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1、 NEMA 250 NEMA 250 ENCLOSURES FOR ELECTRICAL EQUIPMENT (1000 VOLTS MAXIMUM) NEMA Standards Publication 250-2008 Enclosures for Electrical Equipment (1000 Volts Maximum) Published by National Electrical Manufacturers Association 1300 N. 17th Street, Suite 1752 Rosslyn, VA 22209 www.nema.org Copyright
2、 2008 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.
3、NOTICE AND DISCLAIMER The information in this publication was considered technically 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 partic
4、ipating in the development of this document. NEMA standards and guideline publications, 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
5、interest in the topic covered by this publication. While NEMA administers the 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 t
6、he soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication
7、, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, expressed or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your part
8、icular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by 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
9、 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 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 r
10、easonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other 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
11、 police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety-related information in this document shall not be
12、attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. 250-2008 Page i Copyright 2008 by the National Electrical Manufacturers Association. TABLE OF CONTENTS 1 GENERAL .1 1.1 Scope.1 1.2 References 1 1.3 Definitions3 2 ENCLOSURE TYPES, FEATURES, AND APPLICA
13、TIONS5 2.1 General5 2.2 Specific Types .5 3 CONSTRUCTION9 3.1 General9 3.2 Units of Measurement .9 3.3 MaterialsGeneral9 3.4 MaterialsPolymeric.9 3.5 Corrosion ProtectionGeneral.9 3.5.1 Indoor Corrosion Protection .10 3.5.2 Outdoor Corrosion Protection.10 3.5.3 Annealed Coating.10 3.5.4 Bends and Fo
14、rms on Zinc Coatings.11 3.5.5 Hot Dipped Galvanized Damage11 3.5.6 Cast Iron.11 3.5.7 Corrosion Protection for Type 3X, 3RX, 3SX, 4X and 6P Enclosures.11 3.6 Openings .11 3.6.1 Equipment Openings11 3.6.2 Ventilation.11 3.6.3 Drainage Openings 12 3.7 Mounting12 3.8 Conduit Connection.12 3.9 Hubs and
15、Fittings.12 3.10 Knockouts12 3.11 External Operating Mechanisms.13 3.12 Access to Interior.13 3.13 Closing Hardware13 3.14 Gaskets13 3.15 Observation Windows14 4 MARKING15 4.1 Type Designations.15 4.2 Supplemental Markings.15 4.3 Location of Markings .15 4.4 Enclosure Orientation15 4.5 Conduit Hubs
16、and Closure Plates.15 4.6 Equipment Openings.16 4.7 Drainage Openings16 5 DESIGN TESTS.17 5.1 General17 5.2 Test For Protection against Access to Hazardous Parts 22 5.2.1 Non-ventilated Enclosures Test Method22 5.2.2 Ventilated Enclosures Test Method .22 5.2.3 Evaluation.22 5.3 Test for Protection a
17、gainst Ingress of Water (Dripping and Light Splashing).22 5.3.1 Method A 22 5.3.2 Method B 22 5.3.3 Evaluation.23 5.4 Test for Protection against Ingress of Water (Rain)23 250-2008 Page ii Copyright 2008 by the National Electrical Manufacturers Association. 5.4.1 Method23 5.4.2 Evaluation.23 5.5 Tes
18、t for Protection against Ingress of Solid Foreign Objects (Settling Airborne Dust, Lint, Fibers, And Flyings).26 5.5.1 Outdoor Dust Test26 5.5.2 Indoor Dust Tests.26 5.6 External Icing Test.28 5.6.1 Test Method28 5.6.2 Evaluation.28 5.7 Test for Protection against Ingress of Water (Hosedown)29 5.7.1
19、 Test Method29 5.7.2 Evaluation.29 5.8 Indoor Corrosion Protection (Rust-Resistance Test (24-Hour Salt Spray Test)29 5.8.1 Test Equipment 29 5.8.2 Salt Solution .29 5.8.3 Air Supply .30 5.8.4 Temperature.30 5.8.5 Test Procedure.30 5.8.6 Evaluation.30 5.9 Outdoor Corrosion Protection30 5.9.1 600-Hour
20、 Salt Spray Test.30 5.9.2 Evaluation.30 5.9.3 1200-Hour Moist Carbon DioxideSulfur DioxideAir Test.30 5.10 Corrosion ProtectionType 3X, 3RX, 3SX, 4X Or 6P Enclosures.30 5.10.1 Evaluation.31 5.11 Test for Protection against Ingress of Water (Temporary Submersion) .31 5.11.1 Test Method31 5.11.2 Evalu
