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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 4-21
+
+clear; clc; close; // Clear the work space and console.
+
+// Given data
+S_int = 1603 ; // Internal rated speed in rpm (Ex.4-16)
+S_ext = 1250 ; // External rated speed in rpm (Ex.4-16)
+hp_int = 14.3 ; // Internal horsepower
+hp_ext = 10 ; // External horsepower
+
+// Calculations
+T_int = ( hp_int * 5252 ) / S_int ; // Internal torque in lb-ft
+
+T_ext = ( hp_ext * 5252 ) / S_ext ; // External torque in lb-ft
+
+// Display the results
+disp("Example 4-21 Solution : ");
+printf(" \n a: T_int = %.2f lb-ft \n ", T_int );
+printf(" \n b: T_ext = %.2f lb-ft \n ", T_ext );
+printf(" \n c: Internal horsepower is developed as a result of electromagnetic");
+printf(" \n    torque produced by energy conversion. Some of the mechanical energy");
+printf(" \n    is used internally to overcome mechanical losses of the motor,");
+printf(" \n    reducing the torque available at its shaft to perform work.");