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

Junction-to-fluid thermal resistivities, R ''(if), 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 ''(if)=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 Amps 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 Amps. A technique for automatic in situ degassing that would reduce manufacturing cost and permit field servicing of immersion systems that reach sub-ambient pressure when idle showed fluid loss rates of 0.3g per 100cc of air vented, roughly 1/100(th) that expected from an HFC-134a air conditioning system with a similar leak. Experiments to quantify packaging density and fluid requirements suggest that 100cc of fluid is required to dissipate 1kW and packaging density is limited only by the electrical bus geometry.