Electrical Maintenance Practices and Troubleshooting
What this domain tests
Electrical Maintenance Practices and Troubleshooting tests planned and breakdown maintenance, safe isolation, insulation resistance, continuity, vibration and thermal checks, and a logical fault-finding sequence.
Core rules
- Maintenance types include preventive, predictive and breakdown. Predictive work uses vibration, thermography, oil and insulation trends before failure.
- Isolate, lock out and tag out before work; prove dead with a suitable tester.
- Insulation resistance is measured with a megger at the specified voltage; compare readings with manufacturer limits and previous trends.
- Troubleshoot in order: observe, isolate, test supply, test component, repair or replace, then retest under load.
- Phase imbalance, loose terminals, overload, bearing wear and ventilation blockage are common causes of motor trips.
Worked example
A pump motor trips its overload after 10 minutes. The nameplate current is 14 A, but a clamp meter reads 18 A on one phase while others read 14 A. This suggests a supply imbalance or a single-phase load fault, not simply a weak overload. Check supply voltage on all phases, terminal tightness, pump blockage and alignment. Correct the cause before resetting the relay.
Traps that cost marks
Replacing a fuse or resetting a trip without finding the fault, testing insulation on a live circuit, using a multimeter as a megger, ignoring a hot terminal, and restarting a motor repeatedly after a trip. Record readings so trends can reveal deterioration.