Welcome to the home of NEMA MW 1000, Magnet Wire, a standards publication of the National Electrical Manufacturers Association (NEMA). This site tells you about MW 1000, how to use it, and gives updates on revisions as they are approved and published.

About NEMA MW 1000

NEMA members that manufacture magnet wire

NEMA contacts

How to Use

Get your copy of ANSI/NEMA MW 1000-2008 today!

Comparisons to international standards

End user information

Revisions to MW 1000-2008

About NEMA MW 1000

MW 1000 is the world's premier standard for general requirements, product specifications and test procedures for the manufacture and packaging of magnet wire.  The first edition was published in 1965.  MW 1000 is a dynamic document that is continually developed and maintained by the NEMA Magnet Wire Section Technical Committee, to ensure that specifications and test procedures reflect evolving magnet wire end user requirements and state-of-the-art magnet wire manufacturing technologies.

MW 1000 is designed to present, in concise and convenient form, all existing NEMA Standards for magnet wire, including standards for round, rectangular, and square film insulated and/or fibrous covered copper and aluminum magnet wire for use in electrical apparatus.  MW 1000 contains the definitions, type designations, dimensions, constructions, performance, and test methods for magnet wire generally used in the winding of coils for electrical apparatus.

MW 1000 is approved as an American National Standard through an accredited canvass of the American National Standards Institute (ANSI), and is endorsed by Electro-Federation Canada (EFC) for use in Canada and by La Asociación de Normalización y Certificación del Sector Eléctrico (Association of Standardization and Certification of the Electrical Sector (ANCE) for use in Mexico.

Join the ANSI Canvass for NEMA MW 1000.  It's free!  Inquire here.

What is magnet wire?

Magnet wire (also known internationally as winding wire) is an insulated electrical conductor, usually copper or aluminum that when wound into a coil and energized, creates a useful electromagnetic field. Without magnet wire, electricity is essentially useless. Around 90% of all electrical energy requires modification using magnet wire to be of any use.

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NEMA members that manufacture magnet wire

For 2009, the following magnet wire manufacturers are NEMA members:

Condumex–México D.F., México

Bridgeport Insulated Wire Company–Bridgeport, CT

Elektrisola, Inc.–Boscawen, NH

Essex Group, Inc.–Fort Wayne, IN

Magnekon–San Nicolás, NL México

MWS Wire Industries–Westlake Village, CA

Rea Magnet Wire Company–Fort Wayne, IN

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NEMA Contacts

How to Use Your Hard Copy of MW 1000

The white pages make up the Table of Contents for Parts 1, 2, and 3 and the Appendices. The Part 2 specifications are first listed in order according to MW specification number, then by Thermal Class for easy reference to a particular type of magnet wire.

Part 1 (blue, if in print) deals with general information common to all types of magnet wire found in Part 2, including reference documents, definitions, general material requirements, manufacturing information, test conditions and parameters, thermal class information and ordering information.  Part 1 also includes dimensions in both AWG and equivalent metric sizes (in mm) for bare wire, minimum insulation increase, and overall dimensions for all MW specifications in Part 2.  The only exception to this is MW 16-C, a standalone specification that includes dimensional and other requirements particular to polyimide constructions.

Part 2 (yellow, if in print) has all of the NEMA specifications for the particular types of magnet wire listed in the Table of Contents, identified and ordered by “MW” number.  The MW number is followed by a “-C” or “-A” to identify the conductor type, copper or aluminum.  These specifications provide all of the performance requirements for magnet wire for various types of coatings and/or coverings. Insofar as possible, the product specifications are complete on one sheet since they are arranged to include only one insulation or covering per sheet. The title identifies the product, for example, MW 15-C, Polyvinyl Acetal Round Copper Magnet Wire, while MW 15-A covers the aluminum version of the same generic product.

Part 3 (green, if in print) contains the test procedures to be followed and the corresponding tables of specific test values to be attained in determining compliance with the requirements given in Part 2.  The requirements are consolidated with the test procedures and testing parameters for a given property. The Table of Contents provides a useful index of the main test paragraphs, beginning on page viii.

