If it becomes absolutely necessary to run an alternator at lower than 5% below its rated frequency, in terms of output voltage, what must be done?

Correct Answer: Option A — The alternator output voltage must be decreased proportionately downward with the frequency decrease.

Alternator output voltage is directly proportional to operating frequency and magnetic flux speed. Per marine engineering standards and IEEE 45, if frequency drops more than 5% below rated value, voltage must be proportionately decreased to prevent core magnetic saturation and overheating.