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// Example 11.5
// Computation using linear approximation to show the gross error that occurs
// when a linear assumption is applied to compound motors operating at overload
// conditions
// Page No. 456
clc;
clear;
close;
// Given data
Nf=577; // Turns per pole of the shunt motor
IF=4.88; // Field current
Ns=4.5;
IA=450.09; // Armature current
F2=4367.8; // mmf
VT=240; // Voltage value of motor
RF=49.2; // Resistance of shunt motor
HP=125;
perratedload=0.854; // Percentage rated load
Rx1=17.8; // Value of resistance in Example 11.2
Fnet1=(Nf*IF)+ (0.90 * Ns*IA);
Ia2=Fnet1*IA/F2; // Armature current
If2=(F2 - Ns*Ia2*0.90)/Nf;
Rx=(VT/If2)-RF; // External resistance required
// Error introduced by linear approximation
PE=(17.8-Rx)/17.8*100;
// Display result on command window
printf("\n External resistance required in series = %0.2f Ohm ",Rx);
printf("\n Error introduced by linear approximation = %0.1f Percent ",PE);
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