Leakage Magnetic Field Research Articles

Conceptual Design and Electromagnetic Analysis of 2 MW Fully Superconducting Synchronous Motors With Superconducting Magnetic Shields for Turbo-Electric Propulsion System

With air traffic predicted to increase in the future, CO2 emission must be decreased to prevent global warming. Our research group previously proposed electric propulsion systems based on superconducting technology, which is promising for reducing emissions. In this study, propulsive 2 MW fully superconducting motors were conceptually designed. At operating temperatures of 20 and 64 K, we observed the influence of the superconducting magnetic shield on the electromagnetic properties, especially the output power density, AC loss, and efficiency. The superconducting magnetic shield can reduce leakage magnetic field to the outside of the motor by inducing a current, and the shield is reproduced with a conductor of extremely high conductivity for simplicity in electromagnetic analysis. As a result, at an operating temperature of 20 K, the superconducting motors with the superconducting magnetic shields showed a high power density greater than 40 kW/kg and high efficiency of 99.7%. Even at an operating temperature of 64 K, the motors with the superconducting shield showed a power density and efficiency of 20 kW/kg and 99.4%, respectively.

Generalized Design Approach on Industrial Wireless Chargers

The paper briefly discusses the most important standards and regulations established for high-power wireless power transfer systems and introduces the main issues concerned with the conceptual design process. It analyses the electromagnetic design of the inductive magnetic coupler and proposes key formulas to optimize its electrical parameters for a particular load. The method applies to both the resistive load and the battery charging. It also suggests basic topologies for conceptual design of power electronics and discusses its proper connection to the grid. The proposed design strategy is verified by experimental laboratory measurement including analyses of the leakage magnetic field.

Effect of the Crystallographic Texture Type on the Anisotropy of the Magnetic Leakage Field Parameters of Steel Sheets

This paper examines the distribution of the tangential and normal components of the magnetic leakage fields in pole-magnetized sheet materials, such as cold-worked structural steels St3, 09G2S, and 08G2B, as well as electrical steel with different grain structure and coarse-grained magnetically soft alloy Alfer, which have different types of texture induced by rolling and uniaxial tension. It has been found that even minor changes in the preferential orientation of easy magnetization axes 〈100〉 strongly affect the distribution of the tangential Нτ and normalHn components of magnetic leakage fields. For all studied materials, the magnitude ofНτ significantly exceeds that ofHn. However, in most cases, the componentНn exhibits a larger anisotropy thanНτ. Cold plastic working by rolling and uniaxial tension changes the texture state of the studied structural steels with the formation of multicomponent textures, which causes changes in the angular dependences of the parametersНτ and Hn. This fact indicates that the onset of plastic flow in a ferromagnetic material can be detected by changes in the form of circle diagrams of the leakage field components. The circle diagrams of the parametersНτ and Hn of deformed structural steels have the form of figure-eight patterns that are approximately perpendicular to each other. The position of the maxima of Нτ andHn on these diagrams corresponds to the position of the projections of the easy magnetization axes closest to the rolling plane, i.e., the directions along which iron and its alloys have the lowest strength. Therefore, it may be effective to estimate the anisotropy of strength properties of steel products with different texture states by the anisotropy of their magnetic parameters. More reliable results of magnetic texture analysis can be obtained by constructing full circle diagrams of the magnetic leakage field parameters.

