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  • 1. Austrin, L.
    et al.
    Figueroa-Karlström, E.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Evaluation of switching losses in magnetic amplifiers as an alternative to IGBT switching technologies2008In: International Conference on Power Electronics, Machines and Drives, 2008, no 538 CP, p. 250-254Conference paper (Refereed)
    Abstract [en]

    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.

  • 2. Austrin, L.
    et al.
    Krah, Julius Hartwig
    KTH, Superseded Departments, Electrical Systems.
    Engdahl, Göran
    KTH, Superseded Departments, Electrical Systems.
    A modeling approach of a magnetic amplifier2004In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 272, p. E1709-E1710Article in journal (Refereed)
    Abstract [en]

    New soft magnetic materials made possible the use of the magnetic amplifier technology in designing competitive electric power supplies. This technology is used in the Swedish. fighter aircraft Gripen, being also attractive for future more electrical aircraft systems due to the possibility to achieve a compact and robust design. A modeling approach of a magnetic amplifier based on the magnetic hysteresis of the core material is presented here for a common amorphous magnetic alloy.

  • 3. Austrin, L.
    et al.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Simulation of a magnetic amplifier circuit including hysteresis2005Conference paper (Refereed)
    Abstract [en]

    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.

  • 4. Austrin, Lars
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Modeling of a Three-phase Magnetic Amplifier2004In: Proceedings of the 24th Congress of the International Council of the Aeronatical Science, Yokohama, Japan, 2004Conference paper (Refereed)
  • 5. Austrin, Lars
    et al.
    Krah, Julius
    KTH, Superseded Departments, Electrical Systems.
    Engdahl, Göran
    KTH, Superseded Departments, Electrical Systems.
    A Modeling Approach of a Magnetic Amplifier2003In: Proc. on ICM 2003 International Conference on Magnetism, Rome, Italy, 2003Conference paper (Refereed)
  • 6. Austrin, Lars
    et al.
    Torabzadeh-Tari, Mohsen
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A new high power density generation system2006In: ICAS-Secretariat, 25th Congress of the International Council of the Aeronautical Sciences 2006, 2006, p. 3600-3604Conference paper (Refereed)
    Abstract [en]

    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.

  • 7. Autrin, Lars
    et al.
    Ribbenfjärd, David
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Simulation of a mangietc amplifier circuit including hysteresis2005In: Intermag Asia 2005, 2005, p. 225-226Conference paper (Refereed)
  • 8. Benbouzid, M. E. H.
    et al.
    Reyne, G.
    Meunier, G.
    Kvarnsjo, L.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dynamic modelling of giant magnetostriction in Terfenol-D rods by the finite element method1995In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 31, p. 1821-1824Article in journal (Refereed)
    Abstract [en]

    As a contribution to the development of methods for the design and the analysis of devices based on giant magnetostrictive materials, a model for the simulation of the dynamic behaviour of the nonlinear magnetoelastic medium is presented. The coupled magnetic, magnetoelastic and mechanical equations that describe the magnetostrictive problem are solved by means of the finite element method. The thin sheets bending principle (surface splines) is used to introduce in the simulation the nonlinear properties of giant magnetostrictive materials, obtained by static characterizations

  • 9. Bergqvist, A.
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A phenomenological differential #x2010;relation #x2010;based vector hysteresis model1994In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 75, p. 5484-5486Article in journal (Refereed)
    Abstract [en]

    A phenomenological inherently vector hysteresis model employing simple differentials as a means of keeping track of the past history of the magnetic field is proposed. This results in a simple and computationally fairly efficient formulation for vector hysteresis of any dimension. An expression for determining model parameters from experimental data or from the Preisach function is given. The model exhibits rotational hysteresis and reduction of remanent magnetization by an orthogonal field and reduces to the classical Preisach model in one dimension. Details concerning the numerical implementation are discussed and computational examples demonstrating model properties are presented.

