A look inside the thyristor

Since the General Electric Co. of America produced the first thyristor in 1957, it has become widely used because of its advantages over its gaseous equivalent, the grid-controlled mercury-arc valve. The thyristor has the ability to control large power flows; thus there is a predominance of power engineers among the users of the device. Understandably, many consider the thyristor as a `blackbox¿ with the properties of a controllable switch. It is hoped that this article will introduce some of the complexities and subtleties of the thyristor, and perhaps stimulate interest in the machinations within the device.