View source for Textbook problem 6.13 Octave Script

 % This file is the solution for Problem 6.13 in the text on induction machines.
 %  See the notes from March 2 and following.  It demonstrates using inline
 % fuctions in Gnu Octave, and using fsolve.
 %
 %  Rob Frohne and EMEC Class 2011
 %
 %
 s=.035
 R1=.21
 X1=.26
 X2=.26
 Xm=10.1
 V1=230/sqrt(3)
 P=15000
 nph=3
 np=4
 %x(1) = real(I2), x(2) = imag(I2), x(3) = Rr
 a = @(x) [x(3)./s+x(3).*(1+X2./Xm)+X1.*x(3)./s./Xm];
 b = @(x) [X1.*(1+X2./Xm)-R1.*x(3)./s./Xm+X2];
 fcn = @(x) [x(1).*a(x)-x(2).*b(x)-V1, x(2).*a(x)+x(1).*b(x),x(1)-sqrt(181.5/x(3))];
 [x,fval,info]=fsolve(fcn,[37,0,.13],optimset("ComplexEqn", "Off"));
 I2=complex(x(1),x(2))
 Rr=x(3)
 
 wr=2*pi.*[-60:.01:800].*2./np;
 wa=2*pi*60*2/np;
 s=(wa-wr)./wa;
 
 Il=V1./(R1+j*X1+(j*Xm.*(Rr./s+j*X2))./(Rr./s+j*X2+j*Xm));
 I2=Il*j*Xm./(j*Xm+Rr./s+j*X2);
 T=abs(I2.*I2).*Rr.*(1-s)./s./wr;
 figure(1)
 subplot(2,1,1)
 plot(wr*60/2/pi,T)
 title('Torque')
 xlabel('rotor speed (RPM)')
 subplot(2,1,2)
 plot(s,T)
 xlabel('slip, s')