Scope of this technical record
Step-by-step Altivar ATV61 / ATV71 workflow for OCF and SCF output-side cases, separating settings/load, motor/cable, transistor-test and drive-side power-stage evidence.
This workflow assumes qualified industrial-drive service. If insulation testing, output isolation or internal bridge checks cannot be performed safely, stop and collect identity evidence instead of repeating starts.
OCF / SCF workflow route
The workflow turns short fault codes into a field-to-bench evidence package.
Workflow outcome matrix
The workflow must end in a clear action: field correction, controlled re-test, workshop repair evidence or replacement planning.
| Evidence outcome | Next action | Avoid |
|---|---|---|
| Settings/load issue | Correct commissioning or machine condition | Power-board replacement |
| Motor/cable fault | Repair external output path | Another powered start |
| External proof clean and bridge suspicious | Prepare workshop repair evidence | Full-power test without driver checks |
Workflow objective
The workflow is built to prevent two common mistakes: treating OCF as a guaranteed bad board, and treating SCF as a resettable nuisance. Both faults can destroy hardware if the technician repeats powered starts without identifying whether the problem is machine-side, cable-side or drive-side.
The sequence below is deliberately narrow. It only covers the OCF/SCF output fault cluster. OSF/USF voltage faults and command-reference issues belong to different paths.
Step sequence
Run the workflow in order. Do not skip directly to power-board diagnosis because a previous repairer replaced a module, and do not stop at parameter checks when the trip is an instant SCF.
ATV61 / ATV71 OCF-SCF workflow
| Step | Action | What a good answer proves |
|---|---|---|
| 1 | Preserve fault evidence before reset | Exact code, first fault, timing and operating state are known |
| 2 | Classify timing | Enable, first PWM, ramp, load, brake release or after repair |
| 3 | Check motor data and machine load for OCF | Settings/load are plausible or corrected before internal work |
| 4 | Prove motor/cable/output path for SCF | Insulation, terminals and output accessories are documented |
| 5 | Use transistor/static checks only after safe isolation | Drive-side bridge suspicion is based on evidence, not assumption |
| 6 | Review gate-driver and current-feedback boundary | A module will not be powered without driver/root-cause proof |
| 7 | Choose field correction, workshop repair or replacement | The next action matches the proven boundary |
Decision table
The practical outcome should be one of four actions. The page should never leave the technician with only “contact support.” It should tell them what evidence changes the next move.
Outcome after workflow
| Evidence outcome | Likely next action | Do not do this |
|---|---|---|
| Motor data or ramp is wrong | Correct commissioning/settings and re-test under controlled load | Replace power board first |
| Brake/load is held | Fix machine-side release or load issue | Increase current limit blindly |
| Motor/cable insulation is poor | Repair cable/motor/output installation | Fit another drive or module |
| External path proven and bridge test suspicious | Prepare workshop power-stage evidence | Full-power test without driver checks |
| Fault follows previous repair | Audit gate-driver/current-feedback and root cause | Install another IGBT as a diagnostic tool |
Evidence package for the repair bench
A bench technician needs more than the fault label. The package should say how the fault appeared in the field, what external evidence was proven, what settings were checked, what board or module work has already been done and what stopped further powered testing.
- Fault queue photos before reset
- Motor nameplate and key motor-control values
- Load/brake/ramp evidence for OCF
- Insulation and output-terminal evidence for SCF
- Static/transistor-test observations if performed safely
- Board/module label photos and previous repair notes
Field record checklist
- First fault preserved
- Timing classified
- Settings and load checked
- Motor/cable proved
- Static/driver boundary documented
- Outcome selected
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Used to anchor OCF around hardware current limitation, motor data, high inertia, excessive load and mechanical blockage.
Used to anchor SCF1 around drive output short/grounding, motor cable checks, motor insulation and transistor test routing.
OEM programming and fault-reference context for Altivar 71 diagnostic pages.
OEM installation and wiring context for safe output and motor-cable evidence collection.
Linked records
The drive has detected current beyond the permitted boundary. The first split is mechanical load, motor/cable condition, acceleration/current-limit setup and output-stage evidence.
The route begins at output cable, motor insulation, output-connected devices and the inverter power stage. It should not be treated as a keypad or control-terminal fault.
Routes OCF and SCF evidence through motor cable, motor insulation, output terminals, optional output devices, IGBT bridge, current detection and gate-driver integrity.
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