# Chapter 17 , Thyristors¶

## Example 17.1 , Page Number 379¶

In [1]:
import math

#Variables

I = 40                      #Current (in milli-Ampere)
t = 15 * 10**-3             #time (in seconds)
CFS = 93                    #Circuit fusing rate (in Ampere-square second)

#Calculation

SCR = I**2 * t              #Surge in the device (in Ampere-square second)

#Result

print "Since value of SCR i.e. ",SCR," A**2s is less than CFS i.e. ",CFS," A**2s."
print "Therefore the device will not be destroyed."

Since value of SCR i.e.  24.0  A**2s is less than CFS i.e.  93  A**2s.
Therefore the device will not be destroyed.


## Example 17.2 , Page Number 379¶

In [2]:
import math

#Variables

SCR = I2t = 75.0            #SCR (in Ampere-square second)
IS = 100.0                  #Current (in Ampere)

#Calculation

tmax = I2t / IS**2          #Maximum allowable time (in seconds)

#Result

print "Maximum allowable time is ",tmax * 10**3," ms."

Maximum allowable time is  7.5  ms.


## Example 17.3 , Page Number 385¶

In [3]:
import math

#Variables

VD = 0.7                     #Voltage (in volts)
n = 0.75                     #Intrinsic stand-off ratio
VBB = 12                     #Base Voltage (in volts)

#Calculation

VP = n * VBB + VD            #Peak-point voltage (in volts)

#Result

print "Peak - point voltage of the circuit is ",VP," V."

Peak - point voltage of the circuit is  9.7  V.


## Example 17.4 , Page Number 385¶

In [4]:
import math

#Variables

rB1 = 4.0                    #Resistance (in kilo-ohm)
rB2 = 2.5                    #Resistance (in kilo-ohm)
VBB = 15.0                   #Base voltage (in volts)
VD = 0.7                     #Voltage (in volts)

#Calculation

n = rB1 / (rB1 + rB2)        #Intrinsic stand-off ratio
VP = n * VBB + VD            #Peak-point voltage (in volts)

#Result

print "Intrinsic stand off ratio is ",round(n,4),".\nPeak-point voltage is ",round(VP), "V."

Intrinsic stand off ratio is  0.6154 .
Peak-point voltage is  10.0 V.


## Example 17.5 , Page Number 385¶

In [5]:
import math

#Variables

n = 0.60                     #Intrinsic stand-off ratio
rBB = 7.0                    #Base- Bulk resistance (in kilo-ohm)

#Calculation

rB1 = n * rBB                #Resistance (in ohm)
rB2 = rBB - rB1              #Resistance (in ohm)

#Result

print "Static values of rB1 is ",rB1," kilo-ohm and of rB2 is ",rB2," kilo-ohm."

Static values of rB1 is  4.2  kilo-ohm and of rB2 is  2.8  kilo-ohm.