Rating of MCCB for 300A,285kW, 480V,60Hz motor

[Babateen Salem S.]

we have 285kw motor 300A,480V running continues and the existing ABB MCCB is TH5400A,
twice time the MCCB tripping and we found that the phase B was melted inside the MCCB during normal operation and no short circuit was occurred in the power cable and in the motor side
ABB MCCB data TH%400 PR221DS-I In400, 3p ,50KA, instantaneous Short Circuit I 3600A
The size of the MCCB are OK or Not?

Thank
Salem

 

[Besoeker]

we have 285kw motor 300A,480V running continues and the existing ABB MCCB is TH5400A,

I think there might be something wrong with your figures.
At rated load, a 285kW 480V motor would take about 425A assuming 0.85 power factor and 95% efficiency.
It suggests that the MCCB isn't rated for even the continuous motor current.

 

[Babateen Salem S.]

Sory, the motor rating 185KW not 285KW

 

[zog]

we have 285kw motor 300A,480V running continues and the existing ABB MCCB is TH5400A,
twice time the MCCB tripping and we found that the phase B was melted inside the MCCB during normal operation and no short circuit was occurred in the power cable and in the motor side
ABB MCCB data TH%400 PR221DS-I In400, 3p ,50KA, instantaneous Short Circuit I 3600A
The size of the MCCB are OK or Not?

Thank
Salem

How about some test results for the cable, motor, and breaker?

 

[Besoeker]

Sory, the motor rating 185KW not 285KW

Ah, OK.
Then a 400A breaker would be comfortably rated for the continuous duty.
If I understand your original post correctly, you have twice had the same problem on the B phase inside the breaker?
If so, this could indicate either a bad breaker contact or loose connections on that phase.
Have you measured the currents in the three phases during normal operation?