CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT
 

TABLE OF CONTENTS
 

3.1 INTRODUCTION .............................................................................................................. 1
 

3.2 MARKET ASSESSMENT ................................................................................................. 1
 

3.2.1 Small Electric Motor Definition ............................................................................. 1
 

3.2.1.1 General-Purpose Alternating-Current Motor.............................................. 3
 

3.2.1.2 Categories of Induction Motors .................................................................. 5
 

3.2.1.3 Frame Series and Metric Equivalents ......................................................... 6
 

3.2.1.4 Motor Enclosure.......................................................................................... 8
 

3.2.2 Small Electric Motor Nameplates and Terminology .............................................. 9
 

3.2.3 Manufacturers and Market Share.......................................................................... 12
 

3.2.3.1 Small Businesses....................................................................................... 12
 

3.2.4 Application and Performance of Existing Equipment .......................................... 13
 

3.2.5 Trade Associations................................................................................................ 13
 

3.2.5.1 National Electrical Manufacturers Association ........................................ 13
 

3.2.5.2 The Motors and Motion Association ........................................................ 14
 

3.2.6 Regulatory Programs ............................................................................................ 14
 

3.2.7 Non-Regulatory Programs .................................................................................... 15
 

3.2.7.1 Department of Energy Motor Challenge Program.................................... 15
 

3.2.7.2 National Electrical Manufacturers Association Premium Efficiency Motor 

Program..................................................................................................... 16
 

3.2.7.3 Consortium for Energy Efficiency............................................................ 17
 

3.3 TECHNOLOGY ASSESSMENT..................................................................................... 18
 

3.3.1 Technology Options for I2

R Losses...................................................................... 18
 

3.3.2 Technology Options for Core Losses ................................................................... 20
 

3.3.2.1 Plastic Bonded Iron Powder...................................................................... 22
 

3.3.3 Technology Options for Friction and Windage Losses ........................................ 23
 

3.3.4 Technology Options for Stray Load Losses.......................................................... 23
 

3.3.5 Summary of the Technology Options Under Consideration................................. 23
 

LIST OF TABLES 

Table 3.2.1. National Electrical Manufacturers Association Standard MG1–1987 Service Factor 

Requirements of Small Electric Motors ...................................................................... 4
 

Table 3.2.2. Minimum Locked-Rotor Torque, Ounce-Feet*.......................................................... 5
 

Table 3.2.3. Required Small Electric Motor Nameplate Information........................................... 11
 

Table 3.2.4. Optional Small Electric Motor Nameplate Information ........................................... 12
 

Table 3.3.1. Core Steel Grades, Thicknesses, and Associated Losses.......................................... 22
 

Table 3.3.2. Summary of Technology Options for Improving Efficiency.................................... 24
 

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CHAPTER 3. MARKET AND TECHNOLOGY ASSESSMENT
 

3.1 INTRODUCTION 

This chapter details the market and technology assessment that the U.S. Department of 

Energy (DOE) conducted in support of its energy conservation standards rulemaking for small 

electric motors. The small electric motors rulemaking was initiated under the Energy Policy and 

Conservation Act (EPCA), Public Law 94–163, as amended, by the Energy Policy Act of 1992 

(EPACT 1992), Public Law 102–486. The statute requires that, if DOE were to adopt energy 

conservation standards for small electric motors, they would become effective to small electric 

motors manufactured five years after the publication date of the final rule.a 

This chapter consists of two major sections, the market assessment and the technology 

assessment. The goal of the market assessment is to develop a qualitative and quantitative 

characterization of the small electric motors industry. This assessment characterizes the market 

structure based on publicly available information as well as data supplied by manufacturers and 

other interested parties. Issues include manufacturer characteristics and market shares, existing 

regulatory and non-regulatory efficiency improvement programs, product classes, and trends in 

market and equipment characteristics. The goal of the technology assessment is to develop a list 

of technology options that manufacturers can use to improve the efficiency of small electric 

motors. 

3.2 MARKET ASSESSMENT 

This section addresses the scope of the rulemaking, identifies potential product classes, 

estimates national shipments of small electric motors, and the market shares of small electric 

motor manufacturers. This section also addresses typical equipment lifetimes and market 

performance data, and discusses regulatory and non-regulatory programs that apply to small 

electric motors. 

3.2.1 Small Electric Motor Definition 

One of the key documents that relates to the scope of coverage for small electric motors is 

the National Electrical Manufacturers Association (NEMA) Standards Publication MG1 for 

Motors and Generators. NEMA drafted and maintains the MG1 document, most recently revised 

in November 2007 as MG1–2006 with Revision 1. MG1 assists users in the correct selection 

and application of electric motors and generators. MG1 provides practical information to small 

a

 A Final Rule for Small Electric Motors is scheduled to be published by February 28, 2010. Under section 

346(b)(3), any standard for small electric motors “shall apply to small electric motors manufactured 60 months after 

the date such rule is published or, in the case of small electric motors which require listing or certification by a 

nationally recognized test laboratory, 84 months after such date.” (42 U.S.C. 6317(b)(3)) Thus, if DOE does adopt 

energy conservation standards for small electric motors, it is anticipated that these standards would apply to small 

electric motors manufactured after February 28, 2015 and February 28, 2017, respectively. 

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electric motor manufacturers and users concerning the construction, testing, performance, and 

safety of alternating current (AC) and direct current (DC) motors and generators. 

The term “small electric motor” is defined in the statute, and thus, the scope of coverage 

for this rulemaking is determined by this statutory definition. Section 340(13)(G) of EPCA 

defines the term “small electric motor” to mean “a NEMA general-purpose alternating currentb 

single-speed induction motor,c built in a two-digit frame number seriesd in accordance with 

NEMA Standards Publication MG1–1987.” (42 U.S.C. 6311(13)(G)) Such motors include 

single-phase, capacitor-start induction-run (CSIR), capacitor-start capacitor-run (CSCR), and 

polyphase motors. DOE addresses the scope of small electric motors covered in the sections that 

follow, noting that today’s scope is slightly narrower than what DOE considered for the 

determination analysis. See 

http://www1.eere.energy.gov/buildings/appliance_standards/commercial/small_electric_motors.h 

tml. 

Section 346(b)(3) of EPCA (42 U.S.C. 6317(b)(3)) requires that a standard prescribed for 

small electric motors shall not apply to any small electric motor that is a component of a covered 

product under section 322(a) of EPCA (42 U.S.C. 6292(a)) or of covered equipment under 

section 340 of EPCA. (42 U.S.C. 6311) Such products and equipment include, for example, 

residential air conditioners and heat pumps, furnaces, refrigerators and freezers, clothes washers 

and dryers, commercial packaged air-conditioning and heating equipment, and commercial 

refrigeration equipment. Accordingly, the analysis does not include small electric motors 

incorporated into residential and commercial products either covered or specifically excluded by 

statute. 

