c) STANDARDS PUBLICATION/NO. MG 11-1977

(9;)

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TCPC/E$,1 3

energy

management

guide for

selection

and use of

singlephase

motors

NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION 2101 L STREET N.W., WASHINGTON, D.C. 20037
FEA STATEMENT....

PREFACE

- Page

1977 by National Electrical Manufacturers Association

Printed in U.S.A.

1

2

2

4

5

Date Due

€B2 1995

1qF I 0

PART l—lNTRODUC

PART lI—GENERAL C

PART Ill—TYPES OF

PART IV—SELECTIO KEH411(1-84)

PART V—CONCLUSION
J r”

V

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OF KH-LIBRARY

iGPC/6-1 3

FEDERAL ENERGY ADMINISTRATION

WASHINGTON, D.C. 20461

The National Electrical Manufacturers Association (NEMA) has produced

two technical bulletins, “Energy Management Guide for the Selection and

Use of Polyphase Motors,” and “Energy Management Guide for the Selection

and Use of Single—Phase Motors,” to provide practical guidelines for

electric motor users. The large number of electric motor requirements

in this country plays an important role in determining America’s total

electric energy consumption. These publications are meant to help the

end—user make knowledgeable judgments in the selection, application, and

maintenance of these motors.

While NEMA was developing these bulletins, the Federal Energy Adminis

tration (FEA) was directing the preparation of a study entitled “Energy

Efficiency and Electric Motors.” The focus of the FEA study which is

available for purchase through the National Technical Information Service

(PB 259129—29—AS — $7.50) is on energy efficiency in the 1— to 125—HP motor

category. The NEMA bulletins direct attention to both large and small

electric motor applications. This cooperation between NEMA and FEA has

produced documents which complement one another in assisting the motor

end—user. We expect this kind of cooperation between the private sector

and the Government to continue and to contribute to the implementation of

further energy conservation programs related to electric motors.

s K. Pont

sociate Assistant Admflüstrator

National Energy Conservation Programs

Energy Conservation and Environment

1
.

PREFACE

The Motor and Generator Section of NEMA recognized the need for energy

management in motor, applications and organized the Energy Management Com

mittee in the Spring of 19’15. Because motors are part of a system, the Com

mittee concluded that technical information bulletins (or guides) describing

motor performance characteristics should be developed to assist users in apply

ing motors.

This Publication No. MG 11-1977 is the result of the Committee’s work on

single-phase motors. Polyphase motors are covered separately in the “Energy

Management Guide for the Selection and Use of Polyphase Motors, “ MG lO-1977.

The Guide will be reviewed periodically by the Motor and Generator Section

for the purpose of keeping it up t.o date with advancing technology. Comments

will be welcome. They should be addressed to:

Manager, Etigineering

National Electrical Manufacturers Association

2101 L Street, N. W.

Washington, D.C. 20037

11
ENERGY MANAGEMENT GUIDE FOR

SELECTION AND USE OF SINGLE-PHASE MOTORS

(Approved as Authorized Engineering Information 11-11-1976.)

Part I

INTRO DU CT I ON

There is an urgent need to conserve energy resources. Therefore, it is im

portant that motor users and specifiers understand the selection, application and

maintenance of electric motors in order to im.prove the management of electrical

energy consumption. “Energy Management” as related to single-phase electric

motors is a concept in which all factors of the total electric motor drive system

are considered in the reduction of energy consumption.

One of the factors to be considered is the motor itself. An electric motor is

an energy converter, converting electrical energy to mechanical energy. For

this reason, an electric motor should be considered as always being connected

to a driven machine or apparatus which has specific operating characteristics

such as starting, speed and load. Consequently, the selection of the motor most

suitable for any particular application generally involves a host of factors, many

of which conflict with one another to some degree. Fractional-horsepower motors

in the 1/20 through 1 horsepower size are generally connected to single-phase

power systems which are found in homes or small businesses and are most fre

quently used to drive household or commercial appliances.

The system efficiency is the combination of the efficiencies of all of the

components in the system. These components include belts, pulleys, fans,

pumps, gears and, in the case of refrigeration, such items as the compressor.

Other components which are not a part of the system will affect the overall

system efficiency; some of these are refrigeration and air conditioning evaporator

and condenser coils, plumbing associated with pumps, and ducts and baffles as

sociated with fans and blowers. Selection of a motor to provide for the most

efficient system is based on factors such as speed, load versus horsepower, duty

cycle, type, and initial motor cost, as well as motor efficiency.

Good energy management is the successful application of the motor and its

driven components that results in the least consumption of energy.

1
Part II

GENERAL CONCEPTS

The design of an electric motor involves a balance between characteristics

such as starting and running, thermal performance and material utilization.

Operating efficiency involves a careful consideration of these motor performance

characteristics, relating them to the requirements of the specific application

and the efficiency of the system of which the motor is a part.

