Advanced Cooling Solutions for High-Frequency Medium-Voltage Planar Transformers

High-frequency medium-voltage (MV) planar transformers can increase the efficiency of the power supply chain by directly stepping down the medium voltage (10s of kV’s) of the grid to low voltages (~100s of V’s) required by end users, such as direct current fast charging of electric vehicles. As with many power electronics, thermal management of planar magnetic transformers for MV applications presents a barrier to pushing the boundaries of high-power density, while maintaining high efficiency and reliability. Thermal management for MV planar transformers is further complicated by the need to maintain sufficient voltage isolation between the transformer and the environment typically resulting in increased thermal resistance. Advanced Cooling Technologies, Inc. (ACT) designed and developed a novel dielectric two-phase heat transfer device that passively transports waste heat from the MV planar transformer to a heat sink. The form-factor of the device is ideal for the planar geometry of the transformer and allows the device to be in close proximity to the heat source. The dielectric nature of the device provides adequate voltage isolation between the transformer and the environment while providing a strong thermal link. During Phase I, ACT experimentally demonstrated the design, fabrication, and operation of a passive ceramic two-phase heat transfer device for planar transformers. The device provided 2-4x reduction in thermal resistance compared to the baseline ceramic material, and provided voltage isolation up to at least 30,000 volts. Simulations demonstrated the potential for a 2x increase in power density of planar transformers with improved thermal management. ACT, in collaboration with the University of Colorado Boulder, will develop a thermally enhanced medium-voltage planar transformer with significantly higher power density than state-of-the-art devices. The design and fabrication of the ceramic two-phase heat transfer device will be optimized and integrated into a functioning planar transformer. A theoretical full-scale thermal management system for an electric vehicle fast-charging station will be developed. Improved thermal management of planar transformers will push the boundaries of what is possible in terms of power density and efficiency. Thermally enhanced designs of MV planar transformers will be beneficial in the development of the nation’s electric vehicle fast charging infrastructure. Additionally, electric aircraft and spacecraft are increasingly using planar magnetic components due to their compact form and increased power density.