Temperature rise in electric motors

The power loss in an electric machine (see Drive) leads to the build-up of heat in active parts such as the winding and core packs (also see Motor protection). Increases in the winding temperature not only reduce the lifetime of the insulation, but can also cause the electric machine to fail without warning if heat reaches dangerous levels.

Impermissible temperature rises can be the result of improper cooling or an overload, which increases the current requirement of electric motors.

The insulating material used determines to what extent heat may build up in the motor. IEC 60034-1 covers the thermal resistance of insulating materials, thermal classes, and methods for determining overtemperature.