Browse Prior Art Database

Calculating Power Factor and Distortion of a Line-Driven Non-Linear Load

IP.com Disclosure Number: IPCOM000036819D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Willis, SC: AUTHOR

Abstract

This article discloses an alternative method to the conventional time domain system of calculating the total harmonic distortion and power factor of a line current in a system that comprises a non-linear load.

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Calculating Power Factor and Distortion of a Line-Driven Non-Linear Load

This article discloses an alternative method to the conventional time domain system of calculating the total harmonic distortion and power factor of a line current in a system that comprises a non-linear load.

Referring to the figure, a fast fourier transform (FFT) 10 operates on a real- time record of the current waveform. The FFT device (if implemented in hardware) or algorithm (if implemented in software) transforms the real-time record into real and imaginary components of a frequency domain.

The calculations used in conjunction with the apparatus shown in the figure are as follows:
Ck2 = X2REAL (K W f) + X2IMAJ (K W f)

S = S C2K Harmonics HK = ((Ck2/C12)1/2) x 100%

Power Factor PF = Real Power/Apparent Power = XIMAJ (W f)/(S)1/2

Total Harmonic Distortion THD = ((S-C12)1/2/C1) x 100%

If T is the period of the waveform and N is a multiple of 2, such that N/T = N W f > twice the highest frequency of interest, then a real-time record of the current waveform of length T with N samples may be applied to FFT 10, which transforms it into real and imaginary components of the frequency domain.

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