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CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

TABLE OF CONTENTS

3.1 INTRODUCTION ........................................................................................................... 3-1

3.2 MARKET ASSESSMENT.............................................................................................. 3-1

3.2.1 Electric Motor Definitions................................................................................... 3-1

3.2.1.1 Expanded Scope Definitions................................................................. 3-4

3.2.2 Equipment Class Groups and Equipment Classes............................................. 3-12

3.2.2.1 Electric Motor Design......................................................................... 3-14

3.2.2.2 Fire Pump Electric Motors.................................................................. 3-15

3.2.2.3 Horsepower Rating ............................................................................. 3-15

3.2.2.4 Pole configuration............................................................................... 3-16

3.2.2.5 Enclosure type..................................................................................... 3-16

3.2.3 Expanded Scope of Coverage ............................................................................ 3-19

3.2.4 Electric Motor Shipments.................................................................................. 3-24

3.2.4.1 NEMA Design Type ........................................................................... 3-24

3.2.4.2 Horsepower Ratings............................................................................ 3-25

3.2.4.3 Pole Configuration.............................................................................. 3-26

3.2.4.4 Enclosure Types.................................................................................. 3-27

3.2.5 Manufacturers and Market Share....................................................................... 3-28

3.2.5.1 Small Businesses................................................................................. 3-29

3.2.6 Application and Performance of Existing Equipment ....................................... 3-29

3.2.7 Trade Associations............................................................................................. 3-29

3.2.7.1 National Electrical Manufacturers Association .................................. 3-29

3.2.8 Regulatory Programs ......................................................................................... 3-30

3.2.9 Non-Regulatory Programs................................................................................. 3-31

3.2.9.1 Department of Energy Motor Challenge Program.............................. 3-31

3.2.9.2 National Electrical Manufacturers Association Premium Efficiency 

Motor Program.................................................................................... 3-32

3.2.9.3 Consortium for Energy Efficiency...................................................... 3-32

3.3 TECHNOLOGY ASSESSMENT.................................................................................. 3-33

3.3.1 Technology Options for I2R Losses................................................................... 3-33

3.3.2 Technology Options for Core Losses ................................................................ 3-35

3.3.2.1 Plastic Bonded Iron Powder................................................................ 3-36

3.3.3 Technology Options for Friction and Windage Losses ..................................... 3-37

3.3.4 Technology Options for Stray-Load Losses...................................................... 3-37

3.3.5 Summary of the Technology Options Under Consideration.............................. 3-37
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LIST OF TABLES

Table 3.1 Electric Motor Equipment Class Groups............................................ 3-13

Table 3.2 NEMA Design A and B Equipment Classes....................................... 3-16

Table 3.3 NEMA Design C Equipment Classes................................................. 3-17

Table 3.4 Fire Pump Electric Motor Equipment Classes.................................... 3-18

Table 3.5 Characteristics of Motors Regulated Under Expanded Scope of 

Coverage 3-20

Table 3.6 Electric Motor Types DOE Plans on Regulating Under Newly-Expanded 

Scope of Conservation Standards .............................................................................................. 3-20

Table 3.7 Electric Motors Excluded from Expanded Scope of Coverage .......... 3-21

Table 3.8 Core Steel Grades, Thicknesses, and Associated Losses.................... 3-36

Table 3.9 Summary of Technology Options for Improving Efficiency.............. 3-38

LIST OF FIGURES

Figure 3.2.1 Electric Motor Shipments by Design Type for 2011.......................... 3-25

Figure 3.2.2 Electric Motor Shipments by Horsepower Rating for 2011 ............... 3-26

Figure 3.2.3 Electric Motor Shipments by Pole Configuration for 2011................ 3-27

Figure 3.2.4 Electric Motor Shipments by Enclosure Type for 2011 ..................... 3-28
3-1

CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT

3.1 INTRODUCTION

This chapter provides a profile of the electric motor industry in the United States. The 

U.S. Department of Energy (DOE) developed the preliminary market and technology assessment 

presented in this chapter primarily from publicly available information. This assessment is 

helpful in identifying the major manufacturers and their equipment characteristics, which form 

the basis for the engineering and life-cycle cost (LCC) analyses.

This chapter consists of two sections: the market assessment and the technology 

assessment. The market assessment provides an overall picture of the market for the equipment 

concerned, including a scope of the equipment covered, equipment classes, industry structure, 

manufacturer market shares; regulatory and non-regulatory efficiency improvement programs; 

and market trends and quantities of equipment sold. The technology assessment identifies a 

preliminary list of technology options for reducing motor losses to consider in the screening 

analysis.

The information DOE gathers for the market and technology assessment serves as 

resource material for use throughout the rulemaking. DOE considers both quantitative and 

qualitative information from publicly available sources and interested parties.

3.2 MARKET ASSESSMENT

This section addresses the scope of the rulemaking, identifies potential equipment

classes, estimates national shipments of electric motors, and the market shares of electric motor 

manufacturers. This section also discusses the application and performance of existing 

equipment and regulatory and non-regulatory programs that apply to electric motors.

3.2.1 Electric Motor Definitions

The Energy Policy and Conservation Act (EPCA), as amended by the Energy Policy Act 

of 1992 (EPACT 1992), had previously established a definition for “electric motor” as “any 

motor which is a general purpose T-frame, single-speed, foot-mounting, polyphase squirrel-cage 

induction motor of the National Electrical Manufacturers Association (NEMA]) Design A and B, 

continuous rated, operating on 230/460 volts and constant 60 Hertz line power as defined in 

NEMA Standards Publication MG1–1987.” (42 U.S.C. 6311(13)(A) (1992)) Through 

subsequent amendments to EPCA and, in particular, the Energy Independence and Security Act 

that was signed into law on December 19, 2007 (EISA 2007), Congress struck the EPACT 1992 

definition and replaced it with language that covered a broader scope of general purpose electric 

motors, (See 42 U.S.C. 6311(13)(A)-(B) (2010)). 

Consequently, the new terminology adopted as a result of EISA 2007 generated 

confusion over the definitions of the terms “electric motor” and “general purpose electric motor.” 

As a result, DOE sought to clarify its interpretations of these definitions in a rulemaking about 

test procedures for electric motors. On May 4, 2012, DOE published in the Federal Register a 
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test procedure final rule for electric motors which clarified the two definitions. 77 FR 26608 A 

regulatory definition of “electric motor” was promulgated in light of EISA 2007’s removal of the 

statutory definition of “electric motor.” The definition of “general purpose motor” (now “general 

purpose electric motor”) was taken directly from the industry standard NEMA MG1-1993 and 

was intended to specify a broad category of motors that were potentially subject to regulation. 

The term “electric motor” enumerated specific construction and performance characteristics 

required for a “general purpose motor” to be covered equipment under Title 10 of the Code of 

Federal Regulations, Part 431 (10 CFR Part 431).

The test procedure was intended to clear up confusion over the definitions of “electric 

motor” and “general purpose electric motor.” The test procedure final rule defined the two terms 

as follows:

“Electric motor means a machine that converts electrical power into rotational 

mechanical power.”

and

“General purpose electric motor means any electric motor that is designed in standard 

ratings with either:

(1) Standard operating characteristics and mechanical construction for use under usual 

service conditions, such as those specified in NEMA MG1–2009, paragraph 14.2, “Usual Service 

Conditions,” (incorporated by reference, see § 431.15) and without restriction to a particular 

application or type of application; or

(2) Standard operating characteristics or standard mechanical construction for use under 

unusual service conditions, such as those specified in NEMA MG1–2009, paragraph 14.3, 

“Unusual Service Conditions,” (incorporated by reference, see § 431.15) or for a particular type 

of application, and which can be used in most general purpose applications.”

EISA 2007 also introduced and established energy conservation standards for several 

new categories of electric motors. As such, the test procedure final rule sought to clarify DOE’s 

interpretation of these terms. Ultimately, DOE created new definitions for the terms “general 

purpose electric motor (subtype I),” “general purpose electric motor (subtype II),” “NEMA 

Design B motor,” and “fire pump electric motor,” which are shown below.

As a result of the recent electric motors test procedure final rule, 10 CFR 431.12 now 

defines a general purpose electric motor (subtype I) as a general purpose electric motor that:

(1) Is a single-speed, induction motor;

(2) Is rated for continuous duty (MG1) operation or for duty type S1 (IEC);

(3) Contains a squirrel-cage (MG1) or cage (IEC) rotor;

(4) Has foot-mounting that may include foot-mounting with flanges or detachable feet;
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(5) Is built in accordance with NEMA T-frame dimensions or their IEC metric

equivalents, including a frame size that is between two consecutive NEMA frame 

sizes or their IEC metric equivalents;

(6) Has performance in accordance with NEMA Design A (MG1) or B (MG1)

characteristics or equivalent designs such as IEC Design N (IEC);

(7) Operates on polyphase alternating current 60-hertz sinusoidal power, and:

(i) Is rated at 230 or 460 volts (or both) including motors rated at multiple voltages that 

include 230 or 460 volts(or both), or

(ii) Can be operated on 230 or 460 volts (or both); and

(8) Includes, but is not limited to, explosion-proof construction.

Further, the recent electric motors test procedure final rule amended 10 CFR 431.12, 

which now defines a general purpose electric motor (subtype II) as any general purpose electric 

motor that incorporates design elements of a general purpose electric motor (subtype I) but, 

unlike a general purpose electric motor (subtype I), is configured in one or more of the following 

ways:

(1) Is built in accordance with NEMA U-frame dimensions as described in NEMA MG1–

1967 (incorporated by reference, see § 431.15) or in accordance with the IEC metric 

equivalents, including a frame size that is between two consecutive NEMA frame 

sizes or their IEC metric equivalents;

(2) Has performance in accordance with NEMA Design C characteristics as described in 

MG1 or an equivalent IEC design(s) such as IEC Design H;

(3) Is a close-coupled pump motor;

(4) Is a footless motor;

(5) Is a vertical solid shaft normal thrust motor (as tested in a horizontal configuration) 

built and designed in a manner consistent with MG1;

(6) Is an eight-pole motor (900 rpm); or

(7) Is a polyphase motor with a voltage rating of not more than 600 volts, is not rated at 

230 or 460 volts (or both), and cannot be operated on 230 or 460 volts (or both).

Also, as a result of the electric motors test procedure final rule, 10 CFR 431.12 defines a 

NEMA Design B motor as a squirrel-cage motor that is: 

(1) Designed to withstand full-voltage starting;

(2) Develops locked-rotor, breakdown, and pull-up torques adequate for general 

application as specified in sections 12.38, 12.39 and 12.40 of NEMA MG1– 2009 

(incorporated by reference, see § 431.15); 

(3) Draws locked-rotor current not to exceed the values shown in section 12.35.1 for 60 

hertz and 12.35.2 for 50 hertz of NEMA MG1–2009; and

(4) Has a slip at rated load of less than 5 percent for motors with fewer than 10 poles.

Finally, the electric motors test procedure final rule, amended 10 CFR 431.12 by defining 

a fire pump electric motor in the following manner:
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Fire pump electric motor means an electric motor, including any IEC-equivalent, that 

meets the requirements of section 9.5 of NFPA 20 (incorporated by reference, see § 431.15).

