may be taken at either end consistent with design practice. 

c. The face mounting for the drive end shall be in accordance with Figure 18-16. 

d. The end shield at the end opposite the drive shall be totally enclosed or shall provide a suitable 
means to accommodate a drip cover when required for vertical mounting. 

e. Standard shaft extension shall be in accordance with Figure 18-16 (frame 56C). Alternate 
standard shaft extension shall be in accordance with Figure 18-17 (frame 56J). 2 

f. Terminals for line lead connections shall be located in the end shield at the end opposite the drive 
end at the 3 o'clock position. 



1 See 1 .66 for description of Class A and Class B insulation systems. 

2 If the shaft extension length of the motor is not suitable for the application, it is recommended that deviations from this length be in 
1/4-inch increments. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 18, Page 46 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR JET PUMPS 



g. The capacitor unit, when mounted externally on capacitor motors, shall be attached to the motor 
frame 90 degrees counterclockwise from the terminal location facing the end opposite the drive 
end as shown by the dotted lines in Figure 18-16. 

h. Frame-mounted nameplates shall be attached to the motor in the area from to 10 degrees 
counterclockwise from the motor terminal location facing the end opposite the drive end. The 
nameplate shall be so located that it will be read when the motor is mounted in a vertical position 
and the drip cover, when used, is in place. Any other instruction plates shall be immediately 
adjacent to the motor nameplate. 

i. Automatic reset thermal overload protector shall be provided on single-phase motors. 

j. When the alternate shaft extension shown in Figure 18-17 is used, a means shall be provided for 
holding the shaft during assembly or removal of the pump impeller (3/32-inch screwdriver slot in 
opposite end of shaft, flat in shaft, etc.). 

18.131 DIMENSION FOR FACE-MOUNTED MOTORS FOR JET PUMPS 1 ' 2 ' 3 



MAX 
5/8-18UNF-2BJAP q 16 

WHENREQ'D . , 10 

i i 



r 

I 



<E= 



<E 



2.06 



Wh* 



ES 



iJL 



' 10.6250 

.0.6245 



1.88 



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R' 

8 f 



All dimensions in inches 



** .56 BOLT PENETRATION 
ALLOWANCE 




4.500 
4.497 



5.875 



Figure 18-16 
FACE-MOUNTED JET PUMP MOTOR DIMENSIONS 



' Face runout or eccentricity of rabbet (with indicator mounted on the shaft) will be within 0.004-inch gage reading. 
For general mechanical features, see 18.130. 
1 See 4.4.1 for key dimensions. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MOTORS FOR JET PUMPS 



MG 1-2009 
Part 18, Page 47 



0.625 
"0 624 THIS SURFACE TO BE SUITABLY 

TREATED TO RESIST CORROSION AND WEAR 



7/16-20 UNF-2AR.H 
2.00 




ECCENTRICITY OF THREADED PORTION 
OF SHAFT IS HELD WITHIN 0.004 T.I.R. 
WITH THE INDICATOR ON O.D.I A OF 
GROUND RING GAGE AS SHOWN, THE 
GAGE BEING STATIONARY WITH RESPECT 
TO THE ROTOR 



0.03X45° CHAMFER 



WHEN FILLET IS PROVIDED, THREADS IN PUMP IMPELLER 

MUST BE RELIEVED ONE THREAD TO CLEAR FILLET AT SHOULDER 



POINT 



All dimensions in inches 



Figure 18-17 
FACE-MOUNTED JET PUMP MOTOR DIMENSIONS 



18.132 FRAME NUMBER AND FRAME SUFFIX LETTER 

When a motor of a frame size given in 4.4,1 is designed in accordance with the standards for jet-pump 
motors and has the alternate standard shaft extension (threaded shaft) shown in Figure 18-17, the frame 
number shall be followed by the suffix letter J to indicate such construction. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 48 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR COOLANT PUMPS 

SMALL MOTORS FOR COOLANT PUMPS 

(A coolant-pump motor is an enclosed ball-bearing-type motor built for horizontal or vertical operation for direct connection to direct- 
driven centrifugal coolant pumps.) 

18.133 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single-phase 

1. Split-phase 

2. Capacitor start 

3. Repulsion-start induction 

b. Polyphase induction 
Squirrel cage, constant speed 

c. Direct current 
Compound wound 

RATINGS 

18.134 VOLTAGE RATINGS 

18.134.1 Single-Phase Motors 

The voltage ratings for single-phase motors shall be: 

a. 60 hertz 

1 . Split-phase - 1 1 5 and 230 volts 

2. Capacitor start 

a) 1/4 horsepower and smaller- 115 and 230 volts 

b) 1/3 horsepower and larger- 115/230 volts 

b. 50 hertz 

1 . Split-phase - 1 10 and 220 volts 

2. Capacitor start 

a) 1 14 horsepower and smaller - 1 1 and 220 volts 

b) 1/3 horsepower and larger - 1 1 0/220 volts 

18.134.2 Polyphase Induction Motors 

The voltage ratings for polyphase motors shall be: 

a. 60 hertz - 220, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.134.3 Direct-current Motors 

115 and 230 volts. 

18.135 FREQUENCIES 

Frequencies for single-phase and polyphase induction motors shall be 50 and 60 hertz. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1 - 2009 

DEFINITE PURPOSE MACHINES Part 18, Page 49 

SMALL MOTORS FOR COOLANT PUMPS 

18.136 HORSEPOWER AND SPEED RATINGS 

Horsepower and speed ratings shall be as noted in the following table: 





60 Hertz 






50 Hertz 


Brake Hp 
Rating 


Synchronous 
Rpm 


Approximate 
Full-Load Rpm 


Synchronous Approximate 
Rpm Full-Load Rpm 


1/20 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/12 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/8 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/6 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/4 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/3 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1/2 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


3/4 


3600 




3450 


3000 


2850 




1800 




1725 


1500 


1425 


1 


3600 




3450 


3000 


2850 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Sectjon|| 

Part 18, Page 50 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR COOLANT PUMPS 

TESTS AND PERFORMANCE 

18.137 TEMPERATURE RISE 

Motors for coolant pumps shall have Class A insulation. 1 

The temperature rise above the temperature of the cooling medium for each of the various parts of the 
motor, when tested in accordance with the rating, shall not exceed the following values: 

Coil Windings, Degrees C 

Single-phase and polyphase-induction motors* 

thermometer 55 

resistance 65 

Direct-current motors - thermometer 55 

Commutators - thermometer 65 

The temperatures attained by cores, squirrel-cage windings, commutators, and 
miscellaneous parts (such as brushholders and brushes, etc.) shall not injure the 
insulation or the machine in any respect. 

*Where two methods of temperature measurement are listed, a temperature rise 
within the values listed in the table, measured by either method, demonstrates 
conformity with the standard. 

NOTE— All temperature rises are based on a maximum ambient temperature of 
40°C. Abnormal deterioration of insulation may be expected if this ambient 
temperature is exceeded in regular operation. 

18.138 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.139 TORQUE CHARACTERISTICS 

For breakdown torque, see 12.32 for single induction motors and 12.37 for polyphase-induction motors. 

18.140 MAXIMUM LOCKED-ROTOR CURRENT 
See 12.33. 

18.141 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.142 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
I See 12.44 and 12.68. 

18.143 DIRECTION OF ROTATION 

The direction of rotation for coolant-pump motors is clockwise, facing the end opposite the drive end. 



1 See 1 .66 for description of Class A insulation. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 51 

SMALL MOTORS FOR COOLANT PUMPS 

MANUFACTURING 

18.144 GENERAL MECHANICAL FEATURES 

Coolant-pump motors shall be constructed with the following mechanical features: 
(see 18.131) 

a. Totally enclosed 

b. Grease-lubricated ball bearings suitable for horizontal or vertical mounting which shall have 
suitable provision for taking axial trust away from the front end. 

c. Back end shield shall be machined in accordance with Figure 18-16, except that the 5/8"-18 
tapped hole in the bearing hub shall be omitted. 

d. The straight shaft extension shall be in accordance with 4.4.1 and 4.5 or, alternatively, in 
accordance with Figure 18-17. 

e. Terminals or leads shall be located in the front end shield or on the frame adjacent to the front end 
shield. 

f. The capacitor unit, when mounted externally on capacitor motors, shall be attached to the motor 
frame 90 degrees counterclockwise from the terminal location while facing the front end of the 
motors. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 52 DEFINITE PURPOSE MACHINES 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 4-INCH 



SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 4-INCH 

(A submersible motor for deep well pumps is a motor designed for operation while totally submerged in water having a temperature 
not exceeding 25°C (77°F).) 

18.145 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

a. Single-phase 

1. Split-phase 

2. Capacitor 

b. Polyphase induction: Squirrel cage, constant speed 

RATINGS 

18.146 VOLTAGE RATINGS 

18.146.1 Single-Phase Motors 

The voltage ratings for single-phase motors shall be: 

a. 60 hertz - 1 1 5 and 230 volts 

b. 50 hertz - 1 1 and 220 volts 

18.146.2 Polyphase Induction Motors 

The voltage ratings for polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.147 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.148 HORSEPOWER AND SPEED RATINGS 

18.148.1 Horsepower Ratings 

Horsepower ratings shall be: 

a. Single-phase, 115 volts - 1/4, 1/3, and 1/2 horsepower 

b. Single-phase, 230 volts- 1/4, 1/3, 1/2, 3/4, 1, 1-1/2, 2, and 3 horsepower 

c. Polyphase induction - 1/4, 1/3, 1/2, 3/4, 1, 1-1/2, 2, 3, and 5 horsepower 

18.148.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 3600 rpm synchronous speed 

b. 50 hertz - 3000 rpm synchronous speed 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 53 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS^-INCH 

TESTS AND PERFORMANCE 

18.149 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.150 LOCKED-ROTOR CURRENT 

18.150.1 Single-Phase Small Motors 

For single-phase small motors, see 12.33. 

18.150.2 Single-Phase Medium Motors 

For single-phase medium motors, see 12.34. 

18.150.3 Three-Phase Medium Motors 

For three-phase medium squirrel-cage induction motors, see 12.35. 

18.151 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.152 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 

I See 12.44. 
Length and size of cable should be taken into consideration, and the motor manufacturer should be 
consulted. 

18.153 VARIATION FROM RATED FREQUENCY 

i See 12.44. 

18.154 DIRECTION OF ROTATION 

The direction of rotation for submersible motors is clockwise facing the end opposite the drive end. 

18.155 THRUST CAPACITY 

When submersible pump motors are operated in a vertical position with the shaft up, they shall be 
capable of withstanding the following thrust: 



Horsepower Thrust, Pounds 

1/4-1-1/2, incl. 300 
2-5, include. 900 

MANUFACTURING 
18.156 TERMINAL LEAD MARKINGS 

The terminal lead markings for single-phase submersible pump motors shall be as follows: 

a. Auxiliary winding - red 

b. Main winding - black 

c. Common auxiliary winding and main winding - yellow 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 55 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS-6-INCH 



SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 6-INCH 

(A submersible motor for deep well pumps is a motor designed for operation while totally submerged in water having a temperature 
not exceeding 25X (77°F).) 

18.158 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

See 18.145. 

RATINGS 

18.159 VOLTAGE RATINGS 

18.159.1 Single-Phase Motors 

The voltage ratings for single-phase motors shall be: 

a. 60 hertz - 230 volts 

b. 50 hertz - 220 volts 

18.159.2 Polyphase Induction Motors 

The voltage ratings for polyphase motors shall be: 

a. 60 hertz - 200, 230, 460, and 575 volts 

b. 50 hertz - 220 and 380 volts 

18.160 FREQUENCIES 
See 18.147. 

18.161 HORSEPOWER AND SPEED RATINGS 

18.161.1 Horsepower Ratings 

Horsepower ratings shall be: 

a. Single-phase 230 volts - 3, 5, and 7-1/2 horsepower 

b. Polyphase induction - 3, 5, 7-1/2, 10, 15, 20, 25, and 30 horsepower 

18.161.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 3600 rpm synchronous speed 

b. 50 hertz - 3000 rpm synchronous speed 

TESTS AND PERFORMANCE 

18.162 BASIS FOR HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.163 LOCKED-ROTOR CURRENT 

18.163.1 For single-phase medium motors, see 12.34. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 56 DEFINITE PURPOSE MACHINES 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 6-INCH 



18.163.2 For three-phase medium squirrel-cage induction motors, the locked-rotor current, when 

measured with rated voltage and frequency impressed and with rotor locked, shall not exceed the 
following: 



Three 


-phase 60 Hertz Motors at 230 Volts* 




Hp 


Locked-Rotor Current, 


Amperes 


3 


64 




5 


92 




IV* 


130 




10 


190 




15 


290 




20 


390 




25 


500 




30 


600 





*Locked-rotor current of motors designed for voltages other than 230 volts 
shall be inversely proportional to the voltages. 

1 8.1 64 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.165 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 

See 12.44. Length and size of cable should be taken into consideration, and the motor manufacturer 
should be consulted. 

18.166 VARIATION FROM RATED FREQUENCY 
See 12.44. 

18.167 DIRECTION OF ROTATION 
See 18.154. 

18.168 THRUST CAPACITY 

When submersible pump motors are operated in a vertical position with the shaft up, they shall be 
capable of withstanding the following thrusts: 



Hp 


Thrust, pounds 


3 


300 


5 


500 


7-1/2 


750 


10 


1000 


15 


1500 


20 


2000 


25 


2500 


30 


3000 



MANUFACTURING 
18.169 TERMINAL LEAD MARKINGS 

See 18.156. 



© Copyright 2009 by the National Electrical Manufacturers Association. 





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MG 1-2009 Section II 

Part 1 8, Page 58 DEFINITE PURPOSE MACHINES 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 8-INCH 



SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 8-INCH 

(A submersible motor for deep well pumps is a motor designed for operation while totally submerged in water having a temperature 
not exceeding 25°C (77°F).) 

18.171 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Polyphase induction squirrel-cage, constant speed. 

RATINGS 

18.172 VOLTAGE RATINGS 

Voltage ratings shall be: 

a. 60 hertz - 460 and 575 volts 

b. 50 hertz - 380 volts 

18.173 FREQUENCIES 

Frequencies shall be 60 and 50 hertz. 

18.174 HORSEPOWER AND SPEED RATINGS 

18.174.1 Horsepower Ratings 

Horsepower ratings shall be 40, 50, 60, 75, and 100 horsepower. 

18.174.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 3600 rpm synchronous speed 

b. 50 hertz - 3000 rpm synchronous speed 

TESTS AND PERFORMANCE 

18.175 LOCKED-ROTOR CURRENT 

For squirrel-cage induction motors, the locked-rotor current, when measured with rated voltage and 
frequency impressed and with rotor locked, shall not exceed the following: 



Three-Phase 60 Hertz Motors at 460 Volts* 
Hj) Locked- Rotor current, Amperes 

40 380 

50 470 

60 560 

75 700 

100 930 

*Locked-rotor current of motors designed for voltages other than 460 volts 
shall be inversely proportional to the voltages. 



1 8.1 76 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES p art 18 Paqe 59 

SUBMERSIBLE MOTORS FOR DEEP WELL PUMPS— 8-INCH 



18.177 VARIATION FROM RATED VOLTAGE AT CONTROL BOX 

1 See 12.44. Length and size of cable should be taken into consideration, and the motor manufacturer 
1 should be consulted. 

18.178 VARIATION FROM RATED FREQUENCY 

1 See 12.44. 

18.179 DIRECTION OF ROTATION 
See 18.154. 

18.180 THRUST CAPACITY 

When submersible pump motors are operated in a vertical position with the shaft up, they shall be 
capable of withstanding the following thrust: 





Hp 


Thrust, Pounds 






40 


4000 






50 


5000 






60 


6000 






75 


7500 






100 


10000 





© Copyright 2009 by the National Electrical Manufacturers Association. 



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Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 61 

MEDIUM DC ELEVATOR MOTORS 

MEDIUM DC ELEVATOR MOTORS 

18.182 CLASSIFICATION ACCORDING TO TYPE 

18.182.1 Class DH 

Class DH direct-current high-speed elevator motors are open-type motors for use with gear-driven 
elevators. Speed variation is obtained primarily by armature voltage control. 

18.182.2 Class DL 

Class DL direct-current low-speed elevator motors are open-type motors for the use with gearless 
elevators. Speed variation is obtained primarily by armature voltage control. 

RATINGS 

18.183 VOLTAGE RATINGS 

Because the speed variation of direct-current elevator motors is primarily obtained by armature voltage 
control, these motors are operated over a wide range of voltages. Usually the highest applied armature 
voltage should not exceed 600 volts. Whenever possible, it is recommended that voltage ratings of 230 or 
240 volts should be utilized for motors of all horsepower ratings, although voltage ratings of 115 or 120 
volts may be used for motors having ratings of 10 horsepower and smaller. 

18.184 HORSEPOWER AND SPEED RATINGS 

18.184.1 Class DH 

When the voltage rating of a Class DH direct-current elevator motor is either 230 or 240 volts (see 
18.183), the horsepower and speed ratings shall be: 



Hp 




Speed, Rpm 




TA 


1750 


1150 


850 




10 


1750 


1150 


850 




15 


1750 


1150 


850 




20 


1750 


1150 


850 


650 


25 


1750 


1150 


850 


650 


30 


1750 


1150 


850 


650 


40 


1750 


1150 


850 


650 


50 




1150 


850 


650 


60 




1150 


850 


650 


75 






850 


650 


100 






850 


650 



18.184.2 Class DL 

Because of the multiplicity of combinations of traction sheave diameters, car speeds, car loading ratings, 
and roping, it is impracticable to develop a standard for horsepower and speed ratings for Class DL 
direct-current elevator motors. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 62 DEFINITE PURPOSE MACHINES 

MEDIUM DC ELEVATOR MOTORS 



18.185 BASIS OF RATING 

18.185.1 Class DH 

A Class DH direct-current elevator motor shall have a time rating of 15 minutes, 30 minutes, or 60 
minutes. When operated at rated horsepower, speed, and time, the temperature rise of the motor shall be 
in accordance with 18.192. 

18.185.2 Class DL 

A Class DL direct-current elevator motor shall have a time rating of 60 minutes. When operated at rated 
horsepower, speed, and time, the temperature rise of the motor shall be in accordance with 18.192. 

NOTE— When the elevator duty cycle permits, a Class DL direct-current elevator motor may have a time rating of 30 minutes. 

18.186 NAMEPLATE MARKINGS 
See 10.66. 

TESTS AND PERFORMANCE 

18.187 ACCELERATION AND DECELERATION CAPACITY 

Class DH or DL direct-current elevator motors shall be capable of carrying successfully at least 200 
percent of rated armature current for a period not to exceed 3 seconds at any voltage up to 70 percent of 
rated armature voltage and a momentary load of at least 230 percent of rated armature current within the 
same voltage range. 

18.188 VARIATION IN SPEED DUE TO LOAD 

18.188.1 Class DH 

When Class DH direct-current elevator motors (see 18.184) are operated at rated voltage, the variation in 
speed from full-load to no-load hot, based upon full-load speed hot with constant field current maintained, 
shall not exceed 10 percent. 

18.188.2 Class DL 

When Class DL direct-current elevator motors are operated at rated voltage, the variation in speed from 
full-load to no-load hot, based upon full-load speed hot with constant field current maintained, shall not 
exceed 20 percent. 

18.189 VARIATION FROM RATED SPEED 

When Class DH or Class DL direct-current elevator motors (see 18.184) are operated at rated armature 
and field voltage and load, the actual full-load speed hot shall not vary by more than plus or minus 7.5 
percent from rated speed. 

18.190 VARIATION IN SPEED DUE TO HEATING 

18.190.1 Open-Loop Control System 

When a Class DH or Class DL direct-current elevator motor is intended for use in an open-loop elevator 
control system and is operated at rated armature and field voltage and load, the variation in speed from 
full-load cold to full-load hot during a run of a specified duration shall not exceed 10 percent of the full- 
load speed hot. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 63 

MEDIUM DC ELEVATOR MOTORS 



18.190.2 Closed-Loop Control System 

When a Class DH or Class DL direct-current elevator motor is intended for use in a closed-loop elevator 
control system and is operated at rated armature and field voltage and load, the variation in speed from 
full-load cold to full-load hot during a run of a specified duration shall not exceed 15 percent of the full- 
load speed hot. 

18.191 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 

18.192 TEMPERATURE RISE 

The temperature rise, above the temperature of cooling medium, for each of the various parts of Class 
DH and Class DL direct-current elevator motors, when tested in accordance with the rating, shall not 
exceed the values given in the following table. All temperature rises are based on a maximum ambient 
temperature of 40°C. Temperatures shall be determined in accordance with IEEE Std 113. 



Time Rating 15 30 and 60 

minutes minutes 



Class of Insulation* A B A B 

Load, Percent of Rated Capacity 100 100 100 100 

Temperature Rise, t Degrees C 

a. Armature windings and all other windings other than those given in items 

b and c - resistance 80 115 70 100 

b. Multi-layer field windings - resistance 80 115 70 100 

c. Single-layer field windings with exposed uninsulated surfaces and bare 

copper windings - resistance 80 115 70 100 

d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) 
shall not injure the insulation or the machine in any respect. 

*See 1 .66 for description of classes of insulation. 

**AII temperature rises are based on a maximum ambient temperature of 40°C. Temperatures shall be determined in accordance 
with IEEE Std 113. Abnormal deterioration of insulation may be expected if this ambient temperature is exceeded in regular 
operation. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 64 DEFINITE PURPOSE MACHINES 

MOTOR-GENERATOR SETS FOR DC ELEVATOR MOTORS 

MOTOR-GENERATOR SETS FOR DC ELEVATOR MOTORS 

(A motor-generator set consisting of an open-type induction motor direct-connected to an open-type direct-current adjustable-voltage 
generator for supplying power to a direct-current elevator motor.) 

RATINGS 

18.193 BASIS OF RATING 

18.193.1 Time Rating 

The induction motor and the direct-current adjustable-voltage generator shall each have a continuous 
time rating. 

18.193.2 Relation to Elevator Motor 

The kilowatt rating of the direct-current adjustable-voltage generator and the horsepower rating of the 
induction motor do not necessarily bear any definite relation to the rating of the direct-current elevator 
motor to which they furnish power because of the difference in time rating. 

18.194 GENERATOR VOLTAGE RATINGS 

18.194.1 Value 

The direct-current adjustable-voltage generator shall be capable of producing the rated voltage of the 
direct-current elevator motor to which it is supplying power. 

18.194.2 Maximum Value 

Since the direct-current elevator motor and the direct-current adjustable-voltage generator are rated on 
different bases, the generator rated voltage may be less than that of the direct-current elevator motor. 
Usually the highest rated voltage of the generator should not exceed 600 volts. Whenever possible, it is 
recommended that the rated voltage of the generator be 250 volts. 

TESTS AND PERFORMANCE 

18.195 VARIATION IN VOLTAGE DUE TO HEATING 

18.195.1 Open-Loop Control System 

When an elevator direct-current adjustable-voltage generator is intended for use in an open-loop control 
system, the change in armature voltage from full-load cold to full-load hot, with a fixed voltage applied to 
the generator field, shall not exceed 10 percent. 

18.195.2 Closed-Loop Control System 

When an elevator direct-current adjustable-voltage generator is intended for use in a closed-loop control 
system, the change in armature voltage from full-load cold to full-load hot, with a fixed voltage applied to 
the generator field, shall not exceed 15 percent. 

18.196 OVERLOAD 

Both the induction motor and the direct-current adjustable-voltage generator shall be capable of supplying 
the peak load required for the direct-current elevator motor to which it is supplying power. See 18.187. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 p aqe 65 

MOTOR-GENERATOR SETS FOR DC ELEVATOR MOTORS 



18.197 HIGH-POTENTIAL TEST 

The various parts of the set shall be given high-potential tests in accordance with 3.1 for single-phase 
and polyphase induction motors and in accordance with 15.48 for direct-current generators. 

18.198 VARIATION FROM RATED VOLTAGE 

All sets shall operate successfully at rated load and frequency with the motor voltage not more than 10 
percent above or below the nameplate rating but not necessarily in accordance with the standards 
established for operation at normal rating. 

18.199 VARIATION FROM RATED FREQUENCY 

All sets shall operate successfully at rated load and voltage with the motor frequency not more than 5 
percent above or below the nameplate rating but not necessarily in accordance with the standards 
established for operation at normal rating. 

18.200 COMBINED VARIATION OF VOLTAGE AND FREQUENCY 

All sets shall operate successfully at rated load with a combined variation in motor voltage and frequency 
not more than 10 percent above or below the nameplate rating, provided the limits of variations given in 
18.198 and 18.199 are not exceeded, but not necessarily in accordance with the standards established 
for operation at normal rating. 

1 8.201 TEMPERATURE RISE 

The temperature rise, above the temperature of the cooling medium, for each of the various parts of each 
machine in the set, when tested in accordance with their ratings, shall not exceed the following values: 

18.201.1 Induction Motors 

See 12.44. 

18.201.2 Direct-Current Adjustable-Voltage Generators 



Class of Insulation* A B 

Load, Percent of Rated Capacity 10 100 

Time Rating - Continuous 
Temperature Rise, **Degrees C 

a. Armature windings and all other windings other than those given in items b and c - resistance 70 1 00 

b. Multi-layer field windings - resistance 70 100 

c. Single-layer field windings with exposed uninsulated surfaces and bare copper windings - resistance 70 100 

d. The temperature attained by cores, commutators, and miscellaneous parts (such as brushholders, brushes, pole tips, etc.) 
shall not injure the insulation or the machine in any respect. 



*See 1 .66 for description of classes of insulation. 

