VFD-rated motor cable
Price this when overcurrent or overload faults trace to damaged output wiring.
Allen Bradley PowerFlex 700 F7 Fault — What It Means
Fault F7 on the Allen Bradley PowerFlex 700 AC drive indicates motor overload — the drive’s electronic overload protection (OL) has detected sustained overcurrent to the motor beyond the programmed FLA rating. The PowerFlex 700’s thermal model accumulates an overload count; when it reaches 100%, F7 trips and the drive shuts down to protect the motor windings from thermal damage.
Common Causes
- Mechanical overload on the driven equipment — A jammed conveyor, failed bearing, or excessive process load forces the motor to draw more current than its FLA rating allows.
- Motor overload parameters set incorrectly — Parameter 33 (Motor NP FLA) must match the motor nameplate amps exactly. A value set too low will cause premature F7 trips under normal load.
- Insufficient cooling on the motor — A motor running hot due to poor ventilation, blocked airflow, or high ambient temperature draws more current as winding resistance increases.
- Ramp times too short — Acceleration time set too fast forces high inrush current on every start, accumulating thermal count quickly.
Step-by-Step Fix
- Check for mechanical overload — Inspect the driven equipment for jams, seized bearings, or excessive load. Jog the motor uncoupled from the load. If F7 doesn’t trip uncoupled, the load is the problem.
- Verify motor FLA parameter — Check Parameter 33 (Motor NP FLA) in the PowerFlex 700. It must match the motor nameplate full-load amps exactly. Adjust if incorrect.
- Monitor motor current — Use Parameter 2 (Output Current) during operation to confirm actual amps. If current consistently exceeds motor FLA, the load is oversized for the motor.
- Extend acceleration time — Increase Parameter 140 (Accel Time 1) to reduce inrush current during starts. Also check Parameter 141 (Decel Time 1) for similar issues during braking.
- Reset and restart — Press Stop/Reset on the HIM or toggle the reset input. Confirm motor current stays below FLA on the next run cycle.
Parts Often Needed
| Part | Notes |
|---|---|
| Motor (if windings damaged by sustained OL) | Verify winding resistance before replacement |
| Driven equipment bearings | Replace if seized bearing was root cause |
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.
When to Call a Pro
If F7 trips under no-load conditions with correct parameters, the drive’s current sensing circuit may have failed. Rockwell Automation authorized service handles internal diagnostics.