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+// Electric Machinery and Transformers
+// Irving L kosow 
+// Prentice Hall of India
+// 2nd editiom
+
+// Chapter 12: POWER,ENERGY,AND EFFICIENCY RELATIONS OF DC AND AC DYNAMOS
+// Example 12-9
+
+clear; clc; close; // Clear the work space and console.
+
+// Given data
+V = 240 ; // Voltage rating of dc shunt motor in volt
+I_L = 55 ; // Rated line current in A 
+S = 1200 ; // Speed in rpm of the dc shunt motor
+P_r = 406.4 ; // Rotational losses in W at rated load
+R_f = 120 ; // Field resistance in ohm
+R_a = 0.4 ; // Armture resistance in ohm
+
+// Calculations
+// case a
+
+V_f = V ; // Voltage across field winding in volt
+I_f = V_f / R_f ; // Field current in A
+I_a = I_L - I_f ; // Rated armature current in A
+
+V_a = V ; // Voltage across armature in volt
+E_c = V_a - I_a*R_a ; // back EMF in volt
+P_d = E_c * I_a ; // Power developed by the armature in W
+
+// case b
+P_o = P_d - P_r  ; // Rated output power in W
+P_o_hp = P_o / 746 ; // Rated output power in hp
+
+// case c
+T_o = (P_o_hp * 5252)/S ; // C in lb-ft
+T_o_Nm = T_o * (1.356); // Rated output torque in N-m
+
+// case d
+P_in = V*I_L ; // Input power in W
+eta = (P_o/P_in)*100 ; // Efficiency at rated load
+
+// case e
+// At no-load
+P_o_nl = 0 ;
+P_r_nl = P_r ; // Rotational losses in W at no load
+P_d_nl = P_r_nl ;
+
+I_a_nl = P_d_nl / V_a ; // No-load armature current in A
+
+E_c_nl = V ; // No-load voltage in volt
+E_c_fl = E_c ; // Full-load voltage in volt
+S_fl = S ; // Full-load speed in rpm
+S_nl = (E_c_nl / E_c_fl)*S_fl ; // No-load speed in rpm
+
+// case f
+SR = (S_nl - S_fl)/S_fl * 100 ; // Speed regulation
+
+// Display the results
+disp("Example 12-9 Solution : ");
+
+printf(" \n a: E_c = %.1f V \n ",E_c );
+printf(" \n    Power developed by the armature at rated load :\n    P_d = %.1f W \n ",P_d);
+
+printf(" \n b: Rated output power :\n    P_o = %d W \n ", P_o );
+printf(" \n    P_o = %d hp \n ",P_o_hp);
+
+printf(" \n c: Rated output torque :\n    T_o = %.2f lb-ft ",T_o);
+printf(" \n    T_o = %.f N-m \n ",T_o_Nm );
+
+printf(" \n d: Efficiency at rated load :\n    η = %.1f percent \n ",eta );
+
+printf(" \n e: At no-load, P_o = %d W ; therefore\n\t\tP_d = P_r = EcIa ≅ VaIa = %.1f W \n",P_o_nl,P_r);
+printf(" \n    No-load armature current :\n    I_a(nl) = %.3f A \n ",I_a_nl );
+printf(" \n    No-load speed :\n    S_nl = %f ≃ %.f rpm \n ",S_nl,S_nl );
+
+printf(" \n f: Speed regulation :\n    SR = %.1f percent ",SR );
+
+printf(" \n    Variation in SR is due to non-approximation of S_nl = %f rpm",S_nl);
+printf(" \n    while calculating SR in scilab .")