High Energy Density, Low-Cost, High Temperature Capacitors for Hybrid Vehicles

Currently, no low-cost capacitors provide an elevated temperature, high reliability solution to the DC Bus Inverter need in hybrid electric vehicles. In previous work, an annular film capacitor design, which showed potential for use in the DC Bus application, was developed. The unique shape of the capacitor enables the potential use of polypropylene film at 105°C, a requirement for this application. However, the characteristics of the device in this application over transportation lifetimes need to be understood, and the overall design must be optimized. In Phase I, the characteristics of all of the materials that make up the capacitor were profiled as a function of temperature and fed into a sophisticated modeling program. The results, which were compared with actual tests of an annular film capacitor, confirmed the reliable 105°C operation of the device as a DC Bus Capacitor. In Phase II, the final material selections will be optimized for reliability, a low cost but reliable interconnect scheme will be developed, and a test package (which will allow power-train transportation designers to confidently specify the device) will be produced. In addition, modeling simulations to predict failure modes and lifetimes will be compared with actual test results of manufactured capacitors. Commercial Applications and Other Benefits as described by the awardee: A low-cost, polypropylene film used as a DC Bus Capacitor, which requires nothing more than available 105°C engine coolant, would enable the potential elimination of a separate coolant loop and reduce the cost and weight of hybrid electric vehicles.