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


    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?