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A novel consequent-pole bearingless motor is proposed with a unique combined winding structure of parallel motor windings for mixing applications, such as agitators used to mix fluids in the pharmaceutical or food industry. Bearingless motors can be used to achieve high purity and no contamination in these mixing applications. The principles of the magnetic suspension force and torque generation are presented by calculating the magnetomotive force (MMF) distributions with two different magnetic field. In addition, the error angle of the suspension force is evaluated in several pole/slot combinations with the proposed combined winding using 3-D finite element analysis. As a result, 20-pole/24-slot was found to be the best configuration, because it has the least direction and amplitude variations in the radial suspension force generation. A prototype of the proposed 20-pole/24-slot bearingless motor was built and tested. The stable magnetic suspension start-up and rotation can be successfully achieved in the experiment. The measured waveforms of the rotor displacement and the U-phase current while the rotor is magnetically suspended and rotated are shown. It is confirmed by calculations and experiments that the proposed combined winding is effective for stable radial magnetic suspension and rotation. [ABSTRACT FROM AUTHOR]

A novel structure design and experimental results of a one-axis actively positioned single-drive bearingless motor is proposed. This new single-drive bearingless motor is proposed by adapting the 4-pole 2-layer permanent magnet rotor and a wide air-gap length for high rotational speed operation. It is found that the rotational speed of 30 000 r/min is experimentally possible, although around 16 000 r/min top speeds were reported in the literature in only one-axis active magnetic suspension. In the machine design stage, it is shown that a wide gap length provides an efficiency improvement with a reduced risk of possible radial position touchdown. [ABSTRACT FROM AUTHOR]

One-axis actively positioned bearingless motors have been studied for industry applications such as pumps and cooling fans. In particular, single-drive bearingless motors have a great advantage of a simple regulation system. Only one three-phase inverter is required for generating torque and active axial force by q- and d-axis currents. On the other hand, radial and tilting motions of the rotor shaft are passively stabilized by passive magnetic bearings. These passive force and torque are just spring force. Inherently, damping force and torque are not generated. As a result, the rotor vibrations in the radial and tilting directions are considerably high at resonant frequencies. In this article, a valuable strategy is proposed to pass through the critical speed by high angular acceleration with a fan blade. The dynamic modeling of the radial and tilting motions is proposed and simulated to find out the possibility to pass through the critical speed. In the experiment, it is demonstrated that a prototype machine of the one-axis actively positioned bearingless motor can successfully pass through the critical speed without touch-down. [ABSTRACT FROM AUTHOR]

This paper presents a novel stator structure in an actively positioned bearingless motor with 1-degree of freedom. The single-drive bearingless motor concept has been adapted so that the torque and active axial force are regulated independently by the q- and d-axis currents, respectively, with only one three-phase inverter. The axial z-axis position is actively regulated, but the other axes (i.e., the radial and tilting movements) are passively stabilized. A novel stator structure has been proposed to enhance the active axial force. The stator is designed with soft magnetic composites. Experiments confirmed that the active axial force is enhanced by 50%. [ABSTRACT FROM AUTHOR]

We present a method for reducing vibration in a one-axis actively positioned single-drive bearingless motor with repulsive passive magnetic bearings. The single-drive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension force, regulating the $q$- and $d$-axis currents, respectively, driven by only one three-phase inverter. Single-drive bearingless motors have the advantage of low cost. Only the axial $z$-axis is actively positioned. The radial and tilting directions are passively stabilized. Therefore, passive axis vibrations are one of the few serious problems. In this paper, we show that radial vibration originates in axial vibration. In particular, the second-order harmonic vibration with respect to rotational speed is a factor. In theoretical calculations, we derive the relationship between axial and radial vibrations. Additionally, vibration reduction methods are proposed. Finally, experiments confirm that radial vibration is reduced by 59%. [ABSTRACT FROM AUTHOR]

In this paper, a novel single-drive bearingless motor with cylindrical radial air-gap is proposed. The single-drive bearingless motor has only one set of three-phase windings. It generates both torque and axial suspension force independently with only one three-phase inverter and one displacement sensor. Therefore, this single-drive bearingless motor has the advantages of low cost and small size. Only axial direction \boldsymbolz-axis is actively positioned. The other axes, radial movements \boldsymbolx and \boldsymboly, and tilting movements \boldsymbol\theta\boldsymbol {x} and \boldsymbol \theta\boldsymbol{y}, are passively stable. In the proposed motor, the rotor is a cylindrical permanent magnet magnetized in a radial parallel direction. The stator consists of six C-shaped cores and one set of three-phase windings. The principles of the suspension force and torque generations by the \boldsymbold- and \boldsymbolq-axis currents, respectively, are shown. The proposed machine was fabricated and tested only to confirm the principles. In the experiments, start-up was successfully achieved. In an acceleration test up to 3600 r/min, stable magnetic suspension and speed regulation by the \boldsymbold- and \boldsymbolq-axis current regulations were confirmed. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]