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1、 NEMA AB 3 NEMA AB 3 MOLDED CASE CIRCUIT BREAKERS AND THEIR APPLICATION Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without
2、 license from IHS -,-,- Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- NEMA Standards Publicati
3、on AB 3-2006 Molded Case Circuit Breakers and their Application Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, Virginia 22209 www.nema.org Copyright 2006 by the National Electrical Manufacturers Association. All rights including translation in
4、to other languages, reserved under the Universal Copyright Convention, the Berne Convention or the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMAL
5、icensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensus of persons engaged in the developmen
6、t 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 publications, of which the document contained herein is one, are devel
7、oped 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 process and establishes rules to promote fairness in the developme
8、nt 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 publications. NEMA disclaims liability for any personal injury, property,
9、 or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, expressed or implied, as to the accuracy
10、or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by
11、 virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this
12、document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other
13、sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations fo
14、r safety or health purposes. Any certification or other statement of compliance with any health or safetyrelated information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. Copyright National Electrical Manufacturers Ass
15、ociation Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- AB 3-2006 Page i Copyright 2006 by the National Electrical Manufacturers Association. CONTENTS
16、Page Foreword.iii Section 1 GENERAL 1.1 Scope.1 1.2 References.1 1.3 Definitions 3 1.4 Abbreviations and Symbols .8 1.5 General Applications9 1.5.1 Purpose of Circuit Breakers .9 1.5.2 Purpose of Molded Case Switches 9 1.6 Field Testing 9 SECTION 2 AVAILABLE TYPES OF MOLDED CASE CIRCUIT BREAKERS 2.1
17、 General Usage Categories11 2.1.1 Residential.11 2.1.2 Industrial/Commercial11 2.2 Tripping Means11 2.2.1 Thermal-Magnetic11 2.2.2 Hydraulic-magnetic11 2.2.3 Electronic (Solid-State)11 2.3 Specific Purpose Categories .12 2.3.1 Remote Control Circuit Breakers.12 2.3.2 Integrally-Fused Circuit Breaker
18、s12 2.3.3 Current-Limiting Circuit Breakers12 2.3.4 Switching Duty Circuit Breakers (SWD)12 2.3.5 Instantaneous Trip Only Circuit Breakers (Motor Circuit Protector or Circuit Interrupter)15 2.3.6 Heating, Air Conditioning, and Refrigeration Circuit Breakers (HACR)15 2.3.7 Marine Circuit Breakers.15
19、2.3.8 Naval Circuit Breakers.15 2.3.9 Mining Circuit Breakers .15 2.3.10 High Intensity Discharge Lighting Circuit Breakers (HID).15 2.3.11 Ground Fault Circuit Interrupter (GFCI) Circuit Breakers.15 2.3.12 Circuit Breaker with Equipment Ground Fault Protection.16 2.3.13 Classified Circuit Breakers1
20、6 2.3.14 Circuit Breakers with Secondary Surge Arrester16 2.3.15 Circuit Breakers with Transient Voltage Surge Suppressor.16 2.3.16 Circuit Breakers for Use With Uninterruptible Power Supplies 16 2.3.17 Arc-Fault Circuit Interrupter (AFCI) Circuit Breakers16 2.4 Other Applications16 2.5 Special Purp
21、ose Circuit Breakers16 SECTION 3 AVAILABLE VARIATIONS IN MOLDED CASE CIRCUIT BREAKERS 3.1 Constructional Variations.17 3.1.1 Circuit Breaker17 3.1.2 Frame17 3.1.3 Interchangeable Trip Unit .17 Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NAS
22、A Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- AB 3-2006 Page ii Copyright 2006 by the National Electrical Manufacturers Association. 3.1.4 Mechanism17 3.1.5 Pole.17 3.1.6 Accessories.17 3.2 Installatio
23、n Variations.18 3.2.1 External Conductor Connectors .18 3.2.2 Mounting Arrangements .18 3.3 Handle Orientation.19 3.4 Reverse Feed Circuit Breakers19 SECTION 4 MOLDED CASE CIRCUIT BREAKER RATINGS 4.1 Ampere Ratings.20 4.2 Voltage Ratings20 4.3 Interrupting Ratings21 4.4 Frequency21 4.5 Power Factor
24、Considerations 21 SECTION 5 SELECTION OF MOLDED CASE CIRCUIT BREAKERS 5.1 Preliminary Considerations23 5.1.1 Electrical Parameters23 5.1.2 User Requirements.23 5.1.3 Environmental Conditions.23 5.1.4 National Electrical Code .25 5.2 General Considerations for Molded Case Circuit Breaker Application2
25、6 5.2.1 General Requirements26 5.2.2 The Main Circuit Breaker26 5.2.3 The Feeder Circuit Breaker 26 5.2.4 The Branch Circuit Breaker 27 5.3 Load Requirement Considerations29 5.3.1 Continuous Duty, General Purpose Load.30 5.3.2 Lighting Loads.30 5.3.3 Heating, Air Conditioning, and Refrigeration Load
26、s .30 5.3.4 Motor Loads30 5.4 Specific Considerations for Molded Case Circuit Breaker Applications30 5.4.1 Conductor Selection .30 5.4.2 Terminations.31 5.4.3 Single-Phasing Protection 31 5.4.4 Time-Current Curves 31 5.4.5 Selective Coordination40 5.4.6 Series Application.43 5.4.7 Dynamic Impedance.
