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 General­Purpose Alternating­Current Motor.............................................. 3

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

3.2.1.3 Frame Sizes and Metric Equivalents........................................................... 7

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

3.2.2 Small Electric Motor Nameplates and Terminology .............................................. 8

3.2.3 Proposed Equipment Classes................................................................................ 11

3.2.3.1 Representative Units................................................................................. 13

3.2.3.2 Scaling Findings from Representative Units ............................................ 20

3.2.4 Shipments.............................................................................................................. 21

3.2.5 Manufacturers and Market Share.......................................................................... 24

3.2.5.1 Small Businesses....................................................................................... 24

3.2.6 Application and Performance of Existing Equipment .......................................... 25

3.2.7 Trade Associations................................................................................................ 25

3.2.7.1 National Electrical Manufacturers Association ........................................ 25

3.2.7.2 The Motors and Motion Association ........................................................ 26

3.2.8 Regulatory Programs ............................................................................................ 26

3.2.9 Non­Regulatory Programs.................................................................................... 27

3.2.9.1 Department of Energy Motor Challenge Program.................................... 27

3.2.9.2 National Electrical Manufacturers Association Premium Efficiency Motor

Program..................................................................................................... 28

3.2.9.3 Consortium for Energy Efficiency............................................................ 29

3.3 TECHNOLOGY ASSESSMENT..................................................................................... 29

2 3.3.1 Technology Options for I R Losses...................................................................... 30

3.3.2 Technology Options for Core Losses ................................................................... 31

3.3.2.1 Plastic Bonded Iron Powder...................................................................... 33

3.3.2.2 Permanent Magnet Electric Motor............................................................ 34

3.3.3 Technology Options for Friction and Windage Losses ........................................ 34

3.3.4 Technology Options for Stray Load Losses.......................................................... 34

3.3.5 Summary of the Technology Options Under Consideration................................. 35

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 Locked­Rotor Torque, Ounce­Feet*.......................................................... 5

Table 3.2.3. Required Small Electric Motor Nameplate Information........................................... 10

Table 3.2.4. Optional Small Electric Motor Nameplate Information ........................................... 11

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EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.5. Example of Equipment Classes for Capacitor­Start, Induction­Run Small Electric

Motors........................................................................................................................................... 13

Table 3.2.7. Representative Units Selected for the Preliminary Notice of Proposed Rulemaking20

Table 3.2.9. National Electrical Manufacturers Association Polyphase Small Electric Motor

Table 3.2.11. National Electrical Manufacturers Association Capacitor­Start, Induction­Run

Table 3.2.12. Estimated Capacitor­Start, Induction­Run Small Electric Motor National

Table 3.2.13. Estimated Capacitor­Start, Capacitor­Run Small Electric Motor National

Table 3.2.6. Representative Units Selected for the Determination Analysis................................ 14

Table 3.2.8. Scaling from Representative Motors to all Equipment Classes................................ 21

Shipment Data, 2000..................................................................................................................... 22

Table 3.2.10. Estimated Polyphase Small Electric Motor National Shipments, 2007.................. 22

Small Electric Motor Shipment Data, 2000.................................................................................. 23

Shipments, 2007............................................................................................................................ 23

Shipments, 2007............................................................................................................................ 24

Table 3.3.1. Core Steel Grades, Thicknesses, and Associated Losses.......................................... 33

Table 3.3.2. Summary of Technology Options for Improving Efficiency.................................... 35

LIST OF FIGURES

Figure 3.2.1. Polyphase Small Electric Motor Shipments Broken Down by Pole Configuration 14

Figure 3.2.5. Capacitor­Start, Induction­Run Small Electric Motor Shipments Broken Down by

Figure 3.2.6. Capacitor­Start, Induction­Run Small Electric Motor Shipments Broken Down by

Figure 3.2.7. Models of Capacitor­Start, Induction­Run Small Electric Motors Broken Down by

Figure 3.2.8. Efficiency as a Function of Horsepower for Capacitor­Start, Induction­Run Small

Figure 3.2.9. Capacitor­Start, Capacitor­Run Small Electric Motor Shipments Broken Down by

Figure 3.2.10. Capacitor­Start, Capacitor­Run Small Electric Motor Shipments Broken Down by

Figure 3.2.11. Models of Capacitor­Start, Capacitor­Run Small Electric Motors Broken Down by

Figure 3.2.2. Polyphase Small Electric Motor Shipments Broken Down by Horsepower........... 15

Figure 3.2.3. Models of Polyphase Small Electric Motors Broken Down by Horsepower.......... 15

Figure 3.2.4. Efficiency as Function of Horsepower for Polyphase Small Electric Motors......... 16

Pole Configuration........................................................................................................................ 16

Horsepower................................................................................................................................... 17

Horsepower................................................................................................................................... 17

Electric Motors.............................................................................................................................. 18

Pole Configurations ...................................................................................................................... 18

Horsepower................................................................................................................................... 19

Horsepower................................................................................................................................... 19

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EERE-2007-BT-STD-0007 COMMENT 07.2
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 apply 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 non­regulatory efficiency improvement programs, equipment classes, and trends

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

preliminary 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 equipment

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 non­regulatory 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 MG 1 for

Motors and Generators. NEMA drafted and maintains the MG 1 document, most recently

revised in November 2007 as MG 1–2006 Revision 1. MG 1 assists users in the correct selection

and application of electric motors and generators. MG 1 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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EERE-2007-BT-STD-0007 COMMENT 07.2
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

b defines the term “small electric motor” to mean “a NEMA general­purpose alternating current

single­speed induction motor,c built in a two­digit frame number seriesd in accordance with

NEMA Standards Publication MG 1–1987.” (42 U.S.C. 6311(13)(G)) Such motors include

single­phase, capacitor­start induction­run (CSIR), capacitor­start capacitor­run (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 air­conditioning 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 MG 1–1987, such as general purpose and two­digit

frame size. Thus, EPCA’s definition of a small electric motor is tied to NEMA MG1–1987

terminology and performance requirements established for (1) general­purpose alternatingcurrent motors, (2) various categories of induction motors, and (3) the definition of two­digit

b “General­purpose alternating current” is a term that NEMA uses for alternating­current motors that are not

designed with a specific application in mind.

