Search results

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.

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.

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.

The numerical results can predict exactly the temperature rise of the rolled steel by means of the edge induction heating system.

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.

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.

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.

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.

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.

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.

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.

The purpose of this study is to find out the influence degree of harmonic current on the generator operating parameters. In practical operation of the salient-pole synchronous generator, the heat generated by eddy current loss may lead to the breaking of damper winding, and the damper winding is a key component for ensuring the reliable operation of generators. Therefore, it is important to study the distribution characteristics and the influence factors of eddy current loss. Taking a 24-MW bulb tubular turbine generator as a reference, the influence factors that affect the eddy current loss of damper winding are analyzed.

A two-dimensional (2-D) electromagnetic field model of the generator is established, and the correctness of the model is verified by comparing simulation results and experiment data. The eddy current losses of damper winding in various conditions are calculated by using the finite element method.

It is identified that the cogging effect, pole shoe magnetic saturation degree, pole arc coefficient and armature reaction are the main factors that affect the eddy current loss of the generator rotor. When the generator is installed with magnetic slot wedges, the distribution characteristic of eddy current loss is obtained through the study of the eddy current density distributions in the damper bars. The variations of eddy current losses with time are gained when the generator has different permeability slot wedges, pole arc coefficients and pole shoe magnetic saturation degrees.

The study of this paper provides a theoretical reference for the design and optimization of bulb tubular turbine generator structure.

The research can help enhance the understanding of eddy current distribution characteristics and influence factors of eddy current loss in bulb tubular turbine generator.

Eddy currents are inevitable in magnetic resonance imaging (MRI) systems. These currents are mainly induced by gradient fields. This study aims to propose a fast analytical method to calculate eddy currents induced by frequently switching gradient fields in a traditional C-shape MRI system.

Fourier decomposition and magnetic vector potentials were used to calculate the eddy currents. Calculations with the proposed analytical method revealed the spatial distribution and temporal evolution of eddy currents.

Calculation and Maxwell simulation results were consistent. The agreement between calculation and simulation results indicates that increasingly sophisticated structures could be developed. The calculated results could guide the design of improved gradient coils.

Eddy currents induced by gradient current are decomposed into currents induced by each time-harmonic component, and then adding them together to obtain complete contribution of the eddy current. The analytical method was used to characterize the properties of symmetric and asymmetric eddy currents induced by gradient coils in MRI systems. The analytical method can be used to improve the gradient shield during the design of the gradient coil in the MRI system.

Taking a 2,000 r/min 10 kW permanent magnet motor as an example, the purpose of this paper is to study the influence of driving modes on the performance of permanent magnet motor at limit conditions, and researched the variation mechanism of motor performance influenced by different driving modes.

A two-dimensional electromagnetic field model of the permanent magnet motor was established, and a rectangular-wave driving circuit was built. By using the finite element method, the electromagnetic field, current, harmonic content and eddy current loss were calculated when the motor operated at rated load and limit load. On the basis of the motor loss calculation, the temperature field of the motor operating at rated condition and limit condition was researched, and the factors that influence motor limit overload capacity were analyzed. By analyzing the motor loss variation at different load conditions, the change mechanism of the motor temperature field was determined further. Combined with the related experiments, the correctness of the above analysis was verified.

Permanent magnet synchronous motor (PMSM) driven by sine wave is better compared with brushless direct current motor (BLDCM) driven by rectangular wave in reducing the magnetic field harmonics, motor losses and optimizing the temperature distribution in the motor. The method driven by sine wave could improve the motor output performance including the motor efficiency and the motor overload capacity. The winding temperature is the most important factor that limits the output capability of PMSM operating for a long time. However, because of the large rotor eddy current losses, the permanent magnet temperature is the most important factor that limits the output capability of BLDCM operating for a long time.

The influence of driving modes on the motor magnetic field, losses and temperature distribution, efficiency and overload capacity was determined, and the influence mechanism was also analyzed. Combined with the analysis of the electromagnetic and temperature fields, the advantages of different driving modes were presented. This study could provide an important basis for the design of permanent magnet motors with different driving modes, and it also provides reference for the application of permanent magnet motor.

This paper presents the influence of driving modes on permanent magnet motors. The limit output capacity of the motor with different driving modes was studied, and the key factors limiting the motor output capability were obtained.

