IndustrialDriveDataDrive Board & Diagnostic Database
Diagnostic workflow

Unidrive OI.AC Overcurrent Diagnostic Workflow

Entry symptom: Unidrive SP/M reports OI.AC or trips during enable, acceleration, load change or closed-loop instability.

Safety controls before proceeding
  • Secure moving axes and suspended loads before tests.
  • Verify DC bus discharge before output inspection.
  • Do not repeat starts into a suspected short.

Investigation sequence

1

Classify control mode

Record open-loop, closed-loop vector or servo mode and whether encoder feedback is used.

2

Record timing and load

Separate instant enable, ramp, load step and unstable running events.

3

Check external output path

Inspect motor cable, motor insulation, output terminals, brake release and mechanical load.

4

Check feedback path

For closed-loop systems, inspect encoder direction, shielding, supply and option module status.

5

Escalate power stage

If external and feedback routes are credible, inspect output bridge/current feedback evidence.

Stop conditions

  • Axis cannot be secured
  • Brake release status unknown
  • Encoder feedback unstable
  • Motor/cable cannot be isolated

Linked records

OI.AC
AC Output Overcurrent Trip

The drive has detected an AC output overcurrent event. The first route is motor/cable/load, brake release, current loop tuning, encoder feedback and output power-stage evidence.

Open →Feedback / encoder instability
Encoder Feedback Noise or Instability

The drive may be reacting to poor or noisy feedback rather than a failed output module. The route begins with encoder supply, shield/grounding, cable routing, option module and motor-data evidence.

Open →Circuit
Unidrive Output Current, Vector Control and Feedback Path

Routes OI.AC and unstable closed-loop behaviour through motor cable, output bridge, current feedback, brake release, encoder feedback, shielding and tuning context.

Open →