Design and Comparative Analysis of Electric Motors with “Flux-Switching” Effect Having Reluctance Rotors and PM or DC Stator Excitation

This paper introduces innovative designs for synchronous electric motors with phase coils and permanent magnets (PM) or DC-excitation coils embedded in the stator. Alongside concentrated phase coils in dedicated slots, the spoke-type PMs offer high flux intensification, while the option for DC-excitation coils eliminates demagnetization risks. Since the rotor has no active electromagnetic components, the machine can achieve high-speed operation while enabling advanced cooling systems focused solely on the stator. A special implementation with a “wave” or “serpentine” DC-excitation winding which has the potential for reduced losses depending on the motor aspect ratio is presented. The operation, control, and polarity of the DC-excited variant are analyzed using analytical equations and an examination of the airgap field. The design of experiment-based sensitivity analyses and multi-objective optimization employing differential evolution (MODE) is used to analyze the machine topologies for a power rating of 100kW motor at a speed of 3,000rpm, which is typical for industrial applications. The conflicting objectives of maximizing average torque and minimizing motor losses are considered in both the inner and outer rotor configurations of the proposed motor topologies. Discussions on the performance of the selected “best” designs from each topology and their competitiveness compared to state-of-the-art motors are presented. A DC-excited outer rotor design is analyzed and proposed for EV applications, considering different drive cycles, and a prototype of a PM inner rotor design is constructed and tested, showing competitive performance even at high operating temperatures.