1-rectifiers: from single-phase or three-phase ac to variable voltage dc
2-choppers: from dc to variable voltage dc
3-inverters: from dc to variable magnitude and variable frequency, single-phase or threephase ac
4-cycloconverters: from single-phase or three-phase ac to variable magnitude and variable frequency, single-phase or three-phase ac
The first three classes are explained in other articles. This article explains what cycloconverters are, their types, how they operate and their applications.
Traditionally, ac-ac conversion using semiconductor switches is done in two different ways: 1- in two stages (ac-dc and then dc-ac) as in dc link converters or 2- in one stage (ac-ac) cycloconverters (Fig. 1). Cycloconverters are used in high power applications driving induction and synchronous motors. They are usually phase-controlled and they traditionally use thyristors due to their ease of phase commutation.