Direct Current and Transient Analysis
169
Example 2.21
Assuming that the load is R L , determine the Thevenin’s equivalent circuit of the electrical network shown in Figure 2.66 by
a. Hand calculations.
b. Creating the script fi le Thevenin that simulates Thevenin’s theorem consisting in
varying R L over the range 1 ≤ R L ≤ 50 Ω, in steps of 1 Ω, and computing the respective powers for each value of R L . Recall that the resistance dissipates maximum
power when R L = R TH and its V TH = 2 V RTH .
FIGURE 2.66
Network of Example 2.21.
V s = 100 V
−
+
I
R L
R L = 1 :1: 50
a
a ′
R 1 = 20 Ω
R 2 = 60 Ω
FIGURE 2.67
Calculated Thevenin’s equivalent circuit of Example 2.21.
−
+
I
V TH = 75 V
R L
a
a′
R TH = 15 Ω
ANALYTICAL Solution
Part a
The V TH and R TH are evaluated by hand.
V TH
V
ϭ
ϩ
ϭ
ϭ
60 100
20 60
6000
80
75
*
and
R
R R
TH ϭ
ϭ
ϩ
ϭ
ϭ
1
2
20 60
20 60
1200
80
15
| |
*
The calculated Thevenin’s equivalent circuit, as seen through the terminals aa’, is shown
in Figure 2.67.
CRC_47760_CH002.indd 169
CRC_47760_CH002.indd 169
7/23/2008 1:38:53 PM
7/23/2008 1:38:53 PM