Cause: Internal Error 0 comes when communication interruption between microprocessors of the control board. The cause of this fault is faulty or damaged interconnections between microprocessors.

"InF0" fault in Schneider ATV950 drive indicate "Internal Error". This means a communication interruption between microprocessors on a control board is a critical issue that can disrupt the overall functionality of a system. 

Troubleshooting Steps:

1. Check for Physical Damage: Inspect the control board for visible signs of damage, such as broken traces, burnt components, or loose connections.
2. Verify Power Supply: Ensure the control board is receiving stable and adequate power.
3. Isolate the Issue: Try to pinpoint which microprocessors are affected by the communication interruption. This can involve using diagnostic tools or isolating component.
4. Check Communication Lines: Examine the communication lines between the microprocessors for any issues.