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+//Chapter 5:Dc Motor Drives
+//Example 18
+clc;
+
+//Variable Initialization
+
+//The separately excited motor  is fed from a circulating dual converter
+V=220    // rated voltage in V
+N=1500   // rated speed in rpm
+Ia=50    // rated current in A
+Ra=0.5   // armature resistance in ohms
+Vl=165   // line  voltage in V
+f=50     // frequency of the source voltage in Hz
+
+//Solution
+E=V-Ia*Ra            //back emf at the rated speed
+Vm=Vl*sqrt(2)   //peak voltage
+
+//(i)During motoring operation when the speed is 1000 rpm and at rated torque
+N1=1000        //speed of the motor in rpm
+E1=N1/N*E      //back emf at the given speed N1
+Va=E1+Ia*Ra    //terminal voltage at the given speed N1
+alpha_A=acos(%pi/3*Va/Vm)
+alpha_A=alpha_A*180/%pi//required converter firing angle in degrees
+alpha_B=180-alpha_A
+
+//(ii)During braking operation when the speed is 1000 rpm and at rated torque
+N1=1000        //speed of the motor in the book is given as 100 rpm which is wrong
+E1=N1/N*E      //back emf at the given speed N1
+Va=E1-Ia*Ra    //terminal voltage at the given speed N1
+alpha_A1=acos(%pi/3*Va/Vm)
+alpha_A1=alpha_A1*180/%pi//required converter firing angle in degrees
+alpha_B1=180-alpha_A1
+
+//(iii)During motoring operation when the speed is -1000 rpm and at rated torque
+N1=-1000        //speed of the motor in rpm
+E1=N1/N*E      //back emf at the given speed N1
+Va=E1-Ia*Ra    //terminal voltage at the given speed N1
+alpha_A2=acos(%pi/3*Va/Vm)
+alpha_A2=alpha_A2*180/%pi//required converter firing angle in degrees
+alpha_B2=180-alpha_A2
+
+//(iv)During braking operation when the speed is -1000 rpm and at rated torque
+N1=-1000       //speed of the motor in the book it is given as 100 rpm which is wrong
+E1=N1/N*E      //back emf at the given speed N1
+Va=E1+Ia*Ra    //terminal voltage at the given speed N1
+alpha_A3=acos(%pi/3*Va/Vm)
+alpha_A3=alpha_A3*180/%pi//required converter firing angle in degrees
+alpha_B3=180-alpha_A3
+
+//Results
+mprintf("\n(i)Hence the required firing angle is :%.1f °",alpha_B)
+mprintf("\n(ii)Hence the required firing angle is :%.1f °",alpha_B1)
+mprintf("\n(iii)Hence for negative speed during motoring operation the required firing angles are :")
+mprintf("\nalpha_A :%.1f ° and alpha_B :%.1f °",alpha_A2,alpha_B2)
+mprintf("\n(iv)Hence for negative speed during braking operation the required firing angles are :")
+mprintf("\nalpha_A :%.1f ° and alpha_B :%.1f °",alpha_A3,alpha_B3)