Electromagnetic wire or enameled wire, also known as winding wire, is a type of copper (Cu) or aluminum (Al) wire coated with a very thin insulating layer. It is used in the manufacture of transformers, inductors, motors, generators, speakers, hard disk head actuators, electromagnets, electric guitar pickups, and other applications that require tightly insulated coils. The magnet or enameled wire is actually coated with enamel or glass enamel. Modern electromagnetic wires typically use one to four layers (in the case of four-layer thin-film type wires) of polymer film insulation, usually with two different components, to provide a tough, continuous insulation. Electromagnetic wire insulating film used (in order of increasing temperature range) polyethylene formaldehyde (Formvar), polyurethane, polyamide, polyester, polyester polyimide, polyamide polyimide (or amide imide) and polyimide. Polyimide insulated electromagnetic wires are capable of operating at temperatures up to 240 °C.
In most cases, to make magnet or enameled wire, the basic process begins by extruding the wire to the desired size, and then applying liquid paint. The wire then goes into the oven and the enamel is cured. Insulation is usually added in multiple channels, and the wires go in and out of the same oven in series in a continuous process until the desired insulation is obtained. The magnet or enameled wire consists of fully annealed, electrolytically refined copper or aluminum to allow tighter windings when making electromagnetic coils. High purity oxygen free bronze is used for high temperature applications in reducing atmospheres or hydrogen-cooled motors or generators.