**AII temperature rises are based on a maximum ambient temperature of 40°C. Temperatures shall be determined in accordance 
with IEEE Std 113. Abnormal deterioration of insulation may be expected if this ambient temperature is exceeded in regular 
operation. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 66 DEFINITE PURPOSE MACHINES 

MEDIUM AC POLYPHASE ELEVATOR MOTORS 

MEDIUM AC POLYPHASE ELEVATOR MOTORS 

18.202 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Polyphase alternating-current high-speed motors, Class AH, for use with gear-driven elevators shall 
include: 

18.202.1 AH1 

All single-speed internal-resistance-type elevator motors having a squirrel-cage secondary or other form 
of secondary winding having no external connection and designed for only one synchronous speed. 

18.202.2 AH2 

All single-speed external-resistance-type elevator motors having a wound secondary with means for 
connection to an external starting resistance and designed for only one synchronous speed. 

18.202.3 AH3 

All multispeed internal-resistance-type elevator motors having a squirrel-cage secondary or other forms of 
secondary winding having no external connection and designed to give two or more synchronous speeds. 

RATINGS 

18.203 BASIS OF RATING— ELEVATOR MOTORS 

Squirrel-cage elevator motors shall be rated primarily on the basis of locked-rotor torque, but they may 
also be given a horsepower rating. The horsepower ratings shall be those ratings given under 18.206 and 
shall be the brake-horsepower the motor will actually develop without exceeding the standard 
temperature rise for the standard time rating as given in 18.208. 

18.204 VOLTAGE RATINGS 

The voltage ratings shall be: 

a. Class AH 1 motors, 1 horsepower to 10 horsepower, inclusive, at 1200 and 1800 rpm - 115 volts 

b. Class AH1 motors other than those covered in item a, Class AH2 motors, and Class AH3 motors - 
200, 230, 460, and 575 volts 

18.205 FREQUENCY 

The frequency shall be 60 hertz. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 67 

MEDIUM AC POLYPHASE ELEVATOR MOTORS 



18.206 HORSEPOWER AND SPEED RATINGS 

Horsepower and synchronous speed ratings of open-type Class AH1 squirrel-cage motors for elevators 
and similar applications shall be as given in the following table: 





60 HERTZ, TWO- 


AND THREE-PHASE 




Hp 




Synchronous Speed, Rpm 




1 


1800 


1200 










2 


1800 


1200 










3 


1800 


1200 










5 


1800 


1200 




900 






TA 


1800 


1200 




900 


720 




10 


1800 


1200 




900 


720 


600 


15 


1800 


1200 




900 


720 


600 


20 


1800 


1200 




900 


720 


600 


25 


1800 


1200 




900 


720 


600 


30 








900 


720 


600 


40 








900 


720 


600 



TESTS AND PERFORMANCE 

18.207 LOCKED-ROTOR TORQUE FOR SINGLE-SPEED SQUIRREL-CAGE ELEVATOR MOTORS 

The locked-rotor torque for Class AH1 elevator motors, with rated voltage and frequency applied, shall be 
not less than 285 percent of rated synchronous torque. 

For the selection of gearing and other mechanical design features of the elevator, 335 percent of rated 
synchronous torque shall be used as a maximum value of locked-rotor torque for Class AH1 elevator 
motors. 

18.208 TIME-TEMPERATURE RATING 

The rated horsepower or torque of elevator motors under Class AH1 shall be based on a 30-minute run at 
rated horsepower or rated torque and corresponding speed with a temperature rise not to exceed the 
values given in 12.44. 

1 8.209 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.210 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

J See 12.44. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 68 DEFINITE PURPOSE MACHINES 

MEDIUM AC POLYPHASE ELEVATOR MOTORS 



MANUFACTURING 

1 8.21 1 NAMEPLATE MARKING 

1 The following information shall be given on all nameplates. For abbreviations, see 1.79. For some 
I examples of additional information that may be included on the nameplate see 1.70.2. 

a. Manufacturer's type designation (optional) 

b. Horsepower rating 

c. Time rating 

d. Temperature rise 

e. Rpm at full load 

f. Starting torque (pounds at 1 foot) 

g. Frequency 
h. Number of phases 
I. Voltage 
j. Full-load amperes 
k. Code letter for locked-rotor kVA (see 1 0.37) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MEDIUM AC CRANE MOTORS 



MG 1-2009 
Part 18, Page 69 



MEDIUM AC CRANE MOTORS 
RATINGS 



18.212 VOLTAGE RATINGS 

Voltage ratings shall be: 





Hp 


Voltage Ratings, Volts 








60 Hertz 




MO, incl. 




115, 200, 230,460, and 575 




15-125, incl. 




200, 230, 460, and 575 




150 




460 and 575 








50 Hertz 




1-125, incl. 




220 and 380 




150 




380 





18.213 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

18.214 HORSEPOWER AND SPEED RATINGS 

Horsepower and speed ratings for intermittent-rated alternating-current wound-rotor crane motors shall 
be: 



Hertz 


60 


60 


60 


60 


60 


50 


50 


50 


50 


50 


Ratings 






















Hp 










Synchronous 


Speed, Rpm 










1 


1800 


1200 








1500 


1000 








VA 


1800 


1200 








1500 


1000 








2 


1800 


1200 


900 






1500 


1000 


750 






3 


1800 


1200 


900 






1500 


1000 


750 






5 


1800 


1200 


900 






1500 


1000 


750 






7% 


1800 


1200 


900 






1500 


1000 


750 






10 


1800 


1200 


900 






1500 


1000 


750 






15 


1800 


1200 


900 






1500 


1000 


750 






20 


1800 


1200 


900 


720 




1500 


1000 


750 


600 




25 


1800 


1200 


900 


720 




1500 


1000 


750 


600 




30 


1800 


1200 


900 


720 




1500 


1000 


750 


600 




40 


1800 


1200 


900 


720 


600 


1500 


1000 


750 


600 


500 


50 


1800 


1200 


900 


720 


600 


1500 


1000 


750 


600 


500 


60 


1800 


1200 


900 


720 


600 


1500 


1000 


750 


600 


500 


75 


1800 


1200 


900 


720 


600 


1500 


1000 


750 


600 


500 


100 


1800 


1200 


900 


720 


600 


1500 


1000 


750 


600 


500 


125 


1800 


1200 




720 


600 


1500 


1000 




600 


500 


150 


1800 








600 


1500 








500 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 70 DEFINITE PURPOSE MACHINES 

MEDIUM AC CRANE MOTORS 



18.215 SECONDARY DATA FOR WOUND-ROTOR CRANE MOTORS 



Hp 
Rating 

1 


Secondary 
Volts* 

90 


Maximum 

Secondary 

Amperes 

6 


External 

Resistance,** 

Ohms 


Hp 
Rating 


Secondary 
Volts* 


Maximum 

Secondary 

Ampere 


External 

Resistance,** 

Ohms 


7 


25 


220 


60 


1.75 


1-1/2 


110 


7.3 


7 


30 


240 


65 


1.75 


2 


120 


8.4 


7 


40 


315 


60 


2.75 


3 


145 


10 


7 


50 


350 


67 


2.75 


5 


140 


19 


3.5 


60 


375 


74 


2.75 


7-1/2 


165 


23 


3.5 


75 


385 


90 


2.30 


10 


195 


26.5 


3.5 


100 


360 


130 


1.50 


15 


240 


32.5 


3.5 


125 


385 


150 


1.40 


20 


265 


38 


3.5 


150 


380 


185 


1.10 



'Tolerance plus or minus 10 percent 

**Tolerance plus or minus 5 percent 

NOTE— 100 percent external ohms is the resistance per leg in a 3-phase wye-connected bank of resistance which will limit the 

motor locked-rotor torque to 100 percent. 

18.216 NAMEPLATE MARKING 

The following minimum amount of information shall be given on all nameplates: 
For abbreviations, see 1.79. 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Class of insulation system and maximum ambient temperature for which motor is designed (see 
12.44.1) 

e. Rpm at full load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Full-load primary amperes 

j. Secondary amperes at full load 

k. Secondary open-circuit voltage 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

MEDIUM AC CRANE MOTORS 



MG 1-2009 
Part 18, Page 71 



18.217 FRAME SIZES FOR TWO- AND THREE-PHASE 60-HERTZ OPEN AND TOTALLY ENCLOSED 
WOUND-ROTOR CRANE MOTORS HAVING CLASS B INSULATION SYSTEMS 





Time Rating, Enclosure 




Synchronous Speed, Rpm 




Hp Rating 


1800 


1200 
Frame Designation* 


900 


10 


30 minutes, open 


256X 


284X 


286X 


15 




284X 


286X 


324X 


20 


30 minutes, totally enclosed 


286X 
324X 
326X 


324X 
326X 


326X 


25 


364X 


30 


364X 
364X 


364X 


40 




364X 


365X 


50 


60 minutes, open 


364X 


365X 


404X 


60 




365X 


404X 


405X 


75 


30 minutes, totally enclosed 


404X 


405X 


444X 


100 




405X 


444X 


445X 


125 




444X 


445X 




150 




445X 







*Dimensions for these frame designations are given in 18.230. 



TESTS AND PERFORMANCE 



18.218 TIME RATINGS 



The time ratings for open and totally enclosed alternating-current wound-rotor motors shall be 15, 30, and 
60 minutes. 

1 8.21 9 TEMPERATURE RISE 

For temperature rise of Class B insulation system, see 12.44. 

1 8.220 BREAKDOWN TORQUE 

18.220.1 Minimum Value 

The breakdown torque for alternating-current wound-rotor crane motors, with rated voltage and frequency 
applied, shall be not less than 275 percent of full-load torque. 

18.221 .2 Maximum Value 

For the selection of gearing and other mechanical design features of the crane, 375 percent of rated full- 
load torque shall be used as the maximum value of breakdown torque for an alternating-current wound- 
rotor crane motor. 

1 8.222 HIGH-POTENTIAL TEST 

See 3.1 and 12.3. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 72 DEFINITE PURPOSE MACHINES 

MEDIUM AC CRANE MOTORS 



18.223 OVERSPEEDS 

Alternating-current wound-rotor crane motors having standard horsepower and speed ratings and built in 
frame sizes given in 18.217 shall be so constructed that they will withstand, without mechanical injury, an 
overspeed which is 50 percent above synchronous speed. 

18.224 PLUGGING 

Alternating-current wound-rotor crane motors shall be designed to withstand reversal of the phase 
rotation of the power supply at rated voltage when running at the overspeed given in 18.223. 

18.225 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

See 12.44. 

18.226 ROUTINE TESTS 

The routine tests shall be: 

a. No-load readings of current and speed at normal voltage and frequency and with collector rings 
short-circuited. On 50-hertz motors, these readings shall be permitted to be taken at 60 hertz if 50 
hertz is not available. 

b. Measurement of open-circuit voltage ratio 

c. High-potential test in accordance with 3.1 and 12.3 

18.227 BALANCE OF MOTORS 

See Part 7. 

18.228 BEARINGS 

Bearings for wound-rotor crane motors shall be of the antifriction type. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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MG 1-2009 
Part 18, Page 74 



Section II 

DEFINITE PURPOSE MACHINES 

MEDIUM AC CRANE MOTORS 



18.230 DIMENSIONS AND TOLERANCES FOR ALTERNATING-CURRENT OPEN AND TOTALLY 
ENCLOSED WOUND-ROTOR CRANE MOTORS HAVING ANTIFRICTION BEARINGS 1 



Frame 






















Designation 


A Max 


D* 




E** 




2F** 




AAMin 


A 


H** 


254X 


12.50 


6.25 




5.00 




8.25 




1 


4.25 


0.53 


256X 


12.50 


6.25 




5.00 




10.00 




1 


4.25 


0.53 


284X 


14.00 


7.0 




5.50 




9.50 




1-1/4 


4.75 


0.53 


286X 


14.00 


7.0 




5.50 




11.00 




1-1/4 


4.75 


0.53 


324X 


16.00 


8.0 




6.25 




10.50 




1-1/2 


5.25 


0.66 


326X 


16.00 


8.0 




6.25 




12.00 




1-1/2 


5.25 


0.66 


364X 


18.00 


9.0 




7.00 




11.25 




2 


5.88 


0.66 


365X 


18.00 


9.0 




7.00 




12.25 




2 


5.88 


0.66 


404X 


20.00 


10.0 




8.00 




12.25 




2 


6.62 


0.81 


405X 


20.00 


10.0 




8.00 




13.75 




2 


6.62 


0.81 


444X 


22.00 


11.0 




9.00 




14.50 




2-1/2 


7.50 


0.81 


445X 


22.00 


11.0 




9.00 




16.50 




2-1/2 


7.50 


0.81 










Drive End-Straight 


Shaft Extensionf 








ation U 


N-W 






VMin 






Keyseat f 




Frame Design* 




R 




ESMin 


S 


254X 


1.3750 


3.75 






3.50 




1.201 




2.78 


0.312 


256X 


1 .3750 


3.75 






3.50 




1.201 




2.78 


0.312 


284X 


1.625 


3.75 






3.50 




1.416 




2.53 


0.375 


286X 


1.625 


3.75 






3.50 




1.416 




2.53 


0.375 


324X 


1.875 


3.75 






3.50 




1.591 




2.41 


0.500 


326X 


1.875 


3.75 






3.50 




1.591 




2.41 


0.500 


364X 


2.375 


4.75 






4.50 




2.021 




3.03 


0.625 


365X 


2.375 


4.75 






4.50 




2.021 




3.03 


0.625 


404X 


2.875 


5.75 






5.50 




2.450 




3.78 


0.750 


405X 


2.875 


5.75 






5.50 




2.450 




3.78 


0.750 


444X 


3.375 


5.50 






5.25 




2.880 




4.03 


0.875 


445X 


3.375 


5.50 






5.25 




2.880 




4.03 


0.875 


Opposite Drive End-Shaft Extensionf 




Shaft Style 














Shaft 




Keyseat t 


Frame 






Designation 


FU 


FN-FW 


FVtt 


FX 


FY 


FZMax 


Threaded Width 


Depth Length t 


254X 


Straight 1.1250 


3.00 


2.75 












0.250 


0.125 2.41 


256X 


Straight 1.1250 


3.00 


2.75 












0.250 


0.125 2.41 


284X 


Tapered 1.3750 


4.12 


2.62 


2.75 


1.25 


2.00 


1-12 


0.312 


0.156 2.25 


286X 


Tapered 1.3750 


4.12 


2.62 


2.75 


1.25 


2.00 


1-12 


0.312 


0.156 2.25 


324X 


Taperedft 1625 


4.50 


2.88 


3.00 


1.25 


2.00 


1-12 


0.375 


0.188 2.50 


326X 


Tapered ft 1 -625 


4.50 


2.88 


3.00 


1.25 


2.00 


1-12 


0.375 


0.188 2.50 


364X 


Tapered tt 2.125 


4.88 


3.50 


3.62 


1.38 


2.75 


1-1/2-8 


0.500 


0.250 3.25 


365X 


Tapered ft 2.125 


4.88 


3.50 


3.62 


1.38 


2.75 


1-1/2-8 


0.500 


0.250 3.25 


404X 


Tapered ft 2.375 


5.25 


3.75 


3.88 


1.50 


3.25 


1-3/4-8 


0.625 


0.312 3.50 


405X 


Tapered ft 2.375 


5.25 


3.75 


3.88 


1.50 


3.25 


1-3/4-8 


0.625 


0.312 3.50 


444X 


Tapered ft 2.625 


5.88 


4.12 


4.25 


1.75 


3.62 


2-8 


0.625 


0.312 3.88 


445X 


Tapered ft 2.625 


5.88 


4.12 


4.25 


1.75 


3.62 


2-8 


0.625 


0.312 3.88 


(See next page for notes.) 





















1 For meaning of letter dimensions, see 4.1 and 18.229. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 75 

MEDIUM AC CRANE MOTORS 

All dimensions in inches. 

* Dimension D will never be greater than the above values, but it may be less such that shims are usually required for coupled 

or geared machines. When the exact dimension is required, shims up to 0.03 inch may be necessary. 
** The tolerance for the E and 2F dimensions shall be ± 0.03 inch and for the H dimension shall be + 0.05 inch, - inch, 
t For tolerances on shaft extensions and keyseats, see 4.9. 
ttFor straight shafts, this is a minimum dimension. 
$ The tolerance on the length of the key is ±0.03 inch. 
tfThe standard taper of shafts shall be at the rate of 1 .25 inches in diameter per foot of length. The thread at the end of the 

tapered shaft shall be provided with a nut and a suitable locking device. 



> Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 76 DEFINITE PURPOSE MACHINES 

MEDIUM SHELL-TYPE MOTORS FOR WOODWORKING AND MACHINE-TOOL APPLICATIONS 



MEDIUM SHELL-TYPE MOTORS FOR WOODWORKING AND MACHINE-TOOL APPLICATIONS 

18.231 DEFINITION OF SHELL-TYPE MOTOR 

A shell-type motor consists of a stator and rotor without shaft, end shields, bearings, or conventional 
frame. Separate fans or fans larger than the rotor are not included. 

18.232 TEMPERATURE RISE— SHELL-TYPE MOTOR 

The temperature rise of a shell-type motor depends on the design of the ventilating system as well as on 
the motor losses. The motor manufacturer's responsibility is limited to (a) supplying motors with losses, 
characteristics, current densities, and flux densities consistent with complete motors of similar ratings, 
size, and proportion: and (b) when requested, supplying information regarding the design of a ventilating 
system which will dissipate the losses within the rated temperature rise. 

Therefore, obviously, the machine manufacturer is ultimately responsible for the temperature rise. 

18.233 TEMPERATURE RISE FOR 60-HERTZ SHELL-TYPE MOTORS OPERATED ON 50-HERTZ 

When 40°C continuous 60-hertz single-speed shell-type motors are designed as suitable for operation on 
50-hertz circuits at the 60-hertz voltage and horsepower rating, they will operate without injurious heating 
if the ventilation system is in accordance with the motor manufacturers' recommendations. 

1 8.234 OPERATION AT OTHER FREQUENCIES— SHELL-TYPE MOTORS 

All two-pole 40°C continuous 60-hertz shell-type motors shall be capable of operating on proportionally 
increased voltage at frequencies up to and including 120 hertz. The horsepower load shall be permitted 
to be increased in proportion to one half of the increased speed. 

18.235 RATINGS AND DIMENSIONS FOR SHELL-TYPE MOTORS 1 

18.235.1 Rotor Bore and Keyway Dimensions, Three-Phase 60-Hertz 40°C Open Motors, 208, 220, 

440, and 550 Volts 
18.235.1.1 Straight Rotor Bore Motors 



Hp Rating 




Rotor Bores 


Rotor 


Keyways 


Two Pole 


Normal Diameter 
Inches 


Maximum Minimum 
Diameter Inches Diameter, Inches 


Bores, Inches 


Keys, Inches 


BH = 8-Inch Diameter 


1-1/2 to 10 


1-1/2 


2 None 


1-1/2 to 1-3/4, incl. 
2 


3/8x3/16 
1/2 x 1/4 


BH - 10-Inch Diameter 


7-1/2 to 20 


1-7/8 


2-3/8-4-, 6-, & 8- None 
pole motors* 

2-1/8-2 pole None 

motors 


1-7/8 
2 to 2-3/8, incl. 


3/8x3/16 
1/2x1/4 


BH = 12.375-Inch Diameter 


15 to 25 


2-1/4 


2-3/4 


2-1/4 to 2-1/2, incl. 
2-3/4 


1/2x1/4 
3/4 x 3/8 



*AII other 4-, 6-, and 8-pole Hp ratings will have same rotor bores as 2-pole ratings by frame size. 



1 See 18.236. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 77 

MEDIUM SHELL-TYPE MOTORS FOR WOODWORKING AND MACHINE-TOOL APPLICATIONS 

1 8.235.1 .2 Tapered Rotor Bores* 



BH Dimension 



Range of Bore on Big End 



8 
10 

12.375 



1.75 to 2 inches - For all pole combinations 
2.125 to 2.375 inches - For 4, 6, and 8 poles 
2.125 to 2.25 inches - For 2 poles 
2.5 to 2.75 inches - For all pole combinations 



*AII rotor bore dimensions are based on the use of magnetic shaft material. 



The small-end diameter will be whatever comes depending on length of rotor using 1 / 4 inch taper per foot. 

18.235.2 BH and BJ Dimensions in Inches, Open Type Three-Phase 60-Hertz 40°C Continuous, 
208, 220, 440, and 550 Volts 





Horsepower 








BJ Maximum 




2 


4 


Poles 


6 




8 


2 


Poles 
4 


6 and 8 










BH 


= 8-Inch Diameter 








1-1/2 


1 




3/4 






6-3/4 


6-3/4 


6-1/8 


2 


1-1/2 




1 




1/2 


7-1/2 


7-1/8 


6-7/8 


3 


2 




1-1/2 




3/4 


8 


7-5/8 


7-3/8 


5 


3 




2 




1 


9-3/8 


9 


8-3/4 


7-1/2 


5 




3 




1-1/2 


11-1/2 


11-1/8 


10-7/8 


10 












13-1/2 














BH = 


: 10-Inch Diameter 








7-1/2 


5 




3 




2 


9-1/2 


9 


8-5/8 


10 


7-1/2 




5 




3 


11 


10-1/2 


10-1/8 


15 


10 




7-1/2 




5 


12-3/4 


12-1/4 


11-7/8 


20 


15 




10 




7-1/2 


14 1 / 2 


14 


13-5/8 



BH = 12.375-Inch Diameter 



15 
20 
25 



10 
15 
20 



7-1/2 
10 
15 



1/2 

7-1/2 
10 



11 
12-1/4 
13-1/2 



10-3/8 
11-5/8 
12-7/8 



9-7/8 

11-1/8 
12-3/8 



Maximum BK = 



Maximum BJ 



+ 1/4 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 79 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE PUMP APPLICATIONS 



MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE 

PUMP APPLICATIONS 

(These standards were developed jointly with the Hydraulic Institute.) 

18.237 DIMENSION FOR TYPE VP VERTICAL SOLID-SHAFT, SINGLE-PHASE AND POLYPHASE, 
DIRECT CONNECTED SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE 
PUMP APPLICATIONS 1,2 ' 3 ' 4 





AJ** 


AK 




BB Min BD Max 




BF Clearance Hole 


Frame Designations* 




Number 


Size 


143VPand145VP 


9.125 


8.250 




0.19 




10.00 




4 


0.44 


182VPand184VP 


9.125 


8.250 




0.19 




10.00 




4 


0.44 


213VPand215VP 


9.125 


8.250 




0.19 




10.00 




4 


0.44 


254VP and 256VP 


9.125 


8.250 




0.19 




10.00 




4 


0.44 


284VP and 286VP 


9.125 


8.250 




0.19 




10.00 




4 


0.44 


324VP and 326VP 


14.750 


13.500 




0.25 




16.50 




4 


0.69 


364VP and 365VP 


14.750 


13.500 




0.25 




16.50 




4 


0.69 


404VP and 405VP 


14.750 


13.500 




0.25 




16.50 




4 


0.69 


444VP and 445VP 


14.750 


13.500 




0.25 




16.50 




4 


0.69 




U 


VMin 


AHf 






Keyseat 






Frame Designations* 




R 


ESMin 


S 


EU 


143VPand 145VP 


0.8750 


2.75 


2.75 




0.771-0.756 




1.28 


0.190-0.188 


0.6875 


182VPand 184VP 


1.1250 


2.75 


2.75 




0.986-0.971 




1.28 


0.252-0.250 


0.8750 


213VPand215VP 


1.1250 


2.75 


2.75 




0.986-0.971 




1.28 


0.252-0.250 


0.8750 


254VP and 256VP 


1.1250 


2.75 


2.75 




0.986-0.971 




1.28 


0.252-0.250 


0.8750 


284VP and 286VP 


1.1250 


2.75 


2.75 




0.986-0.971 




1.28 


0.252-0.250 


0.8750 


324VP and 326VP 


1.625 


4.50 


4.50 




1.416-1.401 




3.03 


0.377-0.375 


1.2500 


364VP and 365VP 


1.625 


4.50 


4.50 




1.416-1.401 




3.03 


0.377-0.375 


1.2500 


404VP and 405VP 


1.625 


4.50 


4.50 




1.416-1.401 




3.03 


0.377-0.375 


1.2500 


444VP and 445VP 


2.125 


4.50 


4.50 




1.845-1.830 




3.03 


0.502-0.500 


1.7500 



The assignment of horsepower and speed ratings to these frames shall be in accordance with Part 13, except for the inclusion of 

the suffix letter VP in place of the suffix letters T and TS. 

**AJ dimension — centerline of bolt holes shall be within 0.025 inch of true location. True location is defined as angular and 

diametrical location with reference to the centerline of the AK dimension. 

1The tolerance on the AH dimension shall be ±0.06 inch. Dimension AH shall be measured with motor in vertical position, shaft 

down. 



