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Article
Publication date: 1 June 2001

M. Kaltenbacher, S. Reitzinger, M. Schinnerl, J. Schöberl and H. Landes

The focus of this paper is on the efficient numerical computation of 3D electromagnetic field problems by using the finite element (FE) and multigrid (MG) methods. The magnetic…

547

Abstract

The focus of this paper is on the efficient numerical computation of 3D electromagnetic field problems by using the finite element (FE) and multigrid (MG) methods. The magnetic vector potential is used as the field variable and the discretization is performed by Lagrange (nodal) as well as Ne´de´lec (edge) finite elements. The resulting system of equations is solved by applying a preconditioned conjugate gradient (PCG) method with an adapted algebraic multigrid (AMG) as well as an appropriate geometric MG preconditioner.

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

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Article
Publication date: 15 November 2011

Erich Schmidt

The purpose of this paper is to discuss the state of the art of finite element analysis of electrical machines and transformers. Electrical machines and transformers are prime…

929

Abstract

Purpose

The purpose of this paper is to discuss the state of the art of finite element analysis of electrical machines and transformers. Electrical machines and transformers are prime examples of multi‐physical systems involving electromagnetics, thermal issues, fluid dynamics, structural mechanics as well as acoustic phenomena. An accurate operational performance with different electrical and mechanical load situations is more and more evaluated using various numerical analysis methods including the couplings between the various physical domains. Therefore, numerical analysis methods are increasingly utilized not only for the verification of contractual values of existing machines, but also for the initial design process and for the design optimization of new machines.

Design/methodology/approach

The finite element method is the most powerful numerical analysis method for such multi‐physical devices. Since optimizations with respect to the overall performance and also the total manufacturing costs will become more important, the utilization of coupled multi‐physical analyses is of growing interest. For the fast and powerful application of this numerical analysis method, special attention should be given to the requirements of these electromagnetic devices.

Findings

Various methods of coupling the different physical domains of multi‐field finite element analyses are described. Thereby, weakly coupled cascade algorithms can be used with most problems in the field of electrical machines and transformers. On the other hand, a prime objective is to derive comprehensive, multi‐physical simulation models which are easily incorporated into design tools used by engineering professionals.

Research limitations/implications

The development of robust and reliable computer‐aided tools for an optimal design of multi‐physical devices such electrical machines and transformers has to argue about the best possible coupling of various simulation methods. Special consideration shall be paid more and more to a treatment of uncertainties and tolerances by means of statistical and probabilistic approaches.

Originality/value

The paper discusses state of the art of finite element analyses of the mentioned devices. Various optimized methods of modelling and analysis concerning the repetitive structure of electrical machines for electromagnetic analyses are compared with their advantages and drawbacks. Further, various methods of coupling the different domains of multi‐field analyses in case of electrical machines and transformers are described.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 6
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 December 2005

Gilbert Ahamer

Aims to examine a negotiation‐oriented and partly web‐based game “Surfing Global Change” (SGC) invented by the author based on didactics of self‐managed learning and successfully…

814

Abstract

Purpose

Aims to examine a negotiation‐oriented and partly web‐based game “Surfing Global Change” (SGC) invented by the author based on didactics of self‐managed learning and successfully implemented in WebCT.

Design/methodology/approach

Along three historic generations of web‐based teaching (WBT), the key functionalities of any platform (content, discussion and evaluation) are perceived to be utilized in a characteristic way depending on the prevalent didactic concepts. The changing roles of teacher and students are highlighted using the example of SGC Level 3, where students assess one another's competence, each trying to outdo the others in controversial arguments

Findings

The outlay of Surfing Global Change aims at accomplishing sustainable results for complex themes. Thus SGC sets out to weigh out competition vs consensus, self‐study vs team work, emphasizing one's own standpoint vs readiness to compromise, differentiation into details vs integration into a whole. SGC hence wants to mirror professional realities along five interactive game levels: learn content and pass quizzes; write and reflect a personal standpoint; win with a team in a competitive discussion; negotiate a complex consensus between teams; integrate views when recognizing and analyzing global long‐term trends.

Research limitations/implications

Some interactive assessment functionalities are still missing in current platforms.

Practical implications

In advanced university courses the negotiation game SGC was repeatedly used as a procedural shell for interdisciplinary themes.

Originality/value

The paper shows that a “communicative space” is created by utilising mainstream web platform technology, capable of transposing visions of “progressive education”. The definition of three generations of WBT allows for a functional differentiation in the styles of using web‐based tools.

