Electric Vehicle Traction Motor with a Reluctance Outer Rotor and a Modular Stator with AC Concentrated Toroidal Windings and PM or DC Wave Winding Excitation

This paper proposes a novel electric motor concept using stator-embedded phase windings and can employ permanent magnet (PM) or Direct Current (DC) excitation. Concentrated toroidal coils are used for the phase windings and uniquely placed in separate slots while high flux intensification is achieved through a spoke-type arrangement of PMs or by using a DC excitation winding placed circumferentially around the stator. Torque production mechanism conforms with analytical concepts of air-gap flux density distributions using PM or DC excitation. High electrical loading can be achieved using DC excitation resulting in high power density as well as an extended power range through flux weakening by excitation current within thermal constraints. A comparison between this novel design and existing PM design previously analyzed and prototyped is carried out. Parametric studies as well as large scale multi-objective optimizations are used to find geometrical designs with best performance in terms of torque, total losses, torque ripple as well as power factor. Performance metrics such as power density, and machine goodness are used to compare this novel design with a ferrite design. The proposed novel design considers a 10′′ outer rotor diameter with a torque of 550Nm at a base speed of 3,000rpm.