EGSA Prime Mover and Governors 2 — Questions and Answers
Question 1: What is the primary function of a governor on a generator set prime mover?
- To regulate cooling water temperature
- To maintain engine speed by controlling fuel delivery (Correct answer)
- To regulate output voltage
- To control the air-fuel mixture ratio only at startup
Correct answer: To maintain engine speed by controlling fuel delivery
A governor controls fuel delivery to the prime mover to maintain a constant engine speed regardless of load changes.
Question 2: In a diesel engine prime mover, what component directly actuates the fuel injection rack in response to governor signals?
- The throttle body
- The actuator (fuel control unit) (Correct answer)
- The voltage regulator
- The speed sensor
Correct answer: The actuator (fuel control unit)
The actuator (fuel control unit) translates governor output signals into mechanical movement of the fuel injection rack.
Question 3: What is 'droop' in the context of a generator governor?
- The time delay before the governor responds to a load change
- The intentional speed decrease as load increases, expressed as a percentage (Correct answer)
- The voltage drop across the load terminals
- The mechanical wear on governor linkages over time
Correct answer: The intentional speed decrease as load increases, expressed as a percentage
Droop is the engineered speed reduction (typically 3–5%) that occurs as load increases, enabling stable parallel operation of multiple generators.
Question 4: A diesel generator is running at 60 Hz at no load but drops to 59.4 Hz at full load. What is the governor droop percentage?
- 1% (Correct answer)
- 2%
- 3%
- 5%
Correct answer: 1%
Droop % = (no-load speed − full-load speed) / rated speed × 100 = (60 − 59.4) / 60 × 100 = 1%.
Question 5: Which type of governor uses flyweights rotating with the engine to sense speed changes?
- Electronic isochronous governor
- Magnetic pickup governor
- Mechanical centrifugal governor (Correct answer)
- PID digital governor
Correct answer: Mechanical centrifugal governor
Mechanical centrifugal governors use flyweights that move outward or inward with centrifugal force to sense engine speed and adjust fuel accordingly.
Question 6: What happens to engine speed in an isochronous governor as load increases from no-load to full load?
- Speed decreases proportionally to load
- Speed increases to compensate for the load
- Speed remains constant regardless of load (Correct answer)
- Speed fluctuates until manually adjusted
Correct answer: Speed remains constant regardless of load
An isochronous governor maintains exactly the same speed from no-load to full load, unlike a droop governor which allows speed to decrease.
Question 7: A magnetic pickup (MPU) used with an electronic governor is mounted near which engine component?
- The camshaft belt
- The flywheel ring gear (Correct answer)
- The alternator rotor
- The oil pressure sender
Correct answer: The flywheel ring gear
The magnetic pickup senses the passing teeth of the flywheel ring gear to generate a frequency signal proportional to engine speed.
EGSA Prime Mover and Governors 2
What is the primary function of a governor on a generator set prime mover?