Eddy Current Density Research Articles

The effect of test track wheel radius on the evaluation of linear eddy current braking performance of high-speed maglev train

To study the braking performance of linear eddy current brake (LECB) for high-speed maglev trains, experimental studies are usually carried out using a track wheel with a finite radius and a track wheel eddy current brake (TWECB) with a certain radius of curvature. However, the geometrical differences between the two braking methods due to the track radius will lead to differences in their effective excitation air gap during operation. Therefore, the excitation air gap model and eddy current braking force model of TWECB and LECB are developed in this study. Through the excitation air gap model and eddy current braking force model proposed in this paper, the difference in braking performance between TWECB and LECB in the velocity domain and operating air gap domain can be obtained for different track radii. The correctness of the finite element analysis (FEA) method is verified by experimental data, and the eddy current density, braking force and air gap flux density formed by eddy current braking at different track radii are analysed using the finite element method. The results show that an appropriate test track radius can significantly improve the accuracy of TWECB in estimating the braking performance of LECB.

Experimental study of different innovative measurement methodologies applied to a canned pulsed eddy current testing probe suitable for dilation measurement of test specimens

A compact pulsed eddy current testing probe is being developed for the online dilation measurement of test specimens, examined in the high-temperature environment of material testing reactors. The probe has to be canned with metallic clad to protect it from the corrosive sodium-potassium coolant medium present in the material testing reactor. Electromagnetic modelling of the probe was carried out to compute the distribution of time-dependent eddy current density in the vicinity of the probe. It is understood that the slope of the pulsed eddy current signals in the specific time zone where the lift-off point of intersection occurs show a good correlation to the distance between the face of the probe and the test specimen. This paper discusses the experimental study of employing different measurement methodologies at room temperature with the canned pulsed eddy current probe to evaluate its feasibility for dilation measurement. It is observed that a phenomenon of a divergence of signals, akin to the lift-off point of intersection, occurs just after the transient part of the pulsed eddy current signals. Slope analysis of these diverging pulsed eddy current signals was carried out for characterisation of the probe in the air medium as well as the metallic medium present in the gap between the probe face and the test specimen.

Theoretical essentials for designing viscous liquid pumping systems in the conditions of the Arctic region

The purpose is the creation of a scientifically based solution for the design of hermetic electromechanical converters adapted to existing pipelines, as well as those under construction and development. These pipelines meet the energy efficiency requirements and operate in the conditions of the Arctic region. Methods: methods of mathematical analysis, numerical methods, and methods of mathematical programming were used as the main mathematical means. The CFD design package of Ansys Maxwell was used. Research results: we showed that an increase of the efficiency of the system of technological transportation of petroleum products at low temperatures is possible through the use of electromechanical devices that combine the functions of heating and pumping the working liquid. We solved the field problem based on the analytical calculations carried out by a computer. This allowed us to determine the distribution of eddy current density in the structural elements of these devices responsible for creating pressure and heating the pumped petroleum products. The importance of the electrical parameters of the secondary windings has been confirmed numerically and experimentally. The hydraulic characteristics, mechanical losses, volumetric losses and efficiency are determined. Taking into account the outcomes of theoretical studies the experimental sample of the sealed electromechanical converter with the specified physical and chemical characteristics was created at Emperor Alexander I St. Petersburg State Transport University. Practical relevance: the obtained analytical formulas can be used at the development of the systems for pumping viscous liquids at low temperatures using the sealed electromechanical converters which helps to reduce the installed power of energy equipment without degrading the values of technological indicators.

Calculation of magnetic field and eddy current loss in end clamping ring of 300MVA synchronous condenser based on a novel semi‐analytical method

AbstractIt is very important to consider the eddy current reaction of the metal structure in large electric machines, which has a direct impact on the calculation results of induced current and loss. In order to solve the problem that the complex end leakage magnetic field is difficult to calculate directly, a new semi‐analytical method (NSM) considering the eddy current reaction is proposed. Firstly, the corresponding relationship between the external magnetic field and the global magnetic field of the clamping ring in two simple calculation models is obtained by the 3‐D finite element method. Then, the external magnetic field of the clamping ring in a 300MVA synchronous condenser under rated operating conditions is calculated, and the global magnetic field of the clamping ring is determined based on the obtained corresponding relationship. The eddy current density and eddy current loss of the clamping ring are calculated using the external magnetic field and the global magnetic field respectively. Finally, the calculation results were compared with the 3‐D finite element results, which verified the importance of the global magnetic field and the accuracy of the NSM.

