%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% torq1ph.m - calculates torque-speed curve for
%             single-phase induction motor.
% 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear; clf;
p=4; f=60; Vm=120*sqrt(2); % p=poles, f=frequency
Rs=2.02; Xs=2.79; Xm=106.8; Rr=4.12; Xr=2.12;
smax=2; npts=100;  % smax=max slip, npts=points for curve
ws=2/p*2*pi*f;     % Synchronous speed
Zs=Rs+Xs*j; Zm=0+Xm/2*j;
s=zeros(1,npts); dels=smax/npts;
for i=2:npts-1; s(i)=(i-1)*dels; end
s(1)=0.001; s(npts)=smax-0.001;
Td=zeros(1,npts); Tdf=Td; Tdb=Td; wm=Td;
for i=1:npts  % Loop to calculate torque points
ZU=Rr/2/s(i)+Xr/2*j; ZL=Rr/2/(2-s(i))+Xr/2*j;
Zf=Zm*ZU/(Zm+ZU); Zb=Zm*ZL/(Zm+ZL);
Is=Vm/sqrt(2)/(Zs+Zf+Zb);
Irf=abs(Is*Zm/(Zm+ZU)); Irb=abs(Is*Zm/(Zm+ZL));
wm(i)=(1-s(i))*ws;
if wm(i) == 0
Tdf(i)=0.5*Irf^2*Rr/s(i)/ws; Tdb(i)=-0.5*Irb^2*Rr/(2-s(i))/ws;
else;
Tdf(i)=0.5*Irf^2*Rr*(1-s(i))/wm(i)/s(i);
Tdb(i)=0.5*Irb^2*Rr*(s(i)-1)/wm(i)/(2-s(i));
end
Td(i)=Tdf(i)+Tdb(i);
nm=wm*30/pi;
end
plot(nm,Td,nm,Tdf,'--',nm,Tdb,'-.');grid
title('Torque-speed for single-phase induction motor');
xlabel('Speed, rpm'); ylabel('Torque, N-m');