PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

290 Practical MATLAB® Applications for Engineers

XC = -j./(w*C);

XL = j*w*L;

ZLC = XC.*XL./(XC+XL);

ZRLC = R.*ZLC./(R+ZLC); % parallel case

subplot (2,2,3);

plot (w,abs(ZRLC));

title(‘Mag. [Z(w)] vs w (parallel case)’);

xlabel (‘w in rad/sec’);

ylabel (‘Mag[Z(w)] in Ohms’);

grid on;

subplot(2,2,4);

plot(w,angle(ZRLC)*180/pi); grid on;

title(‘Phase[Z(w)] vs w (parallel case)’);

xlabel(‘w in rad/sec’);

ylabel(‘Phase angle in degrees’);

The script fi le impedance_plots is executed, and the results are indicated in Figure 3.70.

0 5000 10,000

0

200

400

600

800

Mag. [Z(w)] versus w (series case)

Mag[Z(w)] in Ohms

0 5000 10,000

− 100

− 50

0

50

100

Phase[Z(w)] versus w (series case)

Phase angle in degrees

0 5000 10,000

0

2

4

6

8

10

Mag. [Z(w)] versus w (parallel case)

Mag[Z(w)] in Ohms

0 5000 10,000

− 50

0

50

100

Phase[Z(w)] versus w (parallel case)

w in rad/sec w in rad/sec

Phase angle in degrees

FIGURE 3.70
Plots of Example 3.13.

Example 3.14

Analyze the circuit diagram shown in Figure 3.71, and obtain by hand the system loop

equations, as well as the matrix loop equation.

Create the script fi le loops that returns

1. The system matrices Z and V


2. The loop currents I 1 , I 2 , and I 3 , in phasor form


3. The instantaneous loop currents i 1 (t), i 2 (t), and i 3 (t)