Details

Campus-Wide Information Systems, vol. 22 no. 5
Type: Research Article
ISSN: 1065-0741

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Article
Publication date: 8 March 2011

Michael Ertl and Manfred Kaltenbacher

The fast and flexible development of fast switching electromagnetic valves as used in modern gasoline engine demands the availability of efficient and accurate simulation tools…

878

Abstract

Purpose

The fast and flexible development of fast switching electromagnetic valves as used in modern gasoline engine demands the availability of efficient and accurate simulation tools. The purpose of this paper is to provide an enhanced computational scheme of these actuators including all relevant physical effects of magneto‐mechanical systems and including contact mechanics.

Design/methodology/approach

The finite element (FE) method is applied to efficiently solve the arising coupled system of partial differential equations describing magneto‐mechanical systems. The algorithm for contact mechanics is based on the cross‐constraint method using an energy‐ and momentum‐conserving time‐discretisation scheme. Although solving separately for the electromagnetic and mechanical system, a strong coupling is ensured within each time step by an iterative process with stopping criterion.

Findings

The numerical simulations of the full switching cycle of an electromagnetic direct injection valve, including the bouncing during the closing state, are just feasible with an enhanced and robust mechanical contact algorithm. Furthermore, the solution of the nonlinear electromagnetic and mechanical equations needs a Newton scheme with a line search scheme for the relaxation of the step size.

Originality/value

The paper provides a numerical simulation scheme based on the FE method, which includes all relevant physical effects in magneto‐mechanical systems, and which is robust even for long‐term contact periods with multitude re‐opening phases.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 27 January 2022

Matthias Kowalski, Martin Hanke and Christian Kreischer

Resolving eddy currents in three dimensions with finite elements, especially in geometrically complex structures, is very time consuming. Notable additional efforts will be…

73

Abstract

Purpose

Resolving eddy currents in three dimensions with finite elements, especially in geometrically complex structures, is very time consuming. Notable additional efforts will be required, if these eddy currents are influenced by magnetic fields arising from larger parts or range over widespread regions. The purpose of this article is to present a new sub-modelling simulation technique, based on the finite-element approach. This method offers remarkable advantages for solving this type of problems.

Design/methodology/approach

A novel sub-modeling technique is developed for the finite-element method addressing this problem by dividing the process into two steps: firstly, a simulation of a “source”-model is carried out providing magnetic field distributions within the entire domain neglecting local eddy current effects and without modeling it in full detailed geometry. A subsequent “sub”-model comprises only the region of interest in higher resolution and is solved while being constrained with boundary conditions derived from the previous source-model. An implementation in ANSYS Mechanical is carried out with the objective to validate finite-element simulation against measurement results.

Findings

The proposed simulation technique performs robustly and time efficiently. Applying this method to an end-region of a turbogenerator allows comparisons with test data of this region for validation purposes. The comparison between measured and simulated radial flux densities shows good correspondence.

Originality/value

This work is novel in many aspects: a new technique for three-dimensional (3D) finite-element method using edge-elements is introduced. To the best of the authors’ knowledge, for the first time, these 3D sub-models are compared against measurement results of an electric machine with net currents. Leveraged from this work, detailed analyses of eddy current phenomena under influences of external magnetic fields can be investigated in higher detail within shorter calculation times.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 41 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 September 2015

Yoshifumi Okamoto, Akihisa Kameari, Koji Fujiwara, Tomonori Tsuburaya and Shuji Sato

– The purpose of this paper is the realization of Fast nonlinear finite element analysis (FEA).

343

Abstract

Purpose

The purpose of this paper is the realization of Fast nonlinear finite element analysis (FEA).

Design/methodology/approach

Nonlinear magnetic field analysis is achieved by using Newton-Raphson method implemented by relaxed convergence criterion of Krylov subspace method.

Findings

This paper mathematically analyzes the reason why nonlinear convergence can be achieved if the convergence criterion for linearized equation is relaxed.

Research limitations/implications

The proposed method is essential to reduce the elapsed time in nonlinear magnetic field analysis of quasi-stationary field.

Practical implications

The proposed method is able to be extended to not only static field but also time domain FEA strongly coupled with circuit equation.

Social implications

Because the speedup of performance evaluation of electrical machines would be achieved using proposed method, the work efficiency in manufacturing would be accelerated.

Originality/value

It can be seen that the nonlinear convergence can be achieved if the convergence criterion for linearized equation is relaxed. The verification of proposed method is demonstrated using practical nonlinear magnetic field problem.

