1 files changed, 70 insertions, 0 deletions
diff --git a/3731/CH6/EX6.9/Ex6_9.sce b/3731/CH6/EX6.9/Ex6_9.sce
new file mode 100644
index 000000000..c478d4446
--- /dev/null
+++ b/3731/CH6/EX6.9/Ex6_9.sce
@@ -0,0 +1,70 @@
+//Chapter 6:Induction Motor Drives
+//Example 9
+clc;
+clf();
+//Variable Initialization
+
+//Ratings of the star connected squirrel Induction motor
+f=50           // frequency in HZ
+Vl=400         // line voltage in V
+P=4            // number of poles
+N=1370         // rated speed
+
+//Frequency variation is from 10 Hz to 50 Hz
+fmin=10     
+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
+
+//Solution
+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
+
+//(i)to obtain the plot between the breakdown torque and the frequency
+K=0.1
+k=[]
+frequency=[]
+torque=[]
+for i=0:8
+K=K+0.1
+f1=K*f
+x=Rs/K+sqrt((Rs/K)**2+(Xs+Xr_)**2)
+Tmax=(3/2/Wms)*(Vl/sqrt(3))**2/x
+k($+1)=K
+frequency($+1)=f1
+torque($+1)=Tmax
+end
+disp(k,"K:")
+disp(frequency,"f:in Hz")
+disp(torque,"Tmax:in N-m")
+
+//Plotting the values of Tmax vs f 
+plot(frequency,torque)
+xgrid(2)
+xlabel('f,Hz')
+ylabel('Tmax,N-m')
+title('Torque  vs frequency characteristic')
+
+//(ii) to obtain the starting torque and current at rated frequency and voltage
+x=(Rs+Rr_)**2+(Xs+Xr_)**2
+Tst=(3/Wms)*(Vl/sqrt(3))**2*Rr_/x     //starting torque at 50 Hz frequency
+Ist=(Vl/sqrt(3))/sqrt(x)         //starting current at 50 Hz frequency
+
+K=fmin/fmax     //minimum is available at 10 Hz
+y=((Rs+Rr_)/K)**2+(Xs+Xr_)**2
+Tst_=(3/Wms)*(Vl/sqrt(3))**2*Rr_/K/y     //starting torque at 10 Hz frequency
+Ist_=(Vl/sqrt(3))/sqrt(y)           //starting current at 10 Hz frequency
+
+ratio1=Tst_/Tst    //ratio of starting torque to the rated starting torque
+ratio2=Ist_/Ist    //ratio of starting current to the rated starting current
+
+//Results
+mprintf("\n(i)Hence from the plot we can see that for a constant (V/f) ratio breakdown torque decreases with frequency")
+mprintf("\n(ii)Hence the required ratio of starting torque to the rated starting torque is :%.3f",ratio1)
+mprintf("\nHence the required ratio of starting current to the rated starting current is :%.2f",ratio2)