What is the function of an overload relay in a motor circuit?

The function of an overload relay in a motor circuit is specifically designed to protect the motor from excessive current that could lead to overheating and eventual burnout. When a motor operates under conditions of overload—such as jamming, excessive load, or mechanical failure—the current draw increases beyond the motor's rated capacity. An overload relay continuously monitors this current and, if it detects levels that exceed safe operating limits for a predetermined duration, it will open the circuit and disconnect power from the motor. This action helps prevent damage to the motor windings, which can occur from excessive heat generated by high current levels.

This protection mechanism is critical in industrial and commercial settings where motors are often required to operate continuously under varying loads. By interrupting the power supply when an overload condition occurs, the relay ensures the longevity and reliability of the motor, allowing it to function effectively without risk of damage from overheating.