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// Example 11.7
// Computation of the resistance of a dynamic braking resistor that will be
// capable of developing 500 lb-ft of braking torque at a speed of 1000 r/min.
// Page No. 464
clc;
clear;
close;
// Given data
T1=910; // Torque load
Pshaft=199.257*746; // Power of shaft
eeta=0.940; // Efficiency
VT=240; // Rated voltage
T2=500; // Braking torque
n1=1000; // Windage and friction speed
n2=1150; // Speed of motor
Rf=52.6; // Field resistance
Racir=0.00707; // Combined armature,compensating winding and // interpolar resistance
// Resistance of a dynamic braking resistor
Pshaft=T1*n2/5252; // Shaft power
Pin=Pshaft*746/eeta; // Input power
IT=Pin/VT; // Total current
If=VT/Rf; // Field current
Ia1=IT-If; // Armature current
Ea1=VT-Ia1*Racir; // Armature emf
Ia2=Ia1*T2/T1; // Armature current
Ea2=Ea1*n1/n2;
RDB=(Ea2-Ia2*Racir)/Ia2; // Resistance
//Display result on command window
printf("\n Resistance of the dynamic braking resistor = %0.3f Ohm ",RDB);
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