Asymmetrical rotor topologies were previously proposed for synchronous reluctance motors (SynRM) to reduce the torque ripple. However, potential negative effect of these topologies on mechanical vibration, which is often serious in SynRM, was hardly studied and such an effect is investigated here. An analytical model is established, through which the spatial orders of the radial electromagnetic force with various rotor topologies are derived, and the relationship of the peak frequencies and the corresponding spatial orders in the radial electromagnetic force is revealed. It is shown that some asymmetric rotor topologies will reduce the order of the lowest spatial harmonic for the radial electromagnetic force, and consequently increase the vibration. Finite element analysis and experiments demonstrate the same results. Finally, a specific rotor topology with asymmetry about both d-axis and q-axis is recommended, which can reduce the torque ripple, but would not deteriorate the radial electromagnetic force and vibration.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
One of the main challenges in motor design is the winding layout, including winding distributions and magnetomotive force (MMF) harmonic analysis. Considering some shortcomings in the existing theories for winding distributions and difficulties in dealing with unconventional fractional‐slot windings, a unified theory of symmetric winding distributions is proposed. First, this study gives the sufficient and necessary conditions for a m‐phase symmetric winding and the novel winding distribution formula. Subsequently, a general method for MMF harmonic analysis including the amplitude of MMF harmonics and harmonic orders are proposed. Finally, the analysis results show that this unified theory is an efficient and compact method to deal with the winding layout to analyse all kinds of winding MMF harmonics.
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