The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Electromagnetic Forces Acting Between the Stator and Eccentric Cage Rotor

Asmo Tenhunen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 22nd of August, 2003, at 12 o'clock noon.

Overview in PDF format (ISBN 951-22-6683-0)   [2544 KB]
Dissertation is also available in print (ISBN 951-22-6682-2)

Abstract

Electromagnetic forces act between the rotor and stator when the rotor is performing eccentric motions with respect to the stator. The aim of this research was to study the charactarestics of the forces and develop the tools to calculate these forces accurately and as quickly as possible.

A new method, called the impulse method, is developed into the finite element analysis of the electromagnetic field to calculate the forces for a wide whirling frequency range by one simulation. The idea of the impulse method is to move the rotor from its central position for a short period of time. This displacement excitation disturbs the magnetic field and, by doing this, produces forces between the rotor and stator. Using spectral analysis techniques, the frequency response function of the forces is calculated using the excitation and response signals. The impulse method is based on the assumption of the spatial linearity of the force.

The impulse method is utilised in the analysis of the rotor eccentricity. The spatial linearity of the force and the effects of the circulating currents and saturation on the forces are studied herein.

The field of investigation is enlarged from the cylindrical whirling motion to the conical motions of the rotor. The modelling of the conical motion requires that the axial variations of the magnetic field be taken into account. This is done by multislice finite element analysis.

This thesis consists of an overview and of the following 8 publications:

  1. Tenhunen, A. and Arkkio, A., 2001. Modelling of induction machines with skewed rotor slots. IEE Proceedings - Electric Power Applications, Vol. 148, No. 1, January 2001, pages 45-50. © 2001 IEE. By permission.
  2. Tenhunen, A., 2001. Finite-element calculation of unbalanced magnetic pull and circulating current between parallel windings in induction motor with non-uniform eccentric rotor. Proceedings of Electromotion'01. Bologna, Italy, 19-20 June 2001, pages 19-24. © 2001 by author.
  3. Tenhunen, A., Holopainen, T. P. and Arkkio, A., Impulse method to calculate the frequency response of the electromagnetic forces on whirling cage rotors. IEE Proceedings - Electric Power Applications, accepted for publication. © 2003 by authors and © 2003 IEE. By permission.
  4. Tenhunen, A., Holopainen, T. P. and Arkkio, A., 2003. Spatial linearity of unbalanced magnetic pull in induction motors during eccentric rotor motions. COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, Vol. 22, No. 4, accepted for publication. © 2003 by authors and © 2003 Emerald. By permission.
  5. Tenhunen, A., Holopainen, T. P. and Arkkio, A., 2003. Effects of saturation on the forces in induction motors with whirling cage rotor. Proceedings of Compumag'03, Vol. II. Saratoga Springs, NY, USA, 13-18 July 2003, pages 66-67. © 2003 by authors.
  6. Tenhunen, A., Holopainen, T. P. and Arkkio, A., 2003. Effects of equalizing currents on electromagnetic forces of whirling cage rotor. Proceedings of IEMDC'03, Vol. 1. Madison, WI, USA, 1-4 June 2003, pages 257-263. © 2003 by authors.
  7. Tenhunen, A., Benedetti, T., Holopainen, T. P. and Arkkio, A., Electromagnetic forces of the cage rotor in conical whirling motion. IEE Proceedings - Electric Power Applications, accepted for publication. © 2003 by authors and © 2003 IEE. By permission.
  8. Tenhunen, A., Benedetti, T., Holopainen, T. P. and Arkkio, A., 2003. Electromagnetic forces in cage induction motors with rotor eccentricity. Proceedings of IEMDC'03, Vol. 3. Madison, WI, USA, 1-4 June 2003, pages 1616-1622. © 2003 by authors.

Errata of publications 1, 7 and 8

Keywords: induction motor, electromagnetic force, finite element analysis, impulse method, eccentricity, whirling motion

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© 2003 Helsinki University of Technology

Last update 2011-05-26