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1 – 10 of over 2000Gives 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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Yilun Li and Shiyou Yang
The temperature drop, especially in the edge of rolled steel in the hot rolling cooling has a catastrophic effect on the steel quality. The purpose of this paper is to study the…
Abstract
Purpose
The temperature drop, especially in the edge of rolled steel in the hot rolling cooling has a catastrophic effect on the steel quality. The purpose of this paper is to study the coupled eddy current-temperature field of a C-type edge induction heater to provide references for engineering applications and designs.
Design/methodology/approach
Three-dimensional finite element analysis (FEA) model of a C-type edge induction heater is developed. Especially, a numerical methodology to couple the eddy current and temperature fields is proposed for coupled eddy current and temperature problems involving movement components. FEA software ANSYS is used to solve the coupled eddy current and temperature fields. The heat loss from the eddy current fields is abstracted and processed, and taken as internal heat source in the analysis of the temperature field. The temperature distribution of the rolling steel is obtained.
Findings
The numerical results can predict exactly the temperature rise of the rolled steel by means of the edge induction heating system.
Practical implications
The proposed numerical methodology for coupling eddy current and temperature fields can be applied to engineering coupled eddy current and temperature problems involving movement components. Also, the developed model and method can be used in the analysis and design of the edge induction heating system.
Originality/value
A numerical methodology to couple eddy current and temperature field for solving multi-physics field problems involving movement components is proposed and implemented in available commercial software. A three-dimensional model of the C-type edge induction heat heater is developed. Finite element method is employed to study the coupled eddy current-thermal problem. A method to deal with the movement of the strip steel is proposed. The proposed methodology can be applied to other coupled eddy current-temperature field problem with moving components.
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Erich Schmidt, Georg Traxler‐Samek and Alexander Schwery
An accurate calculation of eddy current losses in the stator clamping parts of large hydro generators is a matter of particular interest with the initial design and the design…
Abstract
Purpose
An accurate calculation of eddy current losses in the stator clamping parts of large hydro generators is a matter of particular interest with the initial design and the design optimization because they can reach high values and produce local thermal hot‐spots due to the non‐linear magnetic behaviour of the clamping plate.
Design/methodology/approach
With a fully 3D approach of the generator pole pitch, both time‐harmonic and non‐linear transient finite element analyses are carried out for the eddy currents using a magnetic vector potential formulation.
Findings
With the introduction of a novel modelling strategy for the non‐linear clamping plate, the total eddy current losses evaluated from both analysis methods show a good agreement. Nevertheless, the time‐harmonic solution in comparison with the non‐linear transient solution yields different local eddy current distributions in particular with the clamping plate.
Research limitations/implications
The presented analyses use only the fundamental harmonic in the end region field. Further research will need to be carried out for the influence of the higher harmonics in the end region field and again the comparison of both analysis methods.
Practical implications
With the intention of including the numerical analyses with design review and design optimization of the generators, the results obtained from both analysis methods are compared regarding the total eddy current losses as well as their local distributions.
Originality/value
With a fully 3D approach of the generator pole pitch, second order pentahedral and hexahedral edge elements are introduced with both time‐harmonic and non‐linear transient eddy current finite element analyses.
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Belli Zoubida and Mohamed Rachid Mekideche
Reducing eddy current losses in magnets of electrical machines can be obtained by means of several techniques. The magnet segmentation is the most popular one. It imposes the…
Abstract
Purpose
Reducing eddy current losses in magnets of electrical machines can be obtained by means of several techniques. The magnet segmentation is the most popular one. It imposes the least restrictions on machine performances. This paper investigates the effectiveness of the magnet circumferential segmentation technique to reduce these undesirable losses. The full and partial magnet segmentation are both studied for a frequency range from few Hz to a dozen of kHz. To increase the efficiency of these techniques to reduce losses for any working frequency, an optimization strategy based on coupling of finite elements analysis and genetic algorithm is applied. The purpose of this paper is to define the parameters of the total and partial segmentation that can ensure the best reduction of eddy current losses.
Design/methodology/approach
First, a model to analyze eddy current losses is presented. Second, the effectiveness of full and partial magnet circumferential segmentation to reduce eddy loss is studied for a range of frequencies from few Hz to a dozen of kHz. To achieve these purposes a 2-D finite element model is developed under MATLAB environment. In a third step of the work, an optimization process is applied to adjust the segmentation design parameters for best reduction of eddy current losses in case of surface mounted permanent magnets synchronous machine.
