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+
+clc;
+Pout=40000;//output power
+V=250;//supply voltage in volts
+r=0.2;//sum of armature circuit resistance & series field circuit resistance
+n=1500;//speed of dc series motor at rated current
+
+//PART(a)-
+
+Ir=Pout/V;//rated current
+Ea=V-Ir*r;//counter emf at rated load
+Wm=(2*%pi*n)/60;//angular speed of rotation of motor
+Te=round((Ea*Ir)/Wm);//rated electromagnetic torque in Nm.
+//Now the relation giving the torque speed characteristics of series motor must be developed.
+//Since the magnetic saturation is neglected
+//Te=Ka*phi*I
+//Te=K1*Ia^2
+K1=Te/(Ir^2);//Ia=rated current
+//Ea=K2*phi*n=K2*Ia*n
+K2=Ea/(Ir*n);// values of constant of proportionality 
+//The values of constants k1 & K2 are obtained from rated conditions
+//Ia=(V-Ea)/r & Ea=K2*Ia*n ; Ia=1250-0.00454*Ia*n
+//Ia=1250/(1+0.00454n) ....(1); Ia=armature current at any speed
+//Te=K1*Ia^2
+n=[1400 1450 1500 1550 1600 1650 1700];
+Te=K1.*(((V/r)^2)./(1+(K2/r).*n).^2); // Electromagnetic torque
+Tl=5.*sqrt(n); // load torque
+plot(Te,n,Tl,n);
+xlabel('T(Nm)');
+ylabel('Speed(rpm)');
+title('Speed-torque characteristics for Series-motor and for load');
+
+//THE INTERSECTION OF SERIES MOTOR & LOAD CHARACTERISTICS GIVES THE OPERATING POINT
+
+//From the curve the operating point is obtained at 1591 rpm & torque is 199.5 Nm
+disp('The operating speed of motor is 1591 rpm.');
+
+//PART(b)-
+//Current drawn from the source is -
+Ia=(V/r)/(1+(K2/r)*1591);//From equation (1)
+printf('Current drawn from the source is %f A.',Ia);