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Start by
Shubham verma
07-31-2014 08:41 AM

How to select mpcb for 3 phase motor?

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...............
07-31-2014 10:43 AM
Top #2
Gaurav garg
07-31-2014 10:43 AM
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
07-31-2014 01:01 PM
Top #3
Shubham verma
07-31-2014 01:01 PM
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.
07-31-2014 03:03 PM
Top #4
07-31-2014 03:03 PM
hi subham
selection of mpcb
2×rated current of motor
for 5hp motor 16amp mpcb are required
07-31-2014 05:20 PM
Top #5
Shubham verma
07-31-2014 05:20 PM
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.
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