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Power Factor Calculation

  1. Dec 28, 2011 #1
    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. jcsd
  3. Dec 28, 2011 #2

    NascentOxygen

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    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?
     
  4. Dec 29, 2011 #3
    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.
     
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