Eddy Current Effects Research Articles

A metal object detection system for electric vehicle wireless charging with quadrupole detection coils

In the practical application of magnetic coupling wireless charging technology, the absence of direct contact between the receiver and transmitter usually leads to metal objects (MOs) entering the charging area. The strong magnetic field between the receiver and transmitter causes eddy current effects and generates large amounts of heat in MOs, which may lead to serious hazards such as fires, so it is necessary to detect accidental entry of MOs. In this paper, a novel detection coil layout suitable for wireless charging of electric vehicles (EVs) has been proposed, which consists of multiple quadrupole coils arranged to achieve decoupling from the receiver and the transmitter to minimize the effect on the system efficiency. The influence of the presence of MOs on the equivalent inductance and equivalent resistance of the quadrupole detection coil has been deduced. The simulation results show that the maximum self-inductance change rate of the proposed detection coil reaches 28.11%, and a high self-inductance variation rate is also achieved at the edge of the detection coil.

Identification and classification of bearing steel bars based on low-frequency eddy current detection method

Raw material testing is of great significance to guarantee the reliability of bearing ring production. Traditional testing methods such as spark identification are unable to run online, leading to the risk of raw material misuse in bearing ring production. To this end, this paper develops a low-frequency differential eddy current detection method for identifying and classifying raw materials of bearing steel bars. Firstly, the distribution of eddy current density inside bars and effects of excitation signals on the induced signals are discussed via numerical simulation. Then, the low-frequency eddy current detection experimental system with a phase-locked amplifier algorithm is established. Experiment results shows that the method developed in this study can distinguish between carbon steel and bearing steel reliably, identify the furnace number and heat treatment modes of bearing steel bars effectively, laying the foundation for online detection of raw material during bearing production.

A Novel Dual-Differential Edge Sensor Based on the Eddy Current Effect

In this article, a kind of edge sensor based on the eddy current effect is proposed to realize accurate detection of the nano-level resolution in a large temperature span. Compared with edge sensors with different principles used in optical telescope projects, eddy current edge sensor has the advantages of being insensitive to nontarget direction and immune to nonferromagnetic medium. The proposed dual-differential edge sensor (DDES) greatly simplifies its installation and reduces the number of support components for sensors to half by replacing the complementary symmetrical installation method. By analyzing the detection principle, a kind of precise demodulation circuit and real-time temperature compensation method is also designed to guarantee the sensor’s ultrahigh stability. The prototype of the sensor is manufactured and verified that the resolution can reach within 2 nm in the range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$300 ~\mu \text{m}$ </tex-math></inline-formula> , and the temperature drift (TD) performance is less than 6 nm/°C under the large temperature span from −25 °C to +25 °C. The installation error measurement convinced that the current structure has an excellent installation error tolerance, which has the potential to apply in the engineering application of astronomical telescope mirror splicing.

Semiexplicit time integration of a reduced magnetic vector potential magneto‐quasistatic field formulation

AbstractIn this article, a reduced vector potential formulation for transient magneto‐quasistatic field problems is presented. The finite element method for spatial discretization yields a system of differential algebraic equations (DAE). Applying a generalized Schur complement the DAE system decomposes into a system of ordinary differential equations (ODE) and an algebraic equation. In order to avoid computationally expensive linearization schemes to solve nonlinear eddy current problems the ODE system is integrated in time using a semiexplicit Euler scheme. The vector potential is split into a source vector potential and a reduced vector potential which describes the eddy current and magnetization effects. The reduced formulation is compared with the underlying nonreduced formulation regarding the overall performance. In addition, the proper orthogonal decomposition method is applied to the iterative preconditioned conjugate gradient method to minimize the number of iterations per time step.

Estimation of DC Hysteresis Property Using Nonlinear Eddy Current Analysis Considering Hysteretic Property

The DC hysteresis property should be considered in the nonlinear eddy current analysis for accurate hysteresis loop and iron loss calculation of iron cores composed of silicon steels. However, the DC hysteresis property is usually measured at ultra-low frequency (e.g., 0.01 Hz) and it is quite difficult due to very low signal to noise ratio. In this paper, we proposed a method to derive the DC hysteresis property from the AC hysteresis property measured at 20 Hz, which is relatively easy to be measured. The eddy current effect in the 20 Hz hysteresis loop is removed by using an iterative eddy current analysis considering hysteretic property. The estimated DC hysteresis property obtained from the proposed method are compared with those obtained from a conventional estimation method. Finally, the obtained DC hysteresis property are used in the AC hysteresis loops and iron losses calculation (50∼1 kHz) of a non-oriented silicon steel and compared with the measured ones. The hysteresis loops and iron losses can be well represented.

