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1 – 10 of 18
Article
Publication date: 4 September 2017

Werner Renhart, Oszkár Bíró, Christian Magele, Kurt Preis and Alexander Rabel

The purpose of this paper is the modelling and estimation of inrush currents while energising power devices under no load conditions. An analytical representation of the nonlinear…

Abstract

Purpose

The purpose of this paper is the modelling and estimation of inrush currents while energising power devices under no load conditions. An analytical representation of the nonlinear B-H curve serves for considering the hysteresis behaviour in the numerical model.

Design/methodology/approach

The model is implemented into a standard finite element formulation to compute transient problems.

Findings

Inrush currents behave like faults in power distribution facilities. Its prior estimation helps to distinguish between operating conditions and faults.

Research limitations/implications

The magnetic cores may become extremely magnetised. At such high material saturations, the material characteristics are not measurable accurately. Hence, the results depend on the extrapolation of the B-H curves.

Originality/value

The use of first-order reversal curves within the major hysteresis loops helps in a convenient way to estimate peak and shape of the inrush currents.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Content available
Article
Publication date: 10 July 2009

472

Abstract

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 4
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 14 September 2010

Andrej Stermecki, Oszkár Bíró, Kurt Preis, Siegfried Rainer, Klaus Krischan and Georg Ofner

The purpose of this paper is to define a time‐efficient numerical procedure for the extraction of load‐dependent equivalent circuit (EC) parameters of induction machines. The…

Abstract

Purpose

The purpose of this paper is to define a time‐efficient numerical procedure for the extraction of load‐dependent equivalent circuit (EC) parameters of induction machines. The parameters are determined for every operating point, thus their variation due to skin effect and material saturation under arbitrary load condition is taken into consideration.

Design/methodology/approach

Two methods are presented and compared. The first one is based on the numerical simulation of the standard measurement process, yielding an EC with constant parameters. A time‐harmonic finite element analysis is applied in the second method to calculate the load‐dependent EC parameters. Material linearization and the superposition principle for the magnetic flux are employed to define the leakage inductances.

Findings

A distinct load dependence of all EC parameters has been proven as well as the clear disparity between stator and rotor leakage inductances. These effects can only be taken accurately into account by the EC obtained by the second numerical procedure proposed.

Originality/value

The presented method successfully overcomes typical problems of the measurement process and of the standard numerical procedure for EC parameter estimation, thus the obtained EC parameters are load‐dependent while the physical interpretation of the variables and parameters remains straightforward. Hence, the paper of the internal machine variables is enabled.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 June 2001

Igor Tičar, Jože Pihler, Oszkár Bíró and Kurt Preis

The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid…

Abstract

The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid insulation materials, at borders between different insulation materials and, of course, in solid dielectrics. These phenomena result in insulation breakdowns, various disturbances to the environment, and after longer periods, some large‐scale failures. This paper presents the results of theoretical research of the behavior of a system of medium voltage covered conductors. This research work has been elaborated by the use of computer aided electric field calculations. For the confirmation of theoretical findings, practical measurements of partial discharges have been made.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 20 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 19 June 2007

Gernot Matzenauer, Oszka´r Bíro´, Karl Hollaus, Kurt Preis and Werner Renhart

Perfectly matched layers (PMLs) are used for reflectionless truncation of the problem boundaries in finite element methods applications. In this paper, the method of PMLs is…

Abstract

Purpose

Perfectly matched layers (PMLs) are used for reflectionless truncation of the problem boundaries in finite element methods applications. In this paper, the method of PMLs is extended to truncate any lossless medium and the method is implemented for the T formulation.

Design/methodology/approach

The basic concept behind PMLs is to create an artificial material with a complex and diagonal anisotropic permittivity and permeability. For the A, V formulation PMLs are well known.

Findings

It is shown that it is possible to truncate any linear lossless material with PML layers, and if the material has small losses the PML works fine.

Originality/value

In the present paper, an artificial anisotropic lossy material is applied to a 3D edge finite‐element T, formulation to form perfectly matched layers.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 March 2005

Oszkár Bíró, Kurt Preis and Igor Ticar

This paper aims at developing a computational technique to take account of the laminated nature of iron cores when computing their eddy current losses.

Abstract

Purpose

This paper aims at developing a computational technique to take account of the laminated nature of iron cores when computing their eddy current losses.

Design/methodology/approach

A method is presented to compute three‐dimensional eddy current distributions in laminated media by means of the finite element method. In a first step, the laminated medium is assumed to have an anisotropic conductivity with zero (or very low) value in the direction normal to the laminations. In a second step, the eddy currents within the laminates are computed by solving the quasistatic electromagnetic field individually in each sheet. In these essentially two‐dimensional analyses, the boundary conditions are taken from the three‐dimensional field distribution determined in the first step.

Findings

Comparisons with results obtained from a finite element model taking account of each laminate prove the validity of the method.

Research limitations/implications

The method is presented for linear media only. Taking account of nonlinearity is an important future topic.

