ABSTRACT
Cycloconverters are direct-one stage-frequency changers [1,2]. In general, they provide an output frequency lower than the input frequency being called restricted frequency changers. In special schemes [2] they may also provide unrestricted output frequency. In the following we refer to restricted frequency cycloconverters. Among the numerous existing possibilities [2] a six-pulse cycloconverter without circulating current, capable of operating in four quadrants is presented in Fig. 9.1. At least 36 thyristors and a power transformer with three three-phase secondary windings are required. This is one of the reasons why cycloconverters are used mostly in the high power range where paralleling of thyristors if required.
