VFD Troubleshooting Guide
VFD Problems can originate in:
- The VFD itself
- Motor
- Motor cable
- Incoming power
- Mechanical load
- Control wiring
- PLC/HMI
- Encoder/feedback system
- VFD programming
- Environmental conditions
The fastest way to troubleshoot a VFD is to identify exactly when the problem occurs, record the fault code, and determine whether the problem is electrical, mechanical, programming-related, or related to the motor/load.
| Problem | Common Causes | Troubleshooting |
|---|---|---|
| VFD won't start | Run command, enable, STO, reference | Diagnose control path |
| Overcurrent | Acceleration, load, motor, wiring | Check current/load |
| Overvoltage | Deceleration, regeneration | Check braking |
| Undervoltage | Supply sag, transformer, wiring | Check incoming power |
| Overload | Excessive load, sizing, cooling | Check motor/load |
| Ground fault | Motor, cable, insulation | Isolate motor circuit |
| Overheating | Cooling, ambient, load | Check thermal conditions |
| Motor won't accelerate | Load, ramp, current limit | Check acceleration demand |
| Motor runs too fast | Reference/scaling | Check speed command |
| Motor runs too slow | Reference/load/current limit | Check actual speed |
| Motor runs backwards | Phase/feedback/configuration | Verify direction |
| Encoder fault | Wiring, feedback, noise | Check encoder system |
| Speed fluctuates | Feedback/noise/tuning | Trend speed/current |
| Motor vibrates | Mechanical/control | Separate mechanical/control causes |
| Motor overheats | Load, low speed, motor cooling | Check motor duty |
| VFD trips randomly | Power/noise/thermal/load | Analyze fault history |
VFD Won't Start
Diagnostic sequence:
- Is the drive powered?
- Is there an active fault?
- Is the drive enabled?
- Is STO active?
- Is a run command present?
- Is the correct command source selected?
- Is the speed reference greater than zero?
- Is an external interlock preventing operation?
- Is the PLC sending the command?
- Is the motor connected correctly?
VFD Overcurrent
This article explains:
- What overcurrent means
- When it usually occurs
- Common causes
- How to diagnose it
- What information to record
Why Does My VFD Trip on Overcurrent? Causes and Solutions
Need help troubleshooting a VFD?
Send us the drive model, motor nameplate, fault code, application details, and photos of the wiring or drive display. Our VFD and industrial automation specialists can help identify the cause and recommend a solution.
