The document presents an overview of silicon-controlled rectifiers (SCRs), detailing their introduction, characteristics, types, applications, advantages, and disadvantages. SCRs are bistable semiconductor devices used for power control and switching, with specific applications in high-frequency inverters and DC circuit protection. While offering benefits like high current switching and compact size, SCRs have limitations such as difficulty in turning off and conversion of AC to DC.

1. SILICON
COTROLLED RECTIFIRE
Presented By – Om I. Barewar

2. Containts
 Introduction.
 Symbols and Terminology.
 SCR Characterestics.
 Types of SCR.
 SCR characterestics.
 Application of SCR.
 Advantages and Disadvantages.
 Result and Conclusion.
 References.

3. Introduction
 The name of Thyristor is derived from the Greek word
"hqnra" meaning "a door".
 A Thyristor is a bistable semiconductor device.
 It comprises three or more junctions and can be
switched from the off state to the on state or vice versa.
 Switchingfrom the off state to the on state is normally
initiated by a control signal.
 Switch off is normally caused by the current though
the Thyristor dropping below a critical level.
 In the 1960s, bidirectional Thyristors, called Triacs,
where introduced.

4. Symbols

5. Types of SCR
DIAC TRIAC SBS

6. SCR Characterestics
 In addition to their traditional role of power
control devices, SCRs are being used in a wide
variety of other applications in which the SCR’s
turn−off characteristics are important.
 example — reliable high frequency inverters
and converter designs (20 kHz) require a known
and controlled circuit−commutated turn−off time
(tq).
 Unfortunately, it is usually difficult to find the
turn−off time of a particular SCR for a given set

7. VI Characterestics

8. SCR

9. Applications of SCR
 It is uses for power control.
 It is uses for switching.
 For DC circuit breaker.
 Over voltage protection.
 Pulse circuits.
 Battery charging regulator.
 Zero voltage switching.
 AC power control with Solid relays.
 TRIAC zero point switch application.

10. Advantages
 It switches large levels of current using only a
small control current.
 It can switch high voltages.
 Able to control AC power.
 Much smaller in size compare to a transformer
(control AC device).
 Simple to control.
 Turn ON gain is very high.
 Low cost.

11. Disadvantage
 It Cannot be easily turned off.
 For this reason, not suitable for high-power DC
circuits.
 Though suitable for high-power AC circuits, ironically
it will convert the AC to DC. (Though sometimes this
is wanted.)
 In an AC circuit, needs to be turned on each cycle.

12. Result and Conclusion
 Hence the SCR is best for switching.
 Above characteristics make thyristors extremely
usefulin control applications.
 Compared to a mechanical switch,a thyristor
has a very long service life and very fast turn on
and turn off times.
 These devices will act as a crowbar when
overvoltage occurs and will divert the energy
away from circuit or device that is being
protected.

13. References
 Handbook Thyristor theory.
 Handbook of Thyristors - Theory, Parameters
and Applications written by Jurek Budek.
 Littlefuse site
 http://www.circuitstoday.com
 https://www.scribd.com
 http://onsemi.com

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