Harmonic data in power calculation

Discussion in 'General Electronics Chat' started by Sparky, Oct 26, 2010.

  1. Sparky

    Thread Starter AAC Fanatic!

    Aug 1, 2005
    75
    0

    Greetings,

    I’m looking at the output of an electronic 3-phase meter.

    I have 2 “snapshots” from the meter.

    In one snapshot I can make sense of most of the data presented.

    The output gives me Va, Vb, Vc, Ia, Ib, Ic, and their angles, a single power factor, watts, VA, and VAR.

    When I built my power triangle I almost agree with the outputted VA, watts, and VAR. I am within a little on some and right on it on other numbers.

    For this snapshot – there was “load” - current in all 3 phases is around 1.1A.

    The meter also provides “Harmonics VA and Harmonic pf” I did not use these 2 numbers in my power triangle.

    My next snapshot was without load.

    I am given the exact same data – current is around 0.1 in all 3 phases.

    I cannot get any where close to the power triangle – meaning using the same procedure above – (Vrms)(Irms) – VA, VA(cos()) = watts and so on. I do not get the outputted watts, VA and VAR. The outputted powers are quite a bit higher.

    One thing that stands out is that in this snapshot (no load) my harmonics VA and harmonics pf are quite a bit larger than the loaded snapshot.

    With load: harmonics VA = 25.7 and harmonics pf = 0.069.

    With no load: harmonics VA = 493.965 and harmonics pf = 0.30.

    Here is all of the data for the no load:

    Va = 113.336, Ia = 0.087: Ia lags Va by 15.86 degrees
    Vb = 112.676, Ib = 0.136: Ib leads Vb by 21 degrees
    Vc = 113.512, Ic = 0.158, Ic lags Vc by 10 degrees

    Watts = 710.078
    VArms = 1644.563
    VAtd = 1568.625
    VAR = 1398.719
    Pf = 0.432

    Harmonics VA = 493.965
    Harmonics pf = 0.3

    Can you show me how to get the watts, VA rms, and VAr from the provided currents and voltages?

    How do I use the provided harmonic data in power calculations?

    Thanks
    Sparky
     
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