Power Factor Calculation

1. Dec 28, 2011

ssana

Dear all,

I have one 22KW motor.
I want to know how much Kvar i need to install for it.
According to my information, i need to check no load current of motor (it is taking 10 ampere at no load), and than take 90% of no load current (90% of 10 ampere is 9 ampere), so install capacitor that can take maximum 9 ampere current (6 kvar capacitor takes 9 ampere current).
So 6 Kvar is suitable to install in 22KW motor.
Am i calculating in correct way?

Last edited: Dec 28, 2011
2. Dec 28, 2011

Staff: Mentor

I can't help with your question, but I was looking at your figure of 9A for 6kVAR. This implies a supply voltage of 667v. Perhaps I am not doing this right.

This is a 3 phase motor, is it? Maybe that 6kVAR is a set of capacitors drawing 2kVAR per phase? Seems an odd way to rate it, if it is, summing the phases. But the figure of 2kVAR at 9A would give a phase voltage of 220v which might be more likely.

So what is your phase voltage there?

Do you have a table of kVAR vs. current for power factor correction capacitors? If so, do the kVAR figures all turn out to be exact multiples of 3?

3. Dec 29, 2011

ssana

Dear NascentOxygen,
Using three phase formula,
Power = Voltage x Current x √3
Power = 380V x 9A x 1.732
Power = 5923 VA
OR
Power = 5.923 KVA
Approximately 6 KVA

Hope that this will helpful to you.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook