Design and analysis of a highly integrated 9-phase drivetrain for EV applications

Cost and compactness are major success factors for electrical drivetrains for (hybrid) electric vehicles (EV). To increase the system power density, the focus is set on system integration, meaning to integrate e-machine, inverter, control, and gearing into one common housing. The inverter integration is facilitated by multiphase motors leading to lower phase powers and thus smaller inverter modules. To overcome price uncertainties of rare earth magnets, improved hard ferrite magnets are chosen as an alternative. In this paper, a new highly integrated drivetrain with a ferrite based 9-phase synchronous motor concept is presented with special focus on the main choices leading to the particular electromagnetic and mechanical design. The advantages of an integrated triplex inverter power supply and the new mechanical arrangement of a spoke-type rotor design will be presented, without focusing on the detailed electromagnetic behavior of the machine.