Abstract: Power electronics for electric traction motors used to drive automotive vehicles are cooled in a closed system by spraying a dielectric liquid coolant directly onto inverter circuitry. The liquid coolant changes phase and vaporizes as it absorbs heat from power transistors in inverter circuitry comprising the power electronics. The resultant vapor is condensed back to a liquid in a heat exchange arrangement having pipes carrying a second coolant from a radiator used to cool an engine or fuel cell stack in the automotive vehicle. Overspray coolant, which remains liquid, can also be cooled by the heat exchange arrangement. By utilizing the latent heat of evaporation of the dielectric coolant and increasing the rate recycling of the coolant as power output increases, temperature increases in the power electronics are controlled.

Abstract: In order to provide a modular arrangement, an inverter for an electric traction motor used to drive an automotive vehicle is positioned in proximity with the traction motor. The inverter is located within a compartment adjacent to one end of the electric traction motor and is cooled in a closed system by spraying a liquid coolant directly onto the inverter. The liquid coolant absorbs heat from the inverter and is cooled by a heat exchange arrangement comprising a reservoir with pipes carrying a second coolant from the radiator of the automotive vehicle. In a preferred embodiment, the coolant is collected from the inverter in an annular reservoir that is integral with the compartment containing the inverter. In accordance with one embodiment of the cooling arrangement, heat from the inverter vaporizes the liquid coolant by absorbing heat from the inverter during a phase change from a liquid to a vapor.