3.2.1.1 Expanded Scope Definitions

DOE’s expanded scope of coverage requires clarifying the terminology related to a 

number of motor types and, in particular which types of motors would be subject to energy 

conservation standards and which types would not be subject to minimum standards. NEMA 

MG1-2011 contains defining language for some of these electric motor types. Where possible, 

DOE used this language from NEMA MG1–2011 to build potential definitions for some motor 

types, such as “encapsulated electric motor” as well as NEMA Design A and C electric motors. 

However, some of the motor types that DOE plans on subjecting to energy conservation 

standards, such as “partial electric motor” or “air-over electric motor,” are not defined in NEMA 

MG1–2011. Additionally, DOE is not aware of standard, industry-accepted definitions for many 

of these motor types and will look to create them in a test procedure rulemaking that is being 

developed in parallel with this motor standards rulemaking. DOE believes the lack of clearly 

defined, standard motor definitions could cause confusion concerning which motor types are 

subject to efficiency regulations. Therefore, DOE has worked with industry experts in an effort 

to create working definitions for various motor types that DOE plans on including in the 

expansion of energy conservation standards. DOE also looks to create definitions for motor types 

that are specifically called out from being covered under energy conservation standards. A more 

in-depth discussion of these motor types, as well as reasons for DOE including or excluding 

them in the expanded scope of energy conservation standards, are discussed in more detail in 

chapter 2 of the preliminary technical support document (TSD). Below, DOE presents a short 

summary of the motor characteristics and the definitions it is considering for each motor type. 

Air-Over Electric Motors

Air-over electric motors require an external, separate means of cooling to allow 

continuous duty operation. These motors are subject to over-heating and therefore cannot run 

continuously without a specified amount of air flowing over the motor housing, which is 

typically specified by the manufacturer.

DOE may consider proposing to include a definition for “air-over electric motor” based 

on the MG1–2011 paragraph 1.26.9 definition of a “totally enclosed air-over machine” with 

modifications to the definition to also include air-over electric motors with an open-frame 

construction. DOE wishes to make this change in an effort to broaden the scope of the NEMA 

MG1–2011 definition to include air-over electric motors with both totally enclosed and openframe constructions. DOE believes both frame constructions of these motor types use the same 

methods for heat dissipation and therefore looks to define them under the same term. DOE is 

considering the following definition for “air-over electric motor:”

Air-over electric motor means an electric motor designed for cooling by a ventilating 

means external to and not supplied with the motor.
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Electric Motors with Brake Components

Brake motors are motors with a braking mechanism either attached to an exterior shaft or 

built inside the motor enclosure. The brake mechanism is typically mounted on the end opposite 

the drive of the motor. The braking system is typically an electrically released, spring-loaded 

mechanism. The brake component is “energized” during normal operation of the motor. During 

this normal operation, the brake component is not touching or interfering with the motor 

operation, but is drawing power from the same source as the electric motor. When an emergency 

situation arises, power is cut off from the brake component, and the brake “clamps” down on the 

motor shaft to quickly stop rotation of the motor.

DOE may consider proposing definitions for two terms to describe motors with brake 

components: “non-integral brake motors” and “integral brake motors.” A “non-integral brake 

motor” consists of a brake mounted to the motor in such a fashion that the brake component is 

typically bolted onto the outside of the fan cover of the motor and could be removed from the 

motor with minimal disassembly and the motor could operate as a general purpose electric 

motor. An “integral brake motor” consists of a factory-built unified assembly typically built 

either inside the endshield of the motor or in between the motor fan and rotor component. With 

“integral brake motors,” the brake component is difficult to remove, and doing so could require 

disassembly of the motor which may adversely affect its performance. 

DOE is considering the following definitions for “non-integral brake motor” and 

“integral brake motor” based on comments and feedback from industry experts and NEMA. 

DOE is using comments and feedback to define these motor types because there is no definition 

for these motor types in MG1–2011. DOE plans to adopt the following definitions:

Integral brake motor means an electric motor containing a brake mechanism either inside 

of the motor endshield or between the motor fan and endshield such that removal 

of the brake component would require extensive disassembly of the motor or 

motor parts.

Non-integral brake motor means an electric motor containing a brake mechanism 

attached externally in such a manner that it could be readily detached from the 

motor without extensive disassembly of the motor or motor components.

Component Sets

Component sets of electric motors are comprised of a combination of motor parts, such as 

a stator, rotor, shaft, stator housing, shaft bearings, endshields, or other electric motor parts. DOE 

delineated between component sets and partial motors in chapter 2 of the preliminary TSD when 

it called out partial motors as motors only missing one or more endshields. Endshields are the 

circular, metal plates on each end of the motor that enclose the ends of the motor and house the 

shaft bearings and possibly other components. Component sets are typically sold to be turned 

into complete electric motors or installed in equipment by the end-user. 
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DOE is considering the following definition of “component sets” of electric motors based 

on comments gathered from subject matter experts (SME), NEMA, and other industry experts. 

DOE is taking this approach because there is no definition for these motor types in MG1–2011.

Component set means a combination of motor parts that require more than the addition of 

two endshields to create an operable motor. These parts may consist of any 

combination of a stator frame, wound stator, rotor, shaft, or endshields.

Motors with Customer Defined Endshields

Motors may have special or customer-defined endshields, flanges, bases, or mounting 

feet that do not conform to NEMA MG1–2011 standards for typical endshields, flanges, bases, 

or mounting feet dimensions. DOE may consider proposing a definition for motor types with 

“customer-defined endshields” that are based on comments and feedback from industry experts 

and NEMA. DOE bases this definition on electric motors that deviate from the standard 

endshield or flange mounting specifications for Type C face-mounting, Type D flange-mounting, 

or Type P flange-mounting types specified in NEMA MG1-2011, paragraphs 1.63.1, 1.63.2, and

1.63.3 respectively. DOE is taking this approach because there is no definition for these motor 

types in MG1–2011. DOE is considering the following definition for electric motors with 

customer defined endshields:

A motor with customer defined endshields means an electric motor with customized 

flanges which do not conform to NEMA MG1–2011 paragraphs 1.63.1, 1.63.2, or 

1.63.3.

Encapsulated Electric Motors

Encapsulated motors have special insulation protecting the stator winding from 

condensation, moisture, dirt, and debris. This insulation typically consists of a special material 

coating that completely seals off the stator’s copper windings. Encapsulation is generally found 

on open-frame motors, such as open drip-proof (ODP) motors, where the possibility of 

contaminants getting inside the motor is higher than on an enclosed-frame motor, such as a 

totally enclosed, fan cooled (TEFC) motor.

DOE may consider proposing a definition for “encapsulated electric motors” based on the 

definition of “machine with sealed windings” in paragraph 1.27.2 from NEMA MG1–2011. 

DOE is considering the following definition for electric motors with encapsulated stator 

windings:

Encapsulated electric motor means an electric motor that 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 and 

shall be capable of passing the conformance test in NEMA MG1–2011 paragraph

12.62.
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IEC Design N Electric Motors

IEC Design N electric motors are similar to NEMA Design B electric motors with 

regards to locked-rotor limits and torque performance requirements. While IEC Design N motors 

are currently subject to energy conservation standards, DOE is looking to add a definition for

them in order to clarifying any coverage-ambiguity. 

DOE may consider proposing to set a definition for “IEC Design N electric motor” that 

would incorporate language from IEC Standard 60034-12 (2007 Ed. 2.1) with some 

modifications that would make the definition more comprehensive. The IEC Standard 60034-12 

(2007 Ed. 2.1) defines IEC Design N motors as “normal starting torque three-phase cage 

induction motors intended for direct-on-line starting, having 2, 4, 6 or 8 poles and rated from 0,4 

kW to 1,600 kW,” with torque characteristics and locked-rotor characteristics described in later 

tables. DOE looks to modify this definition to include all references to tables for torque 

characteristics and locked-rotor characteristics tables to clarify the performance requirements of 

IEC Design N electric motors in the definition. DOE is considering the following definition for 

IEC Design N motors:

IEC design N electric motor means an electric motor with a three-phase cage induction 

motor intended for direct-on-line starting, having 2, 4, 6, or 8 poles, rated from 

0.4 kW to 1,600 kW and conforming to the IEC 60034-12 edition 2.1 torque 

characteristics found in section 6.1, locked rotor apparent power in section 6.2, 

and starting requirements in section 6.3.

Immersible Electric Motors

Immersible motors are motors capable of being submerged and removed from liquid 

without damaging or destroying the motor. Immersible motors are different than submersible 

motors because they are not designed to run while submerged in liquid. DOE understands that 

immersible motors do not rely on the cooling provided by submersion in liquid to operate 

continuously. DOE is also aware that industry sometimes interchanges the use of the two terms 

“immersible” and “submersible.” Because of the potential confusion of the two terms, DOE 

believes it may be appropriate to provide definitions for both immersible and submersible 

electric motor types.

The definition DOE is considering for “immersible electric motor” is based on comments 

and feedback from industry experts and NEMA. DOE may consider proposing a definition for 

this motor type in an effort to provide clarification concerning electric motor types that may be 

subject to efficiency regulation and those that are exempt. The definition DOE is considering for 

this motor type is:

Immersible electric motor means an electric motor designed to withstand complete 

immersion in liquid for a limited amount of time.
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Inverter-Capable Electric Motors

An inverter is a device used to control the speed or torque characteristics of a motor. 

Inverters may also be referred to as inverter drives, drives, variable speed drives, variable 

frequency drives, adjustable frequency drives, alternating current (AC) drives, or microdrives. 

Inverters serve as special electronic controllers to help manipulate the power source of a motor. 

Inverters are used to slow the rotation of a motor or provide a constant torque output of the 

motor. Motors that can operate on an inverter may require special construction or design changes 

to withstand the abnormally harsh operating conditions an inverter may subject a motor to, such 

as increased operating temperatures or increased harmonic distortion of the motor’s power 

supply. Inverters are considered by DOE as part of an “advanced motor system” and are 

discussed in more detail in chapter 2 of the preliminary TSD.

Manufacturer catalogs refer to motors capable of being run on an inverter as “inverter 

duty.” However, DOE understands there are two distinct types of motors that may be referred to 

as “inverter duty” in the motor industry. The first type is a motor that has the ability to be run on 

an inverter drive, but can also run continuously when connected directly to a polyphase, 

sinusoidal line power source (i.e., it can be run continuously without an inverter). DOE plans to 

refer to this type of motor as an “inverter-capable” motor because it is capable of withstanding 

inverter duty operation, but the motor does not necessitate an inverter for continuous-duty 

operation. The second type of motor that the motor industry may refer to as “inverter duty” is a 

motor that cannot operate continuously without the use of an inverter. This motor type is 

discussed under the title “inverter-only electric motor” section below. 

DOE wishes to create a clear understanding of each of these two motor types because it 

understands that there is no industry accepted definitions delineating between motors capable of 

running continuously on an inverter and motors that can only be run continuously on an inverter. 

DOE is considering creating a clear, succinct definition for this motor type in an effort to clarify 

which motor types may be subject to energy conservation standards. The definition DOE is 

considering for “inverter-capable electric motor” is based on feedback and comments from 

industry experts, SMEs, and NEMA and reads:

Inverter-capable electric motor means an electric motor that can run continuously when 

directly connected to polyphase, sinusoidal line power, but is also capable of 

handling continuous operation on an inverter drive.