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 “two­digit frame number series” and “frame size” 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 size 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 48­frame 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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EERE-2007-BT-STD-0007 COMMENT 07.2
frame size. In the following subsections, DOE addresses elements of the definition of “small

electric motor” that need clarification.

3.2.1.1 General­Purpose Alternating­Current Motor

Two elements in the statutory definition of small electric motors, which derive from

NEMA MG1–1987, are “general­purpose” and “alternating­current.” Paragraph MG1–1.05 sets

forth the definition:

A general­purpose alternating­current 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 MG 1­12.47, and (4) Class A

insulation system with a temperature rise as specified in MG 1­12.42 for small electric

motors or Class B insulation system with a temperature rise as specified in MG 1­12.43

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 MG 1­1987 to define a general­purpose 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 general­purpose alternating­current motors, which are rated for continuous

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

consider only those motors rated for continuous duty.

MG 1–1987 defines general­purpose alternating­current motors as having a service factor

in accordance with MG 1–12.47. 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 1­horsepower motor with a 1.25 service factor can operate at 1.25

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

factor for general­purpose alternating­current motors be in accordance with MG 1–12.47. (See

e NEMA MG1–1987 defines each of the following motors, in part, as “an open machine”: drip­proof, splash­proof,

semi­guarded, guarded, dripproof guarded, open externally ventilated, open pipe­ventilated, and weather­protected

(Type I and Type II).

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EERE-2007-BT-STD-0007 COMMENT 07.2
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 1,200 900

1/20 1.4 1.4 1.4 1.4

1/12 1.4 1.4 1.4 1.4

1/8 1.4 1.4 1.4 1.4

1/6 1.35 1.35 1.35 1.35

1/4 1.35 1.35 1.35 1.35

1/3 1.35 1.35 1.35 1.35

1/2 1.25 1.25 1.25 ­

3/4 1.25 1.25 ­ ­

1 1.25 ­ ­ ­

The MG 1–1987 definition of “general­purpose alternating­current motor,” in part

identifies a 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. Although small electric motors can be manufactured with

Class B, Class F, or Class H insulation systems, DOE proposes to cover only those small electric

motors with Class A insulation systems.

Lastly, MG1–1987 requires that a general­purpose alternating­current 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 “general­purpose 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 general­purpose 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 minimum locked­rotor torque (see NEMA MG1–

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EERE-2007-BT-STD-0007 COMMENT 07.2
12.32.2). Such requirements limit the scope of covered small electric motors. For example, the

breakdown torques of many shaded­pole and permanent­split capacitor motors do not fall within

the breakdown torque ranges of MG1 Table 10–5. Section 12.32.2 of MG 1­1987 requires that

the locked­rotor torque shall be no less than the values presented in Table 3.2.2.

Table 3.2.2. Minimum Locked­Rotor Torque, Ounce­Feet*

Horsepower 60­Hz Synchronous Speed

(RPM)

50­Hz Synchronous Speed

(RPM)

3,600

3,450

1,800

1,725

1,200

1,140

3,000

2,850

1,500

1,425

1,000

950

1/8 ­ 24 32 ­ 29 39

1/6 15** 33 43 18 39 51

1/4 21 46 59 25 55 70

1/3 26 57 73 31 69 88

1/2 37 85 100 44 102 120

3/4 50 119 ­ 60 143 ­

1 61 ­ ­ 73 ­ ­

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

these values may be expected.

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

synchronous speed. For this particular combination (i.e., 1/6 horsepower with a speed between 3,450 and 3,600

rpm), manufacturers must ensure that the motor has at least 15 ounce­feet of locked rotor torque to meet this

requirement of NEMA MG1–1987.

Of the motors satisfying the frame­size requirement of the EPCA definition of “small

electric motor” and “built in a two­digit frame number series in accordance with NEMA

Standards Publication MG 1–1987,” only a subset incorporates the other performance

requirements of a general­purpose motor under NEMA MG 1–1987, paragraph 1.05. Among

single­phase motors with a two­digit frame size, DOE found that only capacitor­start motors–

including capacitor­start induction­run, and capacitor­start capacitor­run motors–can meet the

torque requirements for NEMA general­purpose motors. Among three­phase small electric

motors, only non­servo motors can meet the NEMA performance requirements for generalpurpose motors. Hence, DOE’s analysis only covers the capacitor­start categories of singlephase motors and three­phase small electric motors.

3.2.1.2 Categories of Induction Motors

The statutory definition also requires that a small electric motor be an “alternating current

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

categories of alternating current single­speed induction motors: split­phase,f shaded­pole,g

f A split­phase motor is a single­phase 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

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EERE-2007-BT-STD-0007 COMMENT 07.2
capacitor­start (both CSIRh and CSCRi

), permanent­split capacitor (PSC),jand polyphase.k In

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

its preliminary conclusion that the CSIR, CSCR, and polyphase motors are the only three

categories which are covered under EPCA.

DOE eliminated split­phase, PSC, and shaded­pole motors from consideration because

they are not designed as and do not meet the performance requirements of general­purpose

motors. Split­phase motors are designed for specific purposes and applications, and generally

for applications that are short­time rated. Also, split­phase motors do not meet the breakdown

torque requirements or the locked­rotor torque requirements while simultaneously maintaining

the locked­rotor current requirements that have been established in NEMA for general­purpose

motors. In some cases, split­phase 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

general­purpose motors. Shaded­pole 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

requirements. These shaded­pole 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 shadedpole motors do not meet the performance characteristics for NEMA general­purpose motors,

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

NEMA MG1–1.05, they 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 re­examined 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 two­digit

frame sizes, can be rated for continuous­duty applications, and can meet other performance

requirements for general­purpose motors, including the torque requirements under NEMA MG1–

1987, paragraph 12.32. Therefore, DOE will address three categories of small electric motors in

today’s rulemaking: single­phase CSIR, single­phase CSCR, and polyphase.

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

motor to be used without impedance other than that offered by the motor windings themselves. g A shaded­pole motor is a single­phase induction motor provided with an auxiliary short­circuited winding or

windings displaced in magnetic position from the main winding. h A capacitor­start, induction­run motor is a single­phase 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.

