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.
Safety first
Random restarts/trips can cause unexpected motion. Confirm restart behaviour and keep the area clear. Isolate before handling wiring.
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
Loose power or control connections
Most likelyLoose terminals cause intermittent faults that come and go with vibration/temperature.
- 2
Electrical noise / poor earthing
#2Poor screening/earthing lets noise trigger spurious faults, especially around switching events.
- 3
Marginal supply or load conditions
#3A supply or load that's borderline trips the drive only under certain conditions.
- 4
Environmental (heat, dust, moisture)
#4Heat, dust, or condensation cause occasional faults tied to conditions.
- 5
Firmware/parameter quirk
Least likelyOccasionally a parameter setting or firmware issue causes spurious trips.
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 ModeLog the exact codes and timestamps over several trips to find a pattern.
A correlation between trips and an event/condition.
A pattern points you to the cause group — follow it.
No pattern yet — focus on connections, earthing, and environment.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
VSD nuisance tripping
→ step 2 - 2decision
Do logged codes/timestamps reveal a pattern?
Yes→ step 3No→ step 4 - 3result
Follow the pattern to its cause group.
- 4decision
Are all connections tight and earthing/screening sound?
Yes→ step 5No→ step 6 - 5decision
Are supply/load margins and environment all suitable?
Yes→ step 7No→ step 8 - 6result
Loose terminal or poor earth — repair it.
- 7result
Review parameters/firmware with the drive documentation.
- 8result
Marginal supply/load or harsh environment — address it.
Common mistakes apprentices make
- Clearing trips without logging codes/timestamps to find a pattern.
- Ignoring earthing/screening as a noise source.
- Not checking terminal tightness on an intermittent fault.
- Assuming a drive replacement before ruling out the install.
When to stop & escalate
Once installation, connections, and environment are ruled out, take the logged codes to the drive's documentation/support. Earthing/screening issues on a larger install may need a planned fix.
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
VSD trips on overcurrent / overload
The drive trips with an overcurrent or overload code — on start, on acceleration, or under running load. It may restart and trip again on the same point in the cycle.
VSD communication / fieldbus fault
The drive has lost communication with the PLC/SCADA over its fieldbus (e.g. control by network) — comms-loss fault, no remote control, or the drive stops on comms timeout.
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.