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Comparison between axial and radial flux PM coreless machines for flywheel energy storage
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.
2010 (English)In: Journal of Electrical Systems, ISSN 1112-5209, Vol. 6, no 2Article in journal (Refereed) Published
Abstract [en]

The need of a deeper understanding of coreless machines arises with new magnetic materials with higher remanent magnetization and the spread of high speed motors and generators. High energy density magnets allow complete ironless stator motor/generators configurations which are suitable for high speed machines and specifically in flywheel energy storage. Axial-flux and radial-flux machines are investigated and compared. The limits and merits of ironless machines are presented. An analytic solution of Maxwell’s equations is used to calculate the properties of axial-flux and radial-flux ironless generators. This method is used to investigate the influence of several parameters such as diameter and airgap width. Two machines have been calculated with FEM techniques and results are compared to validate the analytic method. Simulations conclude that end winding effects are more significant for axial-flux than for radialflux topologies. Radial-flux machines are more suitable for high speed ironless stators. The optimum values of some machine parameters are significantly different for ironless machines in comparison to slotted and slotless machines, such as outer radius to inner radius for axial-flux topologies. High speed coreless machines for energy storage and other applications required 3D FEM analysis for accurate results.

Place, publisher, year, edition, pages
2010. Vol. 6, no 2
Keyword [en]
Flux density, High-speed PM electric machine, Magnetic devices, Optimum design, Permanent Magnets Synchronous Machine (PMSM).
National Category
Engineering and Technology
URN: urn:nbn:se:uu:diva-140351OAI: oai:DiVA.org:uu-140351DiVA: diva2:383460
Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2016-04-18Bibliographically approved
In thesis
1. FEM Analysis Applied to Electric Machines for Electric Vehicles
Open this publication in new window or tab >>FEM Analysis Applied to Electric Machines for Electric Vehicles
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electric vehicle technology is an interdisciplinary field in continuous development. It appears to be a margin for improvements. The Division for Electricity at Uppsala University is doing significant research in the field. The present thesis investigates electric machines for vehicular applications, both in the driveline and in the traction motor.

Section 1 presents a driveline with two galvanically isolated voltage levels. A low power side is operated at the optimum voltage of the batteries, while a high power side is operated at a higher voltage leading to higher efficiencies in the traction motor. Both sides are coupled through a flywheel that stabilizes the power transients inherent to a drive cycle.

A review of electric machine topologies for electric vehicles is presented in Section 2. The permanent magnet excited machine is the most suitable technology for an electric driveline.

Section 3 is devoted to numerical models applied to electric machines. The equivalent circuit of a motor/generator with two sets of windings is first presented. This machine couples both sides of the driveline and drives the rotor of the flywheel. The electric parameters are calculated with custom FEM models. A discussion on slotless machines concludes with a simple model to analyze the magnetic field from one static 3D simulation. The tooth ripple losses in solid salient poles are also analyzed with a novel FEM approach. A complete description of the losses in electric machines gives a proper background for further discussion on efficiency.

Section 4 presents the experimental work constructed to validate the theoretical models. The experiments include an axial flux, single wounded prototype, an axial flux, double wound prototype and a planed radial flux coreless prototype.

Section 5 focuses on traction motors for electric vehicles. A simulated prototype illustrates a design and calculation process. The loss theory and the numerical methods presented in Section 3 are applied.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Uppsaliensis, 2011. 54 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 845
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Vehicle Engineering
urn:nbn:se:uu:diva-157879 (URN)978-91-554-8136-0 (ISBN)
Public defence
2011-10-07, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1,, Uppsala, 13:15 (English)
Available from: 2011-09-16 Created: 2011-08-24 Last updated: 2011-11-03Bibliographically approved

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