1 The tolerance for the permissible shaft runout shall be 0.002-inch indicator reading (see 4.1 1). 

2 For the meaning of the letter dimensions, see 4.1 and Figure 18-23. 

3 For tolerance on AK dimension, face runout, and permissible eccentricity of mounting rabbet, see 4.13. 

4 For tolerance on shaft extension diameters and keyseats, see 4.9 and 4.10. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 80 DEFINITE PURPOSE MACHINES 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE PUMP APPLICATIONS 




Figure 18-23 
DIMENSIONS FOR MOTORS FOR VERTICAL TURBINE PUMP APPLICATIONS 



All dimensions in inches. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 



MG 1-2009 
Part 18, Page 81 



MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE PUMP 
APPLICATIONS 

18.238 DIMENSIONS FOR TYPE P AND PH ALTERNATING-CURRENT SQUIRREL-CAGE 

VERTICAL HOLLOW-SHAFT MOTORS FOR VERTICAL TURBINE PUMP APPLICATIONS 1 ' 2 

18.238.1 Base Dimensions 



Item* 


Frame 
Designation 


AJ** 


AK 


BBMin 


BDWIax 


Clearance 


BFTap 
Size 


Number 


EOMin 


1 


182TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.50 


2 


184TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.50 


3 


213TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.50 


4 


215TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.50 


5 


254TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.75 


6 


256TP 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.75 


7 


284TPt 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.75 


8 


286TP| 


9.125 


8.250 


0.19 


10.00 


0.44 




4 


2.75 


9 


324TPf 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.00 


10 


326TPf 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.00 


11 


364TPI 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.00 


12 


365TP 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.00 


13 


404TP 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.50 


14 


405TP 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


4.50 


15 


444TP 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


5.00 


16 


445TP 


14.750 


13.500 


0.25 


16.50 


0.69 




4 


5.00 


17 




14.750 


13.500 


0.25 


20.00 


0.69 




4 




18 




14.750 


13.500 


0.25 


24.50 


0.69ft 


5/8-1 1 


4 




19 




26.000 


22.000 


0.25 


30.50 


0-81 ft 


3/4-10 


4 





All dimensions in inches. 

*See 18.238.2 for the coupling dimensions of the motors covered in items 1 through 16. 

tThese frames have the following alternative base dimensions, the coupling dimensions given in 18.238.2 remaining unchanged: 











Base Dimensions 










AJ** 


AK 


BBMin 




BF 






Frame 
Designations 


BD Max Clearance 


Tap Size 


Number 


EOMin 



324TPH 


9.125 


8.250 


0.19 


12.00 


0.44 


326TPH 


9.125 


8.250 


0.19 


12.00 


0.44 


284TPH 


14.750 


13.500 


0.25 


16.50 


0.69 


286TPH 


14.750 


13.500 


0.25 


16.50 


0.69 



4 


4.00 


4 


4.00 


4 


2.75 


4 


2.75 



**AJ dimension— centerline of bolt holes shall be within 0.025 inch of true location. True location is defined as angular and 
diametrical location with reference to the centerline of the AK dimension. 
ttEither clearance hole or up size shall be specified. 



1 For the meaning of the letter dimensions, see 4.1 and Figure 4-5. 

2 For tolerances on AK dimension, face runout, and permissible eccentricity of mounting rabbet, see 4.13. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 82 DEFINITE PURPOSE MACHINES 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR VERTICAL TURBINE PUMP APPLICATIONS 

18.238.2 Coupling Dimensions 1 







Standard Bore 


Coupling Dimensions 


Maximum Bore 






item* 


BX** 


EW 


R 


BY 


BZ 


BX** 


EW 


R 


BY 


BZ 


1 


0.751 


0.188-0.190 


0.837-0.847 


10-32 


1.375 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


2 


0.751 


0.188-0.190 


0.837-0.847 


10-32 


1.375 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


3 


0.751 


0.188-0.190 


0.837-0.847 


10-32 


1.375 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


4 


0.751 


0.188-0.190 


0.837-0.847 


10-32 


1.375 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


5 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


1.251 


0.250-0.252 


1.367-1.377 


1/4-20 


1.750 


6 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


1.251 


0.250-0.252 


1.367-1.377 


1/4-20 


1.750 


7 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


1.251 


0.250-0.252 


1.367-1.377 


1/4-20 


1.750 


8 


1.001 


0.250-0.252 


1.114-1.124 


10-32 


1.375 


1.251 


0.250-0.252 


1.367-1.377 


1/4-20 


1.750 


9 


1.188 


0.250-0.252 


1.304-1.314 


1/4-20 


1.750 


1.501 


0.375-0.377 


1.669-1.679 


1/4-20 


2.125 


10 


1.188 


0.250-0.252 


1.304-1.314 


1/4-20 


1.750 


1.501 


0.375-0.377 


1.669-1.679 


1/4-20 


2.125 


11 


1.188 


0.250-0.252 


1.304-1.314 


1/4-20 


1.750 


1.501 


0.375-0.377 


1.669-1.679 


1/4-20 


2.125 


12 


1.188 


0.250-0.252 


1.304-1.314 


1/4-20 


1.750 


1.501 


0.375-0.377 


1.669-1.679 


1/4-20 


2.125 


13 


1.438 


0.375-0.377 


1.605-1.615 


1/4-20 


2.125 


1.688 


0.375-0.377 


1.859-1.869 


1/4-20 


2.500 


14 


1.438 


0.375-0.377 


1.605-1.615 


1/4-20 


2.125 


1.688 


0.375-0.377 


1.859-1.869 


1/4-20 


2.500 


15 


1.688 


0.375-0.377 


1.859-1.869 


1/4-20 


2.500 


1.938 


0.500-0.502 


2.160-2.170 


1/4-20 


2.500 


16 


1.688 


0.375-0.377 


1.859-1.869 


1/4-20 


2.500 


1.938 


0.500-0.502 


2.160-2.170 


1/4-20 


2.500 



All dimensions in inches 

*See the correspondingly numbered item in 18.238.1 for the frame designation and base dimensions of the motors to which 

these coupling dimensions apply. 

**The tolerance on the BX dimension shall be as follows 

BX dimension-— 1.001 to 1.500 inches, inclusive, +0.001 inch, -0.000 inch 

BX dimension— larger than 1 .500 inches, +0.001 5 inch, -0.000 inch 



1 For the meaning of the letter dimensions, see 4.1 and Figure 4-5. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 83 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR CLOSE-COUPLED PUMPS 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR CLOSE-COUPLED PUMPS 

(A face-mounting close-coupled pump motor is a medium alternating-current squirrel-cage induction open or totally enclosed motor, 
with or without feet, having a shaft suitable for mounting an impeller and sealing device. For explosion proof motors, see Note 3 of 
Figure 18-24.) 

RATINGS 

18.239 VOLTAGE RATINGS 

See 10.30. 

18.240 FREQUENCIES 
See 10.31.1. 

18.241 NAMEPLATE MARKINGS 
See 10.40. 

18.242 NAMEPLATE TIME RATINGS 
See 10.36. 

TESTS AND PERFORMANCE 

1 8.243 TEMPERATURE RISE 
See 12.44. 

18.244 TORQUES 

For single-phase medium motors, see 12.32. 

For polyphase medium motors, see 12.38, 12.39, and 12.40. 

18.245 LOCKED-ROTOR CURRENTS 

For single-phase medium motors, see 12.34. For three-phase medium motors, see 12.35. 

18.246 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.247 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
See 12.44. 

18.248 BALANCE OF MOTORS 
See Part 7. 

MANUFACTURING 

18.249 FRAME ASSIGNMENTS 

Frame assignments shall be in accordance with Part 13, except for the omission of the suffix letters T and 
TS and the inclusion of the suffix letters in accordance with 18.250, (i.e., 254JP). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 1 8, Page 84 DEFINITE PURPOSE MACHINES 

MEDIUM AC SQUIRREL-CAGE INDUCTION MOTORS FOR CLOSE-COUPLED PUMPS 

18.250 DIMENSIONS FOR TYPES JM AND JP ALTERNATING-CURRENT FACE-MOUNTING 
CLOSE-COUPLED PUMP MOTORS HAVING ANTIFRICTION BEARINGS 

(This standard was developed jointly with the Hydraulic Institute.) 
See Figure 18-24. 




15°-20° Exit (Optional) 



ELDii 



EMorU 
±003 0.043R/0.O54R (MaxTol.) 

DUCOia.EMorU-0.050 Dia ' 

Controlled Undercut Design (Detail A) 



143-184 JP and JM 

213-365 JP 
213-326 JM 




0.O43R/O.O54R EM Dia. 
{No Undercut) 



Controlled Comer Radius Design (Detail B) 

143-184 JP and JM 
' 213-365 JP 
" 213-326 JM 




213-365 JP 

213-326 JM 

143-184 JP and JM 



ENclass3R.H. 



Corner Detail Motor Manufacturer's Choice 



FRAMES 213-365 JP 
213-326 JM 



FRAMES 143-184 
JP AND JM 




Figure 18-24 
DIMENSIONS FOR PUMP MOTORS HAVING ANTIFRICTION BEARINGS 

NOTES 

1 — AH, EQ, and ET dimensions measured with the shaft pulled by hand away from the motor to the limit of end play. 

2 — AJ dimension - centerline of bolt holes is within 0.015 inch of true location for frames 143 to 256 JM and JP, inclusive, and 

within 0.025 inch of true location for frames 284 to 365 JM and JP, inclusive. True location is defined as angular and diametrical 

location with reference to the centerline of the AK dimensions. 

3— Shaft end play should not exceed the bearing internal axial movement. Bearing mounting fits should be as recommended for 

pump application by the bearing manufacturer. (This note applies to open and totally enclosed motors. For explosion-proof 

motor, the individual motor manufacturer should be contacted.) 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18 Page 93 

DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 



DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 

(A direct-current permanent-magnet control tachometer generator is a direct-current generator designed to have an output voltage 
proportional to rotor speed for use in open-loop or closed-loop control systems.) 

1 8.253 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Direct-current permanent-magnet excited. 

18.254 CLASSIFICATION ACCORDING TO OUTPUT VOLTAGE RATING 

a. High-voltage type 

b. Low-voltage type 

RATINGS 

18.255 OUTPUT VOLTAGE RATINGS 

The output voltage ratings of high-voltage-type tachometer generators shall be 50, 100, and 200 volts per 
1000 rpm. 

The output voltage rating of low-voltage-type tachometer generators shall be 2, 4, 8, 16, and 32 volts per 
1000 rpm. 

18.256 CURRENT RATING 

The current rating of high-voltage-type tachometer generators shall be 25 milliamperes at the highest rate 
of speed. 

Low-voltage-type tachometer generators do not have a current rating. In general, the load impedance 
should be at least 1000 times the armature resistance. 

18.257 SPEED RATINGS 

The speed range of high-voltage-type tachometer generators shall be 100-5000, 100-3600, 100-2500 
100-1800, and 100-1250 rpm. 

The speed range of low-voltage-type tachometer generators shall be 100-10000, 100-5000, and 100- 
3600 rpm. 

TESTS AND PERFORMANCE 

18.258 TEST METHODS 

Tests to determine performance characteristics shall be made in accordance with IEEE Std 251. 

1 8.259 TEMPERATURE RISE 

Control tachometer generators shall have a Class A insulation system 1 and shall be designed for use in a 
maximum ambient of 65°C. The temperature rise above the temperature of the cooling medium for each 
of the various parts of the generator, when tested in accordance with the rating, shall not exceed the 
following values: 



1 See 1 .66 for description of classes of insulation. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 94 DEFINITE PURPOSE MACHINES 

DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 



High-Voltage Type Low-Voltage Type 

Coil Windings, Degrees C 

Armature - resistance 40 50 

Commutators - thermometer 40 40 

Xh e temperatures attained by cores, commutators, and miscellaneous parts (such as 
brushholders and brushes) shall not injure the insulation or the machine in any respect. 



Abnormal deterioration of insulation may be expected if the ambient temperature stated above is 
exceeded in regular operation. 

18.260 VARIATION FROM RATED OUTPUT VOLTAGE 

18.260.1 High-Voltage Type 

The no-load voltage of individual generators shall be within plus or minus 5 percent of the rated output 
voltage. 

18.260.2 Low-Voltage Type 

The voltage with specified load impedance shall be within plus or minus 5 percent of the rated output 
voltage. 

1 8.261 HIGH-POTENTIAL TESTS 

18.261.1 Test 

See 3.1. 

18.261.2 Application 

The high-potential test shall be made by applying 1000 volts plus twice the rated voltage of the 
tachometer generator. Rated voltage shall be determined by using the tachometer generator rated 
voltage at maximum rated speed. 

18.262 OVERSPEED 

Control tachometer generators shall be so constructed that, in an emergency, they will withstand without 
mechanical injury a speed of 125 percent of the maximum rated speed. 

This overspeed may damage the commutator and brush surfaces with a resulting temporary change in 
performance characteristics. 

18.263 PERFORMANCE CHARACTERISTICS 

The following typical performance data shall be available for each control tachometer generator. Data will 
normally be supplied in tabulated form. 

18.263.1 High-Voltage Type 

a. Peak-to-peak or root mean square ripple voltage data, as specified, expressed as a percentage of 
output voltage over the rated speed range and at one or more load impedances 

b. Linearity data as a percentage of output voltage over the rated speed range at no-load and at one 
or more load impedances 

c. Reversing error data as a percentage of output voltage over the rated speed range at no-load 

d. Short-time voltage stability data at constant speed and load impedance in percent of average 
voltage 

e. Long-time voltage stability data at constant speed and load impedance in percent voltage change 
per hour 

f. Rotor resistance between bars of opposite polarity corrected to 25°C 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 95 

DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 

g. Standstill (break-away) and maximum running torque in ounce-feet or ounce-inches 
h. Wk 2 of rotor in lb-in. 2 
i. Total weight of generator 

18.263.2 Low-Voltage Type 

a Peak-to-peak or root mean square ripple voltage data, as specified, expressed as a percentage 
of output voltage over the rated speed range and at one or more load impedances 

b. Linearity data as a percentage of output voltage over the rated speed range at no-load and at one 
or more load impedances 

c Reversing error data as a percentage of output voltage over the rated speed at no load 

d. Rotor resistance between bars of opposite polarity corrected to 25°C 



e. Wk 2 of rotor in oz-in. 2 



18.264 NAMEPLATE MARKING 



MANUFACTURING 



The following information shall be given on all nameplates. For abbreviations see 1.79. For some 
examples of additional information that may be included on the nameplate see 170.2. 

18.264.1 High-Voltage Type 

a. Manufacturer's name or identification symbol 

b. Manufacturer's type designation 

c. Manufacturer's serial number or date code 

d. Electrical type 1 

e. Voltage rating - volts per 1 000 rpm 

f. Speed range 

g. Maximum ambient temperature 1 

h. Calibration voltage — no-load test voltage and speed 1 

18.264.2 Low-Voltage Type 

a. Manufacturer's name or identification symbol 

b. Manufacturer's type designation 

c. Voltage rating— volts per 1000 rpm 

18.265 DIRECTION OF ROTATION 

The standard direction of rotation shall be clockwise facing the end opposite the drive end. 

Tachometer generators may be operated on a reversing cycle provided that the period of operation on 
any one direction of rotation is no longer than 1 hour and a reasonable balance of time on each direction 
is maintained. Unequal operating time in both directions may result in uneven brush wear which can 
cause different output voltages, ripple content, and reversing error data. For such an application 
condition, the tachometer generator manufacturer should be consulted. 

18.266 GENERAL MECHANICAL FEATURES 

Control tachometer generators shall be constructed with the following mechanical features: 



1 On small units where nameplate size is such that it is impractical to mark all data, items d, f, g, and h shall be permitted to be on a 
separate card or tag. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 96 DEFINITE PURPOSE MACHINES 

DC PERMANENT-MAGNET TACHOMETER GENERATORS FOR CONTROL SYSTEMS 



18.266.1 High-Voltage Type 

a. Totally enclosed 

b. Ball bearing 

c. Generators built in frame 42 and larger shall have dimensions according to 4.5.1 or 4.5.5. 

d. Generators built in frame 42 and larger shall have provisions for 1/2-inch conduit connection. 

18.266.2 Low-Voltage Type 

a. Open or totally enclosed 

b. Ball bearing 

18.267 TERMINAL MARKINGS 

For clockwise rotation facing the en6 opposite the drive end, the positive terminal shall be marked "A- 
2" or colored red and the negative terminal shall be marked "A-1" or colored black. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II MG 1-2009 

DEFINITE PURPOSE MACHINES Part 18, Page 97 

TORQUE MOTORS 

TORQUE MOTORS 

18.268 DEFINITION 

A torque motor is a motor rated for operation at standstill. 

1 8.269 NAMEPLATE MARKINGS 

18.269.1 AC Torque Motors 

The following information shall be given on all nameplates. For abbreviations see 1.79. For some 
examples of additional information that may be included on the nameplate see 1.70.2. 

| a. Manufacturer's type and frame designation 

b. Locked rotor torque 

c. Time rating 

d. Maximum ambient temperature for which motor is designed 

e. Insulation system designation (if stator and rotor use different classes of insulation systems, both 
insulation system designations shall be given on the nameplate, that for the stator being given 
first) 

f. Synchronous rpm 

g. Frequency 
h. Number of phases 
i. Rated load amperes (locked rotor) 
j. Voltage 
k. The words "thermally protected" for motors equipped with thermal protectors 1 

18.269.2 DC Torque Motors 

The following information shall be given on all nameplates. For abbreviations see 1.79. For some 
examples of additional information that may be included on the nameplate see 1.70.2. 

a. Manufacturer's type and frame designation 

b. Locked rotor torque 

c. Time rating 

d. Temperature rise 

e. Voltage 

f. Rated-load amperes (locked rotor) 

g. Type of winding 
h. The words "thermally protected" for motors equipped with thermal protectors 1 



1 Thermal protection shall be permitted to be indicated on a separate plate. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18, Page 98 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR CARBONATOR PUMPS 

SMALL MOTORS FOR CARBONATOR PUMPS 

18.270 CLASSIFICATION ACCORDING TO ELECTRICAL TYPE 

Single-phase — Split-phase 

RATINGS 

18.271 VOLTAGE RATINGS 

The voltage rating of single-phase 60-hertz motors shall be 1 1 5 or 230 volts. 

18.272 FREQUENCIES 
Frequencies shall be 60 and 50 hertz. 

18.273 HORSEPOWER AND SPEED RATINGS 

18.273.1 Horsepower Ratings 

Horsepower ratings shall be 1/6, 1/4, and 1/3 horsepower. 

18.273.2 Speed Ratings 

Speed ratings shall be: 

a. 60 hertz - 1800 rpm synchronous speed, 1725 rpm approximate full-load speed 

b. 50 hertz - 1500 rpm synchronous speed, 1425 rpm approximate full-load speed 

TESTS AND PERFORMANCE 

1 8.274 TEMPERATURE RISE 

Carbonator pump motors shall have either Class A or B insulation systems. The temperature rise above 
the temperature of the cooling medium shall be in accordance with 12.43. 

18.275 BASIS OF HORSEPOWER RATING 

For single-phase induction motors, see 10.34. 

18.276 HIGH-POTENTIAL TEST 
See 3.1 and 12.3. 

18.277 MAXIMUM LOCKED-ROTOR CURRENT— SINGLE PHASE 
See the values for Design O motors in 12.33. 

18.278 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 
See 12.44. 

18.279 DIRECTION OF ROTATION 

Motors for carbonator pumps shall normally be arranged for counterclockwise rotation when facing the 
end opposite the drive end but shall be capable of operation in either direction. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section II 

DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR CARBONATOR PUMPS 



MG 1-2009 
Part 18, Page 99 



MANUFACTURING 

18.280 GENERAL MECHANICAL FEATURE 

Carbonator-pump motors shall be constructed with the following mechanical features: (see 18.281) 

a. Open ordripproof 

b. Sleeve bearing 

c. Resilient mounting 

d. Automatic reset thermal overload protector 

e. Mounting dimensions and shaft extension in accordance with 18.281 

1 8.281 DIMENSIONS FOR CARBONATOR PUMP MOTORS 

See Figure 18-27. 



TO FACE OF BRG. CAP. 




FACE OF HUB TO BE PER- 
PENDICULAR TO C/L OF 
SHAFT WITHIN 0.004 T.I.R. 

0.09 DIA. HOLE 

CENTERED IN BOTTOM 

UNDERCUT 



Allowable Out of Parallel of Slot in Shaft 

0.004 T.I.R. and Shall Be Central Within 

0.004 T.I.R. (DEPTH 

•This Diameter of Hub to Be Concentric OF SLOT) 52 MIN 

Within 0.004 T.I.R. 






-0.135 MIN. 
h*- 0.140 MIN. (END OF SHAFT TO END OF HUB) 



Figure 18-27 
CARBONATOR PUMP MOTOR DIMENSIONS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section II 

Part 18 Page 100 DEFINITE PURPOSE MACHINES 

SMALL MOTORS FOR CARBONATOR PUMPS 



This page is intentionally left blank. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 20 



<This page is intentionally left blank.> 



Section III 

LARGE MACHINES— INDUCTION MACHINES 



MG 1-2009 
Part 20, Page 1 



Section III 

LARGE MACHINES 

Part 20 

LARGE MACHINES— INDUCTION MACHINES 



20.1 



SCOPE 



The standards in this Part 20 of Section III cover induction machines having (1) a continuous rating 
greater than given in the table below and (2) all ratings of 450 rpm and slower speeds. 



Synchronous Speed 


Motors, Squirrel-Cage 
Wound-Rotor, Hp 


and 


Generators, 


Squirrel-Cage kW 


3600 




500 








400 


1800 




500 








400 


1200 




350 








300 


900 




250 








200 


720 




200 








150 


600 




150 








125 


514 




125 








100 



20.2 



BASIS OF RATING 



Induction machines covered by this Part 20 shall be rated on a continuous-duty basis unless otherwise 
specified. The output rating of induction motors shall be expressed in horsepower available at the shaft at 
a specified speed, frequency, and voltage. 

The output rating of induction generators shall be expressed in kilowatts available at the terminals at a 
specified speed, frequency, and voltage. 

20.3 MACHINE POWER AND SPEED RATINGS 

Motor horsepower ratings shall be as follows: 



Motor Hp Ratings 


100 


600 


2500 


9000 


19000 


125 


700 


3000 


10000 


20000 


150 


800 


3500 


11000 


22500 


200 


900 


4000 


12000 


25000 


250 


1000 


4500 


13000 


27500 


300 


1250 


5000 


14000 


30000 


350 


1500 


5500 


15000 


35000 


400 


1750 


6000 


16000 


40000 


450 


2000 


7000 


17000 


45000 


500 


2250 


8000 


18000 


50000 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 














Se 


Part 20, Page 2 










LARGE MACHINES- 


-INDUCTION MAC 


Generator output ratings 


shall be as 


follows: 
















Generator kW Ratings 






75 




450 




1750 


5500 


14000 


27500 


100 




500 




2000 


6000 


15000 


30000 


125 




600 




2250 


7000 


16000 


32500 


150 




700 




2500 


8000 


17000 


35000 


200 




800 




3000 


9000 


18000 


37500 


250 




900 




3500 


10000 


19000 


40000 


300 




1000 




4000 


11000 


20000 


45000 


350 




1250 




4500 


12000 


22500 


50000 


400 




1500 




5000 


13000 


25000 




Synchronous speed ratings 


shall be 


as 


follows: 








Synchronous Speed Ratings, Rpm at 60 Hertz* 


3600 








720 


400 




277 


1800 








600 


360 




257 


1200 








514 


327 




240 


900 








450 


300 




225 



*At 50 hertz, the speeds are 5/6 of the 60-hertz speeds. 

NOTE— It is not practical to build induction machines of all ratings at all speeds. 

20.4 POWER RATINGS OF MULTISPEED MACHINES 

The power ratings of multispeed machines shall be selected as follows: 

20.4.1 Constant Power 

The horsepower or kilowatt rating for each rated speed shall be selected from 20.3. 

20.4.2 Constant Torque 

The horsepower or kilowatt rating for the highest rated speed shall be selected from 20.3. The 
horsepower or kilowatt rating for each lower speed shall be determined by multiplying the horsepower or 
kilowatt rating at the highest speed by the ratio of the lower synchronous speed to the highest 
synchronous speed. 

20.4.3 Variable Torque 

20.4.3.1 Variable Torque Linear 

Torque varies directly with speed and the horsepower or kilowatt rating for the highest rated speed shall 
be selected from 20.3. The horsepower or kilowatt rating for each lower speed shall be determined by 
multiplying the horsepower or kilowatt rating at the highest speed by the square of the ratio of the lower 
synchronous speed to the highest synchronous speed. 

20.4.3.2 Variable Torque Square 

The torque varies as the square of speed and the horsepower or kilowatt rating for the highest rated 
speed shall be selected from 20.3. The horsepower or kilowatt rating for each lower speed shall be 
determined by multiplying the horsepower or kilowatt rating at the highest speed by the cube of the ratio 
of the lower synchronous speed to the highest synchronous speed. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— INDUCTION MACHINES 



20.5 VOLTAGE RATINGS 
20.5.1 Voltage Ratings 



MG 1-2009 
Part 20, Page 3 



For three phase ac machines, 50 Hz or 60 Hz, intended to be directly connected to distribution or 
utilization systems, the rated voltages shall be selected from the voltages given in following table. Other 
voltages are subject to the approval between manufacturer and purchaser. 



Nominal System voltages 
for 50 Hz* 



_aL 



400 



*L 



400 



3300 



3000 



6600 



6000 



11000 



10000 



Nominal System voltages 

for 60 Hz 



480 



600 



2400 



4160 



6900 



13800 



Preferred motor rated 

voltages for 60 Hz (North 

American Practice) 



460 



575 



2300 



4000 



6600 



13200 



* Either one of the voltage series a) or b) is used in certain countries for 50 Hz. 
NOTE— Induction generators shall have the nominal system voltage ratings as shown 

20.5.2 Preferred Machine Power and Voltage Rating 

It is not practical to build induction machines of all ratings for all voltages. In general, based on motor 
design and manufacturing considerations, preferred motor voltage ratings are as follows: 

a) 60 HZ power supply: 



Horsepower 



100-600 



200-5000 



200-10000 



1000-15000 



[ 



3500 and up 



KW 



75-500 



150-3500 



150-7000 



800-10000 



2500 and up 



Voltage Rating 



460 or 575 



2300 



4000 



6600 



13200 



b) 50 HZ power supply: 



Horsepower 


KW 


Voltage Rating 


100-500 


75-375 


400 


600-8000 


500-6000 


3000 - 3300 


700-15000 


500-12500 


6000 - 6600 


3000 and up 


2500 and up 


10000-11000 



20.6 FREQUENCIES 

The frequencies shall be 50 or 60 hertz. 

