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  • Articles  (199)
  • Emerald  (199)
  • American Association for the Advancement of Science (AAAS)
  • American Association of Petroleum Geologists (AAPG)
  • 2020-2022
  • 1995-1999  (199)
  • Mathematics  (199)
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  • Articles  (199)
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  • 1
    Electronic Resource
    Electronic Resource
    Finite element analysis of the dynamics of a high bandwidth actuator for a hard disk drive (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 120-131 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper a prototype actuator designed for a high bandwidth servo system is modeled and analyzed using finite elements. Natural frequencies and mode shapes of frequencies below 10kHz are extracted using frequency analysis and compared with the results from an experimental model analysis. The effects of key parameters used in the analysis on the natural frequencies are investigated. The frequency response is calculated using the natural frequencies and mode shapes. The calculated frequency response is compared with experimental results. The comparison of results shows that the numerical results are accurate. From the analysis the mechanical dynamics of the actuator can be understood and characterized. The analysis of the actuator shows that dynamic analysis using finite element modeling is accurate and effective and can be applied to other mechatronic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264172
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  • 2
    Electronic Resource
    Electronic Resource
    A quasi-variational inequality for the simulation of a MODFET transistor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 175-186 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We introduce the drift-diffusion model with appropriate jump conditions at the junction of the MODFET transistor (AlGaAs/GaAs). We propose a quasi-variational inequality (QVI) model for this device. We assume that the electron density is bounded and piecewise constant. These hypotheses imply that the Poisson's equation becomes linear with respect to the electrostatic potential. The QVI model keeps a coupling with the continuity equation. Free boundaries arise in the medium AlGaAs near the Schottky-gate contact and in the high mobility medium (GaAs) under the effect of the electron affinity discontinuity at the junction. Numerical results of the QVI model show their location versus the applied gate voltage V/up〉 and the molar fraction X of the AlXGa(1-X)As medium. The inequality seems to be a reasonable simplification of the non-linear Poisson's equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264181
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  • 3
    Electronic Resource
    Electronic Resource
    Noninvasive cardiac source imaging from potential and magnetic field data (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 236-249 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Ventricular surface activation time maps are estimated from simulated and measured body surface potential (BSP) maps and extra-corporal magnetic field maps. In a first step the transfer matrix, relating the primary cardiac sources to the measured potential and/or magnetic field data, is calculated applying the boundary element method. Activation times are determined by minimizing a cost function which is based on this transfer matrix. This optimization method is solved by a quasi Newton method. The critical point theorem is used in order to estimate the starting column matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274757
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  • 4
    Electronic Resource
    Electronic Resource
    STEP standard's evaluation for modeling in electromagnetism (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 311-323 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The new set of standards ISO 10303 "STEP" makes it possible to give a complete representation of a product, using the description language EXPRESS. A part of STEP is devoted to the finite element analysis. This paper presents a brief overview of the architecture and the methodology of STEP and EXPRESS, with special attention to the part concerning the finite element analysis. The possibility to use it in modelling electromagnetic phenomena will be discussed. An example showing the description of a typical problem in electromagnetism will be implemented using EXPRESS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274883
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  • 5
    Electronic Resource
    Electronic Resource
    B-H characteristic extraction using devices with non-uniform field (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 469-482 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper describes an efficient method to extract the B-H nonlinear characteristic from the experimental flux-current F-I data obtained using a non-uniform magnetic field device. Both functions are monotonically piecewise linear approximated with the same number of breakpoints. The method was successfully applied to characterize the ribbon core material of a fluxset magnetic field sector. In this case the hysteresis loop and the lumped magnetic circuit were extracted. Comparison with experimental results validates the proposed method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275116
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  • 6
    Electronic Resource
    Electronic Resource
    Implementation of a hybrid method for eddy current problems (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 398-409 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper, a hybrid formulation for solving time harmonic eddy current problems in terms of magnetic field h is considered. In particular, we discuss some properties of the implicit boundary condition on the discrete level and the computation of the integral operator exploited in this context. An iterative technique is confirmed to be efficient in solving the arising, partly dense, complex linear system of equations. Furthermore, some test results, including timings for linear solvers are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274955
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical calibration of fluxset probe for quantitative eddy current testing (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 436-444 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Fluxset type eddy current probes are used for detecting discontinuities in conducting materials. The measurements obtained by such probes can be used for the reconstruction of the parameters of the detected discontinuity if the output signal of the measurement is uniquely related to the measured field. In this paper a calibration method is presented for the establishment of the relation between the measured magnetic field and the output signal of the probe. The relation is obtained by the optimisation of the parameters of the mapping between the calculated magnetic field distribution and the measured output signal. The magnetic field distribution due to the interaction of the probe and an infinitesimally thin crack located in a conducting plate is calculated numerically by the solution of a boundary integral equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275044
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  • 8
    Electronic Resource
    Electronic Resource
    Anisotropic vector Preisach model and magnetic field solutions (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 458-468 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The implementation of a vector Preisach model for the modelling of anisotropic hysteretic soft magnetic materials is outlined. Some comparisons with measurements on alternate and rotational magnetic field excitations are shown. The hysteresis model is inserted inside a two-dimensional finite element solver formulated in terms of magnetic vector potential and nonlinear solution is handled by means of the fixed point method with H-scheme. Results obtained on a two-dimensional geometry are described and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275107
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of 3-D eddy currents in conducting laminations by an anisotropic conductivity and a 1-D analytical model (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 494-503 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: To circumvent the high computational costs of modelling each lamination to compute the eddy current distribution in three dimensions in conducting laminations, a simple method has been developed. The laminar nature of the eddy currents due to the magnetic leakage field has been considered by applying an anisotropic conductivity with zero or very low value in the direction normal to the laminations. This yields an overall field distribution serving as basis. In a second step, the much smaller eddy current loops caused by the main magnetic flux parallel to the laminations have been taken into consideration by a one-dimensional analytical model. Nonlinearity is neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275170
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  • 10
    Electronic Resource
    Electronic Resource
    Numerical modelling of electrodynamic loudspeakers (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 504-514 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A new method for the numerical computation of the dynamic behaviour of electro-dynamic loudspeakers is presented. The numerical scheme, based on the finite element method (FEM), allows the simulation of coupled magnetic, mechanical and acoustic fields. The obtained simulation results are in good agreement with measured data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275189
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  • 11
    Electronic Resource
    Electronic Resource
    Identification of 1-D magnetic field profiles in high current plasmas (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 275-284 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The identification of magnetic field profiles is crucial in many applications where a direct measurement is difficult. We discuss here a technique, based on the injection of charged particles in the region under examination, which promises to be an innovative and effective tool in the analysis of 1-D field profiles in high current plasma discharges. After the decription of the inverse problem related to the field construction, we consider a suitable discrete identification scheme, and analyze some properties of the latter. The field map in the interest region is reconstructed via a minimization procedure, which identifies the coefficient of a well-suited expansion for the field. In particular, we discuss the precision and robustness of the identification procedure, with respect to the chosen optimization scheme, the amount of data, the order in the field expansion, and the influence of noise on the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274829
