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  • 1. 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.

  • 2. 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)
  • 3. Beckman, C.
    et al.
    Eklund, L.
    Karlsson, B.
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wirdemark, P.
    Verifying 3G license requirements when every dB is worth a billion2006In: Eur Space Agency Spec Publ ESA SP, 2006Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator: "Post& Telestyrelsen", PTS, granted in a "beauty contest" four licenses for operations of 3G systems. To verify the coverage and the license requirements, PTS, has developed a test procedure where the field strength of the primary Common Pilot Channel, CPICH, is measured in a drive test. Designing such a test constitutes a number of challenges mainly due to the fact that in 3G the accuracy in the measurement needs to be extremely high since even a small systematic error of ∼1dB could in Sweden have the consequence that each operator would have to build an extra +1000 sites at a staggering cost of ∼1bilion SEK! The present paper gives an overview of the considerations behind the design of the test method used for verification of the 3G licence requirements in Sweden.

  • 4.
    Beckman, Claes
    et al.
    University of Gävle.
    Eklund, Lars
    Karlsson, Bo
    Lindmark, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Wirdemark, Per
    Verifying 3G licence requirements when every dB is worth a billion2006In: First European Conference on Antennas & Propagation: EuCAP 2006 / [ed] H. Lacoste & L. Ouwehand, 2006, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In the year 2000, the Swedish Telecom regulator: “Post&Telestyrelsen”, PTS, granted in a “beauty contest” four licenses for operations of 3G systems. To verify the coverage and the license requirements, PTS, has developed a test procedure where the field strength of the primary Common Pilot Channel, CPICH, is measured in a drive test. Designing such a test constitutes a number of challenges mainly due to the fact that in 3G the accuracy in the measurement needs to be extremely high since even a small systematic error of ~1dB could in Sweden have the consequence that each operator would have to build an extra +1000 sites at a staggering cost of ~1billion SEK!

    The present paper gives an overview of the considerations behind the design of the test method used for verification of the 3G licence requirements in Sweden.

  • 5.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    A lumped element transformer model including core losses and winding impedances2007Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be tested.

    In this thesis a time-domain transformer model is presented. The model includes core losses as magnetic static hysteresis, eddy current and excess eddy current losses. Moreover, the model comprises winding losses including eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a total transformer model. This results in a detailed transformer model.

    One important result of the thesis is the possibility to simulate dynamic hysteresis including the eddy current shielding in the magnetic core material. This is achieved by using Cauer circuit combined with analytical expression for static and dynamic hysteresis. Thereby, all magnetic loss components in the material can be simulated accurately. This dynamic hysteresis model is verified through experiments showing very good agreement.

  • 6.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Electromagnetic transformer modelling including the ferromagnetic core2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    In order to design a power transformer it is important to understand its internal electromagnetic behaviour. That can be obtained by measurements on physical transformers, analytical expressions and computer simulations. One benefit with simulations is that the transformer can be studied before it is built physically and that the consequences of changing dimensions and parameters easily can be assessed.

    In this thesis a time-domain transformer model is presented. The model includes core phenomena as magnetic static hysteresis, eddy current and excess losses. Moreover, the model comprises winding phenomena as eddy currents, capacitive effects and leakage flux. The core and windings are first modelled separately and then connected together in a composite transformer model. This results in a detailed transformer model.

    One important result of the thesis is the feasibility to simulate dynamic magnetization including the inhomogeneous field distribution due to eddy currents in the magnetic core material. This is achieved by using a Cauer circuit combined with models for static and dynamic magnetization. Thereby, all magnetic loss components in the material can be simulated accurately. This composite dynamic magnetization model is verified through experiments showing very good correspondence with measurements.

    Furthermore, the composite transformer model is verified through measurements. The model is shown to yield good correspondence with measurements in normal operation and non-normal operations like no-load, inrush current and DC-magnetization.

  • 7.
    Ribbenfjärd, David
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Hysteresis modeling including asymmetric domain rotation2006Conference paper (Refereed)
    Abstract [en]

    A technique for modeling of asymmetric domain rotation in magnetic materials is proposed. This technique uses variable pinning strength to model the asymmetry. This is shown to give better agreement with measurement than a constant pinning strength.

