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+//Book Name: Fundamentals of electrical drives by Mohamad A. El- Sharkawi
+//chapter 7
+//example 7.8
+//edition 1
+//publisher and place:Nelson Engineering
+clc;
+clear;
+V=480;//terminal voltage in volt
+p=2;//number of poles
+f=60;//frequency in hertz
+fd=50;//decreased frequency in Hz
+Xeq=4;//inductive reactance in ohm
+R1=0.2;//stator resistance in ohm
+R2=0.3;//rotor resistance reffered to stator in ohm
+Td=60;//driving constant load torque in Nm
+n=3500;//speed of the motor in rpm
+VFR=V/f;//voltage frequency ratio
+Vnew=fd*VFR;
+a=120;//constant value
+ns=(a*fd)/p;//synchronous speed in rpm
+Vs=V/sqrt(3);
+rps=n/60;
+omegas=(2*%pi*rps);
+s=(Td*omegas*R2)/Vnew^2;
+n=ns*(1-s);//the new motor speed at 50Hz in rpm
+rpss=ns/60;
+omega=(2*%pi*rpss)/60;
+mprintf("\nTo compute the starting current at 60Hz,480v:")
+I2st=Vs/sqrt((R1+R2)^(2)+Xeq^(2));//starting current in A
+mprintf("\nThe starting current at 60Hz,480v is %f A",I2st)
+mprintf("\nTo compute the starting current at 50Hz,400v:")
+Vsnew=Vnew/sqrt(3);
+Xeqnew=(fd/f)*Xeq;//inductive reactance at 50Hz
+I2stnew=Vsnew/sqrt((R1+R2)^(2)+Xeqnew^(2));//starting current at 50Hz in A
+mprintf("\nThe starting current at 50Hz,400v is %f A",I2stnew)
+mprintf("\nThe starting current is almost unchanged due to the v/f control")