Learning outcomes
- Explain the key principles of vsd faults, harmonics and troubleshooting.
- Carry out a structured practical check or configuration task.
- Recognise common faults, risks and evidence needed for diagnosis.
Module 5 · Lesson 4
VSD faults, harmonics and troubleshooting
Diagnose overcurrent, overvoltage, undervoltage, earth fault, overheating, communications and process faults.
Before you begin
Fault history, drive manual, meter and trend data.
Safety: Use site procedures, approved test equipment and competent supervision. Never bypass a protection or interlock without formal control.
Step-by-step learning
- Record the exact fault code, time, speed, current and process condition.
- Separate input supply, drive, output cable, motor and mechanical-load causes.
- Check cooling, contamination, terminal tightness and DC-bus condition.
- Use trend and event logs to identify whether faults occur during start, run or stop.
Ian's practical tips:
- Do not megger a motor while it is still connected to a VSD.
- Fast deceleration can create DC-bus overvoltage even when the motor is healthy.
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.