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%
%  imeqckt.m - determines parameters for the equivalent circuit of a
%              three-phase induction motor from test data.
%
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clear;
p=4; f=60; design='B'; % No. poles, frequency, NEMA design
Vdc=10.8; Idc=25.0;    % dc voltage,current data (terminal-terminal)
% Blocked rotor data (phase voltage and power, line current, br freq.)
Vbr=22.26/sqrt(3); Ibr=27.0; Pbr=770/3; fbr=15;
% No-load data (phase voltage and power, line current, speed-rpm)
Vnl=230/sqrt(3); Inl=12.9; Pnl=791/3; nnl=1798;
Req=Pbr/Ibr^2; Zbr=Vbr/Ibr; Xeq=f/fbr*sqrt(Zbr^2-Req^2);
R1=1.05*Vdc/Idc/2; R2pr=Req-R1; % 5% adjustment for ac value of R1
if design=='B'; X1=0.4*Xeq; X2pr=0.6*Xeq;
elseif design=='C'; X1=0.3*Xeq; X2pr=0.7*Xeq;
else; X1=0.5*Xeq; X2pr=0.5*Xeq;
end
thetanl=acos(Pnl/Vnl/Inl); ns=120*60/p; s=(ns-nnl)/ns;
E1=Vnl-Inl*exp(-j*thetanl)*(R1+j*X1); I2pr=E1/(R2pr/s+j*X2pr);
E1=abs(E1); I2pr=abs(I2pr);
Pc=Pnl-Inl^2*R1-I2pr^2*R2pr/s; Rc=E1^2/Pc;
if Pc<0; disp('CHECK FOR DATA ERROR - ESPECIALLY NO-LOAD SPEED'); end
Qm=Vnl*Inl*sin(thetanl)-Inl^2*X1-I2pr^2*X2pr; Xm=E1^2/Qm;
Parameters=[ '       R1           ' 'R2pr        ' 'X1           '... 
             'X2pr        ' 'Rc           ' 'Xm           ' ]
format short e
[ R1 R2pr X1 X2pr Rc Xm ]