Simulation research on transmission characteristics of double drum excitation governor

Aiming at the disadvantage that traditional permanent magnet governor needs an additional air gap adjusting mechanism, a double-barrel excitation speed adjusting device is proposed, which adjusts the air gap by adjusting current instead of the air gap. Due to the uncertainty of current speed regulation, the simulation design is analyzed. A structural model and key components of excitation speed regulation are designed. Structural characteristics and principles of the model are introduced. Due to the complexity of the multi-physical field, the finite element analysis method is used. Based on the three-dimensional moving eddy current field, the simulation model of the double-barrel excitation governor is established; the variation law and speed characteristics of the electromagnetic field in transient excitation governor are analyzed; the magnetic induction intensity cloud diagram, eddy current density vector diagram, and circumferential variation curve of air gap magnetic induction intensity are obtained, and the relationship between speed difference on output torque under different current is got. The results show that the output torque increases with the increase of excitation current. With the increase in slip ratio, it will first increase and then decrease. Its laws and conclusions can provide a novel method for further design and optimization of excitation governor.

The Influence of Material Electromagnetic Parameters on Results of Stress Measurement With Eddy Current Thermography

Abstract If the relationship between electromagnetic parameters and the stress state were characterized by analyzation, it would be helpful to evaluate and classify the flaws in the sample with eddy current thermography (ECT). This paper reported the numerical simulation of the influence of material electromagnetic parameters on the stress state in ECT testing. The influences of conductivity, magnetic permeability, and the thickness of its variation layer on eddy current density and Joule heating have been examined. The results show that the value of electromagnetic parameters and the thickness of its variation layer can be derived from the highest temperature and the distribution of temperature field obtained by using ECT.

Impact of Die Coatings on Forming Conditions in Electromagnetic Embossing of Thin Sheet Metal

In electromagnetic embossing, the interaction of the magnetic field and the induced current density results in body forces that enable the replication of optical microstructures into thin sheet metals. However, as the sheet metal is completely penetrated by the magnetic field, electromagnetic properties of the dies need to be considered in process design, as they influence the forming conditions by changing the field distribution, force vectors and eddy current densities. With die coatings like electroless nickel–phosphorus (NiP), the electromagnetic properties of the die change. Therefore, the effect of both - die substrate and coating material - was studied to find advantageous conditions for electromagnetic embossing. Within two-dimensional electromagnetic field simulation, the electromagnetic properties of coating and substrate material were varied in addition to the coating thickness. To validate the results, electromagnetic embossing experiments were carried out. Here, different dies were fabricated from aluminum (uncoated) and cold work steel with 200 µm and 400 µm thick electroless nickel–phosphorus coatings that were subsequently micro-structured in optical surface quality. It was demonstrated by numerical and experimental results that the coating and the substrate influence the electromagnetic embossing significantly in correspondence to their shielding behavior and field interaction due to electromagnetic properties and coating thickness.

Effects of the wire mesh on pulsed eddy current detection of corrosion under insulation

ABSTRACT Pulsed eddy current (PEC) technique has been used to detect corrosion under insulation (CUI) for decades, but whether and how the wire mesh laid in the insulation layer affects the detection remains ambiguous. This paper touches on this issue for the first time. The insulated structure was simplified to a carbon steel plate covered by a cladding with an air gap representing the insulation layer, in which the wire mesh was situated. Finite element simulations were performed on the simplified model and found that the aluminium or stainless steel wire mesh had little effect on eddy currents in the plate, while the mild steel wire mesh could cause a considerable increase in the probe footprint and a significant drop of the eddy current density. For the mild steel wire mesh, the magnetic permeability and wire diameter were the main factors affecting the probe footprint and eddy current density. Afterwards, simulations were conducted to analyse the effect of the mild steel wire mesh on the PEC probe performances for evaluating the CUI depth and found that the mild steel wire mesh led to decreases in both the PEC signal amplitude and decay rate. The simulation results were finally verified by experiments.

