The roster
Listed alphabetically. A row records that NEMA lists the company under this product section and links to NEMA’s own profile of it; it says nothing about which constructions, sizes or thermal classes the company makes. Ask the company for that.
| No. | Company | Also listed under | Where to check |
|---|---|---|---|
| 01 | Elektrisola Inc. | NEMA profile elektrisola.com | |
| 02 | Essex Solutions | NEMA profile essexsolutions.com | |
| 03 | Freeport-McMoRan | NEMA profile fcx.com | |
| 04 | Nacional de Conductores Eléctricos, S. A. de C. V. | NEMA profile | |
| 05 | SEA Wire and Cable, Inc. | NEMA profile sea-wire.com | |
| 06 | Virginia Insulated Products, Inc. | NEMA profile vipwire.com | |
| 07 | Xignux Corporativo | NEMA profile xignux.com |
Read this before using the list
The section covers a short list of members because magnet wire is a concentrated trade: enameling takes multi-pass ovens that run one wire size for days. Several large makers, and most makers outside North America, are not NEMA members and so are not on this sheet.
What makes magnet wire a separate trade
Building wire and hookup wire are insulated by extrusion: plastic is melted and pushed around the conductor in one pass. Magnet wire is insulated by enameling. Bare wire runs through a bath of liquid resin and then through a curing oven, again and again, building the film in layers until it reaches the specified thickness. The result is insulation thin enough that a coil is almost entirely metal, which is the whole point: the more copper that fits in a slot, the more efficient the motor.
That process is why a magnet wire mill makes little else, and why its product is described by properties no other wire has: how well the film survives being wound around a sharp corner, whether it can be soldered through without stripping, and how long it lasts at temperature.
The standard: NEMA MW 1000
In North America magnet wire is specified to ANSI/NEMA MW 1000, the standard written by the members of this
section. It assigns each construction an MW number, with a suffix for the conductor: -C for copper
and -A for aluminum. A callout therefore names four things at once.
| Part of the callout | What it fixes |
|---|---|
| MW type | The film chemistry and its thermal class: polyurethane, polyester, polyester-imide with a polyamide-imide overcoat, polyimide and others |
| Thermal class | The temperature the insulation is rated to run at, from 105 °C to 240 °C |
| Build | Film thickness: single, heavy, triple or quadruple |
| Size and shape | AWG for round wire; width and thickness for rectangular and square |
Outside North America the equivalent is the IEC 60317 series. The two systems describe similar products but are not interchangeable part for part, so a drawing should name one of them and its revision.
Checking a magnet wire maker
- Ask which MW types it makes, in which sizes. No mill runs the full table. The range a mill quotes is the range its ovens are set up for.
- Ask for the thermal endurance data behind the class. A thermal class is earned by test, and the report should name the test method and the film it was run on.
- If the wire goes into a UL-recognized insulation system, check the wire is in it. A motor or transformer insulation system lists the specific magnet wires it was evaluated with. Substituting another maker’s wire of the same MW type can take the finished part outside its recognition.
- Ask about put-up. Spool, reel or pail size and the tension the wire was wound at matter to a winding line as much as the film does.
The general method, and where each claim can be verified, is in Qualifying a wire manufacturer.