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+// Example 10.12
+// Determine (a) Rated torque (b) Armature current at locked rotor if no
+// starting resistance is used (c) External resistance required in the armature
+// circuit that would limit the current and develop 200 percent rated torque
+// when starting (d) Assuming the system voltage drops to 215V, determine the 
+// locked rotor torque using the external resistor in (c)
+// Page No. 433
+
+clc;
+clear;
+close;
+
+// Given data
+n=1750;                   // Rotor speed
+P=15;                     // Hp rating of motor
+VT=230;                   // Rated voltade of the machine
+Ea=0;
+Racir=0.280;              // Armature circuit loss
+Rf=137;                   // Field resistance
+ItRated=56.2;             // Total current drawn
+VT1=215;                  // Rated voltage after drop
+
+// (a) Rated torque
+Trated=P*5252/n;
+
+// (b) Armature current
+Ia=(VT-Ea)/Racir; 
+
+// (c) External resistance required
+If=VT/Rf;                      // Field current
+IaRated=ItRated-If;            // Rated armature current
+
+Ia2=IaRated*2;                 // Armature current for 200% rated torque
+
+Rx=((VT-Ea)/Ia2)-Racir;        // External resistance required
+
+// (d) Locked rotor torque 
+If215=VT1/Rf;                  // Field current at 215V
+Ia215=(VT1-Ea)/(Racir+Rx);     // Armature current at 215V
+TD2=Trated*( (If215*Ia215) / (If*IaRated) );
+
+// Display result on command window
+
+printf("\n Rated torque = %0.1f lb-ft ",Trated);
+printf("\n Armature current = %0.1f A ",Ia);
+printf("\n Armature current for 200 percent rated torque = %0.1f A ",Ia2);
+printf("\n External resistance required = %0.2f Ohm ",Rx);
+printf("\n Locked rotor torque = %0.1f lb-ft ",TD2);
+
+
+