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.

Technician workflow10 min read

Scope of this technical record

Step-by-step workflow for Unidrive OI.AC cases that can be caused by external output faults, held brakes, feedback instability or true power-stage problems.

Safety boundary

Secure load and motion before testing. Do not repeat starts into a suspected short or unstable feedback loop.

Unidrive OI.AC workflow route

1Mode
→
2Timing
→
3Brake / cable
→
4Feedback
→
5Output stage

The workflow separates machine and feedback causes from true output-stage faults.

Unidrive OI.AC workflow image

Unidrive OI AC workflow mode timing brake cable feedback and output stage
The workflow image keeps brake and feedback evidence ahead of power-stack replacement.

Workflow goal

The workflow identifies whether OI.AC belongs to motor/cable, machine load, brake, feedback, tuning or power stage. It prevents the common mistake of replacing drive hardware while the brake or encoder route remains unresolved.

Step sequence

Classify the control mode before any output-stage conclusion.

OI.AC workflow

StepActionStop condition
1Record control mode and trip timingMode or first event unknown
2Inspect motor/cable and brake/loadMachine boundary found
3Check feedback direction/supply/shieldingFeedback unstable
4Review motor data/tuningParameter baseline missing
5Escalate output/current feedbackExternal/feedback path proven

Output package

The completed workflow should say whether the case is safe to escalate to power-stage repair or must remain with the machine/feedback route.

Field record checklist

  • Control mode
  • Trip timing
  • Brake/load evidence
  • Feedback evidence
  • Output-stage escalation

Technical basis and reference documents

This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.

OI.AC Trip technical noteControl Techniques technical note mirror

Trip-description reference for OI.AC overcurrent context.

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 →
Evidence intake

Turn this record into a qualified service request

A repair decision is much more reliable when the request includes the exact identity of the drive, the first fault evidence and the machine condition when the symptom appeared.

  • Complete drive type code / MLFB or nameplate model
  • Fault code, fault value and first event before reset
  • When the event appears: power-up, enable, ramp, run, decel or stop
  • Motor/cable connected or isolated during the symptom
  • Visible board, option-card, module and connector identifiers
  • Previous repair history, replacement parts and repeat-failure pattern
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