Direct-water-cooled next High Power Density Dual (nHPD2) considering inverter layout

Three types of cooling methods were compared for Hitachi's latest low inductive housing 2in1 module called "next High Power Density Dual (nHPD2)" considering inverter layout. The first is an air-cooled type, the second is a conventional water-cooled type (called 'indirect-watercooled' type), and the third is a water-cooled type without using thermal grease (called 'direct- water-cooled' type). The trade-off curve between thermal resistance and pressure drop was smallest when the direct-water-cooled nHPD2 was used. The thermal resistance of direct- water-cooled type was half which resulted in electric current output doubling comparing to indirect-water-cooled type.