Motor thermal overload switch is an electrical component that is installed in a circuit to ensure its safe operation. Its function is: when the circuit failure or abnormal, with the current rising, and the rising current may damage some important or valuable components in the circuit, may also burn out the circuit and even cause fire. If the temperature switch is properly placed in the transformer, when the temperature rises above a certain temperature, the bimetallic strip will break, and the temperature switch will automatically cut off the power supply. Thus plays the protection circuit safe operation the function.