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+//Chapter 6:Induction Motor Drives
+//Example 8
+clc;
+
+//Variable Initialization
+
+//Ratings of the delta connected Induction motor
+f=50           // frequency in HZ
+Vl=400         // line voltage in V
+P=4            // number of poles
+Pm=2.8*1000    // rated mechanical power developed in W
+N=1370         // rated speed in rpm
+
+//Parameters referred to the stator
+Xr_=5          // rotor winding reactance in ohm
+Xs=Xr_         // stator winding reactance in ohm
+Rr_=5          // resistance of the rotor windings in ohm
+Rs=2           // resistance of the stator windings in ohm
+Xm=80          // no load reactance in ohm
+
+//Solution
+Ns=120*f/P                    //synchronous speed in rpm
+Wms=2*%pi*Ns/60           //synchronous speed in rad/s
+s=(Ns-N)/Ns                   //full load slip
+x=(Rs+Rr_/s)**2+(Xs+Xr_)**2   //total impedance
+T=(3/Wms)*(Vl**2*Rr_/s)/x     //full load torque
+Tl=T
+K=Tl/(1-s)**2                 //since Tl=K*(1-s)**2
+
+//(i) When the motor is running at 1200 rpm
+N1=1200            //speed in rpm
+s1=(Ns-N1)/Ns      //slip at the given speed N1
+Tl=K*(1-s1)**2     //torque at the given speed N1
+
+y=(Rs+Rr_/s1)**2+(Xs+Xr_)**2   //total impedance
+a=Tl*(Wms/3)*y*(s1/Rr_)        //Since T=(3/Wms)*(Vl**2*Rr_/s)/x      and a=V**2
+V=sqrt(a)                 //required voltage at the given speed N1
+Ir_=V/((Rs+Rr_/s1)+%i*(Xs+Xr_))//rotor current
+Im=V/(%i*Xm)                   //magnetizing current
+Is=Ir_+Im                      //total current
+Il=abs(Is)*sqrt(3)        //line current
+
+//(ii)When the terminal voltage is 300 V
+V1=300  //terminal voltage in V
+x=(Rs+Rr_)**2+(Xs+Xr_)**2   
+T=(3/Wms)*(V1**2*Rr_)/x
+
+//Now we have to solve for the value of slip 's' from the given equation 104s**4- 188s**3 + 89s**2 - 179s + 25=0"
+coeff = [104,-188,89,-179,25]    //coeffcient of the polynomial equation 
+s=[]
+s=roots(coeff)                //roots of the polynomial equation
+
+T=K*(1-real(s(4)))**2     //torque at the given terminal voltage of 300 V
+N=Ns*(1-real(s(4)))       //speed at the given terminal voltage of 300 V
+Ir_=V1/((Rs+Rr_/real(s(4)))+%i*(Xs+Xr_))//rotor current
+Im=V1/(%i*Xm)                   //magnetizing current
+Is=Ir_+Im                       //total current
+Il1=abs(Is)*sqrt(3)        //line current
+
+
+//Results
+mprintf("(i)Required torque is Tl:%.1f N-m",Tl)
+mprintf("\nRequired motor terminal voltage is V: %.1f V",V)
+mprintf("\nRequired line current is Il:%.2f A",Il)
+mprintf("\n(ii)The roots of the polynomial equation are s1:%.3f s2:%.3f s3:%.3f s4:%.3f",real(s(1)),real(s(2)),real(s(3)),real(s(4)))
+mprintf("\nHence Only s4: %.3f is valid",real(s(4)))
+mprintf("\nRequired torque is Tl:%.2f N-m",T)
+mprintf("\nRequired speed is N:%.1f rpm",N)
+mprintf("\nRequired line current is Il:%.2f A",Il1)