| 1. |
- Austrin, Lars, et al.
(author)
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A new high power density generation system
- 2006
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In: ICAS-Secretariat, 25th Congress of the International Council of the Aeronautical Sciences 2006. - 9781604232271 ; , s. 3600-3604
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Conference paper (peer-reviewed)abstract
- A trend of increased Electric Power in Aircraft stresses the need of robust, low weight systems with low losses. New hard and soft magnetic materials have made it feasible to work with high speed and high frequency. Applications of new soft magnetic materials and hard magnetic materials like NeFeB magnets have enabled high density power generation systems. A new concept comprising a high speed PM-generator system and a magnetic amplifier control is presented. Magnetic amplifiers are used in the power supply of the Electronic Flight Control System in the Swedish "Gripen" fighter-aircraft. This technology is attractive in More Electric Aircraft (MEA) systems due to the possibility to achieve a compact, robust and a highly reliable system with low losses. Applications of new soft magnetic materials, such as amorphous magnetic alloys, have enabled the use of magnetic amplifier (magamp) technology in the design of competitive electric power converters. This paper presents a studied design on a 20-40 kW generator system including a +/- 270V controlled output, performed by magnetic amplifier technology. This work addresses the power generator, and the power converter. High speed PM-generators are offering high power density. The impact of operating a generation system with higher frequency and an increasing number of poles as well as the advantages with new soft magnetic materials is studied. The iron losses and the copper losses are analyzed for the generator, and the power converter.
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| 2. |
- Austrin, L., et al.
(author)
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Evaluation of switching losses in magnetic amplifiers as an alternative to IGBT switching technologies
- 2008
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In: International Conference on Power Electronics, Machines and Drives. - : IEE. - 9780863419003 ; , s. 250-254
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Conference paper (peer-reviewed)abstract
- In future more electric aircraft (MEA) applications increased requirements of power levels stress the importance of low losses in converters and switching elements. In this work the losses of transistor switches are analysed and compared with the losses in magnetic amplifiers (Magamp) where amorphous alloy properties allows design of competitive devices. More Electric Aircraft technology can take advantage of this to accomplish compact, robust and reliable systems with low losses. Magamps are already used in the power supply of the Electronic Flight Control System in the Swedish "Gripen" fighter-aircraft. This paper presents a comparison between Magamp technology and an alternative Insulated Gate Bi-polar Transistor (IGBT) design. The study is concentrated on the power losses in a proposed 10 kW converter with ± 270 VDC (540 VDC) regulated output, where the fundamental difference between the switching elements is that the magnetic switch handles AC and the IGBT handles DC. To allow comparison, the copper and magnetic losses in the magnetic switch of the magnetic amplifier are considered as equivalent to the switching and conduction losses in the IGBT. The comparison is based on the sum of losses in power converters comprising six switching elements.
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| 3. |
- Austrin, Lars
(author)
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On magnetic amplifiers in aircraft applications
- 2007
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Licentiate thesis (other academic/artistic)abstract
- In the process of designing an electric power supply system for an aircraft, parameters like low weight and low losses are important. Reliability, robustness and low cost are other important factors. In the Saab Gripen aircraft, the design of the primary power supply of the electric flight control system was updated by exchanging a switching transistor regulator to a magnetic amplifier (magamp). By introducing a magamp design, weight was saved and a more reliable power supply system at a lower cost was achieved. In this particular case, with the power supply of the electric flight control system in the Saab Gripen fighter, advantage could be taken of a specific permanent magnet generator (PM-generator). The frequency of the generator offered the perfect conditions for a magamp controller. A key parameter in designing magnetic amplifiers (magamps) is low losses. New amorphous alloys offer new possibilities of the technique in designing magnetic amplifiers, because of their extremely low losses. The core losses are evaluated by studying the equations and diagrams specifying the power losses. The core losses are evaluated and compared with the copper losses in the process of optimizing low weight and low losses. For this an engineering tool is developed and demonstrated. Evaluations of the hysteresis characteristics for the magnetic alloys, as well as modeling and simulation of the core losses, are presented in this work. The modeling of the core losses includes hysteresis losses, eddy current losses and excess losses as well as copper losses. The losses are studied dynamically during realistic operational conditions. The model can be used for any generic analysis of hysteresis in magnetic circuits. Applications of magnetic amplifiers in aircrafts have been demonstrated to be a feasible alternative
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| 4. |
- Austrin, L., et al.
