Design and Operation Performance Analysis of a Novel Three-Segment V-Shape Series–Parallel Variable-Flux Machine

As a competitive candidate for transportation applications, variable-flux machines (VFMs) are widely developed, owing to the abilities of extending the operating speed range and improving the efficiencies in high-speed region. While the traditional VFMs face the problems that the flux-regulation range of the series structure is limited, and the torque-output capability of the parallel structure is low. The research of this article focuses on a novel three-stage V-shaped series–parallel VFM (TSV-SPVFM), which can balance the flux-regulation range and torque-output capability well. The equivalent magnetic circuit model is established for the TSV-SPVFM to elaborate the flux-regulation principle, and realize the preliminary analysis. The performance of the machine, including electromagnetic torque, speed-expansion capacity, and efficiency characteristics under different magnetization states (MSs), are analyzed. Accordingly, the speed control method based on the typical MSs is established, by which the machine can maintain high efficiency while reaching the maximum torque-speed range, and avoid frequent MS switching. A prototype is designed and manufactured, and the experimental platform is built to verify the performance of the machine. The experiment results prove that the machine has wide speed range and high efficiency in high-speed area.