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// Example 11.1
// Computation of (a) The armature current when operating at rated conditions
// (b) The resistance and power rating of an external resistance required in
// series with the shunt field circuit to operate at 125 percent rated speed
// Page No. 448
clc;
clear;
close;
// Given data
HP=40; // hp rating of the device
Perratedload=0.902; // Percentage rated load
VT=240; // Voltage value of motor
RF=99.5; // Resistance of shunt motor
Nf=1231; // Turns per pole of the shunt motor
Ra=0.0680; // Armature resistance
RIP=0.0198; // Interpole winding resistance
Rs=0.00911; // Resistance of series field winding
Bp1=0.70; // Flux density for a net mmf
n1=1150; // Speed of shunt motor
// (a) The armature current when operating at rated conditions
P=HP*746/Perratedload;
IT=P/VT; // Total current
IF=VT/RF; // Field current
Ia=IT-IF;
// (b) The resistance and power rating of an external resistance required in
// series with the shunt field circuit to operate at 125 percent rated speed
Fnet=Nf*IF; // Corresponding mmf from magnetization curve
Racir=Ra+RIP+Rs;
n2=n1*1.25; // 125 percent rated speed
// Shaft load is adjusted to value that limits the armature current to 115%
// of rated current
Bp2=Bp1*(n1/n2)*((VT-Ia*Racir*1.15)/(VT-Ia*Racir))
FF=2.3*1000;
IF1=FF/Nf;
Rx=(VT/IF1)-RF;
PRx=(IF1^2)*Rx;
// Display result on command window
printf("\n The armature current = %0.2f A ",Ia);
printf("\n The resistance rating = %0.1f Ohm ",Rx);
printf("\n The power rating = %0.1f W ",PRx);
//Note: Answer varies due to round-off errors
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