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Magnetic bearings in kinetic energy storage systems for vehicular applications
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
2011 (Engelska)Ingår i: Journal of Electrical Systems, ISSN 1112-5209, Vol. 7, nr 2, s. 225-236Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The rotating Kinetic Energy Storage System (KESS) is suitable as temporary energy storage in electric vehicles due to its insensitivity to the number of charge-discharge cycles and its relatively high specific energy. The size and weight of the KESS for a given amount of stored energy are minimized by decreasing the moment of inertia of the rotor and increasing its speed. A small and fast rotor has the additional benefit of reducing the induced gyroscopic moments as the vehicle turns. The very high resulting rotational speed makes the magnetic bearing an essential component of the system, with the Active Magnetic Bearing (AMB) being the most common implementation. The complexity and cost of an AMB can be reduced by integration with the electric machine, resulting in a bearingless and sensorless electric machine. This review article describes the usage of magnetic bearings for FESS in vehicular applications.

Ort, förlag, år, upplaga, sidor
2011. Vol. 7, nr 2, s. 225-236
Nyckelord [en]
Magnetic bearing, FESS, flywheel, energy storage, electric vehicle
Nationell ämneskategori
Teknik och teknologier
Forskningsämne
Teknisk fysik med inriktning mot elektricitetslära
Identifikatorer
URN: urn:nbn:se:uu:diva-165038OAI: oai:DiVA.org:uu-165038DiVA, id: diva2:471417
Tillgänglig från: 2012-01-02 Skapad: 2012-01-02 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
Ingår i avhandling
1. Kinetic Energy Storage and Magnetic Bearings: for Vehicular Applications
Öppna denna publikation i ny flik eller fönster >>Kinetic Energy Storage and Magnetic Bearings: for Vehicular Applications
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

One of the main challenges in order to make electric cars competitive with gas-powered cars is in the improvement of the electric power system. Although many of the energy sources currently used in electric vehicles have sufficientlyhigh specific energy, their applicability is limited due to low specific power. It would therefore be advantageous to create a driveline with the main energy storage separated from a smaller energy buffer, designed to have high power capabilities and to withstand frequent and deep discharge cycles. It has been found that rotating kinetic energy storage in flywheels is very well suited for this type of application.

A composite shell, comprising an inner part made of glassfiber and an outer part made of carbonfiber, was analyzed analytically and numerically, designed, and constructed. The shell was fitted onto a metallic rotor using shrinkfitting. The cost of the shell, and the complexity of assembly, was reduced by winding the glass- and carbonfiber consecutively on a mandrel, and curing the complete assembly simultaneously. Thereby, the shell obtained an internal segmentation, without the need for fitting several concentric parts onto each other. The radial stress inside the composite shell was kept compressive thanks to a novel approach of using the permanent magnets of the integrated electric machine to provide radial mechanical load during rotation.

Two thrust bearing units (one upper and one lower) comprising one segmented unit with the permanent magnets in a cylindrical Halbach configuration and one non-segmented unit in a up/down configuration were optimized, constructed and tested. Each thrust bearing unit generated 1040 N of repelling force, and a positive axial stiffness of 169 N/mm at the nominal airgap of 5 mm. 

Two radial active magnetic bearings (one upper and one lower) were optimized, constructed and tested. By parameterizing the shape of the actuators, a numerical optimization of force over resistive loss from the bias currentcould be performed. The optimized shape of the electromagnets was produced by watercutting sheets of laminated steel. A maximum current stiffness of120 N/A at a bias current of 1.5 A was achieved.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2014. s. 107
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1104
Nyckelord
flywheel, magnetic bearing, energy storage, electric vehicle
Nationell ämneskategori
Elektroteknik och elektronik
Forskningsämne
Teknisk fysik med inriktning mot elektricitetslära
Identifikatorer
urn:nbn:se:uu:diva-212106 (URN)978-91-554-8825-3 (ISBN)
Disputation
2014-02-05, sal Å80101, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 08:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-01-14 Skapad: 2013-12-05 Senast uppdaterad: 2014-01-24

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Abrahamsson, JohanBernhoff, Hans

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