A change in efficiency as a function of load is an inherent characteristic of

motors. Operation at less than rated load will result in a substantial reduction

in motor efficiency. Oversizing (the use of a motor having an output rating

greater than the load), should be avoided.

Motor efficiency can be improved by matching the voltage and frequency of

the motor with those of the power supply. The use of motors having a voltage

range (i. e, 200-230 volts) or a dual frequency (i.e. 60/50 hz) should be avoided.

In general, for a given type, motors with larger horsepower ratings are more

efficient than those with smaller horsepower ratings. In addition, motors with

higher synchronous speeds are generally more efficient than those with lower

synchronous speeds. This does not imply, however, that all apparatus should be

driven by high-speed motors. Where speed-changing mechanisms, such as pulleys

or gears, are required to obtain the lower speeds, the additional power losses

could reduce the efficiency of the system to a value lower than that provided by

a direct-drive lower-speed motor,

Many motors are used for very short periods of time and for a very low total

number of hours per year. Examples of such applications are can openers, food

waste disposers, electric lawn mowers, power tools, etc. In these instances, a

change in motor efficiency would not substantially change the total energy con

sumed since very little total energy is involved. -

On the other hand, many motors are used for long periods of time and for a

high total number of hours per year. Examples of such applications are air

moving equipment, circulator pumps, refrigeration compressors, etc. In these

instances, an inrease in motor efficiency could substantially reduce the total

energy consumed.

Part III

TYPES OF MOTORS

The most commonly used single-phase motors are those of the induction type

because of their simplicity, dependability, and relatively constant speed. In

duction motors include the following sub-types: shaded-pole, split-phase,

capacitor-start, and permanent-split capacitor. Universal motors are also com

monly used on single-phase power systems in homes on specific applications.

The following is a brief description of each motor type and its primary appli

cation:

2
A. SHADED-POLE MOTORS

Shaded -pole motors are used in a wide variety of applications requiring 1/4

horsepower or less, and the vast majority of applications require less than 1/10

horsepower. They are simple in construction, low in cost, and extremely rugged

and reliable because they do not have commutators, starting switches, collector

rings, brushes, governors, or contacts of any sort. Their low startiTig torque and

efficiency confines the use of shaded-pole motors to such appliances as rotis

series, fans, humidifiers, slide projectors, and small business machines such as

copying machines, vending machines, advertising displays, etc. , many of which

are intended for intermittent operation. Because of the combination of low

horsepower rating and intermittent operation of many of these applications, the

total power consumed by shaded -pole motors normally represents only a small

portion of the total power consumed by electric motors.

B. SPLIT-PHASE MOTORS

Split-phase motors are among the most widely used of all types of single—

phase motors in ratings ranging from 1/12 to 1/2 horsepower. They will be found

in laundry equipment, oil burners, furnace blowers, attic fans, centrifugal

pumps, compressors, business machines, buffing machines, grinders, home work

shop tools, and a host of other applications. Split-phase motors are charac

terized by medium starting torque, high starting current, and medium efficiency.

C. CAPACITOR-START, INDUCTION-RUN MOTORS

Capacitor-start inductionrun motors are most widely used in ratings of 1/8

horsepower and larger for applications where higher starting characteristics are

required. They are characterized by high starting torque, low starting current,

and medium efficiency.

D. CAPACITOR-START CAPACITOR-RUN MOTORS

Capacitor-start capacitor-run motors are most widely use in ratings of 1/3

horsepower and larger for applications where high starting torque, low starting

current, low operating current and high efficiency are required.

E. PERMANENT-SPLIT CAPACITOR MOTORS

Permanent-split capacitor motors are used in direct-drive applications re

quiring ratings ranging from 1/20 to 1 horsepower, suchas fans, business machines

and hermetic motor compressors. They are characterized by low starting torque,

low starting current and high efficiency.

F. UNIVERSAL MOTORS

Universal motors are used in ratings from 1/10 to 1 horsepower in applications

involving vacuum cleaners, hand-held tools, and appliances which operate inter

mittently. They are characterized by high starting torque, low starting current,

medium to low efficiency, and varying speed.

3
Part IV

SELECTION AND APPLICATION

In the selection of single-phase motors for application to the driven equip

ment, the efficiency of the total electric motor- system must always be con

sidered for good energy management. Some of the factors to be evaluated are

as follows:

A. SHORT OR INTERMITTENT DUTY CYCLE OPERATION

Applications involving can openers, vacuum cleaners, hand -held tools,

mixers, blenders, electric knives, etc., fall in this category. Because these

appliances operate for short periods of time, even a large increase in the effi

ciency of the motor or system would have only a negligible effect on total power

consumption.