Inverter-Only Electric Motors

The section above mentions the two types of electric motors capable of being run on an 

inverter. The first type DOE refers to as an ‘inverter-capable’ electric motor. The second type of 

motor often referred to as “inverter duty” is a motor that cannot operate continuously without an 

inverter drive. This motor may have heavy insulation or other design changes to deal with 

operating conditions resulting from inverter operation, such as harmonic distortion of the power 

signal, dielectric stresses resulting from voltage spikes, or hotter-than-typical operating 

temperatures resulting from insufficient air cooling. This motor, unlike an “inverter capable” 

motor, is specifically built for the conditions resulting from inverter-fed operation, and are 
3-9

therefore generally more expensive to build than an “inverter capable” motor. This second motor 

type cannot be used for continuous duty operation on line power without an inverter. DOE plans 

to refer to this second type of motor as an “inverter-only electric motor” because it is specifically 

built to only operate continuously when operated on an inverter.

The definition DOE is considering for “inverter-only electric motor” is based on feedback 

and comments from industry experts, SMEs, and NEMA. As discussed above, DOE looks to 

create a clear, succinct definition for this motor type in an effort to clarify which electric motor 

types may be subject to energy conservation standards. The definition DOE plans on proposing 

for “inverter-only electric motor” is:

Inverter-only electric motor means an electric motor designed such that it can only be run 

continuously when operated through an inverter drive.

Liquid-Cooled Electric Motors

Liquid-cooled electric motors rely on a special cooling apparatus that pumps liquid into 

and around the motor frame. The liquid is circulated around the motor to dissipate heat and 

prevent the motor from overheating during continuous duty operation. The user of a liquidcooled motor may employ different liquids or liquid temperatures which could affect the 

measured efficiency of a motor.

DOE is considering defining “liquid-cooled electric motor” based on the definition of 

“totally enclosed water-cooled machine” in paragraph 1.26.5 of MG1–2011, with some changes. 

DOE is proposing to remove “totally enclosed” from the definition so that open-frame motors 

that are liquid-cooled would also be included in this definition. DOE also plans on replacing the 

term “water” with “liquid” to include motor types that may use other types of liquids, not just 

water, as a coolant. DOE is considering the following definition for “liquid-cooled electric 

motor”:

Liquid-cooled electric motor means an electric motor that is cooled by circulating liquid,

with the liquid or liquid conductors coming in direct contact with the machine 

parts.

NEMA Design A Electric Motors

NEMA MG1–2011 defines four types of polyphase, AC induction motors, NEMA design 

types A, B, C, and D. As stated above, DOE has already adopted a definition for NEMA Design 

B electric motors. NEMA MG1–2011 establishes the same torque requirements for both NEMA 

Design A and NEMA Design B electric motors. However, NEMA Design B electric motors must 

be designed such that their locked-rotor (or starting) current is less than that established for 

NEMA Design A electric motors. Unless the application specifically requires a NEMA Design A 

electric motor design, NEMA Design B electric motors are often used instead of Design A 

electric motors because of the smaller spike in startup current. 
3-10

DOE is considering defining “NEMA Design A electric motor” based on the definition 

found in NEMA MG1–2011 paragraph 1.19.1.1. DOE believes that the MG1–2011 definition of 

“NEMA Design A” electric motor is clear and concise and may consider proposing to define this 

term as:

NEMA design A electric motor means a squirrel-cage motor designed to withstand fullvoltage starting and developing locked-rotor torque as shown in NEMA MG1–

2011 paragraph 12.38, pull-up torque as shown in NEMA MG1–2011 paragraph 

12.40, breakdown torque as shown in NEMA MG1–2011 paragraph 12.39, with 

locked-rotor current higher than the values shown in paragraph 12.35.1 for 60 

hertz and paragraph 12.35.2 for 50 hertz and having a slip at rated load of less 

than 5 percent for motors fewer than 10 poles. 

NEMA Design C Electric Motors

Similarly, NEMA MG1-2011also establishes different torque requirements for NEMA 

Design C electric motors relative to NEMA Design A and B motors. NEMA Design C motors 

are typically used for applications that require high starting-torque applications, such as rock 

crushers or other crushing applications. DOE has placed NEMA Design C motors in their own 

equipment class group for the preliminary analysis. Therefore, DOE believes adopting a formal 

definition would be consistent with its potential adoption of NEMA Design B and NEMA 

Design A electric motor definitions. 

DOE is considering a definition of “NEMA Design C electric motor” based on the 

definition found in NEMA MG1–2011 paragraph 1.19.1.3. DOE believes that the MG1–2011 

definition of “NEMA Design C” electric motor is clear and concise and plans to propose to 

define this term as:

NEMA Design C electric motor means a squirrel-cage motor designed to withstand fullvoltage starting, developing locked-rotor torque for high-torque applications up to 

the values shown in NEMA MG1–2011 paragraph 12.38, pull-up torque as shown 

in NEMA MG1–2011 paragraph 12.40, breakdown torque up to the values shown 

in NEMA MG1–2011 paragraph 12.39, with locked-rotor current not to exceed 

the values shown in paragraph 12.35.1 for 60 hertz and paragraph 12.35.2 for 50 

hertz, and having a slip at rated load of less than 5.

Partial Electric Motors

DOE understands partial motors, also called “partial 3⁄4 motors” or “3⁄4 motors,” as motors 

that are missing one or both endshields. These motors may have an endshield removed to allow 

the motor to be directly connected to another piece of equipment, such as a pump or gearbox. 

When a partial motor is mated to another piece of equipment, it is often referred to as an 

“integral” motor. For example, an “integral gearmotor” is the combination of a partial motor 

mated to a gearbox using bolts or some other means of attachment.
3-11

DOE is considering creating a standard, industry-accepted definition of the term “partial 

electric motor” in order to clarify its understanding of a potential expansion of scope of energy 

conservation standards. Additionally, DOE believes it is currently used inconsistently as an 

“umbrella” term to describe a wide range of electric motor types, including motor types that 

DOE believes should fall under the definition of “component sets” of electric motors. DOE is 

considering a definition of “partial electric motor” based on discussions with industry experts, 

SMEs, and comments from NEMA and other motor-industry groups. DOE hopes to clarify 

energy conservation standards coverage for this rulemaking by setting clear definitions for 

“partial motors.” The definition DOE is considering for “partial electric motor” is:

Partial electric motor means an electric motor necessitating only the addition of one or 

two endshields with bearings to create an operable motor. Included under this 

definition are integral motors and partial 3⁄4 motors.

Submersible Electric Motors

DOE understands submersible electric motors are only capable of continuous duty 

operation while completely submerged in liquid. Submersible motors are similar to liquid-cooled 

motors because they use liquid to dissipate the heat produced during this continuous duty 

operation. However, submersible motors are typically submerged in a liquid as opposed to 

liquid-cooled electric motors that use a separate hose and pump apparatus connected to the 

motor. DOE believes a motor designed to operate while submerged in open water and a motor 

that utilizes a hose and pump apparatus could create significant design changes which would 

warrant separate definitions. Therefore, DOE is considering separate definitions for these two 

motor types to avoid any potential ambiguity between the two motor types.

DOE is considering defining “submersible electric motor” based on the description of 

“submersible motors for deep well pumps” in NEMA MG1–2011 part 18, page 52. The 

definition DOE is considering is:

Submersible electric motor means an electric motor designed for continuous operation 

while submerged in a liquid. Such a motor is unable to operate continuously if not 

submerged in liquid.

Totally Enclosed Non-Ventilated Electric Motors

A majority of the medium-size electric motors shipped in the U.S. are TEFC. These 

motors have a fan on the outside of the end opposite the drive-end which blows air over the 

surface of the motor (typically the fan is enclosed by a metal fan cover). This airflow over the 

surface of the motor helps dissipate heat during the motor’s operation. Unlike TEFC motors, 

totally enclosed, non-ventilated motors (TENV) are motors that have no external fan blowing air 

over the outside of the motor. TENV motors may be used in environments where an external fan 

could clog with dirt or dust. TENV motors are cooled by natural conduction and convection of 

the motor heat into the surrounding environment, which results in a motor that operates at higher 

temperatures than TEFC motors. TENV motors may deal with the higher operating temperatures 
3-12

by adding more frame material to dissipate excess heat or by upgrading stator winding insulation 

to withstand the higher operating temperatures.

DOE is considering defining the term “totally enclosed, non-ventilated electric motor” 

based on the definition of a “totally enclosed non-ventilated machine” in paragraph 1.26.1 in 

NEMA MG1–2011. DOE believes this definition is clear and concise and is considering the 

definition verbatim. DOE is considering the following definition of a TENV motor:

Totally enclosed non-ventilated (TENV) motor means a motor that is a frame-surface 

cooled totally enclosed machine which is only equipped for cooling by free 

convection.

3.2.2 Equipment Class Groups and Equipment Classes

Within each category of electric motors it addressed, EISA 2007 set separate energy 

conservation standards by horsepower rating, enclosure type, and pole configuration. These 

standards correspond to Table 12-12 of NEMA MG 1–2011 (equivalent to NEMA Premiuma

) for 

general purpose electric motors (subtype I) and Table 12-11 of NEMA MG1–2011 (equivalent to 

EPACT 1992 values) for 1 to 200 horsepower general purpose electric motors (subtype II), fire 

pump electric motors, and NEMA Design B electric motors greater than 200 horsepower.

b (42 

U.S.C. 6313(b)(2))

In general, when DOE amends energy conservation standards, it divides covered 

equipment into classes. By statute, these classes are based on: (a) the type of energy used; (b) 

the capacity of the equipment; or (c) any other performance-related feature that justifies different 

efficiency levels, such as features affecting consumer utility. (42 U.S.C. 6295(q)) As a result of 

changes in EISA 2007, particularly with the addition of general purpose electric motors (subtype 

II) as a subset of motors covered by the term “electric motor,” there are a large number of motor 

design features that DOE considered in this rulemaking. In the following sections, DOE 

discusses the design features that it is considering as part of its analysis.

Due to the number of electric motor characteristics (e.g., horsepower rating, pole 

configuration, and enclosure), DOE is using two constructs, at this stage, to help develop 

appropriate energy conservation standards for electric motors: “equipment class groups” and 

“equipment classes.” An equipment class group is a collection of electric motors that share a 

common design type. Equipment class groups include motors over a range of horsepower 

ratings, enclosure types, and pole configurations. Essentially, each equipment class group is a 

collection of a large number of equipment classes with the same design type. An equipment 

class represents a unique combination of motor characteristics for which DOE will determine an 

energy efficiency conservation standard. For example, given a combination of motor design type, 

horsepower rating, pole configuration, and enclosure type, the motor design type dictates the 

 

a NEMA Premium efficiency levels refer to the efficiency values in NEMA MG1-2011 Table 12-12. b EISA 2007 also set minimum conservation levels for subtype I motors from 201-500 horsepower at the EPACT 

1992 levels.
3-13

equipment class group, while the combination of the remaining characteristics dictates the 

specific equipment class.

For the preliminary analysis DOE has created three equipment class groups based on two 

main motor characteristics: the designated NEMA design letter and whether the motor meets the 

definition of a fire pump electric motor. DOE’s resulting equipment class groups are for NEMA 

Design A and B motors (including IEC-equivalent designs), NEMA Design C motors (including 

IEC-equivalent designs), and fire pump electric motors (including IEC-equivalent designs). 

