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How to calculate power

  1. Jan 18, 2016 #1
    1. The problem statement, all variables and given/known data
    I need to calculate the power given the RMS values for voltage and current.

    208 V line to line was put into the system. I measured the following data:

    VA magnitude (v) = 119.9
    VA angle (degrees) = 0
    IA magnitude (A) = 12.1
    IA angle (degrees) = -48.4

    VB magnitude (v) = 119.5
    VB angle (degrees) = -124.4
    IB magnitude (A) = 12.2
    IB angle (degrees) = -167.7

    VC magnitude (v) = 119.2
    VC angle (degrees) = 117.3
    IC magnitude (A) = 12
    IC angle (degrees) = 72.2

    I believe the VA and IA values are the RMS values for voltage and current. I was given that VAN (rms) is about 120 (V) which is what was measured for the VA magnitude.

    I need to fill out the table shown below.
    mt5xyd.jpg
    α, VA'N, VB'N and VC'N can be ignored, I have the values for those columns.

    2. Relevant equations
    PA = VA*IA
    Ptotal = PA + PB + PC
    3. The attempt at a solution

    This is what I think the answer is for each column and how I got it
    IA = 12.1 (A) from measured data
    VAN = 119.9 (V) from measured data
    PA = VA*IA = 119.9*12.1 = 1450.79 (w)

    IB = 12.2 (A) from measured data
    VBN = 119.5 (V) from measured data
    PB = VB*IB = 119.5*12.2 = 1457.9 (w)

    IC = 12 (A) from measured data
    VCN = 119.2 from measured data
    PC = 1430.4 (w)

    Therefore, Ptotal = PA + PB + PC = 1450.79 + 1457.9 + 1430.4 = 4339.09 (w)
     
  2. jcsd
  3. Jan 18, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    Can you think of a reason why the phase angles of the each value might be important?
     
  4. Jan 18, 2016 #3

    NascentOxygen

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    Staff: Mentor

    This is so similar to your earlier thread that you could have continued in that same thread. The formula for 3 phase power remains the same.
     
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