  • 10. Bergqvist, A.
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A phenomenological magnetomechanical hysteresis model1994In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 75, no 10, p. 5496-5498Article in journal (Refereed)
    Abstract [en]

    To obtain accurate design tools for applications involving giant magnetostrictive materials, magnetomechanical hysteresis effects should be taken into account. The problem consists of determining the magnetization and mechanical strain from the combined past history of magnetic field and mechanical stress. In this work, coupled magnetomechanical hysteresis has been modeled by using simple path #x2010;dependent differentials to accumulate the past history in functions related to the magnetization and strain through material #x2010;dependent parameters. By using anhysteretic curves and a few additional parameters to characterize a material, major, and minor loops with respect to both field and stress have been calculated for Terfenol #x2010;D and have shown good agreement with experiments.

  • 11. Bergqvist, A.
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A stress-dependent magnetic Preisach hysteresis model1991In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 27, p. 4796-4798Article in journal (Refereed)
    Abstract [en]

    The authors present a generalization of the classical Preisach model which handles coupled magnetic and mechanical hysteresis. Magnetostrictive materials are known to have hysteresis with respect to both magnetic field H and mechanical stress lambda;. To test the validity of the model, experiments where the two components H and lambda; have been verified in many different ways have been performed on Terfenol-D and compared to results computed from the model. Some of these results are presented. This stress-dependent model is found to have an accuracy comparable to that of the classical Preisach model

  • 12. Bergqvist, A.
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A thermodynamic representation of pseudoparticles with hysteresis1995In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 31, p. 3539-3541Article in journal (Refereed)
    Abstract [en]

    A method of expressing pseudoparticles with hysteresis within a context of irreversible thermodynamics is investigated. The state of a pseudoparticle is uniquely determined by its magnetization and its evolution is governed by entropy maximization. Hysteresis appears if the free energy is a nonconvex function of magnetization. The vectorial nature of magnetization and dependence on rate are accounted for in a systematic manner. Some basic properties are derived for quasistatic processes. In particular, it is found that in the scalar case, the magnetization is a monotonically increasing functional with respect to field and that for quasistatic processes, this implies the wiping-out property

  • 13.
    Bergqvist, A.
    et al.
    KTH.
    Engdahl, Göran
    KTH.
    Homogenization of Laminated Cores for Eddy Current Calculations1998In: The 7th JointMMM-Intermag Conference, 1998. Abstracts, 1998, p. 51-51Conference paper (Refereed)
  • 14. Bergqvist, A. J.
    et al.
    Engdahl, Göran
    KTH, Superseded Departments, Electrical Systems.
    A homogenization procedure of field quantities in laminated electric steel2001In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 37, no 5, p. 3329-3331Article in journal (Refereed)
    Abstract [en]

    A method for representing structures of laminated electric steel is investigated. The average behavior of laminates, including eddy current effects, is approximately represented using a rate-dependent constitutive law. The accuracy of the method is studied by comparing the homogenized description with finite difference calculations.

  • 15.
    Bergqvist, A.
    et al.
    KTH.
    Lundgren, A.
    KTH.
    Engdahl, Göran
    KTH.
    A Statistical Model for Domain Wall Motion Considering hysteresis1998In: The 7th Joint MMM-Intermag Conference, 1998. Abstracts, IEEE , 1998, p. 115-115Conference paper (Refereed)
  • 16. Bergqvist, A.
    et al.
    Tiberg, H.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Application of a vector Preisach model in a magnetic circuit1993In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 73, p. 5839-5841Article in journal (Refereed)
    Abstract [en]

    Magnetic hysteresis effects have been included in a finite #x2010;element description of a magnetic circuit by using the classical vector Preisach model for the constitutive relation between H and B. The influence of an external electric circuit is taken into account by adding equations derived from Faraday #x2019;s law. Computational results are presented for a magnetic circuit used in a magnetostrictive device.

