The thermistor installed in the motor is generally installed close to the motor winding, in order to monitor the temperature rise of the motor winding. Generally, the negative temperature coefficient of the thermistor is used, when the winding temperature rises due to the motor overload, the thermistor resistance value will decrease, and when the resistance value drops to a certain value due to the temperature rise (this value is set according to the motor characteristics or use requirements), the control circuit will act to cut off the motor circuit, so that the motor stops working, and the motor will play a protective role.