Insulation material heat resistance grade

The heat resistance grades of insulating materials commonly used in motors and transformers are divided into 7 grades: Y, A, E, B, F, H, and C: Y grade 90°C, A grade 105°C, E grade 120°C, B grade 130°C , Class F 155°C, Class H 180°C, Class C above 200°C.

The insulation material of each insulation level has a corresponding limit allowable operating temperature (the temperature of the hottest point of the motor or transformer winding). When the motor or transformer is running, the temperature of the hottest point of the winding must not exceed the specified value, otherwise it will cause accelerated aging of the insulating material and shorten the life of the motor or transformer; if the temperature exceeds the allowable value by a large amount, the insulation will be damaged, causing the motor or transformer to burn out.