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Measurement and Modelling of Hysteresis Curves for Nonlinear Permanent Magnets at Different Inclination Angles
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.ORCID iD: 0009-0007-6241-8807
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity.ORCID iD: 0000-0001-8773-8961
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solid State Physics.ORCID iD: 0000-0003-2790-116x
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2023 (English)In: 2023 IEEE International Magnetic Conference (INTERMAG), Institute of Electrical and Electronics Engineers (IEEE), 2023Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents the measurement results of the BH/MH curves of the Alnico 8 (LNGT40) with recoil loops and a mathematical model for the calculation of the average magnetic flux density in a cubic permanent magnet. The measurements were performed with a Vibrating Sample Magnetometer (VSM). The magnet samples have a cubic shape with 3 mm sides. BH curves in preferred (easy) and transverse directions and recoil loops were measured and compared to Alnico 9 (LNGT72) as well as to the data from the supplier. The load line of the cubic magnet in 0 A/m applied magnetic field was found. A mathematical model was developed which can approximate the MH a curve for an applied field with an arbitrarily chosen angle between the field and easy axis, given MH a curves for 0o and 90o. Also, a simplified general model of a cubic permanent magnet in the air and calculation results of stored energy and hysteresis losses were presented.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2023.
Series
International Conference on Magnetics, ISSN 2150-4598, E-ISSN 2150-4601
Keywords [en]
Alnico magnets, BH curve, Demagnetization, Permanent Magnet, Recoil Line
National Category
Other Physics Topics Other Electrical Engineering, Electronic Engineering, Information Engineering Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-520985DOI: 10.1109/INTERMAG50591.2023.10265100ISI: 001090594700054ISBN: 979-8-3503-3246-9 (electronic)ISBN: 979-8-3503-3247-6 (print)OAI: oai:DiVA.org:uu-520985DiVA, id: diva2:1829201
Conference
IEEE International Magnetic Conference (INTERMAG), May 15-19, 2023, Sendai, Japan
Part of project
Modelling novel nonlinear permanent magnet materials for energy applications, Swedish Research Council
Funder
Swedish Research Council, 2018-04617StandUpAvailable from: 2024-01-18 Created: 2024-01-18 Last updated: 2024-04-22Bibliographically approved
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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INTERMAG2023(1740 kB)35 downloads
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Ibrayeva, AnarLind, EmilSilva, Marcelo D.Ghorai, SagarEriksson, Sandra

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