%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  cumgen.m - plots terminal characteristic for cumulative
%             compound dc generator. Armature reaction neglected.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
clear; clf;
VtR=600;      % Rated terminal voltage
PR=60e03;     % Rated output power
Ra=0.25;      % Armature resistance
Rs=0.03;      % Series field resistance
Nf=650;       % Shunt field turns/pole
Ns=1;         % Series field turns/pole
ILR=PR/VtR;   % Rated output current
load eif      % Load stored OCC
m=length(eif); npts=200;
E=eif(1:m,1); If=eif(1:m,2);

% Iterative determination of rated If
IfR=0;
for i=1:50;
IfR=interp1( E, If, VtR+(ILR+IfR)*(Ra+Rs))-Ns/Nf*(ILR-IfR);
end

Rfeq=VtR/IfR;    % Total shunt field circuit resistance
IL=linspace(0,1.5*ILR,npts);
  
% Iterative determination of Vt-IL
for i=1:npts
   If1=IfR;
   for j=1:100
      Vt1=interp1(If, E, If1+Ns/Nf*(IL(i)-If1))- ...
         (IL(i)+If1)*(Ra+Rs); 
      If2=Vt1/Rfeq;
      if abs(If2-If1)<= 0.001; Vt(i)=Vt1; break; end;
      If1=If2;
   end
end
plot(0,0,IL,Vt,ILR,VtR,'o'); grid;
title('Cumulative compound dc generator');
xlabel('Load current, A'); ylabel('Terminal voltage, V');