Screw compressor MPCBs keep failing , Please Help !!

[Mohammedi Seddik]

I can only presume the compressor being such a large one is on a skid with its own control circuit? If so I cannot see a problem as it will have its own overload protection and that MCCB is just protecting the cable to the compressor.

I can only suggest replacing it with some motor rated HRC fuses and see if they a more robust solution.

But without seeing it everyone is guessing.

This MCCB is for motor protection , since there is nothing between the motor and the breaker but the 3 Delta/star contactors, what i'm going to do now is replacing the bad 630A breaker with a another 1250A breaker, i think the problem is just simple as the breaker can't handle the motor espacialy during those power interuptions. we'll see how that goes , and if the new 1250A breaker fails too, i'll just say goodbye to my job hhhhhh

 

[Rocboni]

Can the supply cable handle this increase in mccb size?

 

[Marvo]

Does the unit have an unloader? If so has it been thoroughly tested? A sticky unloader valver could be causing locked rotor on restart which could correspond to the overcurrent failure message. I'm not sure why that would destroy the MCCB though....

Rather than whacking a 1250A MCCB in maybe go with another 630A with ba higher fault current KA rating.