EGSA Electrical Systems Troubleshooting 5

Question 1

During a voltage dip test, a generator's voltage recovers but takes longer than the manufacturer specifies. What is the most likely cause?

Accepted Answer

Sluggish AVR response due to incorrect gain setting

Answer

Low engine coolant temperature

Answer

Incorrect fuel filter

Answer

Misaligned flexible coupling

Question 2

What is the significance of a high kW but low kVA reading on a generator under load?

Accepted Answer

The power factor is near unity, indicating mostly resistive load

Answer

The generator is overloaded

Answer

The generator is under-excited

Answer

The stator windings are shorted

Question 3

A generator produces correct voltage at no-load but the output collapses when connected to a motor starting load. What should be evaluated?

Accepted Answer

Generator's transient reactance and short-circuit capability

Answer

Fuel tank capacity

Answer

Engine block heater function

Answer

Transfer switch bypass setting

Question 4

Neutral-to-ground voltage above 2V in a solidly grounded 120/208V system typically indicates:

Accepted Answer

Excessive neutral current due to unbalanced or non-linear loads

Answer

Normal system operation

Answer

Overvoltage from the utility

Answer

Correct bonding of the neutral and ground

Question 5

When a generator fails to build voltage after a field flash attempt, the next step is to:

Accepted Answer

Test the rotating rectifier diodes for open or short circuit

Answer

Recheck the engine speed

Answer

Inspect the transfer switch contacts

Answer

Replace the governor actuator

Question 6

Which protective relay function trips a generator when it detects reverse power flow from the bus into the machine?

Accepted Answer

ANSI Device 32 (reverse power relay)

Answer

ANSI Device 27 (undervoltage relay)

Answer

ANSI Device 81 (frequency relay)

Answer

ANSI Device 87 (differential relay)

Question 7

A technician notices the generator output voltage varies with changes in engine speed even though the AVR is functional. What is the most probable cause?

Accepted Answer

The AVR voltage sensing input has a loose connection

Answer

The generator is over-fueled

Answer

The brushes are too long

Answer

The coolant thermostat is stuck open