20.7 SERVICE FACTOR 
20.7.1 Service Factor of 1 .0 

When operated at rated voltage and frequency, induction machines covered by this Part 20 will have a 
service factor of 1 .0 and a temperature rise not in excess of that specified in 20.8.1 . 

In those applications requiring an overload capacity, the use of a higher rating is recommended to avoid 
exceeding the adequate torque handling capacity. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 20, Page 4 LARGE MACHINES— INDUCTION MACHINES 

20.7.2 Service Factor of 1 .1 5 

When specified, motors furnished in accordance with this standard will have a service factor of 1.15 and a 
temperature rise not in excess of that specified in 20.8.2 when operated at the service factor horsepower 
rating with rated voltage and frequency maintained. 

20.7.3 Application of Motors with a Service Factor of 1.15 

20.7.3.1 General 

A motor having a 1 .15 service factor is suitable for continuous operation at rated load under the usual 
service conditions given in 20.28.2. When the voltage and frequency are maintained at the value on the 
nameplate, the motor may be overloaded up to the horsepower obtained by multiplying the rated 
horsepower by the service factor shown on the nameplate. When the motor is operated at a 1 .15 service 
factor, it may have efficiency, power factor and speed values different from those at rated load. 

I NOTE— The percent values of locked-rotor current, locked-rotor torque, and breakdown torque are based on the rated 
horsepower. Motors operating in the service factor range may not have the torque margin during acceleration as stated in 20.9. 

20.7.3.2 Temperature Rise 

When operated at the 1.15-service-factor-load, the motor will have a temperature rise not in excess of 
that specified in 20.8.2 with rated voltage and frequency maintained. No temperature rise is specified or 
implied for operation at rated load. 

Operation at the temperature-rise values given in 20.8.2 for a 1.15-service-factor load causes the motor 
insulation to age thermally at approximately twice the rate that occurs at the temperature-rise value given 
in 20.8.1 for a motor with a 1 .0 service-factor load; that is, operating 1 hour at specified 1.15 service 
factor temperature-rise values is approximately equivalent to operating 2 hours at the temperature-rise 
values specified for a motor with a 1 .0 service factor. 

NOTE— The tables in 20.8.1 and 20.8.2 apply individually to a particular motor rating (that is, a 1.0 or 1.15 service factor), and it 
is not intended or implied that they be applied as a dual rating to an individual motor. 



TESTS AND PERFORMANCE 



20.8 TEMPERATURE RISE 



The observable temperature rise under rated-load conditions of each of the various parts of the induction 
machine, above the temperature of the cooling air, shall not exceed the values given in the following 
tables. The temperature of the cooling air (see exception in 20.8.3) is the temperature of the external air 
as it enters the ventilating openings of the machine, and the temperature rises given in the tables are 
based on a maximum temperature of 40°C for this external air. Temperatures shall be determined in 
accordance with IEEE Std 112. 

20.8.1 Machines with a 1 .0 Service Factor at Rated Load 



Temperature Rise, Degrees C 

Class of Insulation System 

Method of 
Temperature 

Item Machine Part Determination A B F H_ 

a Insulated windings 

1 . All horsepower (kW) ratings 

2. 1 500 horsepower and less 

3. Over 1500 horsepower (11 20 kW) 

a) 7000 volts and less 

b) Over 7000 volts 
b The temperatures attained by cores, squirrel-cage windings, collector rings, and miscellaneous parts (such as 

brushholders and brushes, etc.) shall not injure the insulation or the machine in any respect. 



Resistance 


60 


80 


105 


125 


Embedded detector* 


70 


90 


115 


140 


Embedded detector* 


65 


85 


110 


135 


Embedded detector* 


60 


80 


105 


125 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 5 

'Embedded detectors are located within the slot of the machine and can be either resistance elements or thermocouples. For 
machines equipped with embedded detectors, this method shall be used to demonstrate conformity with the standard. (See 20.27.) 

20.8.2 Machines with a 1.15 Service Factor at Service Factor Load 







Method of 




Temperature Rise 


>, Degrees C 






Class of Insulation System 










Item 


Machine Part 


Temperature 
Determination 


A 


B 


F H 


a 


Insulated windings 












1 . All horsepower (kW) ratings 


Resistance 


70 


90 


115 135 




2. 1500 horsepower and less 


Embedded detector* 


80 


100 


125 150 




3. Over 1500 horsepower (1120 kW) 












a) 7000 volts and less 


Embedded detector* 


75 


95 


120 145 




b) Over 7000 volts 


Embedded detector* 


70 


90 


115 135 


b 


The temperatures attained by cores, squirrel-cage windings, collector rings, and miscellaneous parts (such as 
brushholders and brushes, etc.) shall not injure the insulation or the machine in any respect. 



*Embedded detectors are located within the slot of the machine and can be either resistance elements or thermocouples. For 
machines equipped with embedded detectors, this method shall be used to demonstrate conformity with the standard. (See 20.27.) 



20.8.3 Temperature Rise for Ambients Higher than 40°C 

The temperature rises given in 20.8.1 and 20.8.2 are based upon a reference ambient temperature of 
40°C. However, it is recognized that induction machines may be required to operate in an ambient 
temperature higher than 40°C. For successful operation of induction machines in ambient temperatures 
higher than 40°C, the temperature rises of the machines given in 20.8.1 and 20.8.2 shall be reduced by 
the number of degrees that the ambient temperature exceeds 40°C. 

(Exception — for totally enclosed water-air-cooled machines, the temperature of the cooling air is the 
temperature of the air leaving the coolers. Totally enclosed water-air-cooled machines are normally 
designed for the maximum cooling water temperature encountered at the location where each machine is 
to be installed. With a cooling water temperature not exceeding that for which the machine is designed: 

a. On machines designed for cooling water temperature of 5°C to 30°C-the temperature of the air 
leaving the coolers shall not exceed 40°C. 

b. On machines designed for higher cooling water temperatures — the temperature of the air leaving 
the coolers shall be permitted to exceed 40°C provided the temperature rises for the machine 
parts are then limited to values less than those given in 20.8.1 and 20.8.2 by the number of 
degrees that the temperature of the air leaving the coolers exceeds 40°C.) 

20.8.4 Temperature Rise for Altitudes Greater than 3300 Feet (1000 Meters) 

For machines which operate under prevailing barometric pressure and which are designed not to exceed 
the specified temperature rise at altitudes from 3300 feet (1000 meters) to 13200 feet (4000 meters), the 
temperature rises, as checked by tests at low altitudes, shall be less than those listed in 20.8.1 and 
20.8.2 by 1 percent of the specified temperature rise for each 330 feet (100 meters) of altitude in excess 
of 3300 feet (1000 meters). 

20.8.5 Temperature Rise for Air-Cooled Machines for Ambients Lower than 40° C, 
but Not Below 0°C* 

The temperature rises given in 20.8.1 and 20.8.2 are based upon a reference ambient temperature of 
40°C to cover most general environments. However, it is recognized that air-cooled induction machines 
may be operated in environments where the ambient temperature of the cooling air will always be less 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 20, Page 6 



Section III 
LARGE MACHINES— INDUCTION MACHINES 



than 40°C. When an air-cooled induction machine is marked with a maximum ambient less than 40°C 
then the allowable temperature rises in 20.8.1 and 20.8.2 shall be increased according to the following: 

a) For machines for which the difference between the Reference Temperature and the sum of 40°C 
and the Temperature Rise Limit given in 20.8.1 and 20.8.2 is less than or equal to 5°C then the 
temperature rises given in 20.8.1 and 20.8.2 shall be increased by the amount of the difference between 
40°C and the lower marked ambient temperature. 

b) For machines for which the difference between the Reference Temperature and the sum of 40°C 
and the Temperature Rise Limit given in 20.8.1 and 20.8.2 is greater than 5°C then the temperature rises 
given in 20.8.1 and 20.8.2 shall be increased by the amount calculated from the following expression: 

Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 

1 Where: 





Class of Insulation System 


A 


B 


F 


H 


Reference Temperature for 20.8.1 , 
Degrees C 

Reference Temperature for 20.8.2, 
Degrees C 


105 
115 


130 
140 


155 
165 


180 
190 



*NOTE— This requirement does not include water-cooled machines. 

Temperature Rise Limit = maximum allowable temperature rise according to 20.8.1 and 20.8.2 

For example: A 1.0 service factor rated motor with a Class F insulation system and using resistance as 
the method of determining the rated temperature rise is marked for use in an ambient with a maximum 
temperature of 25°C. From the Table above the Reference Temperature is 1 55°C and from 20.8.1 the 
Temperature Rise Limit is 105°C. The allowable Increase in Rise to be added to the Temperature Rise 
Limit is then: 



Increase in Rise 



^4 Q °C-25 clxL f550C -( 4QOc + ^ 5 ° C ) l 
1 j ll 80°C |J 



13° C 



The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then equal 
to the sum of the Temperature Rise Limit from 20.8.1 and the calculated Increase in Rise. For this 
example that total is 1 05°C + 13°C = 1 1 8°C. 

20.9 CODE LETTERS (FOR LOCKED-ROTOR KVA) 

The code letter designations for locked-rotor kVA per horsepower as measured at full voltage and rated 
frequency are as follows: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— INDUCTION MACHINES 



MG 1-2009 
Part 20, Page 7 



Letter Designation 


kVA 


per Horsepower* 


Letter Designation 


kVA 


per Horsepower* 


A 




0-3.15 


K 




8.0-9.0 


B 




3.15-3.55 


L 




9.0-10.0 


C 




3.55-4.0 


M 




10.0-11 2 


D 




4.0-4.5 


N 




11.2-12.5 


E 




4.5-5.0 


P 




12.5-14.0 


F 




5.0-5.6 


R 




14.0-16.0 


G 




5.6-6.3 


S 




16.0-18.0 


H 




6.3-7.1 


T 




18.0-20.0 


J 




7.1-8.0 


U 




20.0-22.4 








V 




22.4-and up 



*Locked kVA per horsepower range includes the lower figure up to, but not including, the higher figure. 
For example, 3.14 is designated by letter A and 3.15 by letter B. 

20.9.1 Multispeed motors shall be marked with the code letter designating the locked-rotor kVA per 
horsepower for the highest speed at which the motor can be started, except constant-horsepower motors 
which shall be marked with the code letter for the speed giving the highest locked-rotor kVA per 
horsepower. 

20.9.2 Single-speed motors starting on Y connection and running on delta connection shall be marked 
with a code letter corresponding to the locked-rotor kVA per horsepower for the Y connection. 

20.9.3 Broad- or dual-voltage motors which have a different locked-rotor kVA per horsepower on the 
different voltages shall be marked with the code letter for the voltage giving the highest locked-rotor kVA 
per horsepower. 

20.9.4 Motors with 60- and 50-hertz ratings shall be marked with a code letter designating the locked- 
rotor kVA per horsepower on 60 Hertz. 

20.9.5 Part-winding-start motors shall be marked with a code letter designating the locked-rotor kVA per 
horsepower that is based upon the locked-rotor current for the full winding of the motor. 

20.10 TORQUE 

20.10.1 Standard Torque 

The torques, with rated voltage and frequency applied, shall be not less than the following: 



Torques 


Percent of Rated Full-Load Torque 


Locked-rotor* 


60 


Pull-up* 


60 


Breakdown* 


175 


Pushover** 


175 



*Applies to squirrel-cage induction motors or induction generators when 
specified for self-starting 

** Applies to squirrel-cage induction generators 

In addition, the developed torque at any speed up to that at which breakdown occurs, with starting 
conditions as specified in 20.14.2, shall be higher than the torque obtained from a curve that varies as the 
square of the speed and is equal to 100 percent of rated full-load torque at rated speed by at least 10 
percent of the rated full-load torque. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 20, Page 8 



Section III 
LARGE MACHINES— INDUCTION MACHINES 



20.10.2 High Torque 

When specified, the torques with rated voltage and frequency applied, shall not be less than the following: 



Torques 


Percent of Rated Full-load Torque 


Locked-rotor 


200 


Pull-up 


150 


Breakdown 


190 



In addition, the developed torque at any speed up to that at which breakdown occurs, with starting 
conditions as specified in 20.14.2, shall be higher than the torque obtained from a curve that has a 
constant 100 percent of rated full-load torque from zero speed to rated speed, by at least 10 percent of 
the rated full-load torque. 

20.10.3 Motor Torques When Customer Specifies A Custom Load Curve 

When the customer specifies a load curve, the torques may be lower than those specified in 20.10.1 
provided the motor developed torque exceeds the load torque by a minimum of 10% of the rated full-load 
torque at any speed up to that at which breakdown occurs, with starting conditions as specified by the 
customer ( refer to 20.14.2.3 ). 

A torque margin of lower than 10% is subject to individual agreement between the motor manufacturer 
and user. 

20.10.4 Motor With 4.5 pu and Lower Locked-Rotor Current 

The limit for breakdown torque given in 20.10.1 shall not apply for motors requiring locked-rotor current of 
4.5 pu or lower. Instead the breakdown torque shall not be less than 150% of rated full-load torque for 
such machines. 

20.11 LOAD WK 2 FOR POLYPHASE SQUIRREL-CAGE INDUCTION MOTORS 

Table 20-1 lists load Wk 2 which polyphase squirrel-cage motors having performance characteristics in 
accordance with this Part 20 can accelerate without injurious temperature rise provided that the 
connected load has a speed torque characteristic according to 20.10.1. For torque-speed characteristics 
according to 20.10.2 maximum load Wk 2 shall be 50 percent of the values listed in Table 20-1. 

The values of Wk 2 of connected load given in Table 20-1 were calculated from the following formula 1 : 



Load Wk' 



Hp 095 


1 

0.0685 

J 


1 
Hp 15 


[-1000 J 


[1000 J j 



Where: 



A = 24 for 300 to 1800 rpm, inclusive, motors 
A = 27 for 3600 rpm motors 



1 This formula may not be applicable to ratings not in Table 20-1 . Consult the manufacturer for the 
ratings that are not shown. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 9 

20.12 NUMBER OF STARTS 

20.12.1 Starting Capability 

Squirrel-cage induction motors (or induction generators specified to start and accelerate a connected 
load) shall be capable of making the following starts, providing the Wk 2 of the load, the load torque during 
acceleration, the applied voltage, and the method of starting are those for which the motor was designed. 

a. Two starts in succession, coasting to rest between starts, with the motor initially at ambient 
temperature. 

b. One start with the motor initially at a temperature not exceeding its rated load operating 
temperature. 

20.12.2 Additional Starts 

If additional starts are required, it is recommended that none be made until all conditions affecting 
operation have been thoroughly investigated and the apparatus has been examined for evidence of 
excessive heating. It should be recognized that the number of starts should be kept to a minimum since 
the life of the motor is affected by the number of starts. 

20.12.3 Information Plate 

When requested by the purchaser, a separate starting information plate should be supplied on the motor. 

20.13 OVERSPEEDS 

Squirrel-cage and wound-rotor induction machines shall be so constructed that, in an emergency not to 
exceed 2 minutes, they will withstand without mechanical injury overspeeds above synchronous speed in 
accordance with the following table. During this overspeed condition the machine is not electrically 
connected to the supply. 



Overspeed, Percent of 
Synchronous Sped, Rpm Synchronous Speed 

1801 and over 20 

1800 and below 25 



> Copyright 2009 by the National Electrical Manufacturers Association. 



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Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 1 1 

20.14 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

20.14.1 Running 

Induction machines shall operate successfully under running conditions at rated load with a variation in 
the voltage or the frequency up to the following: 

a. Plus or minus 10 percent of rated voltage, with rated frequency 

b. Plus or minus 5 percent of rated frequency, with rated voltage 

c. A combined variation in voltage and frequency of 10 percent (sum of absolute values) of the rated 
values, provided the frequency variation does not exceed plus or minus 5 percent of rated 
frequency. 

Performance within these voltage and frequency variations will not necessarily be in accordance with the 
standards established for operation at rated voltage and frequency. 

20.14.2 Starting 

20.14.2.1 Standard 

Induction machines shall start and accelerate to running speed a load which has a torque characteristic 
not exceeding that listed in 20.10 and an inertia value not exceeding that listed in 20.1 1 with the voltage 
and frequency variations specified in 20.14.1. 

20.14.2.2 Low Voltage Option 

When low voltage starting is specified, induction machines shall start and accelerate to running speed a 
load which has a torque characteristic not exceeding that listed in 20.10 and an inertia value not 
exceeding that listed in 20.1 1 with the following voltage and frequency variations: 

a. -1 5 percent of rated voltage with rated frequency 

b. ±5 percent of rated frequency, with rated voltage 

c. A combined variation in voltage and frequency of 1 5 percent (sum of absolute values) of the rated 
values, provided the frequency variation does not exceed ±5 percent of rated frequency. 

20.14.2.3 Other 

For loads with other characteristics, the starting voltage and frequency limits may be different. The 
limiting values of voltage and frequency under which an induction machine will successfully start and 
accelerate to running speed depend on the margin between the speed-torque curve of the induction 
machine at rated voltage and frequency and the speed-torque curve of the toad under starting conditions. 
Since the torque developed by the induction machine at any speed is approximately proportional to the 
square of the voltage and inversely proportional to the square of the frequency it is generally desirable to 
determine what voltage and frequency variations will actually occur at each installation, taking into 
account any voltage drop resulting from the starting current drawn by the machine. This information and 
the torque requirements of the driven (or driving) machine define the machine speed-torque curve, at 
rated voltage and frequency, which is adequate for the application. 

20.15 OPERATION OF INDUCTION MACHINES FROM VARIABLE-FREQUENCY OR VARIABLE- 
VOLTAGE POWER SUPPLIES, OR BOTH 

Induction machines to be operated from solid-state or other types of variable-frequency or variable- 
voltage power supplies, or both, for adjustable-speed applications may require individual consideration to 
provide satisfactory performance. Especially for operation below rated speed, it may be necessary to 
reduce the machine rating to avoid overheating. The induction machine manufacturer should be 
consulted before selecting a machine for such applications. 



) Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 20, Page 12 LARGE MACHINES— INDUCTION MACHINES 



20.16 TESTS 

20.16.1 Test Methods 

The method of testing polyphase induction machines shall be in accordance with the following: 

a. IEEE Std 112 

b. All tests shall be made by the manufacturer. (The order of listing does not necessarily indicate the 
sequence in which the tests shall be made.) 

c. Multispeed machines shall be tested at each speed. 

20.16.2 Routine Tests on Machines Completely Assembled in Factory 

The following tests shall be made on machines completely assembled in the factory and furnished with 
shaft and complete set of bearings: 

a. Measurement of winding resistance 

b. No-load motoring readings of current, power, and speed at rated voltage and frequency. On 50- 
hertz machines, these readings shall be permitted to be taken at 60 hertz. 

c. Measurement of open-circuit voltage ratio on wound-rotor machines 

d. High-potential test in accordance with 20.17. 

20.16.3 Routine Tests on Machines Not Completely Assembled in Factory 

The following factory tests shall be made on all machines not completely assembled in the factory: 

a. Measurement of winding resistance 

b. High-potential test in accordance with 20.17 

20.1 7 HIGH-POTENTIAL TESTS 

20.17.1 Safety Precautions and Test Procedure 

See 3.1. 

20.17.2 Test Voltage— Primary Windings 

The test voltage shall be an alternating voltage whose effective value is 1000 volts plus twice the rated 
voltage of the machine. 1 

20.17.3 Test Voltage— Secondary Windings of Wound Rotors 

The test voltage shall be an alternating voltage whose effective value is 1000 volts plus twice the 
maximum voltage which will appear between slip rings on open-circuit with rated voltage on the primary 
and with the rotor either at standstill or at any speed and direction of rotation (with respect to the rotating 
magnetic field) required by the application for which the machine was designed. 1 



A direct instead of an alternating voltage is sometimes used for high-potential test on primary windings of machines rated 6000 
volts or higher. In such cases, a test voltage equal to 1 .7 times the alternating-current test voltage (effective value) as given in 
20.17.2 and 20.17.3 is recommended. Following a direct-voltage high-potential test, the tested winding should be thoroughly 
grounded. The insulation rating of the winding and the test level of the voltage applied determine the period of time required to 
dissipate the charge and, in many cases, the ground should be maintained several hours to dissipate the charge to avoid hazard to 
personnel. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 13 



20.18 MACHINE WITH SEALED WINDINGS— CONFORMANCE TESTS 

An alternating-current squirrel-cage machine with sealed windings shall be capable of passing the 
following tests: 

20.18.1 Test for Stator Which Can Be Submerged 

After the stator winding is completed, join all leads together leaving enough length to avoid creepage to 
terminals and perform the following tests in the sequence indicated: 

a. The sealed stator shall be tested while all insulated parts are submerged in a tank of water 
containing a wetting agent. The wetting agent shall be non-ionic and shall be added in a 
proportion sufficient to reduce the surface tension of water to a value of 31 dyn/cm (31 x 10 3 
MN/m)orlessat25 C. 

b. Using 500 volts direct-current, take a 10-minute insulation resistance measurement following the 
procedure as outlined in IEEE Std 43. The minimum insulation resistance in megohms shall be > 
5 times the machine rated kilovolts plus 5. 

c. Subject the winding to a 60-hertz high-potential test of 1 . 1 5 times the rated line-to-line rms voltage 
for 1 minute. Water must be at ground potential during this test. 

Id. Using 500 volts direct-current, take a 1 minute insulation resistance measurement following the 
procedure as outlined in IEEE Std 43. The minimum insulation resistance in megohms shall 
be > 5 times the machine rated kilovolts plus 5. 

e. Remove winding from water, rinse if necessary, dry, and apply other tests as may be required. 

20.18.2 Test for Stator Which Cannot Be Submerged 

When the wound stator, because of its size or for some other reason, cannot be submerged, the tests 
shall be performed as follows: 

a. Spray windings thoroughly for one-half hour with water containing a wetting agent. The wetting 
agent shall be non-ionic and shall be added in a proportion sufficient to reduce the surface tension 
of water to a value of 31 dyn/cm (31 x 1 3 pN/m) or less at 25°C. 

b. Using 500 volts direct-current, take a 10-minute insulation resistance measurement following the 
procedure as outlined in IEEE 43. The minimum insulation resistance in megohms shall be > 5 
times the machine rated kilovolts plus 5. 

c. Subject the winding to a 60-hertz high-potential test of 1 .1 5 times the rated line-to-line rms voltage 
for 1 minute. 

d. Using 500 volts direct-current, take a 1 -minute insulation resistance measurement following the 
procedure as outlined in IEEE 43. The minimum insulation resistance in megohms shall be > 5 
times the machine rated kilovolts plus 5. 

e. Rinse winding if necessary, dry, and apply other tests as may be required. 

NOTE — The tests in 20.18.1 and 20.18.2 are recommended as a test on a representative sample or prototype and should not be 
construed as a production test. 



20.19 MACHINE SOUND 

See Part 9 for Sound Power Limits and Measurement Procedures. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section Ml 

Part 20, Page 14 LARGE MACHINES— INDUCTION MACHINES 

20.20 REPORT OF TEST FORM FOR INDUCTION MACHINES 

For typical test forms, see IEEE Std 112. 

20.21 EFFICIENCY 

Efficiency and losses shall be determined in accordance with IEEE Std 1 12. Unless otherwise specified, 
the stray-load loss shall be determined by direct measurement (test loss minus conventional loss). 

When using Method B, Dynamometer, efficiency shall be determined by loss segregation including the 
smoothing of stray-load loss as outlined in IEEE 112. 

The following losses shall be included in determining the efficiency: 

a. Statorl 2 R 

b. Rotor l 2 R 

c. Core loss 

d. Stray load loss 

e. Friction and windage loss 1 

f. Power required for auxiliary items such as external pumps or fans necessary for the operation of 
the machine shall be stated separately. 

In determining l 2 R losses at all loads, the resistance of each winding shall be corrected to a temperature 
equal to an ambient temperature of 25°C plus the observed rated-load temperature rise measured by 
resistance. When the rated-load temperature rise has not been measured, the resistance of the winding 
shall be corrected to the following temperature: 



Class of Insulation System Temperature, Degrees C 

A 75 

B 95 

F 115 

H 130 



If the rated temperature rise is specified as that of a lower class of insulation system (e.g., motors for 
metal rolling mill service), the temperature for resistance correction shall be that of the lower insulation 
class. 

20.22 MECHANICAL VIBRATION 

See Part 7. 



In the case of induction machines furnished with thrust bearings, only that portion of the thrust bearing loss produced by the 
machine itself shall be included in the efficiency calculation. Alternatively, a calculated value of efficiency, including bearing loss due 
to external thrust load, shall be specified. 

In the case of induction machines furnished with less than a less than a full set of bearings, friction and windage losses which are 
representative of the actual installation shall be determined by (1) calculation or (2) experience with shop test bearings and shall be 
included in the efficiency calculations. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 1 5 

20.23 REED FREQUENCY OF VERTICAL MACHINES 

In a single degree of freedom system, the static deflection of the mass (A s , inches) is related to the 
resonant frequency of the system (f n , cycles per minute) as follows: 

4 

/n= ^-Vg /A s 

Where: g = 1389600 in/min 2 

Vertical or other flange-mounted induction machines are frequently mounted on some part of the driven 
(or driving) machine such as a pump adapter. The resulting system may have a radial resonant frequency 
(reed frequency) the same order of magnitude as the rotational speed of the induction machine. This 
system frequency can be calculated from the preceding equation. When the resonant frequency of the 
system is too close to the rotational speed, a damaging vibration level may result. 

