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Electrician Red Seal · Question

An industrial facility requires grounding for a new 480 V, 3-phase motor control centre. The service entrance is configured as a solidly grounded wye system. Which of the following is the primary purpose of grounding the non-current-carrying metal parts of the motor control centre?

Grounding the non-current-carrying metal parts creates a low-impedance path to ground for fault currents. This path facilitates the rapid operation of overcurre

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Question: An industrial facility requires grounding for a new 480 V, 3-phase motor control centre. The service entrance is configured as a solidly grounded wye system. Which of the following is the primary purpose of grounding the non-current-carrying metal parts of the motor control centre?

Answer options:

  • To provide a low-impedance path for lightning surges.
  • To stabilize the system voltage during normal operation. ✅ To ensure proper operation of overcurrent protective devices during a ground fault.
  • To reduce electromagnetic interference (EMI) between electrical equipment.

Correct answer: To ensure proper operation of overcurrent protective devices during a ground fault.

Explanation: Grounding the non-current-carrying metal parts creates a low-impedance path to ground for fault currents. This path facilitates the rapid operation of overcurrent protective devices (like circuit breakers or fuses), clearing the fault and preventing extended hazards.

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