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// Example 8.2
// Determine (a) The minimum value of excitation that will maintain
// synchronism (b) Repeat (a) using eq.(8.16) (c) Repeat (a) using eq.(8.21)
// (d) Power angle if the field excitation voltage is increased to 175% of the
// stability limit determined in (c)
// Page No. 322
clc;
clear;
close;
// Given data
Pin=40; // Input power
Pin1phase=40/3; // Single phase power
Xs=1.27; // Synchronous reactnace
VT=220/sqrt(3); // Voltage
delta=-90; // Power angle
f=60; // Operating frequency
P=4; // Number of poles
Pmech=100; // Mechanical power
eta=0.96; // Efficiency
FP=0.80; // Power factor leading
V=460; // Motor voltage
Xs_Mag=2.72; // Synchronous reactnace magnitude
Xs_Ang=90; // Synchronous reactnace magnitude
deltaPull=-90; // Pullout power angle
// (a) The minimum value of excitation that will maintain synchronism
Ef=98; // From the graph (Figure 8.13)
// (b) The minimum value of excitation using eq.(8.16)
Ef816=-Pin*Xs*746/(3*VT*sind(delta));
// (c) The minimum value of excitation using eq.(8.21)
Ef821=Xs*Pin1phase*746/(VT);
// (d) Power angle if the field excitation voltage is increased to 175%
delta2=Ef816*sind(delta)/(1.75*Ef816);
delta2=asind(delta2);
// Display result on command window
printf("\n The minimum value of excitation = %0.0f V ",Ef);
printf("\n The minimum value of excitation using eq.(8.16) = %0.0f V ",Ef816);
printf("\n The minimum value of excitation using eq.(8.21) = %0.0f V ",Ef821);
printf("\n Power angle = %0.0f deg ",delta2);
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