Finite Element Modeling of Eddy Currents in Uninsulated Laminated-Steel Stacks
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Sähkötekniikan korkeakoulu |
Master's thesis
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Author
Date
2013-05-20
Department
Major/Subject
Electromechanics
Mcode
S-17
Degree programme
EST - Master’s Programme in Electrical Engineering
Language
en
Pages
76+7
Series
Abstract
This thesis deals with the modeling of eddy currents in uninsulated laminations. A numerical model for the calculation of eddy current losses was implemented using finite element analysis. This model calculates the solution from the electric vector potential also known as the T-𝛺 formulation for the study of eddy current problems. The numerical model was verified by comparing the harmonic solution to different analytical models. Moreover, the results were obtained for non-linear material, i.e. electrical steel. During the manufacturing process the laminations are stacked and the uneven contact between laminations makes it impossible to assume uniformity in conductivity between adjacent laminations. Electrical conductivity degradation and surface roughness in laminated-steel increases the average iron losses. Whenever the values of inter-laminar conductivity tend to zero, the eddy current component in the direction perpendicular to the lamination vanishes. For this reason, the eddy currents will loop only within the thickness of the lamination and the losses will decrease dramatically for a certain frequency range. Assuming a linear permeability (low and high) in the inter-laminar region, and widths between 6𝜇m and 10𝜇m, causes negligible changes in the calculation of the losses for which is recommended to use wider inter-laminar areas and high permeability, as it enhances the convergence of the model. A model dealing with insulated laminated-stacks was implemented for comparison purposes. Uninsulated laminations could be used as an economical alternative for certain applications where laminated cores are used, as in the case of rotational electrical machines and transformers.Description
Supervisor
Arkkio, AnteroThesis advisor
Belahcen, AnouarRasilo, Paavo
Keywords
Computational Electromagnetics, Finite Element Analysis, Electrical Machines, Iron Losses, Eddy Currents, Steel Laminations
