Quantitative Analysis of Structure-related Spatial Harmonics on Torque Generation in Hybrid Excited Asymmetric Stator Pole Double Salient Machine for Integrated Machine Drive Applications

Abstract

With the rapid development of integrated machine drives (IMDs), hybrid excited asymmetric stator pole double salient machines (HEASPDSMs) have gained widespread attention owing to their flexible flux regulation ability, excellent heat dissipation capacity, and robust structure. As a type of flux modulation machine, HEASPDSMs exhibit numerous magnetic field harmonics due to their double-sided reluctance structure and introduction of asymmetric stator poles and excitation windings. These harmonics cause significant distortions in airgap flux density, back-electromotive-force (back-EMF), and torque. Traditional magneto motive force (MMF)-specific permeance analytical methods fail to quantify the torque contribution of individual structural-related spatial harmonics, which restricts the torque density improvement of HEASPDSMs. To mitigate the torque distortion and improve torque density, a novel evaluation model for both average torque and torque ripple of HEASPDSMs is proposed in this paper. Different from classical methods, the proposed model directly utilizes stator/rotor MMF and specific permeance as modulation components for torque calculation, which can quantitatively clarify the individual contribution of each modulation harmonic to torque and establish a direct correlation between harmonic contribution and structural parameters. Furthermore, its accuracy is validated via finite element analysis (FEA) by performing single-parameter-scan on four HEASPDSMs with different pole-pair combinations, during which the torque performance and flux regulation ability are analyzed. Finally, experimental validation is performed on a 12s7p HEASPDSM prototype to further verify the proposed model.