Kashimura, Y. and Negoro, Y., "Transmission-Mounted Power Control Unit with High Power Density for Two-Motor Hybrid System," SAE Technical Paper 2016-01-1223, 2016, doi:10.4271/2016-01-1223.
A second-generation power control unit (PCU) for a two-motor hybrid system is proposed. An optimally designed power module, which is a key component of the PCU, is applied to increase heat-resistant temperature, while the basic structure of the first generation is retained and the power semiconductor chip is directly cooled from the single side. In addition to the optimum design, by decreasing the power loss as well as increasing the heat-resistant temperature of the power semiconductors (IGBT: Insulated Gate Bipolar Transistor and FWD: Free Wheeling Diode), the proposed PCU has attained 25% higher power density and 23% smaller size compared to first-generation units, maintaining PCU efficiency (fuel economy). To achieve a high yield rate in the power module assembly process, a new screening technology is adopted at the initial stage of power module manufacturing. In the proposed technology, the maximum current required by hybrid systems can be applied to the component power semiconductor chips at high temperatures before power module assembly. The proposed PCU is directly mounted on the transmission case in the engine compartment of the vehicle and connected to the motor using three-phase connectors. Since conventional three-phase AC cables are eliminated in the layout, space saving and flexibility in the engine compartment layout are provided, simplifying the process of vehicle assembly.