(2)DefiningtheTotal HarmonicDistortionTHD（滋畸变率（orharmonicfactorHF谐波因数）ameasure of the distortion of a waveform.-12Ms s1distortion=100%THD= 100 ×-15sidistortion(t) consists of components at frequencies that aremultiples of 1/T,12>Tshdistortionh=2Where Ishis the rms value of the harmonic component“h
(2) Defining the Total Harmonic Distortion THD (谐 波总畸变率)(or harmonic factor HF谐波因数): a measure of the distortion of a waveform. I 2 I − I 2 %THD = 100 distortion = 100 s s1 Is1 Is1 idistortion(t) consists of components at frequencies that are multiples of 1/T1 . h=2 2 distortion sh I = I Where Ish is the rms value of the harmonic component “h”
(3)Defining theDisplacementPowerFactorDPF(orDisplacementFactor）（基波功率因数、相位移因数）DPF= coSd(4)DefiningtheDistortionFactor（畸变因数）1slI,DPFPF(DPF)V1+THD2·Nonlinearloadsreducepowerfactor.☆
• Nonlinear loads reduce power factor. ☆ DPF 1+THD2 s Is1 PF = (DPF) = I (3) Defining the Displacement Power Factor DPF (or Displacement Factor ) (基波功率因数、相位移因数) DPF = cos1 (4) Defining the Distortion Factor (畸变因数) = Is1 Is
Harmonic Currents Lower Power Factor0.90.80.7PFDPF0.00.50.4015020025050100300%THDRatio of actual powerfactorto displacement powerfactordecreases withincreasingTHD
Harmonic Currents Lower Power Factor Ratio of actual power factor to displacement power factor decreases with increasing THD
Crestfactor（峰值因数):ameasureofthe(5) Defining thepeak input current Is,peak as compared with its rms value ls.1s, peakCF:Is,peak --the peak value of is.I,2Deleteriouseffectsofpoorpowerfactor★P1PF.PF1V Increasing power loss in transmission lines,transformers,generators
(5) Defining the Crest factor (峰值因数): a measure of the peak input current Is,peak as compared with its rms value Is . Is,peak -the peak value of is . Is CF = Is, peak 2 Deleterious effects of poor power factor ☆ ✓ Increasing power loss in transmission lines, transformers, generators. P 1 I = Vs PF PF s
3Deleteriouseffectsofharmonicdistortion★VIncreasing power loss in transmission lines,transformers,generatorsV The utility voltage waveform will also become distorted,adversely affecting other linear loads.disVPCC=VsdtOCdOther equipmentFigure 5-25 Line-voltage notching and distortionFigure 5-26Voltage waveform at the point of common coupling in thecircuitof Fig.5-25
16 3 Deleterious effects of harmonic distortion ☆ ✓Increasing power loss in transmission lines, transformers, generators. ✓The utility voltage waveform will also become distorted, adversely affecting other linear loads. dt dis vPCC = vs − Ls1