Topology and Electromagnetic Force Analysis of Dual-Stator Bidirectional Modulation Machines

This article presents a systematic classification of topologies for dual-stator field modulation machines (DS-FMMs), based on rotor types—namely permanent magnet, iron pole, and consequent-pole—and modulation methods, distinguishing between unidirectional and bidirectional approaches. Two variants of dual stator hybrid multi-excitation machines (DS HMEM-I and DS HMEM-II) are utilized as case studies to illustrate and summarize the various topologies and operating principles associated with bidirectionally modulated machines. Subsequently, an analysis is conducted on the magnetic field modulation effects and air-gap harmonic components of DS-HMEM-I and DS-HMEM-II, comparing their electromagnetic performance against other DS-FMMs. Finally, a radial electromagnetic force analysis is performed on the superior DS-HMEM-I, highlighting the effects of field-modulation harmonics. The findings indicate that DS-HMEM-I exhibit high torque capability and efficiency; furthermore, the interaction among multiple harmonics generates a complex radial electromagnetic force wave characterized by significant amplitude