On July 10, 2006, DOE published in the Federal Register its determination that energy 

conservation standards for small electric motors appear to be technologically feasible and 

economically justified, and would result in significant energy savings. 71 FR 38807. A key 

issue that arose early in the analytical process was interpretation of the EPCA definition of a 

small electric motor and precisely which motors are covered. The EPCA definition identifies 

several key terms that are defined in NEMA MG1–1987, such as general purpose, alternatingcurrent and two-digit frame series. Thus, EPCA’s definition of a small electric motor is tied to 

NEMA MG1–1987 terminology and performance requirements established for (1) generalpurpose alternating-current motors, (2) various categories of induction motors, and (3) the 

b

 “General-purpose alternating current” is a term that NEMA uses for alternating-current motors that are not 

designed with a specific application in mind. 

c

 An induction motor converts electrical power into rotational mechanical power. It depends on electromagnetic 

induction for its operation and has one or more component members capable of rotary movement. 

d

 The terms “two-digit frame number series” and “frame series” refer to a motor’s standard system of numbers in 

combination with letters for designating the size and mounting dimensions of a motor, according to NEMA 

Standards Publication MG1, “Motors and Generators.” In the case of small motors, frame series is the “D” 

dimension in inches multiplied by 16. The “D” dimension is measured from the centerline of the shaft to the bottom 

of the mounting feet. For example, a 48-frame motor would have a “D” dimension of 3.00 inches (16 x 3.00 = 48). 

Such standard dimensions are essential to fitting a motor to the equipment it drives and for interchangeability among 

motors. 

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definition of two-digit frame number series. In the following subsections, DOE addresses 

elements of the definition of “small electric motor” that need clarification. 

3.2.1.1 General-Purpose Alternating-Current Motor 

One element in the statutory definition of small electric motors that derives from NEMA 

MG1–1987, is “general-purpose, alternating-current.” Paragraph MG1–1.05 sets forth the 

definition: 

A general-purpose alternating-current motor is an induction motor, rated 200 horsepower 

and less, which incorporates all of the following: (1) open constructione, (2) rated 

continuous duty, (3) service factor in accordance with MG1-12.47, and (4) Class A 

insulation system with a temperature rise as specified in MG1-12.42 for small electric 

motors or Class B insulation system with a temperature rise as specified in MG1-12.43 for 

medium motors. It is designed in standard ratings with standard operating characteristics 

and mechanical construction for use under usual service conditions without restriction to a 

particular application or type of application. 

The four criteria that NEMA used in MG1-1987 to define a general-purpose alternatingcurrent motor are open construction, continuous duty, service factor, and a Class A insulation 

system. 

Open construction refers to the type of enclosure that houses the motor. An open 

construction enclosure allows outside air to pass through and cool the motor when it is operating. 

Electric motors are also manufactured with closed construction housings, which do not circulate 

external air for cooling. 

A motor rated for continuous duty can operate a driven machine indefinitely at the rated 

load, speed, and temperature without injury to the motor. The statutory language directs DOE to 

cover and evaluate general-purpose alternating-current motors, which are rated for continuous 

duty (as opposed to intermittent duty). Therefore, in this rulemaking, DOE proposes to cover 

only those motors rated for continuous duty. 

MG1–1987 defines general-purpose alternating-current motors as having a service factor 

in accordance with MG1–12.47. The service factor is a measure of the overload capacity at 

which a motor can operate without damage, while operating normally within the correct voltage 

tolerances. The rated horsepower (hp) multiplied by the service factor gives that overload 

capacity. For example, a 1-horsepower motor with a 1.25 service factor can operate at 1.25 

horsepower (1 horsepower x 1.25 service factor). NEMA MG1–1987 requires that the service 

factor for general-purpose alternating-current motors be in accordance with MG1–12.47. (See 

e

 NEMA MG1–1987 defines each of the following motors, in part, as “an open machine”: drip-proof, splash-proof, 

semi-guarded, guarded, dripproof guarded, open externally ventilated, open pipe-ventilated, and weather-protected 

(Type I and Type II). 

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Table 3.2.1.) Therefore, in this rulemaking, DOE proposes to cover only those small electric 

motors that meet the NEMA service factor requirements. 

Table 3.2.1. National Electrical Manufacturers Association Standard MG1–1987 Service 

Factor Requirements of Small Electric Motors 

Horsepower Required Service Factors by Synchronous Speed (rpm) 

3,600 1,800 1,200 

1/4 1.35 1.35 1.35 

1/3 1.35 1.35 1.35 

1/2 1.25 1.25 1.25 

3/4 1.25 1.25 -

1 1.25 - -

The MG1–1987 definition of “general-purpose alternating-current motor,” in part 

identifies a small electric motor as one that incorporates a Class A insulation system with a 

temperature rise as specified in MG1–12.42. This paragraph establishes the maximum 

temperature rise of the various parts of the motor, over a 40°C ambient temperature. For 

example, the temperature rise of the windings of a small electric motor with open construction 

and a Class A insulation system shall not exceed 60°C; if the motor’s service factor is greater 

than 1.15, it shall not exceed 70°C. However, MG1-1987 also defines Class B, F, and H 

insulation systems. DOE believes that, because any of these insulations systems also meets the 

specification of a Class A system and they are regularly used in small electric motors, they are 

covered. 

Lastly, MG1–1987 requires that a general-purpose alternating-current motor be designed 

in standard ratings with standard operating characteristics and mechanical construction for use 

under usual service conditions without restriction to a particular application or type of 

application. This provision is consistent with the definition of “general-purpose motor” under 

section 431.12 of Title 10 of the Code of Federal Regulations, Part 431 (10 CFR Part 431). 

Essentially, both MG1–1.05 and 10 CFR 431.12 require general-purpose motors to meet 

“standard ratings,” which are generally understood to mean any performance or physical 

characteristics established as a rule or model by authority, custom, or general consent. The 

NEMA Standard MG1 is based on general consent, meaning that NEMA members who 

manufacture motors and generators covered in MG1 can vote to approve the document. 

For small electric motors, examples of standard ratings include minimum breakdown 

torque (see NEMA MG1–12.32.1 and Table 10-5, for single-phase motors) and minimum 

locked-rotor torque (see NEMA MG1–12.32.2, for single-phase motors). Such requirements 

limit the scope of covered small electric motors. For example, the breakdown torques of many 

shaded-pole and permanent-split capacitor motors (which are single-phase motors) do not fall 

within the breakdown torque ranges of MG1-1987 Table 10–5. Section 12.32.2 of MG1-1987 

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requires that the locked-rotor torque for single-phase motors shall be no less than the values 

presented in Table 3.2.2. 

Table 3.2.2. Minimum Locked-Rotor Torque for Single-Phase Small Motors, Ounce-Feet* 

Horsepower 60-Hz Synchronous Speed (RPM) 

3,600 1,800 1,200 

1/4 21 46 59 

1/3 26 57 73 

1/2 37 85 100 

3/4 50 119 -

1 61 - -

* On the high voltage connection of dual voltage motors, minimum locked-rotor torques up to 10 percent less than 

these values may be expected. 