Originality/value

Taking account of the laminations by treating the magnetic field distribution obtained from a homogenised model is a novelty of potential benefit to researchers developing methods of loss computation in laminated media.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 16 November 2010

Oszkár Bíró, Stefan Außerhofer, Kurt Preis and Yu Chen

Grain‐oriented steel has a distinctly anisotropic and nonlinear behaviour. Only in rare cases is the magnetisation curve known for directions other than the principal ones. The…

Abstract

Purpose

Grain‐oriented steel has a distinctly anisotropic and nonlinear behaviour. Only in rare cases is the magnetisation curve known for directions other than the principal ones. The paper aims at providing a model to obtain these curves for any direction if those in the easy and hard directions are only given.

Design/methodology/approach

The well‐known elliptic model is modified in order to correctly mimic the typical behaviour of grain‐oriented steel which is not described correctly by the original elliptic model. An additional condition is introduced to fix the angle between the flux density and magnetic field intensity.

Findings

The model is found to yield good agreement with measurements in case of a special material for which measured curves for intermediate angles are available.

Research limitations/implications

Further research is necessary to establish whether the model is applicable to other materials.

Originality/value

The new model can be used in numerical analyses of devices comprising saturated grain‐oriented steel material if the magnetisation curves are given in the principal directions.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 10 July 2009

Gergely Koczka, Stefan Außerhofer, Oszkár Bíró and Kurt Preis

The purpose of the paper is to present a method for efficiently obtaining the steady‐state solution of the quasi‐static Maxwell's equations in case of nonlinear material…

Abstract

Purpose

The purpose of the paper is to present a method for efficiently obtaining the steady‐state solution of the quasi‐static Maxwell's equations in case of nonlinear material properties and periodic excitations.

Design/methodology/approach

The fixed‐point method is used to take account of the nonlinearity of the material properties. The harmonic balance principle and a time periodic technique give the periodic solution in all nonlinear iterations. Owing to the application of the fixed‐point technique the harmonics are decoupled. The optimal parameter of the fixed‐point method is determined to accelerate its convergence speed. It is shown how this algorithm works with iterative linear equation solvers.

Findings

The optimal parameter of the fixed‐point method is determined and it is also shown how this method works if the equation systems are solved iteratively.

Originality/value

The convergence criterion of the iterative linear equation solver is determined. The method is used to solve three‐dimensional problems.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 April 1965

Günter Menges

Es ist mir eine ausserordentliche Freude, an dieser Stelle, wo die Wiege der modernen Fremdenverkehrswissenschaft stand, zu Ihnen sprechen zu dürfen. So danke ich aufrichtig…

Abstract

Es ist mir eine ausserordentliche Freude, an dieser Stelle, wo die Wiege der modernen Fremdenverkehrswissenschaft stand, zu Ihnen sprechen zu dürfen. So danke ich aufrichtig meinem Freund und Kollegen Kurt Krapf dafür, dass er mir diese Gelegenheit eines Vortrages gegeben hat. Obgleich ich ein enges, allerdings «voreheliches» Verhältnis zur Fremdenverkehrswissenschaft aufzuweisen habe, werden Sie es mir nicht verdenken, wenn ich auf meine gegenwärtig legale Beziehung, nämlich zur Ökonometrie, mich stärker als auf jene frühere stütze: Mein Vortrag wird mehr von der Ökonometrie als von der touristischen Wissenschaft, welche kaum mehr als ein Exempel liefert, handeln.

Details

The Tourist Review, vol. 20 no. 4
Type: Research Article
ISSN: 0251-3102

Article
Publication date: 1 April 1994

Claude Kaspar

Nach 1953 ist die Internationale Vereinigung wissen‐schaftlicher Fremdenverkehrsexperten zum zweiten Mal in Wien zum jährlichen Kongress versammelt. Damals nach Kriegsende ging es…

Abstract

Nach 1953 ist die Internationale Vereinigung wissen‐schaftlicher Fremdenverkehrsexperten zum zweiten Mal in Wien zum jährlichen Kongress versammelt. Damals nach Kriegsende ging es darum, einem langsam wiedererstarkten Tourismus eine solide wissenschaftliche Basis zu geben. Es waren auch die Tourismuswissenschafter der klassischen Fremdenverkehrsländer Italien, Spanien, Österreich und der Schweiz, welche sich 1949 erstmals in der Schweiz trafen, um diesem Vorhaben eine konkrete Struktur zu geben. Prof. Paul Bernecker, als einer dieser Promotoren — genannt seien hier die andern: Prof. Walter Hunziker (bis 1973 Präsident), Prof. Kurt Krapf (erster Generalsekretär) und Prof. Angelo Mariotti — übernahm es, den Wiener Kongress zu organisieren. Er war dem Thema “Marktforschung und Werbung im Fremdenverkehr” gewidmet, übrigens ein nach wie vor aktuelles Thema, auch wenn die Terminologie heute in Marketing bzw. Marktbearbeitung oder Kommunikationspolitik erweitert wurde.

Details

The Tourist Review, vol. 49 no. 4
Type: Research Article
ISSN: 0251-3102

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