Page 122 - Solutions Manual to accompany Electric Machinery Fundamentals

When this program is executed, the plot of reactive power versus flux is

(d) The program in part (c) of this program calculated I A as a function of flux. A MATLAB program
that plots the magnitude of this current as a function of flux is shown below:

% M-file: prob4_26d.m
% M-file to calculate and plot the armature current
% supplied to an infinite bus as flux is varied from
% 80% to 100% of the flux at rated conditions.

% Define values for this generator
flux_ratio = 0.80:0.01:1.00; % Flux ratio
Ear = 2776; % Ea at full flux
dr = 27.3 * pi/180; % Torque ang at full flux
Vp = 1850; % Phase voltage
Xs = 15.7; % Xs (ohms)

% Calculate Ea for each flux
Ea = flux_ratio * Ear;

% Calculate delta for each flux
d = asin( Ear ./ Ea .* sin(dr));

% Calculate Ia for each flux
Ea = Ea .* ( cos(d) + j.*sin(d) );
Ia = ( Ea - Vp ) ./ (j*Xs);

% Plot the armature current versus flux
figure(1);
plot(flux_ratio*100,abs(Ia),'b-','LineWidth',2.0);
title ('\bfArmature current versus flux');
xlabel ('\bfFlux (% of full-load flux)');
ylabel ('\bf\itI_{A}\rm\bf (A)');
grid on;
hold off;
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