What can cause an SCF2 (Impedant short circuit) fault on the ATV61 and ATV71 drives?


22 July 2022

Causes for SCF2 fault on the ATV61/ATV71 drives.

Product Line:
Altivar ATV61 and ATV71


Motor short circuit or grounding at the drives output.

Troubleshooting tips:
Check the motor wires and motor insulation with a 1KV Megger (make sure the motor is disconnected from the Drive)
Check your motor for proper grounding.  Verify a ground conductor directly between the drive and the motor. 
Check your drives switching frequency and adjust if needed.
Check your auto diagnostics mode and run the Transistor test under menu 1.10 Diagnostics.
Consider adding a load reactor, dv/dt motor filter or a sinus filter if you have a long motor cable run between the drive and the motor.

Test the VFD output by disconnecting the motor leads, turn off output phase loss, set motor control type to VF/2pts, and running the VFD at specific speeds such as 20Hz / 40Hz / 60Hz.  Measure the phase-phase output voltage across all phases for balance at each speed.  Voltage should be balanced within several volts.