The vertical induction machine manufacturer should supply the following information to aid in determining 
the system resonant frequency, f n : 

a. Machine weight 

b. Center of gravity location— This is the distance from the machine mounting flange to the center of 
gravity of the machine. 

c. Machine static deflection — This is the distance the center of gravity would be displaced downward 
from its original position if the machine were horizontally mounted. This value assumes that the 
machine uses its normal mounting and fastening means but that the foundation to which it is 
fastened does not deflect. 

20.24 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE OF POLYPHASE 
SQUIRREL-CAGE INDUCTION MOTORS 

When the line voltages applied to a polyphase induction motor are not equal, unbalanced currents in the 
stator windings will result. A small percentage voltage unbalance will result in a much larger percentage 
current unbalance. Consequently, the temperature rise of the motor operating at a particular load and 
percentage voltage unbalance will be greater than for the motor operating under the same conditions with 
balanced voltages. 

Voltages should be evenly balanced as closely as can be read on a voltmeter. If the voltages are 
unbalanced, the rated horsepower of polyphase squirrel-cage induction motors should be multiplied by 
the factor shown in Figure 20-2 to reduce the possibility of damage to the motor. 1 Operation of the motor 
with more than a 5-percent voltage unbalance is not recommended. 

When the derating curve of Figure 20-2 is applied for operation on unbalanced voltages, the selection 
and setting of the overload device should take into account the combination of the derating factor applied 
to the motor and the increase in current resulting from the unbalanced voltages. This is a complex 
problem involving the variation in motor current as a function of load and voltage unbalance in addition to 
the characteristics of the overload device relative to l ma ximum or l averafle . In the absence of specific 
information it is recommended that overload devices be selected or adjusted, or both, at the minimum 
value that does not result in tripping for the derating factor and voltage unbalance that applies. When the 
unbalanced voltages are anticipated, it is recommended that the overload devices be selected so as to be 
responsive to l max imum in preference to overload devices responsive to l averag e- 



The derating factor shown in Figure 20-2 is applicable only to motors with normal starting torque, (i.e., motors typically intended for 
service with centrifugal pumps, fans, compressors, etc.) where the required starting or pull-up torque, or both, is less than 100 
percent of rated full-load torque. For motors with other torque characteristics, the motor manufacturer should be consulted. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 20, Page 16 



Section III 
LARGE MACHINES— INDUCTION MACHINES 



1.0 
































if 0.9 










o 
|0.8 










































LU 
Q 
07 























12 3 4 5 

PERCENT VOLTAGE UNBALANCE 

Figure 20-2 

POLYPHASE SQUIRREL-CAGE INDUCTION MOTORS DERATING FACTOR 

DUE TO UNBALANCED VOLTAGE 

20.24.1 Effect on Performance — General 

The effect of unbalanced voltages on polyphase induction motors is equivalent to the introduction of a 
"negative sequence voltage" having a rotation opposite to that occurring with balanced voltages. This 
negative-sequence voltage produces an air gap flux rotating against the rotation of the rotor, tending to 
produce high currents. A small negative-sequence voltage may produce current in the windings 
considerably in excess of those present under balanced voltage conditions. 

20.24.2 Voltage Unbalance Defined 

The voltage unbalance in percent may be defined as: 

maximum voltage deviation from average voltage 



percent voltage unbalance = 100 x 



average voltage 



EXAMPLE: With voltages of 2300, 2220, and 2185, the average is 2235, the maximum deviation from the average is 65, the 
percentage unbalance = 100 x 65/2235 = 2.9 percent 

20.24.3 Torques 

The locked-rotor torque and breakdown torque are decreased when the voltage is unbalanced. If the 
voltage unbalance is extremely severe, the torques might not be adequate for the application. 

20.24.4 Full-Load Speed 

The full-load speed is reduced slightly when the motor operates at unbalanced voltages. 

20.24.5 Currents 

The locked-rotor current will be unbalanced to the same degree that the voltages are unbalanced but the 
locked rotor kVA will increase only slightly. 

The currents at normal operating speed with unbalanced voltages will be greatly unbalanced in the order 
of 6 to 1 times the voltage unbalance. 



MANUFACTURING 



20.25 NAMEPLATE MARKING 



The following information shall be given on all nameplates. For abbreviations, see 1.79. For some 
examples of additional information that may be included on the nameplate see 1.70.2. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 17 



20.25.1 Alternating-Current Polyphase Squirrel-Cage Motors 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Temperature rise 1 

e. Rpm at rated load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Rated-load amperes 

j. Code letter (see 20.9) 

k. Service factor 

20.25.2 Polyphase Wound-Rotor Motors 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Temperature rise 2 

e. Rpm at rated load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Rated-load amperes 

j. Secondary amperes at full load 

k. Secondary voltage 

I. Service factor 

20.25.3 Polyphase Squirrel-Cage Generators 

a. Manufacturer's type and frame designation 

b. Kilowatt rating 

c. Time rating 

d. Temperature rise 1 

e. Rpm at rated load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Rated-load amperes 



1 As an alternative marking, this item shall be permitted to be replaced by the following: 

a. Maximum ambient temperature for which the machine is designed (see 20.8.3). 

b. Insulation system designation (if stator and rotor use different classes of insulation systems, both insulation systems shall be 
given, that for the stator being given first). 

2 As an alternative marking, this item shall be permitted to be replaced by the following: 

a. Maximum ambient temperature for which the machine is designed (see 20.8.3). 

b. Insulation system designation (if stator and rotor use different classes of insulation systems, both insulation 
systems shall be given, that for the stator being given first). 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section lit 

Part 20, Page 1 8 LARGE MACHINES— INDUCTION MACHINES 



20.25.4 Polyphase Wound-Rotor Generators 

a. Manufacturer's type and frame designation 

b. Kilowatt rating 

c. Time rating 

d. Temperature rise 1 

e. Rpm at rated load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Rated-load amperes 

j. Secondary amperes at full speed 

k. Secondary voltage 

20.26 MOTOR TERMINAL HOUSINGS AND BOXES 

20.26.1 Box Dimensions 

When induction machines covered by this Part 20 are provided with terminal housings for line cable 
connections, 1 the minimum dimensions and usable volume shall be as indicated in Table 20-3 for Type I 
terminal housings or Figure 20-3 for Type II terminal housings. 

Unless otherwise specified, when induction machines are provided with terminal housings, a Type I 
terminal housing shall be supplied. 

20.26.2 Accessory Lead Terminations 

For machines rated 601 volts and higher, accessory leads shall terminate in a terminal box or boxes 
separate from the machine terminal housing. As an exception, current and potential transformers located 
in the machine terminal housing shall be permitted to have their secondary connections terminated in the 
machine terminal housing if separated from the machine leads by a suitable physical barrier. 

20.26.3 Lead Terminations of Accessories Operating at 50 Volts or Less 

For machines rated 601 volts and higher, the termination of leads of accessory items normally operating 
at a voltage of 50 volts (rms) or less shall be separated from leads of higher voltage by a suitable physical 
barrier to prevent accidental contact or shall be terminated in a separate box. 



Terminal housings containing stress cones, surge capacitors, surge arresters, current transformers, or potential transformers 
require individual consideration. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— INDUCTION MACHINES 



MG 1-2009 
Part 20, Page 19 



Table 20-3 

TYPE I TERMINAL HOUSING: 

UNSUPPORTED AND INSULATED TERMINATIONS 



Voltage 



Maximum Full-Load 
Current 



Minimum Usable 
Volume, Cubic Inches 



Minimum Internal 
Dimension, Inches 



Minimum Centerline 
Distance,* Inches 



0-600 


400 


900 


8 






600 


2000 


8 






900 


3200 


10 






1200 


4600 


14 




601-2400 


160 


180 


5 






250 


330 


6 






400 


900 


8 






600 


2000 


8 


12.6 




900 


3200 


10 


12.6 




1500 


5600 


16 


20.1 


2401-4800 


160 


2000 


8 


12.6 




700 


5600 


14 


16 




1000 


8000 


16 


20 




1500 


10740 


20 


25 




2000 


13400 


22 


28.3 


4801-6900 


260 


5600 


14 


16 




680 


8000 


16 


20 




1000 


9400 


18 


25 




1500 


11600 


20 


25 




2000 


14300 


22 


28.3 


6901-13800 


400 


44000 


22 


28.3 




900 


50500 


25 


32.3 




1500 


56500 


27.6 


32.3 




2000 


62500 


30.7 


32.3 



*Minimum distance from the entrance plate for conduit entrance to the centerline of machine leads. 

20.27 EMBEDDED TEMPERATURE DETECTORS 

Embedded temperature detectors are temperature detectors built into the machine during construction at 
points which are inaccessible after the machine is built. 

Unless otherwise specified, when machines are equipped with embedded detectors they shall be of the 
resistance temperature detector type. The resistance element shall have a minimum width of 0.25 inch, 
and the detector length shall be approximately as follows: 



Core Length Inches 



Approximate Detector Length, 
Inches 



12 or less 

Greater than 12 and less than 40 

40 or greater 



6 

10 
20 



For motors rated 6000 hp or less or generators rated less than 5000 kW or 5000 kVA, the minimum 
number of detectors shall equal the number of phases for which the machine is wound (i.e., three 
detectors for a three-phase machine). For motors rated greater than 6000 hp or generators rated 5000 
kW (or kVA) or higher the minimum number of detectors shall be six. The detectors shall be suitably 
distributed around the circumference, located between the coil sides, and in positions having normally the 
highest temperature along the length of the slot. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 20, Page 20 



Section III 
LARGE MACHINES— INDUCTION MACHINES 



The detector shall be located in the center of the slot (with the respect to the slot width) and in intimate 
contact with the insulation of both the upper and lower coil sides whenever possible; otherwise, it shall be 
in contact with the insulation of the upper coil side (that is, the coil side nearest the air gap). Each 
detector shall be installed, and its leads brought out, so that the detector is effectively protected from 
contact with the cooling medium. If the detector does not occupy the full length of the core, suitable 
packing shall be inserted between the coils to the full length of the core to prevent the cooling medium 
from directly contacting the detector. 











Minimum Dimensions (Inches) 








Machine Voltage 


L 


W 


D 


A 


B 


C 




X 


E 


F 


G 


460-600 


24 


18 


18 


9-1/2 


8-1/2 


4 




5 


2-1/2 


4 


12 


2300-4160 


26 


27 


18 


9-1/2 


8-1/2 


5-1/2 




8 


3-1/2 


5 


14 


6600-6900 


36 


30 


18 


9-1/2 


8-1/2 


6 




9 


4 


6 


30 


13200-13800 


48 


48 


25 


13-1/2 


11-1/2 


8-1/2 




13-1/2 


6-1/2 


9-1/2 


36 




MACHINE 
ENCLOSURE 
























o^x-^f*-x»-hc 



, ^h hj Ml 

m f uf f w 



V 



A 



DISTANCE FROM THE 
MANUFACTURER 
SUPPLIED TERMINAL 
TO THE BOTTOM OF 
THE BOX 



t/ 



L G 



V V 



SHIELD 

GROUND 

SCREW 



Figure 20-3 
TYPE II MACHINE TERMINAL HOUSING STANDOFF— INSULATOR-SUPPORTED INSULATED 

OR UNINSULATED TERMINATIONS 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 21 



APPLICATION DATA 

20.28 SERVICE CONDITIONS 

20.28.1 General 

Induction machines should be properly selected with respect to their service conditions, usual or unusual, 
both of which involve the environmental conditions to which the machine is subjected and the operating 
conditions. 

Machines conforming to this Part 20 are designed for operation in accordance with their ratings under 
one or more unusual service conditions. Definite-purpose or special-purpose machines may be required 
for some unusual conditions. 

Service conditions, other than those specified as usual, may involve some degree of hazard. The 
additional hazard depends upon the degree of departure from usual operating conditions and the severity 
of the environment to which the machine is exposed. The additional hazard results from such things as 
overheating, mechanical failure, abnormal deterioration of the insulation system, corrosion, fire, and 
explosion. 

Although experience of the user may often be the best guide, the manufacturer of the driven (or driving) 
equipment and the induction machine manufacturer should be consulted for further information regarding 
any unusual service conditions which increase the mechanical or thermal duty on the machine and, as a 
result, increase the chances for failure and consequent hazard. This further information should be 
considered by the user, his consultants, or others most familiar with the details of the application involved 
when making the final decision. 

20.28.2 Usual Service Conditions 

Usual service conditions include the following: 

a. Exposure to an ambient temperature in the range of -15°C to 40°C or, when water cooling is used, 
an ambient temperature range of 5°C (to prevent freezing of water) to 40°C, except for machines 
other than water cooled having slip rings for which the minimum ambient temperature is 0°C. 

b. An altitude not exceeding 3300 feet (1000 meters) 

c. A location and supplementary enclosure, if any, such that there is no serious interference with the 
ventilation of the machine. 

20.28.3 Unusual Service Conditions 

The manufacturer should be consulted if any unusual service conditions exist which may affect the 
construction or operation of the machine. Among such conditions are: 

a. Exposure to: 

1. Combustible, explosive, abrasive, or conducting dusts 

2. Lint or very dirty operating conditions where the accumulation of dirt will interfere with normal 
ventilation 

3. Chemical fumes, flammable or explosive gases 

4. Nuclear radiation 

5. Steam, salt-laden air, or oil vapor 

6. Damp or very dry locations, radiant heat, vermin infestation, or atmospheres conducive to the 
growth of fungus 

7. Abnormal shock, vibration, or mechanical loading from external sources 

8. Abnormal axial or side thrust imposed on the machine shaft 

b. Operation where: 

1 . There is excessive departure from rated voltage or frequency, or both (see 20.14) 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 20, Page 22 LARGE MACHINES— INDUCTION MACHINES 

2. The deviation factor of the alternating-current supply voltage exceeds 1 percent 

3. The alternating-current supply voltage is unbalanced by more than 1 percent (see 20.24) 

4. Low noise levels are required 

5. The power system is not grounded (see 20.36) 

c. Operation at speeds other than the rated speed (see 20.14) 

d. Operation in a poorly ventilated room, in a pit, or in an inclined position 

e. Operation where subjected to: 

1 . Torsional impact loads 

2. Repetitive abnormal overloads 

3. Reversing or electric braking 

4. Frequent starting (see 20.12) 

5. Out-of-phase bus transfer (see 20.33) 

6. Frequent short circuits 

20.29 END PLAY AND ROTOR FLOAT FOR COUPLED SLEEVE BEARING HORIZONTAL 
INDUCTION MACHINES 

20.29.1 General 

Operating experience on horizontal sleeve bearing induction machines has shown that sufficient thrust to 
damage bearings may be transmitted to the induction machine through a flexible coupling. Damage to 
induction machine bearings due to thrusts under such conditions will be avoided if the following limits are 
observed by the induction machine manufacturer and the driven (or driving) equipment/induction machine 
assembler. 

20.29.2 Limits 

Where induction machines are provided with sleeve bearings, the machine bearings and limited-end-float 
coupling should be applied as indicated in the following table: 



Machine Hp (kW) 


Synchronous Speed, 
Rpm 


Min 


. Motor Rotor End 
Float, Inches 


Max. Coupling End 
Float,* Inches 


500 (400) and below 

300 (250) to 500 (400) incl. 

600 (500) and higher 


1800 and below 

3600 and 3000 

all speeds 




0.25 
0.50 
0.50 


0.09 
0.19 
0.19 



'Couplings with elastic axial centering forces are usually satisfactory without these precautions. 

20.29.3 Marking Requirements 

To facilitate the assembly of driven (or driving) equipment and sleeve bearing induction machines, the 
induction machine manufacturer should: 

a. Indicate on the induction machine outline drawing the minimum machine rotor end play in inches. 

b. Mark rotor end play limits on machine shaft. 

NOTE— The induction machine and the driven (or driving) equipment should be assembled and adjusted at the installation site 
so that there will be some endwise clearance in the induction machine bearing under all operating conditions. The difference 
between the rotor end play and the end float in the coupling allows for expansion and contraction in the driven (or driving) 
equipment, for clearance in the driven (or driving) equipment thrust bearing, for endwise movement in the coupling, and for 
assembly. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 23 



20.30 PULSATING STATOR CURRENT IN INDUCTION MOTORS 

When the driven load, such as that of reciprocating type pumps, compressors, etc., requires a variable 
torque during each revolution, it is recommended that the combined installation have sufficient inertia in 
its rotating parts to limit the variations 1 in motor stator current to a value not exceeding 66 percent of full- 
load current. 

20.31 ASEISMATIC CAPABILITY 

20.31.1 General 

The susceptibility of induction machines to earthquake damage is particularly influenced by their 
mounting structures. Therefore, the asiesmatic capability requirements for induction machines should be 
based on the response characteristics of the system consisting of the induction machine and mounting 
structure or equipment on which the induction machine will be mounted when subjected to the specified 
earthquake ground motions. 

20.31 .2 Frequency Response Spectrum 

System aseismatic capability requirements should preferably be given in terms of the peak acceleration 
which a series of "single-degree-of-freedom" oscillators, mounted on the induction machine support 
structure system, would experience during the specified earthquake. A family of continuous plots of peak 
acceleration versus frequency over the complete frequency range and for various values of damping is 
re f errec j to as a "frequency response spectrum" for the induction machine and support structure system. 
This frequency response spectrum should be utilized by those responsible for the system or mounting 
structure, or both, to determine the aseismatic capability requirement which is to be applied to the 
induction machine alone when it is mounted on its supporting structure. The induction machine 
manufacturer should furnish the required data for induction machine natural frequency or mass stiffness, 
or both, to allow this determination to be made. 

20.31 .3 Units for Capability Requirements 

Induction machine aseismatic capability requirements should preferably be stated as a single 
acceleration or "g" value as determined from the system structural characteristics and input data as 
outlined in 20.31 .1 and 20.31 .2. 

20.31 .4 Recommended Peak Acceleration Limits 

For induction machines covered by this Part 20, it is recommended that the supporting base structure for 
the induction machine limit the peak acceleration due to earthquakes to the following maximum values: 

a. One and one-half g's in any direction 

b. One g vertically upward and downward in addition to the normal downward gravity of one g. 

The loads imposed as a result of the foregoing inputs can be assumed to have negligible effect upon the 
operation of the induction machine. 

NOTES 

1 —Accelerations are given in g's or multiples of the "standard" gravitational acceleration (32.2 ft/sec 2 ) (9.81 meter/sec 2 ) and are 
based on an assumed damping factor of 1 percent. Horizontal and vertical accelerations are assumed to act individually but not 
simultaneously. 

2— The axial restraint of the shaft in most horizontal applications is provided by the driven (or driving) equipment or other devices 
external to the induction machine. In such cases, the axial seismic loading of the shaft should be included in the requirements for 
the driven (or driving) equipment. In other applications, restraint of the driven (or driving) equipment rotor may be provided by the 
induction machine. In such cases, the axial seismic loading of the shaft should be included in the requirements for the induction 
machine. 



1 The basis for determining this variation should be by oscillograph or similar measurement and not by ammeter readings. A line 
should be drawn on full-load current of the motor. (The maximum value of the motor stator current is to be assumed as 1 .41 times 
the rated full-load current.) 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 20, Page 24 LARGE MACHINES— INDUCTION MACHINES 

3— When a single g value is given, it is implied that this g value is the maximum value of peak acceleration on the actual frequency 
response curve for the induction machine when mounted on its supporting structure for a particular value of system structural 
damping and specified earthquake ground motion. Values for other locations are frequently inappropriate because of nonrigid 
characteristics of the intervening structure. 

20.32 BELT, CHAIN, AND GEAR DRIVE 

When induction machines are for belt, chain, or gear drive, the manufacturer should be consulted. 

20.33 BUS TRANSFER OR RECLOSING 

Induction machines are inherently capable of developing transient current and torque considerably in 
excess of rated current and torque when exposed to an out-of-phase bus transfer or momentary voltage 
interruption and reclosing on the same power supply. The magnitude of this transient torque may range 
from 2 to 20 times rated torque and is a function of the machine, operating conditions, switching time, 
rotating system inertias and torsional spring constants, number of motors on the bus, etc. 

20.33.1 Slow Transfer or Reclosing 

A slow transfer or reclosing is defined as one in which the length of time between disconnection of the 
motor from the power supply and reclosing onto the same or another power supply is equal to or greater 
than one and a half motor open-circuit alternating-current time constants (see 1 .60). 

It is recommended that slow transfer or reclosing be used so as to limit the possibility of damaging the 
motor or driven (or driving) equipment or both. This time delay permits a sufficient decay in rotor flux 
linkages so that the transient current and torque associated with the bus transfer or reclosing will remain 
within acceptable levels. When several motors are involved, the time delay should be based on one and a 
half times the longest open-circuit time constant of any motor on the system being transferred or 
reclosed. 

20.33.2 Fast Transfer or Reclosing 

A fast transfer or reclosing is defined as one which occurs within a time period shorter than one and a half 
open-circuit alternating-current constants. In such cases transfer or reclosure should be timed to occur 
when the difference between the motor residual voltage and frequency, and the incoming system voltage 
and frequency will not result in damaging transients. 

The rotating masses of motor-load system, connected by elastic shafts, constitute a torsionally 
responsive mechanical system which is excited by the motor electromagnetic (air gap) transient torque 
that consists of the sum of an exponentially decaying unidirectional component and exponentially 
decaying oscillatory components at several frequencies, including power frequency and slip frequency. 
The resultant shaft torques may be either attenuated or amplified with reference to the motor 
electromagnetic (air-gap) torque, and for this reason it is recommended that the electromechanical 
interactions of the motor, the driven equipment, and the power system be studied for any system where 
fast transfer or reclosure is used. 

The electrical and mechanical parameters required for such a study will be dependent upon the method 
of analysis and the degree of detail employed in the study. When requested, the motor manufacturer 
should furnish the following and any other information as may be required for the system study: 

a. Reactances and resistances for the electrical equivalent circuit for the motor, as depicted in Figure 
1-4, for both unsaturated and saturated (normal slip frequency) condition 

b. Wk 2 of the motor rotor 

c. Spring constant of the motor shaft 



> Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 25 



20.34 POWER FACTOR CORRECTION 

WARNING: When power factor correction capacitors are to be switched with an induction machine, the 
maximum value of corrective kVAR should not exceed the value required to raise the no-load power 
factor to unity. Corrective kVAR in excess of this value may cause over-excitation resulting in high 
transient voltages, currents, and torques that can increase safety hazards to personnel and can cause 
possible damage to the machine or to the driven (or driving) equipment. For applications where 
overspeed of the machine is contemplated (i.e., induction generators, paralleled centrifugal pumps 
without check valves), the maximum corrective kVAR should be further reduced by an amount 
corresponding to the square of the expected overspeed. 

a. The maximum value of corrective kVAR to be switched with an induction machine can be 
calculated as follows: 

0.9xl nl xExV3 



kVAR< 



1000 x (1 + OS) 2 



Where: 

l n i = No-load current at rated voltage 

E = Rated voltage 

OS = Per unit maximum expected overspeed 

b. The use of capacitors for power factor correction, switched at the motor terminals, is not 

recommended for machines subjected to high speed bus transfer or reclosing, elevator motors, 
multi-speed motors, motors used on plugging or jogging applications, and motors used with open 
transition autotransformer or wye delta starting. For such applications the machine manufacturer 
should be consulted before installing power factor corrective capacitors switched with the 
machine. 

Closed transition autotransformer starters may introduce a large phase shift between the supply voltage 
and the motor internal voltage during the transition period when the autotransformer primary is in series 
with the motor winding. To minimize the resultant transient current and torque when the autotransformer 
is subsequently shorted out, capacitors for power factor correction should be connected on the line side 
of the autotransformer. 

20.35 SURGE CAPABILITIES OF AC WINDINGS WITH FORM-WOUND COILS 

20.35.1 General 

Stator winding insulation systems of ac machines are exposed to stresses due to the steady state 
operating voltages and to steep-fronted voltage surges of high amplitudes. Both types of voltages stress 
the ground insulation. The steep-fronted surge also stresses the turn insulation. If the rise time of the 
surge is steep enough (0.1 to 0.2 jisec), most of the surge could appear across the first or line coil and its 
distribution in the coil could be non-linear. 

20.35.2 Surge Sources 

The steep-fronted surges appearing across the motor terminals are caused by lightning strikes, normal 
circuit breaker operation, motor starting, aborted starts, bus transfers, switching windings (or speeds) in 
two-speed motors, or switching of power factor correction capacitors. Turn insulation testing itself also 
imposes a high stress on the insulation system. 

20.35.3 Factors Influencing Magnitude and Rise Time 

The crest value and rise time of the surge at the motor depends on the transient event taking place, on 
the electrical system design, and on the number and characteristics of all other devices in the system. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 20, Page 26 LARGE MACHINES— INDUCTION MACHINES 

These include, but are not limited to, the motor, the cables connecting the motor to the switching device, 
the type of switching device used, the length of the busbar and the number and sizes of all other loads 
connected to the same busbar. 

20.35.4 Surge Protection 

Although certain surge withstand capability levels must be specified for the windings, it is desirable, 
because of the unpredictable nature of the surge magnitudes and rise times, that for critical applications 
surge protection devices be installed at or very close to the motor terminals to slope back the rise of the 
incoming surge thereby making it more evenly distributed across the entire winding. 

20.35.5 Surge Withstand Capability for Standard Machines 

Stator windings of ac machines, unless otherwise specified, shall be designed to have a surge withstand 
capability of 2 pu (per unit) at a rise time of 0.1 to 0.2 jas and 4.5 pu at 1.2ns, or longer, where one pu is 
the crest of the rated motor line-to-ground voltage, or: 

1pu = V273 x V L _ L 

20.35.6 Special Surge Withstand Capability 

When higher surge capabilities are required, the windings shall be designed for a surge withstand 
capability of 3.5 pu at a rise time of 0.1 to 0.2 |is and 5 pu at a rise time of 1 .2 |iS or longer. This higher 
capability shall be by agreement between the customer and the manufacturer. 