A capacitor­start, capacitor­run motor is a single­phase motor with different values of effective capacitance for the

starting and running conditions.

j

A permanent­split capacitor motor is another category of single­phase 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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EERE-2007-BT-STD-0007 COMMENT 07.2
3.2.1.3 Frame Sizes 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.

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 sizes 42, 48, and 56. Two­digit NEMA frames

have standard dimensions and tolerances specified in NEMA Standard MG1­1987

paragraphs11.31 and 11.34, which are necessary for mounting and interchangeability among

general­purpose applications.

NEMA MG1–1987 only assigns standard dimensions to 42, 48, and 56 frame motors.

However, certain other non­standard frame sizes, such as a 66 frame size, are manufactured and

sold. While “66” is a two­digit frame size, it does not appear in NEMA MG1–1987.

Consequently, a 66­frame motor may not be covered under the EPCA definition of “small

electric motor.” Furthermore, DOE believes that non­standard, two­digit frames sizes (i.e., other

than 42, 48, and 56) fall outside the scope of the rulemaking for small electric motors. Such nonstandard frame sizes are likely to be definite­purpose or special­purpose motors that are not used

in general­purpose applications.

DOE is concerned about metric equivalents for the two­digit NEMA frame series, the

uncertainty about cross­references, 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

l horsepower. In contrast, general­purpose 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

kilowatt­rated motors, DOE believes that EPCA covers any motor that is equivalent to or can be

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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l

EERE-2007-BT-STD-0007 COMMENT 07.2
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 kilowatt­equivalent motors can be interchanged with small electric motors. 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 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

kilowatt­rated 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 “general­purpose alternating­current motor” as it appears

in NEMA Standard MG1–1987. It explicitly states that a general­purpose alternating­current

motor incorporates “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 EPCA­directed definition. Therefore, DOE interprets the EPCA definition of a

small electric motor to cover only open construction. This is in contrast to and supersedes

DOE’s initial understanding of covered small electric motors. DOE initially included totally

enclosed motors in the scope of its determination analysis.

DOE considered poly­ and single­phase motors, including non­servo three­phase motors;

capacitor­start, induction­run motors; and capacitor­start, capacitor­run 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. These topics are discussed

in section 3.2.3.

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 MG 1 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. The NFPA 70 and

MG 1 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 full­load current;

• rated frequency;

• number of phases;

• rated full­load speed;

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EERE-2007-BT-STD-0007 COMMENT 07.2
• rated temperature rise or the insulation system class and rated ambient temperature;

• rated horsepower;

• time rating;

• code letter for locked­rotor amperes; and

• thermal protection.

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

70 or NEMA Standard MG 1 require on the motor nameplate.

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EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.3. Required Small Electric Motor Nameplate Information

Frame

Designation

Frame size numbers represent standardized designations for size and

dimensions. For small electric motors, the frame sizes 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 56­frame motor would have a shaft

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

motors, the frame size 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 Full­Load

Amperage

The rated full­load amperage represents the amperage consumption when the

motor reaches full­load 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 full­load amperes. The purpose of the

full­load 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 Single­phase and three­phase motors are available in the United States.

Rated Full­Load

Speed

The rated full­load speed is the approximate rotations per minute of the

motor under full­load conditions at a specified voltage and frequency. The

full­load speed is typically 95% to 99% of the no­load 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 full­load speed and torque rating, as

follows:

Horsepower (hp) = [(Motor Speed) × (Torque (lb­ft))] ÷ 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 “short­time” requirements, ranging

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

for continuous duty.

Locked­Rotor

Code Letter

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

greater than the full­load 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 (“locked­rotor

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 07.2
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 3.2.4. 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.

Full­Load

Efficiency

Full­load 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

voltage­amperes at full load. Power factor varies directly with loading,

generally increasing with load percentage.

3.2.3 Proposed Equipment Classes

In general, DOE identifies a class of covered equipment by the type of energy used,

capacity, and performance­related features that affect consumer utility or efficiency. Different

energy conservation standards may apply to different equipment classes. For this rulemaking,

DOE is proposing to establish 72 equipment classes for small electric motors, based on the

following criteria: motor category, number of poles, and horsepower. As these motor

characteristics change, so does the utility and efficiency of the small electric motor. The lists

below identify these three characteristics. There are three motor categories, three pole

configurations, and eight horsepower ratings that affect energy consumption or efficiency,

resulting in 72 combinations, or equipment classes.

1. Motor Category (i.e., type of energy used, start and run characteristics)

• polyphase

• capacitor­start, induction run (CSIR)

• capacitor­start, capacitor run (CSCR)

2. Number of Poles

• 2

• 4

• 6

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EERE-2007-BT-STD-0007 COMMENT 07.2
3. Horsepower

• 1/4

• 1/3

• 1/2

• 3/4

• 1

• 1 1⁄2

• 2

• 3

First, the motor category depends on the type of energy used and its starting and running

electrical characteristics. While all small electric motors use electricity, some motors operate on

single­phase electricity (which requires certain additional electronics for creating rotational

torque) while others operate on polyphase electricity. Polyphase motors do not need additional

circuitry to create rotational torque because they use the existing phase difference in the multiple

phases of electricity applied to the motor. This difference impacts efficiency, and therefore

becomes a factor around which DOE establishes a separate equipment class for polyphase

motors.

Within single­phase small electric motors, there are characteristics which are important

because they can affect the motor’s utility and potential for improving efficiency. The design

feature of incorporating a run capacitor into the small electric motor affects the efficiency of the

motor, making it more efficient than an induction­run motor that does not incorporate a run

capacitor. This constitute a performance­related feature that affects efficiency. Furthermore,

DOE notes that it is not always possible to replace a CSIR motor with a CSCR motor due to the

run capacitor, which is often mounted in an external housing on the motor. In certain

applications, the run capacitor mounted on the motor will physically prohibit it from replacing a

CSIR motor. This is a design feature that affects utility. For all of these reasons, DOE treats

CSIR and CSCR motors as separate equipment classes.

