Learning outcomes
- Explain the key principles of motor protection and condition monitoring.
- Carry out a structured practical check or configuration task.
- Recognise common faults, risks and evidence needed for diagnosis.
Module 3 · Lesson 3
Motor protection and condition monitoring
Use overload, phase-failure, earth-fault, temperature, vibration and insulation information to protect motors.
Before you begin
Protection relay manual, motor data and trend records.
Safety: Use site procedures, approved test equipment and competent supervision. Never bypass a protection or interlock without formal control.
Step-by-step learning
- Set overload and trip class for the actual starting duty.
- Check phase-current imbalance and compare against supply-voltage imbalance.
- Review winding/bearing temperature, vibration and start-count trends.
- Create alarm, warning and trip limits with clear operator actions.
Ian's practical tips:
- Current imbalance can heat a motor badly even when average current looks acceptable.
- Trend changes over time; a single reading rarely tells the whole condition story.
Fault-finding questions
- What should be happening, and what evidence proves it?
- Where is the last known correct signal, voltage, state or process condition?
- What changed immediately before the fault?
- Can the system be divided into smaller testable sections?
Practical activity
Create a one-page test record for this lesson. Include expected values, measured results, equipment used, risks controlled, defects found and the final proven condition.