PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Alternating Current Analysis 287

F = 1000;

W = 2*pi*F;

ZC = -j/(W*C);

ZT = R+ZC;

I = VS/ZT;

VR = R*I;

VC = ZC*I;

subplot(2,1,1)

% Phasors diagram.

VSS = [0 VS];

VVC = [0 VC];

VVR = [0 VR];

plot(real(VSS),imag(VSS),’*’,real(VVC),imag(VVC),’+’,real(VVR),imag(VVR),’o’);

xlabel(‘Real’), ylabel(‘Imaginary’),

title(‘Phasor Diagram (Example 3.12)’); % Figure 3.68 (top)

grid on

hold ; %hold plot

plot(r e a l(V S S), i m a g(V S S), r e a l(V V C),i m a g(V V C),r e a l(V V R),i m a g(V V R));

legend(‘VS’, ‘VC’, ‘VR’);

% Check the Phasor Diagram by applying Kirchhoffs Voltage Law.

disp(‘**********************************************************’)

disp(‘****Check the Phasor Diagram results by applying *****’)

disp(‘*********** Kirchhoffs Voltage Law *******************’)

Check _ Voltage = VR+VC

disp(‘**********************************************************’)

disp(‘ (Note:Check _ V should be equal to VS=1.)’)

T = 1/F;

t = [0:2*T/50:2*T]; % t for 2 periods

VS = sin(W.*t);

VRT = abs(VR)*sin(W.*t+angle(VR));

VCT = abs(VC)*sin(W.*t+angle(VC));

subplot (2,1,2)

p l o t (t,V S,’o’,t,V R T,’*’,t,V C T,’+’)

xlabel (‘time in seconds’),

ylabel (‘Amplitude in Volts’)

title(‘Voltages of the RC Circuit of Example 3.12’);

% Figure 3.68 (bottom)

grid on

lege nd(‘vs(t)’,’v r(t)’,’vc(t)’)

The MATLAB script fi le phasor_time_plots is executed, and the results are shown as

follows:

>> phasor _ time _ plots

Current plot held

*********************************************************

****Check the Phasor Diagram results by applying*****

************** Kirchhoffs Voltage Law ******************

Check _ Voltage =

1

*****************************************************

(note that the correct result is verified by Check _ Voltage=1)