Scope of this technical record
E.OC1 Startup Workflow for qualified repair triage.
Only qualified personnel should implement any electrical test; high-voltage discharge and isolation are mandatory.
Purpose
This workflow converts the official E.OC1 definition into a stop/go diagnostic sequence. Begin by recording whether the trip is immediate, ramp-related or load-dependent; preserve prior repair evidence and do not reset repeatedly.
Investigation logic
The first separation is external: motor cable, motor insulation and mechanical load. Once those are excluded by qualified procedure, the investigation crosses into the output bridge, isolated driver rails and six-channel gate-drive comparison documented in the circuit records.
Completion and stop conditions
The unit is ready for controlled test only when the suspected cause has been removed, protection remains operational and channel/supply evidence is coherent. Recurrence or unexplained asymmetry ends the test and triggers specialist assessment.
Investigation stages for an acceleration trip
Begin with the fault record, exact model and moment of the trip. Establish whether the fault followed a parameter change, motor replacement, cable work, mechanical jam, long acceleration demand or previous internal repair. Under qualified procedures, determine whether the external motor/cable/load branch remains responsible before turning to the inverter output stage.
When the trip is immediate and persists after external causes have been responsibly excluded, capture photographs and markings for the power module and driver board, document any visible damage and avoid repeat starts. A replacement decision is credible only after the companion driver and supply path are included in the assessment.
E.OC1 branch worksheet
| Observation | Most relevant branch | Avoid |
|---|---|---|
| Trip begins after increased acceleration demand | Parameters/load/inertia | Blind board purchase |
| Trip clears when external branch is isolated | Motor/cable/application | Replacing power stage |
| Immediate repeat after module repair | Output module plus gate-drive path | Unprotected repeated testing |
| Visible flash or destroyed power section | Workshop evaluation | Re-energising the unit |
Practical branching record
A competent workflow records observations before making a replacement decision. First capture the displayed trip and operating instant. Next identify whether the fault can occur with the motor disconnected under manufacturer-approved conditions, whether deceleration/braking conditions are relevant, and whether prior module or board work was performed. Only after these branches are documented should the investigation move to board-level evidence.
The value of this sequence is that identical-looking trips can have entirely different root causes. An acceleration overcurrent may come from an output short or mechanical demand; a regenerative overvoltage may be caused by deceleration energy and braking configuration; a repeated immediate trip after output-stage repair may justify analysis of gate-drive or feedback circuitry.
Workflow result categories
| Finding | Interpretation | Next controlled action |
|---|---|---|
| Fault clears after external circuit is isolated | Investigate motor, cable or application side | Do not replace internal board on that evidence alone |
| Fault persists without external cause | Internal stage becomes credible | Preserve fault log and request board/module assessment |
| Fault depends on stopping profile | Regenerative energy path is relevant | Review deceleration/braking design before board work |
| Recent module replacement and repeat trip | Companion damage is possible | Verify driver/supply/protection before further power testing |
Stop conditions for a field technician
Stop further attempts when there is visible power-stage damage, a repeat protective trip with external causes excluded, unstable control supplies, evidence of carbonisation or flashover, or uncertainty about DC-bus discharge and safe isolation. Repeated reset-and-run attempts can convert a repairable board problem into a destroyed power module and collateral control-board damage.
A useful escalation request contains the exact model, trip history, whether the trip occurs before or after output command, motor/cable test status, brake-unit details where relevant, and clear photographs of affected board and module markings. This turns a vague fault inquiry into a diagnostic case that a specialist can evaluate.
Technical basis and reference documents
This is an independent editorial technical reference. Original manufacturer documentation remains controlling for installation, repair and commissioning decisions.
Official FR-A700/FR-A740 operating, parameter and protective-function reference.
Circuit-function mapping prepared from reviewed drawing records; original schematic files are not redistributed.
Linked records
Official FR-A700 protection logic activates E.OC1 when output current reaches or exceeds approximately 220% of rated current during acceleration. The investigation must separate load/ramp causes from output short circuits and internal driver or power-stage damage.
Maps the matched isolated drive stages, gate resistors/clamp paths and feedback connections visible across reviewed 7.5, 15 and 37 kW sheets.
A circuit-derived map of the FR-A740-37KW DB1 supply sheet: rectified input, flyback conversion, feedback regulation, ±15 V / +24 V services and isolated driver rails.