Yaskawa A1000 OC Fault — Overcurrent
The OC fault on the Yaskawa A1000 high-performance vector drive means output current has exceeded approximately 200% of rated drive current (instantaneous trip). The drive shuts down immediately. The A1000 is Yaskawa’s medium-heavy-duty drive used in demanding applications including conveyors, compressors, fans, and pumps.
A1000 OC Fault Variants
| Code | Phase | Description |
|---|---|---|
| OCA | Acceleration | Overcurrent during speed ramp-up |
| OCb | Deceleration | Overcurrent during speed ramp-down |
| OCC | Constant speed | Overcurrent at steady state |
| OC | At stop | Overcurrent at zero speed (short circuit suspect) |
Jump to Fix
Common Causes
| Cause | Fault Variant | Likelihood |
|---|---|---|
| Acceleration ramp too aggressive | OCA | Very High |
| Mechanical load jam or seized bearing | OCC | High |
| Deceleration ramp too fast (high inertia load) | OCb | High |
| Incorrect V/f or vector control tuning | OCA | Medium |
| Short circuit in motor cable or motor | OCA / OC | Medium |
| Failed output IGBT | OCA | Medium |
| Load demand spike (starting against back-pressure) | OCA | Medium |
Step-by-Step Diagnosis
Step 1 — Identify the fault type Check the A1000 fault log (U2-01 through U2-10 store recent faults with conditions):
- OCA: increase acceleration time (C1-01) — start with 2x the current setting
- OCb: increase deceleration time (C1-02) or enable braking resistor if high-inertia load
- OCC: check for mechanical jam, load spike, or insufficient torque limit setting
Step 2 — Extend ramp times (OCA / OCb)
- C1-01 (Acceleration Time 1): default 10 sec — try 20–30 sec for heavy loads
- C1-02 (Deceleration Time 1): increase if high-inertia loads cause OCb
Step 3 — Check mechanical system
- With power off: rotate the load by hand
- Any binding, stiffness, or inability to turn = mechanical issue causing stall
Step 4 — Run motor auto-tune
- A1000 auto-tune: T1-01 = 1 (Rotational auto-tune — motor spins)
- Auto-tune optimizes vector control for the specific motor
- Eliminates excess magnetizing current that causes OCA
Step 5 — Megger test motor and cable
- With drive output disconnected: megger each phase to ground
- Below 1 MΩ: insulation fault — may read as overcurrent
Step 6 — Check IGBT output stage
- Power off — wait 5 minutes for DC bus discharge
- Diode test from U, V, W to DC+ and DC-
- Short in either direction = failed IGBT — drive repair required
Key A1000 Parameters for OC Faults
| Parameter | Function | OC-Relevant Setting |
|---|---|---|
| C1-01 | Acceleration Time 1 | Increase for OCA |
| C1-02 | Deceleration Time 1 | Increase for OCb |
| L3-01 | Stall Prevention — acceleration | 1 (enabled) for variable loads |
| L3-04 | Stall Prevention — constant speed | 1 (enabled) |
| L3-06 | Stall Prevention — deceleration | Adjust for high-inertia loads |
| E1-01 | Input voltage setting | Must match actual supply |
| T1-01 | Auto-tune selection | Run after new motor or OC fault |
A1000 vs V1000 OC Comparison
| Feature | V1000 | A1000 |
|---|---|---|
| Frame size | 0.5–20 HP | 1–600+ HP |
| Torque control | V/f + Basic closed loop | Full closed-loop vector |
| OC trip level | 200% rated | 200% rated |
| Braking resistor | Optional | Standard on most frames |
Pro tip: The A1000 supports S-curve acceleration (C2-01 through C2-04) which smooths the ramp profile. Enabling S-curve significantly reduces OCA faults on applications with high starting torque requirements like conveyors or compressors.
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