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+// Electric Machinery and Transformers
+// Irving L kosow 
+// Prentice Hall of India
+// 2nd editiom
+
+// Chapter 4: DC Dynamo Torque Relations-DC Motors
+// Example 4-8
+
+clear; clc; close; // Clear the work space and console.
+
+// Given data
+V_a = 120 ; // Rated terminal voltage of the DC motor in volt
+R_a = 0.2 ; // Armature circuit resistance in ohm
+R_sh = 60 ; // Shunt field resistance in ohm
+I_l = 40 ; // Line current in A @ full load
+BD = 3 ; //  Brush voltage drop in volt
+S_orig = 1800 ; // Rated full-load speed in rpm
+
+// Calculations
+I_f = V_a / R_sh ; // Field current in A
+I_a = I_l - I_f ; // Armature current @ full load
+E_c_orig = V_a - ( I_a * R_a + BD ) ; // Back EMF @ full load
+
+I_a_a = I_a / 2 ; // Armature current @ half load
+E_c_a = V_a - ( I_a_a * R_a + BD ) ; // Back EMF @ half load
+S_a = S_orig * ( E_c_a / E_c_orig ) ; // Speed @ full load
+
+I_a_b = I_a * ( 5 / 4 ) ; // Armature current @ 125% overload
+E_c_b = V_a - ( I_a_b * R_a + BD ) ; // Back EMF @ 125% overload
+S_b = S_orig * ( E_c_b / E_c_orig ) ; // Speed @ 125% overload
+
+// Display the result
+disp("Example 4-8 Solution : ");
+
+printf(" \n a : At full load ");
+printf(" \n     S = %.1f rpm " , S_a );
+
+printf(" \n b : At 125 percenytoverload ");
+printf(" \n     S = %.1f rpm " , S_b );