Dimension Reduction Calculation Method of Toroidal Magnet

For the high temperature superconducting magnetic energy storage (HTS SMES) magnet with large capacity, in order to reduce the leakage magnetic field and the vertical magnetic field component on the wire, it mostly adopts the toroidal magnet structure. However, this structure has imposed new challenges in calculating the AC loss of the magnet. Due to the particularity structure of the toroidal magnet, that is, its magnetic field is not distributed in the 2D axisymmetric manner, it is impossible to calculate the AC loss in the toroidal magnet with a traditional 2D computation model. At the same time, the 3D model has its problems, such as the modeling is complicated; the calculation efficiency is low; the demand for computation is enormous, and so on. In order to provide a solution for calculating the AC loss in the magnet with a non-2D axisymmetric distributed magnetic field, a method of “dimensionality reduction and inversion” is proposed. In this method, the magnetic field distribution in the toroidal magnet is calculated by using a 3D model intended for uniform flow, and the AC loss is calculated by using a 2D model. The practical application shows that this method can provide a solution for calculating the AC loss in the magnet with a non-2D axisymmetric distribute magnetic field, and the calculated results meet the requirements of engineering calculation.

Electromagnetic Interference Analysis of Permanent Magnet Linear Synchronous Launchers

The compass of unmanned aerial vehicle (UAV) can be affected by electromagnetic environment in an electromagnetic launch system (EMLS). So, the leakage magnetic field of permanent magnet (PM) linear synchronous launchers will result in electromagnetic interference problem. In this article, the analysis models of leakage magnetic field with different linear machine topology are established. And then the distribution characteristics of environmental leakage magnetic field are evaluated by analytical and finite element method. Finally, the leakage magnetic field of prototypes is tested, and some effective shielding measures are discussed. Based on the analysis results, the preferred topology and winding type with good electromagnetic environment are recommended. The suppression measures can also provide important references for the design of EMLS.

Development of Simulation Modeling Software for Transformer Winding Leakage Magnetic Field Based on C#

Development of Simulation Modeling Software for Transformer Winding Leakage Magnetic Field Based on C#

Design of a Cylindrical Winding Structure for Wireless Power Transfer Used in Rotatory Applications

A cylindrical joint structure for wireless power transfer (WPT) systems is proposed. The transmitter (Tx) and receiver (Rx) coils were wound on hemicylindrical and cylindrical structures, respectively. The Rx coil rotates freely around the axial direction of the Tx coil. Different methods of winding the Tx and Rx coils are given and discussed. Electromagnetic fields (EMFs) around the WPT windings should be lower than the limits set by WPT standards. Therefore, the WPT windings were designed to reduce EMF level and maintain constant power-transfer efficiency (PTE). The design procedures of the windings are discussed in detail. EMF analysis was done under different rotation angles (α). The selected design reduced the variation of the mutual inductance (M). As a result, it maintained a constant PTE while rotating the Rx coil between 0° and 85°. Moreover, leakage magnetic fields (LMFs) near the WPT coils of the chosen design were reduced by 63.6% compared with other winding methods that have the same efficiency. Finally, a prototype was built to validate the proposed idea. Experiment results were in good agreement with the simulation results. The WPT system maintained constant efficiency in spite of the rotation of Rx coil, where efficiency dropped by only 2.15% when the Rx coil rotated between 0° and 85°.

Electro-Magnetic Design of a 3MJ YBCO Magnet

The electro-magnetic design of two 3 MJ superconducting magnetic energy storage (SMES) magnets with YBCO conductor are presented. One magnet is with solenoidal geometry composed of double pancake coils, and the other one is with toroidal geometry. According to the magnetic field simulation results, the perpendicular componet of the magnetic field of the toroidal magnet could be extremely reduced compared with the solenoidal geometry. Therefore, a lower YBCO conductor requirement could be expected due to the dependence of Jc vs B performance of the YBCO conductor. Besides, the lower leakage magnetic field is important for application. A SMES system of 3 MJ is considered, and the coil is made of multiple identical D-type pancake coils. The critical current of the used YBCO conductor at 30K is 270A under 1 T perpendicular magnetic field. The inner radius of the D-type curve is 500 mm, and the outer radius is 1000 mm. The SMES magnet is made of 96 pancake coils, where the rated operating current is 975 A and the maximum perpendicular and parallel magnetic flux density are 0.5 T and 4.0 T, respectively. Further more, the maximum hoop stress and radial stress are 283 MPa and 78 MPa.

