Cause : UCE upper switch/UCE Phase L1 comes when there was an UCE shutdown in phase L1. This fault signifies an issue with the inverter's ability to control the voltage or current on that specific phase during operation.

The fault F025 in a Siemens Masterdrive indicates a problem with the output phase. The specific phase will be denoted after the fault code, for example, F025-L1 signifies an issue with phase L1. This fault essentially means there's a problem with the power delivered to the motor on a specific phase.

1. Phase L1 for short-circuit or ground fault (-X2:U2 - including motor).
2. Check the converter outputs for earth fault.
3. Check the CU is correctly inserted.