What is an electronic overload relay primarily used for?

An electronic overload relay is specifically designed to protect electric motors from overload conditions by monitoring the current flowing through the motor. When the current exceeds a predetermined level for a specific duration, indicating that the motor is running under excessive load, the relay interrupts the electrical supply to the motor. This prevents potential overheating and damage to the motor, ensuring its longevity and operational efficiency.

The other options relate to monitoring or measuring parameters not directly associated with motor protection. Voltage fluctuations are not the primary concern of a relay designed for overload conditions, while monitoring pressure levels and measuring temperature gradients typically involve different types of sensors or protection devices, not overload relays. Thus, the primary function of an electronic overload relay is clearly to safeguard motors against overload scenarios, validating the correctness of the chosen answer.