Improvement of cycloconverter power factor via unsymmetric triggering method

Abstract

Since the cycloconverter is naturally commutated, it is possible to manufacture a unit of capacity as large as the rectifier. In fact, a cycloconverter of capacity exceeding 100 MVA may be used to drive linear motors for high-speed railway use. Such a large-capacity converter could not be realized by the conventional inverter. It is reported that the price of the cycloconverter is about half that of inverters if the capacity is larger than 10 MVA. This paper proposes a gate control scheme to maximize the input power factor without increasing harmonic contents of input and output currents. Its features can be summarized as follows. (1) The fundamental input power factor is 1.2 to 2 times as high as that of the conventional cycloconverter. (2) The fundamental input power factor is higher than the power factor of the load when the latter is low. (3) Input and output waveforms are better than those of the conventional cycloconverter.