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// Example 2.8
// Computation of (a) Percent impedance (b) Rated high side current
// (c) Equivalent resistance and reactance referred to the high side
// (d) High side fault current if an accidental short circuit of 0.016 Ohm
// occurs at secondary when 230V impressed across the primary
// Page No. 66
clc;
clear;
close;
// Given data
R=0.9; // Percent resistance
X=1.3; // Percent reactance
VHS=2400; // High side voltage
PV=75000; // Transformer power rating
RPU=0.009 // Per unit resistance
XPU=0.013 // Per unit reactance
VLS=240; // Low side voltage
Zshort=0.016; // Short circuit resistance
VHS_Ang=0; // High side voltage angle
VHS_Sec=2300; // Secondary high side voltage
// (a) Percent impedance
Z=sqrt(R^2+X^2);
// (b) Rated high side current
IHS=PV/VHS;
//(c) Equivalent resistance referred to the high side
Req_HS=RPU*VHS/IHS;
// Equivalent reactance referred to the high side
Xeq_HS=XPU*VHS/IHS;
//(d) High side fault current
a=VHS/VLS; // Ratio of High side and low side voltages
Zin=Req_HS+%i*Xeq_HS+a^2*Zshort; // Input impedance
Zin_Mag=sqrt(real(Zin)^2+imag(Zin)^2); // Magnitude part of input impedance
Zin_Ang= atan(imag(Zin),real(Zin))*180/%pi; // Angle part
IHS_Mag=VHS_Sec/Zin_Mag; // High side current magnitude
IHS_Ang=VHS_Ang-Zin_Ang;
//Display result on command window
printf("\n Percent impedance = %0.2f Percent ",Z);
printf("\n Rated high side current = %0.2f A", IHS);
printf(" \n High side equivalent resistance = %0.3f Ohm",Req_HS);
printf(" \n High side equivalent reactance = %0.3f Ohm",Xeq_HS);
printf(" \n High side fault current magnitude = %0.0f Ohm",IHS_Mag);
printf(" \n High side fault current angle = %0.2f deg",IHS_Ang);
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