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Article
Publication date: 11 May 2020

Fabian Müller, Lucas Crampen, Thomas Henneron, Stephane Clénet and Kay Hameyer

The purpose of this paper is to use different model order reduction techniques to cope with the computational effort of solving large systems of equations. By appropriate…

102

Abstract

Purpose

The purpose of this paper is to use different model order reduction techniques to cope with the computational effort of solving large systems of equations. By appropriate decomposition of the electromagnetic field problem, the number of degrees of freedom (DOF) can be efficiently reduced. In this contribution, the Proper Generalized Decomposition (PGD) and the Proper Orthogonal Decomposition (POD) are used in the frame of the T-Ω-formulation, and the feasibility is elaborated.

Design/methodology/approach

The POD and the PGD are two methods to reduce the model order. Particularly in the context of eddy current problems, conventional time-stepping algorithms can lead to many numerical simulations of the studied problem. To simulate the transient field, the T-Ω-formulation is used which couples the magnetic scalar potential and the electric vector potential. In this paper, both methods are studied on an academic example of an induction furnace in terms of accuracy and computational effort.

Findings

Using the proposed reduction techniques significantly reduces the DOF and subsequently the computational effort. Further, the feasibility of the combination of both methods with the T-Ω-formulation is given, and a fundamental step toward fast simulation of eddy current problems is shown.

Originality/value

In this paper, the PGD is combined for the first time with the T-Ω-formulation. The application of the PGD and POD and the following comparison illustrate the great potential of these techniques in combination with the T-Ω-formulation in context of eddy current problems.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 2 May 2017

Guillaume Caron, Thomas Henneron, Francis Piriou and Jean-Claude Mipo

The purpose of this study is to determine the steady state of an electromagnetic structure using the finite element method (FEM) without calculation of the transient state. The…

78

Abstract

Purpose

The purpose of this study is to determine the steady state of an electromagnetic structure using the finite element method (FEM) without calculation of the transient state. The proposed method permits to reduce the computation time if the transient state is important.

Design/methodology/approach

In the case of coupling magnetic and electric circuit equations to obtain the steady state with periodic conditions, an approach can be to discretise the time with periodic conditions and to solve the equation system. Unfortunately, the computation time can be prohibitive. In this paper, the authors proposed to use the waveform relaxation method associated with the Newton method to accelerate the convergence.

Findings

The obtained results show that the proposed approach is efficient if the transient state is important. On the contrary, if the transient state is very low, it is preferable to use the classical approach, namely, the time-stepping FEM.

Research limitations/implications

The main limitation of the proposed approach is the necessity to evaluate or to know the time constant and consequently the duration of the transient state. Moreover the method requires some important memory resources.

Practical/implications

In the context of the use of the time-stepping FEM, one of the problems is the computation time which can be important to obtain the steady state. The proposed method permits avoidance of this difficulty and directly gives the steady state.

Social/implications

The proposed approach will permit to model and study the electromagnetic systems in the steady state, and particularly the transformers. Because of the gain in computing time, the use of optimisation techniques will be facilitated.

Originality/value

The novelty of this study is the proposal of the waveform relaxation–Newton method to directly obtain the steady state when applied to the three-phase transformer.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 8 May 2009

Jean‐Yves Roger, Emmanuel Vrignaud, Thomas Henneron, Abdelkader Benabou and Jean‐Pierre Ducreux

Coreplates in large generators may suffer from local short circuits. An accurate analysis is required to avoid these failures and detect them when occurring. The purpose of this…

318

Abstract

Purpose

Coreplates in large generators may suffer from local short circuits. An accurate analysis is required to avoid these failures and detect them when occurring. The purpose of this paper is to develop a lamination stack model compliant with interlamination default analysis.

Design/methodology/approach

An electromagnetic model should account for the eddy‐current in the lamination stack. To avoid the modelling of the insulation between the steel sheets, the authors propose to introduce a condition on the fields applied between each sheet. In the case of electric fault between several sheets, the conducting domain, i.e. the sheets, is not simply connected. Then, T‐Ω formulation must be adapted to solve such problem.

Findings

The model allows to account for thin plates, insulating layers and electrical faults in electromagnetic modeling of core plates. This study leads to a first evaluation of eddy current losses in steel laminations with defaults.