B. MOTOR SPEED

Although a, 2-pole motor generally has a higher efficiency, the gearing or

belting necessary to reduce the speed to that required by the driven equipment

may have efficiencies that would reduce the efficiency of the system to a value

lower than that which could be obtained with a 4-, 6- or 8-pole motor, the use -

of which would not require a reduction in speed.

C. LOADING

The motor horsepower rating should be so selected that the load imposed on

the motor will cause it to operate close to its full-load rating.

D. MOTOR TYPE

The most important consideration in selecting a motor of the appropriate type

is to obtain a motor that will perform satisfactorily for the application involved.

Universal motors must be used where high speeds are required, where increasing

the speed of induction motors is not feasible,or when varying speeds are desired.

Shaded-pole motors are generally used where low starting torque and low ef

ficiency are acceptable because of the intermittent duty of the application.

Permanent-split capacitor motors are used where low starting torque is accept

able and a higher efficiency is desired. Split-phase motors are used for generalpurpose applications where medium starting torque is required. Capacitor-start

motors are generally used where high starting torque is required. TableMGll-1

may be used as a guide for selecting the proper motor for the major applica

tion s listed.

E. EVALUATION OF INCREASED EFFICIENCY

For two similar motors operating at the same specified load, but having dif

ferent efficiencies, the following equation can be used to calculate the savings

in operating costs when using motor A rather than motor B:

fioo 100 ‘ . S = 0. 746 x HP x C -x N I — - —

\EB EA

4
Where —

S Savings in dollars per year

HP = Horsepower rating of the specified load

C Energy cost, dollars per kilowatt hour

N Running time, hours per year

EA Efficiency (in percent) of motor A at the specified load

EB = Efficiency (in percent) of motor B at the specified load

The equation applies to motors operating at a specified constant load. For

varying loads, the equation can be applied to each portion of the cycle where

the load is relatively constant for an appreciable period of time. The total

savings are the sum of the savings for each load-time period.

The equation is not applicable to motors’ operating on pulsating loads or on

loads which cycle at rapidly repeating intervals.

Part V

CONCLUSION

Proper selection, application and maintenance of electric motors is essential

to an effective energy management program. With today’s increasing shortages

and costs of energy, energy management is becoming increasingly important. It

is crucial to the Country from the standpoint of conservation of natural resources,

energy independence and energy availability. As part of a system, electric

motors play a significant role in determining the total energy consumption;

however, they cannot be considered alone and are only one factor in any analysis

of an entire syste.m.

5
Table MG 11-1

0)

S

Alternating-current Single-phase Fractional-horsepower Motors Rated 1/20 to 1 Horsepower, 250 Volts or Less

C

Application Motor Type Horsepower Speed, RPM Starting Torque Efficiency

Fans

Direct Drive Permanent Split Capacitor 1/20-1 1625, 1075, 825 Low High

Shaded Pole 1/20-1/4 1550, 1050, 800 Low LowSplit Phase 1/20-1/2 1725, 1140, 850 Low Medium

Belted Split Phase 1/20-1/2 1725, 1140, 850 Medium Medium

Capacitor Start - Induction Run 1/8-3/4 1725, 1140, 850 Medium Medium

Capacitor Start - Capacitor Run 1/8-3/4 1725, 1140, 850 Medium High

Pumps

Centrifugal Split Phase 1/8-1/2 3450 Low Medium

Capacitor Start - Induction Run 1/8-1 45O Medium MediumCapacitor Start - Capacitor Run 1/8-1 3450 Medium High

Positive Displacement ... Capacitor Start - Induction Run 1/8-1 3450, 1725 High Medium

Capacitor Start - Capacitor Run 1/8-1 3450, 1725 High High

Compressors

Air Split Phase 1/8-1/2 3450, 1725 Low or Medium Medium

Capacitor Start - Induction Run 1/8-1 3450, 1725 High Medium

Capacitor Start - Capacitor Run 1/8-1 — 3450, 1725 High High

Refrigeration Split Phase 1/8-1/2 3450, 1725 Low or Medium Medium

Permanent Split Capacitor 1/8-1 3250, 1625 Low High

Capacitor Start - Induction Run 1/8-1 3450, 1725 High MediumCapacitor Start - Capacitor Run 1/8-1 3450, 1725 High High

Industrial Capacitor Start - Induction Run 1/8-1 3450, 1725, 1140, 850 High Medium

Capacitor Start - Capacitor Run 1/8-1 3450, 1725, 1140, 850 High High

Farm Capacitor Start - Induction Run 1/8-3/4 1725 High Medium

Capacitor Start - Capacitor Run 1/8-3/4 1725 High High

Major Appliances Split Phase 1/6-1/2 1725, 1140 Medium Medium

Capacitor Start - Induction Run 1/6-3/4 1725, 1140 High Medium

Capacitor Start - Capacitor Run 1/6-3/4 1725, 1140 High High

Commercial Appliances .... Capacitor Start - Induction Run 1/3-3/4 1725 High Medium

