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
MW 1000 is approved as an American National Standard through the NEMA MW 1000 Consensus Body accredited by the American National Standards Institute (ANSI). The
Consensus Body consists of magnet wire stakeholders including wire manufacturers, end users, and other general interest parties.
Join the NEMA MW 1000 Consensus Body. 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.
- top -
NEMA MW 1000 Highlights
NEMA MW 1000-2020
The following is a summary of changes from MW 1000-2018 that appear in the 2020 edition or are under development for a future edition:
- Revisions to Table 3, Dimensions for Self-Bonding Wire to expand the wire size range to include 8-13.5 AWG, providing the magnet wire industry a set of standard dimensional film and bond coat increases encompassing the entire range
of self-bonding wire sizes that industry currently manufactures
- Revision of requirements in clause 22.214.171.124 to remove the physical properties requirements for aluminum conductors
- Correction to clause 126.96.36.199, Application of Insulation, to indicate that insulation tape coverings, not fibrous coverings, shall be wrapped firmly, closely, evenly, and continuously around the wire
- Revisions to specifications for polyvinyl acetal film insulated wire to harmonize the Heat Shock requirements for consistency
- New specification for MW 16-A Polyimide (Thermal Class to be determined), with requirements to eventually be added for satellite applications
- Revisions to MW 33-A and MW 33-C specifications for paper tape covered rectangular magnet wire to better align with their counterpart round wire specifications
- Revisions to MW 102-A and MW 102-C to align their dielectric breakdown, springback and continuity requirements with the MW 35 series, which is the base specification for “Polyester (amide)(imide) Overcoated with Polyamideimide”
- New MW 88-C specification for polyvinyl acetal film insulated rectangular aluminum wire with self-bonding overcoat, with accompanying amendments to include minimum dimensional increases due to the bonding layer, and a lap shear bond strength test
- New MW 103-C specification for Polyester Overcoated with Polyamideimide with Self-Bonding Overcoat
- New MW 122-C specification for Polyamideimide with Self-Bonding Overcoat;
Part 3—Test Methods
- Revision to the circumferential cut method for determining adherence and flexibility properties, to include photos of a typical fixture and specimen preparation
- Revisions to Appendix H for Fully Insulated Wire, to align with amendments to IEC 60851-5
Look for a new 2023 edition of NEMA MW 1000 to be published around summer.
- top -
NEMA Members that Manufacture Magnet Wire
For 2023, the following magnet wire manufacturers are NEMA Members:
- top -
- top -
How to Use MW 1000
In the Table of Contents, 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.
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. 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.
Part 1 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.
Part 2 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 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 provides a cross-reference between MW 1000 test procedures and those published by the American Society for Testing and Materials (ASTM International)
and the International Electrotechnical Commission (IEC).
Appendix B provides 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 provides a cross-reference of MW specifications with those published by the
Appendix D provides the formulas used for determining dimensional requirements, minimum dielectric breakdown voltage, and cross-sectional areas and conductor resistance
Appendix E 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.
Appendix F provides important information on selected refrigerants that could be used as alternatives to monochlorodifluoromethane (refrigerant R-22), including chemical compositions, boiling points, critical pressures and critical
Appendix G provides industry recommended winding tensions for de-reeling of magnet wire onto end user winding equipment.
Appendix H defines the requirements and test procedures for zero-defect fully insulated magnet wire (FIW).
Appendix I provides a recommended method for repeated scrape resistance, commonly specified by magnet wire end users.
- top -
Comparison to International Standards
MW 1000 is a complete volume containing all general requirements, specifications and test methods for magnet wire in a single document for convenience. IEC specifications and test methods on the other hand, are each published in separate documents. NEMA
specifications and test methods differ from those published by the International Electrotechnical Commission (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: Annex 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: NEMA immersion time requirements for larger wires are more stringent than those specified in IEC specifications. The IEC and NEMA methods for determining the solderability of a given wire construction are technically
equivalent and both Standards recognize the use of lead-free solder alloys upon supplier/customer agreement.
Continuity Requirements: The NEMA continuity requirements for single build (Grade 1) wire more closely reflect the capabilities of present-day manufacturing equipment than do IEC requirements. However, closer harmony between NEMA and
IEC requirements for heavy and triple build (Grade 2 and 3) constructions was achieved upon publication of IEC 60317-0-1:2013, and in the present maintenance work program for IEC 60317-0-1, the requirements for Grade 2 and Grade 3 are proposed
to be fully harmonized.
Test Procedures: There is an ongoing effort to harmonize IEC and NEMA test procedures. The following summarizes notable differences in these procedures:
Resistance to Refrigerants: Both the NEMA and IEC procedures specify the use of monochlorodifluoromethane (refrigerant R22). Since R22 is no longer permitted in new equipment, investigation is ongoing for identifying suitable
alternative refrigerants commonly used in newer refrigeration equipment, to test magnet wire for hermetic applications. The challenge in transitioning to alternative refrigerants is establishing which refrigerants lead to meaningful test
results. A new consideration is that refrigerant oils used in today’s compressors can be more aggressive on wire insulation than refrigerants. IEC 60335-2-34 contains a test for determining wire insulation compatibility with refrigerant and
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.
IEC TC 55 decided not to specify pre-stretching that would result in total elongations equivalent to those in MW 1000.
Dielectric Breakdown: MW 1000 has adopted a shot electrode methodology for determining breakdown of rectangular and large round wires, based on IEC 60851-5. Both MW 1000 and IEC 60851-5 recognize the cylinder method for round enameled
wires. MW 1000 is being revised to specify the cylinder method for the same wire size range as that of IEC 60851-5.
Thermal Endurance: The method for determining the thermal classification of magnet wire is essentially the same between IEC and NEMA Standards. The Standards used IEC 60172 and ASTM D2307, respectively outline a multi-temperature thermal
cycling aging test procedure with a dielectric diagnostic test after each cycle on round wire test samples. The IEC 60172 Standard also includes a method for evaluating rectangular wire test samples.
Thermoplastic Flow (Cut Through): IEC 60851-6 specifies 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
Bond Strength: The IEC and NEMA helical bond peel test procedures are essentially equivalent.
- top -
End User Information
The following information can be downloaded free of charge:
Download and listen to the following:
Companion NEMA Publications:
IEC Test Method Standards:
- top -
here if you have any questions about this page, NEMA or magnet wire Standards.