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Determining demagnetisation risk for two PM wind power generators with different PM material and identical stators
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2016 (English)In: IET Electric Power Applications, ISSN 1751-8660, E-ISSN 1751-8679, Vol. 10, no 7, 593-597 p.Article in journal (Refereed) Published
Abstract [en]

Ways to utilise ferrite permanent magnets (PMs), in a better way has been in focus the last couple of years since the use of neodymium-iron-boron (NdFeB) PMs has been debated. While ferrite PMs offer a low-cost alternative to rare- earth PMs, it is a trade-off for lower energy density. Depending on the type of PM and if the PMs are surface mounted or buried, the risk of demagnetisation during a fault condition can vary significantly between machines. In this study, the demagnetisation risk of two electrically similar generators with identical stators has been studied during several short- circuit faults at different temperatures. The study is simulation-based, and the results show that the generator with the ferrite rotor will suffer from a small but not significant amount of demagnetisation in the worst, three-phase-neutral, short-circuit case at a temperature of 5°C, whereas the NdFeB PMs will suffer from partial demagnetisation if a fault occurs at 120°C. For operational temperatures between 20 and 60°C both generators will sustain a short-circuit event. 

Place, publisher, year, edition, pages
2016. Vol. 10, no 7, 593-597 p.
Keyword [en]
PM, Electrical machines, Demagnetization, Synchronous generators, Wind power, Comsol Multiphysics
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity; Engineering Science
Identifiers
URN: urn:nbn:se:uu:diva-291371DOI: 10.1049/iet-epa.2015.0518ISI: 000381407900001OAI: oai:DiVA.org:uu-291371DiVA: diva2:925378
Funder
Swedish Research Council, 2010-3950StandUp
Available from: 2016-05-02 Created: 2016-05-02 Last updated: 2017-11-30Bibliographically approved
In thesis
1. Demagnetization and Fault Simulations of Permanent Magnet Generators
Open this publication in new window or tab >>Demagnetization and Fault Simulations of Permanent Magnet Generators
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Permanent magnets are today widely used in electrical machines of all sorts. With their increase in popularity, the amount of research has increased as well. In the wind power project at Uppsala University permanent magnet synchronous generators have been studied for over a decade. However, a tool for studying demagnetization has not been available. This Ph.D. thesis covers the development of a simulation model in a commercial finite element method software capable of studying demagnetization. Further, the model is also capable of simulating the connected electrical circuit of the generator. The simulation model has continuously been developed throughout the project. The simulation model showed good agreement compared to experiment, see paper IV, and has in paper III and V successfully been utilized in case studies. The main focus of these case studies has been different types of short-circuit faults in the electrical system of the generator, at normal or at an elevated temperature. Paper I includes a case study with the latest version of the model capable of handling multiple short-circuits events, which was not possible in earlier versions of the simulation model. The influence of the electrical system on the working point ripple of the permanent magnets was evaluated in paper II. In paper III and VI, an evaluation study of the possibility of creating a generator with an interchangeable rotor is presented.  A Neodymium-Iron-Boron (Nd-Fe-B) rotor was exchanged for a ferrite rotor with the electrical properties almost maintained.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 59 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1444
Keyword
Demagnetization, Permanent magnet, Finite Element Method, Synchronous generators, Wind power
National Category
Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-303517 (URN)978-91-554-9733-0 (ISBN)
Public defence
2016-12-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-11-16 Created: 2016-09-20 Last updated: 2016-11-28

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