Question 176Electricity & Electronics - QMED

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.