Properties and applications of GTO thyristors

Abstract

The Gate turn-off thyristor has only recently, namely during the last six years or so become competitive with other power devices, on the market. The reason for the intensive research that has taken place as regards to its development is the simple control acquired through switching both ON and OFF simply by applying positive or negative gate current. The position of the GTO is yet uncertain, as even today it is still in the stage of development, and the ideal device has not yet been constructed. The GTO today, however, seems to be a fitting candidate for the replacement of the conventional thyristor especially if the selling price of the GTO was reduced. This project deals with an analysis of the gate turn-off thyristor in terms of its structure, its properties and its applications. The similarities and differences, with resultant advantages or disadvantages over the conventio~al thyristors are discussed. And the application of the GTO thyristor with special reference to d.c choppers ·and de - ac inverters, is analysed. The GTO type BTV 58 - 1000 R was tested in the laboratory with special regards to drive circuitry and snubber circuits. For comparison reasons, a de chopper was built using both conventional thyristors and the GTO thyristor. Thus a full realization of the differences existing between the two devices was developed. The GTO thyristor was finally used in a simplified PWM single phase d.c.- a.c. inverter, to help understand better the practical problems that are normally associated with GTO' s in bridge circuits.