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//Chapter 6:Induction Motor Drives
//Example 7
clc;
//Variable Initialization
//Ratings of the Star connected Induction motor
f=50 // frequency in HZ
Vl=2200 // line voltage in V
P=6 // number of poles
//Parameters referred to the stator
Xr_=0.5 // rotor winding reactance in ohm
Xs=Xr_ // stator winding reactance in ohm
Rr_=0.12 // resistance of the rotor windings in ohm
Rs=0.075 // resistance of the stator windings in ohm
J=100 // combine inertia of motor and load in kg-m2
//Solution
//(i) During starting of the motor
Sm=Rr_/sqrt(Rs**2+(Xs+Xr_)**2) //slip at maximum torque
Wms=4*%pi*f/P //angular frequency
x=Rs+sqrt(Rs**2+(Xs+Xr_)**2)
Tmax=(3/2/Wms)*(Vl/sqrt(3))**2/x //maximum torque
tm=J*Wms/Tmax //mechanical time constant of the motor
ts=tm*(1/4/Sm+1.5*Sm) //time taken during starting
Es=1/2*J*Wms**2*(1+Rs/Rr_) //energy disspated during starting
//(ii) When the motor is stopped by plugging method
tb=tm*(0.345*Sm+0.75/Sm) //time required to stop by plugging
Eb=3/2*J*Wms**2*(1+Rs/Rr_) //energy disspated during braking
//(iii)Required resistance to be inserted during plugging
tb1=1.027*tm //minimum value of stopping time during braking
x=1.47*(Xs+Xr_) //x=Rr_+Re
Re=x-Rr_ //Re is the required external resistance to be connected
Ee=3/2*J*Wms**2*(Re/(Re+Rr_)) //energy disspated in the external resistor
Eb1=Eb-Ee //total energy disspated during braking
//Results
mprintf("(i)Time taken during starting is ts:%.4f s",ts)
mprintf(" \nEnergy dissipated during starting is Es:%d kilo-watt-sec",Es/1000)
mprintf("\n\n(ii)Time taken to stop by plugging is tb:%.2f s",tb)
mprintf(" \nEnergy dissipated during braking is Eb:%d kilo-watt-sec",Eb/1000)
mprintf("\n\n(iii)Minimum Time taken to stop by plugging is tb:%.2f s",tb1)
mprintf(" \nRequired external resistance to be connected is Re:%.2f ohm",Re)
mprintf(" \nTotal Energy dissipated during braking is Eb:%.2f kilo-watt-sec",Eb1/1000)
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