What are magnet wire insulations?
The term magnet wire includes an
extremely broad range of sizes of both round and rectangular
conductors used in electrical apparatus. Common round-wire sizes for
copper are AWG No. 42 (0.0025 in) to AWG No. 8 (0.1285 in).
A significant volume of aluminum magnet
wire is produced in the size range of AWG No. 4 to AWG No. 26.
Ultrafine sizes of round wire, used in very small devices, range as
low as AWG No. 60 for copper and AWG No. 52 for aluminum.
Approximately 20 different “enamels”
are used commercially at present in insulating magnet wire.
Magnet wire insulations are high in
electrical, physical, and thermal performance and best in space
factor. The most widely used polymers for film-insulated magnet wire
are based on polyvinyl acetals, polyesters, polyamideimides,
polyimides, polyamides, and polyurethanes.
Many magnet wire constructions use
different layers of these polymer types to achieve the best
combination of properties. The most commonly used magnet wire is NEMA
MW-35C, Class 200,\ which is constructed with a polyester basecoat
and a polyamideimide topcoat.
Polyurethanes are employed where ease
of solderability without solvent or mechanical striping is required.
The thermal class of polyurethane insulations has been increased up
to Class 155 and even Class 180.
Magnet wire products also are produced
with fabric layers (fiberglass or Dacron-fiberglass) served over bare
or conventional film-insulated magnet wire. Self-bonding magnet wire
is produced with a thermoplastic cement as the outer layer, which can
be heat-activated to bond the wires together.
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