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…
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.
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F. Rapetti, L. Santandrea, F. Bouillault and A. Razek
This paper deals with the numerical simulation of eddy current distributions in non‐stationary geometries with sliding interfaces. We study a system composed of two solid parts: a…
Abstract
This paper deals with the numerical simulation of eddy current distributions in non‐stationary geometries with sliding interfaces. We study a system composed of two solid parts: a fixed one (stator) and a moving one (rotor) which slides in contact with the former. We also consider a two‐dimensional mathematical model based on the transverse electric formulation of the eddy current problem whose approximation is performed via the mortar element method combined with the standard linear finite element discretization in space and an implicit first order Euler scheme in time. Numerical results underline the influence of the rotor movement on the current distribution and give an estimate of the power losses with respect to the rotor angular speed.
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G.B. Kumbhar, S.V. Kulkarni, R. Escarela‐Perez and E. Campero‐Littlewood
This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective…
Abstract
Purpose
This paper aims to give a perspective about the variety of techniques which are available and are being further developed in the area of coupled field formulations, with selective bibliography and practical examples, to help postgraduate students, researchers and designers working in design or analysis of electrical machinery.
Design/methodology/approach
This paper reviews the recent trends in coupled field formulations. The use of these formulations for designing and non‐destructive testing of electrical machinery is described, followed by their classifications, solutions and applications. Their advantages and shortcomings are discussed.
Findings
The paper gives an overview of research, development and applications of coupled field formulations for electrical machinery based on more than 160 references. All landmark papers are classified. Practical engineering case studies are given which illustrate wide applicability of coupled field formulations.
Research limitations/implications
Problems which continue to pose challenges to researchers are enumerated and the advantages of using the coupled‐field formulation are pointed out.
Practical implications
This paper gives a detailed description of the application of the coupled field formulation method to the analysis of problems that are present in different electrical machines. Examples of analysis of generators and transformers with this formulation are presented. The application examples give guidelines for its use in other analyses.
Originality/value
The coupled‐field formulation is used in the analysis of rotational machines and transformers where reference data are available and comparisons with other methods are performed and the advantages are justified. This paper serves as a guide for the ongoing research on coupled problems in electrical machinery.
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O.J. Antunes, J.P.A. Bastos and N. Sadowski
The purpose of this paper is to compare torque calculation methods when a non‐conforming movement interface is implemented by means of Lagrange multipliers.
Abstract
Purpose
The purpose of this paper is to compare torque calculation methods when a non‐conforming movement interface is implemented by means of Lagrange multipliers.
Design/methodology/approach
The following methods are here used for computing the torque in a synchronous machine and in a switched reluctance motor: Arkkio's method (AM), local Jacobian matrix derivative (LJD) method, Maxwell stress tensor method (MST) and co‐energy variation method.
Findings
This paper shows that, the numerical stability produced by Lagrange multipliers yields a stable torque result, even in thin airgap machines if AM, LJD method or MST method are used.
Originality/value
This work presents a comparative study to indicate the performance of the most commonly used torque calculation methods, when a non‐conforming technique is used, considering a small displacement of the rotor, which is necessary for dynamic cases or coupling with circuit.
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Bernd Flemisch, Barbara Wohlmuth, Francesca Rapetti and Yvon Maday
We present a method for the simulation of the dynamical behavior of a coupled magneto‐mechanical system given in terms of a conductor moving through an electromagnetic field.
Abstract
Purpose
We present a method for the simulation of the dynamical behavior of a coupled magneto‐mechanical system given in terms of a conductor moving through an electromagnetic field.
Design/methodology/approach
For the magnetic part, we consider a model based on an electric vector and a magnetic scalar potential, whereas the mechanical part is modelled by the equation of a rigid body motion. A weak coupling is employed: at each time step the resulting forces are calculated yielding the new displacement of the conductor.
Findings
Numerical results are given for the simulation of an electromagnetic brake with axisymmetric geometry. They indicate that the proposed method is especially well suited for eddy current problems involving moving conductors.
Research limitations/implications
Further research should be undertaken toward the application of the proposed method to real 3D problems.
Originality/value
The spatial discretization of the problem relies on the use of two independent triangulations to approximate the two involved potentials. Whereas the scalar magnetic potential is discretized by means of nodal H1‐conforming finite elements on a grid covering the global computational domain, the vector electric potential is approximated by Hcurl‐conforming edge elements on another grid only covering the conductor. The coupling between the two grids is accomplished via the mortar finite element method. At each time step, only the coupling matrix has to be reassembled, all other involved matrices remain the same. Moreover, no remeshing is necessary when the conductor changes its position. The paper should be valuable for any researcher interested in the numerical simulation of eddy current problems.
