Design of a High-Speed, High-Power Density Permanent Magnet Synchronous Motor for Electric Vehicle Traction

A high-speed electric motor is developed as part of a high-density traction system that includes the motor and the power electronics stage. To consider the close interdependence of the inverter and the motor sizing for a specific application, the high-level design of the high-density system and the detailed design of the electric motor are presented in this thesis. The main objective of the research work is to improve the state-of-the art power density of a traction system for a passenger car. At the system level, different electronic topologies are discussed, and different types of permanent magnets motor topologies are presented and compared regarding the objective of power density. A modeling methodology is presented as an accurate and flexible tool to evaluate the electromagnetic performances of different PMSM topologies. One development axis to increase the power density is an enhanced cooling design of the motor heat extraction system. The proposed motor cooling design allows a distributed heat extraction, with a focus on the typically limiting hot spots on the end windings and the rotor magnets. A second development axis to consider for the motor power density is to increase its speed. A PMSM rotor topology with a retaining sleeve is selected as the high-speed rotor design. The geometric variables that impact the electromagnetic performance and losses are evaluated with some considerations on the demagnetization vulnerability. The thermal management of the losses is discussed. A comparison of the copper losses for different wire types and slot shapes is presented, with a focus on the high frequency losses. A stator slot configuration is proposed as a good compromise between high frequency losses reduction, DC copper resistance, heat transfer, performance, and cost. A high-density system design is presented, combining the different motor enhancements proposed in the research work. From the system geometry and simulated output power, a power density exceeding the targeted value is achieved. The performances are compared with those of a recent design from the industry. Over the full speed range, both peak and continuous power density are higher for the proposed high-density system