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AC Circuit Analysis Techniques Dr. Holbert April 7, 2008 Lect18 EEE 202 1 Introduction • Today, we continue to perform AC analyses using phasors and impedances • We utilize all our circuit analysis tools to accomplish this – KCL, KVL, Ohm’s Law – Voltage and current division – Superposition, source transformation – Nodal and loop/mesh analyses – Thevenin’s and Norton’s theorems Lect18 EEE 202 2 Series Impedance Z1 Z2 Zeq Z3 Z series Z1 Z 2 Z N Z j Lect18 EEE 202 3 Parallel Impedance Z1 Z2 Z3 Zeq 1 1 1 1 1 Z par Z1 Z 2 ZM Zi Lect18 EEE 202 4 Leading and Lagging Phase x1 (t ) X M1 cost q x2 (t ) X M 2 cost x1(t) leads x2(t) by q- x2(t) lags x1(t) by q- On the following plot, which signals lead and which signals lag? Lect18 EEE 202 5 Phase Green leads blue and red Red lags blue and green 8 6 4 2 0 -2 0 0.01 0.02 0.03 0.04 0.05 -4 -6 -8 Lect18 EEE 202 6 Circuit Element Phasor Relations (ELI and ICE man) Element V/I Relation Phasor Relation Capacitor I = C dV/dt I = j ω C V = ω C V 90° Inductor V = L dI/dt V = j ω L I = ω L I 90° Resistor V = I R V=RI = R I 0° Lect18 EEE 202 Phase I leads V by 90° V leads I by 90° V and I are in-phase 7 Class Examples • Drill Problems P8-6, P8-9, P8-8 Lect18 EEE 202 8