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 A — clamp-on ammeter
A clamp-on ammeter permits safe, non-intrusive measurement of individual line currents in a three-phase AC motor, quickly exposing phase unbalance, single-phasing, or overloads per IEEE 45 guidelines.
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