High-Power Density Three-Phase Inverter with 3D Circuit Structure Using Liquid Immersion Cooling

The power density of power converters has recently increased to minimize their size and weight. However, this rise in power density also leads to higher heat generation density and maximum temperature of converters. Therefore, conventional cooling methods such as air cooling and indirect water cooling may not be sufficient to cool high-power density power converters. Liquid immersion cooling has been considered an effective solution for cooling data center servers. This paper aimed to design a high-power density three-phase inverter using a liquid immersion cooling system. The cooling system used hydrofluoroether (HFE) as a refrigerant. The inverter was designed with a 3D circuit structure to take advantage of HFE's, superior cooling and electrical insulation performance, achieving a power density of 346 kVA/L. The cooling performance of the system was verified through computational fluid dynamics (CFD) thermal analysis. The simulation results indicated that the maximum temperature reached 65.4°C, which is well below the rated value of the switching devices. Furthermore, in experimental heat generation tests with actual equipment, the maximum temperature reached 46.2°C, also well below the rated value of the switching devices.