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  • 12
    Electronic Resource
    Electronic Resource
    Comparison of quasi minimal residual and bi-conjugate gradient iterative methods to solve complex symmetric systems arising from time-harmonic magnetic simulations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 298-310 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Finite element discretizations of low-frequency, time-harmonic magnetic problems lead to sparse, complex symmetric systems of linear equations. The question arises which Krylov subspace methods are appropriate to solve such systems. The quasi minimal residual method combines a constant amount of work and storage per iteration step with a smooth convergence history. These advantages are obtained by building a quasi minimal residual approach on top of a Lanczos process to construct the search space. Solving the complex systems by transforming them to equivalent real ones of double dimension has to be avoided as such real systems have spectra that are less favourable for the convergence of Krylov-based methods. Numerical experiments are performed on electromagnetic engineering problems to compare the quasi minimal residual method to the bi-conjugate gradient method and the generalized minimal residual method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274874
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  • 13
    Electronic Resource
    Electronic Resource
    Fast analytical model of induction motor for approaching rotor eccentricity (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 570-586 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Deals with the problem of the electromagnetic torque calculation in the case of either nonuniformity of the air-gap or eccentricity of the rotor. The electromagnetic field distributions have been evaluated for drag-cup motors. An analytical model has been introduced for linear motor based on the variation method for magnetic flux density magnitudes. The total torque and its components have been evaluated for the motors chosen. The decrease of the electromagnetic torque and increase of eddy-current losses have been discussed due to either rotor circular asymmetry or its eccentricity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296582
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  • 14
    Electronic Resource
    Electronic Resource
    Bispectrum estimation using AR-modelling (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 43-60 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper we present a new autoregressive (AR) method for bispectrum estimation defined in terms of its third-moment sequence. The method is based on the segmentation of data into coupled records, and can be considered to be a modification of the "third order recursion method"(TOR). Its foundation resides in considering the data of the process at the left and the right of each record (needed for the calculation of third moment sequence) as not null and taking them as the data corresponding to the preceding and succeeding record respectively. Several simulated examples show that this method allows model parameters to be obtained with greater precision, most of all when only few data are available per record. The influence of factors such as number of data and records, model order, and added white and coloured Gaussian noise on the parameters' estimation is also considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236984
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  • 15
    Electronic Resource
    Electronic Resource
    The role of the potentials in electromagnetism (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 103-119 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: There are two conflicting views about electromagnetic phenomena. The first is based on the action between stationary and moving particles of electric charge and the second on energy distributions in electric and magnetic fields. The difference between these approaches is seen most clearly in the roles assigned to the potentials. According to the particle view the potentials convey the force from one particle to another, whereas in the field approach the potentials are system parameters related to the field energy. The article compares the two views and concludes that the particle view faces impossible difficulties because it ascribes local significance to quantities which are unobservable and conflicts with the quantum-mechanical understanding of charge as a statistical distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264136
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  • 16
    Electronic Resource
    Electronic Resource
    Application of modified FBT algorithm in induction motor series optimal design (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 165-174 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Some improvements are made for Fast Boundary Tracking algorithm according to the practice of the electric machine design in the paper. As discrete variables play a dominant role in determining the values of the objective function and the constraint functions in the motor optimal design, the algorithm is improved in the paper. From the algorithm, a software is developed and used for the optimal design of the induction motors of Y series. The results show that the algorithm is reliable and efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264145
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  • 17
    Electronic Resource
    Electronic Resource
    Selected ideas of the theory of non-linear electrical circuits (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 204-214 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper an outline of the development of methods for the analysis of non-linear circuits is presented. Non-inert and inert elements have been discerned and an inertia measure has been proposed. For this purpose, an exponential function with time constant T equal to TR, TL, or TC is formulated for an element of type R, L, or C, respectively. In circuits with the imposed cause, which varies sinusoidally in time with period Te, the following situations are distinguished and considered: Te » T; Te « T; and Te ˜ T. In the first case, the effect changes in time according to the non-linear characteristic of the element. In the second case, the respective circuit is referred to as the "quasi-linear", because for the sinusoidal cause the effect is also sinusoidal. In the third case, the hysteresis occurs and the effect is a two-valued function. The hysteresis effect occurs also in resistive elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264208
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  • 18
    Electronic Resource
    Electronic Resource
    An energy-transport model for semiconductor heterostructure devices: application to AlGaAs/GaAs MODFETs (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 61-76 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A stationary 3D energy-transport model valid for semiconductor heterostructure devices is derived from a semiclassical Boltznmann equation by the moment method. In addition to the well-known conservation equations, we obtain original interface conditions, which are essential to have a mathematically well-posed problem. An appropriate modelling of the physical parameters appearing in the system of equations is proposed for gallium arsenide. The model being written and its particularities mentioned, we present a novel numerical algorithm to solve it. The discretization of the equations is achieved by means of standard and mixed finite element methods. We apply the model and numerical algorithm to simulate a 2D AlGaAs/GaAs MODFET. Comparisons between expenrimental measurements and calculations are carried out. The influence of the modelling of the physical parameters, especially the electron mobility and the energy relaxation time, is noted. The results show the satisfactory behaviour of our model and numerical algorithm when applied to GaAs heterostructure devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236993
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  • 19
    Electronic Resource
    Electronic Resource
    Numerical investigation of a gas dynamic model for charge transport in semiconductors (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 6-37 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A mathematical gas dynamic model for semiconductor devices is numerically analysed. The well-known ballistic diode problem is taken as an example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236966
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  • 20
    Electronic Resource
    Electronic Resource
    Remark on Maxwell's divergence equations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 77-83 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The divergence equations in Maxwell's theory are Gauss law and the statement that magnetic monopoles do not exist; from this point of view these two equations are fundamental. However, from a practical point of view, it is generally believed that Maxwell's divergence equations are redundant and may be ignored provided that they are satisfied at some time t-0. It has been proved recently that this idea is not correct for boundary-initial value problems. To make mathematical arguments more accessible, we analyse here the role of the divergence equations in the framework of 2D-electromagnetism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910237000
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  • 21
    Electronic Resource
    Electronic Resource
    Estimating unique solutions of DC transistor circuits (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 132-142 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: For each natural n let Fn denote the collection of mappings of Rn onto itself defined by: F ?Fn if and only if there exist n strictly monotone increasing functions fk mapping R onto itself such that for each x =[x1, ..., xn]T ? Rn, F(x) = [f1(x1), ..., fn(xn)]T. The following new property of the class P0 of matices is proved: a real n × n matrix A belongs to P0 if and only if for every G, H ? Fn the set S0 = { x ? Rn : - G(x) =Ax = - H(x) } is bounded. As an illustration of this property a method of estimating the unique solution of the nonlinear equation F(x) + A(x) =b describing the large class of DC transistor circuits is developed. This can improve the efficiency of known computation algorithms. Numerical examples of transistor circuits illustrate in detail how the method works in practice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264163
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  • 22
    Electronic Resource
