EGSA Load Bank Testing 2 — Questions and Answers
Question 1: What is the primary reason a generator set should be operated at a minimum of 30% rated load during a load bank test?
- To prevent wet stacking in diesel engines (Correct answer)
- To verify the automatic transfer switch operation
- To test the battery charging system
- To calibrate the fuel consumption meter
Correct answer: To prevent wet stacking in diesel engines
Operating below 30% load causes unburned fuel to accumulate in the exhaust system, a condition known as wet stacking.
Question 2: During a load bank test, the kW load is stepped up in increments. What is the typical step size used for standard acceptance testing?
- 10% of rated kW per step
- 25% of rated kW per step (Correct answer)
- 50% of rated kW per step
- 75% of rated kW per step
Correct answer: 25% of rated kW per step
Standard EGSA acceptance testing protocols use 25% load steps to evaluate generator response and stability.
Question 3: A resistive load bank draws power at what power factor?
- 0.8 lagging
- 0.9 lagging
- 1.0 unity (Correct answer)
- 0.7 leading
Correct answer: 1.0 unity
Resistive load banks convert all electrical energy to heat, resulting in unity (1.0) power factor with no reactive component.
Question 4: Which instrument is most critical for monitoring engine health during a load bank test on a diesel generator?
- Voltmeter
- Frequency counter
- Exhaust temperature pyrometer (Correct answer)
- Power factor meter
Correct answer: Exhaust temperature pyrometer
Exhaust temperature monitoring reveals overloading, fuel system issues, and turbocharger performance during load testing.
Question 5: What does a significant voltage drop under load during a load bank test most likely indicate?
- The load bank is malfunctioning
- The AVR or alternator excitation system has an issue (Correct answer)
- The transfer switch is not fully closed
- The fuel pressure is too high
Correct answer: The AVR or alternator excitation system has an issue
Excessive voltage drop under load points to automatic voltage regulator (AVR) problems or inadequate alternator field excitation.
Question 6: A reactive load bank test is performed primarily to evaluate the generator's ability to handle what type of load?
- Purely resistive heating loads
- Inductive motor and transformer loads (Correct answer)
- Capacitive power factor correction loads
- DC rectifier loads
Correct answer: Inductive motor and transformer loads
Reactive (inductive) load banks simulate real-world motor and transformer loads that demand kVAR in addition to kW.
Question 7: When performing a load bank test, why should the cooling air inlet and outlet be kept clear of obstructions?
- To prevent interference with the frequency governor
- To avoid overheating that could cause engine shutdown or damage (Correct answer)
- To ensure accurate kW meter readings
- To maintain proper battery float voltage
Correct answer: To avoid overheating that could cause engine shutdown or damage
Restricted airflow causes the engine and alternator to overheat, potentially triggering thermal shutdowns or causing permanent damage.
EGSA Load Bank Testing 2
What is the primary reason a generator set should be operated at a minimum of 30% rated load during a load bank test?