Advanced Electric Powertrain Cooling Contributing to Powertrain Efficiency

Within the H2020 ModulED project, a highly integrated electric powertrain is developed. One of the main challenges was the development of a performant and simultaneously efficient cooling system. This was due to the compactness of the module and the dense packaging of subsystems such as motor, inverter and transmission. While keeping flow and pressure drop within limits to reduce required auxiliary power, the cooling system must be capable of dissipating the generated heat at maximum powertrain power and under most extreme ambient temperatures.Development experience from prior projects provided an initial layout concept of the coolant routing within the drivetrain module. The concept was further developed and adapted to the available space in the ModulED integrated powertrain. Threedimensional conjugate heat transfer (3D-CHT) simulations were applied to investigate the effect of various influencing parameters on the system's hydraulic and thermal performance. The cooling system's performance was improved considering several limiting factors within the design space.The objectives were reached by hydraulically connecting inverter and motor cooling in series. The option of a parallel connection was also considered and will be assessed in the hardware prototype. At maximum powertrain power, the required coolant flow rate and the resulting pressure drop remain within the predefined limits, increasing overall module efficiency. At lower power levels with lower cooling demand, the flow rate will be adjusted accordingly. This paper covers several aspects of the inverter and motor cooling that were investigated in the project as well as the final performance of the cooling subsystem. A design approach of a highly efficient and performant cooling system for electric vehicle drivetrain modules is presented, which also considers restrictions such as integration space and costs