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//Chapter 7:Synchronous Motor and Brushless DC Motor Drives
//Example 4
clc;
//Variable Initialization
//Ratings of the synchronous motor
Pm=8*10**6 // power rating in W
f=50 // frequency in HZ
Vl=6600 // line voltage in V
pf=1 // unity power factor
P=6 // number of poles
I=10 // rated field current in A
Xs=2.8 // reactance of the windings in ohm
Rs=0 // resistance of the windings in ohm
Rd=0.1 // Dc link inductor resistance in ohms
alpha=140 // constant firing angle in degrees
//Solution
N=120*f/P //synchronous speed
V=Vl/sqrt(3) //phase voltage
Is=Pm/(sqrt(3)*Vl*pf) //rated current
Id=%pi/sqrt(6)*Is //Dc line current
phi=180-alpha //phase angle between Is and V in degrees
//(i) When motor operates at rated current and 500rpm
N1=500 //motor speed in rpm
f1=N1/N*f //frequency at N1
V1=f1/f*V //voltge at N1
phi=phi*%pi/180
Pm1=3*V1*Is*cos(phi) //power developed by the motor
//for the 3-phase load commutated inverter
alpha=alpha*%pi/180
Vdl=(3*sqrt(6)/%pi)*V1*cos(alpha)
Vds=-Vdl+Id*Rd
cos_alpha_s=Vds/(3*sqrt(6)/%pi*V)
alpha_s=acos(cos_alpha_s) //in radian
alpha_s1=alpha_s*180/%pi
//(ii) Regenerative braking at 500rpm and at rated motor current
alpha=0 //firing angle
//When firng angle is zero then power factor is unity
pf=1
Pm2=3*V1*Is*pf //power developed by the motor
Ps=Pm2-Id**2*Rd //power supplied to the source
Vdl=(3*sqrt(6)/%pi)*V1*cos(alpha)
Vds=-Vdl+Id*Rd
cos_alpha_s=Vds/(3*sqrt(6)/%pi*V)
alpha_s=acos(cos_alpha_s) //in radian
alpha_s2=alpha_s*180/%pi //in degrees
//Results
disp('W',Pm1,"i)Power developed by the motor is:")
disp('°',alpha_s1,"Source side converter firing angle is")
disp('W',Ps,"ii)Power supplied to the source is:")
disp("°",alpha_s2,"Source side converter firing angle is")
//Answer given for firing angle in the book is wrong
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