Next, the number of poles in an electric motor determines the synchronous speed (i.e.,

revolutions per minute). There is an inverse relationship between number of poles and speed,

meaning that an increase in the number of poles equates to a decrease in the speed of the motor

(e.g., going from two to four to six poles, the synchronous speed drops from 3,600 to 1,800 to

1,200 revolutions per minute). The number of poles has a direct impact on the motor’s

performance and efficiency. Consequently, DOE uses the number of poles as a means of

differentiating equipment classes.

Finally, in general, efficiency scales with horsepower, or in other words, a 3­horsepower

motor is usually more efficient than a 1⁄4­horsepower motor. Horsepower is a critical

performance attribute of an electric motor, and since there is a correlation with efficiency, DOE

uses this as a criterion for distinguishing among equipment classes.

Table 3.2.5 presents 24 equipment classes (EC) for CSIR motors, broken down by

number of poles and horsepower/standard kilowatt equivalent ratings. DOE proposes to have the

same table (and EC breakdown) for both CSCR and polyphase motors. Should DOE establish

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EERE-2007-BT-STD-0007 COMMENT 07.2
minimum energy conservation standards for small electric motors, each “EC” cell in the

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

Table 3.2.5. Example of Equipment Classes for Capacitor­Start, Induction­Run Small

Electric Motors

Motor

Horsepower/Standard

Kilowatt Equivalent

Six Poles Four Poles Two Poles

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

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

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

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

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

11⁄2 hp/1.1 kW EC #16 EC #17 EC #18

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

≥ 3 hp/2.2 kW EC #22 EC #23 EC #24

Another important aspect of general­purpose motors covered in this rulemaking is that

each is built in a two­digit frame size, as defined by NEMA MG1–1987. DOE considered, but

then rejected, the idea of differentiating equipment classes by frame size. Frame size is

determined by the shaft height of the motor from the bottom of the base (also called the “D”

dimension) in sixteenths of an inch. For example, a 56­frame motor would have a shaft height of

56/16 of an inch, or 3.5 inches. DOE is not aware of a direct correlation between efficiency and

frame size that would not generally scale with horsepower. Moreover, frame sizes 42, 48, and 56

are manufactured in various horsepower and pole combinations over a range of efficiencies.

Therefore, DOE proposes not to differentiate equipment classes by frame size.

3.2.3.1 Representative Units

DOE based its selection of representative units from the 72 equipment classes of small

electric motors on three factors: (1) the motors that were studied in the determination analysis,

(2) manufacturer’s sales catalogs for this equipment, and (3) the ability to scale from these units

to other units.

In the determination analysis, DOE studied five different motors as the representative

units. Two of the motors were capacitor­start, induction­run and three were polyphase. For the

capacitor­start, induction­run motors, DOE chose two similar models with 56 and 48 frame sizes

to capture different cost­efficiency characteristics associated with those frame sizes. For the

polyphase motors, DOE chose three models, holding frame size constant, but varying the

horsepower for two motors. The five motors studied in the determination analysis are presented

in Table 3.2.6.

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EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.6. Representative Units Selected for the Determination Analysis

Motor Category Model Horsepower Number of Poles Frame Size

CSIR Dayton 4K856 0.50 4 56

CSIR Dayton 6K965 0.50 4 48

Polyphase Dayton 3N641 0.50 4 56

Polyphase Dayton 2N103 0.50 4 56

Polyphase Dayton 3N102 1.0 4 56

DOE also reviewed manufacturer catalogs and created a database of over 700 motors that

represent all the small electric motors manufactured and listed in the catalogs. Although this

database does not provide information on unit sales, it does provide an indication of the more

popular motors from the standpoint of having a greater variety of certain combinations of

horsepower and frame size. Analyzing this data and shipments data (shown in section 3.2.4)

enabled DOE to select popular configurations of small electric motors. Figure 3.2.1 through

Figure 3.2.11 show shipments data for each motor category broken down by pole configuration

and horsepower, as well as the number of models of each motor category broken down by

horsepower. These figures also show efficiency as a function of horsepower for polyphase and

CSIR motors.

Figure 3.2.1. Polyphase Small Electric Motor Shipments Broken Down by Pole

Configuration

6­pole, 9% 2­pole, 23%

4­pole, 68%

3­14

EERE-2007-BT-STD-0007 COMMENT 07.2
Figure 3.2.2. Polyphase Small ElectricHorse ower MotorpShipments Broken Down by Horsepower

1 1/2 HP, 28%

3/4 HP, 28%

1/4 HP, 2%

1/3 HP, 4%

1/2HP, 11%

1 HP, 19%

2­3 HP, 7%

Figures 3.2.1 and 3.2.2 are based on historical shipments data submitted by NEMA in

year 2000 and projected forward to year 2007. (See section 3.2.4 for more detail.) They show

the breakdown of shipments by pole configuration and horsepower. An overwhelming majority

of polyphase motors shipped are four­pole machines and the weighted average horsepower of

shipments is 1 horsepower.

Figure 3.2.3. Models of Polyphase Small Electric Motors Broken Down by Horsepower

0.25 0.33 0.50 0.75 1.00 1.50 2.00 3.00

Horsepower

The data in Figure 3.2.3 is based on DOE’s database of small electric motors compiled

from several manufacturer’s sales catalogs. This figure shows the distribution of models by

horsepower for polyphase motors. The most common horsepower model is 3⁄4 horsepower, but

the data show a skew toward models around 1 horsepower. The data reaffirm the weighted

average of 1 horsepower for polyphase motor shipments, which is why DOE selected 1

horsepower for the polyphase representative unit.

0

10

20

30

40

50

60

70

80

N

u

mb

er o

f

M

otors

3­15

EERE-2007-BT-STD-0007 COMMENT 07.2
)

Figure 3.2.4. Efficiency as Function of Horsepower for Polyphase Small Electric Motors

50

60

70

80

90

E

fficie

n

c

y (%

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Horsepower

Figure 3.2.4 shows the relationship between efficiency and horsepower for polyphase

motors. As the graph shows, motors with a larger horsepower ratings tend to be more energyefficient. This substantiates DOE’s decision discussed earlier in this chapter about

differentiating equipment classes for small electric motors by horsepower rating.

