Just a quick question about Real 3 phase power

Discussion in 'Homework Help' started by Amanda_Riley, Apr 1, 2011.

  1. Amanda_Riley

    Thread Starter New Member

    May 12, 2010
    22
    0
    The equations to find real power is:

    P = 3 x Vphase x Iphase x cos(v - i)

    or √3 x Vline x Iline x cos(v - i)

    My question is if you have a delta connected 3 phase system and have

    Vphase = Vline = 120 angle 0
    Iphase = 41.6 angle -36.87
    Iline = 72.05 angle -66.87

    Would you use the angle of 36.87 for both the real power equations?
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    How did you arrive at ...

    Vphase = Vline = 120 angle 0 ?

    The phase(line)-to-neutral and phase(line)-to-phase(line) voltages can't be the same.
     
  3. Amanda_Riley

    Thread Starter New Member

    May 12, 2010
    22
    0
    its delta connected - delta source and a delta load so no line to neutral line

    Phase voltage (Vab) = Line voltage(VAB)
    Line current = √3 x phase current
     
  4. subtech

    Senior Member

    Nov 21, 2006
    123
    4
    In short, the answer is yes.

    The phase measurement (some call this the winding current) is the current magnitude and angle to use in your calculation.
     
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