Efficient method for eddy current analysis in permanent magnets of electric motors

Article type: Research Article

Authors: Waszak, Michal-Wolfgang^a

Affiliations: [a] Powertrain Systems, Corporate Research, Volkswagen AG, Wolfsburg, Germany

Abstract: This paper presents an efficient method for eddy current analysis in permanent magnets (PM) used in electric machines. Due to appreciable electric conductivity of sintered PM the energy losses related to induced eddy currents cannot be neglected. Since the resulting increase of temperature may weaken the magnetomotive force or even demagnetize the PM material. Two numerical approaches for eddy current calculations in massive materials are commonly applied: 2d model (assuming infinite axial length) and 3d model (usually suffering from numerical inefficiency). In this paper we discuss numerically efficient method for eddy current computation taking actual axial length into account. We propose to extend the 2d field-circuit-motion time-stepping model to 3d model of induced electric field in the area of massive conducting elements, for instance, the PM of electric motor. Design study of a brushless dc motor is presented. During numerical experiments two contributions to the PM losses are characterized: idle run losses due to stator slotting, and armature reaction losses due to high frequency current switching. The influence of the PM segmentation on the eddy current losses is studied.

DOI: 10.3233/JAE-2005-697

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 22, no. 3-4, pp. 133-139, 2005