Thyristors,SCR,Diac,Triac,UJT theory

[walters]

What are Thyristors,SCR,Diac,Triac,UJT used for?

How do i use a Thyristor?
How do i use a SCR?
How do i use a Diac?
How do i use a Triac?
How do i use a UJT?


What type or circuits use them ?

What kind of Applications can i use these components for?


I don't use these components much because i don't know how to use them or what they do can u guys please help me out with these components

 

[DigiTan]

I'm not certain about the the others, but SCRs and Triacs both fall under the Thyristor category. The SCR (Silicon-Controlled Rectifier) is a 3-terminal device that is effectivly a diode that won't conduct a forward current until a current enters the gate terminal. After that, the SCR continues to conduct even after the gate current has been removed. It's not to be confused with a transistor because it only operates on an on/off basis. This is to say it can't truely amplify.

A triac is essentially two SCRs paralleled with on another, except they're back-to-back so that it can conduct current in either direction once the gate current arrives.

Looking at The First Google Result for "Thyristor" that came up, I found a more detailed description of them. If anyone can describe them in a little more detail, I'm interested because SCRs and Triacs aren't really discussed a lot in the EE courses.

 

[walters]

Thanks for the help

most of theses components have a GATE or Trigger input

Whats the difference between the Gate VS the trigger?


These components won't conduct unless a voltage or pulse is at the Gate or trigger input mostly

 

[akg]

Thanks for the help

most of theses components have a GATE or Trigger input

Whats the difference between the Gate VS the trigger?


These components won't conduct unless a voltage or pulse is at the Gate or trigger input mostly

A trigger is a signal (imagine it as a binary gate, either open or off), when given turns on the device,and the device will not turn off until some other condition(depends on the device) occurs.Once triggered . the subsequent trigger has no control over the current . read the working of the device for more details

A gate on the otherhand can control the current flow thru the device.

 

[walters]

How do i shut the component OFF after its triggered?

 

[akg]

How do i shut the component OFF after its triggered?

make the current flowing thru the device below 'holding current'

 

[walters]

Thanks for the help

make the current flowing thru the device below 'holding current'

How is this done?

How do i make the device "holding current" ? how is this done?

 

[akg]

Thanks for the help

make the current flowing thru the device below 'holding current'

How is this done?

How do i make the device "holding current" ? how is this done?

holding current is the min current to keep the device conducting
look at
https://www.americanmicrosemi.com/tutorials/scr.htm
**broken link removed** -> study the device graphs
also have a look at the parameters of an scr
eg:- https://www.alldatasheet.com/datasheet-pdf/pdf/109289/NEC/03P6MG.html

 

[Styx]

Dear GOD, Walters getting into Power electronics!!!!
My nightmear has come true

 

[walters]

styx

I don't understand about diac and triac

The diac can "Conduct current" in either direction its bidirectional

The Triac has a GATE

What are they both used for i don't get they are used for

 

[akg]

styx

I don't understand about diac and triac

The diac can "Conduct current" in either direction its bidirectional

The Triac has a GATE

What are they both used for i don't get they are used for

walters,
what is the purpose of the gate in triac ?

 

[walters]

The Gate- is to control the current throught the component

 

[akg]

The Gate- is to control the current throught the component

The Triac and FET/UJT both has gates. does they function similar ?
what is described as the breakover voltage of a diac?

 

[walters]

The Triac and FET/UJT both has gates. does they function similar ?

The GATE resistance is different i think so the current controlled is different

what is described as the breakover voltage of a diac?

when reverse voltage before the diac breaks down

 

[akg]

The GATE resistance is different i think so the current controlled is different

Ans incomplete/wrong . The question was not what "u think".

when reverse voltage before the diac breaks down

Are u shure it is the "reverse" voltage reqd to breakdown,if yes what is the difference b/w diac and zener ?.Does a diac has forward breakdown voltage?
Why does a diac have no trigger to conduct ?

 

[walters]

The Triac and FET/UJT both has gates. does they function similar ?

Sorry i don't know

when reverse voltage before the diac breaks down

Are u shure it is the "reverse" voltage reqd to breakdown,if yes what is the difference b/w diac and zener ?.

The voltage drop before it breaksdown i guess

Does a diac has forward breakdown voltage? yes it does

Why does a diac have no trigger to conduct ? because its bi directional
but i don't know why
or whats its used for

 

[akg]

T
Why does a diac have no trigger to conduct ? because its bi directional
but i don't know why
or whats its used for

TRIAC is also bidirectional , but has trigger , so what is the difference.?

 

[walters]

The Triac controls the "Conducting" of the current the Diac can not

 

[akg]

The Triac controls the "Conducting" of the current the Diac can not

so u got clues to the difference b/w diac and triac

 

[walters]

sorta of i mean what do they do different than regular components?

Do they do something different to the current/phase/voltage?

I'm not sure what they do really ?