What is a useful instrument for checking 3 phase A.C. motor performance by measuring possible unbalanced currents?
Official USCG Answer & Rule Citation
Correct Answer: Option C — clamp-on ammeter
A clamp-on ammeter measures current inductively without breaking the circuit. It is ideal for rapidly detecting phase current imbalances in three-phase AC motors, indicating winding faults, voltage unbalance, or mechanical overloads.
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