Eddy Current Phenomena Research Articles

An effective higher order finite element computation method for analyzing the eddy current losses in induction motors using subparametric transformations

An enhanced sub-parametric finite element method is presented for analyzing the eddy current losses in induction motors using higher order sub-parametric transformations. The purpose of this study is to construct a very efficient, simple, and exact higher order sub-parametric approach employing a 2D automated mesh generator implemented in JuliaFEM. Alternating current motors are employed in a wide range of industrial and household applications on a frequent basis such as in fans, water heaters, ovens, pumps and many more. High efficiency of the motors is one of the most desirable parameters of these motors. Eddy current losses are predominant in these motors which are responsible for a decline in the efficiency. Consequently, the use of eddy current analysis is vital in evaluating the behaviour of electric devices under various loads. This paper proposes a novel finite element method approach to minimize the 2D eddy current phenomenon by taking the diffusion equation into account. Eddy currents are the primary source of torque in various types of equipment, such as induction motors. In other cases, it is important to analyse the eddy currents to estimate the losses, reactance, and resistance.

Fluid-Solid Interaction Analysis of a Flow Passing Cylinder Based on Variational Mode Decomposition

The fluid-structure interaction problem of cylindrical flow around the cylinder is a classic problem, especially in many fields such as energy engineering, fluid dynamics, engineering structure, energy utilization and development, and environmental protection. In this article, we have heard about the simplified model and analyzed it with the help of the classical cylindrical flow model. In this paper, the flow field was pre-processed on the Workbench software platform, and the pressure distribution and eddy current phenomenon were observed by post-processing given the velocity of the flow field of 1m/s. There is a large number of thunder (2.799552×106) and the Carmen Vortex appears around the cylinder. The vortex falls off periodically, and the wake structure is relatively irregular. The maximum pressure appears at the bottom of the cylinder and the maximum deformation at the top. Then, the pressure term of the simulation results was transferred to the Ansys solver for finite element structural analysis to observe the stresses and strains of the structure under the action of fluids. Finally, the response signal is based on Variational Mode Decomposition (VMD). Its periodic signal corresponded to the flow field, and its components were analyzed in detail. The application of VMD in this area provides innovative inspiration for related fields.

Model Validation of Synchronous Motors With a New Standstill Measurement Technique

Permanent magnet synchronous machines (PMSM), synchronous reluctance machines (SynRM), and electrically excited synchronous machines (EESM) are widely used in the industry and transportation sectors. Their rotors are often equipped with conducting parts like permanent magnets, thick rotor laminations, damper windings, or a conducting sleeve, or they even have a solid rotor core. Such conducting elements do not allow applying standard AC supply techniques for inductance measurements because of the alternating flux induced by eddy currents. We propose a new technique for inductance measurement at a standstill with a quasi-static voltage supply, which mitigates the eddy current phenomenon. The inductance is measured at several rotor positions over a complete electrical cycle, which allows to proceed with a harmonic spectrum analysis of the inductance variation. With this information, it is possible to estimate motor performance characteristics, such as optimum torque, voltage control, power factor, and torque ripple. The new technique is experimentally validated on a 12 kW axially laminated anisotropic solid-rotor high-speed SynRM. In principle, the method also suits PMSMs, EESMs, and other synchronous machines (not verified in this paper). Experimental validation with a solid-rotor SynRM shows a good correspondence with the simulation. Furthermore, the torque computed using the measured inductance is very similar to the experimental one confirming the effectiveness of the method.

Study on the effect of changing stator structure on wind permanent magnet eddy current heating device

With the development of new energy, the proportion of wind power in the global power production structure is increasing year by year, and it has broad development prospects. This article discusses a new type of wind-powered permanent magnet eddy current heating device, which converts excess wind energy into heat energy and stores it in a heat storage medium, so as to achieve the function of storing heat energy. Thermal energy can be directly supplied to users and can also be used for thermal power generation when the power supply is insufficient, which is of practical significance to alleviating the problems of energy shortage and large amount of wind curtailment. Based on the law of electromagnetic induction and eddy current phenomenon, this paper establishes a model of permanent magnet eddy current heating device, and then simulates and analyzes the permanent magnet eddy current heating device to improve the heating power and material utilization of the device. The focus is on the influence of stator groove type, the number of stator slots and the thickness of the stator on the heating power. Finally, the simulation analysis of the permanent magnet eddy current heating device before and after the optimization is carried out in MATLAB. The simulation results prove the effectiveness of the optimization.

