ATV320 SCF1 instantly on run command, after motor work: what to check?
I'm getting an SCF1 fault on my Schneider Altivar ATV320 drive. It trips instantly when I give the run command, and this started right after we finished some work on the motor. What should I check first?
An SCF1 fault on a Schneider Altivar ATV320 drive indicates a motor short circuit or grounding at the drive's output. This can occur instantly at the run command, especially after recent work on the motor or cables. The most common causes are issues with the motor cable or the motor windings themselves.
Likely causes and checks
1Motor cable damaged or shorted
- Points to it
- The drive detected a short circuit or grounding at its output, between the drive and the motor. This is common if the cable was recently moved, crushed, or exposed to moisture, and often causes an instant trip on the run command.
- Check
- Lock out the machine, wait 15 minutes, and confirm the DC bus is below 42 Vdc. Disconnect the motor cable at the drive and perform an insulation test phase-to-phase and to ground.
2Motor winding or insulation failure
- Points to it
- If the motor cable tests good, the issue might be internal to the motor, such as a winding or insulation failure. This is more likely if the motor is old, has overheated, or has been exposed to moisture.
- Check
- With the motor disconnected from the drive, insulation-test the motor windings.
3Cable capacitance or switching effects on long runs
- Points to it
- For long motor cables, capacitance or switching effects can sometimes trigger an SCF1 fault, even if insulation tests are good. The drive detects a short at its output.
- Check
- Consider connecting chokes in series with the motor and reviewing the switching frequency (SFR parameter).
4Speed loop or brake adjustment
- Points to it
- On hoisting or brake-controlled axes, an SCF1 fault can occur around brake release due to speed loop or brake adjustment issues. The drive detects a short at its output.
- Check
- Check the speed loop and brake settings, and consider increasing the [Time to restart] TTR parameter.
Next check: Given that the fault occurs instantly on the run command and after motor work, the first step should be to check the motor cable for damage or shorts. Lock out, wait 15 minutes, confirm DC bus below 42 Vdc, disconnect the motor cable at the drive, and insulation-test it phase-to-phase and to ground.
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