27、44 5.4.8 Capacitor Switching45 5.4.9 Motor Loads45 5.4.10 Nuclear Power Generating Station Equipment Qualifications46 5.5 Other Considerations for Specific Applications .46 5.5.1 Current-Limiting 46 5.5.2 Ground Fault Protection47 5.5.3 Molded Case Switches .49 5.5.4 Circuit Breakers Used on DC Syst
28、ems.49 5.5.5 Arcing Fault Protection (Circuit Breaker Type AFCI)50 Appendix A UL REQUIREMENTS FOR MOLDED CASE CIRCUIT BREAKERS.52 Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 0
29、8:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- AB 3-2006 Page iii Copyright 2006 by the National Electrical Manufacturers Association. Foreword This standards publication is intended to provide a basis of common understanding within the electrical community concern
30、ing the proper application of molded case circuit breakers. User needs have been considered throughout the development of this publication. Proposed or recommended revisions should be submitted to: Vice President, Technical Services National Electrical Manufacturers Association 1300 North 17th Stree
31、t, Suite 1752 Rosslyn, VA 22209 This standards publication was developed by the Molded Case Breaker Section of NEMA. Section approval of the standard does not necessarily imply that all section members voted for its approval or participated in its development. At the time it was approved, the Molded
32、 Case Breaker Section was composed of the following members: ABB Control, Inc.Wichita Falls, TX Eaton Electrical, Inc.Pittsburgh, PA GE Consumer in NEC Section 240.3 for equipment; and in NEC Section 210-21 for outlet devices. The interrupting rating of the branch circuit breaker should be equal to
33、or greater than the available fault current at the line side terminals in compliance with Section 110-9. The voltage and frequency ratings should be as required for the distribution system. Where applicable, the use of listed series tested molded case circuit breaker combinations should be considere
34、d. See 5.4.6. Ground fault protection may be required in accordance with NEC Section 240-13. If ground fault protection is provided on the main breaker, as defined in NEC Section 230-95, and is also included on the feeder breaker, the user should consider selecting a branch circuit breaker with suit
35、able integral ground fault protection or one that can operate in conjunction with separately mounted ground fault protective devices. For specific 15 and 20 ampere, 125 volt single phase receptacle circuits (see NEC Section 210-8, 305-6, and 550-8(b) for examples), and for items such as spas and hot
36、 tubs (see NEC Section 680-42), the user should select ground fault circuit interrupters (GFCI) equipped to provide personnel protection. Some applications require circuit breakers with ground fault protection for equipment such as electric deicing and snow-melting equipment as described in NEC Sect
37、ion 426.28. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- AB 3-2006 Page 28 Copyright 2006 by
38、the National Electrical Manufacturers Association. Figure 5-2 TYPICAL FEEDER CIRCUIT (LIGHTING LOAD AND SINGLE FIXED MOTOR LOAD) Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08
39、:24:14 MDTNo reproduction or networking permitted without license from IHS -,-,- AB 3-2006 Page 29 Copyright 2006 by the National Electrical Manufacturers Association. Figure 5-3 TYPICAL FEEDER CIRCUIT (COMBINATION AND MULTIPLE MOTOR LOADS) 5.3 LOAD REQUIREMENT CONSIDERATIONS A paramount considerati
40、on in selecting a circuit breaker is the load. Attention should be given to the type of equipment comprising the load, the normal continuous/non-continuous loading, the ON-OFF duty cycle, etc. There are load conditions that will call for the use of circuit breakers having time-current characteristic
41、s or other operating features, or both, fine-tuned for the particular application. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:24:14 MDTNo reproduction or networking permit
42、ted without license from IHS -,-,- AB 3-2006 Page 30 Copyright 2006 by the National Electrical Manufacturers Association. This list is not intended to cover all possible types of loads and combinations of loads, but the examples are cited to illustrate a few of the loading variations that should be
43、considered. If there are any questions about the proper breaker for an application, contact the manufacturer of the circuit breaker or equipment, or both. The following are examples of loads frequently encountered: NOTEPulsating loads, such as welders and phase controlled devices, require special co
44、nsiderations to prevent nuisance tripping. Consult the manufacturer. 5.3.1 Continuous Duty, General Purpose Load Selection of a standard circuit breaker should be determined by adding 100 percent of the non- continuous load plus 125 percent of the continuous load. For a circuit breaker rated to carr
45、y 100 percent of its rated current continuously, it is only necessary to add the non-continuous current plus the continuous current. Breakers rated for 100 percent continuous current applications are specifically marked. 5.3.2 Lighting Loads Refer to 2.3.4 and 2.3.10. 5.3.3 Heating, Air Conditioning
46、, and Refrigeration Loads Refer to 2.3.6. 5.3.4 Motor Loads Since motor loads are so prevalent in industrial and commercial applications, they are covered separately in 5.4.9. 5.4 SPECIFIC CONSIDERATIONS FOR MOLDED CASE CIRCUIT BREAKER APPLICATIONS 5.4.1 Conductor Selection The primary function of a
47、 molded case circuit breaker is to protect the circuit conductors. In order for the circuit breaker to provide this protection, the user should ensure that the breaker and conductors are properly matched. 5.4.1.1 Temperature Rating Of Conductor The National Electrical Code gives specific application
48、 rules to be followed for the temperature rating of conductors in Section 110-14(c). It should be noted that some circuit breakers rated 125 amperes or less are marked for use with conductors rated 60/75C and are suitable for use with conductors of either temperature rating. Wire rated for higher temperatures, such as 90C, may be used if the conductor size is determined by either the 60C or 75C size, as appropriate. In certain cases involving circuit breakers suitable f