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    Modelling and computer simulation study of laser-plasma interaction in semiconductor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 187-203 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Computer simulations were done extensively in order to study non-linear dynamics of laser-plasma interaction in InSb semiconductor. We constructed the modified Duffing kind of non-linear semiconductor plasma oscillator equation. Collision frequency is found to be dominant parameter to influence the bifurcation, chaos, hysteresis and bistable effects of plasma wave. Small windows of higher period cascade above the critical value of laser parameter (a1a2) in the chaos region are observed. Laser-plasma exhibits too much chaotic regime at lower value of laser driving frequency (d). Hysteresis and bistable regions of plasma wave are presented and the conditions for their occurence are identified. The unstable regions completely merge at higher value of effective collision frequency (?).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910264190
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  • 23
    Electronic Resource
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    BEM-computation of antenna near field reactions on conducting materials using curvilinear edge elements (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 348-360 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A boundary element method in terms of the field variables is applied to three-dimensional electromagnetic scattering problems. Especially, the influence of a dipole excited field on low conducting materials situated very close to the antenna will be discussed. We use higher order edge elements of quadilateral shape for the field approximation on curved surfaces. The tangential components of the unknown field variables are interpolated by vector element functions. The Galerkin method is implemented to obtain a set of linear equations. The applicability of the proposed edge element is investigated by the comparison of different BEM-formulations and FEM-results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910274919
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  • 24
    Electronic Resource
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    Capacitive effect models for a magnetic field sensor (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 515-527 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents an efficient modeling technique for the fluxset magnetic field sensor. Using separate numerical solutions for the electric and magnetic fields, an equivalent SPICE circuit is extracted in the postprocessing phase. The main contribution of the paper is the technique used to model the distributed capacitive effects in insulation between coils, by concentrating them in an "Extended II scheme", an infinite circuit which is optimally reduced to a finite one. The results are in qualitative agreement with the experimental ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910275206
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  • 25
    Electronic Resource
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    Dynamic operation of an electromagnetic actuator taking nonlinearity and eddy currents into account (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 611-622 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper deals with a coupled field-circuit simulation of transient and dynamic states in a non-linear axisymmetrical electromagnetic device. The mathematical model of the dynamic phenomena includes: an equation of transient electromagnetic field in a non-linear conducting and moving medium, equations of the converter electric circuits and the equation of mechanical motion. The numerical implementation of the algorithm is based on the finite element method. The Crank-Nicholson scheme for time discretization has been applied. In order to include nonlinearity, the Newton-Raphson process has been adopted. The influence of the saturation effect on the dynamic characteristics of the device has been investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910296645
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  • 26
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    An approach via the central limit theorem to randomization of Fourier's transform (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 38-42 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: By using the central limit theorem, it is possible to consider the Fourier's transform of a stochastic process with independent increments as a Gaussian random variable of which the mathematical expectation and the variance are respectively integrals of the mean and the variance of this process. One can then use this result to analyze the statistical properties of linear feedback systems in the frequency domain, that is to say in terms of transfer functions. The advantage of this approach is that one can deal with linear systems subject to squared white noises, in a very simple manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649910236975
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  • 27
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    Reduced-order method for dielectric resonators using FEM and CFH (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 84-94 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper describes an efficient reduced-order method for the analysis of cylindrical dielectric resonators with an inhomogeneous dielectric medium. The field equations are formulated using the Laplace-domain finite element method and are reduced to lower-order models using the complex frequency hopping (CFH) technique. CFH is a moment matching technique which has been used successfully in the circuit simulation area for the solution of a large set of ordinary differential equations. The proposed technique is faster than the conventional approach by one to three orders of magnitude. The results are compared with those of other numerical methods available in the literature.
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    Quasi-variational inequality and shape optimization for solution of a free boundary problem (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 143-164 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Electrical potentials in a junction field transistor can be calculated using a simplified model based on a complete depletion assumption. This gives rise to a free boundary problem. We show here how we can approximate this problem with a quasi-variational inequality technique and the shape optimization method. A detailed analysis of these methods is presented. Using some numerical experiments we compare our results with the solution of the discrete drift-diffusion system, accomplished with a Gummel-like algorithm. The numerical results suggest that the methods proposed here work successfully and that the shape optimization technique provides a reasonably free boundary without excessive iterations.
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    URL: http://dx.doi.org/10.1108/03321649910264154
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    Highly non-linear field diffusion in HTC superconducting tapes (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 215-224 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents an extension to previous work on modelling AC losses in high-temperature superconducting tapes as a highly non-linear diffusion process. Following successful formulation for a bulk superconductor the presence of silver in a tape has now been included, using a "sandwich" model, to represent more realistically the practical arrangement. The results of the extended 1-D model are included and a new 2-D scheme is described using finite difference formulation. Effects of non-linearity are emphasised.
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    Computation of magnetostatic field using second order edge elements in 3D (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 361-371 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Several second order edge elements have been applied to solving magnetostatic problems. The performances of these elements are compared through an example of magnetic circuit. In order to ensure the compatibility of the system equations and hence the convergence, the current density is represented by the curl of a source field. This avoids an explicit gauge condition which is cumbersome in the case of high order elements.
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    Non destructive evaluation in the time domain (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 422-435 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper a method is presented for an efficient solution of the direct problem (find the scattered field for a given thin crack and driving field) in the time domain. This is a fundamental step in any non destructive evaluation problem. Two different approaches, one in the time domain and the other based on Fourier analysis, are used and compared with reference to a configuration for which some experimental results are available. The advantages and drawbacks of the two approaches are briefly discussed.
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    The optimisation of electromagnetic devices using niching genetic algorithms (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 285-297 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The use of niching genetic algorithms can provide a method of a more widespread search of the design space for a device than more conventional methods. It provides, in effect, a breadth first rather than a depth first search. Thus several alternative designs may be evaluated in parallel.
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    Some considerations about the perfectly matched layer for static fields (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 337-347 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper discusses the perfectly matched layer method recently proposed for the computation of static or quasistatic fields in open boundaries. In particular it is shown how the method can be derived by means of a particular co-ordinate transformation applied to a finite-size isotropic domain surrounding the system of interest. The method is therefore equivalent to a trivial truncation from the point of view of both accuracy and computing time.
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    Contribution to the finite element analysis of eddy-currents in multi-conductor windings surrounded by magnetically non-linear media (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 668-674 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the finite element analysis of electrical machines the multi-conductor winding in a stator slot is usually modeled simply by a single conductor with constant current density. The size of a finite element problem due to the precise modeling of eddy currents in the multi-conductor windings can be much larger compared to the single conductor model. The paper investigates a new FEM approach for the consideration of eddy-currents in multi-conductor windings surrounded by nonlinear media, a case typical in electrical machinery. The method, called elimination of inner nodes, is evaluated in the paper as a possible solution for multi conductor eddy current problems. The paper presents examples and concludes in what circumstances the method of elimination is efficient.
