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// Example 11.3
// Computation of Speed if the load is reduced to a value that causes the
// armature current to be 30 percent of the rated current
// Page No.453
clc;
clear;
close;
// Given data
HP=100;
perratedload=0.896; // Percentage rated load
VT=240; // Voltage value of motor
Ns=14; // Number of turns/pole in series field
Ra=0.0202; // Armature resistance
RIP=0.00588; // Interpole winding resistance
Rs=0.00272; // Resistance of series field winding
n1=650; // Speed of shunt motor
Bp2=0.34; // Air gap flux density from magnetization curve
Bp1=0.87; // Air gap flux density from magnetization curve
// Computation of Speed if the load is reduced to a value that causes the
// armature current to be 30 percent of the rated current
Pin=HP*746/perratedload; // Input power
IT=Pin/VT; // Total current
Ia=IT; // Armature current
Racir=Ra+RIP+Rs; // Resistance of armature circuit
Fnet1=Ns*Ia*(1-0.080); // Net mmf
Fnet2=0.30*Fnet1; // Net mmf from magnetization curve
n2=n1/((VT-(Ia*Racir))/Bp1 * Bp2/(VT-(0.30*Ia*Racir)));
// Display result on command window
printf("\n Speed of the motor = %0.0f r/min ",n2);
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