Scope of this technical record
Energy-flow record linking deceleration regeneration with E.OV3 protection and brake-system decisions.
Braking components can reach dangerous temperatures and the DC bus remains hazardous after stopping.
Energy flow during stopping
When an inertial load is commanded to decelerate, the motor can return energy into the inverter DC link. Mitsubishi identifies E.OV3 when the resulting internal main-circuit DC voltage reaches the protective threshold during deceleration or stop. The path therefore starts at the mechanical process, not automatically at a damaged board.
From proof to resolution
Regeneration route
| Step | Question |
|---|---|
| Operating cycle | Does the trip track a fast stop or descending/regenerative condition? |
| Parameter proof | Does increasing deceleration time remove the event? |
| Hardware provision | Is a brake unit or regenerative converter fitted and healthy? |
| Production requirement | Must the machine retain rapid or frequent stopping? |
Why it matters commercially
A technician searching this fault is often deciding whether a failed drive needs repair or whether the system lacks adequate energy dissipation. A detailed path prevents a customer from buying a control or driver board for a brake-system or process-sizing problem.
DC-link energy path and evidence hierarchy
During deceleration, the motor and driven machine may return energy into the inverter DC link. The official E.OV3 interpretation makes this energy flow the primary hypothesis when the trip is stopping-dependent. The first evidence is therefore operational: load inertia, stopping time, brake option, frequency trend and whether the event disappears when deceleration is relaxed.
Only after that operational evidence is collected does a board-level suspicion become useful. Persistent abnormal DC-link indication inconsistent with the mechanical event, damaged brake-related hardware or a documented failed sensing path may justify internal assessment. This prevents ordinary regenerative trips from being converted into needless board repair requests.
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.