# 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
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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