Working Principle Of Contactor Thermal Relay

A contactor thermal relay operates based on the principle of thermal expansion to protect electrical circuits from overloads.

 

Here’s how it works:

1.Temperature Sensing: The thermal relay contains a bimetallic strip or a temperature-sensitive element that expands when exposed to excessive heat generated by overcurrents in the circuit.

2.Trip Mechanism: As the temperature rises, the bimetallic strip bends or the temperature-sensitive element activates, triggering the trip mechanism of the relay.

3.Contacts Opening: Once tripped, the thermal relay opens its contacts, interrupting the flow of current in the circuit. This prevents further heating and damage to the electrical system.

4.Resetting: After the fault is cleared and the temperature returns to normal, the thermal relay resets automatically or manually, restoring power to the circuit.

 

In summary, contactor thermal relays provide thermal overload protection by sensing temperature changes caused by overcurrents, tripping to interrupt the circuit and prevent damage to electrical equipment.