  • 17. Bergqvist, Anders
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A model for Magnetomechanical Hysteresis and Losses in Magnetostrictive Materials1996In: J. Appl. Phys., Vol. 79, no 8Article in journal (Refereed)
  • 18. Bergqvist, Anders
    et al.
    Lundgren, Anders
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Experimental testing of an anisotropic vector hysteresis model1997In: IEEE Transactions on Magnetics, Vol. 33, no 5, p. 4152-54Article in journal (Refereed)
  • 19. Bergqvist, Anders
    et al.
    Lundgren, Anders
    Stillesjö, Fredrik
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Statistical modelling of magnetic and magnetostrictive properties due to domain wall motion1999In: Journal of Applied Physics, p. 5190-5192Article in journal (Refereed)
  • 20. Bergqvist, J.
    et al.
    Lundgren, A.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Computationally efficient vector hysterisis model using flux density as known variable1998In: Non-linear electromagnetic systems, p. 463-Article in journal (Refereed)
  • 21.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Comparison of two Ultra-fast actuator concepts2012In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 48, no 11, p. 3315-3318Article in journal (Refereed)
    Abstract [en]

    In this paper, two different types of ultra-fast electromechanical actuators are compared using a multi-physical finite element simulation model that has been experimentally validated. They are equipped with a single-sided Thomson coil (TC) and a double-sided drive coil (DSC), respectively. The former consists of a spirally-wound flat coil with a copper armature on top, while the latter consists of two mirrored spiral coils that are connected in series. Initially, the geometry and construction of each of the actuating schemes are discussed. Subsequently, the theory behind the two force generation principles are described. Furthermore, the current, magnetic flux densities, accelerations, and induced stresses are analyzed. Moreover, mechanical loadability simulations are performed to study the impact on the requirements of the charging unit, the sensitivity of the parameters, and evaluate the degree of influence on the performance of both drives. Finally, it is confirmed that although the DSC is mechanically more complex, it has a greater efficiency than that of the TC.

  • 22.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Electric to Mechanical Energy Conversion of Linear Ultra-Fast Electro-Mechanical Actuators Based on Stroke Requirements2014In: Electrical Machines (ICEM), 2014 International Conference on, IEEE conference proceedings, 2014, p. -515Conference paper (Refereed)
    Abstract [en]

    The operational efficiency of ultra fast actuators usedas drives in high voltage direct current breakers are at best5 %. To boost their efficiency, the design of the energizing circuitis crucial. A multi-physics finite element method (FEM) modelcoupled with a SPICE circuit model that is able to predict theperformance of the actuator with an accuracy of at least 95 % hasbeen developed and verified experimentally. Several variants ofprototypes and models have been simulated, built, and tested.It was shown that one of the main problems leading to lowefficiencies is the stroke of the drive. However, there is a possibilityto increase the efficiency of the electric to mechanical energyconversion process of the studied Thomson (TC) and double sidedcoils (DSC) to a maximum of 54 % and 88 % respectively iftheir stroke is minimized. This can be done at the expense ofincreasing the complexity and the cost of the contact system bydesigning a switch with several series connected contacts that isencapsulated in a medium with a high dielectric strength. Anotherproposed solution is to design a current pulse with a rise timethat is considerably shorter than the mechanical response time ofthe system. Parametric variations of capacitances and chargingvoltages show that the TC and the DSC can achieve efficienciesup to 15 % and 23 % respectively. Regardless of the chosenmethod, the DSC has a superior efficiency compared to a TC.

  • 23.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Electric to Mechanical Energy Conversion of Linear Ultrafast Electromechanical Actuators Based on Stroke Requirements2015In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 51, no 4, p. 3059-3067Article in journal (Refereed)
    Abstract [en]