Evaluation and selection of shielding methods for wireless charging of e-rickshaw

High leakage magnetic fields are inevitable for wireless charging (WC) of electric vehicles (EVs), due to their large air gap. This high leakage magnetic field may cause adverse effects on human beings in the vicinity. So the design of coil system of WC system to satisfy the safety limits as well as performance is quite important. The electromagnetic fields exposure to human beings should be less than the safety regulations set by International Commission on Non-Ionizing Radiation Protection. Moreover, EVs’ chassis creates unwanted electrical load on the WC affecting the performance and can be improved through shielding of leakage magnetic fields as per the standards. The main focus of this paper is to first investigate the effectiveness of passive, active and resonant current loop shielding methods through finite element method approach considering asymmetrical circular spiral coils. Based on the outcomes, a passive shielding on the receiving side and inductive coil connected in series opposing configuration with transmitting coil have been proposed for the case of e-rickshaw. Accordingly, coil system is fabricated for the air gap of 12 cm and experimental evaluation is carried out.

Leakage magnetic field variation induced by inner surface grooves during loading in geomagnetic environment

The leakage magnetic field which induced by the inner surface groove during loading had been measured from the outer surface in geomagnetic environment. Compared the variation of the leakage magnetic field along the load with the location and development of the groove, it was found that two phenomena are relate to the magnetic field aberration. The relation can be described by the pink-pink value and the gradient of the magnetic field aberration. This result can be used to evaluate and monitor the inner defect by the magnetic field aberration characters.

Influence of Extension Length of Rotor End Windings on the Three-Dimensional Electromagnetic Field and Temperature Rise in the Large Turbine Generator End Zone With Magnetic Screen

Leakage magnetic field from the rotor end windings affects obviously the electromagnetic losses and temperature of end components in the turbine generator end zone with magnetic screen. As the capacity of turbine generator increases, this effect of rotor end windings has become more prominent. To investigate influence of the extension length of rotor end windings on the electromagnetic and thermal fields in the turbine generator end zone with magnetic screen, three-dimensional transient electromagnetic field model of 1250 MW turbine generator end zone is given. Leakage magnetic field and losses of end components are compared and studied in the end zone under the different extension lengths of rotor end windings. Based on the calculation results of electromagnetic losses (heat sources) and flow network (boundary conditions), three-dimensional fluid-thermal coupling field is calculated in the turbine generator end zone with magnetic screen. Distribution of complex fluid velocity in the end zone is obtained. Influence of the different extension lengths of rotor end windings on the stator-end copper coil, screen plate, finger plate, press plate, magnetic screen, and stator end core is researched in the turbine generator end zone. The accuracy of calculation results is validated by experimental values.

Experimental and Numerical Study on Stray Loss in Laminated Magnetic Shielding Under 3-D AC-DC Hybrid Excitations for HVDC Transformers

To investigate the stray loss in magnetic shielding components immersed in the 3-D AC-DC hybrid leakage magnetic field, a modified method is presented with the variation of the eddy current loss inside the coil due to the change of the leakage magnetic field taken into account. In addition, a new loss separation model is proposed to estimate the standard iron loss of the grain-oriented (GO) silicon steel sheet under AC-DC hybrid excitations. Furthermore, the material properties were appropriately treated based on the simplified model of laminated magnetic shielding for efficient numerical calculation. The comparison of field distribution and loss results obtained by experiment and calculation respectively was made, which shows good consistency and thus verifies the effectiveness of the proposed method in this paper. Meanwhile, the stray loss and additional loss in magnetic shielding are analyzed in detail to evaluate the potential threat of AC-DC hybrid excitations on the local overheating of the structural parts in HVDC transformers.