20.35.7 Testing 

Unless otherwise agreed to between the customer and the manufacturer, the method of test and the test 
instrumentation used shall be per IEEE Std 522. 

The test may be made at any of the following steps of manufacture: 

a. On individual coils before installation in slots 

b. On individual coils after installation in slots, prior to connection with stator slot wedging and 
endwinding support systems installed 

c. On completely wound and finished stator 

The actual step where testing is done shall be a matter of agreement between the customer and the 
manufacturer. 

20.35.8 Test Voltage Values 

The test voltage steps at 20. 35. 7. a and 20.35. 7. b shall be at least: 

a. 65% of the values specified in 20.35.5 or 20.35.6 for unimpregnated coils 

b. 80% of the values specified in 20.35.5 or 20.35.6 for resin-rich coils 

20.36 MACHINES OPERATING ON AN UNGROUNDED SYSTEM 

Alternating-current machines are intended for continuous operation with the neutral at or near ground 
potential. Operation on ungrounded systems with one line at ground potential should be done only for 
infrequent periods of short duration, for example as required for normal fault clearance. If it is intended to 
operate the machine continuously or for prolonged periods in such conditions, a special machine with a 
level of insulation suitable for such operation is required. The motor manufacturer should be consulted 
before selecting a motor for such an application. 

Grounding of the interconnection of the machine neutral points should not be undertaken without 
consulting the System Designer because of the danger of zero-sequence components of currents of all 
frequencies under some operating conditions and the possible mechanical damage to the winding under 
line-to-neutral fault conditions. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— INDUCTION MACHINES Part 20, Page 27 

Other auxiliary equipment connected to the motor such as, but not limited to, surge capacitors, power 
factor correction capacitors, or lightning arresters, may not be suitable for use on an ungrounded system 
and should be evaluated independently. 

20.37 OCCASIONAL EXCESS CURRENT 

Induction motors while running and at rated temperature shall be capable of withstanding a current equal 
to 1 50 percent of the rated current for 30 seconds. 

Excess capacity is required for the coordination of the motor with the control and protective devices. The 
heating effect in the machine winding varies approximately as the product of the square of the current 
and the time for which this current is being carried. The overload condition will thus result in increased 
temperatures and a reduction in insulation life. The motor should therefore not be subjected to this 
extreme condition for more than a few times in its life. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1 -2009 Section III 

Part 20, Page 28 LARGE MACHINES— INDUCTION MACHINES 



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© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21 



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Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21, Page 1 

Section III 

LARGE MACHINES 

Part 21 

LARGE MACHINES— SYNCHRONOUS MOTORS 



(The standards in this Part 21 do not apply to nonexcited synchronous motors, nor do they necessarily 
apply to synchronous motors of motor-generator sets.) 

RATINGS 
21.1 SCOPE 

The standards in this Part 21 of this Section III cover (1) synchronous motors built in frames larger than 
those required for synchronous motors having the continuous open-type ratings given in the table below, 
and (2) all ratings of synchronous motors of the revolving-field type of 450 rpm and slower speeds. 



Motors, Synchronous, Hp 


Power Factor 


Synchronous Speed 


Unity 0.8 


3600 


500 400 


1800 


500 400 


1200 


350 300 


900 


250 200 


720 


200 150 


600 


150 125 


514 


125 100 



21.2 BASIS OF RATING 

Synchronous motors covered by this Part 21 shall be rated on a continuous-duty basis unless otherwise 
specified. The output rating shall be expressed in horsepower available at the shaft at a specified speed, 
frequency, voltage, and power factor. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 2 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



21.3 



HORSEPOWER AND SPEED RATINGS 



Horsepower Ratings 



20 
25 

30 
40 
50 

60 
75 
100 
125 
150 

200 
250 
300 
350 
400 

450 
500 



600 
700 
800 
900 
1000 

1250 
1500 
1750 
2000 
2250 

2500 
3000 
3500 
4000 
4500 

5000 
5500 



6000 

7000 
8000 
9000 
10000 

11000 
12000 
13000 
14000 
15000 

16000 
17000 
18000 
19000 
20000 

22500 

25000 



27500 
30000 
32500 
35000 
37500 

40000 
45000 
50000 
55000 
60000 

65000 
70000 
75000 
80000 
90000 

100000 



Speed Ratings, Rpm at 60 Hertz* 



3600 


514 


277 


164 


100 


1800 


450 


257 


150 


95 


1200 


400 


240 


138 


90 


900 


360 


225 


129 


86 


720 


327 


200 


120 


80 


600 


300 180 


109 





*At 50 hertz, the speeds are 5/6 of the 60-hertz speeds. 

NOTE - It is not practical to build motors of all horsepower ratings at all speeds. 

21.4 POWER FACTOR 

The power factor for synchronous motors shall be unity or 0.8 leading (overexcited). 

21.5 VOLTAGE RATINGS 
21.5.1 Voltage Ratings 

For three phase ac machines, 50 Hz or 60 Hz, intended to directly connected to distribution or utilization 
systems, the rated voltages shall be selected from the voltages given in following table. Other voltages 
are subject to the approval between manufacturer and end user. 



Nominal System voltages 
for 50 Hz* 


Nominal System voltages 
for 60 Hz 


Preferred motor rated 

voltages for 60 Hz (North 

American Practice) 


a) b) 


480 


460 


400 400 


600 


575 


3300 3000 


2400 


2300 


6600 6000 


4160 


4000 


11000 10000 


6900 


6600 




13800 


13200 



I * Either one of the voltage series a) or b) is used in certain countries for 50 Hz. 

8NOTE — For synchronous motors with a leading power factor (overexcited) the recommended rated voltage is the nominal system 
voltages for 60 Hz. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21, Page 3 



21 .5.2 Preferred Motor Output/Voltage Rating 

It is not practical to build synchronous machines of all ratings for all voltages. In general, based on motor 
design and manufacturing considerations, preferred motor voltage ratings are as follows: 

a) 60 HZ power supply: 



Horsepower 



100-600 



200-5000 



200-10000 



1000-15000 



3500 and up 



Voltage Rating 



460 - 575 



2300 - 2400 



4000-4160 



6000 - 6600 



13200-13800 



b) 50 HZ power supply: 



Horsepower 


Voltage Rating 


100-500 


380 - 440 


600-8000 


3000 - 3300 


700-15000 


6000 - 6600 


3000 and up 


10000-11000 



21.6 FREQUENCIES 

Frequencies shall be 50 and 60 hertz. 

21.7 EXCITATION VOLTAGE 

The excitation voltages for field windings shall be 62-1/2, 125, 250, 375, and 500 volts direct current. 
These excitation voltages do not apply to motors of the brushless type with direct-connected exciters. 

NOTE— It is not practical to design all horsepower ratings of motors for all of the foregoing excitation voltages. 

21.8 SERVICE FACTOR 

21 .8.1 Service Factor of 1 .0 

When operated at rated voltage and frequency, synchronous motors covered by this Part 21 and having a 
rated temperature rise in accordance with 21 .10.1 shall have a service factor of 1 .0. 

In those applications requiring an overload capacity, the use of a higher horsepower rating, as given in 
21 .3, is recommended to avoid exceeding the temperature rise for the insulation class used and to 
provide adequate torque capacity. 

21 .8.2 Service Factor of 1 .1 5 

When a service factor other than 1 .0 is specified, it is preferred that motors furnished in accordance with 
this Part 21 will have a service factor of 1 .15 and temperature rise not in excess of that specified in 
21.10.2 when operated at the service factor horsepower with rated voltage and frequency maintained. 

21 .8.3 Application of Motor with 1.15 Service Factor 
21.8.3.1 General 

A motor having a 1 1 5 service factor is suitable for continuous operation at rated load under the usual 
service conditions given in 21.28.2. When the rated voltage and frequency are maintained, the motor may 
be overloaded up to the horsepower obtained by multiplying the rated horsepower by the service factor 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Q ^ ion „, 

d~^"m o a Section III 

Part 21 , Page 4 Large MACHINES-SYNCHRONOUS MOTORS 

shown on the nameplate. At the service factor load, the motor will have efficiency and power factor or 
field excitation values different from those at rated load. 

1 .0 power factor motors will have their field excitation adjusted to maintain the rated power factor Motors 
with power factors other than 1.0 (i.e., over-excited) will have their field excitation held constant at the 
rated load value and the power factor allowed to change. 

1 NOTE-The percent values of locked-rotor, pull-in and pull-out torques and of locked-rotor current are based on the rated 
I Horsepower. 

21.8.3.2 Temperature Rise 

When operated at the 1 . 1 5 service factor load the motor will have a temperature rise not in excess of that 
specified in 21.10.2 with rated voltage and frequency applied and the field set in accordance with 
21.8.3.1. No temperature rise is specified or implied for operation at rated load. 

NOTES 

lrJl bie l 21 1 °: 1 .?. nd 21 ; 10 - 2 a PP'y individually to a particular motor at 1.0 or 1.15 service factor. It is not intended or implied 
that they be applied to a single motor both at 1.0 and 1.15 service factors 

2-Operation at temperature rise values given in 2 1 .1 0.2 and for a 1 . 1 5 service factor load causes the motor insulation to age 
thermally at approximately twice the rate that occurs at the temperature rise values given in 21.10 1 for a motor with a 1 
service factor load, i.e., operation for one hour at specified 1.15 service factor is approximately equivalent to operation for two 
nours at 1 .0 service factor. 

21 .9 TYPICAL KW RATINGS OF EXCITERS FOR 60-HERTZ SYNCHRONOUS MOTORS 

When synchronous motors have individual exciters, the kilowatt ratings given in Tables 21-1 to 21-4 
inclusive, represent typical kilowatt ratings for such exciters. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section HI 












MG 1-2009 


LARGE MACHINES— SYNCHRONOUS MOTORS 






Part 21, Page5 








Table 21-1 










1.0 POWER FACTOR, 60-HERTZ, SYNCHRONOUS MOTORS, 


1800-514 RPM 








Exciter Ratings, 


kW 












Speed, Rpm 








Hp 


1800 


1200 


900 


720 


600 


514 


20 


0.75 


0.75 










25 


0.75 


0.75 


1.0 








30 


0.75 


1.0 


1.0 


1.5 






40 


0.75 


1.0 


1.5 


1.5 


1.5 




50 


1.0 


1.5 


1.5 


1.5 


2.0 




60 


1.0 


1.5 


1.5 


2.0 


2.0 




75 


1.0 


1.5 


2.0 


2.0 


3.0 


3.0 


100 


1.5 


1.5 


2.0 


2.0 


3.0 


3.0 


125 


1.5 


2.0 


3.0 


3.0 


3.0 


3.0 


150 


1.5 


2.0 


3.0 


3.0 


3.0 


4.5 


200 


2.0 


3.0 


3.0 


3.0 


4.5 


4.5 


250 


2.0 


3.0 


3.0 


4.5 


4.5 


4.5 


300 


2.0 


3.0 


4.5 


4.5 


4.5 


4.5 


350 


3.0 


3.0 


4.5 


4.5 


4.5 


6.5 


400 


3.0 


3.0 


4.5 


4.5 


6.5 


6.5 


450 


3.0 


4.5 


4.5 


4.5 


6.5 


6.5 


500 


3.0 


4.5 


4.5 


4.5 


6.5 


6.5 


600 


3.0 


4.5 


6.5 


6.5 


6.5 


6.5 


700 


4.5 


4.5 


6.5 


6.5 


6.5 


9.0 


800 


4.5 


6.5 


6.5 


6.5 


9.0 


9.0 


900 


4.5 


6.5 


6.5 


9.0 


9.0 


9.0 


1000 


4.5 


6.5 


9.0 


9.0 


9.0 


9.0 


1250 


6.5 


6.5 


9.0 


9.0 


13 


13 


1500 


6.5 


9.0 


9.0 


13 


13 


13 


1750 


9.0 


9.0 


13 


13 


13 


13 


2000 


9.0 


13 


13 


13 


13 


17 


2250 


9.0 


13 


13 


13 


17 


17 


2500 


13 


13 


13 


17 


17 


17 


3000 


13 


13 


17 


17 


17 


21 


3500 


13 


17 


17 


21 


21 


21 


4000 


17 


17 


21 


21 


21 


25 


4500 


17 


21 


21 


21 


25 


25 


5000 


17 


21 


25 


25 


33 


33 


5500 


21 


25 


25 


25 


33 


33 


6000 


21 


25 


33 


33 


33 


33 


7000 


25 


33 


33 


33 


33 


40 


8000 


33 


33 


40 


40 


40 


40 


9000 


33 


40 


40 


40 


50 


50 


10000 


33 


40 


50 


50 


50 


50 


11000 


40 


50 


50 


50 


50 


50 


12000 


40 


50 


50 


50 


65 


65 


13000 


50 


50 


65 


65 


65 


65 


14000 


50 


65 


65 


65 


65 


65 


15000 


50 


65 


65 


65 


65 


65 


16000 


65 


65 


65 


65 


85 


85 


17000 


65 


65 


85 


85 


85 


85 


18000 


65 


65 


85 


85 


85 


85 


19000 


65 


85 


85 


85 


85 


85 


20000 


65 


85 


85 


85 


85 


85 


22500 


85 


85 


85 


100 


100 


100 


25000 


85 


100 


100 


100 


100 


125 


27500 


100 


100 


125 


125 


125 


125 


30000 


100 


125 


125 


125 


125 


125 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
















Section III 


Part 21, Page 6 








LARGE MACHINES- 


-SYNCHRONOUS MOTORS 










Table 21-2 










0.8 POWER FACTOR, 60-HERTZ, SYNCHRONOUS MOTORS 


1800-514 RPM 












Exciter Ratings, 


kW 
















Speed, Rpm 








Hp 




1800 


1200 


900 




720 


600 


514 


20 




0.75 


1.5 












25 




1.0 


1.5 


1.0 










30 




1.0 


1.5 


2.0 




2.0 






40 




1.0 


1.5 


2.0 




3.0 


3.0 




50 




1.5 


2.0 


3.0 




3.0 


3.0 




60 




1.5 


2.0 


3.0 




3.0 


3.0 




75 




1.5 


2.0 


3.0 




3.0 


4.5 


4.5 


100 




2.0 


3.0 


3.0 




4.5 


4.5 


4.5 


125 




2.0 


3.0 


4.5 




4.5 


4.5 


4.5 


150 




2.0 


3.0 


4.5 




4.5 


4.5 


6.5 


200 




3.0 


4.5 


4.5 




4.5 


6.5 


6.5 


250 




3.0 


4.5 


4.5 




6.5 


6.5 


6.5 


300 




3.0 


4.5 


6.5 




6.5 


6.5 


9.0 


350 




4.5 


4.5 


6.5 




6.5 


9.0 


9.0 


400 




4.5 


6.5 


6.5 




6.5 


9.0 


9.0 


450 




4.5 


6.5 


6.5 




9.0 


9.0 


9.0 


500 




4.5 


6.5 


6.5 




9.0 


9.0 


9.0 


600 




6.5 


6.5 


9.0 




9.0 


13 


13 


700 




6.5 


9.0 


9.0 




9.0 


13 


13 


800 




6.5 


9.0 


9.0 




13 


13 


13 


900 




6.5 


9.0 


13 




13 


13 


13 


1000 




9.0 


9.0 


13 




13 


13 


17 


1250 




9.0 


13 


13 




13 


17 


17 


1500 




13 


13 


17 




17 


17 


17 


1750 




13 


13 


17 




17 


21 


21 


2000 




13 


17 


17 




21 


21 


21 


2250 




13 


17 


21 




21 


25 


25 


2500 




17 


17 


21 




21 


25 


25 


3000 




17 


21 


25 




25 


33 


33 


3500 




21 


25 


25 




33 


33 


33 


4000 




21 


25 


33 




33 


33 


40 


4500 




25 


33 


33 




33 


40 


40 


5000 




33 


33 


40 




40 


40 


40 


5500 




33 


33 


40 




40 


50 


50 


6000 




33 


40 


40 




50 


50 


50 


7000 




40 


40 


50 




50 


65 


65 


8000 




40 


50 


50 




65 


65 


65 


9000 




50 


50 


65 




65 


65 


65 


10000 




50 


65 


65 




65 


80 


85 


11000 




65 


65 


85 




85 


85 


85 


12000 




65 


65 


85 




85 


85 


85 


13000 




65 


85 


85 




85 


100 


100 


14000 




65 


85 


85 




85 


100 


100 


15000 




85 


85 


100 




100 


100 


100 


16000 




85 


85 


100 




100 


125 


125 


17000 




85 


100 


100 




100 


125 


125 


18000 




85 


100 


125 




125 


125 


125 


19000 




100 


100 


125 




125 


125 


125 


20000 




100 


125 


125 




125 


125 


170 


22500 




125 


125 


170 




170 


170 


170 


25000 




125 


125 


170 




170 


170 


170 


27500 




125 


170 


170 




170 


170 


170 


30000 




170 


170 


170 




170 


200 


200 



© Copyright 2009 by the National Electrical Manufacturers Association. 



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Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21 , Page 9 



TESTS AND PERFORMANCE 



21.10 TEMPERATURE RISE—SYNCHRONOUS MOTORS 

The observable temperature rise under rated-load conditions of each of the various parts of the 
synchronous motor, above the temperature of the cooling air, shall not exceed the values given in the 
appropriate table. The temperature of the cooling air is the temperature of the external air as it enters the 
ventilating openings of the machine, and the temperature rises given in the tables are based on a 
maximum temperature of 40°C for this external air. Temperatures shall be determined in accordance with 
IEEE Std 115. 



21.10.1 


Machines with 1.0 Service Factor at Rated Load 














Temperature Rise, Degrees C 










Class of Insulation System 




Item 


Method of Temperature 
Machine Part Determination 


A 


B F 


H 



Armature winding 

1 . All horsepower ratings 

2. 1 500 horsepower and less 

3. Over 1500 horsepower 

a) 7000 volts and less 

b) Over 7000 volts 

Field winding 

1 . Salient-pole motors 

2. Cylindrical rotor motors 



Resistance 


60 


80 


105 


125 


Embedded detector* 


70 


90 


115 


140 


Embedded detector* 


65 


85 


110 


135 


Embedded detector* 


60 


80 


105 


125 


Resistance 


60 


80 


105 


125 


Resistance 




85 


105 


125 



The temperatures attained by cores, amortisseur windings, collector rings, and miscellaneous parts (such as 
brushholders, brushes, pole tips, etc.) shall not injure the insulation or the machine in any respect. 



'Embedded detectors are located within the slots of the machine and can be either resistance elements or thermocouples. For 
motors equipped with embedded detectors, this method shall be used to demonstrate conformity with the standard (see 20.28). 



21 .1 0.2 Machines with 1.15 Service Factor at Service Factor Load 





Machine Part 


Method of Temperature 
Determination 




Temperature Rise 


Degrees C 








Class of Insulation System 




Item 


A 


B 


F 


H 


a. 


Armature winding 














1 . All horsepower ratings 


Resistance 


70 


90 


115 


135 




2. 1 500 horsepower and less 


Embedded detector* 


80 


100 


125 


150 




3. Over 1 500 horsepower 














a) 7000 volts and less 


Embedded detector* 


75 


95 


120 


145 




b) Over 7000 volts 


Embedded detector* 


70 


90 


115 


135 


b. 


Field winding 














1 . Salient-pole motors 


Resistance 


70 


90 


115 


135 




2. Cylindrical rotor motors 


Resistance 




95 


115 


135 


c. 


The temperatures attained by cores, amortisseur windings, collector rings, and miscellaneous parts (such as 
brushholders, brushes, pole tips, etc.) shall not injure the insulation or the machine in any respect. 





*Embedded detectors are located within the slots of the machine and can be either resistance elements or thermocouples. For 
motors equipped with embedded detectors, this method shall be used to demonstrate conformity with the standard (see 20.28). 



© Copyright 2009 by the National Electrical Manufacturers Association. 



s 



MG 1-2009 Section III 

Part 21, Page 10 LARGE MACHINES— SYNCHRONOUS MOTORS 

21.10.3 Temperature Rise for Ambients Higher than 40°C 

The temperature rises given in 21 .10.1 and 21.10.2 are based upon a reference ambient temperature of 
40°C. However, it is recognized that synchronous motors may be required to operate in an ambient 
temperature higher than 40°C. For successful operation of the motors in ambient temperatures higher 
than 40°C, the temperature rises of the motors given in 21.10.1 and 21.10.2 shall be reduced by the 
number of degrees that the ambient temperature exceeds 40°C. 

(Exception—for totally enclosed water-air-cooled machines, the temperature of the cooling air is the 
temperature of the air leaving the coolers. Totally enclosed water-air-cooled machines are normally 
designed for the maximum cooling water temperature encountered at the location where each machine is 
to be installed. With a cooling water temperature not exceeding that for which the machine is designed: 

a) On machines designed for cooling water temperatures of 5°C to 30°C--temperature of the air 
leaving the coolers shall not exceed 40°C. 

b) On machines designed for higher cooling water temperatures— the temperature of the air leaving the 
coolers shall be permitted to exceed 40°C provided the temperature rises for the machine parts are then 
limited to values less than those given in 21.10.1 and 21 .10.2 by the number of degrees that the 
temperature leaving the coolers exceeds 40°C.) 

21.10.4 Temperature Rise for Altitudes Greater than 3300 Feet (1000 Meters) 

For machines which operate under prevailing barometric pressure and which are designed not to exceed 
the specified temperature rise at altitudes from 3300 feet (1000 meters) to 13200 feet (4000 meters), the 
temperature rises, as checked by tests at low altitudes, shall be less than those listed in 21.10.1 and 
21.10.2 by 1 percent of the specified temperature rise for each 330 feet (100 meters) of altitude in excess 
of 3300 feet (1000 meters). 

21.10.5 Temperature Rise for Air-Cooled Motors for Ambients Lower than 40° C, but Not Below 
0°C* 

The temperature rises given in 21.10.1 and 21.10.2 are based upon a reference ambient temperature of 
40°C to cover most general environments. However, it is recognized that air-cooled„synchronous motors 
may be operated in environments where the ambient temperature of the cooling air will always be less 
than 40°C. When an air-cooled synchronous motor is marked with a maximum ambient less than 40°C 
then the allowable temperature rises in 21.10.1 and 21.10.2 shall be increased according to the following: 

a) For motors for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 21.10.1 and 21.10.2 is less than or equal to 5 G C then the 
temperature rises given in 21.10.1 and 21.10.2 shall be increased by the amount of the difference 
between 40°C and the lower marked ambient temperature. 

b) For motors for which the difference between the Reference Temperature and the sum of 40°C and 
the Temperature Rise Limit given in 21.10.1 and 21.10.2 is greater than 5°C then the temperature rises 
given in 21.10.1 and 2110.2 shall be increased by the amount calculated from the following expression: 

Increase in Rise = {40°C - Marked Ambient} x { 1 - [Reference Temperature - (40°C + Temperature 
Rise Limit)] / 80°C} 

Where: 





Class of Insulation System 






A B F 


H 


Reference Temperature for 21 .1 0. 1 , 
Degrees C 

Reference Temperature for 21.10.2, 
Degrees C 


105 130 155 
115 140 165 


180 
190 



*NOTE— This requirement does not include water-cooled machines. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21 , Page 1 1 

1 Temperature Rise Limit = maximum allowable temperature rise according to 21.10.1 and 21.10.2 

For example: A 1 .0 service factor rated motor with a Class F insulation system and using resistance 
as the method of determining the rated temperature rise is marked for use in an ambient with a 
maximum temperature of 25°C. From the Table above the Reference Temperature is 155°C and 
from 20.10.1 the Temperature Rise Limit is 105°C. The allowable Increase in Rise to be added to 
the Temperature Rise Limit is then: 

/ncrease/nR/se^4Q°C-25°c}xL 7550C -^ C + tQ50C )Uf3 C 
1 ; l[ 80°C Ij 

The total allowable Temperature Rise by Resistance above a maximum of a 25°C ambient is then 
equal to the sum of the Temperature Rise Limit from 20.10.1 and the calculated Increase in Rise. 
For this example that total is 105°C + 13°C = 1 18°C. 

21.11 TORQUES 1 

21.11.1 General 

The locked-rotor, pull-in, and pull-out torques, with rated voltage and frequency applied, shall be not less 
than the values shown in Table 21-5. The motors shall be capable of delivering the pull-out torque for at 
least 1 minute. 

21.11.2 Motor Torques When Customer Supplies Load Curve 

When the load curve is provided by the customer, the motor developed torque shall exceed the load 
torque by a minimum of 10% of motor rated torque at all locations throughout the speed range up the 
motor pull-in torque point for any starting condition specified by customer, (refer to 21.17.2). A torque 
margin of lower than 10% is subject to individual agreement between motor manufacturer and user. 
Pull - out torque shall be 150% at rated voltage, rated frequency with rated exitation current applied. 

Torque values as specified in Table 21-5 do not apply. 

21.12 NORMAL WK 2 OF LOAD 2 

Experience has shown that the pull-in torque values in Table 21-5 are adequate when the load inertia 
does not exceed the values of Table 21-6. The values of load inertia have been calculated using the 
following empirical formula: 

M / m/, 2 *, w °- 375 x (horsepower rating) 1 - 15 
Normal Wk* of load = ■ v ; - 



(speed in rpm / 1000) 2 



1 Values of torque apply to salient-pole machines. Values of torque for cylindrical rotor machines are subject to individual negotiation 
between manufacturer and user. 

