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//Chapter 7:Synchronous Motor and Brushless DC Motor Drives
//Example 2
clc;
//Variable Initialization
//Ratings of the synchronous motor is same as that of Example-7.1
Pm1=500*1000 // power rating in W
f=50 // frequency in HZ
Vl=3.3*1000 // line voltage in V
pf=0.8 // power factor lagging
P=4 // number of poles
I=10 // field current in A
Xs=15 // reactance of the windings in ohm
Rs=0 // resistance of the windings in ohm
Pm=Pm1/2 // power at half the rated torque when the losses are neglected
//Solution
Wms=50*%pi // synchronous speed in rad/sec
V=Vl/sqrt(3) // phase voltage
Is=Pm1/(sqrt(3)*Vl*pf) //rated current
rad=acos(pf)
Is=Is * (cos(-rad) + sin(-rad)*%i) //rated current in vector form
V=V * (cos(0) + sin(0)) //rated phase voltage in rectangular form
E=V-Is*%i*Xs //back emf
//(i) at rated current and unity power factor
E1=V-abs(Is)*%i*Xs
delta=phasemag(E1) //phase angle of E1
nd=delta*%pi/180
Pm=3*abs(V)*abs(E1)*sin(nd)/Xs //mechanical power developed
T=Pm/Wms //braking torque
If=abs(E1)/abs(E)*I //field current
//(ii) at field current of 15A and 500kW output
If1=15 //field current
Pm=-500*1000 //output power
E2=If1/I*abs(E)
sin_delta=Pm*Xs/(3*abs(V)*abs(E2))
delta=asin(sin_delta) //angle delta
Is=((E2*(cos(abs(delta))+sin(abs(delta))*%i))-V)/(%i*Xs) //armature current
Isn=phasemag(Is)
x=(Isn)*%pi/180 //phase angle of Is
power_factor=cos(x) //power factor
//Results
mprintf("i)Braking torque :%.1f N-m",T)
mprintf("\nField current:%.2f A",If)
mprintf("\nii)Armature current :%.2f %.2f ° A",abs(Is),Isn)
mprintf("\nPower factor:%.3f lagging",power_factor)
//Note :There is a slight difference in the answers
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