IndustrialDriveDataDrive Board & Diagnostic Database
Multi-Brand VFD Diagnostics fault record

OUTPUT PHASE LOSS: VFD output phase loss or motor phase missing indication

The drive reports output phase loss, motor phase loss, unbalanced output current or no torque on one phase.

Meaning of the indication

The route must separate motor lead, contactor, current sensor, gate-driver command and output power device evidence.

Checking order

  1. Confirm whether the symptom follows the motor/cable or stays with the drive output phase.
  2. Inspect output contactors, terminals and motor cable continuity under safe isolated conditions.
  3. Compare current feedback evidence with actual phase condition where qualified equipment is available.
  4. Check whether a previous IGBT repair left a driver, gate resistor or phase-current feedback fault unresolved.

Suspect areas

Output terminalMotor cableCurrent sensorGate driverIGBT phase leg
Fault-specific caution

Do not run a loaded motor with suspected output phase loss; motor and power-stage damage can escalate quickly.

Diagnostic workflow

Workflow
VFD overcurrent-at-startup workflow

Overcurrent trip appears immediately at run command, during acceleration or before stable speed is reached.

Open →Workflow
VFD repeated IGBT/IPM failure workflow

Replacement IGBT, IPM or output module fails again during power-up, enable or early load testing.

Open →