Record the exact code and drive model first. Then note whether the trip happens on START, during acceleration, at steady speed or after a process change. These details help separate loading, parameter and motor-side faults.
Start with the symptom
The pattern matters. Keep the equipment record and do not make repairs from a symptom alone.
| Observed symptom | Possible fault area | Evidence to collect |
|---|---|---|
| Trip during acceleration | High-inertia load, short ramp, incorrect motor data | Drive model, code, speed and recent parameter history |
| Trip at constant speed | Overload, mechanical binding or unexpected process demand | Load trend, drive current trend, motor rating |
| Trip after maintenance | Parameter changes, cable or motor reconnection | Approved change log, motor nameplate, wiring records |
| Overcurrent with earth-fault indication | Possible motor cable or winding insulation issue | Exact fault event and specialist inspection report |
What may be happening
Read the manufacturer fault description, not only the two-letter code
Different drives use similar-looking codes for different conditions. For example, Schneider Electric identifies OCF as an overcurrent fault on certain Altivar models. ABB manuals can distinguish overcurrent, earth leakage and short-circuit events. Correct interpretation requires the exact model and firmware documentation.
Trip timing is one of the best clues
A drive that trips while accelerating can be facing a motor or load that cannot follow the requested ramp. A drive that trips only at a certain process point may be seeing changing mechanical demand. These clues guide further evidence collection but are not proof of one cause.
Avoid copying a setting from another installation
Motor frequency, rated voltage, current and speed must match the actual motor and application. Protection thresholds, acceleration and current limits should not be increased simply to make a trip disappear. Any parameter change needs authorized engineering approval and a validated test plan.
Questions that help narrow the fault
These are questions to discuss with the authorized maintenance team. Use existing logs and approved records where possible.
- What is the exact VFD manufacturer, model and fault code?
- At what speed and operating step does the fault appear?
- Was the motor, cable or load changed recently?
- Do the recorded motor parameters match the nameplate?
- Is there an earth-fault or phase-loss event in the log?
What to do next
Keep the trip record. It is diagnostic evidence. Use the drive manual and machine history before concluding that the inverter, motor or load needs replacement.
Frequently asked questions
Does an OC fault mean the VFD IGBT is damaged?
Not necessarily. A load issue or motor data mismatch can cause overcurrent faults. Specific drive diagnostics are needed to distinguish causes.
Should I increase current limit to stop tripping?
Not without an approved engineering review. A higher limit can remove protection from an unresolved fault.
Technical references
Use these for background. Refer to the manual and approved instructions for the actual equipment model.
Record your fault symptoms
Electrical Doctor can collect equipment information and prepare a preliminary fault summary. It does not authorize a repair or switching operation.
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