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    Voltage ranking using artificial neural network (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 587-599 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Voltage ranking attempts to rank busbar voltage deviations from their normally accepted security margins based on a set of performance indices (PI), without performing a full load flow. Existing methods suffer from either masking effects or long computation time. In this paper, an artificial neural network method is proposed for voltage ranking. Counterpropagation network (CPN) has been employed to overcome the problems listed above. A variety of input features are used with the aim of lowering the dimension of the proposed ANN to make it applicable for large power systems. The method is tested on two example systems, a five-bus system and a 71-bus system with very encouraging results.
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    Optimizing ferromagnetic characteristics to reduce Newton iterations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 629-637 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The standard Newton iteration scheme to solve a non-linear system of equations obtained from the finite element methods is based on the updating of the field dependent element reluctivity. Usually, the manufacturer of the ferromagnetic material provides a BH-characteristic as diagram or in the form of a table of data samples. The influence of the material properties, in particular their accurate numerical representation, is significant for the rate of convergence during the Newton iterations. Here, a numerical optimization aiming at a technically smooth non-linear characteristic is performed to obtain a higher rate of convergence of the Newton iteration scheme.
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    Image reconstruction from real scattering data (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 372-384 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper deals with the inverse scattering problem of reconstructing the material properties of perfectly conducting or dielectric cylindrical objects. The material properties are reconstructed from measured far-field scattering data provided by the Electromagnetics Technology Division, AFRL/SNH, 31 Grenier Street, Hanscom AFB, MA 01731-3010. The measured data have to be calibrated for use in our reconstruction algorithm. The inverse scattering problem formulated as unconstrained nonlinear optimization problem is numerically solved using an iterative scheme with a variable calibration factor which will be determined during the optimization process. Numerical examples show the successful application of the method to the measured data.
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    Approximation of the objective function: multiquadrics versus neural networks (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 250-265 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Global optimization in electrical engineering using stochastic methods requires usually a large amount of CPU time to locate the optimum, if the objective function is calculated either with the finite element method (FEM) or the boundary element method (BEM). One approach to reduce the number of FEM or BEM calls using neural networks and another one using multiquadric functions have been introduced recently. This paper compares the efficiency of both methods, which are applied to a couple of test problems and the results are discussed.
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    The optimisation of electromagnetic devices using a combined finite element/neural network approach with on-line training (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 266-274 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a novel method of utilising neural networks for optimisation systems. First, a conventional magnetic circuit model of the device is developed to create a set of sensitivity rules which guide the optimisation. The rules are coded in a knowledge-based neural network. Second, an error network is developed to correct the approximations inherent in the magnetic circuit approach and this combines with the first network to generate realistic outputs. Finally, the error network can be trained on-line with a finite element system. Over time, the network replaces the finite element analysis, thus speeding up the optimisation process.
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    Dual formulations for the modeling of thin conducting magnetic shells (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 385-398 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two sets of dual magnetodynamic and magnetostatic finite element formulations taking thin conducting magnetic shells into account are proposed. The abstraction of the thin region from the computational domain is performed by an appropriate treatment of the surface integral terms arising in the weak formulations. Results are presented for two three-dimensional test-problems.
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    Computationally efficient rate dependent hysteresis model (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 445-457 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A fast dynamic hysteresis model is constructed based on the classical Preisach model and a differential equation which delays its input with respect to the actual value to encompass dynamic effects such as eddy currents and domain wall displacement. It is applied to describe the magnetic behaviour of both grain oriented and nonoriented electrical steel sheets. The results of numerical simulations are compared to experiment and power loss prediction is performed.
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    Complementary finite element magnetodynamic formulations with enforced magnetic fluxes (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 656-667 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two complementary 3D finite element formulations, with either the magnetic field or the magnetic vector potential as unknowns, are developed to deal with the modeling of eddy currents in electrical steel laminations. The magnetic flux through the flux gates of the conducting region is imposed via the boundary terms of the weak formulations, in a natural way thanks to the use of edge finite elements. The two formulations are applied to a simple 1D eddy current problem with analytical solution. As a practical 3D application example, a T-joint region of an electrical steel lamination is considered.
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    Investigations of the audible noise of inductors with respect to different ferromagnetic materials (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 647-655 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Fluorescent lamps are one of the most modern light sources. They can be connected to the 230Vac supply without a transformer. To operate them, an inductor and starter are required only. The main disadvantage of this type of light source is the emitted audible noise of a frequency of 100Hz. For this phenomenon the inductor is responsible. Electromagnetic forces and magnetostriction are acting on the body of the device causing the sound emission. Here, the audible noise problem is investigated with respect to different ferromagnetic materials and the range of applied flux densities inside the iron core.
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    Quantum interface conditions for quasi-Fermi levels in an abrupt heterojunction (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 556-569 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We present a semi-quantum model including tunneling effects across an abrupt heterojunction. The discontinuity of the effective masses and the energy bands are considered. The quantum transmission conditions for the quasi-Fermi levels are obtained using WKB approximation. We use mixed finite element approach and a two dimensional mesh which is double-valued for quasi-Fermi levels at a heterojunction. A GaAs/GaAIAs heterojunction diode is then simulated using both drift-diffusion and semi-quantum model by varying doping density at low temperature.
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    Numerical simulation of induction hardening of steel (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 482-493 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: We discuss a model that is capable of describing the process of induction hardening of steel: induction heating - heat transfer - solid-solid phase transitions in steel. It consists of a reduced system of Maxwell's equations, the heat transfer eqaution and a system of ordinary differential equations for the volume fractions of the occuring phases. The model is applied to simulate surface heat treatments, which play an important role in the manufacturing of steel. The numerical methods are implemented with tools from pdelib, a collection of modular algorithms. We present numerical simulations of surface hardening applied to the steel 42 CrMo 4.
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    Magnetic modelling and magneto-hydro-dynamic simulations of an aluminium production electrolytic cell (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 528-538 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A simulation of the motion of molten aluminium inside an electrolytic cell is presented. Since the driving term of the aluminium motion is the Lorentz (j × B) body force acting within the fluid,this problem involves the solution of the magneto-hydro-dynamic equations. Different solver modules for the magnetic field computation and for the fluid motion simulation are coupled together. The interactions of all these are presented and discussed.
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    On the Lorenz gauge (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 323-336 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Although edge elements satisfactorily solve the eddy current problem, formulations allowing the use of standard, node-based elements, are still looked for. But "well-posed" formulations have been elusive up to now. We propose one, based on a particular gauge, div(s a)=-s 2µ v, close to the "Lorenz gauge" of several recent publications, but not identical if one does not assume a piecewise uniform conductivity.
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    The charge-tube method for space-charge simulations (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 548-555 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The charge-tube method is an accurate way of assigning the space-charge of a beam in computational simulations of charged particle systems. The method is described and is compared with the traditional charge-cell method.
