Question 176Electricity & Electronics - QMED

70% to pass

An alternator switchboard has a synchroscope and synchronizing lamps. If the synchroscope is broken, which of the steps listed is the most essential before an alternator can be paralleled with the bus?

AThe breaker should be closed when both synchronizing lamps are bright.

BA portable phase sequence indicator must be used to verify the information from the lamps.

CThe breaker should be closed when one synchronizing lamp is dark and the other is bright.

DThe frequency meter should be used to determine that the incoming alternator frequency is slightly higher than the bus, then the breaker should be closed when both synchronizing lamps are dark.

AI Explanation

The correct answer is D. When the synchroscope is broken, the most essential step before paralleling an alternator to the bus is to use the frequency meter to ensure the incoming alternator frequency is slightly higher than the bus frequency. Then, the breaker should be closed when both synchronizing lamps are dark, indicating the phases are in sync. This is the correct approach because it ensures the alternator is synchronized with the bus in terms of both frequency and phase before closing the breaker. The other options are incorrect because they do not properly account for the lack of a functioning synchroscope, which is a critical tool for verifying synchronization.