Return Fault On MV Switch Gear

We are facing return fault on a motor. During running condition it comes and trip the motor. This fault comes in random manner either two times in a day or one time in a whole week.

Incoming supply 6.3 KV comes to MV Panel, From MV panel goes to Converter Transformer (6.3 KV to 690V) and applied to the VFD. VFD is connectyed to the motor

From VFD Two command are going to MV panel, One is Start Command which remains high if motor is running. Second From MV panel VFD take feedback (whether breaker is On/OFF) from the Auxiliary contacts of MV breaker (Here breaker is working as Contactor). If start Command is On and Feedback signal misses, VFD generate "Return Fault".

I have checked the auxiliary contacts of MV breaker through which return fault signal is coming to VFD, They are all OK. No fault is shown by the siprotec relay of MV panel.Then why Breaker is OFF without showing any alarm on protective Relay (Siprotec)

If anyone have some solution to this problem , please help me


From VFD Two command are going to MV panel, One is Start Command which remains high if motor is running. Second From MV panel VFD take feedback from the Auxiliary contacts of MV breaker (Here breaker is working as Contactor). If start Command is On and Feedback signal misses, VFD generate "Return Fault".

I have checked the auxiliary contacts of MV breaker where return fault signal is coming to VFD, They are all OK. No fault is shown by the siprotec relay of MV panel.

If anyone have some solution to this problem , help/Guide me