Function: Mainly used for overload protection of asynchronous motor. His working principle is that after the overload current passes through the heat element, the bimetal is heated and bent to push the action mechanism to drive the contact action, thereby disconnecting the motor control circuit to realize the motor break. Electric parking, which acts as an overload protection. In view of the fact that the transfer of heat takes a long time during the bending of the bimetal, the thermal relay cannot be used as a short circuit protection, but can only be used as an overload protection.