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    Fuzzy control of current in thyristor DC drive (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 675-683 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the paper an application of fuzzy logic controller (FLC) for control of thyristor DC drive is presented. During synthesis of the FLC a robustness against variation of structure of the current control plant was taken into account. Comparison between the fuzzy control system and an ordinary digital control system, carried out by simulation method, proved that FLC as a robust controller gives better performance in the range where non-linearity and parameter variation is observed. The simulation results were confirmed by the laboratory experiment.
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    Models of magnetic circuits and their equivalent electrical diagrams (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 600-610 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a method of creating electrical equivalent diagrams of magnetic circuits. The method is based on bond-graph techniques, using flux derivative as flow variable. Couplings between magnetic and electric part of the system are represented by gyrators. Simple models of magnetic branches, including non-linear effects due to saturation, hysteresis and eddy currents, are presented. These models can be easily combined into magnetic circuit models, which can be transformed into dual electric equivalent circuit. Various equivalent circuits of transformers are discussed. The proposed models are simple and particularly useful for system-level simulation of power electronic and motion control systems with magnetic elements. These models can be easily developed if needed. Theoretical considerations are illustrated by examples of digital simulation and experimental results.
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    Selected projection methods to improve the convergence of non-linear problems (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 638-646 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Short computation times required for the design and numerical optimisation of electromagnetic devices with the finite element method are obtained using an adaptive mesh refinement algorithm. Less time is spent on the initial mesh generation, while the time needed for refinement is negligible when special data structures are used. But an even more significant reduction in total computation time is achieved with the initialisation of the solution on the generated mesh. Fewer Newton steps are required to solve non-linear problems compared to a zero initial solution, while the time needed for the projection of the solution is far less than the time needed for a Newton step.
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    Effective reluctivity calculation versus time step calculation of magnetic shielding with ferromagnetic material (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 410-421 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The calculation of magnetic shielding with ferromagnetic material by an effective reluctivity method and a time step method based on the finite element calculation is investigated. The calculation results of both methods are compared with measurement results and with each other in order to check their reliability and accuracy. It turns out that both methods give similar results for the field inside the shielding material, whereas in the surrounding air the effective reluctivity method gives more accurate results than the present time step method.
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    Finite element analysis of electromagnetic torque saturation harmonics in a squirrel cage machine (1999)
    Bradford : Emerald
    Compel 18 (1999), S. 619-628 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The electromagnetic torque oscillations caused by saturation harmonics in a squirrel cage machine are analysed. Special attention is paid to the most important saturation harmonic of alternating field that has three times as many poles as fundamental harmonic and three times its frequency. The operations of the machine as a motor and as a self-excited generator have been investigated. The 2D finite element time-stepping method has been applied to the analysis of a particular machine performance. The finite element equations are coupled with circuits equations which describe the winding connections. The skew of the rotor slots is taken into account.
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    Design optimization of variable frequency driven three-phase induction motors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 135-140 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: An approach to optimize the design of three-phase induction motors for a wide speed range drive is considered. Two operating points in the speed range are taken into consideration. The problem is handled as a constrained optimization problem. An accurate model for the motor in terms of its dimensions has been developed which predicts the motor performance based on about 60 parameters of motor geometry.
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    Computational electromagnetics: some conjectures for industrial and teaching requirements (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 36-46 
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    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The purpose of this paper is to examine the current situation in numerical field computation, paying special attention to the role of education in developing new ideas to meet the ever growing demands of industry.
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    Design considerations for claw pole alternators for wind power applications (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 151-154 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a procedure for the design of claw pole alternators for small scale wind power applications. The method involves a preliminary design stage by means of the classical magnetic circuit analysis and a detailed design stage involving a 3D finite element model. This technique has been implemented in the design of a multiple generation for a small scale gearless autonomous system. The developed model can be implemented for the optimization of the rotor claw geometry through a minimization algorithm.
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    Accelerating the Robin iteration procedure by means of GMRES (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 49-54 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The Robin iteration procedure is a technique for the FEM computation of electromagnetic scattering fields in unbounded domains. It is based on the iterative improvement of the known term of a non-homogeneous Robin condition on a fictitious boundary enclosing the scatterer. In this paper it is shown that the procedure is equivalent to the application of the Richardson method to a reduced system and that the use of GMRES significantly reduces the computational effort.
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    URL: http://dx.doi.org/10.1108/03321649810202964
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    Permanent magnet configuration in repulsive type magnetic bearing for improved radial disturbance attentuation characteristics (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 290-295 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper reports on the development of a repulsive type magnetic bearing system and the importance of permanent magnet (PM) configuration on the attenuation of radial disturbance. A new configuration of the permanent magnet of the bearing system resulting in improved stiffness characteristics in the radial direction has been described. Prototype models have been designed and developed in our laboratory and experiments carried out.
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    URL: http://dx.doi.org/10.1108/03321649810208274
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    Dynamic modelling of a synchronous linear motor with permanent magnet excitation and solid yokes (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 189-195 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A three-axes synchronous torque motor with permanent magnet excitation and solid stator and rotor yoke is used to adjust an air borne telescope and to eliminate oscillations. Hence the motor is part of a complex mechanical system and has to be included in the structural analysis. For this reason the attempt is made to simulate the nonlinear behavior of the motor by a dynamic model considering the eddy current fields and the magnetization characteristic of the iron.
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    URL: http://dx.doi.org/10.1108/03321649810203125
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    Design of RLC circuit for pulse magnetizer of permanent magnets (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 412-417 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The current pulse magnetizing process of permanent magnets is considered. General conditions for the design of a pulse magnetizer are given for the case when the magnetizing process is effected on the magnet put in free space. The boundary-integral analysis of the magnetic field inside the magnet is presented. It concerns both the state corresponding to the maximum value of the magnetizing current pulse and the magnetized state after the full magnetizing.
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    URL: http://dx.doi.org/10.1108/03321649810369519
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    Field and power loss distribution on covers of power transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 302-306 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Heavy current bushings passing through steel cover plates and housing walls of power transformers, generators and other large power equipment are thermally hazardous elements of construction and a source of additional power losses. Safety and reliability of such expensive objects and safety of power delivery often depend on the proper design of these elements. In the paper a computer analysis, based on Maxwell equations and analytical representation of electromagnetic field was carried out. Non-linear permeability of solid steel was considered with the help of analytical approximation. Eddy current losses have been calculated and compared using different methods of calculation and experiments. The method of forecasting possible excessive heating and hot spot with the help of electromagnetic criteria was used. Various constructional means of loss and hot spot reduction were proposed and examined.
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    URL: http://dx.doi.org/10.1108/03321649810369456
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    A numerical investigation of Preisach and Jiles models for magnetic hysteresis (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 357-363 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The Preisach and Jiles models for hysteresis are applied to reconstruct BH loops from measurement data for constructional steel St 37. The distribution function for the Preisach model is determined from all the available, 18, measured BH loops starting from the initial curve. The five unknown parameters in Jiles model are determined by the simulated annealing method to minimize the distance between the largest measured BH loop and the corresponding computed loop. Although Jiles model gives differences from the measured BH loops for low applied fields, it provides results fitted well to the largest measured loop for which the parameters are optimized. The Preisach model gives good fitting over a wide range of the applied field.
