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Article
Publication date: 12 July 2011

Massimo Guarnieri

The paper seeks to do the following. To provide an expression of the electromagnetic power flow that is alternative to the Poynting's theorem expression, overcomes its postulate…

Abstract

Purpose

The paper seeks to do the following. To provide an expression of the electromagnetic power flow that is alternative to the Poynting's theorem expression, overcomes its postulate feature, and is particularly suitable for electric circuit elements.

Design/methodology/approach

The paper proceeds from fundamental electromagnetic laws and, independently of Poynting's formulation, follows an approach that generalize established double formulations of the electrostatic and magnetostatic energies.

Findings

The paper proposes a compact and straightforward expression of the electromagnetic power flow based on the fundamental electromagnetic field sources, i.e. charge and current densities.

Practical implications

The achieved expression confirms Poynting's expression in the case of electric elements, overcoming its arbitrariness, generalizes previous partial results by other authors, deduced via the Poynting's power balance.

Originality/value

Is promising in the computation of power flow electromagnetic devices connected in electrical circuits, i.e. for coupled problems where the analysis of electromagnetic system interfaced to electric circuits is required. Due to its simple structure and straightforward deduction it has educational value to demonstrate the expressions of the electric power in circuit elements.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 June 2000

A. Savini

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community…

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Abstract

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 2 March 2012

Patricia Penabad‐Duran, Xose M. Lopez‐Fernandez, Janusz Turowski and Pedro M. Ribeiro

The purpose of this paper is to apply a 3D methodology to assess the heating hazard on transformer covers and present a practical tool to design amagnetic inserts arrangement.

Abstract

Purpose

The purpose of this paper is to apply a 3D methodology to assess the heating hazard on transformer covers and present a practical tool to design amagnetic inserts arrangement.

Design/methodology/approach

A practical 3D methodology linking an electromagnetic analytical formulation with thermal finite element method is used for computation. Such methodology allows the evaluation of the temperature on metallic device elements heated by electromagnetic induction. This is a 3D problem which in the case of power transformers becomes especially difficult to apply due to the discretization requirement into the thin skin depth penetration compared to big machine dimensions.

Findings

From the numerical solution of the temperature field, decisions on dimensions and different amagnetic inserts arrangements can be taken to avoid hot spots on transformer covers.

Research limitations/implications

Some parameters presented in the model as heat exchange coefficients and material properties are difficult to determine from formulae or from the literature. The accuracy of the results strongly depends on the proper identification of those parameters, which the authors adjust based on measurements.

Originality/value

Differing from previous works found in the literature, which focus their results in power loss computation methods, this paper evaluates losses in terms of temperature distribution, which is easier to measure and validate over transformer covers. Moreover, an experimental work is presented where the temperature distribution is measured over a steel cover plate and a cover plate with amagnetic insert.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 November 2016

Hugo Rodriguez-Ignacio and Xose M. Lopez-Fernandez

The purpose of this paper is the numerical verification of the linearization coefficient ap proposed by Turowski for the calculation of the electromagnetic field distribution and…

Abstract

Purpose

The purpose of this paper is the numerical verification of the linearization coefficient ap proposed by Turowski for the calculation of the electromagnetic field distribution and therefore the stray losses inside magnetically saturated solid steel conductors.

Design/methodology/approach

The numerical verification is performed on a case study consisting of a simple current conductor sheet parallel to a solid steel plate. Numerical computations are compared with analytical calculations with and without inclusion of the semi-empirical Turowski’s coefficient.

Findings

Results confirm a good agreement between numerical values for steel with non-linear permeability and analytical ones applying Turowski’s coefficient. This is particularly powerful in the case of analytical calculation of the magnetic surface impedance (SI) to increase precision when hybrid methods are used. The concept of SI enables the establishment of hybrid approaches for the calculation of stray losses, combining the numerical methods (finite difference method, finite element method (FEM), etc.) together with the analytical formulation, gaining from the advantages of both methods.

