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FEM Analysis Applied to Electric Machines for Electric Vehicles
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
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.
Series
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
Identifiers
URN: urn:nbn:se:uu:diva-157879ISBN: 978-91-554-8136-0 (print)OAI: oai:DiVA.org:uu-157879DiVA: diva2:436792
Public defence
2011-10-07, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1,, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-09-16 Created: 2011-08-24 Last updated: 2011-11-03Bibliographically approved
List of papers
1. Design Parameters Calculation of a Novel Driveline for Electric Vehicles
Open this publication in new window or tab >>Design Parameters Calculation of a Novel Driveline for Electric Vehicles
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2009 (English)In: World Electric Vehicle Journal, ISSN 2032-6653, Vol. 3Article in journal (Refereed) Published
Abstract [en]

A driveline for electric vehicles is presented. The propulsion system is operated at a higher voltage than the primary energy source. The batteries selected as the primary energy source deliver power to the vehicle through a motor-generator wounded with two electrically isolated sets of windings, named Two Voltage Level Machine (TVLM). The dynamic behaviour of a vehicle operating according to a standard drive cycle is studied. Parameters of the driveline such as power rates and size of the flywheel are obtained by optimization. A description of the performance of a TVLM is also presented through its equivalent circuit and the control of the machine. Special attention to the system losses is presented. A scale prototype has been constructed and tested under a drive cycle, demonstrating the system performance of the system.

Keyword
Flywheel, Electric driveline, Regenerative braking, Simulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113157 (URN)ISSN 2032-6653 (ISBN)
Available from: 2010-01-25 Created: 2010-01-25 Last updated: 2016-04-14Bibliographically approved
2. Comparison between axial and radial flux PM coreless machines for flywheel energy storage
Open this publication in new window or tab >>Comparison between axial and radial flux PM coreless machines for flywheel energy storage
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.

Keyword
Flux density, High-speed PM electric machine, Magnetic devices, Optimum design, Permanent Magnets Synchronous Machine (PMSM).
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-140351 (URN)
Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2016-04-18Bibliographically approved
3. Dual voltage driveline for vehicle applications
Open this publication in new window or tab >>Dual voltage driveline for vehicle applications
2010 (English)In: International Journal of Emerging Electric Power Systems, ISSN 2194-5756, E-ISSN 1553-779X, Vol. 11, no 3, 20 pp.- p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel driveline where the load and the energy source are operated at different voltage levels and they are galvanically insulated. The element that couples both part of the driveline is a Two Voltage Level Machine (TVLM). The machine is formed of a self-excited rotor and a stator with two sets of electrically isolated windings for adjustable speed drive applications. Both sets of these three phase windings are independently operated at different voltages. The equivalent circuit of the TVLM is deduced and phasor diagrams are presented. A complete driveline is simulated and the performance of the complete system is discussed. The driveline is applicable in flywheel energy storage systems for vehicles and power conditioning in renewable energy production.

Place, publisher, year, edition, pages
USA: Berkeley Electronic Press, 2010
Keyword
drives, renewable energy sources, rotors, stators, vehicles
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-140362 (URN)10.2202/1553-779X.2384 (DOI)
Note

11478469 dual voltage driveline vehicle applications energy source two voltage level machine self-excited rotor self-excited stator power conditioning renewable energy production

Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2017-12-11Bibliographically approved
4. A Double Wound Flywheel System under Standard Drive Cycles: Simulations and Experiments
Open this publication in new window or tab >>A Double Wound Flywheel System under Standard Drive Cycles: Simulations and Experiments
2010 (English)In: International Journal of Emerging Electric Power Systems, ISSN 1553-779X, Vol. 11, no 4, Article 6.- p.Article in journal (Refereed) Published
Abstract [en]

Flywheel systems are attractive for use in electric vehicles, being able to efficiently handle the large power needed for acceleration and regenerative braking. A double wound flywheel machine, divided in two different voltage levels by the windings, acting like a rotating transformer, is studied. The flywheel stator windings have two sides: a low voltage side connected to the battery and a high voltage side connected to the wheel motor. The load variations on the high voltage side have minimal affect on the low voltage side of the system, in which the speed control of the machine is performed. In this paper the functionality of the system is investigated by means of simulations and experiments. Different standard drive cycles are applied on the high voltage side to assess the effect of load variations in the system as a whole and particularly in the speed control. The response of the speed control system is investigated with computer simulations and experimental verification. The energy storage in the flywheel allows a steady power supply from the battery via the inverter, proving the functionality of the system.

