Tutorial

Tutorial 4	Principles and Current Status of Bearingless Motors
Date/Time	24th May, 2021 Monday / 09:00 - 12:00 hrs
Speakers	Akira Chiba, Tokyo Institute of Technology Eric Severson, University of Wisconsin Madison Wolfgang Gruber, Johannes Kepler University Linz

Abstract

Magnetic suspension has been implemented into industry applications such as canned pumps, compressors for air conditioning, fans and blowers, levitated train systems, and etc. Bearingless motors are a part of magnetically suspended electrical motors with integrated magnetic bearing functions. The goal of this tutorial is to train participants on how and when to use magnetic suspension through bearingless motor concept, that combines electric motors with magnetic bearing functions.

In the first part of the tutorial, participants will learn basic principles, historical test machine developments of bearingless motors. Basic theory of separated winding type bearingless motors is presented, and integration methods of magnetic suspension capability in various PM, induction, synchronous reluctance, consequent-pole, homopolar bearingless motors are presented. In addition, the details of 60kW bearingless motor development is included.

In the second part, the suitability of bearingless motor technology for medium and high power applications is explored by examining results from a recent Transactions review paper. Participants will consider the unique design requirements of magnetically suspended motors for high speed industrial compressor systems. Research efforts to develop bearingless motors for this application are reviewed and promising new developments are identified which show the potential of bearingless motors to alter today’s electric machine design landscape. These innovations include new developments in bearingless induction motors for high speed and significant power applications, unique winding structures for bearingless motors, and bearingless design optimization.

In the third part, combined winding structures in bearingless motors are discussed. These feature more than three phases and motor torque and suspension forces are simultaneously generated in all windings. Phase currents are superposed of drive torque and suspension force components. The advantages are reduced copper loss, simpler manufacture and increased efficiency. In addition, the bearingless slice motor and the bearingless axial force motor are introduced. These devices provide a reduced number of active position regulations, as several degrees of freedom are passively stabilized. Limiting the number of actively regulated axes results in cost down and simplification. The control strategy for such combined winding bearingless motors is addressed and several system developments (e.g, towards high speed and high torque) are shown.

As listed in the relevant publications, a part of the lecturers has been provided a tutorial in 2019 IEMDC in San Diego USA. We could see active involvement of attendees on this topic. This time, I would like to reduce the number of lecturers so that each lecture may have enough time to present from principles and basics.

I also had a one-day tutorial in Lappeenranta in Finland based on my book. Many people came from industries as they are interested in the next step technology. In last year, we published a paper on 60kW 37000rpm bearingless motor with high power density and radial suspension force density. The industrial needs for high power bearingless motors have been increasing recent years.

In 2020, we organized special section in IEEE IAS Transactions on Industry Application for magnetically levitated motor system. The deadline was October in 2020 and we did see considerable number of submission. This fact indicates this topic is timely.

Duration
3 hours

Outline

Magnetic suspension has been implemented into industry applications such as canned pumps, compressors for air conditioning, fans and blowers, levitated train systems, and etc. Bearingless motors are a part of magnetically suspended electrical motors with integrated magnetic bearing functions. The goal of this tutorial is to train participants on how and when to use magnetic suspension through bearingless motor concept, that combines electric motors with magnetic bearing functions. The tutorial is provided by a few experts in this area

Biography

Prof. Akira Chiba chiba@ee.e.titech.ac.jp received the BS., MS. and Ph.D. degrees in Electrical Engineering from the Tokyo Institute of Technology, in 1983, 1985 and 1988, respectively. In 1988, he joined the Tokyo University of Science as a Research Associate in the Department of Electrical Engineering in the Faculty of Science and Technology. Since 2010, he has been Professor in the Graduate School of Science and Engineering in the Tokyo Institute of Technology. He has been studying magnetically suspended bearingless ac motors, super high-speed motor drives and rare-earth-free-motors for hybrid and pure electrical vehicles. He has published more than 1063 papers, including the first book on “Magnetic bearings and bearingless drives” in 2005. He is 2020 IEEE Nikola Tesla Award recipient.

Prof. Eric Severson eric.severson@wisc.edu received the B.Sc. and PhD degrees in electrical engineering from the University of Minnesota, Minneapolis, USA in 2008 and 2015, respectively where he also worked as a post doctoral associate through 2016. He is currently an assistant professor at the University of Wisconsin-Madison, associate director of the Wisconsin Electric Machines and Power Electronics Consortium (WEMPEC), and fellow of the Grainger Institute for Engineering. His research interests include design and control of electric machines and power electronics, with focus areas in magnetic bearings and bearingless motors. Dr. Severson is a recipient of the USA National Science Foundation CAREER Award in 2020, the Department of Defense NDSEG fellowship in 2009, and the National Science Foundation Graduate Research Fellowship in 2009.

Prof. Wolfgang Gruber wolfgang.gruber@jku.at received the Dipl.-Ing. (M.Sc.) degree in Mechatronics and Dr. techn. (PhD) degree in Technical Sciences from Johannes Kepler University (JKU), Linz, Austria, in 2004 and 2009, respectively. Since 2012 he has been Assistant Professor and since 2018 Associate Professor in the Institute of Electrical Drives and Power Electronics at JKU. Since 2004 he also is Senior Researcher at the R&D company Linz Center of Mechatronics GmbH (LCM). His research has focused on new topologies for bearingless slice motors, their design, setup and control. He has developed the bearingless segment motor, reluctance motor, flux-switching motor, and PM Vernier motor. Dr. Gruber received the international Nagamori Award in 2015.

Relevant publications

[1] 2019 IEMDC tutorial “ Lose Your Bearings: A Deep Dive into Magnetically Suspended Motors ” by five lectures below

• Eric Severson, University of Wisconsin Madison, eric.severson@wisc.edu

• Akira Chiba, Tokyo Institute of Technology, chiba@ee.e.titech.ac.jp

• Wolfgang Gruber, Johannes Kepler University Linz, wolfgang.gruber@jku.at

• Christof Zwyssig, Celeroton AG, christof.zwyssig@celeroton.com

• Rafal Jastrzebski, Lappeenranta University of Tec

[2] J. Chen, J. Zhu and E. L. Severson, "Review of Bearingless Motor Technology for Significant Power Applications," in IEEE Transactions on Industry Applications, vol. 56, no. 2, pp. 1377-1388, March-April 2020.