# c)

STANDARDS PUBLICATION/NO. MG 11-1977
(9;)



# RETURN TO CF KH-LIBRARY TCPC/E$,1

3



# energy management guide for selection and use ofsinglephase motors

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

PREFACE - Page

1977 by National Electrical Manufacturers Association

Printed in U.S.A. 1

2

2

4

5 

### Date Due
€B2 

## 1995
1 qF I 

### 0

PART l—lNTRODUC

PART lI—GENERAL C

PART Ill—TYPES OF

PART IV—SELECTIO KEH411(1-84)

PART V—CONCLUSIONJ 

### r”

V 

# RETURN TO 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

11ENERGY 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.

1Part 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:

2A. 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.

3Part 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

4Where

—

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.

5TableMG11-10) SAlternating-currentSingle-phaseFractional-horsepowerMotorsRated1/20to1Horsepower,250VoltsorLess

CApplicationMotorTypeHorsepowerSpeed,RPMStartingTorqueEfficiencyFansDirectDrivePermanentSplitCapacitor1/20-11625,1075,825LowHighShadedPole1/20-1/41550,1050,800LowLowSplitPhase1/20-1/21725,1140,850LowMediumBeltedSplitPhase1/20-1/21725,1140,850MediumMediumCapacitorStart-InductionRun1/8-3/41725,1140,850MediumMediumCapacitorStart-CapacitorRun1/8-3/41725,1140,850MediumHighPumpsCentrifugalSplitPhase1/8-1/23450LowMediumCapacitorStart-InductionRun1/8-145OMediumMediumCapacitorStart-CapacitorRun1/8-13450MediumHighPositiveDisplacement...CapacitorStart-InductionRun1/8-13450,1725HighMediumCapacitorStart-CapacitorRun1/8-13450,1725HighHighCompressorsAirSplitPhase1/8-1/23450,1725LoworMediumMediumCapacitorStart-InductionRun1/8-13450,1725HighMediumCapacitorStart-CapacitorRun1/8-1—3450,1725HighHighRefrigerationSplitPhase1/8-1/23450,1725LoworMediumMediumPermanentSplitCapacitor1/8-13250,1625LowHighCapacitorStart-InductionRun1/8-13450,1725HighMediumCapacitorStart-CapacitorRun1/8-13450,1725HighHighIndustrialCapacitorStart-InductionRun1/8-13450,1725,1140,850HighMediumCapacitorStart-CapacitorRun1/8-13450,1725,1140,850HighHighFarmCapacitorStart-InductionRun1/8-3/41725HighMediumCapacitorStart-CapacitorRun1/8-3/41725HighHighMajorAppliancesSplitPhase1/6-1/21725,1140MediumMediumCapacitorStart-InductionRun1/6-3/41725,1140HighMediumCapacitorStart-CapacitorRun1/6-3/41725,1140HighHighCommercialAppliances....CapacitorStart-InductionRun1/3-3/41725HighMediumCapacitorStart-CapacitorRun1/3-3/41725HighHighBusinessEquipmentPermanentSplitCapacitor1/20-1/43450,1725LowHighCapacitorStart-InductionRun1/8-13450,1725HighMediumCapacitorStart-CapacitorRun1/8-13450,1725HighHighNEMA 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 Electrolux Division of Division of Litton Industries Akron, Ohio 44309 Consolidated Foods Corp. Milwaukee, Wis. 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.