Abstract
Doubly-fed flux reversal permanent magnet (DF-FRPM) machine with two independent armature windings accommodating in stator and rotor slots separately exhibits larger torque density than conventional FRPM due to higher utilization rate of rotor space. In this paper, the investigation is focused on the airgap field modulation and torque contribution of dominating harmonics in DF-FRPM machine. Besides the open-circuit airgap flux density, both stator and rotor armature reaction are qualitatively analyzed by magneto-motive force (MMF)-permeance model considering stator and rotor saliency since the two independently supplied armature windings both make contributions to the torque production. The pole pairs and rotating speed of field harmonics are addressed. Dominating field harmonics that contribute to electromagnetic torque are identified and validated by finite element (FE) analysis.
Highlights
The rapid industrial and technological developments make human society more convenient and bring challenges to environment protection
The results shows that there are abundant airgap field harmonics in both open-circuit and stator armature reaction fields, including those with and without modulation
The dominating rotor armature reaction airgap field harmonics are mostly those without modulation, since the modulation of stator permeance to rotor armature reaction magneto-motive force (MMF) is weak due to the small stator opening ratio
Summary
The rapid industrial and technological developments make human society more convenient and bring challenges to environment protection. Based on the airgap field harmonic modulation, the same analysis method has been frequently used to analyze other type of machines, such as flux switching machines [16], Vernier PM machines [17], fractional slot concentrated winding PM machines [12] and double stator electrical excitation synchronous machines [18]. This paper is focused on the qualitative investigation of airgap field modulation and field harmonics of DF-FRPM machines using MMF-permeance model considering both rotor saliency and stator saliency, based on a 12-stator-slot/14-rotor-slot DF-FRPM machine, see Fig. 1. The dominating pole-pairs and rotating speeds of open-circuit, together with stator and rotor armature reaction airgap field harmonics that conduce to average torque in the DF-FRPM machine are fully discussed in this paper, which reveals its torque improvement mechanism.
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