What is a thermal overload relay?

A thermal overload relay is a crucial device designed to protect electric motors from overheating, which can occur due to excessive current draw or prolonged operation under heavy loads. This overheating can damage the motor windings, cause insulation failure, and lead to catastrophic motor failure.

When a motor operates, it generates heat. The thermal overload relay monitors the temperature or current of the motor and responds by breaking the circuit if it detects conditions that could lead to overheating. Essentially, it works based on the thermal properties of a bimetallic strip that bends when heated, which eventually allows the relay contacts to open and stop the current flow when temperatures exceed a safe threshold.

This protection mechanism helps in avoiding permanent damage to the motor and extends its life, making it an essential component in any system where electric motors are used.

The other options pertain to different functions or devices that do not fulfill the protective role against overheating specifically. While switches control electrical flow, circuit breakers focus on protecting against overloads and shorts, and voltage-increasing components serve a very different purpose in electrical systems.