For motor overload protection using fuses, a 3-wire 3-phase corner-grounded delta supply requires fuses in which conductors?

For motor overload protection using fuses, a 3-wire 3-phase corner-grounded delta supply requires fuses in which conductors?

• A. Every ungrounded conductor and every grounded conductor
• B. Only ungrounded conductors
• C. Only the grounded conductor
• D. The equipment grounding conductor

Answer: (A)

In motor overload protection using fuses, you want to protect every conductor that can carry current under normal or fault conditions. In a corner-grounded delta system there is a grounded conductor tied to the corner, which means that under fault conditions this conductor can become energized and carry current. To ensure any overload or fault current is quickly interrupted, fuses are placed in all ungrounded phase conductors and also in the grounded conductor. The equipment grounding conductor is a safety path intended to carry fault current only momentarily and is not designed to carry normal current, so it is not fused. This arrangement guarantees that any fault path a live current could take is interrupted by a fuse, providing proper protection for the motor and wiring.

In motor overload protection using fuses, you want to protect every conductor that can carry current under normal or fault conditions. In a corner-grounded delta system there is a grounded conductor tied to the corner, which means that under fault conditions this conductor can become energized and carry current. To ensure any overload or fault current is quickly interrupted, fuses are placed in all ungrounded phase conductors and also in the grounded conductor. The equipment grounding conductor is a safety path intended to carry fault current only momentarily and is not designed to carry normal current, so it is not fused. This arrangement guarantees that any fault path a live current could take is interrupted by a fuse, providing proper protection for the motor and wiring.