What is an overload relay used for?

An overload relay is specifically designed to protect electric motors from overheating that can occur due to excessive current. When a motor experiences a current above its rated capacity, the overload relay detects this condition and interrupts the power supply to the motor. This prevents damage that could result from prolonged overheating, which might lead to insulation failure or other mechanical issues. The relay typically uses a bimetallic strip that bends when heated by the excess current, eventually triggering the relay and disconnecting the circuit.

The other choices focus on aspects that are not the primary function of an overload relay. Enhancing motor performance or monitoring energy efficiency might involve different types of devices or systems that are designed for those purposes, such as variable frequency drives or energy management systems. Increasing electrical current to motors would be counterproductive as it could further exacerbate problems of overheating rather than providing protection. Therefore, the correct answer highlights the main role of an overload relay in safeguarding motors.