# Chapter 20 : Thyristors¶

## Example 20.1, Page No 902¶

In [15]:
import math
#initialisation of variables
Vs=25.0
Vtm=1.7
Rl=25.0
Ih=5*10**-3

#Calculations
Vspk=1.414*Vs
Ilpk=(Vs-Vtm)/Rl
print(" for half wave rectifier sinusodial waveform")
Ilrms=.5*Ilpk
es=Vtm+(Ih*Rl)

#Results
print(" switch-off voltage =%.2f v" %es)

 for half wave rectifier sinusodial waveform
switch-off voltage =1.82 v


## Example 20.2, Page No 905¶

In [16]:
import math

#initialisation of variables
Vs=30.0
Vd1=.7
Vg=.8
Ig=200*10**-6

#Calculations
Vspk=1.414*Vs
print(" at 5 degree")
es=Vspk*.087           #  sin5=.087
print(" at 90 degree")
es=Vspk
Vt=Vd1+Vg
print(" to trigger at es=3.7V the R2 moving contact is at the top")
es=3.7
Vr1=es-Vt
I1=1*10**-3
R1=Vr1/I1
R=Vt/I1         #R=R2+R3
es=42.4
Vr3=Vt
I1=es/(R+R1)
R3=Vt/I1
R2=R-R3

#Results
print(" To trigger at es =42.4 the R2 moving contact at the bottom =%.2f" %R2)

 at 5 degree
at 90 degree
to trigger at es=3.7V the R2 moving contact is at the top
To trigger at es =42.4 the R2 moving contact at the bottom =1369.10


## Example 20.3 Page No 906¶

In [17]:
import math

#initialisation of variables
R1=2.2*10**3
R2=1.5*10**3
R3=120.0
Vt=1.5

#Calculations
Vak1=Vt*((R1+R2+R3)/(R3+.5*R2))
Vak2=Vt*((R1+R2+R3)/R3)

#Results
print(" with R2 contact at center = %.2f" %Vak1)
print(" with R2 contact at zero = %.2f" %Vak2)

 with R2 contact at center = 6.59
with R2 contact at zero = 47.75


## Example 20.4, Page No 911¶

In [18]:
import math
#initialisation of variables
Vs=5.0
Ilmax=300*10**-3
Vl=7.0
Vg=0.8

#Calculations
Vz=Vl-Vg
print(" for D1, select a 1N753 with Vz=6.2")
Izmin=1*10**-3
R1=Vg/Izmin

#Results
print("The value of R1 is %d kohm " %R1)

 for D1, select a 1N753 with Vz=6.2
The value of R1 is 800 kohm


## Example 20.5 Page No 911¶

In [19]:
import math
#initialisation of variables
R1=25*10**3
R2=2.7*10**3
C1=3*10**-6
Vg=0.8
Vd1=8.0
Vs=115.0
f=60.0

#Calculations
Vc1=Vd1+Vg
#assume the average charging voltage is
Vac=1.414*Vs
E=.636*Vac
#average charging
Ic=E/(R1+R2)
#charging time
t=(C1*Vc1)/Ic
T=1/f
q=(t*360)/T
a=180-q

#Results
print("Conduction angle =%.2f degrees" %a)

Conduction angle =27.27 degrees


## Example 20.6 Page No 925¶

In [20]:
import math

#initialisation of variables
Vs=10.0
Vf=1.7
Is=500*10**-6
Ih=1.5*10**-3
E=30.0

#Calculations
R=27*10**3
C=0.5*10**-6
R1max=(E-Vs)/Is
R1min=(E-Vf)/Ih
t=C*R*math.log((E-Vf)/(E-Vs))

#Results
print("Capacitor charging time is %3.4f s" %t)

Capacitor charging time is 0.0047 s


## Example 20.7, Page No 931¶

In [21]:
import math
#initialisation of variables
Rbb=4.0*10**3
Pd25=360.0*10**-3
D=2.4*10**-3
T2=100.0

#Calculations
Pd=Pd25-D*(T2-25)
Vb1b1=math.sqrt(Rbb*Pd)

#Results
print("Maximum Vb1b1 that should be used at a temp 100 is %3.1fV " %Vb1b1)

Maximum Vb1b1 that should be used at a temp 100 is 26.8V


## Example 20.8 Page No 931¶

In [22]:
import math

#initialisation of variables
Vb1b1=25
nmax=0.86
nmin=0.74
Vd=0.7

#Calculations
Vpmax=Vd+(nmax*Vb1b1)
Vpmin=Vd+(nmin*Vb1b1)

#Results
print("Maximum Vpmax that should be is %3.1fV " %Vpmax)
print("Minimum Vpmin that should be is %3.1fV " %Vpmin)

Maximum Vpmax that should be is 22.2V
Minimum Vpmin that should be is 19.2V


## Example 20.9 Page No 933¶

In [23]:
import math
#initialisation of variables
Ip=.6*10**-6
Iv=2*10**-3
Veb1=2.5
Vpmin=19.2
Vpmax=22.2
Vbb=25.0
C=1*10**-6
R=18*10**3
Vp=20.0

#Calculations
Vpmin=(Vbb-Vpmax)/Ip
Remax=(Vbb-Veb1)/Iv
t=C*R*math.log((Vbb-Veb1)/(Vbb-Vp))
f=1.0/t

#Results
print("The value of f is %.2f  " %f)

The value of f is 36.94