Within each of these three broad groups, DOE uses combinations of other pertinent motor 

characteristics to enumerate its individual equipment classes. To illustrate the differences 

between the two terms, consider the following example. A NEMA Design B, 50 horsepower 

(hp), 2-pole enclosed electric motor and a NEMA Design B, 100 hp, 6-pole open electric motor 

would both be in the same equipment class group (for the preliminary analysis, group 1), but 

each motor would represent a unique equipment class, which will ultimately have its own 

efficiency standard. There are 478 potential equipment classes which consist of all permutations 

of electric motor design types (i.e., NEMA Design A and B, NEMA Design C, or fire pump 

electric motor), standard horsepower ratings (i.e., standard ratings from 1 to 500 horsepower), 

pole configurations (i.e., 2-, 4-, 6-, or 8-pole), and enclosure types (i.e., open or enclosed). Table 

3.1 illustrates the relationships between equipment class groups and the characteristics used to 

define equipment classes. In the following sections, DOE discusses each of these design 

features.

Table 3.1 Electric Motor Equipment Class Groups

Equipment 

Class Group Electric Motor Design Horsepower Poles Enclosure

1 NEMA Design A & B* 1-500 2, 4, 6, 8 Open

Closed

2 NEMA Design C* 1-200 2, 4, 6, 8 Open

Closed

3 Fire Pump* 1-500 2, 4, 6, 8

Open

Closed

*Including IEC equivalents.

DOE notes that should it establish amended energy conservation standards for electric 

motors with this arrangement of equipment class groups and equipment classes, it would no 

longer disaggregate its standards by general purpose electric motor subtype I and II. 

Additionally, in light of DOE’s plan to expand the scope of energy conservation standards in this 

rulemaking, the equipment class groups listed in Table 3.1 would include motor types that 

previously may not have been subject to energy conservation standards, including motors that 

may not fall under the categories of subtype I or II motors.
3-14

3.2.2.1 Electric Motor Design

Various industry organizations, such as NEMA and IEC, publish performance criteria

that provide specifications that electric motors must meet in order to be assigned different design 

types. As these design types represent a certain set of performance parameters, they provide 

electric motor users with an easy reference to use when designing their equipment and when 

purchasing a motor to drive their equipment. The electric motors covered under this rulemaking 

must meet one of three NEMA design types. For medium polyphase alternating current (AC) 

induction motors, the three NEMA design types considered general purpose and covered by 

EPCA, as amended by EISA 2007, are Design A, Design B, and Design C. The definitions for 

these three motor types are as follows:

In NEMA MG1–2011 paragraph 1.19.1.1, “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.”

Under 10 CFR 431.12,c “NEMA Design B motor means a squirrel-cage motor that is (1)

designed to withstand full-voltage starting, (2) develops locked-rotor, breakdown, and pull-up 

torques adequate for general application as specified in sections 12.38, 12.39 and 12.40 of 

NEMA Standards Publication MG1–2009 (incorporated by reference, see § 431.15), (3)draws

locked-rotor current not to exceed the values shown in section 12.35.1 for 60 hertz and 12.35.2

for 50 hertz of NEMA Standards Publication MG1–2009, and (4) has a slip at rated load of less 

than 5 percent for motors with fewer than 10 poles.”

In NEMA MG1–2011 paragraph 1.19.1.3,“A Design C motor is a squirrel-cage motor 

designed to withstand full-voltage starting, developing locked-rotor torque for special hightorque 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 [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.”

NEMA Design A and NEMA Design B electric motors have different locked-rotor 

current requirements. NEMA Design A electric motors have no locked-rotor current limits 

whereas NEMA Design B electric motors are required to stay below certain maximums specified 

in NEMA MG1-2011 paragraph 12.35.1. This tolerance for excess current will allow NEMA 

Design A motors to reach the same efficiency levels as NEMA Design B with fewer design 

changes and constraints. However, NEMA Design A and NEMA Design B motors have the 

same requirements for locked-rotor, pull-up, and breakdown torque and are consequently used in 

many of the same applications. Additionally, as is shown in section 3.2.4 below, NEMA Design 

 

c As this definition was adopted and codified into the CFR, DOE added some minor language to specify which 

version of NEMA MG1 should be used and DOE corrected some minor typographical errors that referred the reader 

to the wrong tables for locked rotor current specifications.
3-15

B motors constitute a significantly larger population of the electric motors that are shipped 

relative to NEMA Design A motors.

NEMA Design C electric motors, on the other hand, have different torque requirements 

than NEMA Design A or B motors. NEMA Design C electric motors typically have higher 

torque requirements. DOE believes that this performance change represents a change in utility 

which can also affect efficiency. Additionally, the difference in torque requirements will restrict 

which applications can use which NEMA Design types. As a result, NEMA Design C motors 

will not always be replaceable with NEMA Design A or B motors, or vice versa. 

DOE notes that Congress held NEMA Design A and NEMA Design B motors to the 

same energy conservation standards prescribed by EPACT 1992 (42 U.S.C. 6311(13)(A)) and 

EISA 2007 (42 U.S.C. 6311 (13)(A)) (see requirements for general purpose electric motors 

(subtype I)). For the preliminary analysis, DOE has followed the precedent set by EPACT 1992 

and EISA 2007 and has considered NEMA Design A and B motors in a group together, while 

placing NEMA Design C motors in their own equipment class group. Finally, DOE notes that all 

equivalent IEC design types are also covered by this energy conservation standards rulemaking 

and should be considered with their corresponding NEMA Design type. 

3.2.2.2 Fire Pump Electric Motors

EISA 2007 prescribed energy conservation standards for fire pump electric motors. (42 

U.S.C. § 6313(b)(2)(B)) Fire pump electric motors are motors with special design characteristics 

that make them more suitable for emergency operation. As stated previously, DOE adopted a 

definition of “fire pump electric motor,” which incorporated portions of the National Fire 

Protection Association (NFPA) Standard 20, “Standard for the Installation of Stationary Pumps 

for Fire Protection” (2010). Such electric motors, per the requirements of NFPA 20, are required 

to be marked as complying with NEMA Design B performance standards and be capable of 

operating even if it overheats or may be damaged due to continued operation. These additional 

requirements for a fire pump electric motor constitute a change in utility, apart from other 

general purpose electric motors, which DOE believes could also affect its performance and 

efficiency. Therefore, DOE has preliminarily established a separate equipment class group for 

fire pump electric motors.

3.2.2.3 Horsepower Rating

Horsepower is a measurement directly related to the capacity of an electric motor to 

perform useful work and, therefore, it is one of DOE’s primary criteria in designating equipment 

classes. Horsepower rating defines the output power of an electric motor, where 1 horsepower 

equals 745.7 Watts. It is generally true that efficiency scales with horsepower. In other words, a 

50-horsepower motor is usually more efficient than a 10-horsepower motor. Also, because of its 

larger frame size and additional active material (e.g., copper wiring and electrical steel), the 50-

horsepower motor will be able to achieve a higher, maximum level of efficiency. Horsepower is 

a critical performance attribute of an electric motor, and because there is a direct correlation 

between horsepower and efficiency, DOE is preliminarily using horsepower rating as an 

equipment class setting criterion.
3-16

3.2.2.4 Pole configuration

An electric motor’s pole configuration corresponds to the number of magnetic poles 

present in the motor. Consequently, the number of magnetic poles (or “poles”) dictates the 

revolutions per minute (RPM) of the rotor and shaft. For each pole configuration there is a 

corresponding synchronous speed, in RPMs, which is the theoretical maximum speed at which a 

motor might operate without a load. All of the electric motors covered by this rulemaking are 

asynchronous motors, meaning they cannot reach this speed. There is an inverse relationship 

between the number of poles and a motor’s speed. As the number of poles increases from two to 

four to six to eight, the synchronous speed drops from 3,600 to 1,800 to 1,200 to 900 RPMs. 

Because the number of poles has a direct impact on the rotational speed of a motor shaft, it also 

affects a motor’s utility and performance, including efficiency. Therefore, DOE is also using 

pole configuration as a means of differentiating equipment classes for the preliminary analysis.

3.2.2.5 Enclosure type

In general, there are two variations of enclosure types, either open or enclosed. DOE 

currently defines both of these terms under 10 CFR 431.12. An electric motor meets the current 

definition of an “enclosed motor” if it is “an electric motor so constructed as to prevent the free 

exchange of air between the inside and outside of the case but not sufficiently enclosed to be 

termed airtight.” An open motor is defined under 10 CFR 431.12 as “an electric motor having 

ventilating openings which permit passage of external cooling air over and around the windings 

of the machine.” As in EPACT 1992, EISA 2007 prescribes separate energy conservation 

standards for open and enclosed electric motors. (42 U.S.C. 6313 (b)(1)) 

DOE is aware that given two motors of the same horsepower rating, pole configuration, 

and frame size, an open machine is typically more efficient than an enclosed motor. This occurs 

because enclosure type affects an electric motor’s ability to dissipate heat (the open motor’s free 

air exchange allows for better thermal dissipation), which enables open motors to achieve higher 

efficiency levels than their enclosed counterparts. Additionally, whether an electric motor is 

open or enclosed affects its utility in that open motors are generally not used in harsh operating 

environments, whereas enclosed electric motors often are. Therefore, because of the effects on 

both efficiency and consumer utility, DOE is using motor enclosure as an equipment classsetting criterion for the preliminary analysis.

Table 3.2, Table 3.3, and Table 3.4 illustrate the relationship between equipment class 

and various motor design characteristics.