Figure 3.2.5. Capacitor­Start, Induction­Run Small Electric Motor Shipments Broken

Down by Pole Configuration

6­pole, 29% 2­pole, 32%

4­pole, 39%

3­16

EERE-2007-BT-STD-0007 COMMENT 07.2
Figure 3.2.6. Capacitor­Start, Induction­Run Small Electric Motor Shipments Broken

Down by Horsepower

1/4 HP, 18%

1/3 HP, 30%

3/4 HP, 22%

1 HP, 4%

>1 HP, 1%

1/2HP, 25%

Figures 3.2.5 and 3.2.6 are based on historical shipments data submitted by NEMA in

year 2000 and projected forward to year 2007. (See section 3.2.4 for more detail.) They show

the breakdown of shipments by pole configuration and horsepower. The pole configuration

distribution is fairly even among two, four, and six poles, but four poles are most common. The

weighted average horsepower of CSIR motors shipped is 1⁄2 hp.

Figure 3.2.7. Models of Capacitor­Start, Induction­Run Small Electric Motors Broken

Down by Horsepower

0.25 0.33 0.50 0.75 1.00 1.50 2.00 3.00

Horsepower

The data in Figure 3.2.7 are based on DOE’s review of manufacturer catalogs and show

the distribution of models by horsepower for CSIR motors. The most common horsepower

model is 1⁄2 hp and the data trend toward 1⁄2 horsepower as an average model. The data reaffirm

the weighted average of 1⁄2 horsepower for CSIR shipments, which is why DOE selected 1⁄2

horsepower for the CSIR representative unit.

0

10

20

30

40

50

60

70

N

u

mb

er o

f

M

otors

3­17

EERE-2007-BT-STD-0007 COMMENT 07.2
)

Figure 3.2.8. Efficiency as a Function of Horsepower for Capacitor­Start, Induction­Run

Small Electric Motors Efficiency (%

90

80

70

60

50

40

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50

Horsepower

Figure 3.2.8 shows the relationship between efficiency and horsepower for CSIR motors.

In general, small electric motors with a larger horsepower ratings are more efficient.

Figure 3.2.9. Capacitor­Start, Capacitor­Run Small Electric Motor Shipments Broken

Down by Pole Configurations

6­pole, 29% 2­pole, 32%

4­pole, 39%

3­18

EERE-2007-BT-STD-0007 COMMENT 07.2
Figure 3.2.10. Capacitor­Start, Capacitor­Run Small Electric Motor Shipments Broken

Down by Horsepower

1/4 HP, 18%

1/3 HP, 30%

3/4 HP, 22%

1 HP, 4%

>1 HP, 1%

1/2HP, 25%

Figures 3.2.9 and 3.2.10 are based on historical shipments data submitted by NEMA in

year 2000, projected forward to year 2007, and then scaled from CSIR data. (See section 3.2.4

for more detail.) These figures show the breakdown of shipments by pole configuration and

horsepower. The pole configuration distribution is fairly even between two, four, and six poles,

but four poles are most common. The weighted average horsepower of CSCR motors shipped is

1⁄2 horsepower.

Figure 3.2.11. Models of Capacitor­Start, Capacitor­Run Small Electric Motors Broken

Down by Horsepower

0.25 0.33 0.50 0.75 1.00 1.50 2.00 3.00

Horsepower

The weighted average horsepower of CSCR motors shipped was 1⁄2 horsepower, but the

most common horsepower model was clearly 3⁄4 horsepower, shown in Figure 3.2.11. Since

DOE created a 1⁄2­horsepower model for CSIR, it chose 3⁄4 horsepower for CSCR.

DOE did not show efficiency as a function of horsepower for these motors because there

were fewer CSCR models in manufacturer catalogs and only a few of those manufacturers

reported efficiency.

0

2

4

6

8

10

12

14

16

N

u

mber of Motors

3­19

EERE-2007-BT-STD-0007 COMMENT 07.2
DOE also considered the ability to scale from the findings on the representative unit from

the representative equipment class to the adjoining equipment classes, varying both number of

poles and horsepower ratings. DOE selected at least one motor in each of the three categories of

small electric motors (i.e., polyphase, CSIR and CSCR).

Table 3.2.7 presents the four representative units DOE selected for this draft analysis.

The motors are four­pole motors and, in view of DOE’s analysis of manufacturer catalogs, this is

the most common configuration for these horsepower ratings. As in the determination analysis,

DOE selected two CSIR motors with the same horsepower rating and number of poles, but

different frame sizes, to capture any differences in the cost­efficiency relationship among frame

sizes. DOE also selected motors that approximate the middle of the range of covered

horsepowers, partly to minimize any error that might be introduced as the efficiency of these

motors are extrapolated to other horsepower ratings.

Table 3.2.7. Representative Units Selected for the Preliminary Notice of Proposed

Rulemaking

Motor Category Horsepower Number of Poles Frame Size

Polyphase 1.00 4 56

CSIR 0.50 4 56m

CSIR 0.50 4 48

CSCR 0.75 4 56

DOE identified these four as representative units of interest. All four units fit the

requirements of a NEMA general­purpose, single speed, induction motor, rated for continuous

duty, and built with open construction in a two­digit frame size. In the engineering analysis

(chapter 5), DOE provides additional detail on each motor, including input voltage, baseline

efficiency, and other critical performance characteristics.

3.2.3.2 Scaling Findings from Representative Units

DOE believes that it is unrealistic to conduct an analysis of representative units from all

72 equipment classes for small electric motors. Therefore, DOE is selecting a small sample of

motors from popular equipment classes that are approximately in the middle of the range of

covered product (both in terms of number of poles and horsepower rating). DOE will then

extrapolate its findings from each of the three motor categories to other covered small electric

motor equipment classes that were not analyzed, as shown in Table 3.2.8.

m DOE identified these four motors as the representative units to study, and then conducted an engineering analysis

to study the relationship between motor efficiency and manufacturer selling price. DOE found that there was

virtually no difference between the 48 and 56 frame sizes for the 1⁄2­horsepower, four­pole CSIR motors. Therefore,

DOE elected to drop the 56 frame size from its analysis, since frame size tends to scale with horsepower, and at this

rating it would be more common to find a 48 frame than a 56. This issue is discussed in some detail in the

engineering analysis (chapter 5) and the appendix to the engineering chapter (appendix 5A).