Electromagnetic sub-models for 3D edge-elements in transient non-linear simulation

PurposeResolving 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/approachA 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.FindingsThe 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/valueThis 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.

A wearable eddy current based pulmonary function sensor for continuous non-contact point-of-care monitoring during the COVID-19 pandemic

Pulmonary function testing (PFT) allows for quantitative analysis of lung function. However, as a result of the coronavirus disease 2019 (COVID-19) pandemic, a majority of international medical societies have postponed PFTs in an effort to mitigate disease transmission, complicating the continuity of care in high-risk patients diagnosed with COVID-19 or preexisting lung pathologies. Here, we describe the development of a non-contact wearable pulmonary sensor for pulmonary waveform analysis, pulmonary volume quantification, and crude thoracic imaging using the eddy current (EC) phenomenon. Statistical regression analysis is performed to confirm the predictive validity of the sensor, and all data are continuously and digitally stored with a sampling rate of 6,660 samples/second. Wearable pulmonary function sensors may facilitate rapid point-of-care monitoring for high-risk individuals, especially during the COVID-19 pandemic, and easily interface with patient hospital records or telehealth services.

CFD investigation for a 7-pin wrapped-wire fuel assembly with different wires

The fuel rods of the fast reactor are radially and axially fixed and supported by wrapped-wire. The wrapped-wire not only prevents the fuel rod from vibrating but also stirs the coolant, thereby enhancing heat transfer. This paper uses the SST k–ω turbulence model and commercial CFD software to investigate the effect of the number of the wrapped-wires on flow field. The results show that under normal operating conditions, the increase of the number of wrapped wires will increase the pressure difference, but it is conducive to the mixing of the flow field due to the regular eddy current phenomena caused by uneven pressure distribution, which is one of the reasons that affect the convective heat transfer of fuel assemblies.

High-efficiency microwave absorber based on carbon Fiber@La0.7Sr0.3MnO@NiO composite for X-band applications

Carbon fiber (CF) as a multifunctional material with superb performance in aviation industry has serious drawback such as impedance mismatch which restricted the capability of using it as microwave absorber materials. In this research, a novel hierarchical carbon fiber@La0.7Sr0.3MnO@NiO (CF/LS/N) composite was facilely and successfully synthesized via sol-gel and subsequent hydrothermal reactions. The structural, morphological, magnetic and electromagnetic behavior of the composite were precisely evaluated via XRD, FESEM, XPS, VSM and VNA analysis. According to the systematic evaluation results, the synergistic positive effect of adding NiO nanoparticles is revealed in improving the microwave absorption performance of CF@La0.7Sr0.3MnO composite. Literally, dielectric features of the prepared composite enhanced by introducing NiO nanoparticles. Due to improvement in impedance matching, dipole polarization, multiple reflection/scattering, eddy current, interfacial polarization and magnetic resonance phenomenon the minimal reflection loss of the obtained hybrid composite reach to -26 dB with 2.6 mm thickness at filler content of 20 wt%. CF/LS/N composite is predictable to be suitable candidate for military purposes because of the lightweight, low cost and outstanding absorbing properties.

Time- and Frequency-Domain Steady-State Solutions of Nonlinear Motional Eddy Currents Problems

This paper presents a comparison of different time- and frequency-domain solvers for the steady-state simulation of the eddy current phenomena, due to the motion of a permanent magnet array, occurring in the soft-magnetic stator core of electrical machines that exhibits nonlinear material characteristics. Three different dynamic solvers are implemented in the framework of the isogeometric analysis, namely the traditional time-stepping backward-Euler technique, the space-time Galerkin approach, and the harmonic balance method, which operates in the frequency domain. Two-dimensional electrical machine benchmarks, consisting of both slotless and slotted stator core, are considered to establish the accuracy, convergence, and computational efficiency of the presented solvers.

Investigation of high frequency loss in electrical machine lamination considering skin effect and hysteresis

Reducing induction motor losses is very important because of the fulfilment of increasingly stringent requirements set by international regulations for reducing electricity consumption. Since core losses begin to dominate in motors operating at higher frequencies the exact calculation becomes more and more important. The common view is that losses due to higher harmonics caused by stator and rotor slotting constitute an important part of losses in the motor core. Proper calculation of the core losses requires inclusion both hysteresis and eddy current phenomena. For the hysteresis simulation, method included in package Opera 3D has been used. Using that model it was possible to investigate flux behavior at high frequency like as for higher harmonics field. Next part is focused on practical determining of proper method for higher harmonics losses limitation.

