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

Magnetodynamic Vector Hysteresis Models for Steel Laminations of Rotating Electrical Machines

Emad Ali Dlala

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 11th of April, 2008, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9277-6)   [2189 KB]
Dissertation is also available in print (ISBN 978-951-22-9276-9)

Abstract

This thesis focuses on the modeling and prediction of iron losses in rotating electrical machines. The aim is to develop core loss models that are reasonably accurate and efficient for the numerical electromagnetic field analysis. The iron loss components, including hysteresis, classical eddy-current, and excess losses, are determined by modeling the dynamic hysteresis loops, whereby the incorporation of the core losses into the field solution is feasible and thus the influence of the core losses on the performance of the machine is investigated.

The thesis presents a magnetodynamic vector hysteresis model that produces not only an accurate, overall prediction of the iron losses, but also explicitly models the magnetization behavior and the loop shapes. The model is found to be efficient, stable, and adequate for providing accurate predictions of the magnetization curves, and hence iron losses, under alternating and rotating flux excitations. It is demonstrated that the model satisfies the rotational loss property and reproduces the shapes of the experimental loops. In addition, a more simplified, efficient, and robust version of the magnetodynamic vector hysteresis model is introduced.

The thesis also aims to analyze the convergence of the fixed-point method, examine the barriers behind the slow convergence, and show how to overcome them. The analysis has proved useful and provided sound techniques for speeding up the convergence of the fixed-point method.

The magnetodynamic lamination models have been integrated into a two-dimensional finite-element analysis of rotating electrical machines. The core losses of two induction motors have been analyzed and the impact of core losses on the motor characteristics has been investigated. The simulations conducted reveal that the models are relatively efficient, accurate, and suitable for the design purposes of electrical machines.

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

  1. Dlala, E., Saitz, J., Arkkio, A., Hysteresis modeling based on symmetric minor loops, IEEE Transactions on Magnetics, Vol. 41 (8): 2343-2348, August 2005. © 2005 IEEE. By permission.
  2. Dlala, E., Saitz, J., Arkkio, A., Inverted and forward Preisach models for numerical analysis of electromagnetic field problems, IEEE Transactions on Magnetics, Vol. 42 (8): 1963-1973, August 2006. © 2006 IEEE. By permission.
  3. Dlala, E., Arkkio, A., Measurement and analysis of hysteresis torque in a high-speed induction machine, IET Electric Power Applications, Vol. 1 (5): 737-742, September 2007. © 2007 The Institution of Engineering and Technology (IET). By permission.
  4. Dlala, E., Belahcen, A., Arkkio, A., Magnetodynamic vector hysteresis model of ferromagnetic steel laminations, Physica B, Vol. 403 (2-3): 428-432, February 2008. © 2008 Elsevier Science. By permission.
  5. Dlala, E., Belahcen, A., Arkkio, A., Efficient magnetodynamic lamination model for two-dimensional field simulation of rotating electrical machines, Journal of Magnetism and Magnetic Materials, to be published, in press, January 2008. © 2008 Elsevier Science. By permission.
  6. Dlala, E., Belahcen, A., Arkkio, A., Locally convergent fixed-point method for solving time-stepping nonlinear field problems, IEEE Transactions on Magnetics, Vol. 43 (11): 3969-3975, November 2007. © 2007 IEEE. By permission.
  7. Dlala, E., Belahcen, A., Arkkio, A., A fast fixed-point method for solving magnetic field problems in media of hysteresis, IEEE Transactions on Magnetics, to be published, in press, January 2008. © 2008 IEEE. By permission.
  8. Dlala, E., Arkkio, A., Analysis of the convergence of the fixed-point method used for solving nonlinear rotational magnetic field problems, IEEE Transactions on Magnetics, to be published, in press, January 2008. © 2008 IEEE. By permission.

Keywords: iron loss, vector hysteresis, ferromagnetic, magnetodynamic, eddy currents, electrical steel, finite element, rotating electrical machines

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© 2008 Helsinki University of Technology

Last update 2011-05-26