Flux-Weakening Capability Enhancement of a Zero-Sequence Current Excitation Based Pole-Changing Permanent Magnet Machine

This paper presents a novel pole-changing machine with both zero-sequence current and permanent magnet excitation aiming to improve flux-weakening capability. The primary focus is on changing the pole-pair numbers by regulating the direction of DC current excitation. Through pole-changing operation, the polarity of the air gap magnetic field has been changed, thereby changing the frequency of the proposed machine. With the proposed design, the air-gap magnetic field is effectively weakened, and the speed range of the proposed machine is expanded accordingly. The paper presents the machine’s configuration and winding distributions, along with the analysis of the pole-changing principle. Finally, the electromagnetic performance of the proposed machine is examined and validated using the finite element method.