Improved Control of Mesh Density in Adaptive Tetrahedral Meshes for Finite Element Modeling

Tetrahedral meshing is the critical element of finite element modeling. Recently, adaptive meshing has been commonly used. In such meshing, according to the Delaunay method, mesh density is connected with the curvature of modeled object’s edge. Such a method is especially efficient during the modeling of mechanical systems. However, the efficiency of commonly used meshing algorithms is strongly limited in surface-focused phenomena, such as eddy current induced by magneto-dynamic processes. The paper proposes the improved method of Delaunay meshing considering the specific requirements of magnetodynamic systems. In the proposed method, tetrahedral mesh density may be flexibly modified according to the needs of modeled physical phenomena, such as eddy current density. As a result, physical effects may be efficiently and accurately described in finite element models. The paper presents the example of implementing the proposed solution for cylindrical wire. The complete source code is available as open-source software for further practical use and development.

СТРУМИ ТА ЕЛЕКТРОМАГНІТНІ ЗУСИЛЛЯ В СИСТЕМАХ МАГНІТНО-ІМПУЛЬСНОЇ ОБРОБКИ З ФЕРОМАГНІТНОЮ ПЛАТФОРМОЮ

The action of high-density pulsed currents (109 A/m2) leads to the appearance of the electro-plastic effect in metal products. It is proposed to use magnetic pulse treatment of nonmagnetic plates by electromagnetic inductors with a U-shaped magnetic circuit for local flow pulsed currents in the nonmagnetic plates. The work aims to establish an influence of a ferromagnetic platform with nonlinear magnetic permeability on pulsed eddy currents and magnetic pressure of nonmagnetic metal plates with different electrical conductivity in modeling magnetic pulse treatment of welded joints to achieve the electro-plastic effect. Numerical simulation of pulsed electromagnetic fields by the finite element method is used. The current calculation in the inductor's winding is performed by solving the equations of the magnetic field and the electric circuit equations for a discrete-time interval. A power source is a capacitor that is charged to a specific voltage. To study the effect of the ferromagnetic platform on eddy currents and forces in a nonmagnetic plate with its different electrical conductivity, the same pulsed current in the inductor's winding is used. The dependence of amplitude values of eddy current density and magnetic pressure on the surfaces of nonmagnetic plates of different electrical conductivity is investigated. The influence of the presence and absence of a ferromagnetic platform and its electrical conductivity and magnetic permeability on the values ​​of eddy currents and magnetic pressure in the nonmagnetic plate have been studied. Ref. 13, fig. 7, table.

ESTIMATION OF EDDY CURRENTS AND POWER LOSSES IN THE ROTOR OF A SCREW ELECTROTHERMOMECHANICAL CONVERTER FOR ADDITIVE MANUFACTURING

3D printing technologies for large-scale structures allow architects and builders to considerably expand the design boundaries of structures and increase the efficiency of their construction. Mobile robotic platforms for 3D printing are increasingly being implemented in the construction sector, as well as in the production of road surfaces, allowing to solve the problem of limited working space. The typical design of the extruder assembly of a robotic platform for 3D printing large-scale structures can be improved by combining an electric motor, an auger extruder, and a heater in one housing. The proposed auger-type electrothermomechanical converter uses an external auger rotor, which simultaneously performs the functions of an asynchronous motor rotor, a heating element, an actuator, and a protective housing. The purpose of this study was to evaluate the efficiency of using an auger converter as part of a mobile robotic platform for additive manufacturing. For converters operating in difficult conditions, the use of field calculation methods is relevant. In this study, a field calculation was performed using the finite element method and the spatial distribution of eddy currents in the section of the hollow ferromagnetic rotor was found. Pictures of the three-dimensional distribution of the z-component, the normal component of the density of eddy currents, as well as the distribution of the dissipated power density, which considers all types of losses in the rotor, were obtained using the Comsol Multiphysics software and computing complex. The practical value of the obtained results lies in the possibility of predicting optimal indicators of the influence of the thermal regime on the material, as well as the speed of rotation of the converter rotor. This will determine the mechanical properties of the material at the output of the device.

Applicability of eddy current testing in CFRP using electrodes on CFRP surface and control of the testing range

In this study, a novel eddy current testing (ECT) method was developed to facilitate the testing of unidirectional carbon fiber reinforced plastic (UD-CFRP) and control the detection range. First, the effect of adding electrodes orthogonal to the fibers of UD-CFRP were analyzed. The results showed that the eddy current density could be significantly increased by adding electrodes. Moreover, it was found that the distribution of eddy current density in depth axis can be controlled by adjusting the distance of electrodes. Next, the same analysis was conducted for quasi-isotropic CFRP for comparison. The results showed that, unlike the results for the UD-CFRP, the distribution in depth direction could not be controlled by adjusting the distance of the electrodes. Finally, the impedance of the UD-CFRP with electrodes was measured, for confirming that adding electrodes facilitated ECT. It was also confirmed that the impedance increased as the distance between electrodes increased, and this trend was consistent with the numerical simulation results.

