A technician is troubleshooting a DC generator system in which output voltage fluctuates excessively with engine RPM changes. Which component is primarily responsible for maintaining constant output voltage despite varying generator speed?
- AReverse current cutout relay
- BOvervoltage protection relay
- CEqualizing coil
- DVoltage regulator
Show answer & explanationAnswer & explanation
Correct answer: D. Voltage regulator
The voltage regulator maintains constant generator output voltage by controlling the field current supplied to the generator; as RPM changes, the regulator adjusts field resistance (as in a carbon pile or vibrating point regulator) to hold output voltage steady. The reverse current cutout protects the battery from discharging back through the generator, overvoltage relays protect against excessive voltage spikes, and equalizing coils balance load sharing between paralleled generators.
Why the other options are wrong
- A. This relay disconnects the generator from the bus when generator voltage drops below battery voltage, not for voltage regulation.
- B. This is a protective device that trips at excessive voltage, not a continuous regulating device.
- C. Equalizing coils are used only in multi-generator paralleling systems for load sharing.
Voltage Regulator (DC Generator)
A device that automatically adjusts generator field current to maintain a constant output voltage regardless of changes in generator speed or load.
- Carbon pile regulators use pressure to vary resistance in the field circuit
- Vibrating point (vibrator-type) regulators rapidly open/close field circuit
- Works with reverse current relay and overvoltage relay for full protection
Memory trick: Regulator rides the field current like a governor keeping voltage steady