3­20

EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.8. Scaling from Representative Motors to all Equipment Classes

Horsepower 6 poles 4 poles 2 poles

1⁄4 hp EC #1 EC #2 EC #3

1/3 hp EC #4 EC #5 EC #6

1⁄2 hp EC #7 EC #8 EC #9

3⁄4 hp EC #10 EC #11 EC #12

1 hp EC #13 EC #14 EC #15

1 1⁄2 hp EC #16 EC #17 EC #18

2 hp EC #19 EC #20 EC #21

>3 hp EC #22 EC #23 EC #24

DOE addresses the details of the scaling relationships, including the basis for how these

were derived, in preliminary TSD chapter 5.

3.2.4 Shipments

To estimate national energy savings from this proposed regulation, DOE will estimate

disaggregated shipments of small electric motors, broken down by equipment class. Individual

manufacturers consider such information to be highly sensitive, which in turn complicates data

collection. NEMA, as the manufacturers’ trade association, offered to coordinate and aggregate

its members’ shipments data. Working through NEMA, DOE prepared a shipments

questionnaire based on the previous data collection tool that was circulated in 2002 for the

determination analysis. In turn, NEMA would receive current shipments data from its members,

aggregate that data, screen out any equipment classes with too few manufacturers reporting, and

provide the combined shipments tables to DOE.

However, there was limited participation from NEMA’s members and consequently DOE

decided to take a new approach. Essentially, DOE chose to use the earlier small electric motors

shipments data it had received from NEMA during the determination analysis, and apply a

growth estimate based on the observed market trends for those motors.n Then DOE took the

small electric motors shipments estimate that NEMA had provided for 2000 and extrapolated

those data to estimate shipments in 2007, based on the observed market growth trends for small

electric motors between 1990 and 1999. (Trend information was extrapolated from U.S. Census

Bureau data.)

In particular, NEMA provided shipment data to DOE on general purpose, AC, polyphase,

single­speed, induction motors built in a two­digit frame number series with open construction

and rated for continuous duty in accordance with MG1–1987. Table 3.2.9 presents the

disaggregated shipments estimates from NEMA.

n The Determination Analysis was published on July 10, 2006. “Energy Conservation Program for Certain

Industrial Equipment: Determination Concerning the Potential for Energy Conservation Standards for Small

Electric Motors.” 71 FR 38799.

3­21

EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.9. National Electrical Manufacturers Association Polyphase Small Electric Motor

Shipment Data, 2000

Horsepower Six Poles Four Poles Two Poles Total

1/4 hp * * * 9,163

1/3 hp 3,788 12,899 2,585 19,272

1/2hp 6,478 39,501 2,856 48,835

3/4 hp 9,729 47,084 65,405 122,218

1 hp * 56,783 * 84,670

1 1/2 hp * 115,638 * 124,959

2­3 hp ­ 22,384 10,149 32,533

441,650

* Data withheld by NEMA due to insufficient number of manufacturers reporting for those ratings/poles.

Using NEMA’s shipment estimates for open drip­proof, polyphase small electric motors,

DOE applied the same average market growth rate observed in the 1990 through 1999 shipment

data. DOE found that the average annual growth rate was 3.4 percent for open drip­proof

polyphase small electric motors. DOE then applied the 3.4 percent average annual growth rate to

the year 2000 estimate that NEMA had provided, and extrapolated it to 2007. Due to an

insufficient number of manufacturers reporting NEMA was unable to provide shipments data for

all the small electric motors in 2000. Therefore, DOE apportioned the unallocated shipments

from the total column among the number of poles. Where no shipment breakdown by poles was

provided, such as for the one­quarter horsepower polyphase motors, DOE used the same

proportional breakdown as the closest rating (i.e., the one­third horsepower) and established an

even, average breakdown between the two and six pole motors.

Table 3.2.10. Estimated Polyphase Small Electric Motor National Shipments, 2007

Horsepower Six Poles Four Poles Two Poles Total

1/4 hp 1,967 7,637 1,967 11,571

1/3 hp 4,784 16,289 3,264 24,338

1/2hp 8,181 49,884 3,607 61,671

3/4 hp 12,286 59,460 82,596 154,342

1 hp 17,608 71,708 17,608 106,925

1 1/2 hp 5,885 146,033 5,885 157,804

2­3 hp ­ 28,268 12,817 41,084

50,712 379,278 127,745 557,735

NEMA provided shipments data to DOE on general purpose, AC, CSIR, single­speed

induction motors built in a two­digit frame number series with open construction and rated for

continuous duty. Table 3.2.11 presents the disaggregated shipments estimate from NEMA.

3­22

EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.11. National Electrical Manufacturers Association Capacitor­Start, InductionRun Small Electric Motor Shipment Data, 2000

Horsepower Six Poles Four Poles Two Poles Total

1/4 hp * 342,064 * 882,878

1/3 hp 551,566 609,264 354,258 1,515,088

1/2hp 301,198 493,151 465,799 1,260,148

3/4 hp * 385,013 * 1,121,644

1 hp ­ 53,042 143,571 196,613

>1 hp ­ 23,638 24,892 48,530

TOTAL 5,024,901

* Data withheld by NEMA due to insufficient number of manufacturers reporting for those ratings/poles.

Using NEMA’s shipments estimates for open drip­proof, CSIR small electric motors,

DOE applied the same average market growth rate observed in the 1990 through 1999 Census

Bureau shipment data. DOE found that the average annual growth rate was 1.1 percent for open

drip­proof CSIR small electric motors. DOE then applied the 1.1 percent average annual growth

rate to the year 2000 estimate that NEMA provided, and extrapolated it to 2007. Due to an

insufficient number of manufacturers reporting, NEMA was unable to provide shipments data for

all the small electric motors in 2000. Therefore, DOE apportioned the unallocated shipments

data, from the total column, in a manner that is proportional to the next closest horsepower

rating.

