Bimetal, also called thermal bimetal, is an overload protector that activates when subjected to thermomechanical stress. Bimetals include separate strips of different metals that are bonded or form-fitted. Due to the different thermal expansion coefficients of the metals used, the bimetal undergoes a shape change when exposed to temperature fluctuations and returns to its original state after being cooled to normal temperature.
The incoming motor current heats the heating coil of each current-carrying wire in the bimetallic strip. Once the threshold is exceeded, the bimetal will interrupt the circuit with the motor.