EGSA Power Generation Equipment 4

Question 1

What causes harmonic distortion in a generator's output voltage waveform?

Accepted Answer

Non-linear loads such as variable frequency drives and switch-mode power supplies

Answer

Non-linear loads draw current in pulses rather than sinusoidally, injecting harmonic currents that distort the generator's output voltage waveform.

Question 2

When two generators are being synchronized for parallel operation, which parameter must be matched last to avoid circulating currents?

Accepted Answer

Phase angle

Answer

Phase angle is matched last (at closing) using a synchroscope or sync check relay to ensure the breaker closes at the exact moment the phase angles align.

Question 3

What is the purpose of the anti-condensation heater installed in a generator alternator?

Accepted Answer

Prevent moisture condensation on alternator windings during shutdown periods

Answer

Anti-condensation heaters keep alternator windings slightly above ambient temperature during standby to prevent moisture from condensing and degrading insulation resistance.

Question 4

Which factor primarily determines the synchronous speed of an AC generator?

Accepted Answer

Number of magnetic poles and operating frequency

Answer

Synchronous speed (RPM) = (120 × frequency) / number of poles; a 4-pole generator must spin at 1800 RPM to produce 60 Hz output.

Question 5

What is the primary hazard of operating a generator with a single-phase load heavily unbalanced across phases?

Accepted Answer

Overheating of the most heavily loaded phase winding and neutral conductor

Answer

Severe phase unbalance causes one phase winding and the neutral conductor to carry excess current, leading to overheating and potential insulation failure.

(EGSA) Electrical Generating Systems Association Certified Practice Test

(EGSA) Electrical Generating Systems Association Certified Practice Test

EGSA Power Generation Equipment 4