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diff --git a/887/CH17/EX17.4/17_4.sce b/887/CH17/EX17.4/17_4.sce
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+//ex17.4
+P_dev_1=50*746;      //developed power
+V_L=480;      //line voltage
+PF=0.9;      //power factor
+f=60;      //frequency
+P=8;      //number of poles
+X_s=1.4;      //synchronous reactance
+//CASE a
+n_s=120*f/P;      //speed of machine in rpm
+W_s=n_s*2*%pi/60;      //speed in radians per second
+T_dev=P_dev_1/W_s;      //developed torque
+printf(" All the values in the textbook are approximated hence the values in this code differ from those of Textbook")
+disp('CASE a:')
+disp(n_s,'speed in rpm')
+disp(T_dev,'developed torque in Nm')
+//CASE b
+V_a=V_L;      //phase voltage
+I_a_max=P_dev_1/(3*V_a*PF);      //phase current
+phi=acos(PF);
+I_a=I_a_max*complex(cos(phi),sin(phi));
+E_r=V_a-%i*X_s*I_a;      //voltage induced by rotor
+E_r_max=sqrt((real(E_r)^2)+(imag(E_r)^2));
+E_r_phi=atan(imag(E_r)/real(E_r));
+TA=-E_r_phi;      //torque angle
+disp('CASE b:')
+disp('Phase current:')
+disp(I_a_max,'peak value in amperes')
+disp(phi*180/%pi,'phase angle in degrees')
+disp('Voltage induced by rotor:')
+disp(E_r_max,'peak value in volts')
+disp(E_r_phi*180/%pi,'phase angle in degrees')
+disp(TA*180/%pi,'torque angle in degrees')
+//CASE c
+//excitation constant means the values of I_f, B_r and E_r are constant
+P_dev_2=100*746;
+sin_t=P_dev_2*sin(TA)/P_dev_1;      //developed power is proportional to sin_t
+t=asin(sin_t);
+E_r=E_r_max*complex(cos(-t),sin(-t));      //E_r is constant in magnitude
+I_a=(V_a-E_r)/(%i*X_s);      //new phase current
+I_a_max=sqrt((real(I_a)^2)+(imag(I_a)^2));
+I_a_phi=atan(imag(I_a)/real(I_a));
+PF=cos(I_a_phi);
+disp('CASE c:')
+disp('Phase current:')
+disp(I_a_max,'peak value in amperes')
+disp(I_a_phi*180/%pi,'phase angle in degrees')
+disp('Voltage induced by rotor:')
+disp(E_r_max,'peak value in volts')
+disp(-t*180/%pi,'phase angle in degrees')
+disp(t*180/%pi,'torque angle in degrees')
+disp(PF,'power factor is')