Presents the calculation of the induced eddy currents in the conducting parts of transverse flux machines. Compared to conventional machines the transverse flux machine has a bigger torque, both with respect to volume and weight. For this reason, it is especially suited for direct drive applications in electric vehicles and railways. The main focus in this paper is the investigation of the different loss mechanisms caused by the sinusoidal stator current and the movement of the permanent magnet excited rotor. A 3D FEM solver with a \over right arrow A−\over right arrow A, \over right arrow T potential formulation is used in combination with edge elements. The time stepping procedure, with special focus on the displacement between stator and rotor mesh for the velocity effect, is explained in detail. The eddy current density distribution in the different parts of the machine is shown.

A 3-D analytic modeling technique for calculating the eddy current distribution, force and power loss in a conductive plate of finite width and thickness is presented. The derived equations are expressed in a general form so that any magnetic source can be utilized. The model assumes the length of the conductive plate is large and the thickness of the plate is thin but not negligible. The paper aims to discuss these issues.

The conducting and non-conducting regions are formulated in terms of decoupled magnetic vector potential components. In order to accurately compute the eddy current fields and forces the source field only needs to be applied on the surface of the conducting plate. The primary focus is on reducing the eddy current computational time.

The accuracy of the presented approach is verified by utilizing a magnetic rotor that has both a rotational and translational motion. The proposed method is computationally efficient and its accuracy is validated using the finite element method.

The conducting plate thickness is assumed to be thin (but not negligible), and this enables the field interaction through the edge of the plate to be neglected. The lateral force is not calculated in the proposed approach.

The calculation procedure presented is computationally fast and therefore this can enable the 3-D eddy current forces to be computed in near real-time.

This paper presents a fully 3-D analytic based eddy current formlation for computing the eddy current fields and forces in a conducting plate of finite thickness and finite width. The modeling approach is shown to be computationally accurate and relatively fast.

The purpose of this paper is to use numerical methods and modelling to estimate the effect of a passive, metallic (conducting) implant on eddy currents distribution in a human knee model. There exists a concern among wearers of such implants that they alter electromagnetic field (eddy currents) significantly and there is a need for standardization of that problem.

The numerical model of a human knee has been built on the base of Visual Human Project and electromagnetic field calculations were carried out using Meep FDTD engine. In total, two scenarios have been considered: the knee model with and without a metallic implant. The knee implant model has been prepared as the knee model with overestimated electrical parameters of bone tissues by titanium metal. Alternating eddy current distribution has then been evaluated for both models using FDTD low frequency algorithm.

The highest values of eddy currents occurred on the interface between skin and muscle tissues when the model without an implant is considered. However, when the bone tissues have been replaced with titanium metal, the highest values have occurred in the implant (about 100 times higher than the previous one). This means that an implant can be heated by external electromagnetic fields and that the location of the highest values of eddy currents can be shifted to the proximity of the implant. Moreover, one should realize that in this model the implant is like a knee bone with all anatomical details. It has emerged from this that the implant's shape and size are essential when evaluating its effect on eddy currents distribution.

The interaction of electromagnetic field with implants should be generally further investigated, at least for the presumable worst cases. Such investigation has already been done by some researches but they have been devoted to radio frequencies. The authors believe that the presented research will be helpful in the standardization process, when talking about low frequency electromagnetic field.

The presented methodology can be used in the development of computer aid diagnosis systems. Overestimation of electrical parameters of some parts of the model allows us to predict the distribution of electromagnetic field in the model under investigation very quickly. The results presented in the paper can be used during the standardization process.

The purpose of this paper is to describe a semi-analytical modeling technique to predict eddy currents in three-dimensional (3D) conducting structures with finite dimensions. Using the developed method, power losses and parasitic forces that result from eddy current distributions can be computed.

In conducting regions, the Fourier-based solutions are developed to include a spatially dependent conductivity in the expressions of electromagnetic quantities. To validate the method, it is applied to an electromagnetic configuration and the results are compared to finite element results.

The method shows good agreement with the finite element method for a large range of frequencies. The convergence of the presented model is analyzed.

Because of the Fourier series basis of the solution, the results depend on the considered number of harmonics. When conducting structures are small with respect to the spatial period, the number of harmonics has to be relatively large.

Because of the general form of the solutions, the technique can be applied to a wide range of electromagnetic configurations to predict, e.g. eddy current losses in magnets or wireless energy transfer systems. By adaptation of the conductivity function in conducting regions, eddy current distributions in structures containing holes or slit patterns can be obtained.

With the presented technique, eddy currents in conducting structures of finite dimensions can be modeled. The semi-analytical model is for a relatively low number of harmonics computationally faster than 3D finite element methods. The method has been validated and shown to be computationally accurate.