When an overload occurs in an electric motor, it generates an increase in the intensity of electric current circulating in the conductors causing a heating, joule effect.
The operating 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 the motor shutdown and signaling the problem.
The bimetallic elements, formed by two very thin blades consisting of materials with different expansion coefficients, overlapping 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 into the load control circuit to be protected.
When the overload relay operates, its normally closed contacts, 95 to 96, inserted in series with the commanded charge main contactor, and its normally open contacts, 97 to 98, normally used to close a circuit, close. signpost, signal lamp.
