When an overload occurs in an electric motor, it generates an increase in the intensity of the electric current that circulates in the conductors causing a heating, joule effect.
The working principle of the overload relay is based on the joint action of 3 bimetallic elements, each corresponding to a motor supply phase, and 2 switches, responsible for stopping the motor and signaling the problem.
The bimetallic elements, formed by two very thin blades made of materials with different expansion coefficients, superimposed and welded, when heated undergo a bending, this bending is transmitted through mechanical gears to the switch that opens or closes its contacts (95 - 96 and 97 - 98) inserted in the control circuit of the load to be protected.
