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Air Gap Magnetic Flux Density Variations due to Manufacturing Tolerances in a Permanent Magnet Synchronous Generator
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Wind power group)ORCID iD: 0000-0003-3341-6910
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Wind power group)ORCID iD: 0000-0001-8598-2565
2016 (English)In: 2016 XXII INTERNATIONAL CONFERENCE ON ELECTRICAL MACHINES (ICEM), IEEE, 2016, p. 93-99Conference paper, Published paper (Refereed)
Abstract [en]

The impact of manufacturing tolerances on the performance of a permanent magnet synchronous generator is investigated. A generator with a flux concentrating spoke-type rotor, with ferrite permanent magnets, is used in the investigation. Measurements of the air gap magnetic flux density, the air gap length, as well as the magnetization and size of the permanent magnets have been performed. Correlations are calculated and causalities are discussed. It is found that the permanent magnets used are below tolerance in remanent magnetic flux density, that the air gap length is smaller than specified, and that the resulting air gap magnetic flux density is lower than specified. From the results it can be concluded that the design should be made with tolerances in mind and that quality control of parts, especially of PM magnetization, is important for machine performance.

Place, publisher, year, edition, pages
IEEE, 2016. p. 93-99
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-292962DOI: 10.1109/ICELMACH.2016.7732511ISI: 000390884900012ISBN: 978-1-5090-2538-1 (electronic)OAI: oai:DiVA.org:uu-292962DiVA, id: diva2:928665
Conference
22nd International Conference on Electrical Machines (ICEM), SEP 04-07, 2016, Lausanne, SWITZERLAND
Funder
Swedish Research Council, 2012-4706ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 12-295Available from: 2016-05-16 Created: 2016-05-11 Last updated: 2018-11-22Bibliographically approved
In thesis
1. Rare Earth Metal–Free Permanent Magnet Generators
Open this publication in new window or tab >>Rare Earth Metal–Free Permanent Magnet Generators
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Permanent magnet (PM) synchronous generators (SGs) are used in renewable energy production. The preferred PM material is neodymium-iron-boron (NdFeB), which has very high performance and, until recently, low cost. In recent years there has emerged a cost and supply insecurity in NdFeB PMs due to export restrictions imposed by China, where the majority of the raw materials are produced. In this thesis various methods of avoiding the use of PM materials based on NdFeB, or other rare earth metals, are investigated.

One approach is the use of the cheap and abundant ferrite PM. A ferrite PM rotor intended to be interchangeable with an NdFeB PM rotor is designed and built. Some initial investigation of the performance of the new rotor, and how this relates to manufacturing tolerances, is also made.

Another approach is to make parameter studies in anticipation of new PM materials. A study of how three different rotor topologies perform with different PM materials, described by their remanence and recoil permeability, is made. The rotor topologies are: a spoke type PM rotor, a surface mounted PM rotor and a capped PM rotor.

It is concluded that a viable replacement rotor can be designed using ferrite PMs. The new rotor will be heavier and mechanically more complex, and give slightly lower output voltage. Losses in the machine will increase slightly. A study is made on the impact of manufacturing tolerances on the performance of the resulting rotor.

The different rotor topologies work best with different PM material properties. The surface mounted PM and capped PM rotors require higher remanence for good performance; the spoke type PM rotor works well with larger amounts of low remanence material. The recoil permeability should be low for the surface mounted and high for the capped PM rotor.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, Institutionen för teknikvetenskaper, 2016. p. 51
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; UURIE 348-16L
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-292963 (URN)
Presentation
2016-06-13, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2012-4706ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 12-295
Available from: 2016-07-07 Created: 2016-05-11 Last updated: 2016-07-07Bibliographically approved
2. Design of Rare Earth Free Permanent Magnet Generators
Open this publication in new window or tab >>Design of Rare Earth Free Permanent Magnet Generators
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Low speed permanent magnet (PM) synchronous generators (SGs) are commonly used in renewable energy. Rare earth (RE) PMs such as neodymium-iron-boron are a popular choice due to their high performance. In 2011 supply and cost issues were added to the previously existing environmental concerns regarding REPM raw materials as the world's major producer China imposed export restrictions. This thesis aims to investigate and propose design solutions for PMSGs that do not use REPMs. Two approaches are used: to design generators using the cheaper and more abundant ferrite PM materials, and to investigate how properties of new PM materials influence SG design.

A ferrite PM rotor is designed to replace a REPM rotor in an experimental 12 kW wind power generator. The new design employs a flux concentrating spoke type rotor to achieve performance similar to the old REPM rotor while using ferrite PMs. The ferrite PM rotor design is built. The air gap length, magnetic flux density in the air gap, PM remanence, and voltage at both load and no load are measured. The generator has lower no load voltage than expected, which is mainly explained by lower than specified remanence of the ferrite PMs in the prototype. With the measured remanence inserted into the calculations some discrepancy remains. It is found that the discrepancy can be explained by the magnetic leakage flux in the end regions of the spoke type rotor, which is not modeled in the two dimensional simulations used for the design calculations.

To investigate the influence of PM material properties three different PM rotor topologies are optimized for torque production using PM materials described by their remanence, recoil permeability, and demagnetization resistance. Demagnetization is considered using currents determined by a novel, winding design independent short circuit model. It is found that the spoke type rotor gives the highest torque of the three rotor topologies for low remanence materials as long as the PMs have sufficient demagnetization resistance. For high remanence materials the surface mounted PM rotor can give higher torque if the demagnetization resistance is high, but otherwise a capped PM rotor gives higher torque.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 75
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1746
Keywords
permanent magnet generators, electrical machine design, ferrite permanent magnet
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-366344 (URN)978-91-513-0510-3 (ISBN)
Public defence
2019-01-18, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 12-295Carl Tryggers foundation , 15:152Swedish Research Council, 2012-4706
Available from: 2018-12-19 Created: 2018-11-22 Last updated: 2019-01-21

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Eklund, PetterEriksson, Sandra

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