VSD trips on overcurrent only during acceleration
The drive runs steadily once up to speed, but throws an overcurrent (or 'OC on accel') fault each time it ramps up to speed. Runs fine if it gets there; trips on the way up.
Safety first
Drives hold dangerous DC bus voltage after power-off — wait for the discharge time before opening. Follow the manufacturer's manual for the exact fault code; don't just clear faults and keep restarting.
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
Acceleration ramp too fast for the load inertia
Most likelyA short accel time on a high-inertia or heavily-loaded machine demands more current than the drive limit allows while ramping, so it trips on overcurrent during accel.
- 2
Mechanical load too high or binding
#2A stiff, jammed, or overloaded driven machine forces high current as the drive tries to accelerate it.
- 3
Incorrect motor data / no autotune
#3Wrong nameplate parameters or a missing autotune means the drive's current control is off, causing overcurrent during the demanding accel phase.
- 4
Wrong V/Hz or boost setting
Least likelyExcessive low-speed torque boost pushes too much current at the start of the ramp.
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 ModeRead the exact fault code/log and confirm it's overcurrent during acceleration, not at steady speed or on decel.
A clear 'overcurrent on accel' indication in the drive log.
Confirms the accel phase is the trigger — focus there.
If it's actually decel/steady, switch to the matching fault path instead.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
VSD overcurrent on acceleration
→ step 2 - 2decision
Does a longer accel ramp stop the trip?
Yes→ step 3No→ step 4 - 3result
Ramp too fast for the inertia — set an accel time the load can handle.
- 4decision
Does the load turn freely and motor data/autotune check out?
Yes→ step 5No→ step 6 - 5result
Recheck V/Hz and torque boost; if sizing is the limit, escalate.
- 6result
Mechanical binding or wrong motor data — fix mechanics or re-enter/tune parameters.
Common mistakes apprentices make
- Clearing the fault and restarting repeatedly without changing anything.
- Slamming the accel time so short the drive can never ramp the inertia.
- Skipping the autotune and leaving default motor data in.
- Cranking torque boost up and pushing even more current at low speed.
When to stop & escalate
If the load genuinely needs more starting torque/current than the drive can deliver, escalate to review drive/motor sizing or add a brake-resistor/inertia solution. Stop if you suspect a mechanical fault in the driven machine.
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 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.