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This paper describes iterative methods for the high frequency electromagnetic analysis using the finite element method of Maxwell equations including displacement current. The conjugate orthogonal conjugate gradient method has been widely used to solve a complex symmetric system. However, the conventional method suffers from oscillating convergence histories in large-scale analysis. In this paper, to solve large-scale complex symmetric systems arising from the formulation of the E method, an iterative substructuring method like the minimal residual method is presented, and the performance of the convergence of the method is evaluated by numerical results. As the result, the proposed method shows a stable convergence behavior and a fast convergence rate compared to other iterative methods. [ABSTRACT FROM AUTHOR]

The nonconformal domain decomposition methods (DDMs) of the hybrid finite element-boundary integral-multilevel fast multipole algorithm (FE-BI-MLFMA) are presented for computing large electromagnetic scattering/radiation problems. The numerical performance of different transmission conditions between finite element method (FEM) subdomains, and FEM and BI domains is studied in this paper. The Dirichlet transmission condition (DTC) employed at the interface between FEM and BI domains has faster convergence than the Robin-type transmission condition, and this finding is different from the conclusions for the FEM DDMs published in the literature. Furthermore, the cement-element (CE)-based dual-primal finite element tearing and interconnecting (FETI-DP) DDM has faster convergence than the Lagrange-multiplier-based FETI-DP method under the FE-BI system, and is also different from that under the system of the FEM with the absorbing boundary condition (FEM-ABC). It shows that the DDMs of FE-BI-MLFMA have some essential differences from those of FEM-ABC. The analysis of these numerical phenomena is presented in this paper. Further comparison between the DDMs of FE-BI-MLFMA and FEM-ABC demonstrates that the DDMs of FE-BI-MLMFA have essential advantages over those of FEM-ABC. Various numerical experiments confirm the accuracy, efficiency, and flexibility of the nonconformal DDM of FE-BI-MLFMA, which is the CE-based FETI-DP DDM with DTC connecting FEM and BI. [ABSTRACT FROM AUTHOR]

In this paper, the characteristics of the electromagnetic noise radiated by an external rotor in-wheel motor (IWM) are investigated with the Doppler effect taken into consideration. First, Maxwell stress tensor method is employed to derive electromagnetic forces on the magnet surface. The effect of common current harmonics is also analyzed. Then, a structural model of the rotor is built and modal test is conducted to validate the model. Nodal forces, which are calculated by finite element method, are transferred from the electromagnetic mesh to the structural model for further vibration prediction. Finally, boundary element method is used to calculate the noise radiated by the rotor. In particular, the Doppler effect is considered. The calculated results are validated by the noise test. It is found that the end cap contributes more to the overall noise than the shell, and obvious sound directivity appears in the noise of the IWM. The noise measured perpendicular to the outer end cap is larger than that measured in other directions. In addition, the Doppler effect would induce additional side-frequency components around high-frequency peaks in the external rotor motor. [ABSTRACT FROM PUBLISHER]

This paper describes a two-dimensional (2-D) analytical model to predict the magnetic field distribution in axial-field magnetic gears by using the sub-domain method. The sub-domain method consists in solving the partial differential equations linked to the Maxwell's equations in each rectangular region (magnets, air gaps, and slots) by the separation of variables method. The proposed model is based on a two-dimensional approximation for the magnetic field distribution (mean radius model) i.e. the problem is solved in 2-D Cartesian coordinates. One of the main contributions of the paper concerns the analytic solution of the magnetic field in a slot open on the two sides (space between the ferromagnetic pole-pieces). Moreover, it is shown that the analytical model and the 3-D finite elements simulations follow the same trends in the determination of the optimum values for the geometrical parameters. As the analytical model takes less computational time than 3-D numerical model, it can be used as an effective tool for the first step of design optimization. [ABSTRACT FROM PUBLISHER]

