In most motor applications, various types of transformer insulation are often used. We can also know the overall insulation rating of the motor by the heat resistance rating of the insulated motor used. However, we must also note that since the motor is mainly for short-term work, the maximum allowable temperature of the insulating material is also increased according to the service life of the motor. In general, the insulation of the motor is divided into six grades: A, E, B, F, H, and C. The highest heat resistant temperatures of different grades of motors are also different.