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Power flow in the air gap of linear electrical machines by utilization of the Poynting vector: Part 1 - Analytical expressions
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.ORCID iD: 0000-0001-8598-2565
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
(English)In: Journal of Engineering Mathematics, ISSN 0022-0833, E-ISSN 1573-2703Article in journal (Refereed) Submitted
Abstract [en]

Analytical solutions and estimations for the power flow in the air gap of linear electrical machines of different geometries are derived from Poynting’s theorem. The different geometries considered are flat one-sided, multi-sided, and tubular linear electrical machines. The radial power flow for all considered geometries is dependent on the area of the air gap, the electric field, the magnetic field, and the load angle. The tangential power flow for both flat one-sided and tubular linear electrical machines is dependent of the area of the air gap, number of poles, the electric field, the magnetic field, and the load angle. The number of poles could be increased to decrease the tangential power flow in flat linear electrical machines. The expression for the tangential flow in tubular linear electrical machines is so complicated that it is difficult to draw conclusions from it.

Place, publisher, year, edition, pages
Uppsala.
Keywords [en]
Poynting vector; Linear electrical machine; Wave power; Hybrid vehicles; Stirling micro-generators; Air craft launch systems; Artificial hearts
National Category
Energy Engineering Other Engineering and Technologies
Identifiers
URN: urn:nbn:se:uu:diva-382401OAI: oai:DiVA.org:uu-382401DiVA, id: diva2:1307095
Funder
Swedish Energy AgencyAvailable from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-04-26Bibliographically approved
In thesis
1. Power transfer in the air gap of linear generators for wave power
Open this publication in new window or tab >>Power transfer in the air gap of linear generators for wave power
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

An increased need for electric energy and share of renewable energy is important for a more sustainable future, to which wave power can contribute. Some concepts for wave power use linear generators, and the studies presented here focus on the power transfer and forces in the air gap of linear generators.

Based on Poynting's theorem, analytical expressions were derived for how much power is transmitted in the air gap of linear electric machines. The equations were derived for flat linear generators as well as for cylindrical linear generators, and for both the radial and the longitudinal power flows. The radial power flow contributes to the electricity that can be taken from the generator, while the longitudinal contributes to unwanted effects such as vibration. The equations show that for flat linear electric machines, vibrations and other unwanted power transmissions can be reduced by increasing the number of poles in the machine, without decreasing the desired power transfer. Otherwise, the same factors that increase the desired power transfer also increase the unwanted.

By studying the generator as a damping force and a lumped circuit, it was derived that the absorbed energy of a linear generator is quadratically dependent on the partial stator-translator overlap if the inductance of the generator is not affected by a partial overlap. Consequently, the forces in the air gap also depend quadratically on the relative overlap between the stator and the translator.

Data were collected during two experiments in order to determine whether the quadratic dependence between partial stator-translator overlap and energy transfer could be seen experimentally. Linear regression analysis of the experimental data shows that the relationship is somewhere between linear and cubic, but did not clearly show a quadratic relationship. The inductance showed no dependence of the partial stator-translator overlap.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 62
Keywords
Linear generator; Wave Power; Air gap; Poynting's theorem; Partial stator-translator overlap; Linear electrical machines
National Category
Energy Engineering Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-375101 (URN)
Presentation
2019-05-29, Å80101, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Funder
StandUp
Available from: 2019-05-13 Created: 2019-04-25 Last updated: 2019-05-13Bibliographically approved

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Temiz, IrinaEriksson, SandraLeijon, Mats

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