Introduction to Electrical Systems Course Code: EE 111 Course Code: - PowerPoint PPT Presentation

Introduction to Electrical Systems Course Code: EE 111 Course Code: EE 111 Department: Electrical Engineering Department: Electrical Engineering Instructor Name: B G Fernandes Instructor Name: B.G. Fernandes E ‐ mail id: bgf @ee iitb ac in E ‐ mail id: bgf @ee.iitb.ac.in EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 1/7 03, 2009

Sub ‐ Topics: • Time domain response of RL and RC circuit • Step response of RC circuit EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 2/7 03, 2009

Review • Source conversion: I=V/R • Super ‐ position theorem: = + + I I I I I I 1 2 t If x 1 y 1 ⇒ ⇒ & x 2 y 2 y 2 For a linear system, if (x 1 +x 2 ) (y 1 +y 2 ) y , ( 1 2 ) (y 1 y 2 ) 2 EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 3/7 03, 2009

e.g.: = Ω 4 5 . R T H 6 6 = × 3 + 6 ( ) V 6 TH = 9 9 V V = = 2 2 I I I I A A SC SC N N EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 4/7 03, 2009

Determine i D (Assume diode is ideal) (Assume diode is ideal) Circuit is non ‐ linear ‘V’ across 1 Ω = (2+i D ) = V AB i + + 5 2 (2 i ) = = + ∴ ‘i’ supplied by battery D D i D 4 4 Applying KVL A l i KVL + 5 2 i = + + D 10 *4 (2 i ) D 4 = i 1 A D EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 5/7 03, 2009

Time domain response of RC and RL circuit • No transients in purely resistive circuit N i i l i i i i • I cannot change instantaneously in an inductor • V across a capacitor cannot change instantaneously • V across a capacitor cannot change instantaneously Step response: DC voltage or current Step response: DC voltage or current suddenly applied to the circuit t − RC circuit : = + − V e τ V V ( V ) c f ci f where, τ = Time constant where τ Time constant Circuit is assumed to attain steady state at t = 5 τ V ci = capacitor voltage at t = 0, V f is the final value V ci capacitor voltage at t 0, V f is the final value EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 6/7 03, 2009

Step response of R ‐ C circuit Case i) = = 0 at 0 v t c c + = = v 0 at t 0 c V V V = = V V & i R R At steady state v c = V, I = 0 ∴ V R = 0 Steady state is attained at t ≈ 5 τ At t = T + − v v = − = − = c R v v & i R c R R At steady state, v c and i = 0. Observation : ‘i’ through ‘C’ can change instantaneously h i t t l EE 111: Introduction to Electrical Systems Mon, Aug Lecture 5 B.G.Fernandes 7/7 03, 2009