Appendix A (tan, if in print) provides a cross-reference between MW 1000 test procedures and those published by the American Society for Testing and Materials (ASTM International).

Appendix B (tan, if in print) consists of definitions, requirements, and recommended test procedures for reusable magnet wire packaging, standardized dimensions for spools and reels, and standard formatting for the labeling of magnet wire products.

Appendix C (tan, if in print) provides a cross-reference of MW specifications with those published by the International Electrotechnical Commission (IEC), and the J-W-1177 series of Federal Specifications canceled in 1995.

Appendix D (tan, if in print) provides the formulas used for determining dimensional requirements, minimum dielectric breakdown voltage, and cross-sectional areas and conductor resistance

Appendix E New for Rev. 1! (tan, if in print) defines the dimensional criteria for ranges of sizes of rectangular bare, film insulated, and fibrous covered magnet wire.  These tables provide the general rules and guidelines for various rectangular magnet wire products that are not standard as defined in Part 1.  For convenience, cross-references to the corresponding tables in Part 1 are provided.

To properly use MW 1000, first, review Part 1 for general information, then locate the specification in Part 2 for the particular type of insulation and conductor of interest.  Part 2 is arranged in MW number order as shown beginning on page ii.  The dimensions for each Part 2 MW type are provided in Part 1 beginning with Table 1-1. The specification in Part 2 will indicate the performance requirements to be met and references the test procedures and corresponding test values to be attained in Part 3.

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Get your copy of ANSI/NEMA MW 1000-2008 today!

MW 1000-2008 is available through IHS/Global Engineering Documents.  Click here to order.

Amendments

The following amendments to MW 1000-2008 have been approved by the NEMA Magnet Wire Section and, in combination, are subject for approval as an American National Standard:

Clause 1.3, Definitions - addition of the term full rounded edge

Rationale: In the process of developing new standard dimensions for bare insulated rectangular wire in Table 1-8, it was determined that the term full rounded edge should be defined to ensure precision in its application. A drawing is included to make the standard more user friendly.

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Clause 1.3, Definitions - addition of terms for "rectangular wire" and "square wire"

Rationale: to provide clarification to users of the standard, the differences between the dimensional tables in Part 1 for rectangular wire and for square wire

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Revised Table 1-8, Dimensions, Radii and Cross-Sectional Area for Standard Rectangular Bare Wire

Rationale: to encourage the use of standard dimensions and minimum increases for rectangular wire
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Amendment to Part 2 introduction

Rationale: to clarify that the wire size ranges in the DIMENSIONS section of each specification in Part 2 determines the range of wire sizes to be tested to Part 3 test procedures
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Reorganization of MW 16-C Polyimide Round Film Insulated Wire, Class 240

Rationale: consolidates the dimensional and performance requirements of the four insulation builds, and to assign revised and unique Dielectric Breakdown and Scrape Resistance requirements for MW 16-C Quad to the appropriate sections of Part 3

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Amendments to Table 3.3.1

Rationale: to assign half-AWG wire sizes to align with the addition of half-AWG wire sizing in Table 1-1, and to encompass the entire range of copper and aluminum wire sizes in Part 2 specifications.

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Table 3.4.1, Elongation, and related Part 2 specifications

Rationale: to accurately and consistently reflect the Part 2 elongation requirements for all rectangular wires having a thickness of <0.049 in. from 32% to 30%, and correspondingly, to replace these Part 2 elongation requirements with a reference to Table 3.4.1.

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Clause 3.5, Heat Shock

Rationale: to clarify that the procedure applies to both round and rectangular wire

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Clause 3.9.2, High Voltage Continuity

Rationale: to specify calibration of test equipment based on fault resistance and to provide specifications on carbon brush electrodes to be used as part of the test apparatus

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Clause 3.13, Solderability

Rationale: to note the availability of alternative lead-free solder alloys, which are agreed upon between customer and supplier

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Clause 3.54, Transformer Oil Resistance and Hydrolytic Stability

Rationale: to permit testing of a range of wire sizes, not just 18 AWG, to provide guidance on the number, length and/or weight of specimens, and to specify the materials to be used for the test.

