IndustrialDriveDataDrive Board & Diagnostic Database
Diagnostic workflow

Danfoss VLT Deceleration Overvoltage Workflow

Entry symptom: Danfoss VLT trips on overvoltage during deceleration, stop or load lowering.

Safety controls before proceeding
  • Regenerative loads can move unexpectedly.
  • High DC-link voltage is hazardous.
  • Do not bypass brake protection.

Investigation sequence

1

Confirm event timing

Verify the trip is linked to deceleration or lowering rather than steady input overvoltage.

2

Review ramp

Increase deceleration time as a controlled diagnostic where process safety allows.

3

Check brake path

Inspect braking resistor, chopper setting and wiring where fitted.

4

Classify load

Record inertia, vertical load or regenerative process condition.

5

Measure supply

Check input line voltage and DC-link behaviour under qualified procedure.

Stop conditions

  • Load cannot be controlled safely
  • Brake resistor overheats
  • DC-link discharge cannot be verified

Linked records

Overvoltage / DC link high
DC Link Overvoltage During Deceleration

Regenerated energy is raising the DC-link voltage faster than the ramp/brake path can handle it.

Open →Circuit
Danfoss VLT Input Phase and DC-Link Path

Routes alarm 4 and deceleration overvoltage through line phases, fuses, contactor, rectifier, DC-link ripple, high line voltage and braking energy paths.

Open →