Practical Considerations Relating to Immersion Cooling of Power Electronics in Traction Systems

Junction-to-fluid thermal resistivities R ''(jf), of two dual-side-soldered insulated gate bipolar transistor (IGBT) modules immersion cooled in a hydrofluoroether C(3)F(7)OCH(3) liquid were measured experimentally. R ''(jf) = 0.040 degrees C.cm(2)/W for 0.144 cm(2) die at a peak heat flux of 1180 W/cm(2) and 55 A, and 0.11 degrees C.cm(2)/W for 1.46 cm(2) die at a peak heat flux of 550 W/cm(2) and 305 A. A technique for automatic in situ degassing that would reduce manufacturing cost and permit field servicing of immersion systems that reach subambient pressure when idle showed fluid loss rates of 0.3 g per 100 cm(3) of air vented, roughly 1/100th that expected from an HFC-134a air conditioning system with a similar leak. Experiments to quantify packaging density and fluid requirements suggest that 100 cm(3) of fluid is required to dissipate 1 kW and packaging density is limited only by the electrical bus geometry.