POLYGON AUTOTRANSFORMER BASED TWENTY-FOUR- PULSE AC-DC CONVERTER

摘要

The invention provides a hexagon-connected autotransformer for converting three-phase ac input voltages to twelve phase shifted ac voltages feeding four identical six-pulse converters. The six phase shifted voltages are at an angle of +7.5 degree or -7.5 degree with respect to the supply voltages six phase shifted voltages are at an angle of +22.5 degree or -22.5 degree with respect to the supply voltages and their magnitudes are essentially identical. Twelve output nodes are provided between adjacent winding pairs, and the windings sized and arranged such that the output voltage magnitudes are essentially identical. The present design requires substantially fewer coils than other autotransformers for 24-pulse AC-DC converters, resulting in saving in space, volume, weight, size and cost of the converter. The magnetics requirement is only about 27% of the drive rating. The output voltage ratio can also be selected to give an average dc output from the proposed converter same as that of a conventional three-phase diode bridge rectifier. However, it is also possible to step up or step down the output voltage as required. IN-DEL-2006-02728A