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Anisotropic Model of Nonlinear Permanent Magnets in Finite Element Method Software
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity. (Sandra Eriksson)
Department of Electrical Engineering, Indian Institute of Technology Dharwad, Karnataka 580011, India.ORCID iD: 0000-0002-4406-1070
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.ORCID iD: 0000-0001-8598-2565
(English)Manuscript (preprint) (Other academic)
Keywords [en]
Aluminum-nickel-cobalt (Alnico), COMSOL, demagnetization, finite element method (FEM), nonlinear permanent magnets, permanent magnet synchronous generator (PMSG), recoil line
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science
Identifiers
URN: urn:nbn:se:uu:diva-527352OAI: oai:DiVA.org:uu-527352DiVA, id: diva2:1854988
Part of project
Modelling novel nonlinear permanent magnet materials for energy applications, Swedish Research CouncilAvailable from: 2024-04-29 Created: 2024-04-29 Last updated: 2024-04-29
In thesis
1. Nonlinear models of permanent magnets for electrical machines
Open this publication in new window or tab >>Nonlinear models of permanent magnets for electrical machines
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The increased demand for electricity, environmental problems related to mining of rare earth metals and to usage of fossil fuels, national security issues, and monopolization of the rare earth metals market forcing society to explore alternative options for conventional rare earth permanent magnets. Generally, the relationship between magnetic flux density and the magnetic field of permanent magnets has a nonlinear shape, but the operating region of conventional permanent magnets is linear. There is no convenient model of permanent magnets in existing commercial finite element method software that models partial demagnetization and remagnetization of nonlinear permanent magnets correctly. This thesis presents a model that is able to model an electrical machine with nonlinear permanent magnets and does not require a large computational power. A gradual improvement of the model resulted in four versions of it. It started with a simple linear model and ended with a model that is able to simulate partial demagnetization and remagnetization of the magnet and includes all four quadrants of the BH loop. Also, the last version limits the maximum magnetization depending on the angle of normalized magnetization. The magnetic characteristics of Alnico 8 LNGT40 and Alnico 9 LNGT72 magnets were measured in a vibrating sample magnetometer in order to obtain the material data required for this research work. A mathematical model of the MH loops of Alnico 8 LNGT40 in different directions was developed. The models of a synchronous permanent magnet generator with a spoke type topology with Alnico 5, 8 and 9 magnets were tested under normal and three phase short circuit conditions. The results were compared and discussed. It is found Alnico 5 is more sensitive to short circuit than Alnico 8 and 9. Electric steel clamps holding the permanent magnets and airgap above the magnets protect them from demagnetization.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. p. 62
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2404
Keywords
Aluminum-nickel-cobalt (Alnico), COMSOL, demagnetization, finite element method (FEM), nonlinear permanent magnets, permanent magnet synchronous generator (PMSG), recoil line
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-527007 (URN)978-91-513-2136-3 (ISBN)
Public defence
2024-06-13, Room 80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2018-04617
Available from: 2024-05-20 Created: 2024-04-22 Last updated: 2024-05-23

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Westerberg, AnarBoggavarapu, Sai RamEriksson, Sandra

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