MCCB Trip Issue

Dear electrical specialists,

Recently we encounter DB MCCB tripped few times in a day and cause heavy production breakdown.

We do not understand why MCCB trip instead of MCB and ELCB in the control panel. The MG brand MCCB was replaced and the unit was sent for diagnosis and it was found good. But hence trip continue to happen.

So we change the MCCB from MG brand to TS brand. After the change, there is a trip to one of the motor pump which was connected to an inverter. We found out there is wiring loose and tightened it. Since then there is no more trip to the MCCB though we continue to use TS brand MCCB.

We do not understand why motor wiring loose can cause trip to the MG MCCB but not the TS although both are the same load. Our consultant also checked the DB load is normal.

The german vendor who built the control panel suspect inverter can cause trip to MCCB should motor wiring loose.

Can anyone explain the theory of inverter that can cause trip to MCCB when motor wiring loose?

please advice,

Regards,

Jason