Question 509Electricity & Electronics - Assistant Engineer

The correct answer is C) 4.3 megohms. This is based on the requirements specified in the US Coast Guard regulations for electrical systems on inspected vessels. For a motor rated at 3.3 kV, the minimum accepted insulation resistance to hull ground should be at least 4.3 megohms, as tested by an appropriate megger or insulation tester. This value is derived from the general requirement that the insulation resistance should be at least 1 megohm per 1,000 volts of the circuit's voltage rating. The other options are incorrect because 2.3 megohms (A) and 3.3 megohms (B) are below the required minimum, while 6.6 megohms (D) exceeds the minimum without providing any additional benefit.