Table 3.2.12. Estimated Capacitor­Start, Induction­Run Small Electric Motor National

Shipments, 2007

Horsepower Six Poles Four Poles Two Poles Total

1/4 hp 348,160 384,581 223,615 956,357

1/3 hp 597,471 659,971 383,742 1,641,183

1/2hp 326,266 534,194 504,566 1,365,025

3/4 hp 290,405 475,480 449,108 1,214,994

1 hp ­ 57,456 155,520 212,976

>1 hp ­ 25,605 26,964 52,569

TOTAL 1,562,302 2,137,288 1,743,514 5,443,104

Finally, NEMA was unable to provide shipments data for CSCR motors, due to an

insufficient number of manufacturers reporting. However, in its determination analysis, DOE

estimated that CSCR motor shipments represent approximately 5 percent of the shipments of

capacitor­start motors. Therefore, DOE estimated shipments of CSCR motors in 2007 by scaling

the projected CSIR units sold in 2007 to CSCR, based on a 19 to 1 ratio.

3­23

EERE-2007-BT-STD-0007 COMMENT 07.2
Table 3.2.13. Estimated Capacitor­Start, Capacitor­Run Small Electric Motor National

Shipments, 2007

Horsepower Six Poles Four Poles Two Poles Total

1/4 hp 18,324 20,241 11,769 50,335

1/3 hp 31,446 34,735 20,197 86,378

1/2hp 17,172 28,115 26,556 71,843

3/4 hp 15,284 25,025 23,637 63,947

1 hp ­ 3,024 8,185 11,209

>1 hp ­ 1,348 1,419 2,767

TOTAL 82,226 112,489 91,764 286,479

3.2.5 Manufacturers and Market Share

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

• A.O. Smith Electrical Products Company;

• Baldor Electric Company;

• Emerson Motor Technologies; and

• Regal­Beloit Corporation.

The four 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 four companies constitute over 90 percent of the

total U.S. market. Thus, DOE believes that the cumulative shipment estimates provided by

NEMA for the determination analysis constitute a good estimate of overall national shipments.

3.2.5.1 Small Businesses

Although the small electric motor market is predominantly supplied by large

manufacturers, DOE will examine 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 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

1 Manufacturing.

3­24

EERE-2007-BT-STD-0007 COMMENT 07.2
3.2.6 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

• business equipment

• commercial food processing

• compressors

• conveyors

• fans

• farm equipment

• general industrial applications

• heating, ventilation, and air­conditioning equipment

• machine tools

• milking machines

• pumps

• woodworking machines

3.2.7 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).o All four major manufacturers discussed above are members of NEMA and SMMA.

3.2.7.1 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

• 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,p 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

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

about NEMA, visit www.nema.org. p NEMA’s MG 1 document can be purchased online at www.nema.org/stds/MG 1.cfm.

3­25

EERE-2007-BT-STD-0007 COMMENT 07.2
and purchase electric motors. NEMA Standard MG1 is a complete industry reference document

2 for standardizing the motors offered in the market.

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

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

general­purpose motors from 1 to 200 horsepower to meet certain minimum efficiency levels.

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

3.2.7.2 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, in­house educational courses from the SMMA Motor and Motion

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

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, pre­competition research, and facilitation of technology transfer within the industry

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

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

teaching and providing information on new motor technologies.

3.2.8 Regulatory Programs

Under EPCA, as amended by EPACT 1992, each general­purpose three­phase 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

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

amendment are defined as “T­frame” and constructed according to NEMA standard three­digit

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

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

dimensions for mounting and interchangeability are fundamentally different from “T­frame”

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.

q ® NEMA’s Premium Motors program can be reviewed at www.nema.org/gov/energy/efficiency/premium. r Information about the SMMA Motor and Motion College can be obtained at

www.smma.org/motor.college.schedule.html.

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EERE-2007-BT-STD-0007 COMMENT 07.2
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 MG 1–

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 MG

1–2006, 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.

3.2.9 Non­Regulatory 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..

3.2.9.1 Department of Energy Motor Challenge Program

In general, motor­driven 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 energy­efficiency of electric motordriven systems in domestic industry and enhancing environmental quality. The program uses a

market­driven approach to promote the design, purchase, installation, and management of

energy­efficient electric motors and motor­driven systems and equipment, such as pumps, fans,

and compressors. It was designed to help industry capture 5 billion kilowatt­hours per year of

electricity savings and 1.2 million metric tons of carbon equivalent by the year 2000, with

projections of much larger and longer­term national energy savings opportunities of over 100

billion kilowatt­hours per year by the year 2010.s

The Motor Challenge program encompasses three­phase 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 up­to­date 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

s 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.

3­27

EERE-2007-BT-STD-0007 COMMENT 07.2
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.t

MotorMaster+ is an energy­efficient 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.u 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.

3.2.9.2 National Electrical Manufacturers Association Premium Efficiency Motor

Program

On January 11, 1989, NEMA established voluntary energy efficiency levels for 1 through

200 horsepower, polyphase squirrel­cage 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

4 v optimize motor system efficiency commensurate with a particular application.

Going a step beyond EPACT, NEMA Premium applies to single­speed, polyphase; 1 to

500 horsepower; 2­, 4­, and 6­pole; squirrel­cage; induction motors; NEMA Designs A or B; 600

5 volts or less; and rated for continuous duty operation. 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, capacitor­start induction­run, and

capacitor­start capacitor­run small electric motors at premium efficiency levels.

t

For more information about the EERE Information Center, visit

http://www1.eere.energy.gov/industry/bestpractices/info_center.html.

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

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

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

3­28

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EERE-2007-BT-STD-0007 COMMENT 07.2
3.2.9.3 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 Premium­Efficiency 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 system­specific 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

6 levels that are higher than EPACT 1992 requirements.

In May 2007, CEE published the Energy­Efficiency Incentive Programs – PremiumEfficiency Motors & Adjustable Speed Drives in the U.S and Canada, which provides

information about the incentive­based 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.w There are a number of

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

7 the report from CEE.

