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

Recently, the power density of power converters has increased to minimize their size and weight. However, this increase 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 as an effective solution for cooling data center servers. This study 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 maximize superior cooling and dielectric strength of HFE, achieving a power density of 245 kVA/L. The cooling performance of the system was verified via 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, which was also well below the rated value of the switching devices.