Magnetic Leakage Research Articles

Shaking Noise Exploration and Elimination for Detecting Local Flaws of Steel Wire Ropes Based on Magnetic Flux Leakages

Nowadays, steel wire rope (SWR) plays a more and more crucial role in modern facilities including but not limited to goods transmission, elevators, and dams. Due to the external environment, local flaws (LFs) on the SWR may cause deadly accidents. Thus, its health condition should be monitored. When applying the magnetic flux leakage (MFL) based nondestructive testing method to collect the LF signals in multichannel, the shaking noise inevitably exists, and greatly influences the accuracy of LF detection. This article focuses on analyzing shaking sources and the representation of shaking noise in MFL signals based on the lift-off distance. Then, after analyzing morphological features of shaking noise, strand noise, and LF signals, the morphological image processing based method is proposed to suppress shaking noise, especially when LF signals are covered and surrounded by strong shaking noise. In comparison with the state-of-the-art denoising method, this proposed method not only suppresses both strand noise and strong shaking noise but also improves the signal-to-noise ratio of MFL signals for better LF detection.

Influence of heterostructure on structure, electric and magnetic properties of Bi0.5(Na0.80,K0.20)0.5TiO3/BaZrO3 films prepared by the sol–gel method

This study reports on the structure, electric, and magnetic properties of Bi0.5(Na0.80,K0.20)0.5TiO3/BaZrO3 (BNKT/BZO) heterolayered films synthesized via chemical solution deposition on Pt/Ti/SiO2/Si substrates. The influence of different heterolayered configurations on the microstructure, electric and magnetic properties of the films was investigated thoroughly. The heterostructures are expected to generate strongly correlated electron systems in the BNKT and BZO layers that cause a magnetic interface effect in the BNKT/BZO conjunction layer. The BZO layer also prevents metal ion evaporation, resulting in a decline in oxygen vacancies and an enhancement in the electric and magnetic properties. The obtained results show that magnetic properties and leakage current density (J) of BNKT/BZO heterolayered films were greatly improved thanks to the heterolayered structure. Heterolayered 4BNKT/2BZO films (M42) yield the highest M s and M r values of 14.4 emu cm−3 and 1.7 emu cm−3, respectively, about three times higher than multilayered BNKT. Thanks to heterolayered structure, J decreases strongly from 16.0 × 10−4 A cm−2 for BNKT films to 1.4 × 10−4 A cm−2 for heterolayered M42 films. It has been verified that the leakage current in BNKT/BZO heterolayered films follows the Schottky barrier mechanism, with the barrier height fluctuating between 0.80 eV and 0.92 eV. The results of the study show that BNKT/BZO heterolayered films may be suitable for use in environmentally friendly multifunction devices.

Demagnetization Fault Diagnosis of Permanent Magnet Synchronous Motors Using Magnetic Leakage Signals

In most industrial applications, it is difficult to obtain complete demagnetization fault signals of all conditions with labels for permanent magnet synchronous motor (PMSM), and motors are not allowed to be disassembled, so non-contact diagnostic methods are essential. A non-contact fault diagnosis method using magnetic leakage signal based on wavelet scattering convolution network (WSCN) and semi-supervised deep rule-based (SSDRB) classifier is proposed. Through magnetic equivalent circuit model analysis, the magnetic leakage signal on motor surface is selected as fault signal. To avoid complex signal processing, the symmetrized dot pattern method is introduced to convert fault signals into two-dimensional images. Then, WSCN is applied to extract features from images, and SSDRB classifier is adopted to diagnose demagnetization fault. Finally, faulty motor prototypes are manufactured for experiment. By comparing with other methods, the superiority and effectiveness of the proposed method using a small number of labeled samples under different conditions are verified.

Research on Short-Circuit Impedance Analysis Method of Auto-transformer for Side Column Voltage Regulation

In order to realize the accurate analysis of the impedance of transformers with complex connection relations, this paper derives the impedance calculation method of low-voltage excitation side column linear voltage regulating autotransformer by using the power method. The transformer network with different taps is analyzed, and the calculation formulas of transformer HV-MV impedance, HV-LV impedance and MV-LV impedance are derived. The analysis is simplified to the solution of concentric column coil impedance and magnetic potential of each coil. By comparing the calculated data of actual products with the measured data, the calculation deviation of this method is controlled within 2.03%; By using the finite element method, the impedance of the transformer with the measures to control the magnetic shielding is analyzed and calculated. By comparing the impedance of the transformer with different measures, it can be confirmed that the magnetic leakage measures have an impact on the impedance of the transformer.