2 Values of normal Wk 2 of load apply to salient-pole machines. Values of normal Wk 2 for cylindrical-rotor machines are subject to 
individual negotiation between manufacturer and user. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 12 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 







Table 21-5 
TORQUE VALUES 








Hp 


Power Factor 


Torques, 


Percent of Rated Full-Load 


Torque 


Speed, Rpm 


Locked-Rotor 


Pull-In (Based on 
Normal Wk 2 of Load)*t 


Pull-Outt 


500 to 1800 


200 and below 


1.0 




100 


100 


150 




150 and below 


0.8 




100 


100 


175 




250 to 1000 


1.0 




60 


60 


150 




200 to 1000 


0.8 




60 


60 


175 




1250 and larger 


1.0 




40 


60 


150 






0.8 




40 


60 


175 


450 and below 


All ratings 


1.0 




40 


30 


150 






0.8 




40 


30 


200 



*Values of normal Wk 2 of load are given in 21.12. 
fWith rated excitation current applied, 

21.13 NUMBER OF STARTS 1 

21.13.1 Starting Capability 

Synchronous motors shall be capable of making the following starts, providing the Wk 2 of the load, the 
load torque during acceleration, the applied voltage, and the method of starting are those for which the 
motor was designed: 

a. Two starts in succession, coasting to rest between starts, with the motor initially at ambient 
temperature 

b. One start with the motor initially at a temperature not exceeding its rated load operating 
temperature 

21.13.2 Additional Starts 

If additional starts are required, it is recommended that none be made until all conditions affecting 
operation have been thoroughly investigated and the apparatus examined for evidence of excessive 
heating. It should be recognized that the number of starts should be kept to a minimum since the life of 
the motor is affected by the number of starts. 

21.13.3 Information Plate 

When requested by the purchaser, a separate starting information plate will be supplied on the motor. 

21.14 EFFICIENCY 

Efficiency and losses shall be determined in accordance with IEEE Std 115. The efficiency shall be 
determined at rated output, voltage, frequency, and power factor. 

The following losses shall be included in determining the efficiency: 



a. 


I 2 R loss of armature 


b. 


l 2 R loss of field 


c. 


Core loss 


d. 


Stray-load loss 



1 The number of starts applies to salient-pole machines. The number of starts for cylindrical-rotor machines is subject to individual 
negotiation between manufacturer and user. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21, Page 13 

e. Friction and windage loss 1 

f. Exciter loss if exciter is supplied with and driven from the shaft of the machine 

Power required for auxiliary items, such as external pumps or fans, that are necessary for the operation 
of the motor shall be stated separately. 

In determining l 2 R losses at all loads, the resistance of each winding shall be corrected to a temperature 
equal to an ambient temperature of 25°C plus the observed rated-load temperature rise measured by 
resistance. When the rated-load temperature rise has not been measured, the resistance of the winding 
shall be corrected to the following temperature: 



Class of Insulation system Temperature, Degrees C 

A 75 

B 95 

F 115 

H 130 

If the rated temperature rise is specified as that of a lower class of insulation system, the temperature for 
resistance correction shall be that of the lower insulation class. 

21.15 OVERSPEED 

Synchronous motors shall be so constructed that, in an emergency not to exceed 2 minutes, they will 
withstand without mechanical damage overspeeds above synchronous speed in accordance with the 
following table. During this overspeed condition the machine is not electrically connected to the supply. 

Synchronous Speed, Rpm Overspeed, Percent of Synchronous Speed 

1500 and over 20 

1499 and below 25 



21.16 OPERATION AT OTHER THAN RATED POWER FACTORS 

21.16.1 Operation of an 0.8 Power-factor Motor at 1 .0 Power-factor 

For an 0.8-power factor motor which is to operate at 1 .0 power factor, with normal 0.8-power factor 
armature current and with field excitation reduced to correspond to that armature current at 1 .0 power 
factor, multiply the rated horsepower and torque values of the motor by the following constants to obtain 
horsepower at 1.0 power factor and the torques in terms of the 1 .0-power factor horsepower rating. 



Horsepower 


1.25 


Locked-rotor torque 


0.8 


Pull-in torque 


0.8 


Pull-out torque (approx.) 


0.6 



For example, consider a 1000-horsepower 0.8-power factor motor which has a locked-rotor torque of 100 
percent, a pull-in torque of 100 percent, and a pull-out torque of 200 percent and which is to be operated 
at 1 .0 power factor. In accordance with the foregoing, this motor would be operated at 1250 horsepower, 
1.0 power factor, 80 percent locked-rotor torque (based upon 1250 horse power), 80 percent pull-in 
torque (based upon 1250 horsepower) and a pull-out torque of approximately 120 percent (based upon 
1250 horsepower). 



In the case of motors which are furnished with thrust bearings, only that portion of the thrust bearing loss produced by the motor 
itself shall be included in the efficiency calculation. Alternatively, a calculated value of efficiency, including bearing loss due to 
external thrust load, may be specified. 

In the case of motors which are furnished with less than a full set of bearings, friction and windage losses which are representative 
of the actual installation shall be determined by (1) calculation or (2) experience with shop test bearings and shall be included in the 
efficiency calculations. 



» Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section lit 

Part 21, Page 14 LARGE MACHINES— SYNCHRONOUS MOTORS 

21.16.2 Operation of a 1 .0 Power-factor Motor at 0.8 Power-factor 

For a 1 .0-power factor motor which is to operate at 0.8 power factor, with normal 1 .0-power factor field 
excitation and the armature current reduced to correspond to that excitation, multiply the rated 
horsepower and torque values of the motor by the following constants to obtain the horsepower at 0.8- 
power factor and the torques in terms of the 0.8 power factor horsepower rating. 



Horsepower 


0.35 


Locked-rotor Torque 


2.85 


Pull-in torque 


2.85 


Pull-out torque (approx.) 


2.85 



For example, consider a 1000-horsepower 1. 0-power factor motor which has a locked-rotor torque of 100 
percent, a pull-in torque of 100 percent, and a pull-out torque of 200 percent and which is to be operated 
at 0.8-power factor. In accordance with the foregoing, this motor could be operated at 350 horsepower, 
0.8-power factor, 285 percent locked-rotor torque (based upon 350 horsepower), 285 percent pull-in 
torque (based upon 350 horsepower) and a 570 percent pull-out torque (based upon 350 horsepower). 

21.17 VARIATIONS FROM RATED VOLTAGE AND RATED FREQUENCY 

21.17.1 Running 

Motors shall operate successfully in synchronism, rated exciting current being maintained, under running 
conditions at rated load with a variation in the voltage or the frequency up to the following: 

a. Plus or minus 10 percent of rated voltage, with rated frequency 

b. Plus or minus 5 percent of rated frequency, with rated voltage 

c. A combined variation in voltage and frequency of 10 percent (sum of absolute values) of the rated 
values, provided the frequency variation does not exceed plus or minus 5 percent of rated 
frequency 

Performance within these voltage and frequency variations will not necessarily be in accordance with the 
standards established for operation at rated voltage and frequency. 

21.17.2 Starting 

The limiting values of voltage and frequency under which a motor will successfully start and synchronize 
depend upon the margin between the locked-rotor and pull-in torques of the motor at rated voltage and 
frequency and the corresponding requirements of the load under starting conditions. Since the locked- 
rotor and pull-in torques of a motor are approximately proportional to the square of the voltage and 
inversely proportional to the square of the frequency, it is generally desirable to determine what voltage 
and frequency variations will actually occur at each installation, taking into account any voltage drop 
resulting from the starting current drawn by the motor. This information and the torque requirements of 
the driven machine determine the values of locked-rotor and pull-in torque at rated voltage and frequency 
that are adequate for the application. 

21.18 OPERATION OF SYNCHRONOUS MOTORS FROM VARIABLE-FREQUENCY POWER 
SUPPLIES 

Synchronous motors to be operated from solid-state or other types of variable-frequency power supplies 
for adjustable-speed-drive applications may require individual consideration to provide satisfactory 
performance. Especially for operation below rated speed, it may be necessary to reduce the motor torque 
load below the rated full-load torque to avoid overheating the motor. The motor manufacturer should be 
consulted before selecting a motor for such applications. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21, Page 15 













Table 21-6 


















NORMAL Wk 2 OF LOAD IN LB-FT 2 








Speed, Rpm 


Hp 


1800 


1200 


900 


720 


600 


514 


450 


400 


360 


327 


20 


3.63 


8.16 


14.51 


22.7 


32.7 


44.4 


58.0 


73.5 


90.7 


109.7 


25 


4.69 


10.55 


18.76 


29.3 


42.2 


57.4 


75.0 


95.0 


117.2 


141.9 


30 


5.78 


13.01 


23.1 


36.1 


52.0 


70.8 


92.5 


117.1 


144.6 


174.9 


40 


8.05 


18.11 


32.2 


50.3 


72.5 


98.6 


123.8 


163.0 


201 


244 


50 


10.41 


23.4 


41.6 


65.0 


93.7 


127.5 


166.5 


211 


260 


315 


60 


12.83 


28.9 


51.3 


80.2 


115.5 


157.2 


205 


260 


321 


388 


75 


16.59 


37.3 


66.4 


103.7 


149.3 


203 


265 


336 


415 


502 


100 


23.1 


52.0 


92.4 


144.3 


208 


283 


369 


468 


577 


699 


125 


29.8 


67.2 


119.3 


186.6 


269 


366 


478 


604 


746 


903 


150 


36.8 


82.8 


147.2 


230 


331 


451 


589 


745 


920 


1114 


200 


51.2 


115.3 


205 


320 


461 


628 


820 


1038 


1281 


1550 


250 


66.2 


149.0 


265 


414 


596 


811 


1060 


1341 


1656 


2000 


300 


81.7 


183.8 


327 


511 


735 


1001 


1307 


1654 


2040 


2470 


350 


97.5 


219 


390 


610 


878 


1195 


1561 


1975 


2440 


2950 


400 


113.7 


256 


455 


711 


1024 


1393 


1820 


2300 


2840 


3440 


450 


130.2 


293 


521 


814 


1172 


1595 


2080 


2640 


3260 


3940 


500 


147.0 


331 


588 


919 


1323 


1801 


2350 


2980 


3670 


4450 


600 


181.3 


408 


725 


1133 


1632 


2220 


2900 


3670 


4530 


5480 


700 


216 


487 


866 


1353 


1948 


2650 


3460 


4380 


5410 


6550 


800 


252 


568 


1009 


1577 


2270 


3090 


4040 


5110 


6310 


7630 


900 


289 


650 


1156 


1806 


2600 


3540 


4620 


5850 


7220 


8740 


1000 


326 


734 


1305 


2040 


2940 


4000 


5220 


6610 


8160 


9870 


1250 


422 


949 


1687 


2640 


3790 


5160 


6750 


8540 


10540 


12750 


1500 


520 


1170 


2080 


3250 


4680 


6370 


8320 


10530 


13000 


15730 


1750 


621 


1397 


2480 


3880 


5590 


7610 


9930 


12570 


15520 


18780 


2000 


724 


1629 


2900 


4520 


6510 


8870 


11580 


14660 


18100 


21900 


2250 


829 


1865 


3320 


5180 


7460 


10150 


13260 


16780 


20700 


25100 


2500 


936 


2110 


3740 


5850 


8420 


11460 


14970 


18950 


23400 


28300 


3000 


1154 


2600 


4620 


7210 


10390 


14140 


18460 


23400 


28800 


34900 


3500 


1378 


3100 


5510 


8610 


12400 


16880 


22000 


27900 


34400 


41700 


4000 


1606 


3610 


6430 


10040 


14460 


19680 


25700 


32500 


40200 


48600 


4500 


1839 


4140 


7360 


11500 


16550 


22500 


29400 


37200 


46000 


55600 


5000 


2080 


4670 


8310 


12980 


18690 


25400 


33200 


42000 


51900 


62800 


5500 


2320 


5210 


9270 


14480 


20900 


28400 


37100 


46900 


57900 


70100 


6000 


2560 


5760 


10240 


16000 


23000 


31400 


41000 


51900 


64000 


77500 


7000 


3060 


6880 


12230 


19110 


27500 


37500 


48900 


61900 


76400 


92500 


8000 


3560 


8020 


14260 


22300 


32100 


43700 


57000 


72200 


89100 


107800 


9000 


4080 


9180 


16330 


25500 


36700 


50000 


65300 


82700 


102000 


123500 


10000 


4610 


10370 


18430 


28800 


41500 


56400 


73700 


93300 


115200 


139400 



(Continued) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 16 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



Table 21-6 (Continued) 













Speed, Rpm 










Hp 


300 


277 


257 


240 


225 


200 


180 


164 


150 


20 


130.6 


153.3 


177.8 


204 


232 


294 


363 


439 


522 


25 


168.8 


198.1 


230 


264 


300 


380 


469 


567 


675 


30 


208 


244 


283 


325 


370 


468 


578 


700 


833 


40 


290 


340 


395 


453 


515 


652 


805 


974 


1159 


50 


375 


440 


510 


585 


666 


843 


1041 


1259 


1499 


60 


462 


542 


629 


721 


821 


1040 


1283 


1553 


1848 


75 


597 


701 


813 


933 


1062 


1344 


1659 


2010 


2390 


100 


831 


976 


1132 


1299 


1478 


1871 


2310 


2790 


3330 


125 


1075 


1261 


1463 


1679 


1910 


2420 


2980 


3610 


4300 


150 


1325 


1555 


1804 


2070 


2360 


2980 


3680 


4450 


5300 


200 


1845 


2170 


2510 


2880 


3280 


4150 


5120 


6200 


7380 


250 


2380 


2800 


3250 


3730 


4240 


5370 


6620 


8010 


9540 


300 


2940 


3450 


4000 


4600 


5230 


6620 


8170 


9880 


11760 


350 


3510 


4120 


4780 


5490 


6240 


7900 


9750 


11800 


14050 


400 


4090 


4800 


5570 


6400 


7280 


9210 


11370 


13760 


16380 


450 


4690 


5500 


6380 


7320 


8330 


10550 


13020 


15760 


18750 


500 


5290 


6210 


7200 


8270 


9410 


11910 


14700 


17790 


21200 


600 


6530 


7660 


8880 


10200 


11600 


14680 


18130 


21900 


26100 


700 


7790 


9140 


10610 


12180 


13850 


17530 


21600 


26200 


31200 


800 


9090 


10660 


12370 


14200 


16150 


20400 


25200 


30500 


36300 


900 


10400 


12210 


14160 


16260 


18490 


23400 


28900 


35000 


41600 


1000 


11740 


13780 


15980 


18350 


20900 


26400 


32600 


39500 


47000 


1250 


15180 


17810 


20700 


23700 


27000 


34200 


42200 


51000 


60700 


1500 


18720 


22000 


25500 


29200 


33300 


42100 


52000 


62900 


74900 


1750 


22400 


26200 


30400 


34900 


39700 


50300 


62100 


75100 


89400 


2000 


26100 


30600 


35500 


40700 


46300 


58600 


72400 


87600 


104200 


2250 


29800 


35000 


40600 


46600 


53000 


67100 


82900 


100300 


119400 


2500 


33700 


39500 


45800 


52600 


59900 


75800 


93600 


113200 


134700 


3000 


41500 


48800 


56500 


64900 


73900 


93500 


115400 


139600 


166200 


3500 


49600 


58200 


67500 


77500 


88200 


111600 


137800 


166700 


198400 


4000 


57800 


67900 


78700 


90400 


102800 


130100 


160600 


194400 


231000 


4500 


66200 


77700 


90100 


103500 


117700 


149000 


183900 


223000 


265000 


5000 


74700 


87700 


101700 


116800 


132900 


168200 


208000 


251000 


299000 


5500 


83400 


97900 


113500 


130300 


148300 


187700 


232000 


280000 


334000 


6000 


92200 


108200 


125500 


144000 


163900 


207000 


256000 


310000 


369000 


7000 


110100 


129200 


149800 


172000 


195700 


248000 


306000 


370000 


440000 


8000 


128300 


150600 


174700 


201000 


228000 


289000 


356000 


431000 


513000 


9000 


146900 


172500 


200000 


230000 


261000 


331000 


408000 


494000 


588000 


10000 


165900 


194700 


226000 


259000 


295000 


373000 


461000 


558000 


664000 




















(Continued) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part21,Page17 













Speed, Rpm 










Hp 


138 


129 


120 


109 


100 


95 


90 


86 


80 


20 


613 


711 


816 


988 


1175 


1310 


1451 


1600 


1837 


25 


793 


919 


1055 


1277 


1519 


1693 


1876 


2070 


2370 


30 


977 


1134 


1301 


1575 


1874 


2090 


2310 


2550 


2930 


40 


1361 


1578 


1811 


2190 


2610 


2910 


3220 


3550 


4080 


50 


1759 


2040 


2340 


2830 


3370 


3760 


4160 


4590 


5270 


60 


2170 


2520 


2890 


3490 


4160 


4630 


5130 


5660 


6500 


75 


2800 


3250 


3760 


4520 


5370 


5990 


6640 


7320 


8400 


100 


3900 


4530 


5200 


6290 


7480 


8340 


9240 


10180 


11690 


125 


5040 


5850 


6720 


8130 


9670 


10780 


11940 


13160 


15110 


150 


6220 


7220 


8280 


10020 


11930 


13290 


14720 


16230 


18640 


200 


8660 


10040 


11530 


13950 


16600 


18500 


20500 


22600 


25900 


250 


11190 


12980 


14900 


18030 


21500 


23900 


26500 


29200 


33500 


300 


13810 


16010 


18380 


22200 


26500 


29500 


32700 


36000 


41400 


350 


16480 


19120 


21900 


26600 


31600 


35200 


39000 


43000 


49400 


400 


19220 


22300 


25600 


31000 


36800 


41100 


45500 


50200 


57600 


450 


22000 


25500 


29300 


35500 


42200 


47000 


52100 


57400 


65900 


500 


24800 


28800 


33100 


40000 


47600 


53100 


58800 


64800 


74400 


600 


30600 


35500 


40800 


49400 


58700 


65400 


72500 


79900 


91800 


700 


36600 


42400 


48700 


58900 


70100 


78100 


86600 


95500 


109600 


800 


42700 


49500 


56800 


68700 


81800 


91100 


100900 


111300 


127800 


900 


48800 


56600 


65000 


78700 


93600 


104300 


115600 


127400 


146300 


1000 


51000 


63900 


73400 


88800 


105700 


117800 


130500 


143900 


165100 


1250 


71300 


82600 


94900 


114800 


136600 


152200 


168700 


185900 


213000 


1500 


87900 


101900 


117000 


141600 


168500 


187700 


208000 


229000 


263000 


1750 


104900 


121700 


139700 


169000 


201000 


224000 


248000 


274000 


314000 


2000 


122300 


141900 


162900 


197100 


235000 


261000 


290000 


319000 


366000 


2250 


140100 


162500 


186500 


226000 


269000 


299000 


332000 


366000 


420000 


2500 


158100 


183400 


211000 


255000 


303000 


338000 


374000 


413000 


474000 


3000 


195000 


226000 


260000 


314000 


374000 


417000 


462000 


509000 


584000 


3500 


233000 


270000 


310000 


375000 


446000 


497000 


551000 


608000 


697000 


4000 


271000 


315000 


361000 


437000 


520000 


580000 


643000 


708000 


813000 


4500 


311000 


361000 


414000 


501000 


596000 


664000 


736000 


811000 


931000 


5000 


351000 


407000 


467000 


565000 


673000 


750000 


831000 


916000 


1051000 


5500 


392000 


454000 


521000 


631000 


751000 


836000 


927000 


1022000 


1173000 


6000 


433000 


502000 


576000 


697000 


830000 


924000 


1024000 


1129000 


1296000 


7000 


517000 


599000 


688000 


832000 


991000 


1104000 


1223000 


1348000 


1548000 


8000 


602000 


699000 


802000 


971000 


1155000 


1287000 


1426000 


1572000 


1805000 


9000 


690000 


800000 


918000 


1111000 


1323000 


1474000 


1633000 


1800000 


2070000 


10000 


779000 


903000 


1037000 


1254000 


1493000 


1663000 


1843000 


2030000 


2330000 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 18 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



21.19 SPECIFICATION FORM FOR SLIP-RING SYNCHRONOUS MOTORS 

The specification form for listing performance data on synchronous motors with slip rings shall be as 

follows: 

Date __^ 







SLIP-RING SYNCHRONOUS MOTOR RATING 






Hp 
(Output) 


Power 
Factor 


kVA 


Rpm 


Number 
of Poles 


Phase 


Hertz 


Volts 


Amperes 
(Approx.) 


Frame 



Description: 



Hp 
(Output) 


Temperature Rise Guarantees 
Temperature Rise (Degrees C) Not to Exceed 


Excitation Requirements (Maximum) 


Armature Winding 


Field Winding 




Resistance 


Embedded 
Temperature Detector 


Resistance 


kW 


Exciter Rated 
Voltage 















Rating and temperature rise are based on cooling air not exceeding 40°C and altitude not exceeding 3300 feet (1000 meters). High- 
potential test in accordance with MG1-21 .22. 



Torque and kVA (Expressed in terms of above full-load rating with 100-percent voltage applied) 


Locked- Rotor 
Code Letter 


Percent Locked- 
Rotor kVA 


Percent Locked- 
Rotor Torque 


Pull-In Torque 


Percent Pull-Out Torque 

Sustained for 1 Minute With 

Rated-Load Excitation 


Percent 
Torque 


Maximum Load Wk 2 - 
Ib.ft 2 















If started on reduced voltage, the starting torque of the motor will be reduced approximately in proportion to the square of the 
reduced voltage applied. 



Minimum Efficiencies 


Hp 
(Output) 


Power 
Factor 


Full 
Load 


3/4 Load 


1/2 Load 






















.Hlnn l 2 D IrtC 







Approximate Weight, Pounds 


Total 
Net 


Rotor 
Net 


Heaviest 

Part for 

Crane Net 


Total 
Shipping 











Id windings at °C, core losses, stray-load losses, and 

friction and windage losses.* Exciter loss is included if supplied with and driven from shaft of machine. Field rheostat losses are not 
included. 



*a. In the case of a motor furnished with a thrust bearing, only that portion of the thrust bearing loss produced by the motor itself is 
included in the efficiency calculation. 

b. In the case of a motor furnished with less than a full set of bearings, friction and windage losses representative of the actual 
installation are included as determined by (a) calculation or (b) experience with shop test bearings. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21, Page 19 



21 .20 SPECIFICATION FORM FOR BRUSHLESS SYNCHRONOUS MOTORS 

The specification form for listing performance data on brushless synchronous motors shall be as follows: 

Date 



BRUSHLESS SYNCHRONOUS MOTOR RATING 


Hp 
(Output) 


Power 
Factor 


kVA 


Rpm 


Number 
of Poles 


Phase 


Hertz 


Volts 


Amperes 
(Approx.) 


Frame 



Description: 





Temperature Rise Guarantees 

Temperature Rise 

(Degrees C) Not to Exceed 








Armature Winding 


Field 
Winding 


Excitation Requirements* (2) 
(Maximum) 


Hp 
(Output) 




Resistance 


Embedded 
Temperature Detector 


Resistance 


Watts 


Exciter Rated Field 
Voltage 




Motor 












Exciter* (1) 





















*For rotating transformer give (1) data for equivalent winding temperatures and (2) input kVA and voltage instead of excitation for 

exciter. 

Rating and temperature rise are based on cooling air not exceeding 40°C and altitude not exceeding 3300 feet (1000 meters). High- 
potential test in accordance with MG1-21.22. 



Torque and kVA (Expressed in terms of above full-load rating with 100-percent voltage applied) 


Locked-Rotor 
Code Letter 


Percent Locked- 
Rotor kVA 


Percent Locked- 
Rotor Torque 


Pull-In Torque 


Percent Pull-Out Torque 

Sustained for 1 Minute With 

Rated-Load Excitation 


Percent 
Torque 


Maximum Load 
Wk^lb.ft 2 















If started on reduced voltage, the starting torque of the motor will be reduced approximately in proportion to the square of the 
reduced voltage applied. 



Minimum Efficiencies 


Hp 
(Output) 


Power 
Factor 


Full 
Load 


3/4 Load 


1/2 Load 

















Approximate Weight, Pounds 


Total 
Net 


Rotor 
Net 


Heaviest 

Part for 

Crane Net 


Total 
Shipping 











Efficiencies are determined by including I R losses of armature and field windings at _ 



_ °C, core losses, stray-load losses, and 
friction and windage losses.* Exciter loss is included if supplied with and driven from shaft of machine. Field rheostat losses are not 
included. 

*a. In the case of a motor furnished with a thrust bearing, only that portion of the thrust bearing loss produced by the motor itself is 
included in the efficiency calculation. 

b. In the case of a motor furnished with less than a full set of bearings, friction and windage losses representative of the actual 
installation are included as determined by (a) calculation or (b) experience with shop test bearings. 



i Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 21 , Page 20 LARGE MACHINES— SYNCHRONOUS MOTORS 

21.21 ROUTINE TESTS 

21 .21 .1 Motors Not Completely Assembled in the Factory 

The following tests shall be made on all motors which are not completely assembled in the factory, 
including those furnished without a shaft, or a complete set of bearings, or neither: 

a. Resistance of armature and field windings 

b. Polarity of field coils 

c. High-potential test in accordance with 21 .22 

21 .21 .2 Motors Completely Assembled in the Factory 

The following tests shall be made on motors which are completely assembled in the factory and furnished 
with a shaft and a complete set of bearings: 



a. Resistance of armature and field windings 

b. Check no-load field current at normal voltage and frequency. 1 

c. High-potential test in accordance with 21 .22. 

21 .22 HIGH-POTENTIAL TESTS 

21.22.1 Safety Precautions and Test Procedure 

See 3.1. 

