* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Introduction - Electrical and Computer Engineering
Three-phase electric power wikipedia , lookup
Electronic engineering wikipedia , lookup
Power inverter wikipedia , lookup
Ground (electricity) wikipedia , lookup
Fault tolerance wikipedia , lookup
Electrical ballast wikipedia , lookup
Voltage optimisation wikipedia , lookup
History of electric power transmission wikipedia , lookup
Power engineering wikipedia , lookup
Stray voltage wikipedia , lookup
Regenerative circuit wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Electrical substation wikipedia , lookup
Distribution management system wikipedia , lookup
Buck converter wikipedia , lookup
Surge protector wikipedia , lookup
Earthing system wikipedia , lookup
Mains electricity wikipedia , lookup
Flexible electronics wikipedia , lookup
Opto-isolator wikipedia , lookup
Circuit breaker wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Current source wikipedia , lookup
Integrated circuit wikipedia , lookup
Power MOSFET wikipedia , lookup
Alternating current wikipedia , lookup
Electrical wiring in the United Kingdom wikipedia , lookup
Two-port network wikipedia , lookup
Thévenin and Norton Equivalent Circuits ELEC 308 Elements of Electrical Engineering Dr. Ron Hayne Images Courtesy of Allan Hambley and Prentice-Hall Equivalent Circuits Two-terminal circuit Circuit that has any complex interconnection of resistances and sources Has ONLY two points that can be connected to other circuits We will learn how to represent complex twoterminal circuits by simple equivalent circuits ELEC 308 2 Thévenin Equivalent Circuits Consists of voltage source in series with a resistance ELEC 308 3 Circuit Parameters The Thévenin source voltage is equal to the open-circuit voltage of the original network, or Vt = voc ELEC 308 4 Circuit Parameters The Thévenin short-circuit current is given by Vt Rt ELEC 308 5 Circuit Parameters The Thévenin resistance is given by Vt v oc Rt isc isc Thus, we can determine a Thévenin equivalent circuit simply by measuring the OPEN-CIRCUIT VOLTAGE and SHORTCIRCUIT CURRENT ELEC 308 6 Example 2.16 ELEC 308 7 Exercise Find the Thévenin equivalent circuit ELEC 308 8 Norton Equivalent Circuits Consist of independent CURRENT source in PARALLEL with a resistance ELEC 308 9 Circuit Parameters The Norton source current is equal to the short-circuit current of the original network, or In = isc ELEC 308 10 Circuit Analysis Algorithm Complete two of the following: Determine the open-circuit voltage (Vt = voc). Determine the short-circuit current (In = isc). Zero the sources and find the Thévenin resistance Rt looking back into the terminals. Use Ohm’s Law (Vt=InRt) to compute the remaining parameter. Draw one of the following: Thévenin equivalent circuit with independent VOLTAGE source Vt in SERIES with Rt Norton equivalent circuit with independent CURRENT source In in PARALLEL with Rt ELEC 308 11 Exercise 2.29 Find the Norton equivalent circuit ELEC 308 12 Maximum Power Transfer Consider the two-terminal circuit and load resistance below. What value of RL would deliver maximum to the load resistance RL? ELEC 308 13 Maximum Power Transfer The load resistance RL that absorbs the maximum power from a two-terminal circuit is equal to the Thévenin resistance, or RL=Rt The maximum power transferred to the load resistance is given by PL max Vt2 4Rt ELEC 308 14 Example 2.21 Find the load resistance for max power transfer Find the max power ELEC 308 15 Principle of Superposition Suppose we have a circuit with MULTIPLE independent sources We wish to determine a specific response (current or voltage) in the circuit We can EASILY determine the response due to a SINGLE independent source (by zeroing out the other independent sources) The SUPERPOSITION principle states that the total response is the SUM of the responses to each of the independent sources acting INDIVIDUALLY ELEC 308 16 Superposition Illustration ELEC 308 17 Strain Measurements ELEC 308 18 Wheatstone Bridge Circuit used to measure UNKNOWN resistances Used by ME’s and CE’s to measure the resistances of strain gauges in experimental stress studies of machines and buildings ELEC 308 19 Wheatstone Bridge ELEC 308 20 Summary Thevenin Equivalent Circuit Norton Equivalent Circuit Maximum Power Transfer Superposition Wheatstone Bridge ELEC 308 21