AdvancedMedium risk

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.

Start fault-finding

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.

Full detail — causes, the why, and common mistakes.

Likely causes

Ranked from most to least likely.

1
Deceleration ramp too fast for the load
Most likely
A high-inertia load decelerated too quickly regenerates energy back into the bus, raising voltage until it trips.
2
No / faulty braking resistor where needed
#2
Loads 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
#3
An already-high incoming supply leaves little headroom, so any regen tips it over.
4
Overhauling load driving the motor
Least likely
A 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.

Premium fault tree

The full ranked causes, test sequence and flowchart for this fault are part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Testing sequence

Work through one test at a time. Expected reading and what each result means.

Test 1 of 4

Note when it trips — on decel/stop, when lowering a load, or randomly — and read the exact code.

Expected reading

A clear pattern tied to deceleration or an overhauling load.

Your actual reading

If it passes

Decel/overhauling pattern → focus on ramps and braking.

If it fails

Random/at-rest tripping → check supply voltage and the drive itself.

Often leads toVSD trips on overcurrent / overload VSD powered up but won't start the motor

View all expected readings at once

1. Note 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.

2. Lengthen the deceleration ramp and re-test (or enable any over-voltage ride-through the drive offers).

With a slower decel it stops without over-volting.

3. Where braking is required, check the brake resistor and its circuit are present and healthy.

Correctly sized, intact brake resistor and chopper.

4. Measure the incoming supply voltage and compare to the drive's input rating.

Supply within the drive's rated input range.

Full test sequence

The step-by-step test flow with expected readings for this fault is part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Fault-finding flowchart

The same logic as a decision tree.

1
start
VSD overvoltage trip
→ step 2
2
decision
Does it trip on decel/stop or with an overhauling load?
Yes→ step 3No→ step 4
3
decision
Does a longer decel ramp stop the trip?
Yes→ step 5No→ step 6
4
result
Check incoming supply voltage and the drive itself.
5
result
Decel rate was the cause — set an appropriate ramp.
6
decision
Is a correctly sized brake resistor fitted and healthy?
Yes→ step 7No→ step 8
7
result
Check incoming supply voltage headroom.
8
result
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.

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