Low-Frequency NARS (LF NARS) by the use of a superheterodyne EPR spectrometer

In this article, the possibilities of recording EPR spectra by the non-adiabatic rapid sweep (NARS) method on a superheterodyne spectrometer are investigated. This method allows recording the pure EPR absorption spectrum of the object under investigation without the need for lineshape–lineheight compromise, while increasing sensitivity by suppressing low-frequency noise. In the NARS method, a low-amplitude sinusoidal modulation of a magnetic field is not used, and an oscillating triangular-shaped bipolar magnetic field is superimposed on the main permanent magnetic field. The triangular field repetition rate should be higher than that of the undesirable noise, and the amplitude is such that the rate of field change satisfies the Bloch non-adiabaticity criterion. The EPR absorption signal is digitized by a fast ADC and accumulated over a large number (n) of triangular field periods. In this case, for low-frequency noise, the spectrum of which is located below the repetition frequency of the triangular field, an accumulation process occurs with an increase in the signal-to-noise ratio (SNR) in proportion to n. A remarkable property of a superheterodyne spectrometer is that the frequency below which low-frequency noise prevails over white noise is significantly lower for it than for a homodyne spectrometer. This allows the use of a low repetition rate (LF NARS), which makes it much easier to obtain a highly linear triangular field of significant amplitude even in microwave resonators with a massive metal case since the harmful effects of eddy currents are reduced. The conditions of non-adiabaticity become easily feasible. At the same time, the noise suppression effect during accumulation turns out to be so significant that the SNR of the LFNARS spectrum exceeds that of the traditional spectrum with magnetic field modulation, with the same recording time, by more than 10 times.

Science on a stick: An experimental and demonstration platform for learning several physical principles

We share the design for a simple apparatus that, when paired with an Arduino processor and a computer, can be used in a wide range of laboratory measurements: observing linear kinematics, confirming Faraday's and Lenz's laws, measuring magnetic moments, and observing the effects of eddy currents. The setup is simple, inexpensive, easy to replicate, and can even be fabricated and used by students working at home.

High-Sensitivity Detection Method for Metal Foreign Objects Based on Frequency Optimization in Wireless Electric Vehicles Charging

Metal foreign objects will not only reduce the output power and efficiency of the wireless power transfer (WPT) system, but also will be heated under the eddy current effect. The method based on the detection coil array has been wildly adopted for foreign object detection (FOD), especially in high-power level WPT applications. However, the problems of low sensitivity or misjudgment still exist which leads to a safety hazard. Therefore, high sensitivity of the foreign object-detection method based on the excitation frequency optimization has been proposed in this paper. Based on the impedance change of the detection coil caused by the foreign object coupling, the frequency characteristics of detection sensitivity were analyzed under the conditions of different self-inductance detection coils. Then, the detection coil was designed and its corresponding optimal excitation frequency was selected to achieve the optimal detection effect to eliminate the area of low detection sensitivity. Finally, an FOD experimental prototype was established to verify the proposed frequency optimization strategy. The results show that the sensitivity of the FOD system is up to 97.56%. With the optimal excitation frequency of 6.22 MHz, as for 1-yuan coin in the center position and corner position of the detection coil, the detection sensitivity is 92.89% and 40.16%, respectively, which is 22.13% and 23.89% higher than that of the excitation frequency is 1 MHz. The improvement of detection sensitivity is helpful to detect accurately and eliminate the detection blind area.

Ultra-broadband microwave absorption of honeycomb-like three-dimensional carbon foams embedded with zero-dimensional magnetic quantum dots

