ABSTRACT
This chapter examines the operation of thyristors with a direct current (DC) source voltage. More complex commutation circuits may be required when the thyristors are connected to form part of a bridge circuit. The function of a forced commutation circuit is first to reduce the current through the conducting thyristor to zero and then to maintain a reverse voltage across this thyristor for a period equal to or greater than the thyristor turn-off time in order to re-establish the blocking state. The chapter provides forced commutation and to consider the operation of various forced-commutation circuits. It presents the operation of a DC chopper. The chapter addresses DC choppers in terms of their operating envelopes. It also examines the operation of voltage- and current-sourced converters as a means of producing a variable-frequency supply. The chapter explains means of controlling a variable frequency inverter output voltage. It deals with pulse-width-modulated inverters. The chapter highlights the uses of cycloconverter.