(author)
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Simulation of a magnetic amplifier circuit including hysteresis
- 2005
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Conference paper (peer-reviewed)abstract
- The purpose of this paper is to demonstrate the feasibility. of using a dynamic hysteresis model in simulating a magnetic amplifier (mag amp). The presented model includes static hysteresis, classical eddy currents, and excess losses. The proposed modeling approach is shown to be a feasible tool for designing mag amps.
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| 5. |
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| 6. |
- Castillo, Daniel, 1977-
(author)
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Statens förändrade gränser : En studie om sponsring, korruption och relationen till marknaden.
- 2009
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Doctoral thesis (other academic/artistic)abstract
- This thesis brings fresh light on the types of problems that contemporary democracies might face when interacting with private interests. More specifically, the study examines the separation between the state and private interests, based on the assumption that this separation is a precondition for maintaining democracy and legitimate governance. It is thereby a contribution towards understanding the social forces that allow private interests to penetrate the public realm, as well as the forces that protect the state from such penetration. Under which circumstances do private interests access state apparatus in ways that contradicts its universalistic principles? How does the state consider challenges against its legitimacy and how are such threats dealt with? These questions are answered by means of two case studies. The first concerns the interaction between a number of state authorities that receive sponsoring from business enterprises. The second concerns interaction - partially afflicted by corruption - between the state monopoly for selling alcoholic beverages (‘Systembolaget’) in Sweden and its private suppliers.Applying theories on organizational boundaries, exchange, trust, networks as well as legitimacy to these cases, the study demonstrates how state reforms, inspired by the logic of markets, has introduced new ways for private interest to access state affairs. In the case of ‘Systembolaget’, this is particularly evident. The possibility of access, the study argues, is a consequence of reshaping the internal boundaries of the state, broadening informal relations as well as extended scope of action for state employees. This replaced social differentiation as a mechanism of separation by the personal integrity of state employees. Interestingly, this finding should be considered in relation to how the state has attempted to sharpen its organizational boundaries through a strengthening of regulation and the businesslike relations of exchange.
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| 7. |
- Danielsson, Christer
(author)
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Analysis of Synchronous machine dynamics using a novel equivalent circuit model
- 2009
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Licentiate thesis (other academic/artistic)abstract
- This thesis investigates simulation of synchronous machines using a novel Magnetic Equivalent Circuit (MEC) model. The proposed model offers sufficient detail richness for design calculations, while still keeping the simulation time acceptably short. Different modeling methods and circuit alternatives are considered. The selected approach is a combination of several previous methods added with some new features. A detailed description of the new model is given. The flux derivative is chosen as the magnetic flow variable which enables a description with standard circuit elements. The model is implemented in dq-coordinates to reduce complexity and simulation time. A new method to reflect winding harmonics is introduced. Extensive measurements have been made to estimate the traditional dq-model parameters. These in combination with analytical calculations are used to determine the parameters for the new MEC model. The model is implemented using the Dymola simulation program. The results are evaluated by comparison with measurements and FEM simulations. Three different operation cases are investigated; synchronous operation, asynchronous start and inverter fed operation. The agreement with measurements and FEM simulations varies, but it is believed that it can be improved by more work on the parameter determination. The overall conclusion is that the MEC method is a useful approach for detailed simulation of synchronous machines. It enables proper modeling of magnetic saturation, and promises sufficiently detailed results to enable accurate loss calculations. However, the experience is that the complexity of the circuits should be kept at a reasonable low level. It is believed that the practical problems with model structure, parameter determination and the simulation itself will otherwise be difficult to master.