Analysis of Disaster Gas Accumulation Characteristics in Local Area of Upper Corner Based on Entropy Variable Dissipative Structure Model

This paper takes the angle CO of the 1406 working face of Fengjiata Coal Mine as main research object, by combining field measurement, theoretical research and numerical simulation, to explore essence of energy dissipation during gas accumulation in the upper lag zone and seek effective governance solutions. The result shows that the irreversible process such as eddy current loss caused by the spatial morphology of the upper sag angle is an important cause of gas accumulation. Thus, a flexible inflatable airbag for mining to change local ventilation mode is proposed and designed. The numerical simulation method is used to verify the venting of the mine inflatable airbag, which helps significantly eliminate the eddy current phenomenon in the lag zone.

Analysis of improving ways for dual nozzle negative pressure chip removal device in deep hole processing

In order to solve the problem of chip removal of the large-length-diameter ratios deep-hole machining, the negative pressure jet model is established on the basis of analysing the mechanism of DF system’s negative pressure chip removal. To solve the energy loss caused by the eddy current phenomenon in the front separation zone, this paper adopts two-stage injection method. The pre-nozzle is added in the front separation zone so that part of the jet fluid enters the front separation zone through this nozzle, reducing unnecessary energy in the front separation zone and increasing the negative pressure value. Through theoretical analysis and fluent simulation optimization experiments, the paper proved that jet angle of the new jet nozzle is 33 degree and the clearance is 0.4mm has the best effect. The negative pressure zone is the largest, and the pressure value in the negative pressure zone is reduced by about 50.7%, which minimizes the energy loss in the front separation zone and enhances the negative pressure chip removal capability

Influence of Contact Plate Parameters and Eddy Currents on Residual Flux Decay in AMF-Type Vacuum Interrupters

The axial magnetic field (AMF)-type contact is utilized in vacuum interrupters (VIs) due to its effectiveness in current interruption. This paper deals with the study of the eddy current phenomenon occurring in the AMF VIs. The residual AMF beyond current zero is directly the result of eddy currents in the contact plate and, thus, is dependent on the contact plate geometry. Considering that the contact plate is analogous to a disk winding, an analytical formulation is developed to compute the eddy current decay constant as a function of contact plate parameters. The analytical predictions are verified using finite-element method (FEM) simulations of the step response of a circular plate placed in a uniform magnetic field. A linear relationship is established between the contact plate parameters and the eddy current decay constant. The analytical formulation is then used to predict the residual flux decay constant in the context of AMF contact model simulations. A coil-type AMF contact is analyzed using FEM simulations, and parametric studies are carried out to study the effect of the contact opening velocity and radial slots on distribution of the contact gap AMF. The results reported in this work will enable VI engineers to improve the contact design by better control of contact plate parameters.

Analysis and numerical modelling of eddy current damper for vibration problems

This work discusses a contactless eddy current damper, which is used to attenuate structural vibration. Eddy currents can remove energy from dynamic systems without any contact and, thus, without adding mass or modifying the rigidity of the structure. An experimental modal analysis of a cantilever beam in the absence of and under a partial magnetic field is conducted in the bandwidth of 01 kHz. The results show that the eddy current phenomenon can attenuate the vibration of the entire structure without modifying the natural frequencies or the mode shapes of the structure itself. In this study, a new inverse method to numerically determine the dynamic properties of the contactless eddy current damper is proposed. The proposed inverse method and the eddy current model based on a lineal viscous force are validated by a practical application. The numerically obtained transfer function correlates with the experimental one, thus showing good agreement in the entire bandwidth of 01 kHz. The proposed method provides an easy and quick tool to model and predict the dynamic behaviour of the contactless eddy current damper, thereby avoiding the use of complex analytical models.

Magnetic Multiscale Model for Local Eddy Current Flow in Complex Materials With Insulated Conductive Particles

This paper proposes an equivalent magnetic hysteresis (B-H) curve for magnetic multiscale problems of complex materials composed of electrical conductors separated by insulating material. The conventional method, which assigns equivalent material constants to each material, cannot properly express the local eddy current loss and the extra magnetic field derived from the local eddy current. To solve this problem, we derive the magnetic hysteresis curve from the volume-averaged magnetic flux density and the surface magnetic field in the micro-model, and apply this curve to the macro-model. The mesh number of the novel macro-model is reduced to around one-tenth that of the micro-model. Magnetic hysteresis is treated by a free energy magnetic hysteresis model, and the macro-model ignores electrical conductivity. The magnetic hysteresis curve and the numerically calculated losses are consistent in the micro- and macro-models. The proposed method well expresses the local eddy current phenomena.