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-140340 (URN)10.2202/1553-779X.2487 (DOI)
Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2015-12-08Bibliographically approved
5. 3D FEM modeling of ironless Axial Flux Permanent Magnet motor/generators
Open this publication in new window or tab >>3D FEM modeling of ironless Axial Flux Permanent Magnet motor/generators
2011 (English)In: Journal of Electrical and Electronics Engineering, ISSN 1844-6035, Vol. 4, no 1, 53-58 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Oradea, Romania: Editura Universităţii din Oradea, 2011
Keyword
Axial Flux machine, Eddy currents, FEM
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-156738 (URN)
Available from: 2011-08-08 Created: 2011-08-08 Last updated: 2016-04-19Bibliographically approved
6. Losses in Axial-Flux Permanent-Magnet Coreless Flywheel Energy Storage Systems
Open this publication in new window or tab >>Losses in Axial-Flux Permanent-Magnet Coreless Flywheel Energy Storage Systems
Show others...
2008 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Vilamoura, Portugal: , 2008
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-113430 (URN)
Conference
18th International Conference on Electrical Machines
Available from: 2010-01-28 Created: 2010-01-28 Last updated: 2016-04-12Bibliographically approved
7. Filter influence in rotor losses in coreless axial flux permanent magnet machines
Open this publication in new window or tab >>Filter influence in rotor losses in coreless axial flux permanent magnet machines
(English)In: Journal of Electrical SystemsArticle in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-157069 (URN)
Available from: 2011-08-15 Created: 2011-08-15 Last updated: 2011-11-03Bibliographically approved
8. Tooth Ripple Losses in Solid Salient Poles Review and Generalization Method for Concentrated Windings Machines
Open this publication in new window or tab >>Tooth Ripple Losses in Solid Salient Poles Review and Generalization Method for Concentrated Windings Machines
(English)In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Refereed) Submitted
Abstract [en]

This paper presents a numerical method for rotor losses in solid salient poles calculation based on FEM. All literature available in the field refers to distributed windings with a homogeneous slot pitch. The method presented is applicable both to distributed and concentrated windings. A numerical analysis based on a concentrated winding machine is presented.

Keyword
Eddy currents, finite-element analysis (FEA), magnetic losses, synchronous machines
Identifiers
urn:nbn:se:uu:diva-157860 (URN)
Available from: 2011-08-24 Created: 2011-08-24 Last updated: 2017-12-08Bibliographically approved
9. Electrical Motor Drivelines in Commercial All Electric Vehicles: a Review
Open this publication in new window or tab >>Electrical Motor Drivelines in Commercial All Electric Vehicles: a Review
Show others...
2012 (English)In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 61, no 2, 475-484 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a critical review of the drivelines in all Electric Vehicles (EVs). The motor topologies that are the best candidates to be used in EVs are presented. The advantages and disadvantages of each electric motor type are discussed from a system perspective. A survey of the electric motors used in commercial EVs is presented. The survey shows that car manufacturers are very conservative when it comes to introducing new technologies. Most of the EV’s in the market mount a single induction or permanent magnet motor with a traditional mechanic driveline with a differential. The study illustrates that comparisons between the different motors are made difficult by the large number of parameters and the lack of a recommended test scheme. The authors propose that a standardized drive cycle is used to test and compare motors.

Keyword
Motor drives, Road vehicle electric propulsion, Road vehicle power systems, Traction motors
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-157858 (URN)10.1109/TVT.2011.2177873 (DOI)000300427400005 ()
Available from: 2012-04-19 Created: 2011-08-24 Last updated: 2017-12-08Bibliographically approved

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  • modern-language-association-8th-edition
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