Marine Electrical Systems USCG Question #953 (Set 32)

Suppose it is desired to determine the integrity of the insulation of a 4160 VAC motor. What type of insulation resistance tester (megger) would be suitable?

Official USCG Answer & Rule Citation

Correct Answer: Option D — 5000 V megger

Insulation testing of high-voltage machinery requires a megohmmeter rated above the operating voltage. Per IEEE 45 and manufacturer guidelines, a 4160 VAC motor winding necessitates a 5000 V insulation resistance tester to properly stress and evaluate dielectric integrity.

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