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// Example 3.4
// Determine (a) Circulating current in the paralleled secondaries
// (b) Circulating current as a percent of the rated current of transformer A
// (c) Percent difference in secondary voltage that caused the circulating current
// Page No. 104
clc;
clear;
close;
// Given data
S=100000; // Transformer A and B rating
VLSA=460; // Voltage at the low side of transformer A
VLSB=450; // Voltage at the low side of transformer A
RPUA=0.0136; // Percent resistance of transformer A
XPUA=0.0350; // Percent reactance of transformer A
RPUB=0.0140; // Percent resistance of transformer B
XPUB=0.0332; // Percent reactance of transformer B
// (a) Circulating current in the paralleled secondaries
IA= S/VLSA; // Rated low side current for transformer A
IB= S/VLSB; // Rated low side current for transformer B
ReqA=RPUA*VLSA/IA; // Equivalent resistance of transfomer A
ReqB=RPUB*VLSB/IB; // Equivalent resistance of transfomer B
XeqA=XPUA*VLSA/IA; // Equivalent reactance of transfomer A
XeqB=XPUB*VLSB/IB; // Equivalent reactance of transfomer B
// Impedance of the closed loop formed by two secondaries is
Zloop=ReqA+%i*XeqA+ReqB+%i*XeqB;
// Complex to Polar form...
Zloop_Mag=sqrt(real(Zloop)^2+imag(Zloop)^2); // Magnitude part
Zloop_Ang=atan(imag(Zloop),real(Zloop))*180/%pi; // Angle part
Icirc_Mag=(VLSA-VLSB)/Zloop_Mag; // Circulating current magnitude
Icirc_Ang=0- Zloop_Ang; // Circulating current angle
// (b) Circulating current as a percent of the rated current of transformer A
IcircA=Icirc_Mag*100/IA;
// (c) Percent difference in secondary voltage that caused the circulating current
PD=(VLSA-VLSB)*100/VLSB;
// Display result on command window
printf("\n Circulating current magnitude = %0.1f A ",Icirc_Mag);
printf("\n Circulating current angle = %0.1f deg ",Icirc_Ang);
printf("\n Circulating current as a percent of the rated current = %0.1f Percent ",IcircA);
printf("\n Percent difference in secondary voltage = %0.1f Percent ",PD);
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