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//Chapter 7:Synchronous Motor and Brushless DC Motor Drives
//Example 1
clc;
//Variable Initialization
//Ratings of the synchronous motor
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
Wms=50*%pi // synchronous speed in rad/sec
Pm=Pm1/2 // power at half the rated torque when the losses are neglected
//Solution
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) When field current has not changed
sin_delta=Pm*Xs/(3*abs(V)*abs(E))
delta=asin(sin_delta) //angle delta
Is=(V-(abs(E) * (cos(-delta) + sin(-delta)*%i)))/(%i*Xs) //armature current
Is1=[]
Is1(1)=abs(Is)
Isp=phasemag(Is)
x=Isp
n1=x*%pi/180
power_factor=cos(n1) //power factor
//(ii) At unity power factor and rated torque
cos_phi=1
Is=Pm1/(3*V) //since Pm1=3*V*Is
E1=V-Is*%i*Xs
If=abs(E1)/abs(E)*I //field current
//(iii) At the field current of 12.5 A
If1=12.5 //field current
E2=If1/I*abs(E)
Is=sqrt(E2**2-abs(V)**2)/Xs //since E2=abs(V-Is*1j*Xs)
Pm=3*abs(V)*Is*cos_phi //power output at the given field current
T=Pm/Wms //required torque
//results
mprintf("i)Armature current :%.2f %.1f ° A",abs(Is1),x)
mprintf("\nPower factor:%.2f lagging",power_factor)
mprintf("\nii)Field current at unity power factor at rated torque:%.2f A",If)
mprintf("\niii)Required torque is:%.1f N-m",T)
//There is a slight difference in the answer
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