Analytical Modeling of Axial-Flux Permanent Magnet Eddy Current Couplings With a Slotted Conductor Topology

In this paper, a 2-D analytical model for the prediction of the magnetic field in permanent magnet (PM) eddy current couplings with a slotted conductor topology is proposed. The originality of this paper lies in the fact that the influences of both the slots and the iron-core protrusions on the eddy currents induced in the slotted conductor are considered in the analytical computation, and the interactions between adjacent conducting spokes are considered. The magnetic field distribution is obtained by taking account of the eddy current reaction caused by the induced eddy currents in the slotted conductor. The moving PM field is treated as the source of a time-varying magnetic field, and both the effects of the time harmonics and spatial harmonics on the torque computation are analyzed. The results from this analytical model and nonlinear finite-element models are compared, and the effectiveness of the analytical method is demonstrated. The reason for the discrepancies between the results is discussed, and an eddy current clustering phenomenon is observed. The 2-D analytical method has the advantage of taking less computational time for a parametric study than the 3-D finite-element method, and can be a useful tool for design optimization.

Influence of simplifications of the rotational magnetization model on calculation accuracy

Purpose – The purpose of this paper is to present the differences in results of numerical calculations arising from different simplifications of the rotational magnetization model in typical dynamo sheets. Design/methodology/approach – A comprehensive model of rotational magnetization processes in typical dynamo sheets should take into consideration the magnetic hysteresis and eddy current phenomena and also certain anisotropic properties. The chosen model of the rotational magnetization is briefly presented in this paper. A method of the inclusion of the rotational magnetization model into equations of the magnetic field distribution is described. The correctness of these equations has been verified experimentally. Numerical calculations of the rotational magnetization in two types of dynamo sheets were carried out for several simplifications of the described model. Findings – Results of numerical calculations of the rotational magnetization with the omission of the hysteresis phenomenon or with the omis...

Synthesis and electromagnetic properties of Fe3S4 nanoparticles

Fe3S4 nanoparticles with a narrow diameter distribution of 50nm have been synthesized by an environmentally benign chemical method and the electromagnetic properties were investigated in the frequency range of 0.03–18GHz. Theoretical approach, based on the Cole–Cole semicircle, evidently indicates that the dielectric relaxation process corresponds to the Debye dipolar relaxation, meanwhile accompanying with a suppressed eddy current phenomenon. Additionally, Fe3S4 nanoparticles possess significant magnetic losses mainly arising from the natural resonance, resulting in an ideal electromagnetic match. The reflection loss is optimized to be −36.03dB at 12.61GHz for a Fe3S4-paraffine composite layer of 3.0mm in thickness. The electromagnetic absorption properties are ascribed to a synergetic effect of dielectric loss, magnetic loss and the quarter-wavelength cancellation.

Comparison of multiscale models for eddy current computation in granular magnetic materials

In this paper, two multiscale numerical techniques are applied to the study of eddy current phenomena in magnetic granular materials. In particular, the Multiscale Finite Element Method and the Variational Multiscale Method are compared in terms of accuracy and computational efficiency with respect to a standard Finite Element approach and to a homogenization technique with second-order correctors. The numerical analysis is carried on focusing on specific conditions arising in the simulation of actual granular materials, such as soft ferrites and composite materials. In particular, depending on the working frequency and domain size, the electromagnetic phenomena may have a mainly local or global behavior, resulting in a different numerical response of the considered techniques. The results show that the Variational Multiscale Method is more accurate than the Multiscale Finite Element Method, but less efficient from a computational point of view. Moreover, the Multiscale Finite Element Method is found to have a complementary behavior with respect to the homogenization approach with local correctors.

Finite-Element Model for Simulation of Ferrite-Core Eddy-Current Probe

The finite-element method is widely used in modeling eddy-current phenomena. However, its application in eddy-current nondestructive testing involving probe motion requires remeshing for each coil position. Remeshing is not only cumbersome but also a major source of computational noise. We have used the reduced magnetic vector potential formulation to model an air-core probe scan without remeshing the coil in different positions. In this paper, we present a method to model the scanning of ferrite-core probe. With this method, finite-element meshes for the test sample and the ferrite core are generated separately. The coil is not meshed. The magnetic field and magnetic vector potential due to the coil are evaluated analytically. An iterative but fast procedure is used to update the total field. The method is simple, flexible, accurate, and efficient.