    The operational efficiency of ultrafast actuators used as drives in high-voltage direct-current breakers is at best 5%. To boost their efficiency, the design of the energizing circuit is crucial. A multiphysics finite-element method model coupled with a SPICE circuit model that is able to predict the performance of the actuator with an accuracy of at least 95% has been developed and verified experimentally. Several variants of prototypes and models have been simulated, built, and tested. It was shown that one of the main problems leading to low efficiencies is the stroke of the drive. However, there is a possibility to increase the efficiency of the electric to mechanical energy conversion process of the studied Thomson coil (TC) and double-sided coil (DSC) to a maximum of 54% and 88%, respectively, if their stroke is minimized. These efficiencies are idealistic, and these were obtained with clamped armature studies. The efficiency of the actuator can be increased at the expense of increasing the complexity and the cost of the contact system by designing a switch with several series-connected contacts that is encapsulated in a medium with a high dielectric strength. Another proposed solution is to design a current pulse with a rise time that is considerably shorter than the mechanical response time of the system. Parametric variations of capacitances and charging voltages show that the TC and the DSC can achieve efficiencies up to 15% and 23%, respectively. Regardless of the chosen method, the DSC has a superior efficiency compared to a TC.

  • 24.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Optimal Energizing Source Design for Ultra-Fast Actuators2013Conference paper (Refereed)
    Abstract [en]

    One of the key enabling technologies for multi-terminal HVDCgrids is the existence of a breaker that can operate withina few milliseconds. A lot of research has been done to builddifferent ultra-fast drives to actuate the electric contacts ofthese breakers. What they all have in common is an operationalefficiency of at best 5 %. Capacitor banks are discharged throughspirally shaped flat coils to generate ultra-fast repulsive forces. Tooptimize the efficiency of the drive, the design of the energizingcircuit is crucial. The aim of this paper is to optimize theenergizing source and provide a deep explanation of the effectof the chosen capacitance and charging voltage for two actuatorconcepts, the Thomson coil (TC) and the double sided coil (DSC)for different stroke requirements. An experimentally validatedmulti-physics finite element method (FEM) simulation model is applied.

  • 25.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Salinas, Ener
    ABB AB Corporate Research, Sweden.
    Loadability and scaling aspects of Thomson based ultra-fast actuators2012In: Actuator 2012, 2012Conference paper (Refereed)
    Abstract [en]

    In this paper, an ultra-fast single-sided Thomson based actuator is studied. The actuator is comprised of a flat spiral-shaped coil with a conductive armature in its proximity. This armature is mechanically loaded with a uniform mass distribution over its cross section. The energizing source consists of a capacitor bank that is discharged through the actuator coil resulting in a high magnetic pressure within fractions of a millisecond. The coil is dimensioned to withstand the temperature rise.

    An experimentally validated multi-physical finite element model is used to perform simulations by varying the mechanical load to explore the performance of the actuator topology. The obtained currents, induced forces, stresses, and accelerations of the armature are then analyzed in an attempt to develop scaling techniques that can predict for example velocity and efficiency. Finally, the results of the scaling techniques are presented and compared to each other.

  • 26.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. ABB AB Corporate Research, Sweden.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. ABB AB Corporate Research, Sweden.
    Salinas, Ener
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Multiphysics modeling and experimental verification of ultra-fast electro-mechanical actuators2015In: International journal of applied electromagnetics and mechanics, ISSN 1383-5416, E-ISSN 1875-8800, Vol. 49, no 1, p. 51-59Article in journal (Refereed)
    Abstract [en]

    In this paper, a multi-physics computational tool has been developed to accurately model and build high performance ultra-fast actuators. The research methodology is based on a finite element method model coupled with a circuit model. Electromagnetic, thermal, mechanical, and algebraic equations are implemented in Comsol Multiphysics and verified with laboratory experiments of a built prototype. A simplified model is preferred as long as its underlying assumptions hold. However, in the presence of large current and force densities, nonlinearities such as deformations may occur. Such phenomena can only be captured by the use of the developed comprehensive multi-physics simulation model. Although this model is computationally demanding, it was shown to have an accuracy of at least 95% when compared with experiments.