This paper deals with some aspects of formulation and implementation of a broadband algorithm with build-in analysis of some dispersive media. The construction of the finite element method (FEM) based on direct integration of Maxwell's equations and solution of some additional convolution integrals is presented. The broadband, fractional model of permittivity is approximated by a set of some relaxation sub-models. The properties of the 3D time-dependent formulation of the FEM algorithm are determined using a benchmark problem with the Cole-Cole and the Davidson-Cole models. Several issues associated with the implementation and some constraints of the broadband finite element algorithm are presented. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to provide an efficient computational model for fast and accurate calculation of electromagnetically induced vibrations in electrical machines. Although a three-phase permanent-magnet synchronous machine has been used in this paper, the same methodology can be extended to other types of electric machinery. A brief comparison between the different methods for structural analysis in electrical machines is introduced. The method proposed in this paper uses finite-element analysis in order to extract the impulse responses that are used in calculating the vibration. A field reconstruction method is used for the electromagnetic field analysis. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to highlight the capabilities of a new hybrid analytical modeling (HAM) approach for the analysis and design of various electromagnetic structures. After an introduction, where the aim of the development of this modeling approach is presented, the modeling approach is described. The new HAM is based on a strong coupling of the magnetic equivalent circuits method and analytical models (AMs). The AM, based on the formal solution of Maxwell’s equations, is established thanks to the separation of variables method. The HAM is applied to different permanent magnet electric machine structures, and the results are validated extensively by comparison with the finite-element analyses. [ABSTRACT FROM AUTHOR]

An automatic mesh generation method employing a dynamic bubble system can provide a high-quality mesh for electromagnetic finite element analysis. However, it takes a very long time to compute bubbles' movement when a mesh with a large number of elements is generated. The bubbles move according to a force among them, such as the van der Waals force. However, the force received from bubbles of very far distance can be ignored. Therefore, it is unnecessary to calculate the force from all the bubbles. In this paper, we propose a subdivided dynamic bubble system in order to shorten the computation time. The proposed method considers the analysis region to be divided into some tetrahedral subdivisions, and then the bubbles move independently in the tetrahedral subdivisions. As a result, acceleration of the computation time is achieved. [ABSTRACT FROM AUTHOR]

Fast design procedures of electrical machines require the use of adapted modeling approaches. This is particularly true for axial flux permanent magnet (AFPM) machines, which have an intrinsic 3-D electromagnetic structure. Indeed, accurate modeling of AFPM machines requires the use of 3-D finite-element analysis (3-D FEA), which is highly time consuming, especially at first design stages. This paper presents a new quasi-3-D analytical model (AM) that allows modeling accurately AFPM machines while saving a huge amount of time as compared with 3-D FEA. This new approach combines a multislice AM, which takes into account a part of the 3-D effects, and considers the end-effects by a simple and effective radial dependence modeling of the magnetic field in AFPM machines. [ABSTRACT FROM AUTHOR]

Abstract: The enhancements carried out in the tokamak ASDEX Upgrade (AUG) are oriented toward the preparation of the future physics-related activities of ITER and DEMO. To address the main ITER issues, plasma configurations with a wider operational limit (e.g. higher triangularity) are planned for the future experimental campaigns in AUG. To evaluate the mechanical impact on the toroidal field (TF) magnet system a combined electromagnetic and structural finite element model was set up. At first extensive benchmarks of the models are carried out against the AUG reference design configurations with respect to stress [1–3], lateral displacement measurements and poloidal flux pattern. The numerical model was then applied to a set of actual high triangularity (HT) configurations generated by a more favorable poloidal field (PF) current distribution made possible by an extension of the power supply system. The resulting change of the poloidal flux pattern and the lateral force distribution has consequences for the coil shear stress and vault stability. Both aspects are monitored by a safety system measuring the PF flux placed on top and bottom of the outer surface of two TF coils (TFCs) between vault and the TFC supporting structure, so called Turn Over Structure (TOS). The range of the new HT configurations has induced a modification of the flux pattern, so that an adaptation of safety system is required to protect the TFCs system. Following the same criteria of the old safety system [4,5], a new set up of virtual coils will be integrated in the control system of AUG. The motivation of this new set up will be discussed in this paper. [Copyright &y& Elsevier]

