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+
+//Chapter 5:Dc Motor Drives
+//Example 12
+clc;
+
+//Variable Initialization
+
+//Ratings of the 2-pole separately excited DC motor with the fields coils connected in parallel
+V=220      // rated voltage in V
+N=750      // rated speed in rpm
+Ia1=100    // rated current in A
+Ra=0.1     // armature resistance in ohms
+
+//Solution
+E1=V-Ia1*Ra            //rated back emf at rated operation
+Wm1=2*%pi*N/60     //angular speed
+Trated=E1*Ia1/Wm1      //rated torque
+Ke_phi1=E1/Wm1
+
+//(i) When the armature voltage is reduced to 110V
+Wm2=2*%pi*N/60    //angular speed
+E2=Ke_phi1*Wm2
+//Now there are two linear equations...that we have to solve
+//They are given by 0.3*N2+2.674*Ia2=500 and 0.28*N2+0.1*Ia2=110
+a = [0.3,2.674;0.28,0.1]
+b = [500;110]
+x = inv(a)*b
+N2=x(1)      //let the motor speed be N2
+Ia2=x(2)     //let the motor current be Ia2
+
+//(ii)When the field coils are connected in series
+K=Ke_phi1/2
+Wm3=2*%pi*N/60    //angular speed
+E3=K*Wm3
+//Now there are two linear equations...that we have to solve"
+//They are given by 0.3*N3+1.337*Ia3=500 and 0.14*N3+0.1*Ia3=220"
+a = [0.3,1.337;0.14,0.1]
+b = [500;220]
+x = inv(a)*b
+N3=x(1)            //let the motor speed be N3
+Ia3=x(2)           //let the motor current be Ia3
+
+//Results
+mprintf("(i)Hence the motor armature current is Ia2 :%.1f A",Ia2)
+mprintf("\nAnd the required speed is N2 :%.1f rpm",N2)
+mprintf("\n(ii)Hence the motor armature current is Ia3 :%.1f A",Ia3)
+mprintf("\nAnd the required speed is N3 :%.1f rpm",N3)