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Rare Earth Metal–Free Permanent Magnet Generators
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Wind power group)ORCID iD: 0000-0003-3341-6910
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. , 51 p.
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: urn:nbn:se:uu:diva-292963OAI: oai:DiVA.org:uu-292963DiVA: diva2:928830
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
List of papers
1. A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator
Open this publication in new window or tab >>A Complete Design of a Rare Earth Metal-Free Permanent Magnet Generator
2014 (English)In: Machines, ISSN 2075-1702Article in journal (Refereed) Published
Abstract [en]

The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage.

Place, publisher, year, edition, pages
Basel, Switzerland: Multidisciplinary Digital Publishing Institute, 2014
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-236639 (URN)10.3390/machines2020120 (DOI)
Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2016-07-07
2. Air Gap Magnetic Flux Density Variations due to Manufacturing Tolerances in a Permanent Magnet Synchronous Generator
Open this publication in new window or tab >>Air Gap Magnetic Flux Density Variations due to Manufacturing Tolerances in a Permanent Magnet Synchronous Generator
(English)Manuscript (preprint) (Other academic)
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-292962 (URN)
Funder
Swedish Research Council, 2012-4706ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 12-295
Available from: 2016-05-16 Created: 2016-05-11 Last updated: 2016-07-07
3. The Influence of PM Material Properties on Choice of Generator Magnetic Circuit Topology
Open this publication in new window or tab >>The Influence of PM Material Properties on Choice of Generator Magnetic Circuit Topology
2016 (English)Manuscript (preprint) (Other academic)
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-292965 (URN)
Funder
Swedish Research Council, 2012-4706
Available from: 2016-05-16 Created: 2016-05-11 Last updated: 2016-07-07

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