Abstract: Electromagnetic forming (EMF) is a high velocity forming technique that reshapes electrically conductive materials by abruptly discharging a bank of capacitors through a coil. The oscillation frequency of the discharge is a key parameter in the design of an EMF system. For a given initial stored energy, there exist a frequency that produces the maximum workpiece deformation. Once we know it, we can set the electrical parameters of the EMF system to make the current intensity oscillate with this optimum frequency. This saves energy and money, preventing also the premature wearing of the coil. The objective of the present paper is to find the optimum frequency of an EMF system. Using the results provided by a finite element model in frequency domain, we are able to obtain the current flowing trough the coil, the Lorentz force acting on the workpiece, a function relating the electrical parameters of the EMF system with frequency and the optimum frequency of the discharge. Our approach can be very useful for coil design and for modeling complex three-dimensional geometries. To validate the method presented here, we apply it to tube compression and tube expansion processes and compare our results with those provided by other authors. [Copyright &y& Elsevier]

The paper describes the formulation and implementation of the broadband finite element time domain algorithm. The presented formalism is valid to analysis of electromagnetic phenomena in linear, frequency selective materials. The complex profile of permittivity of materials is approximated using a set of the Lorentz resonance models. The solution of the integro-differential second order equation is obtained using a singlestep integration scheme and a recursive convolution algorithm. The discussed formulation enables to adopt the structure of the narrowband part as well as the phase of calculation of the convolution equations for the subsequent components. The properties of the algorithm are validated using a finite difference broadband algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a physics-based high-frequency (HF) model of switching power converters including the insulated gate bipolar transistor (IGBT) unit cells, heat sink, and connective printed circuit board (PCB) traces combined in a single electrical circuit is presented. The IGBT model includes the HF stray components superimposed on the well-known Hefner IGBT model. The HF components were calculated using a 3-D quasi-static finite element (3-D FE) analysis. The proposed complex model of the IGBT was verified both numerically and experimentally at different switching frequencies. The computed IGBT model was used in a low–high frequency model of a motor-drive system, and the common mode ground current was experimentally verified showing excellent results. [ABSTRACT FROM AUTHOR]

In the paper, a novel approach to numerical modeling of tube induction welding is proposed. The coupled electromagnetic and thermal model must take into account also the movement of the metal strip: in order to make possible this kind of simulation in reasonable computation time, a simplified approach to the modeling is presented and discussed. [ABSTRACT FROM PUBLISHER]

This paper deals with the dynamic characteristics of a linear induction motor (LIM) in terms of acceleration times and jerk conditions. We employed Matlab Simulink for conducting simulations of the dynamic modeling of LIM operated by a space vector pulse width modulation inverter. From the simulation results, the maximum load conditions and minimum acceleration times to guarantee passengers' safety were determined. Further, the electromagnetic field theory was employed to derive equivalent circuit parameters, and the results were validated by the finite element method. The analysis model was applied to a magnetic levitation vehicle for providing electromagnetic propulsion force, and its dynamic characteristics were analyzed to predict its operating performance; moreover, experimental results were employed to demonstrate the validity. We believe that the proposed prediction technique for the operating characteristics of LIMs can contribute to improving passengers' safety and riding quality. [ABSTRACT FROM AUTHOR]

This paper deals with the magnet pole shape design of permanent magnet machines for the minimization of torque ripple based on electromagnetic field theory. On the basis of a magnetic vector potential and a two-dimensional (2-D) polar system, analytical solutions for flux density due to permanent magnet (PM) and current are obtained. In particular, the analytical solutions for mathematical expressions of magnets with different circumferential thicknesses can be solved by introducing improved magnetization modeling techniques, resulting in accurate calculations of electromagnetic torque. The analytical results are validated extensively by nonlinear finite element method (FEM). Test results such as back-emf measurements are also given to confirm the analyses. Finally, on the basis of derived analytical solutions, a reduction of torque ripple can be achieved. [ABSTRACT FROM AUTHOR]

