{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

ECE201_Lecture39

# ECE201_Lecture39 - ECE201 Linear Circuit Analysis I Lecture...

This preview shows pages 1–6. Sign up to view the full content.

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

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
2 2. Example (continued from last lecture) The voltage across the motor below is V eff = 0 ) ( 230 rms V. The motor consumes 50 kW at a pf of 0.8 lagging. From last lecture, we found that S m = (50 + j 37.5) kVA, I eff = 87 . 36 74

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 6

ECE201_Lecture39 - ECE201 Linear Circuit Analysis I Lecture...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online