21 .22.2 Test Voltage — Armature Windings 

The test voltage for all motors shall be an alternating voltage whose effective value is 1000 volts plus 
twice the rated voltage of the machine. 2 

21.22.3 Test Voltage— Field Windings, Motors with Slip Rings 

The test voltage for all motors with slip rings shall be an alternating voltage whose effective value is as 
follows: 

a. Motor to be started with its field short-circuited or closed through an exciting armature; ten times 
rated excitation voltage but in no case less than 2500 volts nor more than 5000 volts. 

b. Motor to be started with a resistor in series with the field winding; twice the rms value of the IR 
drop across the resistor but in no case less than 2500 volts, the IR drop being taken as the 
product of the resistance and the current which would circulate in the field winding if short- 
circuited on itself at the specified starting voltage. 

21 .22.4 Test Voltage— Assembled Brushless Motor Field Winding and Exciter Armature Winding 

The test voltage for all assembled brushless motor field windings and exciter armature windings shall be 
an alternating voltage whose effective value is as follows: 

a. Rated excitation voltage < 350 volts direct-current; ten times the rated excitation voltage but in no 
case less than 1500 volts 

b. Rated excitation voltage > 350 volts direct-current; 2800 volts plus twice the rated excitation 
voltage 



1 On motors having brushless excitation systems, check instead the exciter field current at no-load with normal voltage and 
frequency on the motor. 

2 A direct instead of an alternating voltage is sometimes used for high-potential tests on primary windings of machines rated 6000 
volts or higher. In such cases, a test voltage equal to 1 7 times the alternating-current test voltage (effective value) as given in 
21.22.2 and 21.22.3 is recommended. Following a direct-voltage high-potential test, the tested winding should be thoroughly 
grounded. The insulation rating of the winding and the test level of the voltage applied determine the period of time required to 
dissipate the charge and, in many cases, the ground should be maintained for several hours to dissipate the charge to avoid hazard 
to personnel. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



I 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21 , Page 21 

c. Alternatively, the brushless exciter rotor (armature) shall be permitted to be tested at 1000 volts 
plus twice the rated nonrectified alternating-current voltage but in no case less than 1500 volts. 

The brushless circuit components (diodes, thyristors, etc.) on an assembled brushless exciter and 
synchronous machine field winding shall be short-circuited (not grounded) during the test. 

21 .22.5 Test Voltage— Brushless Exciter Field Winding 

The test voltage for all brushless exciter field windings shall be an alternating voltage whose effective 
value is as follows: 

a. Rated excitation voltage < 350 volts direct-current; ten times the rated excitation voltage but in no 
case less than 1500 volts 

b. Rated excitation voltage > 350 volts direct-current; 2800 volts plus twice the rated excitation 
voltage 

c. Exciters with alternating-current excited stators (fields) shall be tested at 1000 volts plus twice the 
alternating-current rated voltage of the stator 

21.23 MACHINE SOUND 
See 20.19. 

21.24 MECHANICAL VIBRATION 
See Part 7. 

MANUFACTURING 

21 .25 NAMEPLATE MARKING 

The following information shall be given on nameplates. For abbreviations, see 1.79. For some examples 
of additional information that may be included on the nameplate see 1 .70.2. 

a. Manufacturer's type and frame designation 

b. Horsepower output 

c. Time rating 

d. Temperature rise 1 

e. Rpm at full load 

f. Frequency 

g. Number of phases 
h. Voltage 

i. Rated amperes per terminal 

j. Rated field current 2 

k. Rated excitation voltage 2 

I. Rated power factor 

m. Code letter (see 10.37) 

n. Service factor 



1 As an alternative marking, this item shall be permitted to be replaced by the following. 

a. Maximum ambient temperature for which the motor is designed (see 21 .10.3). 

b. Insulation system designation (if armature and field use different classes of insulation systems, both insulation systems shall 
be given, with that for the armature being given first). 

2 Applies to exciter in case of brushless machine. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 21 , Page 22 LARGE MACHINES— SYNCHRONOUS MOTORS 

Some examples of additional information that may be included on the nameplate are: 

o. Enclosure or IP code 

p. Manufacturer's name, mark, or logo 

q. Manufacturer's plant location 

r. Serial number or date of manufacture 

21.26 MOTOR TERMINAL HOUSINGS AND BOXES 

21.26.1 Box Dimensions 

When motors covered by this Part 21 are provided with terminal housings for line cable connections, 1 the 
minimum dimension and usable volume shall be as indicated in Table 21-7 for Type I terminal housings 
or Figure 21-1 for Type II terminal housings. 

Unless otherwise specified, when motors are provided with terminal housings, a Type I terminal housing 
shall be supplied. 

21.26.2 Accessory Lead Terminations 

For motors rated 601 volts and higher, accessory leads shall terminate in a terminal box or boxes 
separate from the motor terminal housing. As an exception, current and potential transformers located in 
the motor terminal housing shall be permitted to have their secondary connections terminated in the 
motor terminal housing if separated from the motor leads by a suitable physical barrier. 

21.26.3 Lead Terminations of Accessories Operating at 50 Volts of Less 

For motors rated 601 volts and higher, the termination of leads of accessory items normally operating at a 
voltage of 50 volts (rms) or less shall be separated from leads of higher voltage by a suitable physical 
barrier to prevent accidental contact or shall be terminated in a separate box. 



1 Terminal housings containing surge capacitors, surge arresters, current transformers, or potential transformers require individual 
consideration. 

© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21, Page 23 



Table 21-7 
TYPE I TERMINAL HOUSING UNSUPPORTED AND INSULATED TERMINATIONS 





Maximum Full-Load 


Minimum Usable 


Minimum Internal 


Minimum Centerline 


Voltage 


Current 


Volume, Cubic Inches 


Dimension, Inches 


Distance,* Inches 


0-600 


400 


900 


8 






600 


2000 


8 






900 


3200 


10 






1200 


4600 


14 




601-2400 


160 


180 


5 






250 


330 


6 






400 


900 


8 






600 


2000 


8 


12.6 




900 


3200 


10 


12.6 




1500 


5600 


16 


20.1 


2401-4800 


160 


2000 


8 


12.6 




700 


5600 


14 


16 




1000 


8000 


16 


20 




1500 


10740 


20 


25 




2000 


13400 


22 


28.3 


4801-6900 


260 


5600 


14 


16 




680 


8000 


16 


20 




1000 


9400 


18 


25 




1500 


11600 


20 


25 




2000 


14300 


22 


28.3 


6901-13800 


400 


4400 


22 


28.3 




900 


50500 


25 


32.3 




1500 


56500 


27.6 


32.3 




2000 


62500 


30.7 


32.3 



*Minimum distance from the entrance plate for conduit entrance to the centerline of machine leads. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 24 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



MOTOR 
ENCLOSURE 



\ 

^ v h* D - ■*-: 





SHIELD 

GROUND 

SCREW 














Minimum Dimensions (Inches) 








Motor 
















Voltage 


L 


W 


D 


ABC 


X 


E 


F 


460-575 


24 


18 


18 


9 1 / 2 8/2 4 


5 


2% 


4 


2300-4000 


26 


27 


18 


9/2 8/2 5/2 


8 


3/2 


5 


6600 


36 


30 


18 


9/2 8/2 6 


9 


4 


6 


13200 


48 


42 


25 


13/2 11/2 8V2 


13/2 


6 3 /4 


9/2 



Figure 21-1 
TYPE II MOTOR TERMINAL HOUSING STANDOFF-INSULATOR-SUPPORTED INSULATED OR 

UNINSULATED TERMINATIONS 

21.27 EMBEDDED DETECTORS 

See 20.28. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21, Page 25 

APPLICATION DATA 

21 .28 SERVICE CONDITIONS 

21.28.1 General 

Motors should be properly selected with respect to their service conditions, usual or unusual, both of 
which involve the environmental conditions to which the machine is subjected and the operating 
conditions. Machines conforming to this Part 21 are designed for operation in accordance with their 
ratings under usual service conditions. Some machines may also be capable of operating in accordance 
with their ratings under one or more unusual service conditions. Definite-purpose or special-purpose 
machines may be required for some unusual conditions. 

Service conditions, other than those specified as usual may involve some degree of hazard. The 
additional hazard depends upon the degree of departure from usual operating conditions and the severity 
of the environment to which the machine is exposed. The additional hazard results from such things as 
overheating, mechanical failure, abnormal deterioration of the insulation system, corrosion, fire, and 
explosion. 

Although experience of the user may often be the best guide, the manufacturer of the driven equipment 
and the motor manufacturer should be consulted for further information regarding any unusual service 
conditions which increase the mechanical or thermal duty on the machine and, as a result, increase the 
chances for failure and consequent hazard. This further information should be considered by the user, his 
consultants, or others most familiar with the details of the application involved when making the final 
decision. 

21 .28.2 Usual Service Conditions 

Usual service conditions include the following: 

a. An ambient temperature in the range of 0°C to 40°C, or when water cooling is used, in the range 
of 5°C to 40°C 

b. An altitude not exceeding 3300 feet (1000 meters) 

c. A location and supplementary enclosures, if any, such that there is no serious interference with 
the ventilation of the motor 

21 .28.3 Unusual Service Conditions 

The manufacturer should be consulted if any unusual service conditions exist which may affect the 
construction or operation of the motor. Among such conditions are: 

a. Exposure to: 

1. Combustible, explosive, abrasive, or conducting dusts 

2. Lint or very dirty operating conditions where the accumulation of dirt will interfere with normal 
ventilation 

3. Chemical fumes, flammable or explosive gases 

4. Nuclear radiation 

5. Steam, salt-laden air, or oil vapor 

6. Damp or very dry locations, radiant heat, vermin infestation, or atmospheres conducive to the 
growth of fungus 

7. Abnormal shock, vibration, or mechanical loading from external sources 

8. Abnormal axial or side thrust imposed on the motor shaft 

b. Operation where: 

| 1 . There is excessive departure from rated voltage or frequency, or both (see 21.17) 
2. The deviation factor of the alternating-current supply voltage exceeds 10 percent 

1 3. The alternating-current supply voltage is unbalanced by more than 1 percent (see 21 .29) 
4. Low noise levels are required 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 26 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



| 5. The power system is not grounded (see 21 .39). 

c. Operation at speeds other than rated speed (see 21.17) 

d. Operation in a poorly ventilated room, in a pit, or in an inclined position 

e. Operation where subjected to: 

1. Torsional impact loads 

2. Repetitive abnormal overloads 

3. Reversing or electric braking 

4. Frequent starting (see 21.13) 

5. Out-of-phase bus transfer 

21.29 EFFECTS OF UNBALANCED VOLTAGES ON THE PERFORMANCE OF POLYPHASE 
SYNCHRONOUS MOTORS 

When the line voltages applied to a polyphase synchronous motor are not equal, unbalanced currents in 
the stator windings will result. A small percentage voltage unbalance will result in a much larger 
percentage current unbalance. 

Voltages should be evenly balanced as closely as can be read on a voltmeter. If the voltages are 
unbalanced, the rated horsepower of polyphase synchronous motors should be multiplied by the factor 
shown in Figure 21-2 to reduce the possibility of damage to the motor. 1 Operation of the motor with more 
than a 5-percent voltage unbalance is not recommended. 



1.0 






































ERATING FA 
o c 
bo <c 


























































Q 

0.7 

















12 3 4 5 

PERCENT VOLTAGE UNBALANCE 

Figure 21-2 
POLYPHASE SYNCHRONOUS MOTOR DERATING FACTOR DUE TO UNBALANCED VOLTAGE 

When the derating curve of Figure 21-2 is applied for operation on unbalanced voltages, the selection 
and setting of the overload device should take into account the combination of the derating factor applied 
to the motor and the increase in current resulting from the unbalanced voltages. This is a complex 
problem involving the variation in motor current as a function of load and voltage unbalance in addition to 
the characteristics of the overload device relative to l ma ximumOr l average . In the absence of specific 
information it is recommended that overload devices be selected or adjusted, or both, at the minimum 
value that does not result in tripping for the derating factor and voltage unbalance that applies. When 
unbalanced voltages are anticipated, it is recommended that negative sequence current relays be 
installed or the overload devices be selected so as to be responsive to l ma ximum in preference to overload 
devices responsive to l aV erage 



The derating factor shown in Figure 21-2 is applicable only to motors with normal starting torque and normal locked-rotor current, 
i.e., motors typically intended for service with centrifugal pumps, fans, compressors, and so forth, where the required starting torque 
is less than 100 percent of rated full-load torque. For motors with other starting torque characteristics, or motors with specified limits 
on locked-rotor current, the motor manufacturer should be consulted. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21 , Page 27 



21 .29.1 Effect on Performance 

21 .29.1 .1 Temperature Rise 

The temperature rise of the motor operating at a particular load and percentage voltage unbalance will be 
greater than for the motor operating under the same conditions with balanced voltages. 

21. 29.1. 2 Currents 

The effect of unbalanced voltages on polyphase synchronous motors is equivalent to the introduction of a 
"negative-sequence voltage" having a rotation opposite to that occurring with balanced voltages. This 
negative sequence voltage produces an air gap flux rotating against the rotation of the rotor, tending to 
produce high currents. A small negative-sequence voltage may produce significant continuous current in 
the amortisseur (cage) winding, which normally carries little or no current when the motor is running in 
synchronism, along with slightly higher current in the stator winding. 

The negative-sequence current at normal operating speed with unbalanced voltages may be in the order 
of four to ten times the voltage unbalance. 

The locked-rotor current will be unbalanced to the same degree that the voltages are unbalanced but the 
locked-rotor kVA will increase only slightly. 

21 .29. 1.3 Torques 

The locked-rotor torque, pull-in torque, and pull-out torque are decreased when the voltage is 
unbalanced. If the voltage unbalance is extremely severe, the torques might not be adequate for the 
application. 

21 .29.2 Voltage Unbalance Defined 

The voltage unbalance in percent may be defined as follows. 

* nn max imum voltage deviation from average voltage 

percent voltage unbalance = 1 00 x - 

r average voltage 

EXAMPLE— With voltages of 2300, 2220, and 2185 the average is 2235, the maximum deviation from the average is 65, and 
the percent unbalance = 10 x 65/2235 = 2.9 percent. 

21.30 COUPLING END PLAY AND ROTOR FLOAT FOR HORIZONTAL MOTORS 

See 20.30. 

21 .31 BELT, CHAIN, AND GEAR DRIVE 

When motors are for belt, chain, or gear drive, the motor manufacturer should be consulted. 

21.32 PULSATING ARMATURE CURRENT 

When the driven load, such as that of reciprocating-type pumps, compressors, etc., requires a variable 
torque during each revolution, it is recommended that the combined installation have sufficient inertia in 
its rotating parts to limit the variations in motor armature current to a value not exceeding 66 percent of 
full-load current. 

NOTE— The basis for determining this variation should be by oscillograph measurement and not by ammeter readings. A line 
should be drawn on the oscillogram through the consecutive peaks of the current wave. This line is the envelope of the current 
wave. The variation is the difference between the maximum and minimum ordinates of this envelope. This variation should not 
exceed 66 percent of the maximum value of the rated full-load current of the motor. (The maximum value of the motor armature 
current to be assumed as 1.41 times the rated full-load current.) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 21, Page 28 LARGE MACHINES— SYNCHRONOUS MOTORS 



21.33 TORQUE PULSATIONS DURING STARTING OF SYNCHRONOUS MOTORS 

When operated at other than synchronous speed, all salient-pole synchronous motors develop a 
pulsating torque superimposed on the average torque. During starting and acceleration (with no field 
excitation applied), the frequency of the torque pulsations is at any instant equal to the per-unit slip times 
twice the line frequency. Thus, for a 60-hertz motor, the frequency of the torque pulsation varies from 120 
hertz at zero speed to zero hertz at synchronous speed. 

Any system consisting of inertias connected by shafting has one or more natural torsional frequencies. 
During acceleration by a salient-pole synchronous motor, any torsional natural frequency at or below 
twice line frequency will be transiently excited. 

When it is desired to investigate the magnitudes of the torques which are transiently imposed upon the 
shafting during starting, the instantaneous torque pulsations should be considered in addition to the 
average torque. 

21 .34 BUS TRANSFER OR RECLOSING 

Synchronous motors are inherently capable of developing transient current and torque considerably in 
excess of rated current and torque when exposed to an out-of-phase bus transfer or momentary voltage 
interruption and reclosing on the same power supply. The magnitude of this transient torque may range 
from 2 to 20 times rated torque and is a function of the machine, operating conditions, switching time, 
rotating system inertias and torsional spring constants, number of motors on the bus, etc. 

21 .34.1 Slow Transfer or Reclosing 

A slow transfer or reclosing is defined as one in which the length of time between disconnection of the 
motor from the power supply and reclosing onto the same or another power supply is equal to or greater 
than one and a half motor open-circuit alternating-current time constant. 

It is recommended that slow transfer or reclosing be used so as to limit the possibility of damaging the 
motor or driven (or driving) equipment, or both. This time delay permits a sufficient decay in rotor flux 
linkages so that the transient current and torque associated with the bus transfer or reclosing will remain 
within acceptable levels. When several motors are involved, the time delay should be based on one and a 
half times the longest open-circuit time constant of any motor on the system being transferred or 
reclosed. 

21 .34.2 Fast Transfer or Reclosing 

A fast transfer or reclosing is defined as one which occurs within a time period (typically between 5 and 
10 cycles) shorter than one and a half open circuit alternating-current time constant. In such cases 
transfer or reclosure should be timed to occur when the difference between the motor residual voltage 
and frequency, and the incoming system voltage and frequency will not result in damaging transients. 

The rotating masses of a motor-load system, connected by elastic shafts, constitutes a torsionally 
responsive mechanical system which is excited by the motor electromagnetic (air-gap) transient torque 
that consists of the sum of an exponentially decaying unidirectional component and exponentially 
decaying oscillatory components at several frequencies, including power frequency, slip frequency and 
twice slip frequency. The resultant shaft torques may be either attenuated or amplified with reference to 
the motor electromagnetic (air-gap) torque, and for this reason it is recommended that the 
electromechanical interactions of the motor, the driven equipment, and the power system be studied for 
any system where fast transfer or reclosing is used. 

The electrical and mechanical parameters required for such a study will be dependent upon the method 
of analysis and the degree of detail employed in the study. When requested, the motor manufacturer 
should furnish the following and any other information as may be required for the system study: 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III MG 1-2009 

LARGE MACHINES— SYNCHRONOUS MOTORS Part 21 , Page 29 

a. Synchronous, transient and subtransient reactances and time constants as well as resistances 

b. Wk 2 of the motor and exciter rotors 

c. A detailed shaft model with elastic data, masses, shaft lengths and diameters of different sections 

21.34.3 Bus Transfer Procedure 

For slow bus transfers, and for fast transfers if the study indicates that the motor will not remain in 
synchronism, the following procedures are recommended: 

a. Motor with slip rings— Remove the field excitation, reestablish conditions for resynchronizing and 
delay transfer or reclosing for one-and-one-half open circuit alternating-current time constants. 

b. Brushless motor— Remove the exciter field excitation, reestablish conditions for resynchronizing, 
and delay transfer or reclosing for one-and-one-half open circuit alternating time constants. 

21.35 CALCULATION OF NATURAL FREQUENCY OF SYNCHRONOUS MACHINES DIRECT- 
CONNECTED TO RECIPROCATING MACHINERY 

21.35.1 Undamped Natural Frequency 

The undamped natural frequency of oscillation of a synchronous machine connected to an infinite system 
is: 



fn = 



35200 P r *f 



n V Wk^ 
Where: 

f n = natural frequency in cycles per minute 
n = synchronous speed in revolutions per minute 
P r = synchronizing torque coefficient (see 21 .35.2) 
W = weight of all rotating parts in pounds 
k = radius of gyration of rotating parts in feet 

21.35.2 Synchronizing Torque Coefficient, P r 

When a pulsating torque is applied to its shaft, the synchronous machine rotor will oscillate about its 
average angular position in the rotating magnetic field produced by the currents in the stator. As a result 
of this oscillation, a pulsating torque will be developed at the air gap, a component of which is 
proportional to the angular displacement of the rotor from its average position. The proportionality factor 
is the synchronizing torque coefficient, P r . It is expressed in kilowatts, at synchronous speed, per 
electrical radian. 

21.35.3 Factors Influencing P r 

The value of P r , for a given machine, is dependent upon (1) the voltage and frequency of the power 
system, (2) the magnitude of the applied load, (3) the operating power factor, (4) the power system 
impedance, and (5) the frequency of the torque pulsations. It is recommended that, unless other 
conditions are specified, the value of P r submitted be that corresponding to operation at rated voltage, 
frequency, load, and power factor, with negligible system impedance and a pulsation frequency, in cycles 
per minute, equal to the rpm for synchronous motors and equal to one-half the rpm for synchronous 
generators. 

21.36 TYPICAL TORQUE REQUIREMENTS 

Typical torque requirements for various synchronous motor applications are listed in Table 21-8. In 
individual cases, lower values may be adequate or higher values may be required depending upon the 
design of the particular machine and its operating conditions. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 Section III 

Part 21, Page 30 LARGE MACHINES— SYNCHRONOUS MOTORS 

When using Table 21-8, the following should be noted: 

a. The locked-rotor and pull-in torque values listed are based upon rated voltage being maintained at 
the motor terminals during the starting period. If the voltage applied to the motor is less than the 
rated voltage because of a drop in line voltage or the use of reduced-voltage starting, the locked- 
rotor and pull-in torque values specified should be appropriately higher than the torque values at 
rated voltage. Alternatively, the locked-rotor and pull-in torque values listed in the table should be 
specified together with the voltage at the motor terminals for each torque value. 

b. The locked-rotor and pull-in torque values listed in Table 21-8 are also based upon the selection 
of a motor whose rating is such that the normal running load does not exceed rated horsepower. If 
a smaller motor is used, correspondingly higher locked-rotor and pull-in torques may be required. 

c. The pull-in torque developed by a synchronous motor is not a fixed value but varies over a wide 
range depending upon the Wk of its connected load. Hence, to design a motor which will 
synchronize a particular load, it is necessary to know the Wk 2 of the load as well as the pull-in 
torque. For the applications listed in Table 21-8, the Wk 2 of the load divided by the normal Wk 2 of 
load (see 21.12) will usually fall within the range of the values shown in the last column. Where a 
rotating member of the driven equipment operates at a speed different from that of the motor, its 
Wk 2 should be multiplied by the square of the ratio of its speed to the motor speed to obtain the 
equivalent inertia at the motor shaft. 

d. For some applications, torque values are listed for (a) starting with the driven machine unloaded in 
some manner and (b) starting without unloading of the driven machine. Even though the driven 
machine is normally unloaded for starting, the higher torque values required for starting under load 
may be justified since, with suitable control, this will allow automatic resynchronization following 
pull-out due to a temporary overload or voltage disturbance. 

e. The pull-out torque values listed in Table 21-8 take into account the peak loads typical of the 
application and include an allowance for usual variations in line voltage. Where severe voltage 
disturbances are expected and continuity of operation is important, higher values of puil-out torque 
may be justified. 



© Copyright 2009 by the National Electrical Manufacturers Association. 



Section III 

LARGE MACHINES— SYNCHRONOUS MOTORS 



MG 1-2009 
Part 21, Page 31 



Table 21-8 
TYPICAL TORQUE REQUIREMENTS FOR SYNCHRONOUS MOTOR APPLICATIONS 

Torques in Percent of Motor Ratio of Wk z 

Full-Load Torque of Load to 

l tem Locked- Normal Wk 2 of 

Np^ Application Rotor Pull-In Pull-Out Load 

1 Attrition mills (for grain processing) - starting unloaded 100 60 175 3-15 

2 Ball mills (for rock and coal) 140 110 175 2-4 

3 Ball mills (for ore) 150 110 175 1.5-4 

4 Banbury mixers 125 125 250 0.2-1 

5 Band mills 40 40 250 50-110 

6 Beaters, standard 125 100 150 3-15 

7 Beaters, breaker 125 100 200 3-15 

8 Blowers, centrifugal— starting with: 

a. Inlet or discharge valve closed 30 40-60* 150 3-30 

b. Inlet or discharge valve open 30 100 150 3-30 

9 Blowers, positive displacement, rotary - by-passed for starting 30 25 150 3-8 

10 Bowl mills (coal pulverizers) - starting unloaded 

a. Common motor for mill and exhaust fan 90 80 150 5-1 5 

b. Individual motor for mill 140 50 150 4-10 

1 1 Chippers - starting empty 60 50 250 10-100 

12 Compressors, centrifugal - starting with: 

a. Inlet or discharge valve closed 30 40-60* 150 3-30 

b. Inlet or discharge valve open 30 100 150 3-30 

13 Compressors, Fuller Company 

a. Starting unloaded (by-pass open) 60 60 150 0.5-2 

b. Starting loaded (by-pass closed) 60 100 150 0.5-2 

14 Compressors, Nash-Hyotr - starting unloaded 40 60 150 2-4 

See page 30 for notes applying to this table (Continued) 



© Copyright 2009 by the National Electrical Manufacturers Association. 



MG 1-2009 
Part 21, Page 32 



Section III 
LARGE MACHINES— SYNCHRONOUS MOTORS 



Table 21-8 (Continued) 



Item 

No. Application 

15 Compressors, reciprocating - starting unloaded 

a. Air and gas 

b. Ammonia (discharge pressure 100-250 psi) 

c. Freon 

16 Crushers, Bradley-Hercules - starting unloaded 

17 Crushers, cone - starting unloaded 

18 Crushers, gyratory - starting unloaded 

19 Crushers, jaw - starting unloaded 

20 Crushers, roll - staring unloaded 

21 Defibrators (see Beaters, standard) 

22 Disintegrators, pulp (see Beaters, standard) 

23 Edgers 

24 Fans, centrifugal (except sintering fans) - starting with: 

a. Inlet or discharge valve closed 

b. Inlet or discharge valve open 

25 Fans, centrifu