Overlapping elements can be used to connect non-conforming meshes in the finite-element method. This approach has been developed with the scalar potential formulation and used to solve magnetostatic problems but not in the case of the vector potential formulation. In this paper, we propose to introduce the overlapping element method in this second formulation. [ABSTRACT FROM PUBLISHER]

The calculation of voltages induced by external electromagnetic fields on multiconductor transmission lines (MTLs) has been the subject of several studies. In this paper, discrete equations for MTLs exposed to incident fields are derived based on the time-domain finite-element method and the backward differentiation formula. Based on these equations, a value-delivery table characterizing the MTLs is presented. Combining this table with modified node analysis formulation, it is convenient for analyzing the responses of transmission lines composed of complex termination networks or complex transmission-lines networks. The validity and efficiency of the proposed algorithm is demonstrated using several examples. Finally, a 1-km 35 kV overhead line above an imperfectly conducting ground is studied, and the influences of ground wire and a metal-oxide arrester to the lightning-induced voltage are both discussed. [ABSTRACT FROM PUBLISHER]

This paper presents copper and iron loss models of a classical switched reluctance motor (SRM) and a mutually coupled switched reluctance motor (MCSRM). The iron losses in different parts of machines are then detailed. Based on the power losses model, a lumped parameter (LP) transient thermal model during driving cycles is performed, the analytical results are validated by the finite-element (FE) transient thermal model. Special attention has been paid to model the salient rotor and a method to transform the salient rotor into a nonsalient one has been proposed. A comparison between the maximum temperatures obtained by using different heat source (average power losses or instantaneous power losses during driving cycles) is given. The experimental tests are also realized to verify the analytical and numerical results. [ABSTRACT FROM PUBLISHER]

This paper concerns the modeling of electromagnetic vibration-and-noise sources in permanent-magnet direct current (PMDC) commutator motors. The electromagnetic sources are considered as an electromagnetic field distributed in the air-gap region of a PMDC motor. The latter is then formulated by the two-dimensional field theory in polar coordinates with the consideration of slotting effects and the armature reaction field. Consequently, based on the derived radial electromagnetic field, the radial and tangential magnetic forces acting on the inner surface of the permanent magnets can be expressed as Fourier functions in forms of space and frequency harmonics. The results obtained from the present models agree well with those from the finite-element models. In addition, the measured cogging torque is compared to those calculated by the analytical and finite-element models to validate the formulated electromagnetic field and magnetic forces. Furthermore, experimental investigations are carried out on the electromagnetic vibration-and-noise behavior of a commonly used PMDC commutator motor (such as that in heating, ventilating, and air conditioning (HVAC) systems). By measuring the natural frequencies and the associated mode shapes of the stator, the relationships between the magnetic forces and the measured vibration-and-noise responses are discussed in the frequency domain. [ABSTRACT FROM PUBLISHER]

Abstract: A finite element model is introduced in this paper to describe the coupling between the welding arc and the weld pool dynamic in pulsed gas tungsten arc welding. The cathode, arc-plasma and melting anode regions are taken into account. The unified time-dependent model describes the heat transfer, fluid flow and electromagnetic fields in the three regions. The originality of the numerical model is its ability to treat the arc and weld pool time evolution under pulsed current welding in a unified formalism, taking into account eddy current in the weld pool. The case of thin plates with fully penetrated weld pools is also handled. To validate the predictions of the model, an Infra-Red camera is used to film the dynamic of the weld pool surface. Then an image processing algorithm permits to get the time evolution of the weld pool width directly from the film. The numerical model is applied to the 304 stainless steel welding, and the computed results show that the predictions are in fair agreement with the experimental results. [Copyright &y& Elsevier]

