1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA MG 11-1977 (R2012)Energy Management Guide for Selection and Use of Single-Phase MotorsNEMA MG 11-1977 (R1997, R2001, R2007, R2012) Energy Management Guide for Selection and Use of Single-Phase Motors Published by National El
2、ectrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, VA 22209 www.nema.org Copyright 2012 by National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the
3、 Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. MG 11-1977 (R1997, R2001, R2007, R2012) Page ii Copyright 2012 by the National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered techn
4、ically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. NEMA standards and guideline publ
5、ications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the
6、process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publica
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13、 of the statement. MG 11-1977 (R1997, R2001, R2007, R2012) Page iii Copyright 2012 by the National Electrical Manufacturers Association CONTENTS FOREWORD AND SCOPE iv Section 1 INTRODUCTION . 1 Section 2 GENERAL CONCEPTS 2 Section 3 TYPES OF MOTORS 3 3.1 SHADED-POLE MOTORS 3 3.2 SPLIT-PHASE MOTORS 3
14、 3.3 CAPACITOR-START, INDUCTION-RUN MOTORS. 3 3.4 CAPACITOR-START, CAPACITOR-RUN 3 3.5 PERMANENT-SPLIT CAPACITOR MOTORS 3 3.6 UNIVERSAL MOTORS . 3 Section 4 SELECTION AND APPLICATION 4 4.1 SHORT OR INTERMITTENT DUTY CYCLE OPERATION 4 4.2 MOTOR SPEED 4 4.3 LOADING . 4 4.4 MOTOR TYPE . 4 4.5 EVALUATIO
15、N OF INCREASED EFFICIENCY . 4 Section 5 CONCLUSION. 6 MG 11-1977 (R1997, R2001, R2007, R2012) Page iv Copyright 2012 by the National Electrical Manufacturers Association FOREWORD The Motor and Generator Section of NEMA recognized the need for energy management in motor applications and organized the
16、 Energy Management Committee in the Spring of 1975. Because motors are part of a system, the Committee concluded that technical information bulletins (or guides) describing motor performance characteristics should be developed to assist users in applying motors. The first edition of MG 11 was subseq
17、uently published in 1977 with the statement to periodically review the guide for the purpose of keeping it up to date with advancing technology. This reaffirmation, MG 11-1977 (R1997, R2001, R2007), is the result of this commitment. The goal of this guide is to assist the reader in the choice of sin
18、gle-phase motors for his application. Polyphase motors are covered separately in the Energy Management Guide for the Selection and Use of Polyphase Motors, MG 10-2001 (R2007). The practice of periodically reviewing and updating the guide will be continued. Comments on the guide from readers are welc
19、omed and should be addressed to: Senior Technical Director, Operations National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, VA 22209 SCOPE This energy management guide provides practical information concerning the proper selection and application of single-phase
20、induction motors including installation, operation, and maintenance. MG 11-1977 (R1997, R2001, R2007, R2012) Page 1 Copyright 2012 by the National Electrical Manufacturers Association Section 1 INTRODUCTION There is an urgent need to conserve energy resources. Therefore, it is important that motor u
21、sers and specifiers understand the selection, application and maintenance of electric motors in order to improve 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
22、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 m
23、achine 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. Small (fractional-hor
24、sepower) 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 frequently used to drive household or commercial appliances. The system efficiency is the combination of the efficiencies of all of th
25、e 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
26、 evaporator and condenser coils, plumbing associated with pumps, and ducts and baffles associated 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
27、 efficiency. Good energy management is the successful application of the motor and its driven components that results in the least consumption of energy. MG 11-1977 (R1997, R2001, R2007, R2012) Page 2 Copyright 2012 by the National Electrical Manufacturers Association Section 2 GENERAL CONCEPTS The
28、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 appl
29、ication 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 r
30、ating 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 (e.g., 200-230 volts) or a dual frequency (e.g., 60/50 Hz) should be avoided. In general, for a
31、 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 drive
32、n 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 sho
33、rt 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 consumed since very litt
34、le 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 increase in motor efficiency c
35、ould substantially reduce the total energy consumed. MG 11-1977 (R1997, R2001, R2007, R2012) Page 3 Copyright 2012 by the National Electrical Manufacturers Association Section 3 TYPES OF MOTORS The most commonly used single-phase motors are those of the induction type because of their simplicity, de
36、pendability, and relatively constant speed. Induction motors include the following sub-types: shaded-pole, split-phase, capacitor-start, and permanent-split capacitor. Universal motors are also commonly used on single-phase power systems in homes on specific applications. The following is a brief de
37、scription of each motor type and its primary application: 3.1 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
38、extremely rugged and reliable because they do not have commutators, starting switches, collector rings, brushes, governors, or contacts of any sort. Their low starting torque and efficiency confines the use of shaded-pole motors to such appliances as rotisseries, fans, humidifiers, slide projectors,
39、 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
40、-pole motors normally represents only a small portion of the total power consumed by electric motors. 3.2 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 horsepower. They are found in laundry equipment, oil burn
41、ers, furnace blowers, attic fans, centrifugal pumps, compressors, business machines, buffing machines, grinders, home workshop tools, and a host of other applications. Split-phase motors are characterized by medium starting torque, high starting current, and medium efficiency. 3.3 CAPACITOR-START, I
42、NDUCTION-RUN MOTORS Capacitor-start induction-run 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. 3.4 CAPACITOR-START,
43、 CAPACITOR-RUN Capacitor-start capacitor-run motors are most widely used 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. 3.5 PERMANENT-SPLIT CAPACITOR MOTORS Permanent-split capacitor m
44、otors are used in direct-drive applications requiring ratings ranging from 1/20 to 1 horsepower, such as fans, business machines and hermetic motor compressors. They are characterized by low starting torque, low starting current and high efficiency. 3.6 UNIVERSAL MOTORS Universal motors are used in
45、ratings from 1/10 to 1 horsepower in applications involving vacuum cleaners, hand-held tools, and appliances which operate intermittently. They are characterized by high starting torque, low starting current, medium to low efficiency, and varying speed. MG 11-1977 (R1997, R2001, R2007, R2012) Page 4
46、 Copyright 2012 by the National Electrical Manufacturers Association Section 4 SELECTION AND APPLICATION In the selection of single-phase motors for application to the driven equipment, the efficiency of the total electric motor system should always be considered for good energy management. Some of
47、the factors to be evaluated are as follows: 4.1 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 in
48、crease in the efficiency of the motor or system would have only a negligible effect on total power consumption. 4.2 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 efficienci
49、es 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. 4.3 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. 4.4 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 are used where high speeds are required, whe