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Clause 3.57, Bond

Rationale: to reorganize the procedures to make it clear as to how the test is to be conducted in each possible condition. In addition, specifications for self-bonding wire in Part 2 are modified editorially for clearer reference to the appropriate type of test procedure.

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Part 3, Tables of test requirements

Rationale: to assign half-AWG wire sizes to clarify and document the appropriate break where a different test method is used.

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New Appendix E

Rationale: to relocate the dimensions from former Tables 1-13 through 1-18 into a new informative reference section.  These dimensions are considered to be non-standard relative to the amended Table 1-8.

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Specifications MW 47-C and MW 48-C

Rationale: to require MW 47-C wire to have a silicone varnish, the same tracer requirements as in MW 48-C, and Springback requirements up to 4 AWG, not 4/0 AWG. Both MW 47-C and MW 48-C should adopt the MW 43-C and 44-C requirements for treatment with a modified silicone insulating varnish or silicone compound for a tough outer finish.  All changes are editorial in nature because they restore the requirements that were published in MW 1000-1997.

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Comparison to international standards

NEMA specifications and test methods differ from those published by the IEC. The following is a general summary of these differences:

Dimensions: NEMA dimensional requirements apply American Wire Gauge (AWG) wire sizing, while dimensional requirements in IEC standards apply metric sizing in mm.  Therefore the requirements are not exactly the same, but some overlap occurs between the standards.  The IEC and NEMA methods for determining dimensions are technically equivalent.

Available Specifications: Appendix C of NEMA MW 1000 cross-references NEMA and IEC magnet wire specifications.  Not all NEMA specifications have a corresponding IEC specification number and vice versa.

Solderability Requirements: Although NEMA has adopted the IEC-based approach to establishing solder bath immersion times for some of the more popular wire specifications, the NEMA immersion times for larger wires are more stringent than those specified in IEC.  Efforts to bring these requirements into harmony could begin in 2012.  The IEC and NEMA methods for determining solderability are technically equivalent.

Continuity Requirements: The NEMA continuity requirements for single build wire more closely reflect the capabilities of present day manufacturing equipment than do IEC requirements.

Test Procedures: There is an ongoing effort to harmonize IEC, NEMA and Japanese Industrial Standard (JIS) test procedures.  The following summarizes notable differences in these procedures:

Heat Shock: Differences exist between the test specimen preparation procedures,namely the degree of pre-elongation of wire specimens and the diameter of the test mandrels used for wrapping wire specimens.  The NEMA-specified total elongation of wire specimens (pre-stretch + mandrel wrapping) is more stringent than IEC, which specifies only a mandrel wrap.

Although IEC TC 55 Working Group 1 has decided not to specify pre-stretching in order to obtain total elongations equivalent to those in NEMA MW 1000, a table of such pre-stretching percentages will be prepared for informational purposes, should manufacturers of IEC-specified wire wish to comply.

Dielectric Breakdown (for rectangular wire): MW 1000 does not recognize the IEC 60851-5 shot box methodology for determining breakdown of rectangular and large round wires.

Thermoplastic Flow (Cut Through): The next edition of IEC 60851-6, containing tests for thermal properties, will adopt a single-point method of evaluation.  This could be adopted in MW 1000 in the future as a routine test, however for now MW 1000 recognizes a rising-point method as a qualification test.

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End user information

This section contains information applicable to the magnet wire end user

Table of current and obsolete NEMA magnet wire specification sheets

Table of recommended winding wire tensions

Companion NEMA publications:

MW 750, Dynamic Coefficient of Friction of Film Insulated Magnet Wire (New 2009 edition now available)
MW 765, Reclaiming of Magnet Wire Packaging
MW 785, Simulated Insertion Force Test for Film Insulated Magnet Wire

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