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+//Chapter 5:Dc Motor Drives
+//Example 17
+clc;
+
+//Variable Initialization
+
+//Ratings of the separately excited motor
+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=440   // line  voltage inV with 3-phase ac supply
+f=50     //frequency of the source voltage in Hz
+
+//Solution
+//(i) Tranformer ratio
+alpha=0    //firing angle in degrees
+Va=V       //motor terminal voltage is equal to the rated voltage when the firing angle is 0 degrees
+Vm=%pi/3*Va/cos(alpha)
+Vrms=Vm/sqrt(2)        //rms value of the converter input voltage
+a=(Vl/sqrt(3))/Vrms    //required transformer ratio
+
+//(ii)Value of the firing angle
+E=V-Ia*Ra      //back emf at the rated speed
+
+//(a)When the speed of the motor is 1200 rpm and rated torque
+N1=1200        //speed of the motor i rpm
+E1=N1/N*E      //back emf at the given speed N1
+Va=E1+Ia*Ra    //terminal voltage at the given speed N1
+alpha=acos(%pi/3*Va/Vm)  //required firing angle in radians
+alpha1=alpha*180/%pi         //required firing angle in degrees
+
+//(b)When the speed of the motor is -800 rpm and twice the rated torque
+N1=-800        //speed of the motor in rpm
+E1=N1/N*E      //back emf at the given speed N1
+Ia=2*Ia        //torque is directly proportional to the current hence twice the rated current
+Va=E1+Ia*Ra    //terminal voltage at the given speed N1
+alpha=acos(%pi/3*Va/Vm)  //required firing angle in radians
+alpha2=alpha*180/%pi         //required firing angle in degrees
+
+
+//Results
+mprintf("(i)Hence the required transformer ratio is :%.3f",a)
+mprintf("\n(ii)(a)Hence the required firing angle is :%.2f °",alpha1)
+mprintf("\n(b)Hence the required firing angle is :%.2f °",alpha2)