The magnetic response behavior of microwave absorbing materials (MAMs) is beneficial to the expansion of the effective bandwidth in the high-frequency electromagnetic fields. However, the high density of magnetic components does not match with the lightweight requirement of MAMs. In response to this contradiction, the metal-organic framework (MOF) ZIF-67 material and melamine foam were used in the present work as the magnetic component and self-sacrificial template, respectively. A three-dimensional honeycomb carbon foam with zero-dimensional magnetic Co quantum dots (Co-QDs/CF) was prepared by a simple two-step method. The unique honeycomb structure significantly improved impedance matching and carrier mobility, providing more scattering paths for the electromagnetic wave conduction while reducing the overall density. In turn, the uniformly embedded magnetic Co-QDs endowed the 3D carbon foam with excellent high-frequency magnetic response while ensuring light weight. The ultra-small size (<10 nm) enhanced the exchange coupling between magnetic particles while suppressing the eddy current effect, and the magnetic loss capability was greatly improved. Interestingly, Co-QDs acting as numerous micro-resistors formed a large three-dimensional conductive network with the carbon skeleton, which demonstrated outstanding electron transport ability, so that the conductance loss was significantly enhanced. Surprisingly, the effective absorption bandwidth of Co-QDs/CF in the 2–18 GHz band was as high as 8.74 GHz with a matching thickness of 2.5 mm, while the corresponding filling rate was only 20 wt%. Thus, the proposed ingenious strategy to construct three-dimensional conductive networks using ultra-small magnetic quantum dots opens up new prospects for the development of lightweight broadband MAMs.

Design Process of Post-Assembly 3-Times Magnetizer for 10-Poles of Flux Concentrated Rotor Considering Eddy Current Effect

The post-assembly magnetizer for flux concentrated rotor of permanent magnet synchronous motor is dealt with in this paper. The design process of a magnetizer that is able to fully magnetize the permanent magnet (PM) inserted rotor core assembly within 3-times is discussed. The number of turns of the Main-pole winding and the Inter-pole winding was determined to maximize the magnetization ratio in each magnetization stage. At the same time, demagnetization characteristic is also examined. When the magnetizer is designed, the number of turns of winding is determined considering the eddy current generated in the core. The magnetization ratio of the PM considering the eddy current effect is compared with the magnetization ratio of the designed magnetizer when the eddy current effect is ignored. Finally, the properties of the finally designed magnetizer are verified through fabricated magnetizer and experiments.

Design and Verification of Metal Foreign Body Detection Device for Harvester Based on Eddy Current Effect

Highlights Prevent metal foreign bodies from scratching the intestines of animals and damaging the harvest cutter. Highly integrated design of acquisition circuit. Application of electromagnetic simulation to verify the feasibility of the principle of eddy current effect. Establishment of Support Vector Machine Multi-Classification Algorithm Model. Abstract. Aiming at the problem that the metal foreign bodies mingled in the silage cause damage to the gastrointestinal tract of animals and livestock, as well as irreversible damage to the rotary cutter of the harvester, a metal foreign body detection and sensing device for the harvester feeding drum composed of multiple single coils and signal acquisition units was designed to realize real-time detection and alarm of metal foreign bodies during harvesting. The sensor adopted a monolithic design with high integration of the signal acquisition circuit, which has a strong anti-interference ability. First, the electromagnetic simulation model was established. According to the simulation analysis of the eddy current effect, when the metal foreign object enters the alternating magnetic field, the energy will be lost, and the equivalent impedance of the coil will change accordingly. Then, the existence of the metal foreign body can be determined by detecting the equivalent impedance Rp of the coil. Next, we adopted a support vector machine multi-classification algorithm to train the detection device. In this process, different sizes of metal (copper, aluminum, and iron) were used, which can effectively improve the sensitivity and accuracy of metal foreign body detection. Finally, the sensor was installed on the test stand for multi-scene simulation experiments. The results show that the metal detection sensor can quickly identify the existence of metal by detecting the equivalent impedance Rp based on the eddy current effect; at the same time, the size of this sensor for metal foreign body detection is limited to 0.6 mm in diameter, 12 mm in length, and 100 mm in maximum detecting distance. Keywords: Eddy current effect, Equivalent impedance, Harvester, Metal foreign body, Support vector machine.

Real‐Time Strain Detection Technology for Steel Structures Based on Eddy Current Effect

To avoid strains in steel structures in special equipment caused by excessive alternating loads, which cause stress concentrations in local areas and reduce the strength and pressure‐bearing capacity of the steel structures, a method for evaluating the strain state of the steel structures using the eddy current effect is proposed, and the relevant testing device is developed. The RMS voltage and tension values were tested and fitted linearly with sampling time, and their linear correlations after fitting were 0.9978560 and 0.9967905, respectively. To investigate the method’s practical application, the effect of strain on the impedance of the eddy current probe was first studied theoretically, followed by the design and fabrication of a strain detection device comprised of an eddy current probe and a signal processing system. Finally, tensile strain experiments were carried out on 5 mm thick standard Q235 steel tensile specimens using a universal tensile machine and the linear equation of RMS voltage versus strain was obtained analytically. Theoretical and experimental tests have shown that the device can detect each strain stage and quantify the strain within the elastic stage by fitting a linear equation.

