# Makinas electricas

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• Publicado : 3 de junio de 2010

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% M-file: prob9_7.m
% M-file to create a plot of the torque-speed curve of the
% the shunt dc motor with and without armature reaction.
% Get the magnetization curve. Note that this curve is% defined for a speed of 1200 r/min.
if_values = p91_mag(:,1);
ea_values = p91_mag(:,2);
n_0 = 1200;
% First, initialize the values needed in this program.
v_t = 240;% Terminal voltage (V)
r_f = 100; % Field resistance (ohms)
r_adj = 175; % Adjustable resistance (ohms)
r_a = 0.40; % Armature resistance (ohms)
i_l =0:1:55; % Line currents (A)
n_f = 2700; % Number of turns on field

f_ar0 = 1200; % Armature reaction @ 55 A (A-t/m)
% Calculate the armature current for eachload.
i_a = i_l - v_t / (r_f + r_adj);
% Now calculate the internal generated voltage for
% each armature current.
e_a = v_t - i_a * r_a;
% Calculate the armature reaction MMF for each armature
%current.
f_ar = (i_a / 55) * f_ar0;
% Calculate the effective field current with and without
% armature reaction. Ther term i_f_ar is the field current
% with armature reaction, and the termi_f_noar is the
% field current without armature reaction.
i_f_ar = v_t / (r_f + r_adj) - f_ar / n_f;
i_f_noar = v_t / (r_f + r_adj);
% Calculate the resulting internal generated voltage at
% 1200r/min by interpolating the motor's magnetization
% curve.
e_a0_ar = interp1(if_values,ea_values,i_f_ar);
e_a0_noar = interp1(if_values,ea_values,i_f_noar);
% Calculate the resulting speed fromEquation (9-13).
n_ar = ( e_a ./ e_a0_ar ) * n_0;
n_noar = ( e_a ./ e_a0_noar ) * n_0;
% Calculate the induced torque corresponding to each
% speed from Equations (8-55) and (8-56).
t_ind_ar =e_a .* i_a ./ (n_ar * 2 * pi / 60);
t_ind_noar = e_a .* i_a ./ (n_noar * 2 * pi / 60);
% Plot the torque-speed curves
figure(1);
plot(t_ind_noar,n_noar,'b-','LineWidth',2.0);
hold on;...