Licensed Electrical Contractor Troubleshooting & Maintenance 2

Question 1

A motor repeatedly trips its overload relay shortly after reset. What is the most likely cause?

Accepted Answer

Motor running in a high-resistance fault condition

Answer

A motor tripping overloads repeatedly after reset typically indicates a high-resistance fault (such as a failing winding or bearing friction) drawing excess current.

Question 2

When using a clamp-on ammeter to troubleshoot a single-phase 240V circuit, you clamp around both conductors and read zero. What does this indicate?

Accepted Answer

Normal balanced current flow

Answer

Clamping both conductors of a single-phase circuit cancels opposing magnetic fields, resulting in a zero reading, which indicates normal balanced current.

Question 3

A GFCI outlet tests correctly but will not reset. The most likely cause is:

Accepted Answer

A downstream ground fault is still present

Answer

A GFCI that trips immediately upon reset indicates a ground fault condition still exists on the circuit or load side.

Question 4

During a megohmmeter test on a cable, the insulation resistance reads near zero. The best next step is to:

Accepted Answer

Disconnect all equipment and retest the cable alone

Answer

Disconnecting all equipment isolates whether the low reading is from the cable itself or connected loads before condemning the cable.

Question 5

A 3-phase motor is running but drawing unequal currents on all three phases. Single-phasing has been ruled out. What is the most likely cause?

Accepted Answer

Voltage unbalance on the supply

Answer

Even a small supply voltage unbalance causes disproportionately larger current unbalance in a 3-phase motor.

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Practice Test

Licensed Electrical Contractor Troubleshooting & Maintenance 2