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+//Chapter 5:Dc Motor Drives
+//Example 6
+clc;
+
+//Variable Initialization
+
+//The motor rating is same as that of Ex-5.5
+N=600      //value of the speed given from the magnetization curve in Ex-5.5
+
+Ra=0.04    //armature resistance in ohms
+Rf=10      //field resistance in ohms
+T=400      //load torque in N-m
+N1=1200    //given speed in rpm to hold the overhauling torque
+
+//Solution
+Wm=2*%pi*N1/60    //angular speed at the given speed N1
+
+//Magnetisation curve at N=600rpm
+If=[2.5,5,7.5,10,12.5,15,17.5,20,22.5,25]       //field current in A
+E =[25,50,73.5,90,102.5,110,116,121,125,129]    //value of the back emf as given in Ex-5.5 for the speed N in V
+
+//Magnetisation curve at N=1200rpm
+If=[2.5,5,7.5,10,12.5,15,17.5,20,22.5,25]       //field current in A
+E1=N1/N*E                           //back emf at the speed N1
+mprintf("Hence the magnetization curve at 1200rpm is")
+disp(If,"Field current   If:in A")
+disp(E1,"Back emf is     E1 in V:")
+
+Pd=T*Wm                               //power developed
+x=Pd*Ra
+V=[]
+for i=1:10
+V($+1)=E1(i)-x/E1(i)
+end
+disp(V,"Terminal voltage V:in V")
+
+//Results
+//Plotting the values of V vs If
+subplot(2,1,1)
+plot(V,If)
+xlabel('Terminal voltage V')
+ylabel('Field current I_f')
+title('V vs If')
+xgrid(2)
+
+//Plotting the values of E vs If
+If=[2.5,5,7.5,10,12.5,15,17.5,20,22.5,25]       //field current in A
+E =[25,50,73.5,90,102.5,110,116,121,125,129]    //value of the back emf as given in Ex-5.5 for the speed N in V
+E1=N1/N*E                           //back emf at the speed N1
+
+subplot(2,1,2)
+plot(E1,If,'y')
+xlabel('E')
+ylabel('Field current I_f')
+title('E vs If')
+xgrid(2)
+
+mprintf("\nFrom the plot we can see that when the current If=25 A the terminal voltage is V=250 V with the back emf E=258V")
+
+E=258           //value of the back emf in V at from the plot 
+V=250           //value of terminal voltage in V from the plot at E=258 V
+If=25           //value of If in A from the plot at E=258 V
+Ia=(E-V)/Ra     //armature current
+If=V/Rf         //field current
+Ir=Ia-If 
+Rb=V/Ir         //braking resistance
+
+mprintf("\nHence the rquired braking resistance is %.3f ohm",Rb)