Systems and methods that allow for weight and size reduction of electronics components, such as transformer rectifier units (TRUs) or autotransformer rectifier units (ATRUs), by providing a fluid cooling system is utilized to provide high heat dissipation for a transformer assembly of TRUs or ATRUs by providing a thermal interface at the windings of the transformer assembly, which are the hottest spots in such assemblies. The cooling system may include a fluid-cooled winding heat sink element or “finger,” which may be a thermally conductive bar (e.g., aluminum, copper) having microchannels therein positioned between the core and windings of a transformer or between turns of the windings of a transformer. Fluid passes through the microchannels of the heat sink element to provide direct cooling to the heat generating windings of the transformers. The heat sink element may be produced by an additive manufacturing technology.