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//Chapter 6:Induction Motor Drives
//Example 13
clc;
//Variable Initialization
//Ratings of the star connected Induction motor are same as that of Ex-6.9
f=50 // frequency in HZ
Vl=400 //line voltage in V
P=4 // number of poles
N=1370 //rated speed
//Parameters referred to the stator
Xr_=3.5 // rotor winding reactance in ohm
Xs=Xr_ // stator winding reactance in ohm
Rr_=3 // resistance of the rotor windings in ohm
Rs=2 // resistance of the stator windings in ohm
//Solution
Wms=4*%pi*f/P
f1=60 //frequency in Hz during speed control of the motor
K=f1/f //the value of K at 60Hz
x=Rs+sqrt(Rs**2+K**2*(Xs+Xr_)**2)
Tmax_=3/(2*K*Wms)*(Vl/sqrt(3))**2/x //torque at 60 Hz frequency
z=Rs+sqrt(Rs**2+(Xs+Xr_)**2)
Tmax=3/(2*Wms)*(Vl/sqrt(3))**2/z //maximum torque
ratio=Tmax_/Tmax //ratio
//Result
mprintf("Ratio of Motor breakdown torque at 60Hz to rated torque at 50Hz is:%.3f",ratio)
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