Licensed Electrical Contractor Troubleshooting & Maintenance 4

Question 1

A submersible pump motor has failed megohmmeter testing. Before condemning the motor, you should:

Accepted Answer

Allow the motor to dry thoroughly and retest, as moisture affects readings

Answer

Moisture ingress in submersible motors dramatically reduces insulation resistance; the motor should be dried and retested before replacement.

Question 2

A transformer secondary voltage is 10% higher than nameplate rating with no load. The most likely cause is:

Accepted Answer

Wrong tap setting on the primary side of the transformer

Answer

Incorrect primary tap settings change the turns ratio, directly affecting secondary output voltage — selecting a lower voltage tap raises secondary voltage.

Question 3

When troubleshooting an intermittent ground fault on a large commercial system, the best systematic approach is to:

Accepted Answer

Divide the system in half repeatedly (half-split method) to isolate the fault section

Answer

The half-split method isolates intermittent faults efficiently by systematically eliminating half the system with each test.

Question 4

During maintenance on a 480V motor starter, you find the contactor contacts are pitted and eroded. The correct maintenance action is to:

Accepted Answer

Replace the contact assembly — filed contacts reduce contact pressure and life

Answer

Contactor contacts should be replaced when worn, not filed; filing reduces thickness, changes geometry, and shortens remaining service life.

Question 5

A 20A, 120V circuit is protected by a 20A AFCI breaker and also uses a GFCI outlet as the first device. A ground fault occurs downstream. Which device should operate first?

Accepted Answer

The GFCI outlet, as it is closest to the fault

Answer

The GFCI outlet closest to the fault should trip first due to its faster response to line-to-ground current imbalance at that point.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Troubleshooting & Maintenance 4