** Each value in this table depicts the ounce-feet of locked-rotor torque for this combination of horsepower and 

synchronous speed. For this particular combination (i.e., 1/4 horsepower with a speed between 3,450 and 3,600 

rpm), manufacturers must ensure that the motor has at least 21 ounce-feet of locked rotor torque to meet this 

requirement of NEMA MG1–1987. 

Of the motors satisfying the frame-size requirement of the EPCA definition of “small 

electric motor” and “built in a two-digit frame number series in accordance with NEMA 

Standards Publication MG1–1987,” only a subset incorporates the other performance 

requirements of a general-purpose motor under NEMA MG1–1987, paragraph 1.05. Among 

single-phase motors with a two-digit frame series, DOE found that only capacitor-start motors– 

including capacitor-start induction-run, and capacitor-start capacitor-run motors–can meet the 

torque requirements for NEMA general-purpose motors. Among three-phase small electric 

motors, only non-servo motors can meet the NEMA performance requirements for generalpurpose motors. Hence, DOE’s analysis only covers the capacitor-start categories of singlephase motors and three-phase small electric motors. 

3.2.1.2 Categories of Induction Motors 

The statutory definition also requires that a small electric motor be a single-speed 

induction motor” built in accordance with NEMA MG1–1987. DOE identified six categories of 

alternating current single-speed induction motors: split-phase,f

 shaded-pole,g capacitor-start 

(both CSIRh and CSCRi), permanent-split capacitor (PSC),j and polyphase.k In the discussion 

f

 A split-phase motor is a single-phase induction motor equipped with an auxiliary winding displaced in magnetic 

position from, and connected parallel to, the main winding. Unless otherwise specified, DOE assumed that the 

auxiliary circuit is open when the motor attains a predetermined speed. The term “split-phase motor” describes a 

motor to be used without impedance other than that offered by the motor windings themselves. 

g

 A shaded-pole motor is a single-phase induction motor provided with an auxiliary short-circuited winding or 

windings displaced in magnetic position from the main winding.

h

 A capacitor-start, induction-run motor is a single-phase motor with a main winding arranged for direct connection 

to a source of power and an auxiliary winding connected in series with a capacitor. The motor has a capacitor phase, 

which is in the circuit only during the starting period. 

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that follows, DOE explains its review of these six induction motor categories and its conclusion 

that the CSIR, CSCR, and polyphase motors are the only three categories which are covered 

under EPCA. 

DOE eliminated split-phase, PSC, and shaded-pole motors from consideration because 

they are not designed as and do not meet the performance requirements of general-purpose 

motors. Split-phase motors are designed for specific purposes and applications, and generally 

for applications that are short-time rated. Also, split-phase motors do not meet the breakdown 

torque requirements or the locked-rotor torque requirements while simultaneously maintaining 

the locked-rotor current requirements that have been established in NEMA for general-purpose 

motors. In some cases, split-phase motors are components of products covered under EPCA 

sections 322(a) and 340, 42 U.S.C. 6292(a) and 6311, respectively and are otherwise excluded 

from coverage by statute. (42 U.S.C. 6317(b)(3)) Similarly, PSC motors used in fans, business 

machines, and hermetic motor compressors do not meet the torque requirements for NEMA 

general-purpose motors. Shaded-pole motors that are generally intended for intermittent 

operation in applications such as rotisseries, fans, humidifiers, small business machines, 

advertising machines, copiers, vending machines and advertising displays also do not meet the 

performance requirements. These shaded-pole motors tend to have low efficiency ratings (i.e., 

less than 50 percent) and are sold in high volume. However, DOE believes that because PSC 

and shaded-pole motors do not meet the performance characteristics for NEMA general-purpose 

motors, which are required under EPCA section 340(13)(G), 42 U.S.C. 6311(13)(G), and 

identified in NEMA MG1–1.05, and therefore are not covered categories of induction motors. 

The remaining categories of small electric motors include CSIR, CSCR, and polyphase. 

In view of its July 2006 determination (71 FR 38799), DOE re-examined the standard 

performance characteristics, construction specifications, and ratings for these three motor 

categories. DOE concluded that they meet the EPCA requirements for small electric motors. 

Furthermore, CSIR, CSCR, and polyphase small electric motors are manufactured in two-digit 

frame series, can be rated for continuous-duty applications, and can meet other performance 

requirements for general-purpose motors, including the torque requirements under NEMA MG1– 

1987, paragraph 12.32 for single-phase motors. Therefore, DOE will address three categories of 

small electric motors in today’s rulemaking: single-phase CSIR, single-phase CSCR, and 

polyphase. 

3.2.1.3 Frame Series and Metric Equivalents 

Another element in the statutory definition is that a small electric motor is “built in a twodigit frame number series in accordance with NEMA Standards Publication MG1–1987.” 

NEMA MG1–1987 establishes a system of numbers and letters for designating motor frames. 

i

 A capacitor-start, capacitor-run motor is a single-phase motor with different values of effective capacitance for the 

starting and running conditions. 

j

 A permanent-split capacitor motor is another category of single-phase motor that has the same value of capacitance 

for both starting and running conditions. 

k

 A polyphase motor is an electric motor that uses the phase changes of the electrical supply to induce a rotational 

magnetic field and thereby supply torque to the rotor. 

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The frame number for a small electric motor is determined by measuring the distance in inches 

between the centerline of the shaft to the bottom of the mounting feet multiplied by 16. The twodigit frame series encompasses NEMA frame series 42, 48, and 56. Two-digit NEMA frames 

have standard dimensions and tolerances specified in NEMA Standard MG1-1987 paragraphs 

11.31 and 11.34, which are necessary for mounting and interchangeability among generalpurpose applications. 

DOE understands that manufacturers produce other two-digit frame series, namely a 66 

frame series. The 66 frame series is used for definite-purpose or special-purpose motors and not 

used in general-purpose applications and therefore not covered under the EPCA definition of 

“small electric motor.” At this time, DOE is unaware of any other motors with frame series that 

are built in accordance with NEMA MG1-1987, but should such frame series appear, DOE will 

evaluate whether or not they are included equipment at that time. 

DOE is concerned about metric equivalents for the two-digit NEMA frame series, the 

uncertainty about cross-references, and the potential issues with imports of small electric motors, 

whether manufactured alone or as a component of another piece of equipment. 

EPCA section 340(13)(F), as amended by EPCA 1992, 42 U.S.C. 6311(13)(F), defines 

small electric motors in terms of “NEMA Standards Publication MG1–1987,” whose 

construction and rating system uses English units of measurement and output ratings in 

horsepower. l In contrast, general-purpose electric motors manufactured outside the United 

States and Canada are defined and described with reference to the International Electrotechnical 

Commission (IEC) Standard 60034–1 series, “Rotating electrical machines,” which use different 

terminology and criteria than EPCA. The performance attributes of these IEC motors are rated 

pursuant to IEC Standard 60034–1, “Rating and performance,” which uses metric units of 

measurement, a different construction and rating system than NEMA MG1–1987, and output 

ratings in kilowatts instead of output ratings in horsepower. Standards exist, such as the Institute 

of Electrical and Electronics Engineers Standard 112, which define the relationship between 

horsepower and watts or kilowatts. Further, 10 CFR 431.12 (2008) defines “electric motor” in 

terms of NEMA and IEC equivalents, and 10 CFR 431.25 provides a table of horsepower and 

kilowatt equivalent ratings, which DOE views as a precedent for similar treatment of small 

electric motors. 

