How does an overload relay operate in a motor protection circuit?

An overload relay operates in a motor protection circuit by disconnecting power if the current exceeds a preset level. The primary function of an overload relay is to monitor the current flowing through the motor. When the current exceeds the designated threshold, indicating that the motor is drawing more current than it is designed for—often due to issues such as overheating, mechanical failure, or jamming—the relay activates its mechanism to open the circuit. This action helps prevent damage to the motor by stopping the power supply, thereby protecting it from excessive heat and potential burnout.

While sensing temperature changes can be a feature of other protective devices, it is not the main operational principle of an overload relay. Monitoring voltage fluctuations is important for overall motor protection, but this is not the specific role of an overload relay. Speed regulation, on the other hand, is typically handled by separate control devices and not by the overload relay itself. Thus, the core function of the overload relay is crucial for safeguarding the motor from overcurrent conditions.