Multi-physics coupling simulation of electrode induction melting gas atomization for advanced titanium alloys powder preparation

A numerical modeling method is proposed for the melting process of Titanium metals of Titanium alloys powder preparation used for 3D printing. The melting process simulation, which involves the tight coupling between electromagnetic field, thermal field and fluid flow as well as deformation associated during the melting process, is conducted by adopting the finite element method. A two-way coupling strategy is used to include the interactions between these fields by incorporating the material properties dependent on temperature and the coupling terms. In addition, heat radiation and phase change are also considered in this paper. The arbitrary Lagrangian–Eulerian formulation is exploited to model the deformation of Titanium metal during the melting process. The distribution of electromagnetic flux density, eddy current density, temperature, and fluid flow velocity at different time can be determined by utilizing this numerical method. In a word, the method proposed in this paper provides a general way to predict the melting process of electrode induction melting gas atomization (EIGA) dynamically, and it also could be used as a reference for the design and optimization of EIGA.

Research on Electric Conductivity of Thermo-plastic Composites Based on Eddy Current Loss

Thermoplastic composites has attracted extensive attention in industrial process with excellent properties. As one of the most important parameters, electric conductivity is difficult to detect due to its inhomogeneity and anisotropy. In this paper, a novel method for measuring volume electric conductivity of composites based on eddy current loss has been introduced by using both experimental and numerical approaches. Initially, the eddy current loss and equivalent volume conductivity under different magnetic flux density are presented by analyzing voltage and current acquired in a designed air-gapless reactor under 500 Hz sinusoidal excitation with variety amplitudes. Then, to verify the measurement method and determine the influence of different materials on the eddy current loss, a 3-D electromagnetic model of the experimental devices is built and three cases with different materials are calculated. The parameters including eddy current loss and magnetic flux density are presented. The mechanism underlying the influence of different conductivity on the measuring model is analyzed according to the confidents and eddy current loss. Results show that the ratio of eddy current loss to the square of magnetic flux density is linear. The formula of equivalent volume conductivity needs to be revised by multiplying certain coefficients for high conductivity due to the eddy current effect on the detection coil. It is reasonable that magnetic flux density rang is set in 0.2~0.8T during measurement.

Design optimization of APMEC using chaos multi-objective particle swarm optimization algorithm

In order to meet the requirement that the permanent magnet eddy current coupler has larger output torque and smaller eddy current loss in actual operation, the structural parameters and operation performance of axial permanent magnet eddy current coupler (APMEC) are optimized by chaos multi-objective particle swarm optimization algorithm (CMOPSO) in this paper. The model of APMEC is established by three-dimensional finite element simulation. The central composite design (CCD) method is used to select the appropriate test point, and the response value is obtained by ANSYS finite element analysis software simulation. The second-order response surface regression model of APMEC was established according to the response value. The CMOPSO is used to optimize APMEC, and the optimal combination of structural parameters is obtained. By comparing the eddy current density distribution of APMEC before and after optimization with the finite element simulation experiment, it is verified that the optimization method is feasible to optimize the structural parameters of APMEC. The optimization results show that the efficiency of the permanent magnet eddy current coupler is more than 94%, and the energy consumption is reduced to 83% of the original energy consumption.

Modeling Magnetic Material Using Vector Potential-Based Elements in ANSYS and Comparing with Edge-Based Elements

More and more, soft or hard magnetic materials have been used in the magnetic confinement fusion machine, like reduced-activation ferritic-martensitic steel, which may be used in the first wall and breeding blanket structural material of ITER. Twisted coils in the stellarator may be substituted by permanent magnets. ANSYS electromagnetic simulation has two methods: nodal-based formulation or edge-based formulation. Nodal-based formulation has been widely used in past years. This paper will present a modification to the nodal-based element SOLID97 in ANSYS to form the correct normal boundary condition to model ferromagnetic materials and compare the results, e.g., field, eddy current density, and Lorentz force, to edge-based methods using SOLID236.

