Radial force modeling for bearingless motors based on analyze of field origins

Abstract

This article proposes a global harmonic analysis of normal and tangential field components in air gap of multiphase bearingless permanent magnet motor topology to determine the radial force. This allows establishing the semi-analytical expressions of the radial force considering the location of field sources. The accuracy of the model is verified by full finite element method model using a statistic approach. An important result of this approach of modeling is that it permits to choose the most convenient topology for the bearingless permanent magnet motors by taking into account the location of the field sources in stator and rotor. In addition, the semi-analytic model allows predicting the force waveforms according to the stator and rotor topologies. The analysis of two different rotor topologies is carried out and it highlights the influence of the tangential component of the air-gap magnetic field on the motor performances. Moreover, the influence of the radial or parallel magnetization of the rotor magnet on the force ripples is discussed. The reduction of CPU time using the semi-analytical model makes it suitable to be implemented in a design optimization process.

Keywords

Bearingless permanent magnet motor radial force semi-analytic model flux density harmonics field source location radial or parallel magnetization

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References

Oshima

Miyazawa

Deido

. Characteristics of a permanent magnet type bearingless motor. IEEE T Ind Appl 1996; 32(2): 363–370.

Chiba

Rahman

Fukao

. Radial force in a bearingless reluctance motor. IEEE T Magn 1991; 27(2): 786–790.

Kang

Huang

Yang

. Analysis and experiment of a 6 phase bearingless induction motor. In: Proceedings of electrical machines and systems (ICEMS), Wuhan, China, 17–18 October 2008, pp.990–994. New York: IEEE.

Okada

Miyamoto

Ohishi

. Levitation and torque control of internal permanent magnet type bearingless motor. IEEE T Contr Syst T 1996; 4(5): 565–571.

Steinert

Nussbaumer

Kolar

. Concept of a 150 krpm bearingless slotless disc drive with combined windings. In: Proceedings of electric machines & drives conference (IEMDC), Chicago, IL, 12–15 May 2013, pp.311–318. New York: IEEE.

Munteanu

Binder

Schneider

. Loss measurement of a 40 kw high-speed bearingless PM synchronous motors. In: Proceedings of Energy Conversion Congress and Exposition (ECCE), Phoenix, AZ, 17–22 September 2011, pp.722–729. New York: IEEE.

Serri

Tani

Serra

. Analytical model of radial forces considering mutual effects between torque and levitation current space vectors in 5-phase PM bearingless motors. In: Proceedings of Industrial Electronics Society (IECON), Vienna, 10–13 November 2013, pp.5142–5147. New York: IEEE.

Schneider

Petersen

Serra

. Influence of pole pair combinations on high-speed bearingless permanent magnet motor performance. In: Proceedings of power electronics, machines and drives (PEMD), York, 2–4 April 2008, pp.707–711. New York: IEEE.

Huang

Kong

. Analysis of half-coiled short-pitch windings with different phase belt for multiphase bearingless motor. J Electr Eng Technol 2014; 9(1): 162–168.

10.

Munteanu

Binder

Schneider

. No-load tests of a 40 kW high-speed bearingless permanent magnet synchronous motor. In: Proceedings of international symposium on power electronics electrical drives automation and motion (SPEEDAM), Pisa, 14–16 June 2010, pp.1460–1465. New York: IEEE.

11.

Zürcher

Nussbaumer

Kolar

. Principles of magnetic levitation force and motor torque generation by superposition of harmonics in bearingless brushless motors. In: Proceedings of industrial electronics (IECON’09), Porto, 3–5 November 2009, pp.1246–1251. New York: IEEE.