Rail Magnetic Flux Leakage Detection and Data Analysis Based on Double-Track Flaw Detection Vehicle

The rapid development of the railway industry has brought convenience to people’s lives. However, with the high speed, high frequency and heavy load characteristics of rail use, the safety of rail is seriously threatened. In this paper, a magnetic flux leakage testing (MFL) detection technology of rail based on a double-track flaw detection vehicle is introduced in detail, which can effectively detect the damage of rail top surface, which is the blind area of ultrasonic detection. The magnetic dipole model is used to analyze that the leakage magnetic field in the direction of Bx and Bz above the damage is related to the depth and width of the damage. The relationship between the depth of the damage and the leakage magnetic field is quantitatively studied for the damage with fixed width but varying depth. The finite element simulation tool is used to model and simulate the damage at different depths. After analyzing the different characteristic values, it is found that the peak value of magnetic leakage signal has a certain correlation with the depth of damage, and the natural logarithm function is fitted out—VBx = 0.1451ln(b) + 0.2705, VBz = 2.7787ln(b) + 0.0087. In order to verify the prediction function of the injury depth fitted by the simulation data, the human injury with different depths was processed and the dual-track flaw detector was used to carry out the experiment of high-speed detection environment. The peak-to-peak fitting of the magnetic leakage signals in the direction of Bx and Bz of the experimental results shows that the peak-to-peak variation rule is roughly in line with the natural logarithm function in the simulation. The correlation between the fitting results of the experimental data and the simulation fitting function is analyzed using the Pearson coefficient. The Pearson coefficient in the direction of Bx is ρx = 0.91386. The Pearson coefficient of the Bz direction is ρz = 0.98597, the peak-to-peak value of Bx and Bz direction is positively correlated with the depth of damage and the fitting effect of the Bz direction is better than that of the Bx direction.

Simulating mechanical properties of human tissues or organs based on magnetorheological fluid for tactile display

Robot-assisted minimally invasive surgery enables surgeons to tele-perform elaborate surgical operations to patients with less damage and pain. Besides force feedback provided by the surgical robot to the surgeon, touching sensations are also important for the surgeon to acquire the complete conditions of the patient. Thus, tactile display devices are crucial elements in surgical robots. Meanwhile, various sensations of magnetorheological (MR) fluid can be provided to human fingers because its stiffness, elasticity, and viscosity can be controlled by applied magnetic field. Therefore, in this paper, a new tactile display device based on MR fluid is proposed. This device has high magnetic conduction efficiency, less magnetic leakage, no MR fluid leakage, and overcomes the major drawbacks of the existing tactile display devices based on MR fluid in literatures. Firstly, the design of the tactile display device is described in detail, followed by its fabrication and assembling methods. Secondly, the working current range of the tactile display device is determined by using electromagnetic finite element method (FEM) simulation. Thirdly, the mathematical model to characterize the compression and shear behaviors of the tactile display device is developed. Then, the tactile display device is tested in terms of normal and shear contact forces, followed by its elastic and shear moduli analysis. Finally, the unknown parameters in the mathematical model are figured out, and the model is validated by using structural FEM simulation. The experimental results show that the elastic and shear modulus range of the proposed tactile display device are respectively 3–7.5 kPa and 1.4–5.0 kPa, which can cover the mechanical properties of various human viscera.

Evaluation of the Behaviour of Steel Bar in the Concrete under Cyclic Loading Using Magnetic Flux Leakage and Acoustic Emission Techniques

The behaviour of the steel bar in concrete under cyclic loading has been evaluated using magnetic flux leakage associated with acoustic emission monitoring technique. Visual observation was used to observe the deformation of the beam under cyclic loading. The sensors of metal magnetic memory were scanned in the middle of the beam at a distance of 320 mm at the bottom part. Twenty-two cyclic ranges were performed for cyclic loading of 100 or 200 cycles for each range, with a frequency of 1 Hz and a sinusoidal wave mode. The magnetic flux leakage signal, acoustic emission characteristics and crack width were measured and analysed to evaluate the behaviour of the steel bar in the concrete beam. The magnetic flux leakage signal and acoustic emission energy results were well matched with the occurrence of cracks at the centre of the beam. It was found that the relationship between the magnetic leakage flux signal and crack opening showed a strong correlation with R2 of 0.969. A high acoustic emission energy of 1300 nVs is observed at the centre of the beam. Based on the results, the behaviour of the steel in the concrete beam can be determined by the integrity assessment of a structure.