The effect of permanent magnet position on axial and radial load capability in axial hybrid magnetic bearing

The axial and radial load capacity of axial hybrid magnetic bearing (HMB) is critical for the magnetic levitation system. In this paper, the effect of permanent magnet (PM) position on axial and radial magnetic force and stiffness in axial HMB is investigated. Six different configurations are considered and the equivalent magnetic circuits of HMBs for each configuration is built and studied based on the distribution of magnetic field and magnetic leakage. The dependence of axial and radial magnetic force and stiffness on the axial displacement, radial displacement and control current is calculated and investigated for different configurations. To validate the calculated results, the axial and radial magnetic forces for each configuration are simulated by finite element method. A good agreement between the calculated and simulated results validated the proposed magnetic circuit models.

基于微磁学的损伤缺陷检测研究

基于微磁学的损伤缺陷检测研究

Shielding Effectiveness Analysis of the Conducting Spherical Shell With a Circular Aperture Against Low Frequency Magnetic Fields

In this paper, an analytical model is presented to calculate the low frequency magnetic shielding effective (SE) of the spherical shell with a circular aperture and finite conductivity. This model is obtained by the combination of two submodels: the finite conductivity shell without the aperture, and the perfect conductor shell with the aperture. Both the submodels have existing analytical solutions. The first submodel represents the diffusion effect of magnetic field penetration through the conducting shell, and the second one denotes the aperture effect of magnetic field leakage through the aperture. The total magnetic field is the superposition of these from the two submodels. Calculation results are provided for an aluminum spherical shell of radius 0.1m for frequencies between 10Hz and 1MHz. The results are in good agreement with these form 2D axisymmetric finite element simulations. It is shown that there is a critical frequency. Below this frequency, the diffusion effect is dominant and the SE enhances with the increase of frequency. Above this frequency, the aperture effect is dominant and the SE keeps unchanged with the variation of frequency. In addition, the phase shift characteristics are also analyzed for the two effects respectively, and are employed to elucidate the mechanism of the resonance phenomenon of the SE around the critical frequency. Further, the effect of aperture depth is investigated numerically, which shows that increasing the depth has similar effect on SE like reducing aperture radius.

An overlapping peak separation algorithm based on multiorder differential method and genetic algorithm for magnetic eddy current signal of a defect cluster

AbstractSafety assessment plays a vital role in the operation of oil and gas production systems, and data processing is important for the analysis of defects to make correct diagnosis. Therefore, the research to find a reliable data processing method is carried out. The magnetic eddy current signal detected of the defect is generally an abnormal data of “one peak and double valley” type. When the distance between the two defects is close, the leakage magnetic fields of the two defects interfere with each other. In order to facilitate the extraction of the characteristics of such anomalous data, it is necessary to separate the overlapping abnormal data. In this article, the above methods for identifying and processing anomaly detection data of complex defects are studied. The data fitting method is used to find the most suitable fitting function, and the accuracy of overlapping peak separation is optimized by the improved peak separation method based on GA algorithm. The results show that the Gaussian function is most suitable for fitting prediction of the “defective cluster” detection data after separation. The overlapped peak separation result optimized by GA algorithm has less error with the actual data. Therefore, the relevant features of the separated data can accurately reflect the defect related information and effectively improve the pipeline safety assessment.

Highly effective leakage magnetic field suppression by using a reactive coil in perfectly aligned EV wireless charging systems

Using a reactive coil to suppress the leakage magnetic field (LMF) in wireless power transfer is practical, but the suppression capability reported in the literature is still limited. This paper proposes several methods for improving the suppression capability of this scheme. Three conditions are required to realize this goal, namely (1) a good LMF proportionality, (2) an equation regarding the LMF coefficients and mutual inductances, and (3) an equation regarding the impedance of the reactive coil loop. Coil geometry optimization is performed to meet condition (2), and coil reactance is compensated by a capacitor to meet condition (3). Given the trade-off between LMF suppression capability and efficiency, a control strategy based on a switching capacitor array is adopted. In the experiments, a 97.5% reduction in the LMF strength is achieved on the measurement point with slight effects on efficiency.

