The thermal class is determined on the nameplate. These are aramid and polyester based and obtain films and laminates which are used at the following points, between the coil and the groove, which is the groove bottom film, to insulate the steel sheet package from the coil of enameled yarn; between the phases, to electrically isolate the phase from one another; closure of the stator slot to electrically isolate the coil found at the top of the stator slot and also to operate mechanically so as to keep the wires within the groove.
Currently, the enamel used in the wires ensures the mechanical property ensured by the outer layer of the enamel which resists abrasion forces during the insertion thereof into the stator grooves. The inner enamel layer ensures high dielectric strength to the assembly and attaches 200 degree grade to the wire. This wire is used on all class B, F and H engines. On smoke extraction engines, the wire is specific for very high temperatures. Insulating films and laminates have the function of thermal and electrically insulated parts of the motor coil.