Scope of this technical record
This record handles Unidrive OI.AC overcurrent trips by separating output-current protection from motor cable faults, braked or stalled load conditions, closed-loop feedback problems, motor-data issues and true output-stage faults.
Secure the driven machine before testing. A closed-loop Unidrive axis, hoist or winder can move unexpectedly if command, brake or feedback evidence is wrong. Do not repeatedly reset into a suspected short, ground fault or held-brake condition.
OI.AC overcurrent route
Closed-loop and brake evidence must be checked before a power-stage conclusion.
OI.AC overcurrent machine route image
Searcher intent coverage
OI.AC users need machine evidence: motor map, brake, feedback and load timing. The fault label alone is not enough to justify power-stack repair.
| Observed situation | Decision needed | Evidence that satisfies the search |
|---|---|---|
| Trip at enable | Motor/output or current feedback boundary | Disconnected-output result and motor data |
| Trip at brake release | Brake/load problem | Brake contactor and shaft-release evidence |
| Closed-loop instability | Feedback route | Open-loop comparison and encoder cable evidence |
Field interpretation of OI.AC
OI.AC should be treated as a route into the output-current system, not as proof that the drive stack has failed. The first question is timing. A trip at enable points to motor cable, output device, pre-existing short, incorrect motor connection or a brake/load state that prevents current from building normally. A trip during acceleration points toward ramp, load, motor data, current limit, brake release or feedback direction. A trip during loaded running may point to mechanical overload, intermittent cable damage, feedback noise or thermal drift in the current path.
Closed-loop installations need special discipline. If the encoder direction, feedback scaling, shield, option module or motor data is wrong, the drive can command excessive torque while trying to correct a position or speed error. The symptom may look like a power fault even though the first cause is feedback quality or machine setup.
Fast triage before hardware replacement
The repair route begins outside the drive. Record the trip timing, machine state and brake state, then prove that the motor and cable are not shorted or grounded. Only after the external output path and feedback path are credible should the current feedback, gate-drive or output module boundary become the leading suspect.
A good field note states what changed when the motor/cable was isolated, whether the machine can rotate freely, whether the brake released, and whether the fault follows open-loop or closed-loop operation. Without those details, the repair desk cannot distinguish a failed drive from a drive correctly protecting itself.
OI.AC triage table
| Trip timing | Likely first boundary | What to record |
|---|---|---|
| Immediately on enable | Output cable, motor connection, power stage, brake/load locked | Motor disconnected result, phase-to-phase checks, brake command and mechanical free movement |
| During acceleration | Ramp, current limit, motor data, load torque, brake release | Ramp value, load condition, motor nameplate data, brake release proof |
| When switching to closed loop | Encoder direction, feedback option, shielding, tuning | Encoder type, option module, direction check, cable route and noise exposure |
| Only under load | Mechanical overload, intermittent cable, torque demand | Actual machine load, cable movement, temperature and production condition |
| Still present after proven external isolation | Current feedback, gate-drive, output stage | Static output checks, board photos, previous repair history |
Repair boundary
Escalate to board or power-stack work only after field causes are removed from the evidence chain. The strongest internal-drive evidence is a repeated OI.AC with the output path safely isolated, abnormal static output measurements, visible damage, current-sense irregularity, or repeat trips that do not follow motor, cable, brake or feedback changes.
Do not close the case after a simple reset. The close-out note should identify the corrected boundary: motor/cable insulation, brake release, encoder/option module, motor-data/tuning, mechanical overload, current feedback or output-stage hardware. That record prevents the same machine from returning with the same trip after a drive replacement.
Field record checklist
- Exact Unidrive type code, frame and control mode
- Trip timing: enable, acceleration, load, deceleration or closed-loop transition
- Motor and cable isolation result recorded with the drive disconnected correctly
- Brake release and mechanical free-movement evidence
- Encoder/feedback option type, cable route and direction check
- Motor nameplate data, ramp/current-limit settings and prior repair history
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Linked workflow record for output-current and feedback boundary checks.