In electric motors the insulation of the stator winding is responsible for preventing the passage of electric current from the conducting wires to the stator plating.

It protects the winding of erosive agents from the environment and helps in conducting the heat generated by the losses to the outside. The MIT being a robust machine is dimensioned so that its useful life is determined by the longevity of the stator winding insulation.

The life of the insulation is reduced due mainly to the temperature, but also due to the action of humidity and vibration, until it can not withstand the applied voltage and cause a short circuit.

An increase of 10ºC above the thermal class limit of the insulation can reduce the half-life of the motor coxreels 1125. The total insulation of the winding involves a combination of insulation from the groove where the coils are inserted, the winding impregnation resin, the enamel on each winding wire and the insulation between phases.

The standard establishes the classes of insulation, each with its temperature limit, that is, by the higher temperature that the insulation system can withstand without affecting its useful life.