ВПЛИВ П-ПОДІБНОГО МАГНІТОПРОВОДУ ІМПУЛЬСНОГО ІНДУКТОРА З ДВОМА КОТУШКАМИ НА ВИХРОВІ СТРУМИ ТОНКОСТІННИХ НЕМАГНІТНИХ МЕТАЛІВ У ПРОЦЕСІ МАГНІТОІМПУЛЬСНОЇ ОБРОБКИ

A review of the literature on the use of pulsed electric current to create electro-plastic effect in metal parts is performed. Inductor with a U-shaped magnetic core and pulsed current is investigated for processing thin-walled metal plates with rectilinear welds. With a saturated magnetic core relative magnetic permeability can be low, so using a magnetic core can be impractical. The aim of the work is to establish the influence of a magnetic core of an induction system on voltage, current and magnetic forces when reaching the eddy current density of 109 A/m2 in the weld of a non-magnetic thin-walled metal plate. A two-dimensional model of the induction system with and without the magnetic core is investigated here. Simulation of the distribution of electromagnetic fields with the reduction of the parameters of the two-dimensional model to three-dimensional is performed. A capacitor charged to a certain voltage is a source of pulsed currents in inductor winding. The equation of the electric circuit for determining the current in the inductor’s winding is solved. The influence of the dimensions of the magnetic core on voltage and currents in the inductor’s winding is determined. The influence of the magnetic core on the transients of voltages of capacitor and inductor, the currents in the winding and the weld of the metal non-magnetic plate, the magnetic forces in the weld is studied. The influence of the magnetic core on distribution of magnetic field strength, currents and magnetic forces on the surface of the plate in the area of the weld is studied. Ref. 13, Fig. 4, Table.

Mitigation of the error field and eddy currents for the start-up of spherical tokamak using compensation and reverse coils

The tokamak is the most popularly accepted device among the fusion community for future fusion reactors. It has an assembly of toroidal field (TF), central solenoid (CS), poloidal field (PF) coils, and compensation coils (CC) for sustaining plasma in the vacuum vessel (VV). Eddy currents are crucial for the steady-state operation of a tokamak. Major sources of eddy current in the tokamak are edge localized modes and transient currents in the CS and TF coils. Eddy currents strongly affect the tokamak startup scenarios. Eddy currents are produced due to flux changes, the vertical component of the magnetic field (VCMF) of the CS coil, and also by the fast rise of current in the TF coil in the initial phase. This study is aimed to estimate the eddy current density and magnitude of the VCMF by experimental and simulation tools. Eddy current density and VCMF are mitigated on the central cylinder and vacuum vessel, using a pair of six turn CC connected in series with CS and a reverse coil connected in series with TF coil. The current direction in the reverse coil is opposite to the direction of current in the Z-shaped connectors of the TF coil. Tokamak startup is optimized by decreasing the eddy current density, VCMF, and the resulting electromagnetic (EM) forces with the installation of CC and reverse coils.

Design and Force Analysis of Salient Single-Sided Linear Induction Motor

The linear induction motors, due to their unique features, utilize in various applications. The most crucial drawback of the linear induction motors is the large air gap between secondary and primary. This problem deteriorates the performance of linear induction motor, increases power loss, and causes to low efficiency. In this paper, a novel structure of single-sided linear induction motor is proposed to reduce the magnetic air gap. This structure consists of ladder-slit sheets and salient back iron for secondary of single-sided linear induction motor. The salient parts of back iron fill the slits of sheet, and therefore, the effective magnetic air gap can be decreased owing to partial form. Also, the electromagnetic aspects of the proposed secondary such as z-component of air gap flux density, y-component of aluminum eddy current density, and three components of Lorentz force are analyzed. Also, the finite element method and the analytical method is used for the 3 D analysis of the edge effects as well as the end effects. To show the advantages of the proposed structure, the results are compared with other secondary structures. The results show that the thrust and efficiency of the salient single-sided linear induction motor increased in comparison with other ones.

A Model for Stator Eddy Current Losses Due to Axial Flux in Synchronous Generators at Steady State and under Load Angle Oscillations

The load angle of a synchronous generator connected to a power grid has an eigenfrequency that depends on the operating conditions. The existence of an eigenfrequency can make the generator sensitive to electrical and mechanical disturbances and motivates the use of damper windings and power stabilizing systems. Another reason for keeping load angle oscillations small is that they increase the eddy current losses in the stator core and clamping structure due to axial leakage flux. This is shown with transient finite element analyses and can be explained by a loss model derived from a phasor model of the eddy current loss density.