Research limitations/implications

The present study does not take into account thermal effects. The next step will consist in a magneto‐thermal computation. Thus, an electromagnetic finite element software must be coupled with a thermal one. An other improvement will rely on the study of actual situation in order to evaluate the accuracy of industrial sensors and to compare with measurements.

Originality/value

The paper develops a lamination stack model compliant with interlamination default analysis. As far as the authors know, this is the first study on 3D electromagnetic modeling.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 September 2012

Juliana Luísa Müller, Raphaël Romary, Abdelkader Benabou, Thomas Henneron, Francis Piriou, João Pedro Assumpção Bastos and Jean‐Yves Roger

Interlaminar short circuits in turbo generator stators can lead to local damage of the iron core. The purpose of this paper is to model an interlaminar short circuit diagnosis…

168

Abstract

Purpose

Interlaminar short circuits in turbo generator stators can lead to local damage of the iron core. The purpose of this paper is to model an interlaminar short circuit diagnosis test on an existing structure.

Design/methodology/approach

This work presents the modeling of short‐circuited laminations in a stator yoke of a turbo‐generator. A 3D finite element model, associated to a homogenization technique, is used to calculate the short‐circuit current. The diagnosis test known as El Cid has been modelled as well.

Findings

Calculation results are compared with the experiment. The same tendency has been observed both in experimental and numerical results.

Research limitations/implications

Additional calculations may be performed (parametric studies) in order to investigate El Cid measuring under different conditions (different material properties, fault position, size), which may lead to a better interpretation of the results.

Practical implications

Modelling of short circuit diagnosis tests under different conditions may help with the interpretation of measuring results, predicting the fault size/seriousness and location. So, only the concerned parts of the stator have to be disassembled and repaired/rebuilt.

Originality/value

It is not easy to model numerically a structure with a short circuit inside, since different dimensions are involved: the fault and the varnish between laminations are much smaller than the stator itself. Thus, homogenization techniques have been used to model the lamination stack region. The combination of this technique with the modelling of the El Cid test constitutes a tool to study this kind of fault and calculate its severity and location in a stator.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 14 August 2007

Jean V. Leite, Abdelkader Benabou, P.A. da Silva, N. Sadowski, Thomas Henneron, Stéphane Clénet, P. Kuo‐Peng, Francis Piriou and N.J. Batistela

The magnetic field strength measurement in a rotational single sheet tester (RSST) is quite difficult to achieve. In fact, flux leakage perturbs the field sensors as well as the…

451

Abstract

Purpose

The magnetic field strength measurement in a rotational single sheet tester (RSST) is quite difficult to achieve. In fact, flux leakage perturbs the field sensors as well as the homogeneity in the sample area. This paper seeks to present a 3D finite element (FE) model of an RSST taking into account a vector hysteresis model. The use of such model allows analyzing with accuracy the magnetic behavior of the system.

Design/methodology/approach

A vector hysteresis model, which is based on a general vectorization of the scalar Jiles‐Atherton model, is incorporated in a 3D FE code, with vector potential formulation.

Findings

The vector hysteresis model is validated by comparison with rotational experimental results. A good agreement is observed between calculations and measurements.

Originality/value

This paper shows that a classical scalar hysteresis model can be extended to take into account the magnetic vector behaviour and can be included in a 3D FE code. The methodology for the hysteresis including in the FE formulation is shown. This is useful for the design and analysis of an RSST prototype, improving the measurement techniques.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 July 2014

Irene Woyna, Erion Gjonaj and Thomas Weiland

– The purpose of this paper is to present a time domain discontinuous Galerkin (DG) approach for modeling wideband frequency dependent surface impedance boundary conditions.

197

Abstract

Purpose

The purpose of this paper is to present a time domain discontinuous Galerkin (DG) approach for modeling wideband frequency dependent surface impedance boundary conditions.

Design/methodology/approach

The paper solves the Maxwellian initial value problem in a computational domain, which is spatially discretized by the higher order DG method. On the boundary of the computational domain the paper applies a suitable impedance boundary condition (IBC). The frequency dependency of the impedance function is modeled by auxiliary differential equations (ADE).

