The primary function of an overload relay is to prevent the electric motor from overheating, which can occur when the motor draws more current than its rated capacity. This situation often arises due to mechanical failure, blockages, or when the motor is running under heavy load for extended periods. If the motor continues to operate under these conditions, it can suffer from thermal damage, potentially leading to winding insulation breakdown, failure, or even fire hazards.

    Overload relays work by monitoring the current flowing through the motor's circuit. When the current exceeds the preset threshold, the relay acts to break the circuit, cutting off the power supply and stopping the motor. This protective action is typically triggered by a thermal element that responds to the heat generated by excessive current flow.