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// Example 8.1
// Determine (a) Developed torque (b) Armature current (c) Excitation voltage
// (d) Power angle (e) Maximum torque
// Page No. 317
clc;
clear;
close;
// Given data
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) Developed torque
ns=120*f/P; // Synchronous speed
Td=5252*Pmech/(ns*eta);
// (b) Armature current
S=Pmech*746/(eta*FP);
Theta=-acosd(FP); // Power factor angle (negative as FP is leading)
V1phi=V/sqrt(3); // Single line voltage
S1phi_Mag=S/3; // Magnitude
S1phi_Ang=Theta; // Angle
VT_Mag=V1phi;
VT_Ang=0;
Ia_Mag=S1phi_Mag/VT_Mag; // Armature current magnitude
Ia_Ang=S1phi_Ang-VT_Ang; // Armature current angle
Ia_Ang=-Ia_Ang; // Complex conjugate of Ia
// (c) Excitation voltage
Var1_Mag=Ia_Mag*Xs_Mag;
Var1_Ang=Ia_Ang+Xs_Ang;
/////////
N01=VT_Mag+%i*VT_Ang;
N02=Var1_Mag+%i*Var1_Ang;
// Polar to Complex form
N01_R=VT_Mag*cos(-VT_Ang*%pi/180); // Real part of complex number 1
N01_I=VT_Mag*sin(VT_Ang*%pi/180); //Imaginary part of complex number 1
N02_R=Var1_Mag*cos(-Var1_Ang*%pi/180); // Real part of complex number 2
N02_I=Var1_Mag*sin(Var1_Ang*%pi/180); //Imaginary part of complex number 2
FinalNo_R=N01_R-N02_R;
FinalNo_I=N01_I-N02_I;
FinNum=FinalNo_R+%i*FinalNo_I;
// Complex to Polar form...
FN_M=sqrt(real(FinNum)^2+imag(FinNum)^2); // Magnitude part
FN_A = atan(imag(FinNum),real(FinNum))*180/%pi;// Angle part
//////
Ef_Mag=FN_M;
Ef_Ang=FN_A;
// (d) Power angle
delta=Ef_Ang;
// (e) Maximum torque
Pin=3*(-VT_Mag*Ef_Mag/Xs_Mag)*sind(deltaPull); // Active power input
Tpull=5252*Pin/(746*ns);
// Display result on command window
printf("\n Developed torque = %0.0f lb-ft ",Td);
printf("\n Armature current magnitude= %0.2f A ",Ia_Mag);
printf("\n Armature current angle= %0.2f deg ",Ia_Ang);
printf("\n Excitation voltage magnitude = %0.0f V ",Ef_Mag);
printf("\n Excitation voltage angle = %0.1f deg ",Ef_Ang);
printf("\n Power angle = %0.1f deg ",delta);
printf("\n Maximum torque = %0.0f lb-ft ",Tpull);
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