What is Thyristor: Definition and 15 Discussions

A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials. It acts exclusively as a bistable switch, conducting when the gate receives a current trigger, and continuing to conduct until the voltage across the device is reversed biased, or until the voltage is removed (by some other means). There are two designs, differing in what triggers the conducting state. In a three-lead thyristor, a small current on its Gate lead controls the larger current of the Anode to Cathode path. In a two-lead thyristor, conduction begins when the potential difference between the Anode and Cathode themselves is sufficiently large (breakdown voltage).
Some sources define silicon-controlled rectifier (SCR) and thyristor as synonymous. Other sources define thyristors as more complex devices that incorporate at least four layers of alternating N-type and P-type substrate.
The first thyristor devices were released commercially in 1956. Because thyristors can control a relatively large amount of power and voltage with a small device, they find wide application in control of electric power, ranging from light dimmers and electric motor speed control to high-voltage direct-current power transmission. Thyristors may be used in power-switching circuits, relay-replacement circuits, inverter circuits, oscillator circuits, level-detector circuits, chopper circuits, light-dimming circuits, low-cost timer circuits, logic circuits, speed-control circuits, phase-control circuits, etc. Originally, thyristors relied only on current reversal to turn them off, making them difficult to apply for direct current; newer device types can be turned on and off through the control gate signal. The latter is known as a gate turn-off thyristor, or GTO thyristor. A thyristor is not a proportional device like a transistor. In other words, a thyristor can only be fully on or off, while a transistor can lie in between on and off states. This makes a thyristor unsuitable as an analog amplifier, but useful as a switch.

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  1. F

    Thyristor gate driver problem

    Hey folks. please help me out, I am having trouble finding the problem with a thyristor driver circuit. So this circuit has been working for many years without problems. It works from 2 of the 3 phases, so 400VAC (I am in Europe). The thyristor is in series with a large coil, aka electromagnet...
  2. B

    Why does a thyristor keep conducting after removing the gate current?

    i have seen several videos of thyristors but they never really explain the fundamentals they just say that cause there is a current flowing in there it keeps being on but why does a transistor then turn off when you remove gate voltage
  3. Javier Lopez

    High Power SCR Driver Design for Plasma Compression Coil Activation

    I have made following design to drive two high power hokeypuck SCRs to activate a Plasma compression coil. As long as catode falls below 0V, I do not know if it is needed to insert diodes from the optoisolated driver A1 (and A2) and the limiting current resistor R1 (and R2):
  4. A

    Thyristor: Definition & Working Principles

    What is a thyristor and how do they work?
  5. cnh1995

    Inverter for 3-phase fully controlled Thyristor converter

    I am helping a group of my friends for writing microcontroller code for their final year project in EE. They are building a small model of HVDC system (fed from 3 phase supply), with microcontroller based converter and inverter. We are done with the coding for firing of the SCRs in the...
  6. H

    Increase the maximum voltage rating of semiconducter

    Hello, I was wondering if there is any way of increasing a transistor or thyristor maximum voltage ratting in DC? Thanks. Edit: Just to be more precise, I am referring to the off state. I know you can the on state via a resistor.
  7. T

    What thyristor, triac, diode, transistor for an amateur?

    Beginner here. Learning about electronics. I would like to play with a thyristor, triac, diode, transistor, diode bridge, etc. using 1,5-9V batteries, wires, multimeter. I am buying a breadboard too. What kind of these you recommend for that purpose? There is a wide variety on the shelves please...
  8. M

    HVDC - Current Source Converter - Minimum DC Power flow

    Hello, I was reading about the differences between Current Source Converters and Voltage source converters. One main difference was that Current source converters need to have a minimum DC power flow of 5-10% while VSC do not have a min flow requirement. It was also called a deadband. Why is...
  9. Planobilly

    How to test a Bi-Directional Triode Thyristor

    Hi Guys, I am working on a Carver model M-1.0t stereo amp. There is no AC voltage to the input transformer primary. The AC input is controlled by a Bi-Directional Triode Thyristor. This is the data sheet. http://www.datasheet.hk/view_online.php?id=1927120&file=0465\sm16gz41_6629879.pdf This is...
  10. U

    How to quantify relatively simple experimental errors

    Homework Statement For my coursework task, i am to quantify and discuss errors associated with an experimental procedure. This involved a thyristor control unit which allowed the firing angle of two thyristors (in a half controlled bridge rectifier) to be varied with a rotary dial or pot/rheo...
  11. P

    Help with thyristor currents please

    Hi, I want to use a 2n5062 thyristor as a switch to output a current when the thyristor is on. I have found a data sheet which has values for gate trigger current and holding current (200 microamp and 5 milliamperes) respectively. Am I correct in thinking I must apply at least the gate trigger...
  12. R

    What is causing the fault in my thyristor and op amp circuit?

    I have tested this circuit on the computer and it works but when I try to make it both on a pcb and breadboard the circuit will not work at all. If i swap the thyristor - TIC106D - for a transistor - TIP121 - the circuit works fine so I think the problem can be isolated down to somewhere between...
  13. G

    Thyristor soft-starter in Matlab

    Can anybody help me with this, please. I am supposed to design a soft starter to reduce inrush current from grid to the 3 phase induction machine. My understanding is that initially the high inrush current is blocked by thyristor and after a period of time the normal current is allowed to...
  14. R

    Are Mega Testers Accurate for Testing Puck Thyristors?

    I just started working on a furnace that uses the puck type thyristors for the main power switching. Every now and then, one of them blows and we replace it. We ususally use a mega tester to test wheteher they have blown or not i.e. put 250V across and short the gate to the anode. A zero...
  15. M

    What Is the Practical Device Number of a Static Induction Thyristor?

    hello everybody! i am making a report on Static induction thyristor and about to end the report but i could't find the practical device number of the SITH so if anybody knows about this, kindly tell me?