THYRISTORS

Thyristors



Table of Contents

Introduction3

Basic Operation of Thyristor3

Characteristics of thyristors:4

Current-voltage characteristics of a thyristor5

Specifications6

Practical Example of Application Design7

Advantages and limitations7

Advantages8

Disadvantages8

Series and Parallel Connection8

Series Connection8

Parallel Connection8

Thyristor

Introduction

A thyristor is one of the most important types of power semiconductor devices. The thyristors are used extensively in the power electronic circuits. They operate as bi-stable switches, from a non conducting state to a conductive state. For many applications it can be assumed that the thyristor switches or switches are ideal, but practical thyristors exhibit certain features and limitations. The thyristor is an electronic component consisting of elements semiconductor that uses feedback to produce an internal switching. Materials which are made up of semiconductor type, i.e. depending on the temperature at which they are can function as insulating or conductive. These devices transmit only unidirectional because the current in one direction. It is generally used to control electrical power. The device consists of an anode and a cathode, where the joints are of a PNPN between them. Therefore can be modeled as 2 PNP and NPN transistors typical, so it is said also that the voltage fed thyristor works. This creates 3 connections, the gate terminal is connected to the junction J2 (NP junction). Some sources define as synonyms to the thyristor and silicon controlled rectifier (SCR), SCR others define as a type of thyristor, at the same devices DIAC and TRIAC. This element was developed by engineers at General Electric in the 1960's. Although much deeper roots of this device is found in the SCR created by William Shockley (Nobel Prize for Physics in 1956) in 1950, which was defended and developed at Bell Laboratories in 1956 (Harding, 1985, pp. 315).

Basic Operation of Thyristor

The thyristor is a bi-stable switch, i.e., is the electronic equivalent of the circuit mechanics, therefore, is capable of passing fully or completely block the flow of current without any intermediate level, while not able to withstand high power surges. This basic principle can also be seen in the Shockley diode. Thyristor design allows it to pass quickly on to receive a momentary pulse of current in its control terminal called gate (or in English, gate) when a positive voltage between anode and cathode, i.e. the voltage at the anode is greater than at the cathode. It can only be turned off with the interruption of power supply, opening the circuit, or by passing a reverse current through the device. If the thyristor reverse biases exist in a weak reverse leakage current until it reaches the point of maximum reverse voltage, provoking the destruction of the item (at the junction avalanche). For the device to pass the lock status to active status, you must generate a stream of positive engagement in the anode, and should be a small current in the gate can cause an avalanche breakdown at the junction J2 to make the device drive. For the device remains in the active state must be induced from the anode current of sustaining a much lower than the coupling, without which the device ...