Quantitative Detection of Tank Floor Defects by Pseudo-Color Imaging of Three-Dimensional Magnetic Flux Leakage Signals

Highly integrated three-dimensional magnetic sensors have just been developed and have been used in some fields, such as angle measurement of moving objects. The sensor used in this paper is a three-dimensional magnetic sensor with three Hall probes highly integrated inside; 15 sensors are used to design the sensor array and then measure the magnetic field leakage of the steel plate; the three-dimensional component characteristics of the magnetic field leakage are used to determine the defect area. Pseudo-color imaging is the most widely used in the imaging field. In this paper, color imaging is used to process magnetic field data. Compared with analyzing the three-dimensional magnetic field information obtained directly, this paper converts the magnetic field information into color image information through pseudo-color imaging and then obtains the color moment characteristic values of the color image in the defect area. Moreover, the least-square support-vector machine and particle swarm optimization (PSO-LSSVM) algorithm are used to quantitatively identify the defects. The results show that the three-dimensional component of the magnetic field leakage can effectively determine the area range of defects, and it is feasible to use the color image characteristic value of the three-dimensional magnetic field leakage signal to identify defects quantitatively. Compared with a single component, the three-dimensional component can effectively improve the identification rate of defects.

An Enhanced Magnetic Equivalent Circuit Model for a Magnetorheological Clutch Including Nonlinear Permeability, Flux Fringing, and Leakage Effects

Magnetorheological (MR) clutches have significant potential in electromechanical interface and are a promising technology with high commercial value in the automotive industry. A quick and precise magnetic circuit modeling method is demanded to calculate performance or optimize design of the MR clutch. Conventional magnetic circuit models present poor accuracy because they often fail to accurately include nonlinearities such as magnetic saturation, magnetic fringing, and magnetic leakage. In this regard, an enhanced magnetic equivalent circuit (EMEC) model based on lumped parameter method is proposed. This model can not only cope with clutch geometry and material properties (nonlinear permeability) but can also consider flux fringing and leakage effects. Combined with the specific structure, formulae for the calculation of fringing permeances and leakage permeances in the magnetic circuit of the MR clutch are presented. Finite-element analysis (FEA) and experimental results show that the proposed EMEC model can provide better accuracy compared with magnetic equivalent circuit (MEC) model from available literature and provide less computational effort compared with FEA. Moreover, the influence of design parameters corresponding to device geometry and material properties on the output flux density is discussed based on the proposed EMEC model. All taken together, the proposed EMEC model provides a comprehensive knowledge in optimize design and performance prediction of MR device.

Mutual Inductance Calculation of Circular Coils for an Arbitrary Position With a Finite Magnetic Core in Wireless Power Transfer Systems

Mutual inductance can be increased, and magnetic leakage can be reduced by adding finite magnetic core materials to the coil structure. However, the problem of the calculation of the mutual inductance between two arbitrarily positioned circular coils with a finite magnetic core has not been resolved. In this article, an analytical formula for calculating the mutual inductance between two circular coaxial coils on a finite magnetic core is obtained based on regional hierarchical expansion analysis (RHEA), the Maxwell equation, the Bessel function, and the boundary conditions for electromagnetic fields. The mutual inductance between two arbitrarily positioned coils is obtained by using the analytical geometry method. A series of experiments are carried out to verify the analytic calculations. The experimental results for each misalignment case are compared with the calculated results and simulated results. The theoretical results and simulated results are in good agreement with the experimental data, which verifies the validity of the proposed method.

Double-Sandwich Magnetic Coupling Structure Design for Dual-LCL Wireless Charging System in EV Applications

In the wireless charging system of EVs, the traditional single-stage LC resonance network has the issues of narrower of parameter design and small equivalent input impedance. While the composite resonant network will introduce additional resonant capacitors and inductors, which increases the system volume, cost, and reduces the efficiency. This paper proposes a design scheme of double-sandwich magnetic coupling structure with a low cross-coupling coefficient, which integrates the resonant inductors into the power transmitter and receiver, and it is designed taking the magnetic leakage and loss as constraints. A 500W prototype is built, and the comparison of experimental efficiencies between the double-sandwich and the separate magnetic coupling structures is performed. Finally, the effectiveness of the integrated design scheme is validated.

