Abstract
This paper introduces a bearingless motor topology with a magnet-free rotor that provides a higher rotor torque density and wider magnetic air gap compared to previously published topologies. The stray flux is minimized by using a stator with only eight teeth in temple configuration that contain permanent magnets. The motor performance is analyzed based on experimental prototypes, that were designed using 3D FEM simulations, for even and odd rotor pole pair numbers of six and nine, respectively. Control schemes that compensate parasitic radial forces to achieve stable magnetic levitation of the rotors are presented. The implemented prototypes reached a rotational speed of 2000 rpm and a maximum torque of 8 Nm.
Highlights
Bearingless slice motors, featuring a magnetically levitated rotor and a stator with a magnetically integrated bearing function [1], are used in several commercial products [2]
Its capability to generate high tangential forces makes the considered flux-switching permanent magnet (FSPM) topology well suited for achieving high toque densities [31]
The nominal flux values are marked by red asterisks, which shows that a similar operating region at the onset of saturation is obtained for both topologies
Summary
Bearingless slice motors, featuring a magnetically levitated rotor and a stator with a magnetically integrated bearing function [1], are used in several commercial products [2]. Topologies of bearingless motors without permanent magnets (PMs) in the rotor have been published previously [7] Such topologies can be designed to feature low mechanical complexity [8], a large air gap [9], or high torque per stator PM mass [10]. The magnetic air gap length can be reduced, resulting in a worse thermal insulation of the rotor To overcome these limitations, a new bearingless temple motor topology [15], [16], as shown, is presented in this work. Most research on flux-switching permanent magnet (FSPM) motors has been carried out for small air gaps and large numbers of stator and rotor teeth, with 12/10 being a popular combination [17]–[19] with the lowest number of teeth.
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