Design and Analysis of Bearingless Synchronous Reluctance Machines

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2020-10-16
Degree programme
86 + app. 48
Aalto University publication series DOCTORAL DISSERTATIONS, 133/2020
A bearingless machine is a special type of electrical machine where the mechanism to levitate the rotor is integrated into the machine design. This thesis focuses on modelling and analysing different electromechanical behaviours of bearingless synchronous reluctance machines. Three models have been developed for different computational requirements, which include one finite element model, one reduced-order model and one analytical model. The models yield reasonably accurate results which are subsequently verified by the experimental results from a prototyped machine. It is found that the levitation force generation influences the iron losses of the machine, especially the hysteresis component. The vibration characteristics of the machine are also influenced by the levitation force production. Using numerical simulations, it is shown that the vibration components can be used to track the rotor displacement from the centre of the stator. The proposed analytical model clearly explains the variations in the inductance components of the machine's windings with the rotor's displacement. A novel algorithm has been proposed for the reduced-order model since the snapshot matrix selection requires additional consideration due to the complexities raised from the levitation force production. The levitation force ripple appears to be a major concern due to the properties of the reluctance rotor. The force harmonics are modelled with a novel method and an indexing technique which improve the understanding of the forces produced by the spatial harmonics of the magnetic flux density. Different reluctance rotor designs are investigated showing that a design compromise lies between maximising average torque, levitation force and minimising their corresponding ripple.
A doctoral dissertation completed for the degree of Doctor of Science (Technology) to be defended, with the permission of the Aalto University School of Electrical Engineering, Remote connection link , on 16 October 2020 at 12 noon.
Supervising professor
Belahcen, Anouar, Prof., Aalto University, Dept. of Electrical Engineering and Automation., Finland
Thesis advisor
Rasilo, Paavo, Prof., Tampere University, Finland
Martin, Floran, Dr., Aalto University, Finland
bearingless, eccentricity, electromagnetic force, levitation, reluctance rotor
Other note
  • [Publication 1]: Mukherjee, Victor; Farzam Far, Mehrnaz; Martin, Floran; Belahcen, Anouar. 2017. Constrained Algorithm for the Selection of Uneven Snapshots in Model Order Reduction of a Bearingless Motor. IEEE Transactions on Magnetics, volume 53, issue 6, pages 1-4, June 2017.
    DOI: 10.1109/tmag.2017.2664505 View at publisher
  • [Publication 2]: Belahcen, Anouar; Mukherjee, Victor; Martin, Floran; Rasilo, Paavo. 2018. Computation of Hysteresis Torque and Losses in a Bearingless Synchronous Reluctance Machine. IEEE Transactions on Magnetics, volume 54, issue 3, pages 1-4, March 2018.
    DOI: 10.1109/TMAG.2017.2765080 View at publisher
  • [Publication 3]: Mukherjee, Victor; Rasilo, Paavo; Martin, Floran; Belahcen, Anouar. 2019. Effect of Magnetic Forces and Magnetostriction on the Stator Vibrations of a Bearingless Synchronous Reluctance Motor. IEEE Transactions on Magnetics, volume 55, issue 6, pages 1-4, June 2019.
    DOI: 10.1109/TMAG.2019.2894739 View at publisher
  • [Publication 4]: Mukherjee, Victor; Sokolov, Maxim; Pippuri, Jenni; Hinkkanen, Marko; Belahcen, Anouar. 2019. Comparative study of inner and outer rotor bearingless synchronous reluctance motors. The Journal of Engineering, volume 2019, issue 17, pages 4375-4379, June 2019.
    Full text in Acris/Aaltodoc:
    DOI: 10.1049/joe.2018.8195 View at publisher
  • [Publication 5]: Mukherjee, Victor; Rasilo, Paavo; Martin, Floran; Belahcen, Anouar. Analysis of Electromagnetic Force Ripple in a Bearingless Synchronous Reluctance Motor. Submitted to the IEEE Transactions on Magnetics, April 2020
  • [Publication 6]: Saarakkala, Seppo; Mukherjee, Victor; Sokolov, Maxim; Hinkkanen, Marko; Belahcen, Anouar. Analytical Model Including Rotor Eccentricity for Bearingless Synchronous Reluctance Motors. XIII International Conference on Electrical Machines (ICEM), Alexandroupoli, pages1388-1394, September 2018.
    Full text in Acris/Aaltodoc:
    DOI: 10.1109/ICELMACH.2018.8506892 View at publisher