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| 8. |
- Danielsson, Oskar, 1975-
(author)
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Wave Energy Conversion : Linear Synchronous Permanent Magnet Generator
- 2006
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Doctoral thesis (other academic/artistic)abstract
- This thesis studies the electric aspects of a linear synchronous permanent magnet generator. The generator is designed for use in a wave energy converter, which determines the fundamental requirements of the generator. The electromagnetic properties of the generator are investigated with a finite element based simulation tool. These simulations formed the base of the design and construction of a laboratory prototype. Several experiments where conducted on the prototype generator. The results verify at large the simulation tool. However, a difference between the measured and simulated air gap flux was discovered. This was attributed to the longitudinal ends of the generator, which are ignored in the simulation tool. Experiences from the construction, and further finite element studies, led to a significant change in the support structure of the first offshore prototype generator. A complete wave energy converter was constructed and launched, the 13th of March, on the west coast of Sweden. A study of the load resistance impact on the power absorption has been carried out. An optimal load interval, with regard to power absorption, has been identified. Furthermore, the generator has proofed to withstand short term overload several times larger than the nominal load. Finally, the longitudinal ends’ influence on the flux distribution was investigated with an analytical model, as well as finite element simulations. A possible problem with large induction of eddy currents in the actuator back steel was identified.This work is a part of a larger project, which aims do develop a viable wave energy conversion system.
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| 9. |
- Daroui, Danesh, et al.
(author)
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Projekt: Kretsbaserad lösare för elektromagnetisk analys av kraftelektroniksystem- Applikation mot IGBTmoduler
- 2007
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Other publication (pop. science, debate, etc.)abstract
- Projektet syftar till att accelerera och adaptera den programvara, MultiPEEC,som ingick i ELEKTRA-projekt 36021 för att möjliggöra studier avelektromagnetiska effekter i avancerade kraftelektroniksystem.Programvaran bygger på en långsiktig forskningssatsning på Luleå tekniskauniversitet med syfte att kombinera lösningen av elektriska kretsar ochelektromagnetiska effekter i samma miljö med hjälp av en ekvivalent-kretsmetod(PEEC).I första delen av projektet verifierades, optimerades och stabiliseradesprogramvaran i ett mycket nära samarbete med ABB CRC. I den föreslagnaandra delen av projektet kommer programvaran att massivt accelereras föratt möjliggöra detaljstudier av elektromagnetiska effekter i bus bars ochIGBT moduler. För bus bars är det främst studier av parasitiska induktanseroch magnetiska fältmönster som är av intresse för att minimeraoscillationer, spänningstoppar och sk termiska hot spots. För IGBTmodulerna är det främst den dynamiska strömfördelningen i modulerna ochöver seriekopplade konfigurationer som studeras för att förbättrakommande produkter. Exakt med vilken metod den egen-utveckladeprogramvara kommer att accelereras utifrån bestäms under hösten 2010med en litteraturstudie som bas. Tänkbara metoder är QR decomposition,Fast multipole methods, wavelets, eller hierarkiska matrismetoder. Detprimära syftet är att accelerera lösningen av system beskrivna i frekvensdomänen under kvasi-statiska antaganden formulerade med hälp av enmodifierad nodanalys (MNA) då det passar för ovan nämnda designstudier.Vidare är det av stor vikt att kunna uppskatta felet som dessaaccelerationsmetoder introducerar i lösningen så verktyget inte blir praktisktoanvändbart.
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| 10. |
- Engdahl, Göran, et al.
(author)
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An approach to optimization the coil and magnetic circuit of magnetostrictive actuators
- 2006
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In: 2nd IC-SCCE.
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Conference paper (peer-reviewed)abstract
- When designing a magnetostrictive actuator with bias permanent magnets one important problem is the dimensioning of the ingoing parts in order to achieve the required power output while keeping the losses as low as possible i.e. to maximize the electromechanical efficiency. It is also of interest to use the permanent magnets efficiently. This paper presents a technique which includes FE-methods of estimating the fringing fields in the vicinity of magnetostrictive actuators. A reasonable accurately estimation of the fringing field is an important issue when dimensioning the permanent magnets and the magnetic flux path of a magnetostrictive actuator. Furthermore, we desccribe a technique to determine the coil geometry, taking into account the leakage flux in the coil, for minimum resistive losses and sufficient magnetization of the active material.
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