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// Example 2.5
// Computation of (a) Equivalent impedance of the transformer referred to the
// high side (b) Input impedance of the combined transformer and load (C) Actual
// input voltage at the high side (d) Input impedance if the load is disconnected
// (e) Exciting current for the conditions in (d)
// Page No. 60
clc;
clear;
close;
// Given data
S=75000; // Transformer ratings
VLS=240; // Low side voltage magnitude
PF=0.96; // Lagging power factor
VLS_Ang=0; // Low side voltage angle
VL=240; // Load voltage
VHS=4800; // High side voltage
RHS=2.488; // High side resistance
RLS=0.00600; // Low side resistance
XHS=4.8384; // High side reactance
XLS=0.0121 // Low side reactance
Rfe=44202; // High side resistance
Xm=7798.6; // High side reactance
// (a) Equivalent impedance of the transformer referred to the
// high side
ILS=S*1/2/VLS; // Delivering one-half rated load
Theta=acosd(PF); // Angle
ThetaI=0-Theta;
ZloadLS_Mag=VLS/ILS; // Low side impedance magnitude
ZloadLS_Ang=VLS_Ang-ThetaI; // Low side impedance angle
a=VHS/VL; // Ratio of High side and low side voltages
Zeq_LS=RHS+a^2*RLS+%i*(XHS+a^2*XLS)
// Complex to Polar form...
Zeq_Mag=sqrt(real(Zeq_LS)^2+imag(Zeq_LS)^2); // Magnitude part
Zeq_Ang= atan(imag(Zeq_LS),real(Zeq_LS))*180/%pi; // Angle part
// (b) Input impedance of the combined transformer and load
ZloadHS_Mag=a^2*ZloadLS_Mag; // High side impedance magnitude
ZloadHS_Ang=ZloadLS_Ang; // High side impedance angle
// Polar to Complex form
ZloadHS_R=ZloadHS_Mag*cos(-ZloadHS_Ang*%pi/180); // Real part of complex number
ZloadHS_I=ZloadHS_Mag*sin(ZloadHS_Ang*%pi/180); // Imaginary part of complex number
Zin=ZloadHS_R+%i* ZloadHS_I+Zeq_LS; // Input impedance
// Complex to Polar form...
Zin_Mag=sqrt(real(Zin)^2+imag(Zin)^2); // Magnitude part
Zin_Ang= atan(imag(Zin),real(Zin))*180/%pi; // Angle part
// (c) Actual input voltage at the high side
IHS=ILS/a; // High side current
VT=IHS*Zin_Mag;
// (d) Input impedance if the load is disconnected
X=(1/Rfe)+(1/Xm*%i);
ZinOC=1/X; // Input impedance
ZinOC_Mag=sqrt(real(ZinOC)^2+imag(ZinOC)^2); // Magnitude part
ZinOC_Ang= atan(imag(ZinOC),real(ZinOC))*180/%pi; // Angle part
ZinOC_Ang=ZinOC_Ang*-1;
// (e) Exciting current for the conditions in (d)
I0_Mag=VT/ZinOC_Mag; // Magnitude of current
I0_Ang=0-ZinOC_Ang; // Angle of current
// Display result on command window
printf("\n Equivalent impedance of the transformer magnitude = %0.2f Ohm ",Zeq_Mag);
printf("\n Equivalent impedance of the transformer angle = %0.1f deg ",Zeq_Ang);
printf("\n Input impedance of the combined transformer and load magnitude = %0.2f Ohm ",Zin_Mag);
printf("\n Input impedance of the combined transformer and load angle = %0.2f deg ",Zin_Ang);
printf("\n Actual input voltage at the high side = %0.0f V", VT);
printf(" \n Input impedance magnitude when load is disconnected = %0.0f Ohm",ZinOC_Mag);
printf(" \n Input impedance angle when load is disconnected = %0.2f deg",ZinOC_Ang);
printf(" \n Exciting current magnitude = %0.2f A",I0_Mag);
printf(" \n Exciting current angle = %0.0f deg",I0_Ang);
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