21、ation.31 5.12 Test for Protection against Ingress of Water (Prolonged Submersion) 31 5.12.1 Alternate Tests .31 5.13 Oil Exclusion Test32 5.13.1 Test Method32 5.13.2 Evaluation.32 5.14 Gasket Tests .32 5.14.1 Aging Test 32 5.14.2 Evaluation.32 5.14.3 Oil immersion test.33 Annex A Comparison Between
22、NEMA Enclosure Type Numbers and ANSI/IEC Enclosure Classification Designations.34 A.1 GENERAL34 Annex B Descriptions, Applications, Features, and Test Criteria of Enclosures for Hazardous (Classified) Locations.37 B.1 GENERAL37 B.2 SPECIFIC TYPES .37 B.2.1 Enclosure Features.38 B.2.2 Enclosure Test
23、Criteria .39 Tables 2-1 Comparison of Specific Applications of Enclosures for Indoor Nonhazardous (Non-Classified) Locations5 2-2 Comparison of Specific Applications of Enclosures for Indoor and Outdoor Nonhazardous (Non-Classified) Locations6 3-1 Knockout Dimensions13 250-2008 Page iii Copyright 20
24、08 by the National Electrical Manufacturers Association. 5-1A Degrees of Protection against Access to Hazardous Parts18 5-1B Degrees of Protection against Solid Foreign Objects .19 5-1C Degrees of Protection against Water 20 5-1D Additional Protection21 5-2 Tightening Torque .23 Figures 5-1 Rain-tes
25、t Spray-head Piping .24 5-2 Rain-test Spray Head25 -,-,- 250-2008 Page iv Copyright 2008 by the National Electrical Manufacturers Association. FOREWORD This Standards Publication covers the classification and description of enclosures for electrical equipment. Enclosures for rotating apparatus have
26、not been included. The primary purpose of this publication is to permit a potential user to determine: 1. The type of enclosure appropriate for the application. 2. The features the enclosure is expected to have. 3. The tests applied to the enclosure to demonstrate its conformance to the description.
27、 These standards are used by the electrical industry to provide guidelines for the manufacture and proper application of enclosures and to promote the benefits of repetitive manufacturing and widespread enclosure availability. Each type of enclosure is described in general and functional terms where
28、 practicable, and omits reference to structural details and specific applications except where they are essential to the identification of the enclosure type. For such structural details and specific applications, see the appropriate NEMA product standards publication. Individual product standards p
29、ublications incorporating enclosure construction unique to the product design may reflect the type of designations contained herein provided the design tests for such construction equal or exceed the requirements of these Standards Publication. User needs have been considered throughout the developm
30、ent of this publication. Proposed or recommended revisions should be submitted to: Vice President, Technical Services National Electrical Manufacturers Association 1300 N. 17th Street Suite 1752 Rosslyn, VA 22209 Publication 250-2008 revises and supersedes Publication 250-2003. This Standards Public
31、ation was developed by the NEMA Enclosure Section of the National Electrical Manufacturers Association. 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 Enclosure Section w
32、as composed of the following members: Allied Moulded Products, Inc. Bryan, OH Boltswitch, Inc. Crystal Lake, IL Carlon, Lamson and 2. Enclosures for indoor or outdoor locations, Types 3, 3X, 3R, 3RX, 3S, 3SX, 4, 4X, 6, and 6P. b. Hazardous (classified) locations 1. Enclosures for indoor locations, T
33、ypes 7 and 9; 2. Enclosures for indoor or outdoor locations, Type 8; and 3. Enclosures for mining applications, Type 10. Requirements for enclosures for non-hazardous (non-classified) locations are contained in the body of the standard. Requirements for enclosures for hazardous (classified) location
34、s are contained in Annex A of the standard. This standard covers the requirements to provide protection to the enclosed equipment against specific environmental conditions. This standard supplements requirements for enclosures that are contained in the individual product standards. This standard doe
35、s not cover the requirements for protection of devices against conditions such as condensation, icing, corrosion, or contamination which may occur within the enclosure or which may enter via conduit or unsealed openings. A product that contains features, characteristics, components, materials, or sy