  • 27.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Salinas, Ener
    ABB AB Corporate Research, Sweden.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    On the Design of Ultra-Fast Electromechanical Actuators: A Comprehensive Multi-Physical Simulation Model2012In: Sixth International Conference on Electromagnetic Field Problems and Applications (ICEF), 2012, IEEE conference proceedings, 2012, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In this paper, a simulation of an ultra-fast electromechanical drive was performed by using a two-dimensional axi-symmetric multi-physical finite element model. The aim of this paper is to primarily show that the following model can be used to simulate and design those actuators with good accuracy, secondly, to study the behavior and sensitivity of the system and thirdly, to demonstrate the potential of the model for industrial applications. The simulation model is coupled to a circuit and solves for the electro-magnetic, thermal, and mechanical dynamics utilizing a moving mesh. The actuator under study is composed of a spiral-shaped coil and a disk-shaped 3mm thick copper armature on top. Two numerical studies of such an actuator powered by 2640 J capacitor banks were performed. It is shown that forces up to 38 kN can be achieved in the range of 200 μs. To add credibility, a benchmark prototype was built to validate this experimentally with the use of a high speed camera and image motion analysis.

  • 28.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. ABB Corporate Research.
    Salinas, E.
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    On the design of a linear composite magnetic damper2015In: 2015 IEEE International Magnetics Conference, INTERMAG 2015, IEEE conference proceedings, 2015Conference paper (Refereed)
    Abstract [en]

    In recent years, ultra-fast actuators have become key elements in the development of high voltage direct current (HVDC) breakers for multiterminal grids which represent a huge progress in modern power transmission [1]. After fulfilling their operation these actuators need to be decelerated using controllable forces to avoid deforming vital components incorporated in the system. In this paper, a dedicated damper is proposed based on a magnet array that induces eddy currents in a composite metal tube resulting in an efficient braking response. Several topologies are investigated by simulations and experiments. The theory behind eddy current damping is explained in [2]. The main requirements for such dampers are reliability, robustness, and ease of construction. The expected durability of these kind of dampers is longer than the breaker itself which guarantees extremely good reliability within HVDC systems.

  • 29.
    Bissal, Ara
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Salinas, Ener
    Magnusson, Jesper
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    On the Design of a Linear Composite Magnetic Damper2015In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 51, no 11, article id 8003305Article in journal (Refereed)
    Abstract [en]

    High-voltage direct current (HVdc) breakers are the key components in the realization of multiterminal HVdc grids. In the presence of fault current, these breakers should be able to deliver impulsive forces to swiftly open the metallic contacts. After the acceleration phase, the moving armature should be decelerated using controllable forces to avoid plastically deforming fragile components integrated in the system. In this paper, finite-element method-based simulation models, complimented with small-scale and large-scale experimental prototypes, were utilized to benchmark different damping topologies. It was found that a Halbach-based configuration can deliver a damping force that is almost two and a half times larger than its sequel. Its sequel, composed of vertically stacked oppositely oriented magnets, is easier to assemble and is also capable of generating a considerable damping force. Finally, it has been shown that both these schemes, inserted in a composite tube, have a potential to be used as dampers in HVdc breakers.

  • 30. Bjurman, U.
    et al.
    Engdahl, Göran
    KTH, Superseded Departments, Electrical Systems.
    Separation of high and low frequency behavior in non-linear circuit simulation, excited with modulated signals2000In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 36, no 4, p. 968-970Article in journal (Refereed)
    Abstract [en]

    Exciting nonlinear circuits with modulated signals will generate crossmodulation frequencies. In ordinary simulation techniques this makes time stepping methods a necessity, In the case of EMC-testing where the carrier frequency is as high as 2 GHz and the modulating frequency only 1 kHz, the simulation time will be extremely long. This paper presents Time Domain Frequency Separation (TDFS), a method,where the high and low frequency behavior is calculated separately to decrease the computation time. In a simulation made with Saber the calculation took approximately fourteen hours, and with TDFS in Matlab two minutes.