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    Finite element method in evaluation of torque ripple in synchronous reluctance motor (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 369-373 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper deals with the calculation and reduction of torque pulsation in synchronous reluctance motors (SRM). The analysis is based on finite element modeling and proposes a method of dynamic torque characteristic calculation. The mutual connection between static and dynamic torque characteristic is also established. Several aspects for reduction of torque pulsation are demonstrated and applied with success.
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    Ultra high torque SRM - measurement and computer design (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 364-368 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A prototype of a special electrical machine - double statored switched reluctance motor - has been developed which produces a very high static and dynamic torque. Possible ways of measuring the machine are presented. The basic parameters of the model are described. Results are compared to those obtained by computer design. A difference between computed and measured results is discussed.
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    URL: http://dx.doi.org/10.1108/03321649810369492
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    Electromagnetic forces calculation on power transformer windings under short circuit (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 374-377 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper aims to determine the electromagnetic forces acting in a power transformer, when a current corresponding to the first peak of a three-phase circuit flows in the windings. The finite element method for the evaluation of the field's values is applied, and the electromagnetic forces acting in a power transformer windings are calculated. Finally the results of a computation test by a personal computer for the exposed method are graphically presented and some conclusions about the behavior of the calculated electromagnetic forces are derived.
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    Measurement of near-fields radiated by an induction heating power supply (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 389-392 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Induction coil and the extension cable of an induction heating power supply radiate electromagnetic noise and often give disturbance to other equipment and systems closely located. In this paper a method for measuring near-fields radiated by this system is proposed. Related data measured by using near-field probes and spectrum analyzer are processed and a software is developed for calculating antenna factor. The electric field results are given in graphics.
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    URL: http://dx.doi.org/10.1108/03321649810203323
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    A new probe for eddy current testing of low conductivity materials (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 393-397 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the paper a new probe for eddy current testing of low conductivity materials is presented. The new probe has been applied for eddy current testing of H2SO4 water solution. Results of measurements are presented.
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    Non-destructive testing of layered structures using generalised radial basis function networks trained by the orthogonal least squares learning algorithm (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 382-388 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The evaluation of the conductivity profile of layered metallic structures is performed via the inversion of the impedance of a circular air cored probe coil of rectangular cross section. The inversion approach is based on the implementation of generalised radial basis function neural networks. The choice of the size of the network and the evaluation of its weights are handled by the orthogonal least squares learning algorithm. The merits of the proposed method are illustrated in the light of two examples concerning non-destructive testing applications.
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    Conditions for the existence of an X-point in a magnetic field (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 773-780 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A sufficient condition for the existence of a node (i.e. an X-point) in lines of a quasi-static magnetic induction field is proved. The theoretical approach is developed for two-dimensional fields. The problem of obtaining an X-point in a magnetic induction field is encountered in toroidal devices (tokamaks) for controlled thermonuclear fusion experiments. The proposed method is capable of identifying possible X-point locations through the knowledge of field variables which are easy to calculate and/or measure.
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    URL: http://dx.doi.org/10.1108/03321649810221404
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    Microwave interdigital bandpass filters modeling (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 690-696 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: An improved model for microwave interdigital filters design and analysis is developed by correction of Denig's procedure (1989). This model enables correct modeling multiple-coupled transmission line structures as parallel sections of single coupled lines. Also, it is very suitable for the design and analysis of the filters by means of widely used microwave CAD programs. In this way the design and analysis of the microwave interdigital filters are significantly simplified. The verification of modified Denig's procedure is carried out through the two examples of the microstrip interdigital bandpass filters by means of program package LIBRA.
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    3D finite element analysis modelling of the arc chamber of a current limiting miniature circuit breaker (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 244-251 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper presents the initial stage of a 3D finite element (FE) model of the electromagnetic field in the arc chamber of a current limiting miniature circuit breaker (MCB). The final objective of the model is to compute the magnetic forces on the arc, and predict the position of the arc at a series of discrete time steps. The trajectory of the arc calculated from the model will then be compared with experimental data recorded by a high speed arc imaging system (AIS) on a flexible test apparatus (FTA) designed to simulate the operation of a commercial MCB under laboratory conditions. By comparing the FE model of the arc behaviour with the actual arc images generated from the AIS an insight into the factors governing the motion of the arc can be gained. In particular the relative importance of the average flux density across the arc chamber is compared with the local flux density distribution at the arc roots. An understanding of the influence of the magnetic flux distribution can then be used to improve the magnetic design of the MCB to promote low immobility times and effective current limiting operation.
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    The analysis of the leakage reactance in a one-phase transformer with asymmetrical disk-type windings (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 285-289 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A three-dimensional analysis of the quasistationary, magnetic leakage field of a one-phase transformer with asymmetrical disk windings is presented. A simplified mathematical model of the transformer based on Maxwell's equations is applied. Computational results of the leakage reactance for asymmetrical disk-type windings are compared with the analytical ones according to Richter's formulae.
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    The transient and steady state performance of single-phase induction motor with two capacitors fed by matrix converter (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 296-301 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this study, a single-phase induction motor with constant v/f, fed by matrix converter, is considered under various frequencies. The modeling of the motor, mechanical load for single phase induction motor and matrix converter have been obtained by using Simulink package program. The performance of the motor under various frequencies is determined. A single-phase induction motor considered in this work has a running capacitor. The analysis and simulation results are presented.
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    Using genetic algorithm for the optimization of electromagnetic devices (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 181-185 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Stochastic methods offer a certain robustness quality to optimization process. In this paper, the genetic algorithm, based on the computer simulation of the natural evolution, is used for the shape optimization of an electromagnetic actuator. The framework is modeled by a 2D finite element method allowing the computation of the magnetic force. The aim is to obtain a desired force profile considering the armature movement.
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    An approach to improve the synchronous machine model in saturated state (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 261-266 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A magnetic study has been linked to an electrical survey to improve a saturated synchronous machine model. The machine is supplied by a sinusoidal voltage source, but the developed model could be extended to a non-sinusoidal case. The last one corresponds to electrical machines supplied by power electronic converters. First, the machine magnetic state is analysed from a numerical calculation based on the finite element method. Saturation laws are established. The results show that some parameters which were considered constant values vary with the saturation level. Second, we introduce the saturation laws in the machine electrical equations. The voltage supplied machine is simulated for an electrical transient state. Finally, the developed model is compared to a reference one which uses experimental constant parameters. The simulation results show that the proposed electromagnetic laws significantly modify the machine currents' waveforms.