Although the statutory definition of small electric motor does not address metric or 

kilowatt-rated motors, DOE believes that EPCA covers any motor that is equivalent to or can be 

used as a substitute for a covered small electric motor. Generally, IEC metric or kilowattequivalent motors can perform the identical functions of small electric motors and provide 

comparable rotational mechanical power to the same machines or equipment. In other words, 

IEC metric or kilowatt-equivalent motors can be interchanged with small electric motors as 

defined by NEMA standards. A given commercial central air conditioner, for example, could 

operate with either an IEC motor or NEMA motor with little or no effect on performance. 

Therefore, DOE interprets EPCA to mean that a “small electric motor” is any motor that is 

l

 The Energy Independence and Security Act of 2007 (EISA 2007), renumbered EPCA section 340(13)(F) 

(42 U.S.C. 6311(13)(F)) to be section 340(13)(G) (42 U.S.C. 6311(13)(G)). There was no change in the language. 

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identical or equivalent to a motor constructed and rated in accordance with NEMA MG1 and 

covered by the statute. Otherwise, placing energy efficiency requirements on NEMA small 

electric motors, but not on equivalent IEC or kilowatt-rated small electric motors, could give 

preferential treatment to the latter, should DOE establish minimum energy conservation 

standards for the NEMA small electric motors, but not the IEC equivalent motors. 

3.2.1.4 Motor Enclosure 

DOE examined the definition of “general-purpose, alternating-current” motor as it 

appears in NEMA Standard MG1–1987. It explicitly states that a general-purpose, alternatingcurrent motor incorporates an “open construction.” Later versions of NEMA Standard MG1 

revised the definition and expanded it to incorporate open or enclosed construction. However, 

this is not the case with the EPCA-directed definition. DOE considered this and believes that the 

reference MG1-1987 applies to all facets of the statutory definition of a small electric motor. 

The language of the statute specifies that the requirements of MG1-1987 apply in determining 

what constitutes a small electric motor. DOE's application of that definition is consistent with 

that language. Similarly, because the statute specifically mentions MG1-1987 as the version of 

MG1 on which DOE should relay, the 1987 version is the only applicable version of NEMA 

MG1. Accordingly, consistent with MG1-1987, only CSIR, CSCR, and polyphase motors with 

open construction meet the statutory definition. 

DOE considered poly- and single-phase motors, including non-servo three-phase motors; 

capacitor-start, induction-run motors; and capacitor-start, capacitor-run motors. Only those 

motors that are built with an open construction are applicable. Horsepower ranges and pole 

configurations are also important characteristics of covered motors. Table 3.2.3 through Table 

3.2.5 present the 72 product classes (PC) for polyphase, CSIR and CSCR motors, broken down 

by number of poles and horsepower/standard kilowatt equivalent ratings. Should DOE establish 

minimum energy conservation standards for small electric motors, each “PC” cell in the 

following table would be replaced by the applicable nominal full-load efficiency value. 

Table 3.2.3. Polyphase Small Electric Motor Product classes 

Horsepower/Standard 

Kilowatt Equivalent 

Six Poles Four Poles Two Poles 

1/4 hp/0.18 kW PC #1 PC #2 PC #3 

1/3 hp/0.25 kW PC #4 PC #5 PC #6 

1/2 hp/0.37 kW PC #7 PC #8 PC #9 

3/4 hp/0.55 kW PC #10 PC #11 PC #12 

1 hp/0.75 kW PC #13 PC #14 PC #15 

11⁄2 hp/1.1 kW PC #16 PC #17 PC #18 

2 hp/1.5 kW PC #19 PC #20 PC #21 

≥ 3 hp/2.2 kW PC #22 PC #23 PC #24 

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Table 3.2.4. Capacitor-Start, Induction-Run Small Electric Motor Product classes 

Horsepower/Standard 

Kilowatt Equivalent 

Six Poles Four Poles Two Poles 

1/4 hp/0.18 kW PC #25 PC #26 PC #27 

1/3 hp/0.25 kW PC #28 PC #29 PC #30 

1/2 hp/0.37 kW PC #31 PC #32 PC #33 

3/4 hp/0.55 kW PC #34 PC #35 PC #36 

1 hp/0.75 kW PC #37 PC #38 PC #39 

11⁄2 hp/1.1 kW PC #40 PC #41 PC #42 

2 hp/1.5 kW PC #43 PC #44 PC #45 

≥ 3 hp/2.2 kW PC #46 PC #47 PC #48 

Table 3.2.5. Capacitor-Start, Capacitor-Run Small Electric Motor Product classes 

Horsepower/Standard 

Kilowatt Equivalent 

Six Poles Four Poles Two Poles 

1/4 hp/0.18 kW PC #49 PC #50 PC #51 

1/3 hp/0.25 kW PC #52 PC #53 PC #54 

1/2 hp/0.37 kW PC #55 PC #56 PC #57 

3/4 hp/0.55 kW PC #58 PC #59 PC #60 

1 hp/0.75 kW PC #61 PC #62 PC #63 

11⁄2 hp/1.1 kW PC #64 PC #65 PC #66 

2 hp/1.5 kW PC #67 PC #68 PC #69 

≥ 3 hp/2.2 kW PC #70 PC #71 PC #72 

3.2.2 Small Electric Motor Nameplates and Terminology 

The National Fire Protection Association (NFPA) Standard 70, “National Electrical 

Code,” article 430.7, and NEMA MG1 paragraph 10.39 prescribe a consistent set of required 

information that is reported on all motor nameplates. This information enables a motor user to 

purchase and install a motor that is appropriate for a particular application. NFPA Standard 70 

and MG1 each require that an electric motor nameplate be marked with information that 

includes, but is not limited to: 

• manufacturer's name; 

• frame designation; 

• rated voltage; 

• rated full-load current; 

• rated frequency; 

• number of phases; 

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• rated full-load speed; 

• rated temperature rise or the insulation system class and rated ambient temperature; 

• rated horsepower; 

• time rating; 

• code letter for locked-rotor amperes; and 

• thermal protection. 

In the following table, DOE provides a brief description of each of the fields that NFPA 

70 or NEMA Standard MG1 require on the motor nameplate. 

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Table 3.2.6. Required Small Electric Motor Nameplate Information 

Frame 

Designation 

Frame series numbers represent standardized designations for size and 

dimensions. For small electric motors, the frame series are two digits, 

determined by the shaft height of the motor from the bottom of the base in 

sixteenths of an inch. For example, a 56-frame motor would have a shaft 

height (“D” dimension) of 56/16 of an inch, or 3.5 inches. For metric 

motors, the frame series is also the shaft height of the motor from the bottom 

of the base, but the height is noted in millimeters rather than sixteenths of an 

inch. 

