Thyristors revisited. The role of improved performance and design in modern applications

More than 35 years ago the SCR/thyristor became the first semiconductor capable of controlling substantial levels of voltage and current and has since taken over many applications previously done by electro-mechanical and ignitron type devices. In the same period other power semiconductors have come along, e.g. high power bipolar transistors, darlingtons, MOSFETs, IGBTs and GTOs which in their turn have taken over some of the applications formally done by thyristors. Yet the thyristor has remained the first choice where proven reliability, high current, high voltage and not least, cost effectiveness are the main considerations. This paper shows how modern market applications have driven the way which device development has gone and the way in which device performance is measured. Emphasis is placed on low frequency, converter or phase control thyristors.