ECE201_Lecture39 - ECE201 Linear Circuit Analysis I Lecture...

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1 ECE201 Linear Circuit Analysis I Lecture 39 Topic: Power Factor Improvement 1. Power factor (p.f.) and the power factor angle (p.f.a.) (1) pf = P real P apparent = P ave V eff I eff = cos θ z ( ) where θ Z = ∠ Z j ω ( ) = θ v − θ i (2) pfa = θ Z = θ v − θ i pfa uniquely determines pf; but not vice versa, since cos( α ) = cos(– α ) . So we use “lagging” and “leading” to distinguish between positive and negative angles. “lagging” pfa: phase of I lags behind phase of V . ⇒ θ i < θ v ⇒ θ v − θ i > 0 ⇒ θ z > 0 “leading” pfa: phase of I leads phase of V . ⇒ θ i > θ v ⇒ θ v − θ i < 0 ⇒ θ z < 0 (3) Range of pf and pfa 0 ≤ pf ≤ 1 –90 ˚ ≤ θ Z ≤ 90˚ L,C R C R L θ Z = 0 most circuits are inductive in real life, i.e., have “lagging” pfa, i.e., θ v − θ i = θ z > 0 Ideally, we want pf 1, or θ z 0 , then P ave Apparent power
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2 2. Example (continued from last lecture)
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This note was uploaded on 04/19/2011 for the course ECE 201 taught by Professor All during the Spring '08 term at Purdue University-West Lafayette.

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ECE201_Lecture39 - ECE201 Linear Circuit Analysis I Lecture...

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