An autotransformer for use in low frequency, high power applications that uses a stack of printed wire boards constructed of a top, inner, and bottom layer including electrical trace windings circumventing the transformer core and formed in the inner layer for direct thermal contact with a heat sink interface providing a uniform and consistent heat path down to the heat sink plate. The autotransformer further includes a board to board connection employing solder cups to electrically connect between predetermined printed wire board traces. The printed wire board autotransformer also may use a non-planar interface for thermal interface with a non-planar heat sink plate surface.