Table 3.2 NEMA Design A and B Equipment Classes

Horsepower Enclosure Two Poles Four Poles Six Poles Eight Poles

1.0

Open - EC#1 EC#2 EC#3

Enclosed - EC#4 EC#5 EC#6

1.5

Open EC#7 EC#8 EC#9 EC#10

Enclosed EC#11 EC#12 EC#13 EC#14

2.0

Open EC#15 EC#16 EC#17 EC#18

Enclosed EC#19 EC#20 EC#21 EC#22

3.0 Open EC#23 EC#24 EC#25 EC#26
3-17

Enclosed EC#27 EC#28 EC#29 EC#30

5.0

Open EC#31 EC#32 EC#33 EC#34

Enclosed EC#35 EC#36 EC#37 EC#38

7.5

Open EC#39 EC#40 EC#41 EC#42

Enclosed EC#43 EC#44 EC#45 EC#46

10.0

Open EC#47 EC#48 EC#49 EC#50

Enclosed EC#51 EC#52 EC#53 EC#54

15.0

Open EC#55 EC#56 EC#57 EC#58

Enclosed EC#59 EC#60 EC#61 EC#62

20.0

Open EC#63 EC#64 EC#65 EC#66

Enclosed EC#67 EC#68 EC#69 EC#70

25.0

Open EC#71 EC#72 EC#73 EC#74

Enclosed EC#75 EC#76 EC#77 EC#78

30.0

Open EC#79 EC#80 EC#81 EC#82

Enclosed EC#83 EC#84 EC#85 EC#86

40.0

Open EC#87 EC#88 EC#89 EC#90

Enclosed EC#91 EC#92 EC#93 EC#94

50.0

Open EC#95 EC#96 EC#97 EC#98

Enclosed EC#99 EC#100 EC#101 EC#102

60.0

Open EC#103 EC#104 EC#105 EC#106

Enclosed EC#107 EC#108 EC#109 EC#110

75.0

Open EC#111 EC#112 EC#113 EC#114

Enclosed EC#115 EC#116 EC#117 EC#118

100.0

Open EC#119 EC#120 EC#121 EC#122

Enclosed EC#123 EC#124 EC#125 EC#126

125.0

Open EC#127 EC#128 EC#129 EC#130

Enclosed EC#131 EC#132 EC#133 EC#134

150.0

Open EC#135 EC#136 EC#137 EC#138

Enclosed EC#139 EC#140 EC#141 EC#142

200.0

Open EC#143 EC#144 EC#145 EC#146

Enclosed EC#147 EC#148 EC#149 EC#150

250.0

Open EC#151 EC#152 EC#153 EC#154

Enclosed EC#155 EC#156 EC#157 EC#158

300.0

Open EC#159 EC#160 EC#161 -

Enclosed EC#162 EC#163 EC#164 -

350.0

Open EC#165 EC#166 EC#167 -

Enclosed EC#168 EC#169 EC#170 -

400.0

Open EC#171 EC#172 - -

Enclosed EC#173 EC#174 - -

450.0

Open EC#175 EC#176 - -

Enclosed EC#177 EC#178 - -

500.0

Open EC#179 EC#180 - -

Enclosed EC#181 EC#182 - -

Table 3.3 NEMA Design C Equipment Classes

Horsepower Enclosure Four Poles Six Poles Eight Poles

1.0

Open EC#1 EC#2 EC#3

Enclosed EC#4 EC#5 EC#6

1.5

Open EC#7 EC#8 EC#9

Enclosed EC#10 EC#11 EC#12

2.0 Open EC#13 EC#14 EC#15
3-18

Enclosed EC#16 EC#17 EC#18

3.0

Open EC#19 EC#20 EC#21

Enclosed EC#22 EC#23 EC#24

5.0

Open EC#25 EC#26 EC#27

Enclosed EC#28 EC#29 EC#30

7.5

Open EC#31 EC#32 EC#33

Enclosed EC#34 EC#35 EC#36

10.0

Open EC#37 EC#38 EC#39

Enclosed EC#40 EC#41 EC#42

15.0

Open EC#43 EC#44 EC#45

Enclosed EC#46 EC#47 EC#48

20.0

Open EC#49 EC#50 EC#51

Enclosed EC#52 EC#53 EC#54

25.0

Open EC#55 EC#56 EC#57

Enclosed EC#58 EC#59 EC#60

30.0

Open EC#61 EC#62 EC#63

Enclosed EC#64 EC#65 EC#66

40.0

Open EC#67 EC#68 EC#69

Enclosed EC#70 EC#71 EC#72

50.0

Open EC#73 EC#74 EC#75

Enclosed EC#76 EC#77 EC#78

60.0

Open EC#79 EC#80 EC#81

Enclosed EC#82 EC#83 EC#84

75.0

Open EC#85 EC#86 EC#87

Enclosed EC#88 EC#89 EC#90

100.0

Open EC#91 EC#92 EC#93

Enclosed EC#94 EC#95 EC#96

125.0

Open EC#97 EC#98 EC#99

Enclosed EC#100 EC#101 EC#102

150.0

Open EC#103 EC#104 EC#105

Enclosed EC#106 EC#107 EC#108

200.0

Open EC#109 EC#110 EC#111

Enclosed EC#112 EC#113 EC#114

Table 3.4 Fire Pump Electric Motor Equipment Classes

Horsepower Enclosure Two Poles Four Poles Six Poles Eight Poles

1.0

Open - EC#1 EC#2 EC#3

Enclosed - EC#4 EC#5 EC#6

1.5

Open EC#7 EC#8 EC#9 EC#10

Enclosed EC#11 EC#12 EC#13 EC#14

2.0

Open EC#15 EC#16 EC#17 EC#18

Enclosed EC#19 EC#20 EC#21 EC#22

3.0

Open EC#23 EC#24 EC#25 EC#26

Enclosed EC#27 EC#28 EC#29 EC#30

5.0

Open EC#31 EC#32 EC#33 EC#34

Enclosed EC#35 EC#36 EC#37 EC#38

7.5

Open EC#39 EC#40 EC#41 EC#42

Enclosed EC#43 EC#44 EC#45 EC#46

10.0

Open EC#47 EC#48 EC#49 EC#50

Enclosed EC#51 EC#52 EC#53 EC#54

15.0 Open EC#55 EC#56 EC#57 EC#58
3-19

Enclosed EC#59 EC#60 EC#61 EC#62

20.0

Open EC#63 EC#64 EC#65 EC#66

Enclosed EC#67 EC#68 EC#69 EC#70

25.0

Open EC#71 EC#72 EC#73 EC#74

Enclosed EC#75 EC#76 EC#77 EC#78

30.0

Open EC#79 EC#80 EC#81 EC#82

Enclosed EC#83 EC#84 EC#85 EC#86

40.0

Open EC#87 EC#88 EC#89 EC#90

Enclosed EC#91 EC#92 EC#93 EC#94

50.0

Open EC#95 EC#96 EC#97 EC#98

Enclosed EC#99 EC#100 EC#101 EC#102

60.0

Open EC#103 EC#104 EC#105 EC#106

Enclosed EC#107 EC#108 EC#109 EC#110

75.0

Open EC#111 EC#112 EC#113 EC#114

Enclosed EC#115 EC#116 EC#117 EC#118

100.0

Open EC#119 EC#120 EC#121 EC#122

Enclosed EC#123 EC#124 EC#125 EC#126

125.0

Open EC#127 EC#128 EC#129 EC#130

Enclosed EC#131 EC#132 EC#133 EC#134

150.0

Open EC#135 EC#136 EC#137 EC#138

Enclosed EC#139 EC#140 EC#141 EC#142

200.0

Open EC#143 EC#144 EC#145 EC#146

Enclosed EC#147 EC#148 EC#149 EC#150

250.0

Open EC#151 EC#152 EC#153 EC#154

Enclosed EC#155 EC#156 EC#157 EC#158

300.0

Open EC#159 EC#160 EC#161 -

Enclosed EC#162 EC#163 EC#164 -

350.0

Open EC#165 EC#166 EC#167 -

Enclosed EC#168 EC#169 EC#170 -

400.0

Open EC#171 EC#172 - -

Enclosed EC#173 EC#174 - -

450.0

Open EC#175 EC#176 - -

Enclosed EC#177 EC#178 - -

500.0

Open EC#179 EC#180 - -

Enclosed EC#181 EC#182 - -

3.2.3 Expanded Scope of Coverage

During the October 18, 2010, framework public meeting, DOE received comments 

regarding the energy savings potential from expanding the scope of coverage beyond subtype I, 

subtype II, and fire pump electric motors. DOE addresses these comments in chapter 2 of the 

preliminary TSD DOE’s discussion of expanding the scope of coverage refers to the decision to 

analyze energy conservation standards for electric motor types that currently do not have energy 

conservation standards. DOE has the statutory authority to establish such standards without first 

promulgating a coverage determination rulemaking based on the modifications resulting from 

EISA 2007, which struck the statutory definition for “electric motors.” DOE recognizes the 

energy savings potential of scope expansion for motors previously exempt from conservation 

standards, as well as motors that may not fall into the subtype I, subtype II, and fire pump 

electric motor categories. DOE plans on expanding the scope of conservation standards to all 
3-20

motors with characteristics listed in Table 3.5 and then specifically naming motors for which no 

standards are established. 

Table 3.5 Characteristics of Motors Regulated Under Expanded Scope of Coverage

Motor Characteristic

Is a single-speed, induction motor,

Is rated for continuous duty (MG1) operation or for duty type S1 (IEC),

Contains a squirrel-cage (MG1) or cage (IEC) rotor,

Operates on polyphase alternating current 60-hertz sinusoidal power,

Has a 2-, 4-, 6-, or 8-pole configuration,

Is rated 600 volts or less,

Has a three-digit NEMA frame size and is less than 500 horsepower, and

Is a NEMA Design A, B, or C motor (or an IEC equivalent)

Table 3.6 lists electric motors that are not currently subject to efficiency standards, but 

would be subject to minimum efficiency standards if DOE decides to expand energy efficiency 

standards to electric motors with all of the characteristics listed in Table 3.5 (with the exception 

of specifically named motors that would otherwise not be covered). Such motors would fall into 

the equipment class groups listed in Table 3.1 based on their respective NEMA Design type. See 

chapter 2 of the preliminary TSD for an in-depth discussion of the decision to include these 

motors in the expansion of energy conservation standards. 

Table 3.6 Electric Motor Types DOE Plans on Regulating Under Newly-Expanded 

Scope of Conservation Standards

Electric Motors with Customer Defined Endshields or 

Special Flanges Encapsulated Electric Motor

Electric Motors with Single and Double Shafts of NonStandard Shaft Dimensions or Additions Immersible Electric Motor

Electric Motors with Sleeve Bearings Inverter-Capable Electric Motor

Electric Motors with Special Base or Mounting Feet Partial Electric Motor

Electric Motors with Thrust Bearings Totally Enclosed, Non-Ventilated Electric Motor

Vertical Hollow-Shaft Electric Motor -

In the March 30, 2011, Request For Information related to electric motors, DOE requested 

comment on expanding the scope of energy conservation standards to motors that were not 

currently subject to standards, including some motor types listed in Table 3.6 and Table 3.7. (76 

FR 17577) The motor types listed in Table 3.7 are motor types which, at this time, DOE does not 

plan on subjecting to energy conservation standards. While some of these motors conform to 

many or all of the characteristics listed in Table 3.5, DOE understands that covering such motors 

might not be warranted due to special operating conditions or testing difficulties as discussed 

below.
3-21

Table 3.7 Electric Motors Excluded from Expanded Scope of Coverage

Electric Motor Type

Air-Over Electric Motors Direct Current Motors

Component Sets Single Phase Motors

Intermittent Duty Motors Liquid-Cooled Motors

Inverter-Only Duty Motors Submersible Motors

Multispeed Motors -

Air-Over Electric Motors

Air-over electric motors require an external means of cooling to allow continuous duty 

operation. These motors may be subject to over-heating and therefore cannot run continuously 

without a specified amount of air flowing over the motor housing. The required air flow amount 

is usually determined by the manufacturer as part of the motor design and performance 

characteristics. 

DOE is not planning on covering air-over motors because of the test setup complexities 

required for these motors. DOE’s primary test procedure, the Institute of Electrical and 

Electronics Engineers, Inc. (IEEE) Standard 112–2004 Test Method B (IEEE 112B), requires

certain measurements to be taken at a steady-state temperaturesd

. Reaching a steady-state 

temperature requires a motor to be rated and operate under continuous-duty conditions; 

otherwise the motor could overheat and be damaged before reaching a steady-state temperature. 

IEEE 112B does not provide directions on how to setup an air-over motor for testing, which 

would otherwise require an external cooling apparatus. DOE is not aware of test procedures that 

provide guidance on how to test such motors. DOE requests comment on testing non-continuous 

duty motors in chapter 2 of the preliminary TSD. 

