Scope of this technical record
DC bus overvoltage trips that appear during deceleration, stopping, lowering or other regenerative machine states.
DC-link and braking hardware can remain hazardous and hot after shutdown. Work must follow qualified isolation and rated braking-component procedure.
Deceleration overvoltage route
Deceleration overvoltage is treated as energy management before a board-level claim.
DC-bus overvoltage deceleration map
The useful interpretation
A deceleration overvoltage usually means the motor is returning energy into the DC link faster than the drive can absorb, dissipate or return it. That makes the fault a system-energy problem before it is a board-replacement problem.
The route starts with machine timing and parameter configuration: stop mode, ramp-down time, overvoltage stall/control, braking enable and load direction. Then it moves to brake resistor wiring, chopper hardware, DC-bus feedback and common-DC-bus interaction.
Evidence map
If lengthening the ramp removes the trip, braking capacity or machine inertia is implicated. If the trip remains with gentle ramps, suspect bus feedback, incoming supply condition or system-level DC-link interaction. If braking hardware is fitted but never heats or shows no switching evidence, chopper/resistor routing becomes the priority.
Overvoltage during deceleration route
| Evidence | Likely boundary | Next step |
|---|---|---|
| Trip only on fast stop | Ramp/load inertia | Review decel time and stop mode |
| Brake resistor fitted but no effect | Chopper/resistor path | Check wiring, resistance and enable |
| Trip on lowering or unwinding | Regenerative load | Review braking or regenerative front end |
| Common DC bus present | System energy exchange | Check other drives returning energy |
| Measured bus disagrees with panel | Bus feedback | Inspect sensing path |
What makes the page different
Most overvoltage explanations say to increase the deceleration time or add a braking resistor. This page also covers the cases that matter to service shops: resistor installed but ineffective, chopper transistor not switching, feedback error, braking duty mismatch and common-DC-bus energy transfer.
Field record checklist
- Fault timing during decel/stop/lowering
- Ramp-down and stop-mode settings
- Brake resistor value and wiring
- Internal or external braking unit status
- Common DC bus or regenerative unit presence
- Measured bus evidence if qualified
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Linked workflow for DC-link overvoltage triage.
Diagnostic workflow
Drive trips on DC bus overvoltage when stopping, lowering, braking or reducing speed.
Drive reports undervoltage/precharge fault, blows input fuses or shows no-display symptoms with uncertain DC-link charging.
Turn this record into a qualified service request
A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.
- Complete drive type code / MLFB or nameplate model
- Fault code, fault value and first event before reset
- When the event appears: power-up, enable, ramp, run, decel or stop
- Motor/cable connected or isolated during the symptom
- Visible board, option-card, module and connector identifiers
- Previous repair history, replacement parts and repeat-failure pattern