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ECE 240 – Electrical Engineering Fundamentals PSPICE Tutorial 4 Network Theorems The examples in this tutorial and the corresponding homework continue to deal with the DC analysis of circuits, or DC Bias analysis in PSPICE. The focus of this tutorial is to illustrate the use of PSPICE to verify Norton and Thevenin’s Theorem and the Maximum Transfer of Power Theorem. Norton and Thevenin’s Theorem In class, the Thevenin and Norton equivalents of the circuit to the left of a-b shown in figure 1 were found. These equivalent circuits are shown in figures 2 and 3. 4A a 61 i 41 24 V + - 21 31 b Figure 1. Complete Circuit 61 24 V + - Figure 2. Thevenin Equivalent 4A 61 Figure 3. Norton Equivalent By Norton and Thevenin’s Theorems we know that adding the 2 Ω resistor to either of these equivalent circuits will result in the same current flow, i. This can be verified by simulating the three circuits in PSPICE and showing that the currents obtained in all three circuits are the same. Figure 4 show the results of the PSPICE simulation. Note that the current in all three circuits is 3A. Figure 4. PSPICE Simulation of Norton and Thevenin Equivalent Circuits Maximum Transfer of Power In class the maximum transfer of power theorem was used to find the value of R in the circuit shown in figure 5 that would result in the maximum transfer of power to R. V1 41 -+ 41 41 + 100 V + - V1 41 - + - 20V Figure 5. Maximum Transfer of Power Circuit R It was determined that the value of R = 3Ω would result in the maximum transfer of power. This result can be verified in PSPICE as follows. 1. Use PSPICE to simulate the circuit with a resistance of R = 3Ω. Display the power delivered to the 3 Ω resistor. Figure 6 shows that 1.2KW are delivered to this 3Ω resistor. Figure 6. Simulation of Circuit with R = 3Ω 2. Repeat this simulation with R = 2.5 Ω. As shown in figure 7, the power to the resistor has dropped to 1.19 KW. Figure 7. Simulation of Circuit with R = 2.5Ω 3. Repeat step 2 for R = 3.5 Ω. Again the results shown in figure 8 confirm that the power has dropped. Figure 8. Simulation of Circuit with R = 3.5Ω