Electrical Systems Troubleshooting Flashcards
7 cards from real EGSA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Electrical Systems Troubleshooting flashcards as text
Excessive third-harmonic distortion in a generator's output is most commonly caused by:
Answer: Non-linear loads such as UPS systems and VFDs
Non-linear loads draw current in pulses rather than sinusoidal waves, generating third and other odd harmonics that distort the generator output waveform.
When load testing a generator, what parameter confirms the generator is operating within its rated kVA capacity?
Answer: Both kilowatts and kVAR readings within nameplate rating
kVA capacity is determined by both the real power (kW) and reactive power (kVAR) components, and both must be within nameplate limits to confirm proper operation.
A parallel-connected generator is importing reactive power (absorbing VArs) instead of exporting. The likely cause is:
Answer: Under-excitation of the generator field
Under-excitation causes the generator to operate in a leading power factor mode, absorbing reactive power from the bus rather than supplying it.
What is the most appropriate test to verify continuity of a generator's rotor winding without disassembly?
Answer: Slip ring resistance measurement with an ohmmeter
Measuring resistance across the slip rings with an ohmmeter checks rotor winding continuity and compares the reading against the manufacturer's specification.
Which fault condition causes unequal voltage readings across each phase of a three-phase generator but normal frequency?
Answer: Partial short in one phase stator winding
A partial short in one phase stator winding reduces the turns ratio and output impedance of that phase, lowering its voltage while the other phases remain normal.
When a generator's voltage regulation is poor under varying loads, which component should be calibrated or replaced first?
Answer: AVR
The AVR continuously adjusts excitation to maintain constant output voltage; poor regulation under varying loads is the primary symptom of an AVR fault or misadjustment.
A technician measures 0 ohms between two phase conductors in a de-energized three-phase system. This indicates:
Answer: A phase-to-phase short circuit
Zero resistance between two phase conductors in a de-energized system indicates a bolted or solid phase-to-phase short that must be located and cleared before re-energizing.