F7900 fault in siemens sinamics V90 drive indicates the Motor is blocked or the speed controller is at its limit. This means the drive has been outputting maximum torque for too long without the motor reaching the target speed, indicating a mechanical jam or disconnected encoder.
Cause:
The servo motor has been operating at the torque limit longer than 1s and below the speed threshold of 120 rpm. This signal can also be initiated if the speed actual value is oscillating and the speed controller output repeatedly goes to its limit.
Remedy:
- Check whether the servo motor can rotate freely or not.
- Check the torque limit.
- Check the inversion of the actual value.
- Check the motor encoder connection.
- Check the encoder pulse number.
