VFD-rated motor cable
Price this when overcurrent or overload faults trace to damaged output wiring.
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 {#most-likely-cause}
| 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 {#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 |
Technician Tips
When diagnosing VFD faults, always check the drive’s fault history before resetting. Modern drives store the last 5-10 faults with the drive state at the time (running, accelerating, decelerating, stopped). An overcurrent fault that occurs only during acceleration points to incorrect motor data or mechanical binding. The same fault during deceleration suggests regeneration issues. A ground fault that clears after disconnecting the motor and returns when reconnected means the motor or cable insulation has failed.
Prevention: Schedule annual infrared scanning of drive cabinets. Loose power connections and failing capacitors produce heat long before they cause faults. A 5-minute scan can prevent hours of unplanned downtime.
Need Replacement Parts?
Before ordering, match the drive part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
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.