Question 175Electricity & Electronics - QMED

The correct answer is B) decrease. When an alternator is being paralleled with one already on the line, the frequency of the incoming alternator will momentarily decrease at the instant the incoming generator circuit breaker is closed. This is because the incoming alternator will need to synchronize its frequency and phase with the existing alternator on the line. The incoming alternator's frequency will initially be lower than the system frequency, causing the overall system frequency to momentarily decrease until the two alternators can properly synchronize. The other options are incorrect because: A) the frequency would not increase, C) the frequency would not remain unchanged, and D) the frequency would not be exactly 60 Hz at that instant.