Motor noisy or whining when run on a VSD
The motor runs but is noticeably noisy on the drive — a whine, whistle, or growl that isn't there on direct supply, sometimes worse at certain speeds.
Safety first
Mostly a quality/comfort issue, but persistent resonance can stress the drivetrain. Isolate before mechanical checks. Keep clear of the shaft.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Apprentice mode
Full walk-through — the why, what readings mean, mistakes & safety.
Likely causes
Ranked from most to least likely.
- 1
Switching (carrier) frequency audible
Most likelyA low carrier frequency makes the motor emit an audible whine that a higher carrier can reduce.
- 2
Mechanical resonance at certain speeds
#2The system resonates at particular frequencies, producing noise/vibration at those speeds.
- 3
Control mode / tuning
#3Some control modes or aggressive tuning create more audible noise.
- 4
Genuine mechanical issue surfacing
Least likelyBearings/coupling problems can be more apparent under drive operation.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
On the tools? Job Mode shows one test at a time with thumb-sized buttons — your place and readings carry straight over.
Enter Job ModeNote whether the noise changes with speed and whether it's a steady whine or speed-specific.
A characterisation: steady whine vs speed-specific resonance.
Steady whine → likely carrier frequency. Speed-specific → resonance.
Noise that tracks a mechanical fault → check bearings/coupling.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
Motor noisy on VSD
→ step 2 - 2decision
Is it a steady whine (vs speed-specific or mechanical)?
Yes→ step 3No→ step 4 - 3decision
Does adjusting carrier frequency reduce it?
Yes→ step 5No→ step 4 - 4decision
Is it tied to specific speeds (resonance)?
Yes→ step 6No→ step 7 - 5result
Carrier-frequency whine — set within the allowed range.
- 6result
Use skip frequencies to avoid the resonant point.
- 7result
Mechanical fault surfacing — check bearings/coupling.
Common mistakes apprentices make
- Assuming a fault when it's just audible carrier-frequency whine.
- Raising carrier frequency without regard to drive derating/heat.
- Not using skip frequencies for a clear resonance point.
- Missing a genuine bearing problem made obvious by the drive.
When to stop & escalate
Carrier-frequency changes can affect drive heating and cable stress — stay within the manufacturer's guidance. Persistent resonance may need a mechanical/structural review.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
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Related faults
Motor noisy or vibrating (bearing / mechanical)
The motor runs but is noisy, rough, or vibrating — grinding, rumbling, or whining noises that point to bearings or mechanical trouble.
VSD nuisance tripping with no obvious cause
The drive trips intermittently with codes that don't seem to match the conditions — random faults, hard to reproduce, often noise- or connection-related.
Motor draws fluctuating current / unstable running
The motor runs but its current swings up and down, speed surges, or it runs roughly — pointing at load variation, supply, or control instability rather than a hard fault.
Learn the theory
How the gear and circuits behind this fault actually work.