USCG Exam PracticeHand/power tools, measuring instruments, and maintenance
Before paralleling an incoming generator to the bus, the operator uses a synchroscope and frequency meter together. At what position of the synchroscope pointer should the breaker be closed?
- A. As the pointer passes through the six o'clock (180°) position, indicating opposite phase
- ✓ As the pointer creeps slowly through the twelve o'clock (in-phase) positionCorrect
- C. At any position, provided the frequency meters show identical readings
- D. As the pointer accelerates through the three o'clock position to allow for breaker closing time
Why B is correct
The synchroscope and frequency meter are used together to match frequency and phase before paralleling. The breaker is closed only as the synchroscope creeps slowly through its in-phase, twelve o'clock position. Closing at any other position risks a severe out-of-phase connection.
Cited:NEETS Mod. 3 §1-4