%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  shmtrdes.m - plots developed torque-speed curve for shunt 
%               excited dc motor with rated voltage applied
%               for the example design motor of Chapter 5.
%               Uses OCC calculated & saved by dcOCsat.m. 
%               Armature reaction neglected.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear; clf;
VtR=500;                      % Rated terminal voltage
PsR=400;                      % Rated output horsepower
Ra=0.0141;                    % Armature resistance
a=0.4; b=1.2e-5;              % F&W loss equation coefficients
nmR=1750;                     % Rated speed(rpm)
% Rated developed torque & armature current
TdR=PsR*746/(nmR*pi/30)+(a+b*nmR^1.7)*30/pi; 
IaR=(VtR-sqrt(VtR^2-4*Ra*TdR*nmR*pi/30))/2/Ra;

load eifdes; eif=eifdes;  % Load stored OCC from dcOCsat.m run
m=length(eif); npts=200;
Kphip=eif(1:m,1)/(nmR*pi/30); If=eif(1:m,2);
% Rated If
IfR=interp1(Kphip, If, (VtR-IaR*Ra)/(nmR*pi/30));
Rfeq=VtR/IfR;    % Total shunt field circuit resistance
npts=25; Ia=linspace(1.5*PsR*746/VtR,0,npts);
% Determination of Td-nm
for i=1:npts
   Kphi=interp1(If, Kphip, IfR);
   Td(i)=Kphi*Ia(i);
   wm(i)=VtR/Kphi-Td(i)*Ra/Kphi^2; nm(i)=wm(i)*30/pi;
   Pfw=a*nm(i)+b*nm(i)^2.7;
   eff(i)=(1-(Pfw+Ia(i)^2*Ra+VtR*IfR)/(IfR+Ia(i))/VtR)*100;
   Ps(i)=(Td(i)*wm(i)-Pfw)/746;
   if eff(i)<0; m=i-1; break; end  % F&W over driving
end
subplot(2,1,1); plot(0,0,0.7376*Td(1:m),nm(1:m), ...
   0.7376*TdR,nmR,'o'); grid; title('Shunt dc motor');
ylabel('Speed, rpm'); xlabel('Torque, Ft-lb');
subplot(2,1,2); plot(0,0,Ia(1:m)+IfR,nm(1:m),IaR+IfR,nmR,'o'); grid;
title('Shunt dc motor');
ylabel('Speed, rpm'); xlabel('Line current, A');
figure(2)
subplot(2,1,1); plot(Ps(1:m),nm(1:m),PsR,nmR,'o'); grid;
title('Shunt dc motor');
ylabel('Speed, rpm'); xlabel('Output power, HP');
subplot(2,1,2); plot(eff(1:m),nm(1:m),94,nmR,'*'); grid;
title('Shunt dc motor');
ylabel('Speed, rpm'); xlabel('Efficiency, %');