Capacitor Start - Capacitor Run 1/3-3/4 1725 High High

Business Equipment Permanent Split Capacitor 1/20-1/4 3450, 1725 Low High

Capacitor Start - Induction Run 1/8-1 3450, 1725 High Medium

Capacitor Start - Capacitor Run 1/8-1 3450, 1725 High High
NEMA STANDARDIZATION

The purpose of NEMA Standards, their classification and status are set forth in

certain clauses of the NEMA By-Laws. which are quoted below:

Purpose of Standards

National Electrical Manufacturers Association Standards are adopted in the public Interest and are designed to

eliminate misunderstandings between the manufacturer and the purchaser and to assist the purchaser in selecting

and obtaining the proper product for its particular need. Existence of a National Electrical Manufacturers

Association Standard does not in any respect preclude any member or non-member from manufacturing or selling

products not conforming to the Standard.

(By-Law--Art. V. Sec. 1)

Definition of a Standard

A Standard of the National Electrical Manufacturers Association defines a product. process or procedure with

reference to one or more of the following: nomenclature, composition, construction, dimensions, tolerances,

safety, operating characteristics, performance, quality, rating, testing and the service for which designed.

(By-Law—Art. V. Sec. 2, Subsection A)

Classes of Standards

National Electrical Manufacturers Association Standards are of two classes:

1 NEMA Standard, which relates to a product commercially standardized and subject to repetitive manufac

ture, which standard has been approved by at least 90 per cent of the members of the Subdivision eligible to vote

thereon;

2. Suggested Standard for Future Design, which may not have been regularly applied to a commercial product.

but which suggests asound engineering approach to future development, which standard has been approved by at

least two-thirds of the members of the Subdivision eligible to vote thereon.

(By-Law—Art. V, Sec. 2, Subsection B)

Authorized Engineering Information

Authorized Engineering Information consists of explanatory data and other engineering information of an in

formative character not falling within the classification of NEMA Standard or Suggested Standard for Future Design.

(By-Law—Art. V, Sec. 6, 1st Sentence)

Identification of Status

At the end of each standard in this publication appear the words “NEMA Stand

ard” or “Suggested Standard for Future Design. “ which indicate the status of the

standard. These words are followed by a date which indica,tes when that standard

was adopted in its present form by the Association.

The classification “Authorized Engineering Information” is designated simifarly.
MOTOR AND GENERATOR SECTION

OF THE

NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION

MEMBER COMPANIES

Allis-Chalmers Corp. Electric Machinery Mfg. Co. Ideal Electric & Manufacturing Co., The

Milwaukee, Wis. 53201 Division of Turbodyne Corp. Mansfield, Ohio 44903

Minneapolis, Minn. 55413

Allis, Louis, Co., The Imperial Electric Co. • The

Division Electrolux Division of of Litton Industries Akron, Ohio 44309

Milwaukee, Wis. Consolidated Foods Corp. 53201

Old Greenwich, Conn. 06870

The Lincoln Electric Co.

Ametek, Inc. Emerson Electric Co. Cleveland, Ohio 44117

Lamb Electric Division St. Louis, Mo. 63136

Kent, Ohio 44240

Marathon Electric Manufacturing Corp. U. S. Electrical Motors Division

Wausau, Wis. 54401 Emerson Electric Co. Baldor Electric Co.

Milford, Coon. 06460 Fort Smith, Ark. 72901 Ohio EleOtric Motors Division

Northwestern Electric Division Magnetics International, Inc.

Beloit Power Systems, Inc. Emerson Electrtc Co. Maple Heights, Ohio 44137

Beloit, Wis. 53511 Chicago, Ill. 60647

Otis Elevator Co.

Franklin Electric CO., Inc. Bodine Electric Co. Mahwah, N.J. 07430

Bluffton, md. 46714 Chicago, Ill. 60618

General Electric Co. Reliance Electric Co.

Chandeysson Electric Division Schenectady, N.Y. 12345 Cleveland, Ohio 44117

Abex Corp.

St. Louis, Mo. 63116 Gould Inc.

The Sievert Electric Co. Electric Motor Division

Delco Products Division of St. Louis, Mo. 63166 Chicago, Ill. 60622

General Motors Corp.

Dayton, Ohio 45401 Hamischfeger Corp. Sterling Power Systems, Inc.

Milwaukee, Wis. 53246 (A Subsidiary of the Lionel Corp.)

Electra Motors Operations Irvine, Calif. 92714

Power Transmission Division Howell Electric Motors

Dresser Industries, Inc. A Unit of SFM Corp. Westinghouse Electric Corp.

Anaheim, Calif. 92803 Plainfleld, N.J. 07061 Buffalo, N.Y. 14240

Printed in U.S.A.