Rated Voltage Rated voltage is the design voltage at which an electric motor will yield 

optimal performance. In general, motors should be capable of operating 

within a 20% band of the rated voltage, 10% above to 10% below. 

Rated Full-Load 

Amperage 

The rated full-load amperage represents the amperage consumption when the 

motor reaches full-load torque. The value is determined by testing a sample 

of motors, and is usually rounded up to allow for slight variations in 

manufacturing that may increase the full-load amperes. The purpose of the 

full-load amperes is to enable appropriate sizing of power supply wiring and 

any overload protection devices. 

Frequency For the North American market, motors are designed to operate on 

alternating current at 60 Hertz (cycles per second). 

Phase Single-phase and three-phase motors are available in the United States. 

Rated Full-Load 

Speed 

The rated full-load speed is the approximate rotations per minute of the 

motor under full-load conditions at a specified voltage and frequency. The 

full-load speed is typically 95% to 99% of the no-load speed. 

Insulation Class 

and Rated 

Ambient 

Temperature 

Insulation class and allowable maximum ambient temperature denote the 

operating parameters of an electric motor, which directly relates to motor 

operating life. The maximum temperature (i.e., hot spot) is a combination of 

motor design and ambient temperature. 

Rated 

Horsepower 

Rated horsepower is a measure of how much work a motor is expected to 

perform. Horsepower is based on full-load speed and torque rating, as 

follows: 

Horsepower (hp) = [(Motor Speed) × (Torque (lb-ft))] ÷ 5,250. 

Time Rating Time rating states whether the motor is rated for continuous duty (24 hours 

per day / 7 days per week) or certain “short-time” requirements, ranging 

from 5 to 60 minutes. In this rulemaking, all small electric motors are rated 

for continuous duty. 

Locked-Rotor 

Code Letter 

Starting an AC motor creates an inrush current that is usually several times 

greater than the full-load current. The inrush current may be large enough to 

cause a voltage dip that affects other equipment. Manufacturers provide the 

inrush current in motor performance specification sheets (“locked-rotor 

current”) and as a coded letter on the nameplate. 

Manufacturer's 

Name 

The name of the motor’s manufacturer must appear on the nameplate. 

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EERE-2007-BT-STD-0007 COMMENT 17
 

 

In addition to the above information, manufacturers of small electric motors may 

voluntarily include information, such as service factor, efficiency, and power factor. 

Manufacturers usually provide such information because it facilitates purchasing and allows 

maintenance personnel to quickly identify an appropriate replacement motor. 

Table 3.2.7. Optional Small Electric Motor Nameplate Information 

Service Factor This measure indicates how much overload a motor can withstand when 

operating normally within the correct voltage tolerances. The standard 

service factor for a 1 horsepower open motor with a rated full load speed of 

1800 revolutions per minute is 1.15. This means that such a motor could 

provide 1.15 horsepower when operated at its service factor. Small electric 

motors are also designed with higher service factors, such as 1.25 or 1.35. 

Full-Load 

Efficiency 

Full-load efficiency is a measure of the motor’s ability to effectively convert 

electrical power into mechanical power and is expressed as a percentage. 

Power Factor This value is represented by the ratio of the motor load in watts divided by 

voltage-amperes at full load. Power factor varies directly with loading, 

generally increasing with load percentage. 

3.2.3 Manufacturers and Market Share 

Five large manufacturers dominate the small electric motor market for this rulemaking: 

• A.O. Smith Electrical Products Company; 

• Baldor Electric Company; 

• Emerson Motor Technologies; 

• Regal-Beloit Corporation; and 

• WEG Electric Motors Corporation. 

The five manufacturers identified above are all major manufacturers with diverse 

portfolios of product offerings, including small electric motors covered under EPCA. Over the 

past decade, there has been a consolidation of motor manufacturing in the United States and, in 

part, the limited number of small electric motor manufacturers is a result of mergers and 

acquisitions occurring over the last few decades. 

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

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

shipments of small electric motors from these five companies constitute over 50 percent of the 

total U.S. market. 

3.2.3.1 Small Businesses 

The small electric motor market is predominantly supplied by large manufacturers, DOE 

examined those small businesses that manufacture small electric motors during the NOPR stage 

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

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EERE-2007-BT-STD-0007 COMMENT 17
 

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 small 

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

the North American Industry Classification System (NAICS). For small electric motors, the size 

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

DOE found that there are no small businesses that manufacture the type of small electric 

motors covered by this rulemaking. While many small businesses exist that produce small 

electric motors, none of these companies produce motors that meet the criteria to be covered by 

this rulemaking. For example, Sterling Electric manufactures a line of small electric motors that 

meet most criteria (open enclosure, general purpose, etc.), but the motors are not two-digit frame 

series, and therefore are not covered by this rulemaking. 

3.2.4 Application and Performance of Existing Equipment 

The general purpose CSIR, CSCR and polyphase small electric motors covered are used 

in a fairly wide range of applications, including the following: 

• blowers 

• compressors 

• commercial clothes dryers 

• conveyors 

• fans 

• food processing equipment 

• heating, ventilation, and air-conditioning equipment 

• medical equipment 

• packing machinery 

• pumps 

3.2.5 Trade Associations 

DOE is aware of two trade associations for manufacturers of small electric motors: the 

National Electrical Manufacturers Association (NEMA) and the Motors and Motion Association 

(SMMA).m All five major manufacturers discussed above are members of NEMA and SMMA. 

3.2.5.1 National Electrical Manufacturers Association 

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

four groups that provide different functions for its members: 

• NEMA/TEC, Technical Services Department 

• NEMA/GOV, Government Relations Department 

m For more information about The Motors and Motion Association, visit www.smma.org. Likewise, for information 

about NEMA, visit www.nema.org. 

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EERE-2007-BT-STD-0007 COMMENT 17
 

• NEMA/PAC, Political Action Committee 

• NEMA/BIS, Business Information Services 

Through these groups, NEMA helps to standardize the performance, size, and 

functionality of electrical equipment for its members. An example of NEMA’s role in 

standardization is the NEMA Standard MG1 document,n which is a reference document for 

motor and generator manufacturers and users. NEMA Standard MG1 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. NEMA Standard MG1 is a complete industry reference document 

for standardizing the motors offered in the market.2 

In addition to MG1, NEMA established and promoted a high efficiency standard for 

electric motors through the “NEMA Premium®” label for qualifying motors.o NEMA motor 

manufacturers attach this label to motors that are built to prescribed high efficiency standards. 

These standards exceed the minimum requirements established by EPACT 92, which requires 

general-purpose motors from 1 to 200 horsepower to meet certain minimum efficiency levels. 

See section 3.2.7 for more discussion on these minimum efficiency levels. 

3.2.5.2 The Motors and Motion Association 

SMMA is a trade association focused on electric motors and motion control products. 

