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+//Chapter 6:Induction Motor Drives
+//Example 10
+clc;
+clf();
+//Variable Initialization
+//ratings of the star connected squirrel Induction motor is 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
+
+//the frequency variation is from 5 Hz to 50 Hz
+fmin=5     
+fmax=50
+//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
+
+//calculation
+Ns=120*f/P     //synchronous speed
+N1=Ns-N        //increase in speed from no load to full torque rpm
+Wms=2*%pi*Ns/60
+s=(Ns-N)/Ns    //full load slip
+Tmax=54.88   //maximum torque as obtain from Ex-6.9
+
+//to obtain the plot between the voltage and the frequency
+K=0
+k=[]
+frequency=[]
+line_voltage=[]
+for i=0:9
+K=K+0.1
+f1=K*f
+x=2*K*Wms*Tmax/3
+y=Rs+sqrt((Rs)**2+(K*(Xs+Xr_))**2)
+Vl_square=3*x*y
+Vl=sqrt(Vl_square)
+k($+1)=K
+frequency($+1)=f1
+line_voltage($+1)=Vl
+end
+disp(k,"K:")
+disp(frequency,"f:in Hz")
+disp(line_voltage,"Vl:in V")
+
+//Plotting the values of line voltage Vl vs f 
+plot(frequency,line_voltage,'b')
+xlabel('f,Hz')
+ylabel('Line voltage,volts')
+xgrid(2)
+title('Line voltage  vs Frequency characteristic')
+//for constant V/f ratio
+x=[0,10,20,30,40,50]
+y=[0,80,160,240,320,400]
+plot(x,y,'--')
+str=["$\underleftarrow{\huge{Constant V/f  ratio}}$"]
+xstring(21,160,str)
+
+mprintf("\nHence for a constant breakdown torque at all frequencies,")
+mprintf("\nV/f ratio has to be progressively increased with increase in frequency")