ATV320 OCF trip during acceleration of a high-inertia load, what to check?
My Altivar ATV320 drive is tripping on OCF every time I try to accelerate a high-inertia load. It trips partway through the acceleration ramp. What should I check first?
An OCF (Overcurrent) fault on a Schneider Altivar ATV320 drive indicates that the drive detected excessive output current. This often occurs during acceleration of high-inertia loads, on a load step, or after a motor or parameter change. Common causes include the load being too high for the acceleration ramp, mechanical locking, or incorrect motor control parameters.
Likely causes and checks
1Inertia or load too high for the ramp
- Points to it
- The drive is detecting excessive current because the motor is struggling to accelerate a heavy load within the set ramp time.
- Check
- Lengthen the [Acceleration] ACC parameter and verify that the motor, drive, and load sizes are appropriately matched.
2Mechanical locking
- Points to it
- A mechanical obstruction is preventing the motor from turning freely, causing the drive to draw excessive current.
- Check
- With the drive locked out, manually check that the driven mechanism turns freely without any binding or jams.
3Motor control parameters are incorrect
- Points to it
- If the drive's settings do not accurately reflect the connected motor's characteristics, it can lead to overcurrent conditions.
- Check
- Verify the SET- and DRC- parameters against the motor's rating plate, specifically [Nom Motor Voltage] UNS and [Nom Motor Current] NCR. Then, run [Autotuning] TUN.
4Current limit or switching frequency setting
- Points to it
- Even with correct motor parameters and a free mechanism, the drive might still trip if the current limit is too restrictive or the switching frequency is unsuitable.
- Check
- Consider decreasing the [Current Limitation] CLI parameter or increasing the [Switching frequency] SFR parameter.
Next check: Since the trip occurs partway through acceleration with a high-inertia load, start by lengthening the [Acceleration] ACC parameter and confirming the motor, drive, and load sizing.
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