Scope of this technical record
Routes Unidrive Over Volts searches through DC-link level, deceleration command, regenerative load, brake resistor, brake chopper and feedback hunting before control-board repair is considered.
DC-link and braking circuits store hazardous energy and brake resistors can be hot. Secure the machine and verify discharge before any measurement or inspection.
Over Volts braking and DC-link image
Searcher intent coverage
Over Volts users are usually troubleshooting a stopping/lowering event. The answer must explain regeneration and braking evidence before board suspicion.
| Observed situation | Decision needed | Evidence that satisfies the search |
|---|---|---|
| Trip during decel | Regeneration/load inertia | DC bus trend and decel time |
| Brake resistor fitted | Brake path condition | Resistor value and chopper evidence |
| Trip in closed-loop running | Feedback hunting | Encoder trace and open-loop comparison |
What the searcher is deciding
The phrase Over Volts is simple, but the cause is often a machine-energy problem. The question is whether the DC bus rose because the load regenerated energy during stopping/lowering/unwinding, because the braking path could not absorb it, because the line was high, or because unstable feedback made the drive hunt.
A page that only says 'increase decel time' misses repair evidence. The correct route captures when the bus rises, whether a brake resistor is fitted, whether the resistor and chopper are healthy, and whether closed-loop feedback is generating unnecessary regenerative swings.
Over Volts decision table
Treat Over Volts as an event tied to machine movement.
DC-bus energy route
| Event | Likely boundary | Evidence | Next action |
|---|---|---|---|
| Trips only during deceleration | Regenerative load energy | Stop time, load inertia, bus trend | Adjust decel/brake route before board claim |
| Trips on lowering/overhauling load | Regenerative hoist/winder condition | Load direction and brake control | Prove braking path and mechanical control |
| Brake resistor fitted but trip remains | Resistor, wiring, thermal switch or chopper | Resistance value, heat marks, chopper command | Repair brake path before drive replacement |
| Trips while running closed-loop | Feedback hunting/regeneration | Encoder trace, shield, tuning, open-loop comparison | Correct feedback/tuning before bus repair |
| High bus at idle | Incoming supply or bus measurement | Line voltage and bus reading | Supply/DC measurement route |
Repair boundary
An internal drive repair becomes credible when the braking path, deceleration demand, supply level and feedback stability have been documented and the bus behaviour remains abnormal. Before that point, a replacement drive may repeat the same Over Volts trip on the first loaded stop.
For repair intake, include a photo of the brake resistor or braking unit, the load type, trip moment, deceleration time and whether the DC bus is high before motion begins.
Field record checklist
- When Over Volts appears
- DC bus behaviour before and during stop
- Load inertia/hoist/winder condition
- Brake resistor/chopper evidence
- Line voltage evidence
- Encoder/feedback stability if closed-loop
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Used for DC link over-voltage trip-family alignment.