What is Thermal Overload Relay?

Thermal overload relays are economic electromechanical protection devices for the main circuit

Working Principle ofThermal Overload Relay

A thermal relay works depending upon the above-mentioned property of metals. The basic working principle of thermal relay is that, when a bimetallic strip is heated up by a heating coil carrying over the current of the system, it bends and makes normally open contacts.

Construction of Thermal Relay

The construction of a thermal relay is quite simple. As shown in the figure above the bimetallic strip has two metals โ€“ metal A and metal B.

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