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Herbert De Gersem, Mariana Ion, Markus Wilke, Thomas Weiland and Andrzej Demenko
To propose trigonometric interpolation in combination with both sliding‐surface and moving‐band techniques for modelling rotation in finite‐element electrical machine models. To…
Abstract
Purpose
To propose trigonometric interpolation in combination with both sliding‐surface and moving‐band techniques for modelling rotation in finite‐element electrical machine models. To show that trigonometric interpolation is at least as accurate and efficient as standard stator‐rotor coupling schemes.
Design/methodology/approach
Trigonometric interpolation is explained concisely and put in a historical perspective. Characteristic drawbacks of trigonometric interpolation are alleviated one by one. A comparison with the more common locked‐step linear‐interpolation and mortar‐element approaches is carried out.
Findings
Trigonometric interpolation offers a higher accuracy and therefore can outperform standard stator‐rotor coupling techniques when equipped with an appropriate iterative solver incorporating Fast Fourier Transforms to reduce the higher computational cost.
Originality/value
The synthetic interpretation of trigonometric interpolation as a spectral‐element approach in the machine's air gap, the efficient iterative solver combining conjugate gradients with Fast Fourier Transforms. The unified application to both sliding‐surface and moving‐band techniques.
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Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields…
Abstract
Introduces the fourth and final chapter of the ISEF 1999 Proceedings by stating electric and magnetic fields are influenced, in a reciprocal way, by thermal and mechanical fields. Looks at the coupling of fields in a device or a system as a prescribed effect. Points out that there are 12 contributions included ‐ covering magnetic levitation or induction heating, superconducting devices and possible effects to the human body due to electric impressed fields.
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Mariana Ion, Herbert De Gersem, Markus Wilke and Thomas Weiland
To propose trigonometric interpolation in combination with the sliding‐surface technique for modeling rotation in electrical machine models discretised by the finite integration…
Abstract
Purpose
To propose trigonometric interpolation in combination with the sliding‐surface technique for modeling rotation in electrical machine models discretised by the finite integration technique (FIT).
Design/methodology/approach
Locked‐step, linear and trigonometric interpolation techniques are developed for coupling the stator and rotor model parts of an electrical machine model.
Findings
Linear and trigonometric interpolation should be preferred over the locked‐step approach. Three‐machine models with sliding‐surface coupling discretised by the FIT result in efficient and reliable models.
Originality/value
The introduction of sliding‐surface techniques in the FIT, the trigonometric interpolation used in combination, the application of the FIT for simulating electrical machines.
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P. Alotto, A. Bertoni, I. Perugia and D. Scho¨tzau
The capability of discontinuous finite element methods of handling non‐matching grids is exploited in the simulation of rotating electrical machines. During time stepping, the…
Abstract
The capability of discontinuous finite element methods of handling non‐matching grids is exploited in the simulation of rotating electrical machines. During time stepping, the relative movement of two meshes, consistent with two different regions of the electrical device (rotor and stator), results in the generation of so‐called hanging nodes on the slip surface. A discretisation of the problem in the air‐gap region between rotor and stator, which relies entirely on finite element methods, is presented here. A discontinuous Galerkin method is applied in a small region containing the slip surface, and a conforming method is used in the remaining part.
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Xiaodong Shi, Yvonnick Le Menach, Jean‐Pierre Ducreux and Francis Piriou
To compare slip surface and moving band techniques for modelling movement in 3D with FEM.
Abstract
Purpose
To compare slip surface and moving band techniques for modelling movement in 3D with FEM.
Design/methodology/approach
The slip surface and moving band techniques are used to model the rotation of electrical machines in 3D with FEM. The proposed techniques are applied to a permanent magnet synchronous machine. The comparison is carried out at no‐load for the electromotive force (EMF) and the cogging torque. The torque is also compared for the short circuit case.
Findings
For both the locked‐step and moving band approaches there is no difficulty in establishing the scalar potential and potential vector formulations. However, if step displacement is not equal to the mesh step, the results can show numerical irregularities. Some improvements have been proposed in order to limit this problem.
Originality/value
The results of the EMF and the cogging torque are improved.