Maintenance & Troubleshooting — Industrial Electrician (442A) Practice Questions

Free Maintenance & Troubleshooting practice questions

1. 1.A motor is tripping on overload intermittently. What should be checked first?

   • A.Replace the motor
   • B.Check actual current draw vs nameplate FLA, check for mechanical binding, and verify overload setting✓
   • C.Replace the starter
   • D.Check the paint

   Why: Measure running amps on all phases. Compare to nameplate FLA. Check for: mechanical load issues, phase imbalance, loose connections, ventilation blockage, overload set too low.

2. 2.When troubleshooting a control circuit, you measure 120V across a contactor coil but it won't pull in. What's the issue?

   • A.Voltage is too high
   • B.The coil is open (burned out) — voltage present but no current flows through an open coil✓
   • C.The voltage is normal, no problem
   • D.The control transformer is bad

   Why: Voltage across an open component = source voltage (voltage divider with infinite resistance). The coil has failed open-circuit. Replace the contactor or coil. Measure current to confirm.

3. 3.When a 3-phase motor hums but doesn't start, the most likely cause is:

   • A.Low oil level
   • B.Single-phasing — one phase is lost (blown fuse, broken wire, bad contactor contact)✓
   • C.Motor is too large
   • D.Foundation is loose

   Why: A 3-phase motor with one phase missing cannot develop starting torque — it just hums loudly and draws high current. Check all 3 phases at the motor terminals. Common cause: one contactor contact failed.

4. 4.A motor bearing failure is best detected early using:

   • A.Visual inspection
   • B.Vibration analysis showing bearing defect frequencies (BPFO, BPFI, BSF, FTF)✓
   • C.Resistance measurement
   • D.Voltage measurement

   Why: Vibration analysis detects bearing defects months before failure by identifying characteristic frequencies. Ultrasonic testing detects even earlier-stage defects. Together they enable planned replacement.

5. 5.A PLC input LED is ON but the program doesn't see the input. What should be checked?

   • A.The output module
   • B.The input module hardware, wiring connection, and whether the correct PLC address is being monitored✓
   • C.The power supply only
   • D.The network cable

   Why: LED ON means the field device is providing signal. If the PLC program doesn't register it: check if you're monitoring the correct address, check the input module for fault, verify the slot/channel mapping.

6. 6.A ground fault on a 3-phase ungrounded delta system — the first fault causes:

   • A.A trip
   • B.No trip — but one phase now has 0V to ground and the other two have full line voltage to ground✓
   • C.An explosion
   • D.Nothing at all

   Why: On ungrounded delta, the first ground fault doesn't trip anything (no ground return path). But it elevates the other two phases to full line-to-line voltage to ground, stressing insulation. A second ground fault on another phase creates a phase-to-phase short.

7. 7.A motor running hot but drawing normal amps likely has:

   • A.An electrical problem
   • B.A cooling problem — blocked ventilation, failed cooling fan, or dirty motor✓
   • C.A control circuit issue
   • D.Too much grease

   Why: Normal amps = normal electrical loading. Overheating with normal current points to cooling deficiency: clogged air passages, failed external fan, high ambient temperature, or excessive regreasing blocking air paths.

Other 442A exam blocks

Other Red Seal trades

RedSeal Prep Pro is an independent study tool. Practice questions are original content written in the style of the Certificate of Qualification and are not affiliated with the Red Seal Program, the Industrial Electrician trade board, or any provincial certification body.