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    Influence of the sampling period on sinusoidal steady-state operations of inverter-fed asynchronous motors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 219-224 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Inverter-fed asynchronous motors represent today a source of disturbance in electric drives, because they irradiate outside their frames electromagnetic waves with different frequencies. Knowledge of the disturbances generated inside the drive is necessary. In the paper the influence of the sampling time on the distortion between predicted and actual armature current is evaluated on the basis of an analytical calculus procedure, that allows for an easy evaluation of the harmonic contents of the currents. This is the first step towards the evaluation of the causes of environmental electromagnetic disturbances.
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    The non-linear characteristics of AC machines based on the calculation of magnetic field co-energy (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 324-328 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Non-linear characteristics, as relations between linked fluxes and currents of individual machine coils, are sought for in the so called circuit models of saturated electrical machines. Their determination can be based on the co-energy of the magnetic field only, which is a multivariable function of all coil currents and rotor position angle. The author proposes the calculation of co-energy values at necessary points by the FEM and the interpolation of the results by a suitable multivariable spline function. The functions of linked fluxes are generated as the first derivatives of the spline. This way could be used to separate the circuit calculation from the field calculation when saturated machines are modelled. An example of a wound rotor induction machine is used to show the elementary problems of the calculation of the non-linear characteristics.
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    Computational electromagnetics in Poland: a review (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 427-438 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper presents a historical review, the state of the art and recent advances in the field of computational electromagnetics at leading universities and research institutes in Poland. Contributions made by Polish scientists to the development of fundamental electromagnetism, as well as to computational methods, are emphasized, and some conclusions are drawn regarding expected future developments.
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    3-D calculations of leakage field and reactance for special transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 460-474 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Two approaches to 3-D magnetic field calculations for low-power special transformers are presented in the paper. The application of fast calculation procedures based on the finite difference method, to direct solving of the Poisson and Laplace equations is given. The calculated example deals with the three-phase leakage transformer. On the other hand, the iterative solution of regularized integral equations used for calculation of 3-D field distribution and integral parameters of leakage field in current transformer is also presented. The software packages developed by the authors are useful for computer-aided design of low-power special transformers.
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    Fast computation of coupled fields in complex, 3-D, industrial electromagnetic structures (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 489-505 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Recent progress in the development of electromagnetic field theory and sophisticated software for solution of complicated, non-linear, 3-D structures is not always accompanied with relatively cheap and simply presented engineering instructions, easy to use for regular industrial design. In the paper some theoretical and practical examples are given as to how one can get over a excessive calculating difficulties to obtain quickly simple design directions and reduce complicated theory to simple practical conclusions. The fast and cheap package RNM-3D is validated by comparison with industrial test data and with the interactive graphics system is the final illustration of the effectiveness of such an approach. RNM-3D is used successfully in many transformer works the world over.
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    Analysis of drifting charged aerosols from HVDC ionizers via a hybrid CSM-FD method (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 620-627 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper are summarized our research activities dealing with the theoretical and experimental analysis of high voltage direct current (HVDC) ionizers. We present here the basic principle of a hybrid charge simulation-finite difference method, that has been used to simulate the electric behaviour of these devices, by computing the electric field strength and the ionic current density distribution, therefore the efficiency of emission. We have realized an experimental ion counter and we have used it to verify the values predicted by means of this numerical technique.
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    Application of higher-order spectra for signal processing in electrical power engineering (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 602-611 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: During recent years, higher order statistics (HOS) have found a wide applicability in many diverse fields, e.g. biomedicine, harmonic retrieval and adaptive filtering. In power spectrum estimation, the signal under consideration is processed in such a way that the distribution of power among its frequency is estimated and phase relations between the frequency components are suppressed. Higher order statistics and their associated Fourier transforms reveal not only amplitude information about a signal, but also phase information. If a non-Gaussian signal is received along with additive Gaussian noise, a transformation to higher order cumulant domain eliminates the noise. These are some methods for estimation of signal components, based on HOS. In the paper we apply the MUSIC method both for the correlation and the fourth order cumulant, to investigate the state of asynchronous running of synchronous machines and the fault operation of inverter-fed induction motors. When the investigated signal is distorted by a coloured noise, more exact results can be achieved by applying cumulants.
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    Magneto-thermo-elastic vibration of thin shells under a surge current (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 407-411 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The mathematical model of thin cylindrical conducting shell deformation under a current surge was elaborated. The shell deformation influence on the electromagnetic and thermal field distribution has been calculated. The perturbation analysis of the vibration of a thin cylindrical shell under heavy current surge was given. The critical wave number and mode was found and the most probable instability was calculated.
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    Computer simulation of dynamic states of the silicon micromotor (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 307-312 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper presents the results of silicon micromotor static and dynamic simulations by means of finite element method and the Moulton-Adams algorithm as well. Capacitance and torque curves calculation. The virtual work principle has been applied. The dynamic states of the motor are described by the non-linear and non-stationary system of ordinary difference equations solved numerically. Some results of computer simulation of dynamic states are presented and discussed.
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    Analytical approximation of the dependence of magnetic material properties on temperature (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 402-406 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Temperature dependence of magnetic susceptibility has been approximated by the extension of Curie-Weiss law to ferromagnetic states. Application of similar relations to other properties and corresponding model parameters of magnetic materials would enable thermal analysis of circuits containing ferromagnetic cores.
