Magnet wire

It is used in the construction of transformers, inductors, motors, generators, speakers, headphones, hard disk head actuators, electromagnets, electric guitar pickups, and other applications that require tight coils of insulated wire.

[2] Most often, magnet wire is composed of fully annealed, electrolytically refined copper to allow closer winding when making electromagnetic coils.

[3] High-purity oxygen-free copper grades are used for high-temperature applications in reducing atmospheres or in motors or generators cooled by hydrogen gas.

Magnet wire insulating films use (in order of increasing temperature range) polyvinyl formal (Formvar), polyurethane, polyamide, polyester, polyester-polyimide, polyamide-polyimide (or amide-imide), and polyimide.

Thicker magnet wire is often square, rectangular or hexagonal (with rounded corners) in cross section, packing more efficiently and having greater structural stability and thermal conductivity across adjacent turns.

Magnet wire is used in windings of electric motors, transformers, inductors, generators, headphones, loudspeaker coils, hard drive head positioners, electromagnets, and other devices.

Electric motors are found in numerous diverse applications, such as fans, blowers, pumps, machines, household appliances, power tools, and disk drives.

For a given size of motor frame, high conductivity material reduces the energy loss due to coil resistance.

For example, to reduce load losses in continuous-use induction-type motors above 1 horsepower, manufacturers invariably use copper as the conducting material in windings.

To improve the electrical energy efficiency of induction-type motors, load loss can be reduced by increasing the cross section of copper coils.

Early developments in motor efficiency focused on reducing electrical losses by increasing the packing weight of stator windings.

[8] Transformer windings are normally made from copper but aluminium is a suitable competitor where weight and first cost are decisive factors.

[3] In North America, aluminium is the predominant choice of winding material for low-voltage, dry-type transformers larger than 15 kilovolt-amperes (kVA).

[9] Copper used for the manufacture of transformer windings is in the form of wire for small products and strip for larger equipment.

To obtain equal ratings in aluminium transformers, a 66% larger cross-sectional area is required than for copper conductors.