Multiparallel Asymmetrical Cycloconverter Having Improved Power Factor and Waveforms

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Abstract
A newly developed cycloconverter having an improved power factor is presented. The cycloconverter is composed of three or six converters connected in parallel through interphase reactors. To reduce reactive power, the thyristors in the bridge are controlled so as to have the minimum number of phase-controlled thyristors, and the other thyristors are kept in the turn-on or -off states. To compensate for the unbalanced input current of the bridge, the input terminals of three or six bridges are parallel connected and twisted to each other. Owing to the multiparallel configuration, the cycloconverter fits for relatively low voltage and high current ratings. The method enables the realization of almost the same power factor and harmonic content as the conventional high-performance cycloconverters. Both the experimental and simulation results show that a power factor of above 0.8 is obtained in 70 percent of its operating area at a load power factor of 0.8. The microcomputer-based gate control circuit is described and results with the conventional cycloconverters are compared.