Displacement Vs Distortion
Posted 30 November 2006 - 11:08 PM
Again, all help appreciated.
Posted 01 December 2006 - 02:12 PM
If you know the displacement power factor and the total harmonic current distortion, you can calculate the total power factor from Total PF = Displacement PF/sqrt(1+THDi^2).
Posted 01 December 2006 - 04:55 PM
For an accurate determination of Irms, you should determine the fundamental current (If) and each individual harmonic current for each individual load and then add the individual fundamental and harmonic currents to get totals for each, such as total fundamental (If), total 2nd harmonic (I2), total 3rd harmonic (I3) etc. The total RMS current for the plant is then Irms = sqrt(total If^2 + total I2^2 + total I3^2 + Ö total In^2).
If the loads have similar harmonic spectrums, I believe that you can just add together the total harmonic current (Ih) values for the individual loads to get a total Ih for the plant. For each distorted load, you can determine the total fundamental and harmonic currents from If = Irms/sqrt(1 + THD^2) and Ih = If x THD. To determine the total RMS current you add all the fundamental currents together and all the harmonic currents together and calculate the total RMS current from Irms = sqrt(If^2 + Ih^2). The currents of the loads without harmonic content are added as part of the total If.
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