An isolated, power factor corrected, converter, for operation from a three-phase AC source, comprises three power processors, each power processor connected to one of the three phases. Each power processor comprises a cascade of a first and a second power conversion stage. At least one of the first and second power converters in each power processor is configured to provide galvanic isolation through a DC Transformer between the power processor input and output. At least one of the first and second power converters in each power processor is configured to provide power factor correction at the AC source. Substantially all of the bulk energy storage and low frequency filtering is provided by storage elements at the output of the power system. Low voltage semiconductor devices may be cascaded to implement low output capacitance high voltage switches in a multi-cell resonant converter for high voltage applications.