Liquid-Cooled Motors

Liquid-cooled electric motors rely on a special cooling apparatus that pumps liquid into 

and around the motor housing. The liquid is circulated around the motor to dissipate heat and 

prevent the motor from overheating during continuous-duty operation. The user of a liquidcooled motor could employ different liquids or liquid temperatures which could affect the 

measured efficiency of a motor. IEEE 112B does not provide standardized direction for testing 

liquid-cooled motors, and therefore DOE does not plan on including them in the scope of 

coverage. DOE requests comment on the testing of liquid-cooled electric motors, including any 

test procedure that is capable of testing these motor types.

Submersible Motors

Submersible motors are similar to liquid-cooled motors in that they use liquid to dissipate 

the heat produced during continuous duty operation. However, unlike liquid-cooled motors, 

 

d Section 3.3.2 of IEEE 112B requires the conductor losses to be measured when the machine is at a specified 

temperature.
3-22

submersible motors are only meant to operate while completely submerged in water, as opposed 

to having a hose and pump apparatus circulating liquid around the motor enclosure. 

DOE is not aware of any test procedures for motors that can only operate continuously in 

special environments, such as underwater. Therefore, DOE does not plan on including 

submersible motors in the expanded scope of coverage. DOE requests comment on the testing of 

submersible electric motors, including any test procedure that is capable of testing these motor 

types.

Component Sets

Component sets are comprised of any combination of motor parts, such as a stator, rotor, 

shaft, stator housing, shaft bearings, endshields, or other electrical parts. DOE delineated 

between component sets and partial motors in chapter 2 of the preliminary TSD when it called 

out partial motors as motors only missing one or both endshields. Component sets are typically 

sold to be turned into complete electric motors or installed in equipment by the end-user. 

DOE believes component sets do not constitute a complete motor that could be tested 

under IEEE 112B. Additionally, DOE is not aware of any test procedures that would 

accommodate the testing of component sets of motors. While DOE is planning on including 

partial motors in the expansion of energy conservation standards by testing them with a custombuilt endshield that could be attached as a ‘dummy’ endplate for testing, DOE believes 

component sets would require too many or various hardware additions to make a complete 

motor. Therefore, DOE does not plan on including component sets in the expanded scope of 

coverage. DOE requests comment on the decision not to subject these motor types to efficiency 

standards due to testing difficulties. DOE requests comment on any applicable testing standards 

that are capable of testing component sets of electric motors.

Intermittent-Duty Electric Motors

Intermittent-duty motors are motors that, by definition, are not able to operate 

continuously under full load. DOE does not plan to include such motors in the expanded scope 

for energy conservation standards because it does not believe intermittent-duty motors present 

significant opportunities for energy savings. Additionally, IEEE 112B requires measurements to 

be taken at a steady-state temperatures. Reaching a steady-state temperature requires a motor to 

be rated and operate under continuous-duty conditions; otherwise the motor could overheat and 

be damaged before reaching a steady-state temperature. Intermittent-duty motors are not capable 

of continuous-duty operation and, therefore, never reach a steady-state temperature which IEEE 

112B requires for certain calculations. Otherwise, DOE is not aware of any test procedures 

which provide for testing an intermittent or non-continuous-duty motor. DOE requests comment 

on this matter in chapter 2 of the preliminary TSD. 

Inverter-Only Electric Motors

Inverter-only motors cannot be run continuously when directly connected to a 60-hertz, 

AC polyphase sinusoidal power source. Therefore a separate, special electronic controller, called 
3-23

an inverter, is used to alter the power signal to the motor. For a more in-depth discussion of how 

inverter controllers work, see chapter 2 of the preliminary TSD.

Inverter controllers are not necessarily 100 percent efficient when manipulating the 

power signal being fed into the motor. Consequently, the IEEE 112B-measured efficiency of an 

inverter-only motor would not reflect the true efficiency of that motor, but would also include 

any losses inherent in the inverter controller. DOE believes testing an inverter-only motor with 

the inverter controller connected would not accurately record the efficiency of the motor per se. 

DOE is not planning to include inverter-only motors under the expanded scope motors covered 

by energy conservation standards, because it is not aware of any test procedures that recognize 

and differentiate losses caused by the inverter controller. DOE requests comment on this issue in 

chapter 2 of the preliminary TSD.

Multispeed Motors

For this rulemaking, the speed of an electric motor subject to energy conservation 

standards is determined by its magnetic pole configuration (2-, 4-, 6-, or 8-pole), and the 

frequency (60-hertz) of the motor’s incoming power signal. The pole configuration is directly 

determined by the stator winding configuration as discussed in section 3.2.2.4.

In general, multispeed motors are motors with multiple, separate stator winding 

configurations that enable the motor to perform at different speeds contingent upon which 

winding configuration is connected to the power source. For example, a multispeed motor could 

be wound with a 2-pole winding configuration and a 4-pole winding configuration. When the 

power source is connect to the 2-pole winding configuration, the motor shaft will rotate at or 

near (depending on slip) 3,600 revolutions per minute (RPM), and when the 4-pole winding 

configuration is connected to the power source the same motor shaft will rotate at or near 1,800 

RPM.

DOE is not planning to include multispeed motors in the expanded scope of motors 

covered under conservation standards, because it is not aware of any test procedures that provide 

methods for testing a motor with more than one nameplate-rated speed. DOE requests comment 

on any test procedures that are capable of testing multispeed electric motors.

Direct Current Motors

Direct current (DC) motors are motors that run on DC power input. For this rulemaking, 

DOE is covering only electric motors that operate on polyphase, sinusoidal AC power and can be 

tested under IEEE 112B. DC motors cannot be tested under IEEE 112B, but require testing under 

other methods.

Single Phase Motors

Single phase motors operate on a single phase, AC power source. For this rulemaking, 

DOE is covering only electric motors that operate on polyphase, sinusoidal AC power and can be 
3-24

tested for efficiency under IEEE 112B. DOE does not plan to include single phase motors in this 

rulemaking because they cannot be tested according to IEEE 112B.

3.2.4 Electric Motor Shipments

To prepare an estimate of the national impact of energy conservation standards for 

electric motors, DOE needed to estimate annual motor shipments. For this stage of the 

rulemaking, DOE used publically available shipment data from the U.S. Census Bureau, NEMA, 

and the Annual Energy Outlook provided by the U.S. Energy Information Administration. 

DOE used this data for three main purposes. First, the shipment data and market trend 

information contributed to the shipments analysis and base-case forecast for electric motors

(chapter 9 of the preliminary TSD). Second, DOE used the shipment and catalog data to select 

the representative equipment classes and units for analysis (chapter 5 of the preliminary TSD). 

Third, DOE used the data to develop the installed stock of equipment for the national impact 

analysis (chapter 10 of the preliminary TSD). Although more detailed shipments data are given 

in chapter 9, the shipments shown in this chapter illustrate which electric motor characteristics 

were the most common in 2011.

3.2.4.1 NEMA Design Type

As discussed previously, the scope of DOE’s energy conservation standards for electric 

motors covers four design types: NEMA Design A, NEMA Design B, NEMA Design C, and 

fire pump electric motors.e

In 2011, Design B motors were by far the most common electric 

motor type, comprising of 98.7 percent of all shipments. NEMA Design A was the second most 

common design type, consisting of 1.0 percent of shipments. Finally, NEMA Design C and fire 

pump electric motors constituted just 0.2 percent and 0.1 percent of shipments, respectively. 

 

e DOE notes that IEC-equivalent design types are also covered.
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Figure 3.2.1 Electric Motor Shipments by Design Type for 2011

As will be discussed in more detail in chapter 5 of the preliminary TSD, DOE focused its 

engineering analysis on NEMA Design B motors based on the popularity of the design type. 

Although NEMA Design C motors consist of a small portion of the motor market, DOE has 

separately analyzed these motors because of the different utility and performance characteristics 

that these motors have relative to Design A and B motors.

3.2.4.2 Horsepower Ratings

For 2011 NEMA supplied shipments data broken down by horsepower rating.

Figure 3.2.2 illustrates the total shipments of electric motors broken down by horsepower rating. 

As is evident by the graph, the vast majority of shipments occurred in the lower range of 

horsepower rating, with 5-horsepower being the most common rating.

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

1 2 5 10 20 30 50 75 125 200 300 400 500

Percent of Shipments

Horsepower Rating
3-26

Figure 3.2.2 Electric Motor Shipments by Horsepower Rating for 2011

3.2.4.3 Pole Configuration

NEMA also supplied 2011 shipments data broken down by pole configuration. As 

illustrated in 

Figure 3.2.3, 4-pole electric motors were by far the most commonly shipped. The next 

highest group of shipments was 2-pole motors, constituting 18 percent of all shipments. Then, 6-

pole and 8-pole motors accounted for 10 percent and 3 percent of electric motor shipments, 

respectively.

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

1 2 5 10 20 30 50 75 125 200 300 400 500

Percent of Shipments

Horsepower Rating

16.4%

70.0%

10.8%

2.9%

2-pole 4-pole 6-pole 8-pole
3-27

Figure 3.2.3 Electric Motor Shipments by Pole Configuration for 2011

3.2.4.4 Enclosure Types

Finally, NEMA provided shipment estimates broken down by enclosure types, that is, 

open or enclosed. In 2011, enclosed motors were shipped roughly three times as frequently as 

open motors. In 2011, enclosed consisted of about 77 percent of electric motor shipments and 

open electric motors consisted of about 23 percent of motor shipments.

16.4%

70.0%

10.8%

2.9%

2-pole 4-pole 6-pole 8-pole
3-28

Figure 3.2.4 Electric Motor Shipments by Enclosure Type for 2011

3.2.5 Manufacturers and Market Share

The major manufacturers that dominate the electric motor market for this rulemaking, in 

alphabetical order, are: 

• A.O. Smith Electrical Products Company;

• Baldor Electric Company;

• General Electric Company;

• Nidec Motor Corporation;

• Regal-Beloit Corporation.;

• Siemens Industry, Inc.;

• Toshiba; and

• WEG

The manufacturers identified above are all major manufacturers with diverse portfolios of 

equipment offerings, including electric motors covered under EPCA. Over the past decade, there 

has been a consolidation of motor manufacturing in the United States and this list is a result of 

those mergers and acquisitions. 

DOE does not have empirical data on the market shares of particular manufacturers of 

electric motors. Nevertheless, estimates of available cumulative data indicate that shipments of 

electric motors from these companies constitute over a significant portion of the total U.S. 

market. Further, DOE believes that the cumulative shipment estimates provided by NEMA 

constitute a good estimate of overall national shipments.
3-29

3.2.5.1 Small Businesses

Although the electric motor market is predominantly supplied by large manufacturers, 

DOE will examine those small businesses that manufacture electric motors during the NOPR 

stage of the rulemaking. In general, the Small Business Administration (SBA) defines a small 

business manufacturing enterprise for “motor and generator manufacturing” as one that has

1,000 or fewer employees. The number of employees in a small business is rolled up with the 

total employees of the parent company; it does not represent the division manufacturing electric

motors. SBA lists small business size standards for industries as they are described in the North 

American Industry Classification System (NAICS). For electric motors, the size standard is 

matched to NAICS code 335312, Motor and Generator Manufacturing.1

3.2.6 Application and Performance of Existing Equipment

The general purpose electric motors as well as the definite and special purpose electric 

motors that can be used in general purpose applications covered in the preliminary analysis are 

used in a wide range of applications that include the following: 

• blowers

• business equipment

• commercial food processing

• compressors

• conveyors

• crushers

• fans

• farm equipment

• general industrial applications

• grinders

• heating, ventilation, and air-conditioning equipment

• machine tools

• milking machines

• pumps

• winches

• woodworking machines

3.2.7 Trade Associations

DOE is aware of one trade association for manufacturers of medium electric motors, the 

National Electrical Manufacturers Association (NEMA).