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    Complementarity by "local corrections" (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 717-725 
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    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: By using complementarity (solving for both potentials, scalar and vector), one often can provide bilateral bounds for some quantities of interest, like for instance the reluctance of a circuit. However, the vector potential method is expensive, and does not make use of information acquired in the first phase of solving for the scalar potetential. We show how to improve on this by a "local correction" process which, starting from h = grad ?, yields a divergence-free b, close to µh, by a series of local and independent (parallel) problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221279
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  • 87
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    Performance analysis of locally recurrent neural networks (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 708-716 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Many practical applications of neural networks require the identification of non-linear deterministic systems or chaotic systems. In these cases the use of a network architecture known as locally recurrent neural network (LRNN) is often preferable in place of standard feedforward multi-layer perceptron (MLP) networks, or of globally recurrent neural network. In this paper locally recurrent networks are used to simulate the behaviour of the Chua's circuit that can be considered a paradigm for studying chaos. It is shown that such networks are able to identify the underlying link among the state variables of the Chua's circuit. Moreover, they are able to behave like an autonomous Chua's double scroll, showing a chaotic behaviour of the state variables obtainable through a suitable circuit elements choice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221251
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  • 88
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    A procedure for magnetic design and optimization of permanent magnet brushless DC motors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 749-756 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The paper reports on a development of an automated CAD optimization system which interfaces an external design routine with a general purpose finite element software. The magnetic analysis is performed using a parameterized model and the process is controlled from within procedures written in MATLAB programming environment. Results are shown for a permanent magnet brushless DC motor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221378
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  • 89
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    Lorentz gauge eddy current formulations for multiply connected piecewise homogeneous conductors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 732-740 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Vector potential formulations of Maxwell's equations need to be gauged, otherwise nodally based finite element approximations lead to an ill conditioned linear system. In this paper alternative Lorentz gauge formulations will be analysed. Particular attention will be paid to the conditions to be applied at material interfaces, bearing in mind ease of implementation in a finite element code and efficiency of solution. The methods discussed are designed to cope with the most challenging physical situations, namely, multiply connected abutting conductors made of different materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221314
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  • 90
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    Computation of 3D electromagnetic field and torques in spherical motors (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 106-110 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: A spherical motor is a novel electromechanical device that has obtained worldwide attention for its attractive advantages. A general analysis of electromagnetic torque in double excited spherical motor has been completed on the calculation of its 3D electromagnetic field distributions. The analysis accounts for the effect of open-end region in the stator. Double scalar magnetic potentials method has been used in the FEM numerical analysis. On the computation results, the other electromagnetic parameters can be calculated, which will be very significant in the design and performance prediction of the spherical motor. The calculation results indicate that the device is capable of continuous speed control and efficient torque production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203026
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  • 91
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    Effect of the non-linearity of demagnetization curves on the torque of hybrid stepping motors with permanent magnets in slots (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 318-323 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The recent achievements in electronic control as well as the higher performance of advanced permanent magnets have brought about a change in the general strategy for design and development of new types of small electrical machines. A special application of permanent magnets (PM) is represented by hybrid stepping motors (HSM). The latter are a sort of combination of variable reluctance-motors and permanent magnet-motors. The influence of various PM inserts into the magnetic circuits of electromechanical converters on field and force distribution has been already investigated by the authors (1996). Promising results for HSM have been reported, especially when rare-earth PMs are used. The main aim of PM inserting, when they are put into slots of slotted pole shoes with radial N-S polarization, is to focus magnetic field lines in the corresponding teeth. As a result, the reluctance stepping torque can be increased depending on the material used. Now a further step is made by extending the analysis from the case of linear to that of non-linear demagnetization curves of permanent magnets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810693474
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  • 92
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    An easy and fast 2D finite element program for studying the fields in three-phase transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 342-346 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: All the algorithms introduced by the authors in their finite-element computational program for studying fields easily and quickly are described in the paper. Moreover, an application of the analysis of the thermal field to a three-phase transformer is proposed. This analysis gives a valid help to designing transformers having to provide services to satisfy some particular needs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369474
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  • 93
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    Loss evaluation of non-magnetic tie-plates in transformers (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 347-351 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: This paper tests the eddy current analysis methods based on TEAM benchmark model, evaluates the engineering effectiveness of the eddy current codes through product-based test models, and proposes an engineering-oriented loss solver to deal with the eddy current loss problems concerning the core tie-plates in large power transformers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203260
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  • 94
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    Stability analysis of equilibrium states of a certain class of non-linear dynamic circuits (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 741-748 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Dynamic non-linear circuits driven by DC voltage and current sources are considered in the paper. The problem of identification of asymptotically stable equilibrium states is analyzed. The circuits are studied where there is a one-to-one correspondence between each operating point of a DC model of a dynamic circuit and equilibrium state of the dynamic circuit. A method is developed, based on quantities concerning resistive circuits only, enabling us to select some of the operating points being asymptotically stable equilibrium states. It is shown that these operating points are asymptotically stable equilibrium states of some class of dynamic circuits which differ one from another in characteristics of the capacitors and inductors. The approach is illustrated by a numerical example.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810221369
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  • 95
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    On the use of the FEM and BIE methods in the 3D magnetic field computation of the reactors with air gaps (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 116-120 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The calculation results of the 3D magnetic field in a reactor are examined using the computer packages TRACAL3 as well as OPERA3D. The first own package is based on the boundary integral equations (BIE) and the second commercial package is deduced from finite elements method (FEM). As an example, the magnetic flux density components were calculated. For the reactors with large air gaps, the numerical results obtained by BIE and FEM are relatively close.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810369348
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  • 96
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    Optimal shape design of the HV winding of a test transformer (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 128-134 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In the paper, attention is focused on a class of single-phase transformers that are employed when a high-voltage withstand test is required for verifying the quality of the dielectric insulation of a given component. The HV winding of this kind of transformer is made up of several layers, characterized by height that decreases along with the increase of the voltage profile in order to keep the distance between winding and ground within acceptable limits. Therefore, the designer of such devices is mainly concerned with the shaping of the HV winding; starting from a tentative configuration, he has to find the winding shape such that the electric breakdown cannot occur, at the same time keeping the volume of oil and active materials as small as possible. Traditionally, the design is developed by means of a trial-and-error approach based on a sequence of field analyses, varying a design variable at a time; the paper shows how the design problem can be solved more efficiently by optimizing the profile of the winding in an automatic way.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203053
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  • 97
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    Identification of thermal parameters in a coupled magnetic-thermal model with the experimental designs method (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 331-336 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In analysing coupled electromagnetic thermal behaviours in electrical devices one of the main difficulties is related to the uncertainties of thermal parameters. The authors present, in this work, a technique using the method of experimental designs for the identification of thermal parameters necessary for a coupled finite element model analysing the magneto-thermal behaviour of an electromagnetic device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203242
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  • 98
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    Numerical modeling of transient heating of solid plate 3D structure (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 337-341 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: The heating of flat metal products has an increasing importance in different technical applications. One of the most advanatageous heating methods is induction heating. The heat is generated within the workpiece itself. It provides high power densities and high productivity. For induction heating of flat metal products two methods are applied: the longitudinal and the tranverse magnetic flux heating. In our case we have applied tranverse flux heating. This paper presents certain results of electromagnetic field obtained by means of finite element method and transient thermal field obtained by finite difference method. The analysis is made by simulating the heating phenomenon while the sophisticated software has been employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203251
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  • 99
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    Influence of the neutral in the thermal performance of a three-phase induction motor under unbalanced power supply using the finite element approach (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 378-381 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: In this paper the influence of the neutral in the thermal performance of a three-phase squirrel cage induction motor fed by asymmetrical supply voltages is studied and analysed. A 2D finite element formulation was used to solve the steady-state heat transfer problem. The eddy currents in the rotor bars were evaluated using a combined 3D finite element approach with analytical expressions. The numerical solutions are compared with measured experimental results obtained in laboratory tests for two load conditions and two unbalanced power supply situations with and without the neutral wire connected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203305
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  • 100
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    A 3D design optimisation of electromagnetic low-voltage linear actuators based on FE force computation (1998)
    Bradford : Emerald
    Compel 17 (1998), S. 166-170 
    Details
    ISSN: 0332-1649
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Experience and exploring the linear AC and DC actuators confirm the necessity of the computation of forces distribution as the step preceding their optimal design. This paper expresses an approach to computations of different forces of low-voltage linear actuators acting on both mechanical and/or electrical parts. The computations are based on magnetic coenergy concept associated with virtual work method and simulated by step displacement of the armature from the total open through total closed position. The magnetic coenergy is numerically computed through the flux-linkage approach, where the magnetic field distribution is obtained by applying the finite element method in 3D-domain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/03321649810203099
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