# Ch-8 : Thyristors¶

## Page No. 210 Example 8.1.¶

In :
from math import asin,pi,cos
Vm=220.
V1=110.
RL=100.
print "We have,"
print "                  V1 = Vm*sin(theta)"
print "Therefore,"
x=asin(V1/Vm)*pi/180
print " Firing angel, theta =%0.2f"%x
ca=180-x
print "    Conduction angle = 180 - theta = %0.2f"%ca
print "Average voltage, Vav = (Vm/2pi) * (1+cos(theta))"
Vav = (Vm/(2*pi))*(1+cos(x*pi/180))
print "              Vav = %0.2f V"%Vav
Iav=Vav/RL
print "Average current,  Iav = Vav / RL =%0.2f A"%Iav
po=Vav*Iav
print "Power output = Vav*Iav = %0.2f W"%po
print "The time during which the SCR remains OFF is"
t=1./(2*6*50)
t1=t*10**3
print "       t = %0.2f ms"%t1

We have,
V1 = Vm*sin(theta)
Therefore,
Firing angel, theta =0.01
Conduction angle = 180 - theta = 179.99
Average voltage, Vav = (Vm/2pi) * (1+cos(theta))
Vav = 70.03 V
Average current,  Iav = Vav / RL =0.70 A
Power output = Vav*Iav = 49.04 W
The time during which the SCR remains OFF is
t = 1.67 ms


## Page No. 211 Example 8.2.¶

In :
from math import sqrt,pi,acos
Vdc=150.
Vm=230*sqrt(2)
RL=10.
print "For an SCR full wave rectifier,"
print "            Vdc = (Vm/pi)*(1+cos(theta))"
x=acos(((Vdc*pi)/Vm)-1)*pi/180
print "Therefore,    theta =%0.2f"%x
print "For 50Hz, T = 20 ms for 360"
t = (20./360)*x
print "Therefore      t = (20*10**3/360)*63.34 = %0.2e ms"%t
Iav=Vdc/RL
print "Load current,    Iav = Vav / RL = %0.2f A"%Iav

For an SCR full wave rectifier,
Vdc = (Vm/pi)*(1+cos(theta))
Therefore,    theta =0.02
For 50Hz, T = 20 ms for 360
Therefore      t = (20*10**3/360)*63.34 = 1.07e-03 ms
Load current,    Iav = Vav / RL = 15.00 A


## Page No. 212 Example 8.3.¶

In :
from math import sqrt
Vm=400
PIV=sqrt(3)*Vm
print "As the supply voltage is 400 sin 314t, Vm = 400 V"
print "Peak inverse voltage(PIV) = sqrt(3)*Vm =%0.2f V"%PIV
RMS=20
ff=1.11
Iav=round(RMS/ff)
print "RMS value of current = 20 V"
print "Average value of current, Iav = RMS value/form factor =%0.2f A"%Iav
pr=PIV*Iav
pr1=pr*10**-3
print "Power rating of the SCR(kW) = PIV * Iav =%0.2f kW"%pr1

As the supply voltage is 400 sin 314t, Vm = 400 V
Peak inverse voltage(PIV) = sqrt(3)*Vm =692.82 V
RMS value of current = 20 V
Average value of current, Iav = RMS value/form factor =18.00 A
Power rating of the SCR(kW) = PIV * Iav =12.47 kW