Page 248 - Solutions Manual to accompany Electric Machinery Fundamentals

% First, initialize the values needed in this program.
v_t = 240; % Terminal vol tage (V)
r_f = 200; % Field resistance (ohms)
r_adj = 120; % A djustable resistance (ohms)
r_a = 0.14; % A rmature resistance (ohms)
i_l = 0:1:100 ; % Line currents (A)
n_ f = 1500; % Number of turns on shunt field
n_se = 15; % Number of turns on series fiel d

% Calculate the armature current for each load.
i_a = i_l - v_t / (r_f + r_adj);

% Now calculate the internal generated voltag e for
% each armature current.
e_a = v_t - i_a * r_a;

% Calculate the effective field current for each armature
% current.
i_ f = v_t / (r_f + r_adj) - (n_se / n_f) * i_a;

% Calculate the resulting internal generated voltage at
% 1200 r/min by interpol ating the motor's magnetization
% curve.
e_a0 = interp1(if_values,ea_values,i_f);

% Calculate the resulting speed from Equation (9- 13).
n = ( e_a ./ e_a0 ) * n_0;

% Calculate the induced torque corresponding to each
% speed fr om Equations (8-55) and (8-56).
t_ind = e_a .* i_a ./ (n * 2 * pi / 60);

% Plot the torque-speed curves
figure(1);
pl ot(t_ind,n,'b-','LineWidth',2.0);
xlabel('\bf\tau_{ind} (N-m)');
ylabel('\bf\itn_{m} \rm\bf(r/min)');
title ('\bfDifferentially Compounded DC Mo tor Torque-Speed
Ch aracteristic');
axis([ 0 80 2900 3500]);
grid on;

The resulting torque-speed curve is shown below.

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