Speed Measurement Feasibility by Eddy Current Effect in the High-Speed MFL Testing

Speed Measurement Feasibility by Eddy Current Effect in the High-Speed MFL Testing

Magnetic and loss characteristics of &lt;b&gt;γ&lt;/b&gt;&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N soft magnetic composites

Soft magnetic composite materials are prepared by mixing magnetic materials and insulating materials, which possess both the excellent magnetism of magnetic materials and the low resistivity of insulating materials. They possess broad application prospects in emerging power electronics industries such as photovoltaic inverters, new energy vehicles, and charging stations. The third-generation high-frequency wide bandgap semiconductors, mainly composed of SiC and GaN, have the operating frequency of soft magnetic materials raised to MHz. However, current soft magnetic materials have significant core losses at high frequencies. Therefore, people are focus their attention on developing new soft magnetic composite materials to reduce iron core losses at high frequencies. In this paper, γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N with high resistivity is prepared by nitriding carbonyl iron powders, showing its excellent soft magnetic properties, and the γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N is ball-milled to become easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N powder. Compared with the none easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N powders, the none easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N powders are spherical in shape, the easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N powders exhibit a high aspect to thickness ratio in sheet shape. The obtained easy plane powders are mixed with polyurethane insulation to make the soft magnetic composite. There is a significant difference between the in-plane and out-of-plane hysteresis loop of the magnetostatic easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N soft magnetic composite, and the in-plane hysteresis loop is more easily magnetized to saturation state. The degree of plane orientation is 98.46%. The fitting analysis results of the Jiles-Atherton model also prove its easy plane characteristic, and has higher effective permeability and lower power loss than the counterparts of the none easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N composite that is not ball-milled. After loss separation, it is found that in a low frequency range, hysteresis loss is the main loss, while in a high frequency range, the excess loss will surpass the hysteresis loss, acting as the main loss, the magnetostatic easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N soft magnetic composites material reduces hysteresis loss and excess loss. Comparing with similar soft magnetic composites, the eddy current effect in magnetic iron particles is reduced by nitriding process, and the magnetostatic easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N soft magnetic composite has excellent high-frequency soft magnetic properties. Magnetostatic easy plane γ&lt;i&gt;'&lt;/i&gt;-Fe&lt;sub&gt;4&lt;/sub&gt;N provides a new idea for the high-frequency application of soft magnetic composites matching the third generation wide bandgap semiconductors.

Eddy-Current Lift-Off Effect Compensation for 3-D Printed Ti-6Al-4V Components With Various Electrical Conductivities

Eddy-Current Lift-Off Effect Compensation for 3-D Printed Ti-6Al-4V Components With Various Electrical Conductivities

Design of orthogonal directional shear horizontal electromagnetic acoustic transducer

This research proposed an electromagnetic acoustic transducer (EMAT) for generating and receiving orthogonal directional shear horizontal (ODSH) guided waves in the metal plate-like structure. The proposed EMAT generates the fundamental mode of SH wave in the horizontal and vertical direction in the plane of the test sample. The ODSHEMAT combines a new Chevron-like coil design which generates an eddy current effect in the skin depth of the plate surface, and a periodic permanent magnet that applies a static magnetic field vertically with a periodicity equal to its wavelength. The direction of the resultant Lorentz force acting on the test surface-controlled PPM underneath a specific chevron angle of the coil wire. The constructive interference of propagated waves has been developed in the orthogonal directions, enhancing the ultrasonic signals and improving the signal-to-noise ratio. A finite element simulation has been carried out with a thin aluminum plate, keeping the proposed EMAT at the center of the sample. Further, the simulation results show good agreement with the proposed design.