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

w For more information about CEE motor and motor systems programs, visit http://www.cee1.org/ind/mot­sys/mtrms­main.php3.

3­29

EERE-2007-BT-STD-0007 COMMENT 07.2
2 covered in this rulemaking, energy efficiency losses are grouped into four main categories: I 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.

2 3.3.1 Technology Options for I R Losses

2

I 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

2 efficiency motors that use copper are now available. I 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 cross­sectional 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.

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

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

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

2 than aluminum, and changing from aluminum bars to copper would reduce associated I R losses

in the rotor.

2 Manipulation of the rotor’s geometrical design is another approach to reduce I R losses in

the rotor. For the motors covered in this rulemaking, the rotors are called “squirrel­cage 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

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 speed­torque

characteristics of the motor. The cusps in the speed­torque 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 speed­torque characteristics.

Another change to the rotor bar geometry that can reduce resistance is increasing the

cross­sectional 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 cross­sectional 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

2 help decrease resistance and alleviate some of the I R losses.

3­30

EERE-2007-BT-STD-0007 COMMENT 07.2
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 conduct bar shape could induce

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

create cusps in the speed­torque 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.

2

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

manufacturers may attempt 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 cross­sectional 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 cross­sectional area relative to the total slot crosssectional area. Depending on the number of poles in the motor, certain length­to­diameter ratios

are better suited to balance the magnetic circuit.

2 Another way for manufacturers to reduce I R 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

2

I 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 0.010 inch.

3.3.2 Technology Options for Core Losses

Core losses are those losses created in the steel components of a motor. These losses,

2 like I 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 several turns of wire in the stator. Monitored starting torque is also

3­31

EERE-2007-BT-STD-0007 COMMENT 07.2
important because an increased stack may reduce torque, 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 common 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 so­called “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:” cold­rolled magnetic

laminations (CRML), fully processed non­oriented electrical steel, and semi­processed 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.x Semi­processed electrical steels are

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

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 non­standard thicknesses that are harder to manufacture.

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

steel. Using thinner laminations decreases the cross­sectional 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

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

3­32

EERE-2007-BT-STD-0007 COMMENT 07.2
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

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.

Table 3.3.1. 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 Cold­rolled magnetic laminations (semiprocessed)

26 M47 0.019 2.80 Watts/lb at 1.5 T Non­oriented electrical steel (fully processed)

24 M36 0.025 2.35 Watts/lb at 1.5 T Non­oriented electrical steel (fully processed)

24 M19* 0.025 2.00 Watts/lb at 1.5 T Non­oriented electrical steel (fully processed)

29 M15* 0.014 1.45 Watts/lb at 1.5 T Non­oriented electrical steel (fully processed)

Hiperco

50* 0.006 1.00 Watts/lb at 1.5 T Iron­cobalt­vanadium soft magnetic alloy

SA1 0.001 0.08 Watts/lb at 1.3 T Amorphous core steel (silicon and boron);

flux density limitation–testing at 1.3 T†

* 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 SI­derived 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 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.

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EERE-2007-BT-STD-0007 COMMENT 07.2
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 pre­wound 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

9 motor design.

3.3.2.2 Permanent Magnet Electric Motor

Permanent magnet motors are made in many configurations. The most common are

brushless DC motors and brushless AC motors. These motors use a permanent magnet for the

rotating member instead of a squirrel­cage rotor. They may also require an electronic controller

to operate, which increases the cost of the system and requires extra space. Permanent magnet

motors do not have the same operating characteristics as an induction motor. They are less

rugged than induction motors and are subject to conditions that may cause demagnetization. It is

possible to make a permanent magnet motor that will operate without the aid of a controller.

These motors are synchronous in nature and have a different speed torque profile than an

induction motor. However, none of these motors meet the requirements of a NEMA generalpurpose motor.

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 well­designed 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

2 Any losses that are otherwise unaccounted for and not attributed to I R losses, steel

losses, or frictional and windage losses are considered stray­load losses. DOE is not aware of

any specific techniques manufacturers use to reduce stray­load losses. General process changes

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

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EERE-2007-BT-STD-0007 COMMENT 07.2
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.

.

Table 3.3.2. Summary of Technology Options for Improving Efficiency

Type of Loss to Reduce Technology Option Applied

Use copper die­cast rotor cage

Remove skew on conductor cage

Increase cross­sectional area of rotor conductor bars

I

2

R Losses Increase end ring size

changing gauges of copper wire in stator

Manipulate stator slot size

Decrease the radial air gap

Improve grades of electrical steel

Use thinner steel laminations

Anneal steel laminations

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

laminations)

Use high­efficiency lamination materials

Use plastic bonded iron powder

Use a permanent magnet electric motor

Friction and Windage Losses Use better bearings and lubricant

Install a more efficient cooling system

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EERE-2007-BT-STD-0007 COMMENT 07.2
REFERENCES

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

American Industry Classification System. 2006. (Last accessed April 21, 2008.)

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

April 21, 2008, material from this website is available in Docket # EERE–2007–BT–STD–0007.

2 National Electric Manufacturers Association. (Last accessed April 21, 2008.)

<http://www.nema.org/about/upload/NEMACorpBrochure05.pdf > The April 21, 2008, material

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

3 Small Motor and Motion Association. January 8, 2008. (Last accessed April 21, 2008.)

<http://www.smma.org/> The April 21, 2008, 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. March 12, 2002. (Last accessed April 21, 2008.)

<http://www.nema.org/stds/complimentary­docs/upload/MG 1MG 1premium.pdf> The April

21, 2008, material from this website is available in Docket #EERE–2007–BT–STD–0007.

6 Consortium for Energy Efficiency. Industrial Programs Premium­Efficiency Motors. 2008.

(Last accessed April 21, 2008.) < http://www.cee1.org/ind/motrs/motrs­main.php3> The April

21, 2008, material from this website is available in Docket #EERE–2007–BT–STD–0007.

7 Consortium for Energy Efficiency. Energy­Efficiency Incentive Programs, Premium­Efficiency

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

<http://www.motorsmatter.org/tools/programs2007.pdf>

8 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.

9 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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EERE-2007-BT-STD-0007 COMMENT 07.2