3.2.7.1 National Electrical Manufacturers Association

NEMA was established as a trade association in 1926, and has since been divided into 

five core departments that provide different functions for its members. Those departments are: 

• Technical Services
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• Government Relations

• Industry Operations 

• Business Information Services

• Medical

Through these groups, NEMA establishes voluntary standards for the performance, size, 

and functionality of electrical equipment to facilitate communication among motor 

manufacturers, original equipment manufacturers, engineers, purchasing agents, and users. An

example of NEMA’s role in standardization is the NEMA Standards Publication MG-1, “Motors 

and Generators,” (MG 1) document,f which is a reference document for motor and generator 

manufacturers and users. MG 1 provides guidance to motor manufacturers on performance and 

construction specifications for a broad range of electric motors. By standardizing around certain 

parameters, NEMA makes it easier for users to identify and purchase electric motors. MG 1 is a 

complete industry reference document for standardizing the motors offered in the market. The 

groups above also set up work that NEMA, as a whole, does to contribute to U.S. public policy 

and the economic data analysis it performs.

2

In addition to MG 1, NEMA established and promoted a high efficiency standard through 

a “NEMA Premium®” label for qualifying motors.g

3.2.2

 NEMA motor manufacturers attach a label 

to motors that are built to high efficiency standards. These standards exceed those set by 

EPACT 1992, which requires general-purpose motors from 1 to 200 horsepower to meet certain 

minimum efficiency levels. See section and 3.2.9 for more discussion on these minimum 

efficiency levels.

3.2.8 Regulatory Programs

EPCA, 42 U.S.C. 6311, et seq., as amended by EPACT 1992, established energy 

conservation standards and test procedures for certain commercial and industrial electric motors 

manufactured (alone or as a component of another piece of equipment) after October 24, 1997. 

Then, in December 2007, Congress passed into law EISA 2007. (Pub. L. No. 110–140) Section 

313(b)(1) of EISA 2007 updated the energy conservation standards for those electric motors 

already covered by EPCA and established energy conservation standards for a larger scope of 

motors not previously covered. (42 U.S.C. 6313(b)(2))

EPCA also directs that the Secretary [of Energy] shall publish a final rule no later than 24 

months after the effective date of the previous final rule to determine whether to amend the 

standards in effect for such product. Any such amendment shall apply to electric motors 

manufactured after a date which is five years after –

(i) the effective date of the previous amendment; or

(ii) if the previous final rule did not amend the standards, the earliest date by which a 

previous amendment could have been effective. (42 U.S.C. 6313(b)(4))

 

f NEMA’s MG 1 document can be purchased online at www.nema.org/stds/MG 1.cfm. g NEMA’s Premium® Motors program can be reviewed at www.nema.org/gov/energy/efficiency/premium. 
3-31

As described earlier, EISA 2007 constitutes the most recent amendment to EPCA and 

energy conservation standards for electric motors. Because these amendments became effective 

on December 19, 2010, DOE is required by statute to publish a determination by December 19, 

2012, whether to further amend the EISA 2007 energy conservation standards for electric 

motors. As such, DOE will determine whether to promulgate amended energy conservation 

standards for electric motors and, if so, at what levels. Sections 325(o)-(p) of EPCA require any 

such levels to be technologically feasible, economically justified, and save a significant amount 

of energy. (42 U.S.C. 6295(o)-(p), 6316(a)) Any such amended standards that DOE establishes 

would require compliance two years after publication of a final rule. 

3.2.9 Non-Regulatory Programs

DOE reviewed voluntary programs that promote energy efficient electric motors in the 

United States, including the DOE Motor Challenge and Best Practices programs, NEMA 

Premium energy efficient motors program, and Consortium for Energy Efficiency (CEE) 

Premium Efficiency motors program.

3.2.9.1 Department of Energy Motor Challenge Program

In general, motor-driven equipment accounts for almost 70 percent of all electricity 

consumption by U.S. industries. In 1993, DOE launched its industry/government partnership, 

Motor Challenge Program with the goals of increasing the energy-efficiency of electric motordriven systems in domestic industry and enhancing environmental quality. The program uses a 

market-driven approach to promote the design, purchase, installation, and management of 

energy-efficient electric motors and motor-driven systems and equipment, such as pumps, fans, 

and compressors. It was designed to help industry capture 5 billion kilowatt-hours per year of 

electricity savings and 1.2 million metric tons of carbon-equivalent by the year 2000, with 

projections of much larger and longer-term national energy savings opportunities of over 100 

billion kilowatt-hours per year by the year 2010.h

The Motor Challenge program encompasses three-phase 60 Hertz motors rated 1 

horsepower and above. Its elements and offerings include: DOE Energy Efficiency and 

Renewable Energy (EERE) Information Center, which provides up-to-date information about the 

practicality and profitability of electric motor system strategies; design decision tools, such as 

MotorMaster+ software; Showcase Demonstration projects; training; workshops; and 

conferences. In general, the response to the program from industry has been overwhelmingly 

favorable. The Motor Challenge program is no longer active; however, the DOE Energy 

Efficiency and Renewable Energy (EERE) Information Center and the MotorMaster+ database 

of industrial motors remain viable.

The EERE Information Center answers questions on energy efficient products and 

services and refers callers to the most appropriate DOE/EERE resources. Industrial callers are 

eligible for an advanced level of service that includes engineering assistance, research, and 

 

h For more information about DOE “Best Practices,” under the DOE Industrial Technologies Program, and Motor 

Challenge, visit http://www1.eere.energy.gov/industry/bestpractices/index.html.
3-32

software support for plant staff and industrial service providers working on industrial energy 

savings projects.i

MotorMaster+ is an energy-efficient motor selection and management tool, which 

includes a database of over 20,000 AC motors. It features motor inventory management tools, 

maintenance log tracking, efficiency analysis, savings evaluation, energy accounting, and 

environmental reporting capabilities.j

3.2.9.2 National Electrical Manufacturers Association Premium Efficiency Motor

Program

On January 11, 1989, NEMA established voluntary energy efficiency levels for 1 through 

200 horsepower, polyphase squirrel-cage induction motors. For an electric motor to be classified 

as “energy efficient,” it was required to meet certain levels of efficiency in NEMA Standards 

Publication MG 1–1987 (Revised March 1991). In 1992, the NEMA efficiency levels were 

incorporated into section 342(b) of EPACT 1992 and subsequently codified in 10 CFR 431.25. 

In 2001, the NEMA Premium Efficiency Motor Program was established to provide special 

recognition to electric motors that exceed the required efficiency levels established by EPACT 

1992. NEMA Premium-labeled motors help purchasers identify more efficient motors and 

optimize motor system efficiency commensurate with a particular application.3k

Going a step beyond EPACT, NEMA Premium applies to single-speed, polyphase; 1 to 

500 horsepower; 2-, 4-, and 6-pole; squirrel-cage; induction motors; NEMA Designs A or B; 600 

volts or less; and rated for continuous duty operation.4

3.2.9.3 Consortium for Energy Efficiency

 Such electric motors are typically used in 

industrial applications operating more than 2000 hours per year. 

The Consortium for Energy Efficiency (CEE) is a nonprofit corporation that develops 

initiatives for its North American members to promote the manufacture and purchase of energy 

efficient equipment, including electric motors and services. Its members include utilities, 

statewide and regional market transformation administrators, environmental groups, research 

organizations and state energy offices in the U.S. and Canada. Also included in the CEE 

collaborative process are manufacturers, retailers, and government agencies.

In 1996, CEE began its Premium-Efficiency Motors Initiative to promote the production, 

distribution, and adoption of premium efficiency motors over motors meeting the minimum 

efficiency levels established under EPACT 1992. In 1999, CEE took a systems approach to 

energy savings and launched its Motor Systems Initiative that viewed the motor as a component 

of a larger system, where efficient motors, adjustable-speed drives, and system-specific design 

strategies would provide the greatest opportunity for savings. Then, in 2001, CEE launched its 

 

i

For more information about the EERE Information Center, visit 

http://www1.eere.energy.gov/industry/bestpractices/info_center.html. j

For more information about MotorMaster+, visit www1.eere.energy.gov/industry/bestpractices/software.html#mm. k For more information about the NEMA Premium Efficiency Motor Program, visit 

http://www.nema.org/gov/energy/efficiency/premium/.
3-33

Motor Decisions Matter to promote greater awareness of the benefits of motor systems 

efficiency. In June 2001, CEE and NEMA aligned to promote NEMA Premium motor efficiency 

levels that are roughly .5 to 3 percentage points above EPACT 1992 requirements.5

In May 2007, CEE published the Energy-Efficiency Incentive Programs – PremiumEfficiency Motors & Adjustable Speed Drives in the U.S and Canada, which provides 

information about the incentive-based programs in North America. These programs concentrate 

on 1 to 200 horsepower motors, but some include 201 to 500 horsepower motors. It appears that 

the programs cover commercial and industrial motors rated from 1 to 500 horsepower.lThere are 

a number of different programs broken down by region. For more information on these 

programs, download the report from CEE.6

3.3 TECHNOLOGY ASSESSMENT

The electric motors covered in the framework document are all AC induction motors. 

Induction motors have two core components: a stator and a rotor. The components work 

together to convert electrical energy into rotational mechanical energy. This is done by creating 

a rotating magnetic field in the stator, which induces a voltage across the rotor-stator air gap 

which in turn causes current to flow within the squirrel cage of the rotor. The squirrel cage of the 

rotor is so named because without the core steel stack, the rotor conductor bars and end rings 

resemble the exercise wheels that domesticated squirrels would run in. The stator and rotor 

magnetic fields interact to create torque. This torque provides the rotational force delivered to 

the load via a shaft.

The purpose of the technology assessment is to develop a preliminary list of technology 

options that may improve the efficiency of electric motors. For the electric motors covered in 

this rulemaking, energy efficiency losses are grouped into five main categories: stator I2R losses, 

rotor I2R losses, core losses, friction and windage losses, and stray load losses. 

Designers have to balance the five basic losses to optimize the various motor 

performance criteria. There are numerous trade-offs that have to be considered. Efficiency is 

only one parameter that has to be met. Reducing one loss may increase another. What may be 

desirable on a 4-pole motor may not be on a 2-pole motor. Increasing the air gap is a good 

example: a larger air gap may reduce the stray loss but may increase the losses associated with 

the magnetizing current. A complete discussion of these trade-offs is beyond the scope of this 

report. Different companies utilize different approaches for minimizing motor losses.

