An overload relay is a device used to protect electrical motors from damage due to excessive current. When a motor draws more current than it is rated to handle, typically caused by mechanical failure, jams, or prolonged running beyond its capacity, the overload relay disconnects the power supply to the motor, preventing potential damage. Overload relays are typically connected in series with the motor's power supply, and they are usually coupled with a contactor for efficient control and protection.

    Working Principle of Overload Relay

    The fundamental operation of an overload relay is simple： it detects the motor’s current and responds if it exceeds preset limits. When a motor runs under normal conditions, the relay continuously monitors the current drawn by the motor. If the current reaches a predetermined threshold for a set duration, the relay will activate and interrupt the power supply to the motor, ensuring that the motor is not exposed to harmful overcurrent.