  • 8.
    Ribbenfjärd, David
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Modeling of dynamic hysteresis with Bergqvist's lag model2006Conference paper (Refereed)
    Abstract [en]

    This work presents a dynamic hysteresis model based on Bergqvist's lag model for static hysteresis and Bertotti's model for dynamic hysteresis. This new model is used for simulation of magnetic materials. The simulation results are compared with measurements of the amorphous alloy Metglas 2605 S-2 and the transformer steel Surahammar M5. The simulated results show good agreement with the measurements.

  • 9.
    Ribbenfjärd, David
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Novel method for modelling of dynamic hysteresis2008In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 44, no 6, p. 854-857Article in journal (Refereed)
    Abstract [en]

    The dynamic hysteresis model for magnetic materials presented by Bertotti [1] uses the classical eddy current expression, where the applied field is assumed to penetrate the material homogenously. However, for this to be valid for a material exposed to a field varying with a frequency in the kilohertz range or higher, the material has to be very thin, e.g., a thin laminate, typically thinner than 0.1 mm. In this paper a novel method is presented. The idea is to combine Bertotti's model with a Cauer circuit and divide the material into a number of sections, each exhibiting different magnitude of magnetic field caused by the eddy current shielding. Furthermore, the eddy currents are modeled by "magnetic inductances" instead of the classical eddy current expression. This modelling technique yields simulation results that agree very well with measurements.

  • 10.
    Ribbenfjärd, David
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Optimization of the geometrical selection of subsections in Cauer circuit models of laminated magnetic materials at high frequencies2008In: Proceedings IEEE Conference on Electromagnetic Field Computations, 2008, p. 337-Conference paper (Refereed)
  • 11.
    Ribbenfjärd, David
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Time-domain transformer model in Dymola2006In: Proceedings of IC-SCCE, 2006Conference paper (Refereed)
  • 12.
    Ribbenfjärd, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Lindmark, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Karlsson, Bo
    Eklund, Lars
    Improved vehicle antenna system for measurement of 3G radio coverage2004In: Joint COST 273/284 Workshop on Antennas and Related System Aspects in Wireless Communications, 2004, p. 189-193Conference paper (Refereed)
  • 13.
    Ribbenfjärd, David
    et al.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Lindmark, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Karlsson, Bo
    Eklund, Lars
    Omnidirectional Vehicle Antenna for Measurement of Radio Coverage at 2 GHz2004In: IEEE Antennas and Wireless Propagation Letters, ISSN 1536-1225, Vol. 3, no 1, p. 269-272Article in journal (Refereed)
    Abstract [en]

    To accurately determine radio coverage, it is necessary to have an omnidirectional antenna pattern. Our measurement results show that this is not the case for an antenna mounted on a vehicle. We present two improved antenna solutions with an additional ground plane in the form of a disk and a corrugated cone. The peak-to-peak variation in the horizontal plane is then reduced from 5 to 2.5 dB and 1.7 dB, respectively. Although our results are limited to a medium-size vehicle and frequencies around 2 GHz, we believe that they are of interest for all measurements where high accuracy is desired.

  • 14.
    Tavakoli, Hanif
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bormann, D.
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Comparison of a simple and a detailed model of magnetic hysteresis with measurements on electric steel2008In: Symposium Electromagnetic Phenomena in Nonlinear Circuit, 2008, p. 89-90Conference paper (Refereed)
  • 15.
    Tavakoli, Hanif
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bormann, Dierk
    Ribbenfjärd, David
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Engdahl, Göran
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Comparison of a simple and a detailed model of magnetic hysteresis with measurements on electrical steel2009In: Compel, ISSN 0332-1649, Vol. 28, no 3, p. 700-710Article in journal (Refereed)
    Abstract [en]

    Purpose - For efficient magnetic field calculations in electrical machines, the hysteresis and losses in laminated electrical steel must be modeled in a simple and reliable way. The purpose of this paper is to investigate and discuss the potential of a simple complex-permeability model. Design/methodology/approach - A frequency dependent complex-permeability model as well as a more detailed model (describing hysteresis, classical eddy current effects, and excess losses separately) are compared to single-sheet measurements on laminated electrical steel. It is discussed under which circumstances the simple complex-mu model is an adequate substitute for the more detailed model. Findings - A satisfactory agreement of the simple complex-mu model was found with both detailed model and measurements, improving with increasing frequencies. This is true not only for the effective permeability function, but holds also for the detailed H-B characteristics (hysteresis). Originality/value - It is demonstrated that the complex-A model is a reliable and convenient starting point for the estimation of flux distribution and losses in complicated magnetic core geometries.

1 - 15 of 15
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