SMMA has over 120 members, including manufacturers, suppliers, users, consultants, 

universities, and distributors. SMMA supports its members through programs and services, 

including annual conferences, in-house educational courses from the SMMA Motor and Motion 

College, the publication of industry market trend data, and small electric motor research 

activity.p 

In 1995, SMMA founded the Electric Motor Education and Research Foundation 

(EMERF), whose mission is “to advance and promote the electric motor industry through 

education, pre-competition research, and facilitation of technology transfer within the industry 

and in cooperation with academic, private research and governmental organizations.”3 EMERF 

is important because it is a segment of the SMMA that promotes energy efficiency through 

teaching and providing information on new motor technologies. 

3.2.6 Regulatory Programs 

Under EPCA, as amended by EPACT 1992, each general-purpose three-phase induction 

motor, which is covered by definition and manufactured for distribution in commerce in the 

United States, is required to have a nominal full load efficiency that is not less than the efficiency 

in 10 CFR 431.25. The output ratings of these electric motors are from 1 to 200 horsepower and, 

as such, there appears to be some overlap with the 1 to 3 horsepower small electric motors 

n

 NEMA’s MG1 document can be purchased online at www.nema.org/stds/MG1.cfm. o

 NEMA’s Premium® Motors program can be reviewed at www.nema.org/gov/energy/efficiency/premium. p

 Information about the SMMA Motor and Motion College can be obtained at 

http://www.smma.org/MotorMotionCollege.htm. 

3-14 

EERE-2007-BT-STD-0007 COMMENT 17
 

 

covered in this rulemaking. However, the electric motors covered under the EPACT 1992 

amendment are defined as “T-frame” and constructed according to NEMA standard three-digit 

frame series dimensions for mounting and interchangeability. The small electric motors covered 

in the analysis are, by definition, built in a “two-digit frame number series” for which the 

dimensions for mounting and interchangeability are fundamentally different from “T-frame” 

motors. This one element in the definition of “small electric motor,” distinctly separates the 

identity of “small electric motors” from “electric motors” covered by EPCA. Therefore, DOE 

concludes that there is no overlap between these covered electric motors. 

In general, EPCA, as amended by EISA 2007, covers certain categories of motors other 

than those already covered under the EPACT 1992 amendment and for some, it extends the 

upper limit of the output power range from 201 horsepower to 500 horsepower. For all of these 

motors, EISA 2007 prescribes nominal full load efficiency levels as defined in NEMA MG1– 

2006, Table 12–11. Further, for those electric motors already covered under the EPACT 1992 

amendment, EISA 2007 prescribes nominal full load efficiency levels as defined in NEMA 

MG1–2006, Table 12–12. EISA 2007 does not however, address efficiency levels for small 

electric motors that are the subject of this analysis. 

Nevertheless, EPACT 1992 amended EPCA to cover “small electric motors” and directed 

the Secretary of Energy to make a determination as to whether energy conservation standards for 

covered small electric motors would be technologically feasible, economically justified, and 

would result in significant energy savings. 42 U.S.C. 6317(b). Based on its analysis of available 

information, DOE determined that energy conservation standards for the defined small electric 

motors appear to meet these criteria. 71 FR 38807. As a result, DOE has undertaken a 

rulemaking process for small electric motors as directed by EPCA. 

3.2.7 Non-Regulatory Programs 

DOE reviewed voluntary programs that promote energy efficient electric motors in the 

United States, including the DOE Motor Challenge program, NEMA Premium energy efficient 

motors program, and Consortium for Energy Efficiency (CEE) Premium Efficiency motors 

program. 

3.2.7.1 Department of Energy Motor Challenge Program 

In general, motor-driven equipment accounts for more than 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 

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EERE-2007-BT-STD-0007 COMMENT 17
 

 

 

 

projections of much larger and longer-term national energy savings opportunities of over 100 

billion kilowatt-hours per year by the year 2010.q 

The Motor Challenge program encompasses three-phase 60 Hertz motors rated 1 

horsepower and above. Its elements and offerings include: the 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 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 

software support for plant staff and industrial service providers working on industrial energy 

savings projects.r 

MotorMaster+ is an energy-efficient motor selection and management tool, which 

includes a database of over 20,000 electric motors. It features motor inventory management 

tools, maintenance log tracking, efficiency analysis, savings evaluation, energy accounting, and 

environmental reporting capabilities.s Recently, MotorMaster+ has been expanded to include an 

International Electrotechnical Commission 50 Hertz database that contains 0.03, 0.04, 0.06, 0.09, 

0.12, 0.15, 0.18, 0.25, 0.3, 0.37, 0.45,0.55, and 0.75 kW motors–the equivalent of polyphase 

small electric motors, but rated in kilowatts. Many manufacturers have supplied data to 

MotorMaster+ that was outside the scope of small electric motors, nevertheless, the database 

could be expanded in the future to include small electric motors. 

3.2.7.2 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 MG1–1987 (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.4 t 

q

 For more information about DOE “BestPractices,” under the DOE Industrial Technologies Program, and Motor 

Challenge, visit http://www1.eere.energy.gov/industry/bestpractices/index.html. 

r

 For more information about the EERE Information Center, visit https://www.eecbg.energy.gov/informationcenter/. s

 For more information about MotorMaster+, visit www1.eere.energy.gov/industry/bestpractices/software.html#mm.
 t

 For more information about the NEMA Premium Efficiency Motor Program, visit 

http://www.nema.org/gov/energy/efficiency/premium/. 

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EERE-2007-BT-STD-0007 COMMENT 17
 

 

 

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. 5 Such electric motors are typically used in 

industrial applications operating more than 2000 hours per year. The NEMA Premium 

Efficiency Motor Program does not cover small electric motors as they are defined in EPCA. 

Nevertheless, some motor manufacturers offer polyphase, capacitor-start induction-run, and 

capacitor-start capacitor-run small electric motors at premium efficiency levels. As a result of 

the Energy Independence and Security Act (EISA) of 2007, these efficiency levels will become 

mandatory on December 19, 2010. 

3.2.7.3 Consortium for Energy Efficiency 

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 products, 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 

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 higher than EPACT 1992 requirements.6 

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. DOE reviewed 

the report and the CEE program descriptions it contains, but did not find any incentives that 

explicitly cover small electric motors. It appears that the programs cover commercial and 

industrial motors rated from 1 to 500 horsepower, although there is some potential for crossover 

to small polyphase electric motors in the 1 to 3 horsepower range.u

 There are a number of 

different programs broken down by region. For more information on these programs, download 

the report from CEE.7 

u

 For more information about CEE motor and motor systems programs, visit http://www.cee1.org/ind/mot-sys/mtrms-main.php3. 

3-17 

EERE-2007-BT-STD-0007 COMMENT 17
3.3 TECHNOLOGY ASSESSMENT 

The small electric motors covered in this rulemaking 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 current flow in the rotor. This current 

flow creates an opposing magnetic field in the rotor, which creates rotational forces. Because of 

the orientation of these fields, the rotor field follows the stator field. The rotor is connected to a 

shaft that also rotates and provides the mechanical energy output. 