Findings

The authors will study the resonance frequency and the Q factor of different types of cavity resonators including lossy materials. The lossy materials are modeled by means of IBCs. The authors will compare the results with analytical results, as well as numerical results obtained by direct calculations where lossy materials are included explicitly into the numerical model. Several convergence studies are performed which demonstrate the accuracy of the approach.

Originality/value

Modeling of frequency dependent boundary conditions in time domain with finite difference time domain method (FDTD) method is considered in numerous papers, as well as in frequency domain finite element method (FEM), and in a few papers also time domain FEM. However, FDTD method is only first order accurate and fails in modeling of complicated surfaces. FEM allows for high order accuracy, but time domain modeling is numerically extremely expensive. In frequency domain, broadband modeling of frequency dependent boundary conditions requires several simulations as opposed to the time domain, where a single simulation is needed. The time domain DG method proposed in this paper allows to overcome the difficulties. The authors introduce a broadband surface impedance formulation based on the ADE approach for the higher order DG method.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 August 2021

Chandani Khandelwal, Satish Kumar and Deepak Verma

The purpose of this paper is to contribute to the existing literature on financial risk disclosure by examining a sample of non-financial Indian companies listed on the Bombay…

673

Abstract

Purpose

The purpose of this paper is to contribute to the existing literature on financial risk disclosure by examining a sample of non-financial Indian companies listed on the Bombay stock exchange (BSE) to explore the degree of information about financial risks contained in their annual reports.

Design/methodology/approach

To study the financial risk disclosure of Indian companies, a sample of 206 non-financial companies has been derived from the top 500 listed companies at BSE. The method used in this study to analyze risk disclosure is content analysis. A total of 1,854 annual reports are scanned through software Nvivo-12 to find different types of risk words. Overall, risk disclosure, category wise risk disclosure, year-wise risk disclosure and sector-wise risk disclosure are assessed. The risk disclosure index is also computed.

Findings

The results show that there are some risk disclosure practices in Indian companies. No general pattern is observed. Companies are following vague method of risk disclosure. In the true sense, Indian companies are now started risk disclosure practices since 2018. This may be because of pressure from regulating bodies and stakeholders with greater detail about their financial risks.

Originality/value

This study is carried out for Indian non-financial companies. The paper adds to the literature relating to financial risk disclosure in developing countries.

Details

Qualitative Research in Financial Markets, vol. 13 no. 5
Type: Research Article
ISSN: 1755-4179

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Article
Publication date: 5 December 2016

Shamsun Nahar, Mohammad Azim and Christine Jubb

The purpose of this paper is to investigate the extent of risk disclosure and the factors determining this for all listed banks in Bangladesh.

2207

Abstract

Purpose

The purpose of this paper is to investigate the extent of risk disclosure and the factors determining this for all listed banks in Bangladesh.

Design/methodology/approach

Relying on a theoretical framework based on agency theory and the creation of a risk disclosure index (RDI) based on International Financial Reporting Standard (IFRS) 7, Basel II: market discipline, and prior literature, hand-collected data from the annual reports of all 30 banks traded on the Dhaka Stock Exchange over 2007-2012, creating 180 bank-year observations, are analysed.

Findings

The study suggests that implementation of IFRS 7 and Basel II: market discipline standards in a non-mandated environment raised the extent of risk disclosure in every category of financial institution risk (market, credit, liquidity, operational and equities). The effect can be attributed to regulatory concerns and voluntary adoption of international disclosure standards in the banking industry in Bangladesh. Specifically, whilst the determinants of disclosure vary across types of risk, the number of risk committees, leverage, company size, the existence of a risk management unit, board size and a Big4 affiliate auditor are significant determinants of at least one category of risk disclosure.

Research limitations/implications

The source of risk disclosures is limited to listed banks’ annual reports.

Practical implications

The RDI, developed in this paper, contributes to the literature by: first, quantifying the extent of each of five types of risk disclosure; and second, identifying the factors determining them. Stakeholders, particularly depositors and investors, can use this index to select or monitor their bank of interest.

