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+//Book Name: Fundamentals of electrical drives by Mohamad A. El- Sharkawi
+//chapter 7
+//example 7.1
+//edition 1
+//publisher and place:Nelson Engineering
+clc;
+clear;
+V=480;//terminal voltage in volt
+p=6;//number of poles
+f=60;//frequency in hertz
+Pout=30*746;//rated output voltage in volts
+R1=0.5;//stator resistance in ohm
+R2=0.5;//rotor resistance reffered to stator in ohm
+Protational=500;//rotational loss in watt
+Pcu=600;//core losses in watt
+c=0.05;//cost of energy
+t1=100;//time which the motor operates in a week
+Pd=Pout+Protational;//developed power in watt
+a=1;// the s^2 value from the equation s^2-s+0.039
+b=-1;//the s value from the equation s^2-s+0.039
+c=0.039;//the constant value from the equation s^2-s+0.039
+s1=(-(b)+sqrt((b)^2-(4*a*c)))/(2*a);
+s2=(-(b)-sqrt((b)^2-(4*a*c)))/(2*a);//roots to find the value of s from the equation s^2-s+0.03
+s=s2;//s1 is very large hence neglected thus slip=s2
+a1=120;//constant value in the formula
+ns=(a1*f)/p;//synchronous speed in rpm
+n=ns*(1-s);
+mprintf("\nThe speed of the motor is %d rpm",n)
+I2=sqrt((Pd*s)/(3*R2*(1-s)));//motor current in amps
+Pwinding=3*I2^(2)*(R1+R2);
+Pin=Pd+Pwinding+Pcu;
+eta=Pout/Pin;//efficiency of the motor
+eta=eta*100;//efficiency in percentage
+mprintf("\nThe efficiency of the motor without added resistance is %d percentage",eta)
+nnew=0.8*n;//speed after 20% reduction
+snew=(ns-nnew)/ns;
+rmsnew=nnew/60;//speed in rps
+omegadnew=(2*%pi*rmsnew);
+rps=n/60;//speed in rps
+omega=(2*%pi*rps);
+Pdnew=(Pd*omegadnew)/omega;
+Radd=R2*((snew-s)/s);//resistance added to reduce 20% of the speed
+mprintf("\nThe resistance added to reduce 20 percentage of the speed is %f ohm",Radd)
+I2new=sqrt((Pdnew*snew)/(3*(R2+Radd)*(1-snew)))
+Pwindingnew=3*I2^(2)*(R1+R2+Radd);
+Pinnew=Pdnew+Pwindingnew+Pcu;
+Poutnew=Pdnew-Protational;
+etanew=Poutnew/Pinnew;
+etanew=etanew*100;
+mprintf("\nThe efficiency of the motor with added resistance is %d percentage",etanew)
+Padd=3*I2^(2)*Radd;
+Padd=Padd*10^(-3);
+t=100*52;//total hours of operation in one year
+C=Padd*t*c;
+mprintf("\nThe annual cost of the operating motor is $%f",C)
+//The answer may vary due to roundoff error
+