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876 ⏐⏐⏐ POWER (ac)
P q
s
be set up. Then, using the Time Domain(Transient) option to get a
plot versus time and setting the Run to time to 1 ms and the Maximum
step size to 1 ms/1000 � 1 ms, we select OK and then the Run PSpice
icon to perform the simulation. Then Trace-Add Trace-V1(R) will
result in the curve appearing in Fig. 19.37. Next, Trace-Add Trace-
I(R) will result in the curve for the current as appearing in Fig. 19.37.
Finally the power curve will be plotted using Trace-Add Trace-
V1(R)*I(R) from the basic power equation, and the larger curve of Fig.
19.37 will result. The original plot had a y-axis that extended from �50
to �50. Since all of the data points are from �20 to �50, the y-axis
was changed to this new range through Plot-Axis Settings-Y Axis-
User Defined-(�20 to �50)-OK to obtain the plot of Fig. 19.37.
FIG. 19.37
The resulting plots for the power, voltage, and current for the resistor
of Fig. 19.36.
You can distinguish between the curves by simply looking at the
symbol next to each quantity at the bottom left of the plot. In this case,
however, to make it even clearer, a different color was selected for each
trace by clicking on each trace with a right click, selecting Properties,
and choosing the color and width of each curve. However, you can also
add text to the screen by selecting the ABC icon to obtain the Text
Label dialog box, entering the label such as P(R), and clicking OK.
The label can then be placed anywhere on the screen. By selecting the
Toggle cursor key and then clicking on I(R) at the bottom of the
screen, we can use the cursor to find the maximum value of the current.
At A1 � 250 ms or 1 ⁄ 4 of the total period of the input voltage, the current
is a peak at 3.54 A. The peak value of the power curve can then be
found by right-clicking on V1(R)*I(R), clicking on the graph, and then
finding the peak value (also available by simply clicking on the Cursor