Thyristors
As stated before, Bell Laboratories were the first to fabricate a silicon-based semiconductor device called thyristor. Its first prototype was introduced by GEC (USA) in 1957. This company did a great deal of pioneering work about the utility of thyristors in industrial applications. Later on, many other devices having characteristics similar to that of a thyristor were developed. These semiconductor devices, with their characteristics identical with that of a thyristor, are triac, diac, silicon-controlled switch, programmable unijunction transistor (PUT), GTO, RCT etc. This whole family of semiconductor devices is given the name thyristor. Thus the term thyristor denotes a family of semiconductor devices used for power control in dc and ac systems. One oldest member of this thyristor family, called silicon-controlled rectifier (SCR), is the most widely used device. At present, the use of SCR is so vast that over the years, the word thyristor has become synonymous with SCR. It appears that the term thyristor is now becoming more common than the actual term SCR. In this book, the term SCR and thyristor will be used at random for the same device SCR. Other members of thyristor family are also discussed in this category.
A thyristor has characteristics similar to a thyratron tube. But from the construction view point, a thyristor (a pnpn device) belongs to transistor (pnp or npn device) family. The name ‘thyristor’, is derived by a combination of the capital letters from THYRatron and transISTOR. This means that thyristor is a solid state device like a transistor and has characteristics similar to that of a thyratron tube. The present-day reader may not be familiar with thyratron tube as this is not being taught these days.
Written by arjun on April 8th, 2009 with
1 comment.
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#1. June 17th, 2009, at 12:18 AM.
thanks. i m very happy that i have got all the circuit diagrams which i was in need.