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ABSTRACT: A bearingless motor combines the functions of both noncontact magnetic suspension and torque generation in a single motor unit. Therefore, it offers advantages such as no grease lubrication, no contamination, and can be maintenance free. For low speed rotating and swinging stages (or platforms), the authors have developed a multi-consequent-pole bearingless motor. It has 40 poles and 48 slots with two-pole toroidal suspension windings. The advantage of the multi-pole bearingless motor is its low suspension force variation compared with other bearingless motors with low pole numbers. The aim of this paper is to evaluate the suspension force performance of the bearingless motor. The measured suspension force differed by 21% from the calculated three-dimensional finite element method (3D-FEM) results. It was found that the discrepancy is caused by the number of mesh elements in the 3D-FEM calculation, manufacturing and assembly errors, and the iron stack fill factor.
IEEE Transactions on Magnetics 11/2011; · 1.36 Impact Factor
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ABSTRACT: A multi-consequent-pole bearingless motor which is adapted to low speed rotation is presented. The bearingless motor can be used in swinging stages (or platforms) under specific conditions. Two degrees of freedom (2DOF) are actively controlled in the radial x-y directions. A gap sensor is required to control each DOF. Although 2DOF bearingless motors almost have a flat rotor so that axial length of the rotor is small, the device needs gap sensors and its target. In this paper, a novel stator structure is proposed and a design procedure considers the installation of the gap sensors on the stator. Three dimensional finite element analyses are carried out. An amplitude pulsation and a direction error of the radial suspension force with respect to the rotor rotational angular position are evaluated. Two machines with a conventional stator and the proposed stator are tested and compared. It is shown the proposed machine has beneficial performance by experimental verification.
IEEE Transactions on Magnetics 07/2009; · 1.36 Impact Factor
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ABSTRACT: Multi-consequent-pole bearingless motors can be used in low speed rotating and swinging stages (or platforms) under specific conditions. A test machine has been designed and built and in this machine two axes of freedom are actively controlled in the radial x-y directions. The suspension windings are of a novel toroidal shape, i.e., they are wound around the stator yoke. This produces a low axial length because the coil ends are compact. In the paper, a multi-consequent-pole rotor design is presented. The design procedure considered the leakage fluxes and magnetic saturation and used a three dimensional finite element analysis before the machine was constructed and tested. This paper proposes a novel structure for the suspension windings and the rotor. The suspension of the rotor was found to be successfully achieved and these characteristics are put forward in the paper.
Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on; 11/2008
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ABSTRACT: For low speed applications, such as rotating and swing stages, a multi-consequent-pole bearingless motor is proposed. This paper describes basic characteristics of a multi-consequent-pole bearingless motor. Unlike conventional bearingless motors, suspension force generating on consequent-pole type is independent of rotor rotational position. Thus, multi-pole rotors such as 40, 44, and 46 poles are easy without a penalty of high precision in rotating angular position detection. Basic design of pole number selection is discussed with suspension force and average torque capability. Magnetic force error can be reduced with multi-pole rotor configuration. A test machine has been constructed and driven by a compact drive and a CPU unit.
Power Conversion Conference - Nagoya, 2007. PCC '07; 05/2007
