Marine Electrical Systems USCG Q#1338 (Set 45)

For a motor rated at 3.3 kV, what would be a minimum accepted insulation resistance to hull ground as tested by an appropriate megger (insulation tester)?

Official USCG Answer & Rule Citation

Correct Answer: Option C — 4.3 megohms

IEEE 45 guidelines for insulation resistance testing specify a minimum megger value using the formula $R_m = KV + 1$. For a 3.3 kV motor, $3.3 + 1 = 4.3$ megohms, ensuring adequate dielectric strength against hull ground under marine operating and humidity conditions.

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