Electrical Engineering

, Volume 100, Issue 2, pp 389–399 | Cite as

An asymptotic approximation of the magnetic field and forces in electrical machines with rotor eccentricity

  • Felix Boy
  • Hartmut Hetzler
Original Paper


In this contribution, a systematic asymptotic derivation of approximate solutions to the magnetic field problem in rotating electric machines with an eccentrically running rotor is proposed. It is consistent with the well-known permeance harmonic method and can be seen as an alternative view on the derivation of the magnetic flux density and resulting lateral forces in the air gap of the machine. The asymptotic expansion is based on a purely geometric small parameter and applies even for large rotor eccentricities. The advantage of this method lies in its extensibility towards higher approximation orders, and in the fact that it is possible to quantify the order of the involved approximation error. The discussion includes two examples and a numerical verification.


Electrical machines Eccentric rotor Magnetic field Asymptotic expansion Unbalanced magnetic pull 


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Copyright information

© Springer-Verlag Berlin Heidelberg 2017

Authors and Affiliations

  1. 1.Engineering Dynamics Group, Department of Mechanical Engineering, Institute of MechanicsUniversity of KasselKasselGermany

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