can any body tell me how to select mpcb for 3 phase motor.........and also for the star delta motor and does by using vfd current rating will going to change...............

Hello Shubham

The calculation for value is same as in case of MCB. However, MPCB comes with some additional features and its current is adjustable unlike MCB. So just calculate the value and adjust is from the front panel provided on it. The calculation is as follows:
Load=VI cosQ,
where value of CosQ is given on motor plate. However if not specified consider it 0.8
V= 415V
Load in KW

Thanks dear but i am using the same formula but i just want to confirm that what will be the effect of starting current of motor on mpcb.As we know intially motor will more current than the normal current.

For exapmle:motor of 5 hp will have different current during starting and after stabilization.

hi subham
selection of mpcb
2×rated current of motor
for 5hp motor 16amp mpcb are required

thanks dipak

I have one powerpack motor of 7.5 hp in which i have selected 15 amp current but mpcb is not getting trip.