Originality/value

Previous numerical analysis was focused on the field dependence on time for several depths inside solid steel. The aim of this paper is to investigate the electromagnetic field distribution inside solid steel on a representative FEM model and verify how the linearization coefficient ap proposed by Turowski works.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 35 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 February 1985

A.K. GASIORSKI

The paper presents a numerical version of a method which makes it possible to calculate any quasi‐stationary two‐dimensional field in non‐ferromagnetic conductors of limited…

Abstract

The paper presents a numerical version of a method which makes it possible to calculate any quasi‐stationary two‐dimensional field in non‐ferromagnetic conductors of limited cross‐sections for unknown boundary conditions on the conductor surfaces. The principle of the method depends on the application of a finite‐element network within the current region and the method of variable division within the no‐current region. The conditions of the continuity of the vector potential and the continuity of the tangential component of the magnetic induction vector are considered in the form of functions defined by the Bubnov‐Galerkin method. Since the separation of the variables is used in the region without current, it is easy to satisfy the conditions at infinity for different types of input. The shapes of the conductors in the current region are, on the other hand, illustrated by discretization by means of the finite element method. An example of the application of the method for two‐dimensional analysis of power losses in two thick solid circular conductors placed in a sinusoidally varying transverse field is presented. Plots of power losses were drawn based on numerical computation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 4 no. 2
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 September 2004

Andrzej Patecki, Sławomir Stępień and Grzegorz Szymański

Presents 3D method for the computation of the winding current distribution and power losses of the electromagnetic gear. For a prescribed current obtained from measurement, the…

Abstract

Presents 3D method for the computation of the winding current distribution and power losses of the electromagnetic gear. For a prescribed current obtained from measurement, the transient eddy current field is defined in terms of a magnetic vector potential and an electric scalar potential. From numerically obtained potentials the power losses are determined. The winding power losses calculation of an electromagnetic gear shows that a given course of the current generates skin effect and significantly changes the windings resistances. Also presents the designing method for reducing power losses.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 June 1998

A. Pelikant and J. Turowski

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…

468

Abstract

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 17 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 August 1998

J. Turowski

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…

Abstract

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.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 17 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 2 March 2015

Patricia Penabad Durán, Paolo Di Barba, Xose Lopez-Fernandez and Janusz Turowski

The purpose of this paper is to describe a parameter identification method based on multiobjective (MO) deterministic and non-deterministic optimization algorithms to compute the…

Abstract

Purpose

The purpose of this paper is to describe a parameter identification method based on multiobjective (MO) deterministic and non-deterministic optimization algorithms to compute the temperature distribution on transformer tank covers.

Design/methodology/approach

The strategy for implementing the parameter identification process consists of three main steps. The first step is to define the most appropriate objective function and the identification problem is solved for the chosen parameters using single-objective (SO) optimization algorithms. Then sensitivity to measurement error of the computational model is assessed and finally it is included as an additional objective function, making the identification problem a MO one.

Findings

Computations with identified/optimal parameters yield accurate results for a wide range of current values and different conductor arrangements. From the numerical solution of the temperature field, decisions on dimensions and materials can be taken to avoid overheating on transformer covers.

Research limitations/implications

The accuracy of the model depends on its parameters, such as heat exchange coefficients and material properties, which are difficult to determine from formulae or from the literature. Thus the goal of the presented technique is to achieve the best possible agreement between measured and numerically calculated temperature values.

Originality/value

Differing from previous works found in the literature, sensitivity to measurement error is considered in the parameter identification technique as an additional objective function. Thus, solutions less sensitive to measurement errors at the expenses of a degradation in accuracy are identified by means of MO optimization algorithms.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 September 2015

Sándor Bilicz

The purpose of this paper is to discuss a numerically efficient simulation method for the study of the high-frequency behaviour of air-cored coils. The self-resonance phenomenon…

Abstract

Purpose

The purpose of this paper is to discuss a numerically efficient simulation method for the study of the high-frequency behaviour of air-cored coils. The self-resonance phenomenon of coils can be studied which is important, e.g., in wireless power transfer (WPT).

Design/methodology/approach

A full-wave and a quasi-stationary integral formulation is introduced. The integral equation is solved by using the Method of Moments. The complex impedance of the coil is calculated and studied in a wide frequency band.

Findings

The integral equation method is numerically efficient compared to finite element schemes, making possible its use in design optimisation problems.

Research limitations/implications

The present model can treat homogeneous media only. Future research will focus on the extension of the approach to heterogeneous media.

Practical implications

The method can be used in the design optimisation of WPT systems that apply magnetically coupled resonant coils.

Originality/value

The presented computation scheme is original. Integral equation schemes have not been used for coil modelling before, to the best of the author’s knowledge.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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