Two-Dimensional Analytical Models for Cogging Torque Prediction in Interior Permanent Magnet Machine

Analytical prediction of cogging torque needs accurate flux density and relative permeance closed-form expressions. The accurate two-dimensional (2D) air gap flux density distribution function and the 2D permeance function are currently almost always applied to surface-mounted permanent magnet (SPM) machines, instead of interior permanent magnet (IPM) machines, due to complications from IPMs severe magnetic saturation and leakage flux. To address these issues, this paper proposes a set of new methods to derive the accurate closed-form 2D expressions of IPMs for both flux density and relative permeance. As for the flux density 2D model, a virtual equivalence model for IPM is introduced, so that Laplace’s equation and quasi-Poisson equation can be directly applied to IPM. As for permeance, the same virtual equivalence model also enables 2D models derivation for IPM. Subsequently, the resulting cogging torque analytical expression is obtained with the accurate relative permeance and air gap flux density models. The results from the proposed 2D analytical models showed similar accuracy to the finite element analysis (FEA). In addition, as demonstrated, the proposed 2D analytical models is a highly efficient tool set in the design process of cogging torque optimization, facilitating fast evaluation of different design factors.

Study on the characteristics of power transmission side of leaky magnetic field canceling coil for non-contact power transfer while in operation

Recently, automated guided vehicles (AGVs) have been deployed in factories to improve work efficiency and reduce labor shortages. However, current power supply systems, such as AGV shift systems and battery replacement systems, cannot fully utilize the advantages of these systems because of the time they are inactive. Therefore, to improve work efficiency, we have adopted an in-transit non-contact power supply system that can supply power while the work is in progress and while the machine is moving. There are several non-contact power supply methods; however, the most widely used electromagnetic induction method was used in this study. Compared to conventional non-contact power transfer, a stable power supply and reduction of magnetic leakage field are more important for non-contact power transfer while traveling because of its characteristic of transferring power over a long section of the track. Therefore, we investigated the characteristics of a cancellation coil with enhanced effectiveness based on an 8-shaped coil that reduces the leakage of magnetic fields using electromagnetic field analysis simulations. We then fabricated a feeding coil and verified its effectiveness using actual measurements. As a result, it was confirmed that the cancellation coil has superior magnetic field leakage reduction performance compared to the ordinary 8-shaped coil.

Three-Phase Inverter Fed Adjustable Field IPMSM Drive Utilizing Zero-Sequence Current

This article proposes a three-phase four-wire inverter drive system for an adjustable field interior permanent magnet synchronous motor utilizing magnetic saturation. The magnetic saturation is regarded as a phenomenon of a decrease in permeability depending on an extra magnetic field. In the proposed motor, the number of flux linkage can be controlled by modulating the permeability of magnetic leakage paths in the rotor. However, the proposed adjustable field method requires an additional magnetomotive force (m.m.f.) to control the permeability. Therefore, a zero-sequence current <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> fed by the three-phase four-wire inverter is utilized as the additional m.m.f. source. Thereby, the field control can be achieved with a simple three-phase inverter without sacrificing the number of switching devices compared with conventional motor drives. In the article, the control algorithm of the three-phase four-wire inverter is discussed, and its usefulness is verified by comparing the proposed drive system with other methods or systems.

A Magnetic Field Containment Method for an IPT System with Multiple Transmitting Coils Based on Reflective Properties

Inductive power transfer (IPT) systems with multiple transmitting coils are mainly used in specific scenarios, such as IPT sharing platforms and dynamic wireless charging of electric vehicles, etc. However, it faces problems of electromagnetic field leakage and low efficiency. A new magnetic field containment method based on reflective properties is proposed to solve the above shortcomings. Firstly, the reflective properties and performance figures of the IPT system with a unified passive compensation network are described and derived. Then, an S−LCL topology appropriate for the time−varying coupling IPT system is presented, where the IPT system’s transmitter consists of multiple coils that are compatible with one or more moving receivers and is powered by an inverter. Then, magnetic field focusing, power transfer and overall efficiency are analyzed and simulated. Finally, an experimental prototype is built to validate the feasibility of the proposed system. The experimental results show that the proposed method can increase the power transfer of the coupled transmitting coil and reduce the magnetic field leakage of the standby transmitting coils without complex shielding measures, switch, position detection and communication circuits.

Investigation of the effect of initial magnetization state on the force-magnetic coupling effect of rebars