The purpose of the technology assessment is to develop a preliminary list of technology 

options that could improve the efficiency of small electric motors. In the small electric motors 

covered in this rulemaking, energy efficiency losses are grouped into four main categories: I

2

R 

losses, core losses, friction and windage losses, and stray load losses. The technology options 

considered in this section are categorized by these four categories of losses. 

3.3.1 Technology Options for I2R Losses 

I

2

R losses stem from the current flow through the copper windings in the stator and 

conductor bars in the rotor. These conductor bars are usually made of aluminum, but some high 

efficiency motors that use copper are now available. I

2

R losses are reduced by decreasing 

resistance to current flow in the electrical components of a motor. These losses are manifested 

as waste heat, which can shorten the service life of a motor. 

There are several ways that manufacturers work to minimize the losses created by 

resistance to current flow. Most of these efforts use the same principle of decreasing resistance, 

but there are different ways and areas of the motor where this can be done effectively. The 

resistance of a conductor is a function of both the resistivity and the geometric dimensions (e.g., 

the cross-sectional area) of the material through which current flows. Resistivity is a physical 

characteristic that remains relatively constant for a given material, so changing the material type 

or manipulating the material’s geometry (e.g., copper wire diameter) are two approaches 

manufacturers employ to lower resistance. For single-phase CSCR motors, design engineers can 

also change the microfarad rating of the run-capacitor in combination with changing the copper 

wiring. The second capacitor reduces the current required to run the motor and in turn reduces 

the I2

R losses. 

Rotor conductor bars are areas where current flows. These bars are usually made of 

aluminum in small electric motors. One method of increasing the efficiency of the motor is to 

substitute copper bars for aluminum. Aluminum has a higher electrical resistivity (2.65 x 10-8 

ohm-m) than copper (1.68 x 10-8 ohm-m). Copper is approximately 58 percent more conductive 

than aluminum, and changing from aluminum bars to copper would reduce associated I2

R losses 

in the rotor. 

Manipulation of the rotor’s geometrical design is another approach to reduce I2

R losses in 

the rotor. For the motors covered in this rulemaking, the rotors are called “squirrel-cage rotors” 

because without the core steel stack, the rotor conductor bars and end rings resemble the exercise 

wheels that domesticated squirrels would run in. The conductor bars of the rotor cage are not 

3-18 

EERE-2007-BT-STD-0007 COMMENT 17
 

 

 

 

 

straight from one end ring to another; instead, they are twisted or slightly skewed. 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, overly 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 (i.e., aluminum or copper) through which current is flowing. By 

increasing the cross-sectional area, resistance will decrease and current flow will increase. 

Another area of the rotor that manufacturers may alter to increase efficiency is the end 

ring. Current also flows through this area of the rotor. Increasing the size of the end ring can 

help decrease resistance and alleviate some of the I2

R losses. 

When rotor resistance is lowered, rotor bar current is increased, resulting in an increase in 

the electromagnetic forces. Depending on the magnitude of the gain in efficiency, this may 

actually have some adverse impacts on the electric motor. Also, when manufacturers increase 

the diameter of the rotor bars to lower rotor resistance, they remove steel from the lamination 

and thus the magnetic circuit. The reduction in steel will drive up magnetic saturation, which 

could counteract the efficiency gains. Furthermore, changing the conductor bar shape could 

induce harmonic content to the motor’s operation. Odd harmonics, particularly the third 

harmonic, can create cusps in the speed-torque characteristics, which in turn disrupt motor 

acceleration. Larger rotor bars may also cause manufacturers to build new lamination tooling 

and add stack length because of magnetic saturation. 

I

2

R losses are also prevalent in the stator. There are several design alterations that 

manufacturers may employ to decrease these losses. Most of the design options involve 

increasing the amount of copper winding in the slots. Manufacturers can accomplish this by 

using different gauges of copper wire, changing the slot sizes, and adjusting the length to 

diameter ratios. The use of larger (i.e., numerically lower) wire gauges increases the efficiency 

of the motor because the larger cross-sectional area decreases the overall motor resistance. 

Increasing the stator’s slot size may also allow manufacturers to increase the slot fill. Slot fill is 

the amount of copper wire inserted into a cross-sectional area relative to the total slot crosssectional area. Depending on the number of poles in the motor, certain length-to-diameter ratios 

are better suited to balance the magnetic circuit. 

Another way for manufacturers to reduce I2R losses is to reduce the air gap between the 

stator and rotor. A smaller air gap will decrease the magnetomotive force drop, which occurs 

across the air gap. The motor will then require less current to drive the load and thereby reduce 

I

2

R losses. The problem with this option is that smaller air gaps mean there are tighter tolerances 

on specifications when building a motor, which at some point become technically infeasible to 

manufacture. Based on discussion with manufacturers and small electric motor design engineers, 

DOE believes that the smallest air gap possible, without manufacturing problems, is 0.0125 inch. 

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EERE-2007-BT-STD-0007 COMMENT 17
 

 

 

 

 

 

 

3.3.2 Technology Options for Core Losses 

Core losses are those losses created in the 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 physical currents that are induced in the steel laminations 

by the magnetic flux of the windings. 

Manufacturers have several techniques to help reduce the effects of hysteresis and eddy 

current losses in their motors. One of the first approaches is simply adding additional steel to the 

rotor and stator (i.e., increasing the “stack” length). This is one of the least costly and least 

invasive changes a manufacturer can use to increase motor efficiency. The extra steel 

laminations and increased stack height decrease flux density. This reduces hysteresis losses, but 

also changes motor performance. Adding stack length increases motor impedance, which is then 

reduced by removing turns of wire in the stator. Monitored starting torque is also important 

because an increased stack may reduce torque, potentially rendering the motor unable to start in 

certain applications. Adding stack to the motor means the motor is also getting longer 

physically, therefore geometrical constraints can become an issue as well. 

Another technique for reducing steel losses is using a higher quality, more efficient grainoriented 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 small electric motors manufactured today. 

There are three types of steel that DOE considers “conventional:” cold-rolled magnetic 

laminations (CRML), fully processed non-oriented electrical steel, and semi-processed nonoriented electrical steel. Each steel type is sold in a range of grades. Generally, 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 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 do not require annealing after being punched and assembled, and are 

available in a range of steel grades from M56 through M15.v

 Semi-processed electrical steels are 

designed for annealing after punching and assembly, but they have more limited availability.8 

The exotic steels generally are not manufactured for specific use in small electric motors. 

These steels include amorphous steel, vanadium permendur, and other alloyed steels containing a 

high percentage of boron or cobalt. 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. 

v

 Lower “M” grades of steel denote lower losses, thus M15 has fewer losses per pound of steel than M56. 

3-20 

EERE-2007-BT-STD-0007 COMMENT 17
 

 

Another method manufacturers use to reduce core losses is to use thinner laminations of 

steel. Using thinner laminations decreases the cross-sectional area through which the eddy 

currents are produced, reducing the magnitude of the eddy currents. This reduction in losses will 

reduce heat generation in the steel and improve efficiency. However, this design change does 

come with a penalty. As laminations become thinner, more laminations are needed for the same 

stack height, requiring more punching and assembly time. 