Findings
In case of the skin effect operating, both full and partial magnet segmentations can lead to eddy current losses increases. Such deviations of magnet segmentation techniques can be avoided by an appropriate choice of their design parameters.
Originality/value
Few works are dedicated to investigate partial magnet segmentation for eddy current losses reduction. This paper studied the effectiveness and behaviour of partial segmentation for different frequency ranges. To avoid eventual anomalies related to the skin effect an optimization process based on the association of the finite elements analysis to genetic algorithm method is adopted.
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Masato Enokizono, Takashi Todaka and Shinya Urata
The purpose of this paper is to show formulation of a dynamic E&S model, which enables analysis of the effects of eddy currents under vector magnetic behavior in numerical…
Abstract
Purpose
The purpose of this paper is to show formulation of a dynamic E&S model, which enables analysis of the effects of eddy currents under vector magnetic behavior in numerical simulations and to demonstrate its usefulness.
Design/methodology/approach
When a magnetic flux waveform is distorted, effects of eddy currents increase due to harmonic flux components. In such a case, the result calculated by using the conventional E&S model does not agree with the measured one. The conventional E&S model is improved by considering magnetic flux waveform distortion. The harmonic components of the magnetic field strength waveform were estimated with the classical eddy current model.
Findings
In the verification of the dynamic E&S model, it was found that the magnetic field was suppressed by the effect of the eddy current. The conventional analysis overestimates the magnetic field, because the magnetic flux waveform cannot distort. In the magnetic characteristic analysis of a three‐phase transformer model core, the correlation between the eddy currents and the flux waveform distortion are clearly demonstrated.
Practical implications
Both magnetic flux and field strength waveform distortions can be represented in numerical simulations. The dynamic E&S model is very useful for magnetic core design, taking account of practical 2D vector magnetic properties.
Originality/value
The method presented in this paper enables effects of eddy currents in the magnetic characteristic analysis to be more accurately expressed, considering the 2D vector magnetic properties.
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Matteo Cacciola, Domenico Costantino, Francesco Carlo Morabito and Mario Versaci
The paper seeks to propose a specific approach based on Dynamic Analysis and Chaos Theory aiming to emphasize the differences into the eddy current signals obtained by related…
Abstract
Purpose
The paper seeks to propose a specific approach based on Dynamic Analysis and Chaos Theory aiming to emphasize the differences into the eddy current signals obtained by related non‐destructive tests, when the inspected specimens have flaws with different shapes.
Design/methodology/approach
Non‐linear eddy current analysis is very useful for flaw detection in many in‐service inspections. State‐of‐the‐art technologies allow one to define position and depth of defects, but the shape identification is still an open problem. In this paper, experimental data have been subjected to a dynamical analysis in order to relate the trend of eddy current signals to the shape of analyzed defect.
Findings
In particular, a dynamical reconstruction by means of recurrence plots (RPs) has been carried out in order to detect analogies and differentiations between different eddy current signals. Moreover, cross‐correlation between RPs of a reference benchmark and testing eddy current signals has been applied in order to emphasize a different dynamical behaviour and to detect a particular flaw's shape. In this way, a real‐time algorithm for defect shape classification has been performed.
Originality/value
Proposed approach is very interesting, and it is an innovation in non‐destructive testing procedures. In fact, the shape identification of a flaw is still an open challenge. The proposed approach, based on dynamic analysis, gives the key to solve this particular ill‐posed problem, by introducing a relation between the eddy current measurements and the shape of defect existing in the inspected specimen. Very interesting preliminary results have been obtained.
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The purpose of this paper is to supply a numerical analysis tool to solve eddy currents induced in nonlinear materials such as steel by boundary element method (BEM), and then…
Abstract
Purpose
The purpose of this paper is to supply a numerical analysis tool to solve eddy currents induced in nonlinear materials such as steel by boundary element method (BEM), and then apply it to design and analysis of power devices.
