107_23 - 1 Electrical Engineering Technology EET 107...

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Unformatted text preview: 1 Electrical Engineering Technology EET 107 Introduction to Circuit Analysis # 23 Professor Robert Herrick Purdue University © EET 107 - 23 Introduction to Circuit Analysis 2 Electrical Engineering Technology Norton’s Theorem Supply Conversion Lab Techniques Parallel Voltage Supplies Purdue University © EET 107 - 23 Introduction to Circuit Analysis 3 Norton’s model Purdue University © EET 107 - 23 Introduction to Circuit Analysis 4 Norton Model Electronic Circuit IN RN Norton Model Equivalent circuit of the original Electronic Circuit Purdue University © EET 107 - 23 Introduction to Circuit Analysis 5 Norton Model Electronic Circuit IN Original circuit RN Norton Model IN = original circuit’s short circuit current RN = original circuit’s output resistance with sources 0’d Purdue University © EET 107 - 23 Introduction to Circuit Analysis 6 Norton Model Electronic Circuit IN RN Norton Model ® Valid for any load ® Same resulting load voltage and current Purdue University © EET 107 - 23 Introduction to Circuit Analysis 7 Norton Current Electronic Circuit ISC Short Circuit Current Short the output ! Purdue University © EET 107 - 23 Introduction to Circuit Analysis 8 Norton Current Electronic Circuit Short Circuit Current ISC IN = ISC IN RN Purdue University © Note: If ISC is down, current source must be up. EET 107 - 23 Introduction to Circuit Analysis 9 Norton Resistance Electronic Circuit RTH RN = RTH Purdue University © EET 107 - 23 Introduction to Circuit Analysis 10 Norton Model Analysis IL Electronic Circuit + VL - Load Same IL and V L IL Norton Model Purdue University © + VL EET 107 - 23 Load Introduction to Circuit Analysis 11 Norton Model Analysis - example 6Ω 24V + - IL 3Ω + VL - 6Ω Find IL and V L using the Norton model approach ! Purdue University © EET 107 - 23 Introduction to Circuit Analysis 12 Norton Model Current - example 6Ω 24V + - ISC Short circuit current 3Ω ISC = IN = 24V / 6Ω = 4A Calculate or measure ISC Purdue University © EET 107 - 23 Introduction to Circuit Analysis 13 Norton Model Current - example 6Ω 24V + - + 3Ω VOC - ETH = VOC = ( 3Ω / 9Ω ) 24V = 8V Calculate or measure VOC Purdue University © EET 107 - 23 Introduction to Circuit Analysis 14 Norton Resistance - example RN = RTH = ETH / ISC RTH = 8V / 4A = 2Ω Purdue University © EET 107 - 23 Introduction to Circuit Analysis 15 Norton Model - example 4A IN 2Ω Purdue University © RTH EET 107 - 23 Norton Model Introduction to Circuit Analysis 16 Norton Model - with load attached IL 4A + VL - 2Ω model IL VL load = 2 Ω / 8Ω x 4A = 1A = 1A x 6 Ω = Purdue University © 6Ω 6V EET 107 - 23 Same load results ! Introduction to Circuit Analysis 17 Overview Supply Conversions Purdue University © EET 107 - 23 Introduction to Circuit Analysis 18 Equivalent Models - supply conversion RTH ETH IN + - Thevenin model RN Norton model RTH = RN ETH = IN • RTH IN = ETH / RTH Purdue University © EET 107 - 23 Introduction to Circuit Analysis 19 Thevenin Resistance Electronic Circuit + VOC - Electronic Circuit ISC RTH = RN = VOC / ISC Warning - SHORT can cause smoke or loading ! Purdue University © EET 107 - 23 Introduction to Circuit Analysis 20 Equivalent Circuit - source conversion + 3 mA R2 3 k R1 6 kΩ 9V − convert RTH = RN = 6 kΩ ETH = 3mA • 6 kΩ = 18V Purdue University © EET 107 - 23 Introduction to Circuit Analysis 21 Example model - source conversion 1 mA +3V− 6 kΩ 18 V + 12V R2 3 k 9V − ENET = 18V – 9V = 9V RT = 6 kΩ + 3 kΩ = 9 kΩ IR2 = 9V / 9kΩ = 1 mA Purdue University © EET 107 - 23 Introduction to Circuit Analysis 22 Original Circuit - source conversion 1 mA 2 mA 3 mA R1 6 kΩ + 12V +3V− R2 3 k 9V − IR1 = 3 mA − 1mA = 2mA VR1 = VIsupply = 2mA • 6kΩ = 12V Purdue University © EET 107 - 23 Introduction to Circuit Analysis 23 Lab Measurements Purdue University © EET 107 - 23 Introduction to Circuit Analysis 24 Thevenin Voltage - measure VOC IL Electronic Circuit Electronic Circuit Purdue University © + VL - Load Open load + ETH - EET 107 - 23 voltmeter Introduction to Circuit Analysis 25 Measure Norton Current - ISC IN Electronic Circuit ammeter careful Purdue University © EET 107 - 23 Introduction to Circuit Analysis 26 Thevenin Resistance Measurements Four basic techniques u Measure ETH & IN, then RTH = ETH / IN u Live circuit, matched load u Live circuit, partial loading u Dead circuit, Ohmmeter with supplies zeroed Ohmmeter Purdue University © EET 107 - 23 Introduction to Circuit Analysis 27 Thevenin Resistance Measurements Using VOC and ISC u Measure OPEN CIRCUIT voltage u Measure SHORT CIRCUIT current RTH = VOC / ISC = ETH / IN Careful ! ISC not always possible ! Purdue University © EET 107 - 23 Introduction to Circuit Analysis 28 Thevenin Resistance - matched load Electronic Circuit + ETH - Electronic Circuit + Purdue University © ½ ETH - EET 107 - 23 Attach & adjust pot. VPOT = ½ ETH voltmeter Introduction to Circuit Analysis 29 Thevenin Resistance - matched load RTH ETH + - RPOT + ½ ETH - + ½ ETH - RPOT = RTH Purdue University © EET 107 - 23 Introduction to Circuit Analysis 30 Thevenin Resistance - unmatched load + VL - Electronic Circuit RL voltmeter Series Circuit Analysis IL RTH ETH + - + VRth − + VL − Purdue University © IL = IRth = VL / RL RL VRth = ETH – VL RTH = VRth / IL EET 107 - 23 Introduction to Circuit Analysis 31 Thevenin RTH - dead circuit measurement Electronic Circuit RTH ohmmeter ® Power off ® Zero sources E è replaced by short I è replaced by open Purdue University © EET 107 - 23 Open load Introduction to Circuit Analysis 32 Parallel Voltage Supplies Purdue University © EET 107 - 23 Introduction to Circuit Analysis 33 Parallel Voltage Supplies Isupply 24 V 24 V R1 R2 12 k Ω 24 V 6 kΩ E’s must be the same. IR1 = 24V / 12kΩ = 2mA Each supply IR2 = 24V / 6kΩ = 4mA Isupply = 6mA / 3 = 2mA Isupply = 2mA + 4mA = 6mA Purdue University © EET 107 - 23 Introduction to Circuit Analysis 34 Electrical Engineering Technology Norton’s Theorem Supply Conversion Lab Techniques Parallel Voltage Supplies Purdue University © EET 107 - 23 Introduction to Circuit Analysis ...
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This note was uploaded on 02/22/2012 for the course ECET 107 taught by Professor Staff during the Fall '08 term at Purdue.

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