Question 192Electricity & Electronics - QMED

The correct answer is C) The frequency of the incoming generator is approaching that of the bus. When paralleling two alternators, the synchronizing lamps are used to indicate when the frequencies and phase angles of the two alternators are matched. If the flickering of the lamps becomes progressively slower, it means that the frequency of the incoming alternator is approaching that of the bus. This indicates that the two alternators are getting closer to being in sync, and can be safely paralleled. The other answer choices are incorrect because: A) Opposite phase rotation would cause the lamps to flicker rapidly, not slowly. B) A significantly lower frequency of the incoming alternator would cause the lamps to flicker rapidly, not slowly. D) Matching terminal voltages is not indicated by the slowing of the lamp flickering.