Basic Elements Acting Mechanism of Electrical Machines from the Perspective of the Airgap Field Modulation Theory

The objective of this paper is to investigate the mechanism of the three basic elements of electrical machines, namely the source, modulator and filter, acting separately and together from the perspective of the general airgap field modulation theory. Evolution of individual elements on the modulation effects are illustrated by representative topologies, based on which the mutual coupling relation of the basic elements is demonstrated. For instance, the variation of the source or filter has an obvious effect on the modulator such as local saturation, and the principal pole pair combinations of source and filter then the effective harmonic components in modulated airgap field are mutually interrelated etc. In addition, different kinds of modulation behaviors due to the element spatial adjustment are introduced to provide initial design and future topology optimization guidance. It is proven that it is possible to enhance the output characters of a typical magnetic field modulated machine via reasonable selection of element configuration. Electromagnetic performances evolution based on 2-D finite element analysis together with experimental verifications are provided to demonstrate the effectiveness of theoretical analysis.