Design/methodology/approach
Utilizing integral formulas derived on the basis of rapid attenuation of the electromagnetic fields, the paper formulates eddy currents in steel. In the formulation, nonlinear terms are regarded as virtual sources, which are improved iteratively with the electromagnetic fields on the surface. The periodic electromagnetic fields are expanded in Fourier series and each harmonic is analyzed by BEM. The surface and internal electromagnetic fields are obtained numerically one after the other until convergence by the Newton‐Raphson method.
Findings
It is confirmed that this approach gives accurate solutions with meshes much larger than the skin depth and therefore is adequate to apply to a large‐scale application.
Research limitations/implications
The eddy current is formulated by utilizing the impedance boundary condition in order to meet a large‐scale application, and so solutions near the edge are poor. In the case of better solutions being required, some modifications are necessary.
Originality/value
To lessen computer memory consumption, the parallel component of the currents to the steel surface is analyzed as a 2D problem and the normal component is obtained from the parallel component. One 2D equation for one analyzing region is discretized by dividing the region into layers adaptively and then solved. Next, another is solved sequentially. This method gives a compatible numerical analysis tool with finite element method.
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Norio Takahashi, Hirofumi Shinagawa, Daisuke Miyagi and Yuhito Doi
The purpose of this paper is to examine the mechanism of the increase or decrease of eddy current loss of the segmented Nd‐Fe‐B sintered magnets without insulation, and the…
Abstract
Purpose
The purpose of this paper is to examine the mechanism of the increase or decrease of eddy current loss of the segmented Nd‐Fe‐B sintered magnets without insulation, and the effects of parameters on such a phenomenon are discussed.
Design/methodology/approach
The measured contact resistance is used in the finite element analysis.
Findings
It is shown that the eddy current loss in a magnet shows the peak value when the number of segments are increased at 40 kHz, but this property is changed at low frequency (10 kHz). Its tendency is changed by the contact resistance and the permeance (surrounding iron core).
Originality/value
The reason of a curious property of eddy current loss of segmented magnets is clearly explained by examining the eddy current distribution at various contact resistances.
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Katsumi Yamazaki, Yuki Yamato, Hisashi Mogi, Chikara Kaido, Akihito Nakahara, Kazuhiko Takahashi, Kazumasa Ide and Ken'ichi Hattori
The purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the…
Abstract
Purpose
The purpose of this paper is to investigate the distribution of in‐plane eddy currents in stator core packets of turbine generators, and to reveal the loss reduction effect by the slits in the stator teeth.
Design/methodology/approach
The in‐plane eddy currents are calculated by a 3D finite element method that considers lamination of electrical steel sheets. First, this method is applied to a simple model that simulates the stator core of the turbine generators. The calculated losses are compared with the measured losses in order to confirm the validity. Next, the same method is applied to a 250 MVA class turbine generator.
Findings
The validity of the calculation method is confirmed by the measurement of the simple model. By applying this method to the turbine generator, it is clarified that the considerable in‐plane eddy currents are generated not only at the end stator packets, but also at the top of the teeth of the interior packets due to the duct space. It is also clarified that the in‐plane eddy‐current loss decreases as nearly half by the slits of the stator teeth.
Originality/value
A reliable calculation method for the in‐plane eddy‐current loss in the turbine generators is developed. The results obtained by this method are valuable for the design of the generator from the viewpoint of heat conduction.
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Kota Watanabe and Hajime Igarashi
It is important to investigate large‐scale numerical analyses of electromagnetic fields in design processes of electromagnetic machines. Thus, faster solvers for eddy current…
Abstract
Purpose
It is important to investigate large‐scale numerical analyses of electromagnetic fields in design processes of electromagnetic machines. Thus, faster solvers for eddy current analyses are necessary. Parallel computation methods for linear solvers in electromagnetic field analyses have been investigated. These methods have gained importance due to the diffusion of PC clusters and multi‐core CPUs in recent years.
Design/methodology/approach
This paper discuses linear solvers for the finite element method in eddy current analyses on parallel computers. The preconditioned conjugate gradient method with overlapping domain decomposition is treated. Some techniques treated to improve the convergence was investigated.
Findings
The numerical results show that the overlapping effect results in good convergence in eddy current analyses.
Originality/value
The preconditioned conjugate gradient method with overlapping domain decomposition has been treated. The numerical results show that the overlapping method works more efficiently for eddy current analyses. Moreover, this method enables large‐scale analyses on popular computers such as PC clusters.
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