Problem 5.8 - CHALLENGE PROBLEM! Maximum Power Transfer by Norton Source
*
* The circuit for this problem is from textbook Chap. 4, Problem 84.
* Determine the Thevenin equivalent of load "by inspection," where the
* "source" consists of the current source and resistance R1. Change
* resistance R12 to a variable resistance through the use of a model
* with a variable parameter. Use the .DC sweep function to vary the
* resistance over the range from .1 ohm to 1.9 ohms. Use Probe to
* draw the power curve for power input to the load circuit at node 1.
*
* ===> This is a good problem to use the CURSOR selection on the PROBE
* menu screen. When you press the letter C to select the cursor
* function, a pair of "cross-hair" cursors become available. The
* cursors are moved along a waveform by using the arrow keys. The
* cursors move one pixel at a time at first, but if you hold the
* arrow key down for a few seconds they will begin to move 10 pixels
* at a time. You can move backward or forward along a curve, and note
* the coordinates of the cursor in a window in the corner of the
* screen. The second cursor is selected by holding down the Shift
* key while using the arrow keys. You can also jump a cursor from
* one waveform to another by pressing the Ctrl key and an arrow key.
* The waveforms that the cursors are on are marked with a dotted
* line box around the variable or expression below the graph.
*
* NOTE: You can determine that it is not possible to adjust the
* source resistance to any finite value and observe a maximum
* in the graph of power delivered to the load. You can explore
* this result with a PSpice experiment in which the source
* resistance R1 is swept over a range of values and a PROBE graph
* of the power delivered to the load is obtained. (A suggested
* range of resistance is 0.5 ==> 10 ohms.)
* ===> The latter is left as the exercise for the student in this problem.
*
.OPT NOPAGE
I1 0 1 DC 180
V1 2 3 DC 5
V2 3 4 DC 40
V3 0 4 DC 10
R1 1 0 1
R12 1 2 RTHEV 1
R2 2 0 6
R23 2 3 5
R3 3 0 7
R34 3 4 3
R4 4 0 8
R44 4 4 4
.MODEL RTHEV RES(R=1)
.DC RES RTHEV(R) .1 1.9 .1
.PROBE ; Graph the load power V(1)*I(R12). Also
; graph the currents I(R1) and I(R12) on
; one graph. What value (approximately) of
; R12 maximizes the load power? How does
; this compare with your calculated value?
.PRINT DC V(1) I(R1) I(R12)
.END
Prob 5.8, Part 2. CHALLENGE PROBLEM! Maximum Power Transfer by Norton Source
*
* Explore the effect of a variable source resistance R1.
*
.OPT NOPAGE
I1 ; Complete the program statements.
V1 ; You may eliminate this part of the
V2 ; problem if you wish. Part 1 will run
V3 ; but an error message will be produced
R1 1 0 RSRC 1 ; for Part 2 if you do not complete this
R12 ; part before you run Part 1.
R2
R23
R3
R34
R4
R44
.MODEL RSRC RES(R=1)
.DC RES RSRC(R)
.PROBE ; Graph the load power V(1)*I(R12). Also
; graph the source power V(1)*I(I1) on
; the same graph. Is there a value of R1
; that maximizes the load power?
; Answer: It is not a finite value of R1.
; An open circuit (infinite R1) is maximum
.PRINT DC V(1) I(R1) I(R12) ; power.
.END