VSD trips on DC bus overvoltage
The drive trips on overvoltage — usually during deceleration or stopping, when a spinning load pushes energy back into the DC bus faster than it can be absorbed.
Safety first
The DC bus holds a dangerous charge. Wait the documented discharge time and prove dead before touching internal terminals. Braking resistors get very hot.
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
Deceleration ramp too fast for the load
Most likelyA high-inertia load decelerated too quickly regenerates energy back into the bus, raising voltage until it trips.
- 2
No / faulty braking resistor where needed
#2Loads that regenerate need a brake resistor to dump the energy; if it's missing or faulty, the bus over-volts.
- 3
High or rising supply voltage
#3An already-high incoming supply leaves little headroom, so any regen tips it over.
- 4
Overhauling load driving the motor
Least likelyA load that drives the motor (e.g. lowering a weight, a fan windmilling) feeds energy back continuously.
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 when it trips — on decel/stop, when lowering a load, or randomly — and read the exact code.
A clear pattern tied to deceleration or an overhauling load.
Decel/overhauling pattern → focus on ramps and braking.
Random/at-rest tripping → check supply voltage and the drive itself.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
VSD overvoltage trip
→ step 2 - 2decision
Does it trip on decel/stop or with an overhauling load?
Yes→ step 3No→ step 4 - 3decision
Does a longer decel ramp stop the trip?
Yes→ step 5No→ step 6 - 4result
Check incoming supply voltage and the drive itself.
- 5result
Decel rate was the cause — set an appropriate ramp.
- 6decision
Is a correctly sized brake resistor fitted and healthy?
Yes→ step 7No→ step 8 - 7result
Check incoming supply voltage headroom.
- 8result
Fit/repair correctly sized dynamic braking.
Common mistakes apprentices make
- Decelerating a high-inertia load far too quickly.
- Not fitting (or checking) a braking resistor on a regenerating load.
- Overlooking an overhauling load that drives the motor.
- Ignoring an already-high incoming supply voltage.
When to stop & escalate
If the application fundamentally regenerates (hoists, large fans), the braking method should be designed for it. Persistent high supply voltage is a distribution issue to raise.
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.
Was this guide helpful?
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 powered up but won't start the motor
The drive is energised and the display is alive, but it won't run the motor. No fault may be shown — it just sits in 'ready' or 'stopped' and ignores the start command.
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.