  • 31. Bjurman, Ulf
    et al.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Separation of high and low frequency behavior in non linear circuit simulation excited with modulated signals1999In: Proc of the 12:th Conference on Computation of Electromagnetic Fields, Sapporo Japan, 1999, p. 260-61Conference paper (Refereed)
  • 32.
    Carrander, Claes
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A semi-empirical approximation of static hysteresis for high flux densities in highly grain-oriented silicon iron2017In: 8th Joint European Magnetic Symposia (JEMS2016), Institute of Physics (IOP), 2017, article id UNSP 012039Conference paper (Refereed)
    Abstract [en]

    In calculations and simulations regarding magnetic materials, it is important to have a have an accurate model of the hysteresis loop. The major loop, in particular, is used in many simulations. However, it is generally not possible to measure the true major loop, and it must therefore be approximated using a minor loop. There are several methods available for approximating magnetization curves, but they are primarily designed for paramagnetic materials, and are poorly suited to the highly grain-oriented steels used in modern transformers. Therefore, we propose two expressions for approximating the magnetization curves of grain-oriented silicon-iron steels. Both methods give close agreement with measurements and can be extrapolated to in order to describe the major loop.

  • 33.
    Carrander, Claes
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Magnetizing current measurements on full scale power transformers2015In: International journal of applied electromagnetics and mechanics, ISSN 1383-5416, E-ISSN 1875-8800, Vol. 48, no 2-3, p. 159-162Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of a power transformer core are generally held to be quite similar to those of the core steel itself. Due mainly to it being rare and practically difficult to acquire a transformer for testing and verification, testing of large units is usually only performed concerning no-load losses. However, other parts of the magnetic hysteresis loop are more sensitive to variations in material and geometry and could be used for more detailed diagnostics. This paper shows that measurements of magnetic hysteresis can be performed with good results on large power transformers. Methods to compensate for capacitive currents and to calculate the effective magnetic length of the core are shown and the results are compared to standard material measurements. The results show good agreement with Epstein frame measurements on annealed samples.

  • 34.
    Carrander, Claes
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Mousavi, Seyedali
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES).
    An application of the time-step topological model for three-phase transformer no-load current calculation considering hysteresis2017In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 423, p. 241-244Article in journal (Refereed)
    Abstract [en]

    In many transformer applications, it is necessary to have a core magnetization model that takes into account both magnetic and electrical effects. This becomes particularly important in three-phase transformers, where the zero-sequence impedance is generally high, and therefore affects the magnetization very strongly. In this paper, we demonstrate a time-step topological simulation method that uses a lumped-element approach to accurately model both the electrical and magnetic circuits. The simulation method is independent of the used hysteresis model. In this paper, a hysteresis model based on the first-order reversal-curve has been used. © 2016 Elsevier B.V.

  • 35.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Design of Magnetostrictive Devices Using Dynamic Simulation1989In: Proc. Second Int. Conf. on Giant Magnetostrictive and Amporphous Alloys for Actuators and Sensors, Marbella, Spain, 1989, 1989Conference paper (Refereed)
  • 36.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Design Procedures for Optimal Use od Giant Magnetostrictive Materials in Magnetostrictive Actuator applications2002In: Proceedings of the 8th International Conference on New Actuators, ACTUATOR 2002, Bremen, Germany, 2002, p. 554-557Conference paper (Refereed)
  • 37.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Dynamic Simulation of Terfenol Rods under Transient Magnetization1989In: Proc. First Int. Conf. on Giant Magnetostrictive Alloys and their Impact on Actuator and Sensor Technology, Marbella, Spain, 1989, 1989Conference paper (Refereed)
  • 38.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Flextensional Transducers Based on Terfenol-D1992In: International Symposium on Giant Magnetostrictive Materials and their Applications, November 5-6, 1992, Tokyo, Japan, 1992Conference paper (Refereed)
  • 39.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Handbook of Giant Magnetostrictive Materials1999Book (Other academic)
  • 40.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Modelling of Highly Magnetostrictive Materials1992In: International Symposium on Giant Magnetostrictive Materials and their Applications, November 5-6, 1992, Tokyo, Japan, 1992Conference paper (Refereed)
  • 41.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Multidisciplinary Modelling of Actuators Based on Magnetostriction2002In: Proceedings of 2nd IFAC Conference on Mechatronic Systems , Berkeley, California, USA, Edited by M. Tomizuka, 2002Conference paper (Refereed)
  • 42.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bergqvist, A.
    Lundberg, A.
    Measurements and modelling of 2-D magntization and magnetoelasticity in silicon iron1998In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177Article in journal (Refereed)
  • 43.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bergqvist, A.
    Lundgren, A.
    Stillesjö, F.
    Statistical modeling of magnetic and magnetostrictive properties due to domain wall motion1999In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, ISSN 0021-8979, Vol. 85, no 8, p. 5190-5192Article in journal (Refereed)
    Abstract [en]

