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Need an equation to figure out Power correction

Discussion in 'General Electronics Chat' started by Bree Bree, Dec 25, 2017.

  1. Bree Bree

    Bree Bree New Member

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    I try looking on internet and my school book. I'm having difficultly finishing a problem. The question is below: I only want the equation to get this going. I can do the rest on my own.

    Based upon the power factor, determine the value of the capacitors needed in each case to bring the power factor to the following values. Be sure to show your calculations.
    1. Power Factor = 0.85
    2. Power Factor = 0.95
    3. Power Factor = 1.00
     
  2. dr pepper

    dr pepper Well-Known Member Most Helpful Member

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    Welcome.
    Hi Bree we need to know more info like voltage & current.
    If you have a Pf of 1 then you wouldnt need any capacitance as your load must be non reactive.
     
  3. Bree Bree

    Bree Bree New Member

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    Given: f = 1000 Hz, R = 680 Ω, L = 100 mH, Vrms = 5 V
     

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  4. dave miyares

    Dave New Member

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  5. boro3

    boro3 New Member

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    where you schould put the capacitor ?
    in serie with L?
    or parralel?
    its value depends on where the capacitor is.

    for power factor 1 and c in serie with L (if Power factor is 1, you only got ohm resistance)

    Zc,l= j(wL-1/wC)=0, now you can calculate the C

    first you calculate the Phase Phi with arccos(Power Factor).
    Then you need the total Impedanz or Admittance (depends on where you put the C).
    Then you can calculate with arctan(Phi)=Imaginary/Real
     
    Last edited: Dec 25, 2017
  6. Bree Bree

    Bree Bree New Member

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    The capacitor would be in parallel.
     
  7. Ratchit

    Ratchit Well-Known Member

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    You don't need an equation, you need an understanding of what PF is. PF correction is the same a making a resonant circuit. Specifically, XL has to equal XC to get a PF of one. Given the inductive reactance, can you come up with a capacitor value to give an equal capacitive reactance at the same frequency?

    Ratch
     
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