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.
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Macro Element Method for Modeling Eddy Currents in the Multi-Conductor Windings of Electrical Machines

Áron Szücs

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 9th of November, 2001, at 12 o'clock.

Overview in PDF format (ISBN 951-22-5691-6)   [2083 KB]
Dissertation is also available in print (ISBN 951-666-582-9)

Abstract

The computation of the magnetic field in electromagnetic devices - especially rotating electrical machines - usually excludes the effect of eddy currents in the multi-conductor windings. Eddy-current losses are frequently calculated from a magnetic field solution in which the effect of eddy currents is not considered. The aim of this research has been the development of efficient methods to consider the effect of eddy currents in multi-conductor windings accurately within electromagnetic field computation. There are methods, which take the effect of eddy currents on the magnetic field into account in multi-conductor windings but all those approaches have serious drawbacks. Analytical formulations lead to very complicated models while numerical analysis leads to enormously large problem size for many conductors or in small penetration depth cases. The thesis suggests a novel combination of the elimination of inner nodes method with the conventional finite element technique. Based on the magnetic linearity of the winding regions the creation of numerical macro elements is suggested. The Gauss elimination of the nodes inside the finite element model of the multi conductor winding resulted in significantly decreased problem size and in accelerated solution of the system of equations in the nonlinear iteration process. The new macro element method, has been developed by the creation of constant macro elements for the duration of the whole time-stepping analysis. The macro element method has been verified with test computations and it is found to be faster in nonlinear problems and it requires significantly less memory than the traditional approach. The advantages and limitations of the method are presented in this thesis.

This thesis consists of an overview and of the following 6 publications:

  1. Szücs, Á., Arkkio, A., Palko, S., Saitz, J. and Yatchev, I. 1996. Study of electrical machines, using a new interactive finite element preprocessor. Proceedings of PEMC'96, Budapest, Hungary, 2-4 September 1996, Vol. 2, pp. 273-277.
  2. Áron Szücs, Antero Arkkio, 1999. Consideration of Eddy Currents in Multi-Conductor Windings Using the Finite Element Method and the Elimination of Inner Nodes, IEEE Transactions on Magnetics, Volume 35, Number 3, Part I of two parts, May 1999.
  3. Áron Szücs, Antero Arkkio, 1998. Newton Raphson Iteration Using the Finite Element Method and the Elimination of Inner Nodes for the Consideration of Eddy-Currents in Multi-Conductor Windings at IEEE CEFC'98 The Eighth Biennial IEEE Conference on Electromagnetic Field Computation, Tucson, Arizona, USA, June 1-3, 1998.
  4. Áron Szücs, 2000. Macro Elements In the Finite Element Analysis of Multi-Conductor Eddy-Current Problems, IEEE Transactions on Magnetics, Volume 36, Number 4, July 2000.
  5. Áron Szücs, 2000. Advanced Utilization of Macro Elements that Replace the Multi-Conductor Windings in the Finite Element Analysis of Rotating Electrical Machines, Laboratory Report, No. 66, 12 p, 2001, Helsinki University of Technology, Laboratory of Electromechanics.
  6. Áron Szücs, Antero Arkkio, Tapani Jokinen, 2000. Modeling of Eddy Currents in the Stator Winding of Asynchronous Machines Using Macro Elements at ICEM 2000 Proceedings of the International Conference on Electrical Machines, Helsinki, Finland, August 28-30, 2000.

Keywords: eddy currents, finite element methods, machine windings, macro elements, skin effect

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© 2001 Helsinki University of Technology

Last update 2011-05-26