    Statistical mechanics is employed to derive magnetic and magnetostrictive bulk properties of soft magnetic materials dominated by domain wall motion. The material is divided into an ensemble of volumes with uniform magnetization, each one much smaller than a typical domain but much larger than one atom. The energy for such a volume element is assumed to consist of an internal energy: the interaction with the external magnetic field and a mean field interaction with the surrounding medium. The volume fractions of discrete mesoscopic magnetizations in the medium are derived from Boltzmann statistics. The bulk magnetization is the weighted average of the mesoscopic values. Magnetostriction is treated in a similar way. Calculations are compared with two-dimensional measurements on grain-oriented silicon #x2013;iron. #xa9; 1999 American Institute of Physics.

  • 44.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bergqvist, Anders
    Loss Simulations in Magnetostrictive Actuators1996In: J. Appl. Phys., Vol. 79, no 8Article in journal (Refereed)
  • 45.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Blomberg, Lars
    Brunsell, Per
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Norgren, Martin
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Rosander, Staffan
    Electrotechnical modelling2011Other (Other academic)
  • 46.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Edin, Hans
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Eriksson, Roland
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hörnfeldt, Sven
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Schönborg, Niclas
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Electrotechnical Modelling and Design2011Other (Other academic)
  • 47.
    Engdahl, Göran
    et al.
    KTH, Superseded Departments, Electrical Systems.
    Krah, J. H.
    The feasibility to model a 3-leg core type medium frequency power transformer by use of a dual Cauer circuit2002In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 242, p. 1210-1213Article in journal (Refereed)
    Abstract [en]

    A model for medium frequency power transformers is suggested, The model is able to treat arbitrary topologies by use of Cauer circuits for core and windings. An implementation example is given for a 1-phase transformer with turn ratio 1:1. The model can be extended to include winding insulation materials by use of lumped capacitive and resistive circuit elements.

  • 48.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Krah, Julius
    Alternative 2D Magnetization Measurement Methods for Soft Magnetic Materials2000In: Proceedings from the 6th International Workshop on 1&2 Dimensional Magnetic Measurement and Testing, Bad Gastein, Austria., 2000Conference paper (Refereed)
  • 49.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Kvarnsjö, L.
    A Dependent Radially Resolved Simulation Model of Giant Magnetostrictive Materials1990In: Mechanical Modellings of New Electromagnetic Materials, p. 131-138Article in journal (Refereed)
  • 50.
    Engdahl, Göran
    et al.
    Power Engineering, ABB Corporate Research, Västerås.
    Lerebourg, B.
    Ecole Nationale SupCrieure d’Hydraulique et de Mkcanique de Grenoble, St Martin d’ Hères.
    Experimental study of magnetic slurries regarding magnetic properties1996In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 32, no 5, p. 5109-5111Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to assess the basic magnetic properties of a mixture composed of a commercial lubricant and soft magnetic iron particles, where the particle content is significantly higher than in conventional magnetic fluids, due to the fact that the particles verge on the sedimentation level. This so called magnetic slurry can, then, be regarded as a highly ductile magnetic conducting material for tentative use in a magnetic circuit that can change shape under operation. The high particle content results in high saturation field densities that extend the application field towards electric power engineering. This paper, therefore, focuses on properties like relative permeability, losses, the Q-factor and the efficiency for the power frequencies 50 and 400 Hz. It shows that the relative permeabilities are low (below 10). The values of the efficiency and the Q-factor decrease considerably above 0.5 T. That limits the application of the studied slurry in electric power engineering. In such applications, the powder properties must be improved

123 1 - 50 of 132
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