This paper presents a new neural-network method to describe the electromagnetic (EM) behavior at the interface between the substructures from an internally decomposed EM structure. A set of neural networks is used to represent the EM behavior of the substructure as seen from the interface. This allows EM coupling between substructures to be effectively represented. The method is developed in a finite-element environment. An EM transfer function matrix is formulated to produce training data, allowing neural networks to learn the spatial coupling between EM-field variables at various locations over the interface of the substructure. A new formulation is proposed where trained neural networks are integrated into the finite-element equation for efficient simulation of an overall EM structure. A technique is developed to allow the proposed model to be used with the mesh different from that in neural-network training. Examples show that the proposed method provides better accuracy than conventional neural-network approaches for modeling substructures from an internally decomposed EM problem. Using the proposed model also speeds up finite-element simulation. [ABSTRACT FROM AUTHOR]

In this paper, a new method of electric field design of high voltage vacuum interrupters is proposed. According to the multi-gap insulation effect and the vulnerable breakdown spots theory, the symmetrical voltage shields are proved to be effective. So the initial model of a high voltage vacuum interrupter is designed. Next with finite element methods and optimization theory, a mathematical model of electric field intensity in interrupters is given. What's more, by optimizing this model with finite element software, a more symmetrical electric field in vacuum interrupters is obtained and its peak value appear as in the second auxiliary gaps (the two gaps between the center floating shield and the symmetrical voltage shields). The result shows that with this method, the vacuum interrupters can withstand higher static breakdown. [ABSTRACT FROM AUTHOR]

This paper involves the computation of 3-D magnetic fields in high-performance, long-lifetime solenoid actuators by finite-element (FE) modeling. Operating at frequencies between 150 and 300 Hz, these actuators are unique in terms of the large force they produce (8–15 N) and their very long lifetime (over five billion continuous duty cycles). Their magnetic circuit typically operates at saturation and, because of the compact dimensions, the 3-D nature of the field distribution needs to be taken into account for their design. Results are presented in terms of the effects of design parameters on saturation and force calculation. [ABSTRACT FROM AUTHOR]

In order to reduce the influence of axial displacement and/or to ease the assembly, certain capacitive angular sensors use symmetric designs limiting their absolute measuring range to (360°/n) where it is the number of blades. This paper presents a combined sensor that utilizes a Wiegand sensor to obtain ad. ditional information needed to resolve 360°. Since magnetic and electric fields required by the sensing principles do not interfere, one single rotor design can be used for both fields. When the receiver coil on a Wiegand sensor has to drive a current, this current influences the shape and duration of the pulse generated by the sensor. We found that shape and amplitude of the pulse vary depending on the strength of the applied fields and the location of the initial inverse nucleation. Since most of design optimization for capacitive sensors is done by means of simulations, an adequate model of the combined sensor is needed. For the capacitive part, numerical approches such as the finite element method are available. For the pulse wire part, an extended king model has been developed; results of measurements and numerical simulations are reported. [ABSTRACT FROM AUTHOR]

We have investigated and calculated the distribution of electromagnetic fields and forces induced by a three- phase axially-symmetric system of electric current with six electrodes in a cylinder of a finite length [1, 3]. In this paper the alternating current is fed to each of nine discrete circular conductors-electrodes, which are placed on the internal wall of the cylinder. This new mathematical model describes a real device [7], which transforms electric energy into heat. The viscous incompressible flow of weakly electroconductive liquid-electrolyte is obtained by the finite-difference method, using the monotonous vector finite difference schemes. The average axially-symmetric motion of electrolyte and vortex distribution in a cylinder has been considered. The dependence of electromagnetic forces and velocity distribution at the inlet of the cylinder is investigated in the case of: 1) the vortex formation from the Lorentz force inside the cylinder by the electrode, 2) the vortex-breakdown from the swirl velocity at the inlet of the cylinder. [ABSTRACT FROM AUTHOR]