Originality/value

The RDI was developed according to the most relevant standards – IFRS 7 and Basel II: market discipline, plus prior scholarly literature. This type of benchmarking has not been conducted to date in previous studies. Inferences about risk disclosure are based on archival data derived from all listed banks in a virtually unregulated environment. Further, the study complements the literature by providing support for the applicability of agency theory in investigating the level of risk disclosure by banks.

Details

Asian Review of Accounting, vol. 24 no. 4
Type: Research Article
ISSN: 1321-7348

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Article
Publication date: 13 November 2024

Harmandeep Singh

This study investigated the effect of voluntary cybersecurity risk reporting (VCRR) on corporate reputation. By examining the association between VCRR and corporate reputation…

129

Abstract

Purpose

This study investigated the effect of voluntary cybersecurity risk reporting (VCRR) on corporate reputation. By examining the association between VCRR and corporate reputation, this study aims to provide exploratory evidence of how cybersecurity risk is sensitive to a company’s image and reputation.

Design/methodology/approach

An automated content analysis of VCRR by 95 Bombay Stock Exchange-listed companies was undertaken using Python code. Signaling and legitimacy theories were adopted to interpret the findings, establishing whether VCRR was related to corporate reputation.

Findings

The results confirm that VCRR improves the corporate reputation in the financial market. The results also confirm the signalling and legitimacy theory that a company can manage reputational risks through higher voluntary risk disclosure.

Practical implications

The corporation’s managers can gain insights from the study’s findings and proactively address cybersecurity risks through strategic disclosure and management practices. In addition, organizations can recognize that investors value transparency and establish a positive reputation for those who communicate openly.

Social implications

A significant association between VCRR and corporate reputation implies that such disclosures enhance trust and transparency in the business sector and induce security and accountability among investors engaging with the company.

Originality/value

To the best of the authors’ knowledge, this study is the first that empirically investigates this issue and adds to the international literature a new explanatory variable, corporate reputation, to explain VCRR practices.

Details

Meditari Accountancy Research, vol. 33 no. 1
Type: Research Article
ISSN: 2049-372X

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Article
Publication date: 4 April 2017

Ridhima Saggar and Balwinder Singh

This study aims to measure the extent of voluntary risk disclosure and examine the relationship between corporate governance firm level quality in the form of board…

4094

Abstract

Purpose

This study aims to measure the extent of voluntary risk disclosure and examine the relationship between corporate governance firm level quality in the form of board characteristics and ownership concentration’s impact on risk disclosure in the annual reports of Indian listed companies.

Design/methodology/approach

The method adopted in this study is automated content analysis, which is applied to a sample of 100 listed Indian non-financial companies to find out the extent of risk disclosure. Further, multiple linear regressions have been applied to find out the relationship between corporate governance firm level quality in the form of board characteristics, ownership concentration and risk disclosure.

Findings

The findings reveal that the total number of positive risk keywords surpasses negative risk keywords disclosure. The corporate governance mainsprings, namely, board size and gender diversity have a positively significant effect on risk disclosure, whereas ownership concentration in the hands of the largest shareholder insignificantly affects risk disclosure, but identity of the largest shareholder having ownership concentration negatively affects disclosure of risk information in the case of Indian promoter body corporate, foreign promoter body corporate and non-institutions in comparison to family ownership.

Research limitations/implications

This study relied on a set of 39 risk keywords for measuring the extent of risk disclosure. Further, it uses a sample of 100 companies to examine the effect of corporate governance on risk disclosure at one point of time. However, a longitudinal study can help in understanding risk disclosure adopted by Indian listed companies in a better manner.

Practical implications

The findings have implications for regulatory bodies such as the Securities and Exchange Board of India, which needs to strengthen corporate governance norms with respect to board characteristics and keep a check on ownership concentration for improving risk disclosure by companies.

Originality/value

To best of the authors’ knowledge, this study is a preliminary attempt linking two research lines in India, that is, corporate risk disclosure and corporate governance quality in the form of board characteristics and ownership concentration. The study identifies corporate governance firm level qualities which lead to divulgation of risk information by the companies pointing towards strengthening of regulatory regime in the country for improved corporate governance regulations adopted by listed companies.

Details

Managerial Auditing Journal, vol. 32 no. 4/5
Type: Research Article
ISSN: 0268-6902

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