USCG Exam PracticeAC circuits and theory
On a shipboard switchboard, the wattmeter deflects to a negative reading while a generator is connected to the bus. What does this indicate?
- A. The generator's power factor has risen above unity
- B. The generator is supplying more reactive power than real power
- ✓ The generator is being motored by the bus and must be trippedCorrect
- D. The potential coil leads are reversed and the meter must be re-zeroed
Why C is correct
NEETS Mod. 3 §1-4 states that a wattmeter reading that swings negative warns of reverse power, in which a generator is being motored by the bus, and the machine must be tripped to protect its prime mover. A power factor above unity is not a defined operating condition; reversed leads would be a calibration/connection issue, not a normal operational reading.
Cited:NEETS Mod. 3 §1-4