IndustrialDriveDataDrive Board & Diagnostic Database
Input rectifier / DC-link

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.

Functional path

L1/L2/L3 input
Fuses / contactor
Rectifier
DC-link capacitors
Brake chopper
Brake resistor

Diagnostic signals and checkpoints

Alarm 4Phase-to-phase input voltageDC-link overvoltage timingBrake resistor continuityPlant line sag

Technician notes

  • A phase-loss alarm must be measured at the drive input terminals.
  • Deceleration overvoltage requires load inertia and brake-path evidence.