36、stems new or different from those in use when the standard was developed, and that involves a risk of fire, electric shock, or injury to persons shall be evaluated using the appropriate additional component and end-product requirements as determined necessary to maintain the level of safety for the
37、user of the product as originally anticipated by the intent of this standard. 1.2 REFERENCES The following documents contain provisions, which through reference in this text, constitute provisions of this Standards Publication. By reference herein these publications are adopted, in whole or in part
38、as indicated, in this publication. American National Standards Institute (ANSI) 11 West 42nd Street New York, NY 10036 American Society of Mechanical Engineers (ASME) 345 East 47th Street New York, NY 10017-2392 250-2008 Page 2 Copyright 2008 by the National Electrical Manufacturers Association. ANS
39、I/ASME B1.20.1 Pipe Threads, General Purpose (In) ANSI/ASME B94.11M Twist Drills ASTM International 100 Barr Harbor Drive West Conshohocken, PA 19428 ASTM A 653/A 653M Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process AST
40、M B117 Standard Practice for Operating Salt Spray(Fog) Apparatus ASTM B555 Standard Guide for Measurement of Electrodeposited Metallic Coating Thickness by the Dropping Test ASTM D471 Rubber Property-Effect of Liquids ASTM D5964 Standard Practice for Rubber IRM 902 and IRM 903 Replacement Oils for A
41、STM No. 2 and ASTM No. 3 Oils. International Electrotechnical Commission (IEC) 3, rue de Varemb P.O. Box 131 1211 Geneva 20 Switzerland ANSI/IEC 60529 Degrees of protection provided by enclosures (IP Code) The Instrumentation, Systems, and Automation Society (ISA) 67 Alexander Drive Research Triangl
42、e Park, NC 27709 USA ANSI/ISA 12.12.01 Nonincentive Electrical Equipment for use in Class I and II, Division 2, and Class III, Divisions 1 and 2 Hazardous (Classified) locations. National Fire Protection Association (NFPA) 1 Batterymarch Park PO Box 9101 Quincy, MA 02269 ANSI/NFPA 70 National Electr
43、ical Code ANSI/NFPA 496 Purged and Pressurized Enclosures for Electrical Equipment ANSI/NFPA 497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. ANSI/NFPA 499 Classification of Combustible Dusts and
44、 of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas Superintendent of Documents US Government Printing Office Washington, DC 20402 30 CFR Part 18 Electric Motor-Driven Mine Equipment and Accessories Underwriters Laboratories Inc. (UL) 333 Pfingsten Road Northb
45、rook, IL 60062 ANSI/UL 50 Enclosures for Electrical Equipment Non-Environmental Considerations 250-2008 Page 3 Copyright 2008 by the National Electrical Manufacturers Association. ANSI/UL 50E Enclosures for Electrical Equipment Environmental Considerations ANSI/UL 94 Tests for Flammability of Plasti
46、cs Materials for Parts in Devices and Appliances ANSI/UL 157 Gaskets and Seals ANSI/UL 514B Conduit, Tubing, Cable Fittings ANSI/UL 698 Industrial Control Equipment for Use in Hazardous (Classified) Locations ANSI/UL 746C Polymeric Materials Use in Electrical Equipment Evaluations ANSI/UL 877 Circui
47、t Breakers and Circuit-Breaker Enclosures for Use in Hazardous (Classified) Locations ANSI/UL 886 Outlet Boxes and Fittings for Use in Hazardous (Classified) Locations ANSI/UL 894 Switches for Use in Hazardous (Classified) Locations ANSI/UL 1203 Explosion-Proof and Dust-Ignition-Proof Electrical Equ
48、ipment for Use in Hazardous (Classified) Locations ANSI/UL 1332 Organic Coatings for Steel Enclosures for Outdoor-Use Electrical Equipment 1.3 DEFINITIONS The following definitions are applicable in this standard. cover: An unhinged portion of an enclosure that covers an opening. degree of protectio
49、n: The extent of protection provided by an enclosure against access to hazardous parts, against ingress of foreign solid objects and/or against ingress of water and verified by standardized test methods. design tests: Tests to demonstrate performance of a product designed to applicable standards. NOTEDesign tests are not intended to be production tests.) door: A hinged portion of an enclosure that covers an opening. enclosure: A surrounding case constructed to provi
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