To investigate the effect of the initial magnetization state on the force-magnetic coupling effect of rebars, magnetic field magnetization experiments and axial tensile experiments of rebars were conducted. The tangential/normal components of spontaneous magnetic leakage field (SMLF) intensity BT/N were collected. The “SMLF intensity distribution parameters” DT/N were introduced to quantify the degree of stress-induced changes in the distribution of the BN/T curves on the rebar surface. The results show that both the stress state and the initial magnetization state affect the variation pattern of SMLF intensity of rebars, and BT/N have different characteristics of the force-magnetic coupling effect. With the increase of tensile stress, BT curves shift downward and BN curves rotate counterclockwise. With the increase of magnetization, the convexity degree of BT curves and the variation range of BN curves enlarge. And both BT/N values change abruptly at the yield strength point. The initial magnetization state drives the force-magnetic coupling effects in the elastic and plastic stages to exhibit differences. The σ-DT/N curves in the elastic stage are linearly monotonically decreasing, where the σ-DT fitted straight line has a large downward slope. DT is more sensitive to stress changes. The DT/N variations in the plastic stage can effectively characterize the stable development region of plastic deformation. The modified J-A magnetomechanical model reveals the contribution of the initial magnetization state to the characterization of the force-magnetic coupling effect. The morphological analysis of the rebar microstructure clarifies the physical reasons for the SMLF variation under different stress states. This research provides a new idea for the non-destructive detection of the rebar stress state.

Stress and Corrosion Defect Identification in Weak Magnetic Leakage Signals Using Multi-Graph Splitting and Fusion Graph Convolution Networks

Weak magnetic flux leak detection is one of the most important non-destructive testing and measurement methods for pipelines. Since different defects cause different damage, it is necessary to classify the different types of defects. Traditional machine learning methods of defect type identification mainly use feature analysis methods and rely on expert a priori knowledge and the ability of designers. These methods have the following weaknesses: a priori knowledge needs to be designed iteratively, and a priori knowledge design relies on expert experience. In recent years, the rapid development of deep learning methods in the field of machine vision has led to the development of defect analysis in the industry. However, most deep learning methods lack the ability to analyze both detailed information and the overall structure. In this paper, we propose graph convolution networks for splitting and fusing multiple graphs of detail graphs and a root graph. Detail information (detail graphs) provides detailed information for the detection of WMFLs. The structure information (root graph) provides structural information for the detection of WMFLs. This paper uses simulation data and experimental data to verify that the proposed method can identify stress defects and corrosion defects well. The paper explains the experimental results in detail to demonstrate the superiority of the method in industrial methods.

Electromagnetic Field Analysis of Distributed Winding Permanent Magnet Synchronous Motor Considering Axial Leakage Flux using Two-Dimensional Finite-Element Analysis

This paper proposes a method for the electromagnetic field analysis of permanent magnet synchronous motors (PMSMs) considering the axial leakage flux. To the axial leakage flux while employing two-dimensional (2D) finite-element analysis (FEA), the permeance of the axial leakage path is added into a slot region by increasing the permeability of elements in that region. The increased permeability is calculated based on the permeance relationship of the main magnetic and axial leakage paths, which are calculated using the equivalent magnetic circuit method. The effect of the proposed method is verified by comparing it with the 3-dimensional FEA results. The proposed coupling method uses finite element analysis and is developed from the lumped method proposed in our previous research. The developed method enables the analysis of distributed winding machines, which is not possible with the existing method.

Analytical and FEM Methods for Line Start Permanent Magnet Synchronous Motor of 2.2kW

This paper has developed electromagnetic equations based an analytical model to design a three-phase line start permanent magnet synchronous motor (LSPMSM) of 2.2 kW. In order to enhance the torque and efficiency of this machine, an optimized slot shape of rotor permanent magnet is proposed. The analytical model is first presented to evaluate the magnetic characteristics, and then analytical expressions are derived under the open circuit condition. The influence of the magnet size variables on the analytical model is considered to investigate the magnetic leakage flux and flux density distribution in air gaps. Moreover, the variation of design has a significant impact on the steady-state performance characteristics of this motor. In addition, in order to check the output results from the analytical model, a finite element method is developed to evaluate these solutions. Finally, experimental and simulation results have been compared and analyzed to validate the development of method.

Demagnetization Fault Diagnosis of Permanent Magnet Synchronous Motor Based on Empirical Mode Decomposition

The demagnetization failure of the permanent magnet synchronous motor (PMSM) will be accompanied by a magnetic leakage phenomenon. The degree of magnetic leakage will affect the utilization of the permanent magnet. If the magnetic leakage is serious, the motor can not run normally. To study the problem of the demagnetization fault degree of PMSM when partial demagnetization fault occurs, this paper employs the finite element method to simulate the radial magnetic leakage signal 1cm outside the 8-pole 48-slot surface-mounted PMSM. The amplitude of the harmonic wave of the radial magnetic leakage signal is analyzed when partial demagnetization occurs in the permanent magnet synchronous motor. The results show that the spatial order amplitude of the motor radial flux leakage signal decreases along with the increase of demagnetization, which can be used as a check for the demagnetization degree of the motor.