Screw compressor MPCBs keep failing , Please Help !!

Mohammedi Seddik · Mar 18, 2018

Rocboni said:
Can we get the part number of the MPCB, it could be a standard MCCB

here it is :

[ElectriciansForums.net] Screw compressor MPCBs keep failing , Please Help !!

LeeH · Mar 18, 2018

That is an MCCB FYI.

Mohammedi Seddik · Mar 18, 2018

Rocboni said:
Can we get the part number of the MPCB, it could be a standard MCCB

here it is :

Mohammedi Seddik · Mar 18, 2018

LeeH said:
That is an MCCB FYI.

So do you think using this with a 250kw motor is a wrong idea ??

LeeH · Mar 18, 2018

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.

Mohammedi Seddik · Mar 18, 2018

LeeH said:
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 · Mar 18, 2018

Can the supply cable handle this increase in mccb size?

Marvo · Mar 18, 2018

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.