Pre-Lab #7
Steady State Power Analysis
1. Lookup the crest factors for the following waveforms on the internet or in a
textbook (no source citation is required), and complete Table 1 below.
𝐶𝑟𝑒𝑠𝑡 𝐹𝑎𝑐𝑡𝑜𝑟 =
𝑉0−𝑃𝐾
𝑉𝑅𝑀𝑆
=
𝐼0−𝑃𝐾
𝐼𝑅𝑀𝑆
𝐶𝑟𝑒𝑠𝑡 𝐹𝑎𝑐𝑡𝑜𝑟 𝑜𝑓 𝑆𝑖𝑛𝑢𝑠𝑜𝑖𝑑 = √2
Waveform
Sinusoid
Square
Triangle
Sawtooth
Crest Factor
Same as Triangle
Table 1
2. For the circuit shown in Fig. 1 perform an “AC” sweep with PSpice from 250 Hz
– 10 kHz as shown. Plot the following voltages on the same graph:
a. Voltage across the load resistor R_Load (on a linear scale) vs. frequency
(on a log scale).
b. Voltage across the inductor L_Source_External (on a linear scale) vs.
frequency (on a log scale).
c. Voltage across the capacitor C_Load (on a linear scale) vs. frequency (on
a log scale).
R_Parasitic
L_Source_External
C
B
200
100mH
V+
V-
100nF
R_Source_Internal
50
1Vrms
0Vdc
V1
C_Load
V+
A
V-
250
R_Load
V+
V-
0
Fig. 1
Date Last Modified: 2/8/2016 10:56 PM
3. For the same circuit shown in Fig. 1 on a separate graph plot the imaginary
(quadrature) power stored by the inductor and the capacitor together.
a. Plot the imaginary (quadrature) power stored by the inductor
L_Source_External (on a linear scale) vs. frequency (on a log scale).
b. On the same graph plot the imaginary (quadrature) power stored by the
capacitor C_Load (on a linear scale) vs. frequency (on a log scale).
R_Parasitic
L_Source_External
C
B
200
100mH
W
100nF
R_Source_Internal
C_Load
50
A
1Vrms
0Vdc
W
V1
250
R_Load
0
Fig. 2
4. For the same circuit shown in Fig. 1 on a separate graph plot the power dissipated
by the load resistor R_Load (on a linear scale) vs. frequency (on a log scale).
R_Parasitic
L_Source_External
C
B
200
100mH
100nF
R_Source_Internal
C_Load
50
A
1Vrms
0Vdc
V1
250
R_Load
W
0
Fig. 3
5. Explain why the power response curve (power Vs frequency) for the load resistor
R_Load is a bell curve.
Date Last Modified: 2/8/2016 10:56 PM
Plotting Differential Voltage in PSpice
In PSpice differential voltage may be plotted by attaching “Voltage Differential Markers”
across the component as shown in Fig. 1. The “Voltage Differential Markers” may be
selected by clicking the symbol shown below:
First, click on the side of the component which is the positive side and a V+ probe will
appear.
Next, click on the other side of the component which is the negative side and a V- probe
will appear.
Lastly, the probes will become the same color.
Plotting Power in PSpice
In PSpice power may be plotted by attaching a “Power Dissipation Marker” to the
component dissipating power as shown in Fig. 2 and Fig. 3. The “Power Dissipation
Marker” may be selected by clicking the symbol shown below:
Date Last Modified: 2/8/2016 10:56 PM