Bearingless slice motor concepts without permanent magnets in the rotor

Abstract

Bearingless permanent magnet motors are very compact and favorable for high speed designs. Especially the bearingless slice motor (using a permanent magnet excited rotor disc) features a mechanically simple and very cost effective fully magnetically levitated system by stabilizing some degrees of freedom by permanent magnetic reluctance forces. This work focuses on constructional possibilities to apply the slice rotor principle with its passive stabilization without any permanent magnets in the rotor part. As a matter of fact, the permanent magnets are necessary and are therefore located in the stator. Possible stator compositions are outlined and separated into homopolar and heteropolar permanent magnet air gap flux types. The definition of performance parameters allows evaluating the operational behavior of the two considered bearingless reluctance slice motor types (one with hompolar and one with heteropolar air gap flux distribution). The composition, optimization and construction of a prototype are outlined in the last section. Measurements are conducted to show the proper functionality of the bearingless reluctance slice motor prototype.