enee204Lectures_12_13_Gomez

enee204Lectures_12_13_Gomez - Chapter 4: Equivalent...

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1 10/12/2005 1 Welcome to ENEE 204 Welcome to ENEE 204 Basic Circuit Theory Lectures 12 and 13 Chapter 5: Understanding and modeling of REAL devices: Thevenin and Norton Theorem Real voltage and current sources Real Devices 10/12/2005 2 Chapter 4: Equivalent Transformations What you should have learned: 1. Parallel and Series Connections and connectivity (redrawing if needed) 2. Voltage and current divider rules, know by heart. 3. Calculating impedance of a network. 4. Using symmetry to simplify circuit. a. No current flowing in a branch, remove the branch. b. If two points are equivalent, i.e., same voltage, just short them. 5. If two or more sources, use superposition method. Replace current source with open circuit , voltage source with a short circuit. 10/12/2005 3 Input impedance completely describes the electrical property of a passive* linear circuit between two terminals. *Passive circuit: no power sources 1 2 Z in L 1 L 2 R C Z in 1 2 R L L L R L C R L L C R L L C R L in Z Z Z Z Z Z Z Z Z Z Z Z Z + + + + + + + = = 1 2 1 1 2 1 2 1 2 // // 10/12/2005 4 Chapter 5: Thevenin and Norton Theorems - This describes the operation of REAL (non-ideal) sources, in conjunction with a “LOAD”. - Also simplifies circuit analysis. Ideal voltage source: voltage is constant regardless of current drawn or load. Non-deal voltage source: voltage is affected by load. Ideal current source: current is constant regardless of voltage needed. Non-ideal: current is affected by load.
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2 10/12/2005 5 Non-ideal voltage source can be modeled by ideal voltage source and a resistor in series. Model: + i (t) v s R s = internal resistance + v v v = v s - i R s ideal non-ideal v s Drycell + - ideal 10/12/2005 6 Non-ideal ac voltage is modeled as ideal voltage source, V s and an impedance, Z s . Z s I V V- ˆ ˆ s = + - s V ˆ Z s V ˆ + I ˆ ˆ 10/12/2005 7 Non-ideal current source can be modeled by ideal current source and an admittance in parallel. Y S V I I ˆ - ˆ ˆ s = ideal v Slope = Y s Good current source: low Y S = High Z S I s I ˆ non-ideal I s ˆ Y S V ˆ + - 1 Z S Y S = 10/12/2005 8 Non-ideal voltage and current sources can be modeled by the same circuits. I s Y N =1/Z Th + - V s Z Th I ˆ Thevenin Theorem Norton Theorem
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3 10/12/2005 9 What do we need to do learn?
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enee204Lectures_12_13_Gomez - Chapter 4: Equivalent...

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