DETERMINATION OF THE PHYSICO-CHEMICAL CHARACTERISTICS OF A MAGNETIC LIQUID IN THE IMPLEMENTATION OF THE METHOD BASED ON AN ELECTROMAGNETIC CONVERTER

A non-contact three-parameter electromagnetic method for measuring magnetic susceptibility κ, electrical conductivity χ, and temperature t of a ferrofluid sample is proposed. Theoretical principles of the operation of the inductive parametric electromagnetic transducer (IPET) with a sample of ferro-fluid are considered. As a result of studies of the universal functions of transformation of the IPET with a sample of the ferro-fluid, the theoretical provisions of the work of the IPET were further developed, which are related to the possibility of estimating the static parameters of the magnetic fluid. Because record of the effect of eddy currents leads to the need to determine three parameters of magnetic fluids with only one IPET, the necessity of using an inductive IPET switching circuit with a ferro-fluid sample, which provides for compensation of interfering external inductance L1 using a compensating capacitance P567 to improve the accuracy of measurements of the physical and chemical parameters of magnetic fluids, has been proved. The operation of the circuit is based on the fact that the eddy EMF excites a magnetic flux in the sample of the magnetic fluid under study, which is added geometrically with the excited magnetic flux from an external source, creating the resulting magnetic flux Ф2t in the sample of the magnetic fluid under study, while the resulting magnetic flux decreases in magnitude and shifts by the phase angle in relation to the excited magnetic flux, all this leads to a change in the components of the signals of the IPET, that is: inductance Lit and resistance Ω2t, which are associated with the physicochemical parameters κ, χ and t of the magnetic fluid sample. In further studies, in order to increase the efficiency of wastewater treatment of a mini-brewery, it is recommended to use a magnetic fluid in complex cleaning methods that involve the use of magnetic fluids in filters for post-treatment of wastewater from food production of acidic and alkaline composition.

Multiple physical field coupling simulation of high current lithium electrolyzer in industry

AbstractThe electric field, thermal field, and velocity field in a 60 kA diaphragmless lithium electrolyzer are studied by multiple physical field coupling simulations. The current density distribution, the balance of heat generation, heat dissipation, and the flow field distribution of the lithium electrolyzer are discussed. The velocity distribution is solved by the Euler–Euler two‐phase flow model, and the turbulent flow of electrolyte is solved by the k–ε method. The results show that in an electric‐heat field, there is a constant ratio of current loss, and the current density distribution is not uniform. The electrolyte temperature is evenly distributed, wherein thermal radiation plays a dominant role. In addition, it is found that the velocity distribution of the end‐side interpolar space and the inside interpolar space is different. The influence of electrode distance in the range of 30~60 mm on the flow field is investigated, and the dominance of the electrode distance effect and the eddy current effect is analyzed. The optimal range of electrode distance is 40~50 mm.

Design of underwater magnetostrictive longitudinal-type transducers with circuit model considering eddy currents and multi-rod structure

Underwater magnetostrictive longitudinal-type transducers (UMLT) are widely used for high-power sonar applications to generate sound waves. When designing an UMLT, to establish an effective model is one of the most necessary but difficult tasks. However, due to the special properties of giant magnetostrictive materials (GMM), the traditional design methods of transducer are completely inapplicable. Therefore, an electro-magneto-mechanical multi-field coupling model is established in this paper, and the eddy current effect, multi-GMM rod structure and other factors are fully considered. Based on the model, the resonant frequency, impedance characteristics and transmitting current response can be calculated to guide the design of UMLT. To verify the feasibility of the proposed model, a measurement experiment platform is constructed. The results validate that the proposed model is effective and more accurate than the conventional model. Thus, it can also be considered as a guideline for the design and analysis of UMLT.

Fast measurement of the gradient system transfer function at 7 T.

In this work, a new method to determine the gradient system transfer function (GSTF) with high frequency resolution and high SNR is presented, using fast and simple phantom measurements. The GSTF is an effective instrument for hardware characterization and calibration, which can be used to correct for gradient distortions, or enhance gradient fidelity. The thin-slice approach for phantom-based measurements of the GSTF is expanded by adding excitations that are shifted after the application of the probing gradient, to capture long-lasting field fluctuations with high SNR. A physics-informed regularization procedure is implemented to derive high-quality transfer functions from a small number of measurements. The resulting GSTFs are evaluated by means of gradient time-course estimation and pre-emphasis of a trapezoidal test gradient on a 7T scanner. The GSTFs determined with the proposed method capture sharp mechanical resonances with a high level of detail. The measured trapezoidal gradient progressions are authentically reproduced by the GSTF estimations on all three axes. The GSTF-based pre-emphasis considerably improves the gradient fidelity in the plateau phase of the test gradient and almost completely eliminates lingering field oscillations. The presented approach allows fast and simple characterization of gradient field fluctuations caused by long-living eddy current and vibration effects, which become more pronounced at ultrahigh field strengths.