What is meaning of commutation of SCR?
Commutation
The process by which the
SCR is turned off from turn on condition is called as commutation.
Describe the different methods of commutation of the SCR.
Commutation of the SCR
Forced commutation : Class
A , Class B , Class C , Class D and Class E
Natural commutation : Class
F
Describe the main condition necessary to turn off the SCR.
The force commutation
circuit turn off time must be greater than the SCR turn off time.
Explain : Line commutation OR Explain : Natural commutation OR Explain
: AC commutation
Natural
( Line or AC ) commutation
The SCR is turned off
automatically during negative cycle of the alternating supply is called as natural
commutation. It is not possible when the SCR is operated on the DC supply.
Explain the term : Forced commutation
Forced commutation
When the SCR is operated
on the DC supply, it is not turned off naturally. The SCR is turned off by some
external circuit is called as forced commutation. This external circuit is
called as commutation circuit.
Explain the term : Current commutation, Voltage commutation
Current
commutation
It is a commutation
process in which the SCR is turned off from turn on condition by reducing the
anode current below the holding current for sufficient time.
Voltage
commutation
It is a commutation process in which the SCR is turned off from turn on condition by applying reverse voltage across SCR terminal for sufficient time. The voltage and current commutation is a type of forced commutation.
Which commutation method is known as self commutation?
Class A commutation and class B commutation
Which commutation method is known as resonant commutation? Why?
Resonant commutation
The Class A commutation
is known as resonant commutation because the commutation process in this method
is done by series RLC circuit.
Give reason : Class A and Class B commutation is known as
current commutation.
Current commutation
The commutation in the
class A and class B is done by reducing the anode current below the holding
current for sufficient time therefore it is called as current commutation.
Explain
the term : Self commutation
Self
commutation
The SCR turned off from
turned on condition after some time automatically and again it on after some
time. This process is called as the self commutation. However the time interval
between turn off and turn on depends upon circuit parameters.
Write the
application of class A commutation
Series inverter, Self
commutated inverter
Why the
class A commutation is used for high frequency applications?
Class A commutation
The weight of the
commutation component L and C becomes bulky particular for low frequency
therefore the class A commutation is used only for high frequency applications.
The resonance angular
frequency
ω0 = 1 / √ ( LC )
Which
commutation method is also known as complementary commutation?
Class C
Which
commutation method is also known as voltage commutation?
Class C
Write the
application of Class C commutation.
Mcmurray Bedford inverter
Why the Class
C commutation is called as complementary commutation?
Complementary commutation
An auxialiary thyristor
is connected across with the main thyristor in the Class C commutation. This
auxiliary thyristor turn off the main thyristor and vice versa therefore this
method is also called as complementary commutation.
Which
type of force commutation requires minimum energy?
External pulse commutation or Class E commutation
Thyristors are an integral part of modern day electrical circuits. They are mainly used as switches (automatic or manual) and voltage converters.
ReplyDeleteA thyristor is a high-speed semiconductor device that is stimulated by light, heat, or electric current to turn on and off easily.
It works as a sort of two-way switch. When it's turned on, it can be more easily turned off than when it is off. If a regular diode were in the circuit instead of a thyristor, the current would constantly flow in one direction through the circuit. It would have to be physically disconnected in order to turn it off which can be difficult to do under certain conditions (e.g., with live electricity).