PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Alternating Current Analysis 271

>> imp _ Z

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Magnitude of Z (in Ohms) and phase (in degrees) is given by :

Zmag =

3.6761

Phase _ deg =

-36.0274

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Example 3.4

Evaluate by hand and by using MATLAB the voltage v(t) across the series RL circuit

shown in Figure 3.52, if the current is i(t) = 5 cos(100t) A.

ANALYTICAL Solution

I = 5 ∠0°

Z = 40 + j (^100) 0.3 = 40 + j 30
V = Z (^) I = (40 + j30) 5 ∠0° = 250 ∠(36.52°)
then
v(t) = 250 cos(100t + 36.87°)
MATLAB Solution
% Script file: vol _ RL
W=100;
Z=40+jW.3;
V=5Z;
Vmax=abs(V);
Phase=angle(V);
Phasedegree=Phase180/pi;
% Print results
disp(‘^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^’)
disp(‘The peak value (in volts) and the phase (in degrees) of v(t)
are=’);
Vmax,
Phasedegree,
disp(‘^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^’)
FIGURE 3.52
Network of Example 3.4.
R 1 = 40 Ω
L = 0.3 H
v(t)
i(t)