Reconfigurable DDP-type transmitter coil for electric vehicle wireless charging under misaligned conditions

This paper presents a new type of a transmitter coil for wireless power transfer (WPT) to assist in the achievement of a constant output power and in the reduction of magnetic field leakage under misaligned electric vehicle (EV) wireless-charging conditions. The proposed DDP coil is an improvement upon the conventional DD coil and can be adaptively reconfigured depending on the misalignment of different sizes or types of receiver coils. The reconfigurable resonant circuit is designed to compensate various coil structures and to maintain a high-energy efficiency. The reconfiguration strategy is presented by studying the characteristics of the magnetic field and mutual inductance of the coils. A precise human anatomic model and a full-scale Tesla EV model are built to evaluate the magnetic field leakage and human exposure to the WPT system. Simulation results show that the power transfer efficiency (PTE) reaches 99.16% and that the maximum electric field induced in humans is − 1.11 dBV/m, while the transfer power is 6.6 kW with a 12 cm lateral offset on both the x-axis and y-axis. The effectiveness of the proposed type of transmitter coil is verified through simulation and experimental results.

Non-Destructive Testing of Steel Corrosion Fluctuation Parameters Based on Spontaneous Magnetic Flux Leakage and Its Relationship with Steel Bar Diameter

In an actual structure, the arrangement of steel bars is complicated, there are many factors affecting the corrosion of steel bars, and these factors affect each other. However, accurately reflecting the corrosion of steel bars in actual engineering through theoretical calculations is difficult. Besides, it is impossible to detect and evaluate steel bars rust completely and accurately. This article is based on spontaneous magnetic leakage detection technology and adopts the method of stage corrosion and scanning along the reinforcing bar. Based on spontaneous magnetic flux leakage detection technology, the linear change rate of the tangential component curve of the magnetic flux leakage signal generated after the corrosion of a steel bar is studied, and a comparison is made between the steel bar coated concrete samples with different steel bar diameters. In this paper, the “origin of magnetic flux leakage signal” is defined as a reference point, which is convenient for effectively comparing the magnetic signal curves under all operating conditions. Besides, the “rust-magnetic fluctuation parameter” is proposed to accurately reflect the sudden change of leakage magnetic field caused by disconnection due to the corrosion of a steel bar. A new data processing method is provided for the non-destructive testing of steel corrosion using the spontaneous magnetic flux leakage effect, which can effectively reduce the influence of steel bar diameter on magnetic flux leakage signal and improve the precision of non-destructive testing technology of steel bar corrosion using the metal magnetic memory effect.

Influence of Crack Size on Stress Evaluation of Ferromagnetic Low Alloy Steel with Metal Magnetic Memory Technology.

Based on the magneto-mechanical effect, the influence of crack size on stress evaluated with metal magnetic memory (MMM) technology was discussed in this paper. Based on equivalent theory, the regular rectangular grooves, with different widths and depths, were precut in the surface of an experimental sample for simulating surface crack, and a three dimensional electrically controlled displacement system was used to collect the Hp(y) signal of the sample under different stresses, and the fracture morphology was observed by using scanning electron microscopy (SEM). The results show that the influence of detection line on Hp(y) signal can be ignored; as stress increases, the Hp(y) signal turns counterclockwise around zero-crossing point and its mutation, corresponding to the location of groove, becomes distinct gradually. When groove depth is constant, the magnetic intensity gradient changes in the form of quadratic polynomial as groove width increases, and when the groove width is the same, the magnetic intensity gradient is a linear function of groove depth. When stress reaches the yield strength of the material, the magnetic intensity gradient decreases gradually as stress increases further, and the orientation of magnetic domain is seen as the main reason for that result. At last, the experimental results are discussed based on the piezomagnetic effect and leakage magnetic field theory of finite depth slit model, and the change of magnetic domain orientation is considered to be the main reason.