A bimetal is also called a thermobimetal and is an overload protector that activates when subjected to thermal-mechanical stress. Bimetals compriseseparate strips of different metals that are bonded or form-fit. Due to the different thermal expansion coefficients of the metals used, the bimetal changes in shape when exposed to fluctuations in temperature and returns to its original state after cooling down to normal temperature.
Inflowing motor current heats up a heating coil for each current-carrying line in the bimetal. As soon as a threshold value is exceeded, the bimetal interrupts the circuit to the motor.