HOLT Electricians Practice Exam

If a fuse is used for overload protection on a motor, where must it be installed?

1. On the motor frame

2. On each ungrounded conductor

3. At the main panel board

4. On the grounded conductor

The correct answer is: On each ungrounded conductor

Installing a fuse for overload protection on a motor directly on each ungrounded conductor is crucial for several reasons. First, placing the fuse on each ungrounded conductor ensures that the protection provided is specific to the electrical path that powers the motor. This allows for the immediate disconnection of power to the motor in case of an overload condition, thus preventing excessive current that could lead to damage or overheating of the motor windings. Additionally, if the fuse were installed on the motor frame or at the main panel board, it would not provide timely protection directly at the point of overcurrent. This could potentially allow high fault currents to damage the motor before the fuse reacts. By ensuring fuses are present on each ungrounded conductor, a more rapid and effective response to overload conditions is achieved. Moreover, placing a fuse on the grounded conductor is not advisable because it could lead to safety risks and improper operation of the motor; the grounded conductor should remain uninterrupted to ensure the grounding system functions effectively. Therefore, the correct location for installing fuses for protecting motors in the event of overload is indeed on each ungrounded conductor.