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 do additional annealing to the steel because they are 

adding another step to the manufacturing process, which increases production time. The 

necessary annealing equipment also requires a large capital investment. 

Table 3.3.1 presents the core steels used in manufacturing small 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. 

3-21 

EERE-2007-BT-STD-0007 COMMENT 17
 

 

Table 3.3.1. Core Steel Grades, Thicknesses, and Associated Losses 

Steel 

Grade 

Nominal 

Thickness 

(inches) 

Theoretical Core Loss at 

60 Hz 

(Watts per Pound at 

Magnetic Flux Density) 

Remarks 

24 M56* 0.025 4.30 Watts/lb at 1.5 T9 Cold-rolled magnetic laminations (semiprocessed) 

26 M47 0.019 2.80 Watts/lb at 1.5 T8 Non-oriented electrical steel (fully processed) 

24 M36 0.025 2.35 Watts/lb at 1.5 T8 Non-oriented electrical steel (fully processed) 

24 M19* 0.025 2.00 Watts/lb at 1.5 T8 Non-oriented electrical steel (fully processed) 

29 M15* 0.014 1.45 Watts/lb at 1.5 T8 Non-oriented electrical steel (fully processed) 

Hiperco 

50* 0.006 1.00 Watts/lb at 1.5 T10 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," named in honor 

of inventor, scientist, and electrical engineer Nikola Tesla. 

3.3.2.1 Plastic Bonded Iron Powder 

Recently, DOE became aware of a new technology that Lund University researchers in 

Sweden developed 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. 

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.11 

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EERE-2007-BT-STD-0007 COMMENT 17
 

3.3.3 Technology Options for Friction and Windage Losses 

Bearing friction and an imperfect cooling fan system create what is called “friction and 

windage losses” in AC induction motors. These losses also add heat to the motor’s system and 

decrease 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 current fan can help reduce heat and losses. Baffles 

help redirect airflow through the motor, creating better circulation and a cooler motor overall. 

With a well-designed cooling system, the motor should run more efficiently. However, some 

manufacturers choose to use one cooling system for a range of horsepower ratings. This means 

that the same cooling system may exceed spatial constraints for certain smaller motors, resulting 

in more losses than are necessary to cool the motor. 

3.3.4 Technology Options for Stray Load Losses 

Any losses that are otherwise unaccounted for and not attributed to I2

R losses, steel 

losses, or frictional and windage losses are considered stray-load losses. DOE is not aware of 

any specific techniques manufacturers use to reduce stray-load losses. General process changes 

to the manufacturing of rotors and stators could somewhat reduce these losses. 

3.3.5 Summary of the Technology Options Under Consideration 

Table 3.3.2 summarizes the technology options discussed in this technology assessment, 

and those that DOE will now 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 chapter 5) as a means of improving the efficiency of small electric motors. 

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Table 3.3.2. Summary of Technology Options for Improving Efficiency 

Type of Loss to Reduce Technology Option Applied 

I

2

R Losses 

Use copper die-cast rotor cage 

Remove skew on conductor cage 

Increase cross-sectional area of rotor conductor bars 

Increase end ring size 

Changing gauges of copper wire in stator 

Manipulate stator slot size 

Decrease the radial air gap 

Change run-capacitor rating 

Core Losses 

Improve grades of electrical steel 

Use thinner steel laminations 

Anneal steel laminations 

Add stack height (i.e., length, add electrical steel 

laminations) 

Use high-efficiency lamination materials 

Use plastic bonded iron powder 

Friction and Windage Losses Use better bearings and lubricant 

Install a more efficient cooling system 

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REFERENCES
 

1 U.S. Small Business Administration. Small Business Size Standards Matched to North 

American Industry Classification System. 2006. (Last accessed September 22, 2009.) 

<http://www.sba.gov/idc/groups/public/documents/sba_homepage/serv_sstd_tablepdf.pdf> The 

September 22, 2008, material from this website is available in Docket # EERE–2007–BT–STD– 

0007. 

2 National Electric Manufacturers Association. (Last accessed September 22, 2009.) 

<http://www.nema.org/about/upload/NEMACorpBrochure05.pdf > The September 22, 2009, 

material from this website is available in Docket #EERE–2007–BT–STD–0007. 

3

 Small Motor and Motion Association. 2008. (Last accessed September 22, 2009.) 

<http://www.smma.org/> The September 22, 2009, material from this website is available in 

Docket #EERE–2007–BT–STD–0007. 

4

 National Electric Manufacturers Association. NEMA Premium Efficiency Electric Motors 

Program. 2008. (Last accessed April 21, 2008.) 

<http://www.nema.org/gov/energy/efficiency/premium/upload/nemaprem1p.doc> The April 21, 

2008, material from this website is available in Docket #EERE–2007–BT–STD–0007. 

5

 National Electric Manufacturers Association. NEMA Premium Product Scope and Nominal 

Efficiency Levels. June 3, 2009. (Last accessed September 22, 2009.) 

<http://www.nema.org/stds/complimentary-docs/upload/MG1premium.pdf> The September 22, 

2009, material from this website is available in Docket #EERE–2007–BT–STD–0007. 

6 Consortium for Energy Efficiency. Industrial Programs Premium-Efficiency Motors. 2008. 

(Last accessed September 22, 2009.) < http://www.cee1.org/ind/motrs/timeline_poster.pdf> The 

September 22, 2009, material from this website is available in Docket #EERE–2007–BT–STD– 

0007. 

7 Consortium for Energy Efficiency. Energy-Efficiency Incentive Programs, Premium-Efficiency 

Motors and Adjustable Speed Drives in the U.S. and Canada. May 2007. (Last accessed 

September 22, 2009.) <http://www.motorsmatter.org/tools/programs2007.pdf> The September 

22, 2009, material from this website is available in Docket #EERE-2007-BT-STD-0007. 

8 AK Steel Corporation. Product Data Bulletin: Selection of Electrical Steels for Magnetic 

Cores. July 2007. West Chester, Ohio. 

9

 National Materials. National Materials Company: Materials. (Last accessed April 21, 2008.) 

<http://nmlp.hypermart.net/Material/index.html> The April 21, 2008, material from this website 

is available in Docket #EERE–2007–BT–STD–0007. 

10 Carpenter Technology Corporation. Core Loss vs. Induction for 0.006” thick strip. 2009. 

(Last accessed September 22, 2009.) 

<http://cartech.ides.com/datasheet.aspx?i=101&e=200&c=TechArt>. The September 22, 2009, 

material from this website is available in Docket #EERE-2007-BT-STD-0007. 

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11 Horrdin, H., Olsson, E. Technology Shifts in Power Electronics and Electric Motors for 

Hybrid Electric Vehicles: A Study of Silicon Carbide and Iron Powder Materials. 2007. 

Chalmers University of Technology. Göteborg, Sweden. 

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