3.3.1 Technology Options for I2

R Losses

I

2

R losses are produced from either the current flow through the copper windings in the 

stator (stator I

2

R losses) or the squirrel cage of the rotor (rotor I

2

R losses). Stator I

2

R losses are 

 

l

For more information about CEE motor and motor systems programs, visit http://www.cee1.org/ind/mot-sys/mtrms-main.php3.
3-34

reduced by decreasing resistance to current flow in the electrical components of a motor. These 

losses are manifested as heat, which can shorten the service life of a motor. Another way to 

decrease stator I

2

R losses is to increase the cross sectional area of the stator winding conductors 

(e.g., copper wire diameter). This can also be accomplished by either increasing the slot fill 

and/or increasing the size of the stator slots. However, this method replaces some of the stator 

magnetic cross sectional area and increases the flux density in the stator. Increasing the flux 

density may increase core losses. The motor designer must make a trade-off between these two

options to streamline the motor design.

There are also various ways to reduce rotor I

2

R losses. Rotor conductor bars are the areas

in the rotor where current flows. These bars are usually made of aluminum in electric motors. 

However, one method of increasing the efficiency of the motor is to substitute copper bars for 

aluminum bars. Aluminum has a higher electrical resistivity (2.65 x 10-8 ohm-m) than copper 

(1.68 x 10-8 ohm-m). Copper’s 63 percent lower electrical resistance compared to aluminum 

would result in reduced rotor I

2

R losses if copper bars are used instead of aluminum.

Manipulation of the rotor’s geometrical design is another approach to reduce rotor I

2

R 

losses. The conductor bars of the rotor cage may be skewed. This means the conductor bars are 

slightly offset from one end of the rotor to the other. By skewing the rotor bars, motor designers 

can reduce harmonics that add cusps to the speed-torque characteristics of the motor. The cusps 

in the speed-torque curves mean that the acceleration of the motor will not be completely 

smooth. The degree of skew matters because reducing the skew will help reduce the rotor 

resistance and reactance, thereby providing gains in efficiency. However, reducing the skew 

may have adverse impacts on the speed-torque characteristics.

Another change to the rotor bar geometry that can reduce resistance is increasing the 

cross-sectional area of the conductor bars. Resistance is inversely proportional to the crosssectional area of the material through which current is flowing. By increasing the cross-sectional 

area, rotor bar resistance will decrease which may reduce rotor I

2

R losses. 

Manufacturers may also alter the end rings of the rotor to increase efficiency. Current 

flows through the end rings of the rotor and increasing the size of the end ring may decrease 

resistance and reduce the associated rotor I

2

R losses.

Another approach to improve motor efficiency is increasing the number of steel 

laminations to the rotor and stator (i.e., increasing the “stack” length). Increasing the stack 

length reduces the flux densities and therefore the iron loss. However, usually other parameters 

in the motor design must be modified to achieve an efficiency improvement with a longer stack 

length. Improving the grade of electrical steel used in the motor laminations will also reduce the 

iron losses.

Another way manufacturers may improve efficiency is to reduce the air gap between the 

stator and rotor. Within limits, decreasing the air gap decreases the magneto-motive force drop 

across the air gap. This will improve the motor’s power factor and reduce stator I2

R losses. 

Reducing the air gap has some manufacturing limitations and it may also increase other loss 

components, so again design optimization is a must.
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3.3.2 Technology Options for Core Losses

Core losses are losses created in the electrical steel components of a motor. These losses, 

like I2

R losses, manifest themselves as heat. Core losses are generated in the steel by two 

electromagnetic phenomena: hysteresis losses and eddy currents. Hysteresis losses are caused by 

magnetic domains resisting reorientation to the alternating magnetic field (i.e., 60 times per 

second, or 60 hertz). Eddy currents are currents that are induced in the steel laminations by the 

pulsating magnetic flux.

Another common technique for reducing steel losses is using a higher quality, more 

efficient electrical steel in the core. Hysteresis losses are reduced because the magnetic 

permeability improves and grain size increases, reducing the magnetic domain resistance. Eddy 

currents are reduced because the resistivity of the laminations is higher, reducing the magnitude 

of the currents. In studying the techniques used to reduce steel losses, DOE considered two types 

of materials: conventional silicon steel and so-called “exotic” steels, which contain a relatively 

high percentage of boron or cobalt.

Conventional steels are commonly used in electric motors manufactured today. There are 

three types of steel that DOE considers “conventional” or cold-rolled magnetic laminations 

(CRML), fully processed non-oriented electrical steel, and semi-processed non-oriented 

electrical steel. Each steel type is sold in a range of grades. In general, as the grade number goes 

down, so does the amount of loss associated with the steel (i.e., watts of loss per pound of steel). 

The induction saturation level also drops, causing the need for increased stack length. Of these 

three types, CRML steels are the most commonly used, but also the least efficient. The fully 

processed steels are annealed before punching and therefore do not require annealing after being 

punched and assembled, and are available in a range of steel grades from M56 through M15. 

Semi-processed electrical steels are designed for annealing after punching and assembly.

The exotic steels are generally not manufactured for specific use in electric motors. 

However, these steels offer a lower loss level than the best electrical steels, but are more 

expensive per pound. From a manufacturing perspective, these steels also present problems 

because they come in non-standard thicknesses that are harder to manufacture.

Another possible option for reducing core loss is to use thinner laminations. Thinner 

laminations generally have less eddy current losses and this contributes toward improving motor 

efficiency.

Manufacturers may also reduce eddy currents by using improved insulating coatings 

between the steel laminations. Improved coatings increase the resistance between the steel 

laminations, which makes it more difficult for eddy currents to flow from lamination to 

lamination.

Annealing the core steel is another technique manufacturers use to reduce hysteresis 

losses. Annealing is a heating process that alters the grain structure of the steel and alleviates any 

stresses introduced during punching and assembly. After being annealed, the material becomes 

much easier to magnetize, which means the magnetic domains reorient more easily. 

Manufacturers will incur more cost if they anneal the steel because they are adding another step 
3-36

to the manufacturing process and that increases production time. The necessary annealing 

equipment also requires a large capital investment.

Table 3.8 presents the core steels used in manufacturing electric motors, including some 

more efficient steels that are not as common, which DOE considered in its analysis. In addition 

to the steel grade name, the table presents nominal thickness and core losses at a fixed magnetic 

flux density.

Table 3.8 Core Steel Grades, Thicknesses, and Associated Losses

Steel 

Grade

Nominal 

Thickness 

(inches)

Core Loss at 60 Hz

Watts per Pound at 

Magnetic Flux Density

Remarks

24 M56* 0.025 4.30 Watts/lb at 1.5 T† Cold-rolled magnetic laminations (semiprocessed)

26 M47* 0.019 2.80 Watts/lb at 1.5 T Non-oriented electrical steel (fully 

processed)

24 M36* 0.025 2.35 Watts/lb at 1.5 T Non-oriented electrical steel (fully 

processed)

24 M19* 0.025 2.00 Watts/lb at 1.5 T Non-oriented electrical steel (fully 

processed)

29 M15* 0.014 1.45 Watts/lb at 1.5 T Non-oriented electrical steel (fully 

processed)

Hiperco 

50 0.006 1.00 Watts/lb at 1.5 T Iron-cobalt-vanadium soft magnetic alloy

* Denotes a steel used in the engineering analysis.

†

Watts of loss per pound of core steel are only comparable at the same magnetic flux density, measured in tesla. The 

tesla (symbol T) is the SI-derived unit of magnetic field, which is also known as "magnetic flux density.”

3.3.2.1 Plastic Bonded Iron Powder

Recently, DOE became aware of a new technology that Lund University researchers in 

Sweden developed in the production of magnetic components for electric motors from plastic 

bonded iron powder (PBIP). The technique has the potential to cut production costs by 50 

percent while doubling motor output.

The method uses two main ingredients: metal powder and plastics. Combining the 

ingredients creates a material with low conductivity and high permeability. The metal particles 

are surrounded by an insulating plastic, which prevents electric current from developing in the 

material. This is critical because it essentially eliminates losses in the core due to eddy currents. 

Properties of PBIP can differ depending on the processing. If the metal particles are too closely 

compacted and begin to touch, the material will gain electrical conductivity, counteracting one of 

its most important features.
3-37

Another advantage of PBIP is a reduction in the number of production steps. The 

number of steps in manufacturing a rotor and stator is reduced from roughly 60 to just a few. A 

second way to increase savings is to build an inductor with PBIP. During processing, the plastic 

and metal are molded together using a centrifugal force. During this process, the inductor core 

consisting of PBIP and pre-wound windings are baked into the core. This inductor is then used 

as a filter for grid power application. The filter then reduces the use of cooling equipment in the 

motor design.7

3.3.3 Technology Options for Friction and Windage Losses

Bearing friction and the cooling fan system create what is called “friction and windage 

losses” in AC induction motors. The bearing friction also adds heat to the motor’s system which

adds losses and decreases the motor’s efficiency.

To decrease the losses caused by motor bearings, manufacturers can change the bearings 

or bearing lubricant. Less friction, and thus less heat, is produced when manufacturers use a 

better bearing structure or bearing lubricant, but manufacturers must also consider issues such as 

temperature rating and speed. 

Another way to reduce heat in an induction motor is to use a better cooling system. 

Changing the fan or adding baffles to the ventilation system can help reduce the motor 

temperature rise and therefore losses. Baffles help redirect airflow through the motor, creating 

better circulation and an overall cooler-running motor. With a well-designed cooling system, the 

motor should run more efficiently. 

3.3.4 Technology Options for Stray-Load Losses

 Stray-load loss is defined as the difference between the total motor loss and the sum of the 

other four losses referred to above. Stray-load loss is caused by many factors. Manufacturers 

alter different design parameters to reduce stray-load losses, including slot combination, skew, 

rotor cage insulation, etc. Stator and rotor lamination design can contribute toward reducing the 

high frequency losses that occur to some degree in all induction motors. Careful attention to the 

design and manufacturing processing of the motor can significantly reduce the stray-load loss.

3.3.5 Summary of the Technology Options Under Consideration

Table 3.9 summarizes the technology options discussed in this preliminary TSD 

technology assessment and those that DOE will consider in the screening analysis (see chapter 

4). The options that pass all four screening criteria are considered “design options” and are used 

in the engineering analysis (see preliminary TSD chapter 5) as a means of improving the

efficiency of electric motors.
3-38

Table 3.9 Summary of Technology Options for Improving Efficiency

Type of Loss to Reduce Technology Option Applied

Stator I2R Losses

Increase copper wire diameter to maximize slot fill

Reduce end turn length

Increase stator slot size

Rotor I2R Losses

Reduce rotor resistance by a change in volume or material 

conductivity

Increase rotor slot size

Manipulation rotor slot configuration

Core Losses

Select lamination with less watts loss/pound

Optimize air gap

Improve annealing process

Add stack height (i.e., add electrical steel)

Friction and Windage Losses Optimize bearing or lubrication selection

Improve cooling system design

Stray-Load Losses

Optimize selection of rotor/stator slot combination

Improve stator/rotor slot lamination designs

Improve rotor surface machining

Most of the design changes suggested in Table 3.9 produce interacting effects on the 

motor’s breakdown torque, locked rotor torque, locked rotor current, and so forth. Therefore, 

motor designers making a specific design change must evaluate the effects against all of a

motor’s performance characteristics and not just focus on efficiency.
3-39

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