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In industrial applications, two forms of electrical energy are used: direct current (dc) and alternating current (ac). Usually constant voltage constant frequency single-phase or three-phase ac is readily available. However, for different applications, different forms, magnitudes and/or frequencies are required. There are four different conversions between dc and ac power sources. These conversions are done by circuits called power converters. The converters are classified as:
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.
The following sections will describe the operation principles of the cycloconverter starting from the simplest one, single-phase to single-phase (1f-1f) cycloconverter.
1.1. Single-phase to Single-phase (1f-1f) Cycloconverter
To understand the operation principles of cycloconverters, the single-phase to single-phase cycloconverter (Fig. 2) should be studied first. This converter consists of back-to-back connection of two full-wave rectifier circuits. Fig 3 shows the operating waveforms for this converter with a resistive load.