Details

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

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Book part
Publication date: 22 November 2012

Margarida Romero

This chapter aims to advance in the analysis of the learner engagement and performance in the use of computer-based games, also known as Serious Games (SG). The chapter describes…

Abstract

This chapter aims to advance in the analysis of the learner engagement and performance in the use of computer-based games, also known as Serious Games (SG). The chapter describes the learner engagement in relation to the use of SG in individual and collaborative learning activities. The SG learning experience considers the learner engagement in the individual activities observed through their real use of the game and their perceptions of the usefulness of the game and the time-on-task spent. The collaborative use of SG considers additional mechanisms of engagement related to the intragroup relationships – relationships within the same members of the group – and intergroup relationships – relationships between the different groups – such is the degree of interdependence and the degree of competition in the game. The state of the art in the learner engagement in the use of individual and collaborative SG is based in a literature review, and completed by the study case of the individual and the collaborative use of the eFinance Game or eFG (MetaVals) in ESADE Business & Law School. We analyse the current challenges and transfer the knowledge created through the eFG case for the practitioners aiming to promote learners’ engagement through the use of individual and collaborative SG.

Details

Increasing Student Engagement and Retention Using Immersive Interfaces: Virtual Worlds, Gaming, and Simulation
Type: Book
ISBN: 978-1-78190-241-7

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Article
Publication date: 1 June 2005

Kota Watanabe and Hajime Igarashi

This paper discusses the robustness of the algebraic multigrid (AMG) method as well as geometric multigrid (GMG) method against mesh distortion in edge‐based finite element…

215

Abstract

Purpose

This paper discusses the robustness of the algebraic multigrid (AMG) method as well as geometric multigrid (GMG) method against mesh distortion in edge‐based finite element analysis.

Design/methodology/approach

Analyzes a simple magnetostatic problem, in which the model consists of a cubic iron and the surrounding air region. Prepares three meshes which have same number of elements to evaluate the robustness of multigrid against the distortion of mesh.

Findings

The AMG method is shown to be more robust against mesh distortion than the GMG method.

Originality/value

Shows that the AMG is more robust than the GMG. This result is of practical interest to the researchers in this field.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 June 2001

Bernhard Weiß and Oszkár Bíró

A geometric multigrid (MG) method for the efficient solution of 3D non‐linear magnetostatic field problems is presented. A finite element method (FEM) with edge elements is used…

435

Abstract

A geometric multigrid (MG) method for the efficient solution of 3D non‐linear magnetostatic field problems is presented. A finite element method (FEM) with edge elements is used to describe the magnetic vector potential. A numerical example is presented to demonstrate the efficiency of the MG method not only for linear, but also for non‐linear problems.

Details

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

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Article
Publication date: 9 September 2013

Andreas Hauck, Michael Ertl, Joachim Schöberl and Manfred Kaltenbacher

The purpose of this paper is to propose a solution strategy for both accurate and efficient simulation of nonlinear magnetostatic problems in thin structures using higher order…

168

Abstract

Purpose

The purpose of this paper is to propose a solution strategy for both accurate and efficient simulation of nonlinear magnetostatic problems in thin structures using higher order finite element methods. Special interest is put in the investigation of the step-lap joints of transformer cores, with a focus on the spatial resolution of the field quantities.

Design/methodology/approach

The usage of hierarchical finite elements of higher order makes it possible to adapt the local accuracy in different spatial directions in thin steel sheets. Due to explicit representation of gradients in the basis functions, a simple Schwarz-type block preconditioner with a conjugate gradient solver can efficiently solve the arising algebraic system. By adapting the block size automatically according to the aspect ratio, deterioration of convergence in case of thin elements can be prevented. The resulting Newton scheme is accelerated utilizing the hierarchical splitting in a two-level scheme, where an initial guess is computed on a coarse sub-space.

Findings

Compared to an isotropic choice of polynomial order for the basis functions, significant runtime and memory can be saved in the simulation of thin structures without losing accuracy. The iterative solution scheme proves to be robust with respect to the polynomial order, even for aspect ratios of 1:1000 and anisotropies in two directions. An additional saving in runtime and Newton iterations can be achieved by solving the nonlinear problem initially on the lowest order basis functions only and projecting the solution to the complete space as starting value, analogous to a full multigrid scheme.

Originality/value

Within the presented solution strategy, especially the anisotropic block preconditioner and the accelerated Newton scheme based on the two-level splitting constitute a novel contribution. They provide building blocks, which can be utilized for other types of magnetic field problems like transient nonlinear problems or hysteresis modeling as well.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 32 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

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