Question 184Electricity & Electronics - 1st Asst/Chief

The correct answer is D) overload relay heaters and overload relay NC contacts (OL). The overload relay is designed to detect a sustained motor overload condition and disconnect the motor from the power source to prevent damage. The overload relay heaters monitor the motor current, and if a sustained overload is detected, the normally closed (NC) overload relay contacts will open, interrupting the motor control circuit and disconnecting the motor. This is the primary mechanism to protect the motor from a sustained overload, making this the correct answer. The other options, such as transformer fuses or disconnect switch fuses, are not the primary mechanism for disconnecting the motor in an overload situation. They may provide overcurrent protection, but the overload relay is the key component designed for this specific purpose.