Ferromagnetic Parts Research Articles

Coupled Magnetic Field-Circuit Analysis of Inductive Power Transfer in High-Potential Transformers

Inductive power transfer grew to be a hot topic as reflected by monographs and thousands of articles published mainly last decade. We complement the bulk of research by harnessing the power of coupled magnetic field (MF)-circuit simulations on examples of virtually air-core high-potential (HP) transformers. Easiness of reliable insulation design is greatly facilitated by their open magnetic systems. Circuit analysis on the basis of simplified equivalent circuits is performed. A comparison is made to Tesla transformer. Major impediment here is modeling ferromagnetic parts of the system. Thus, circuit analysis is mostly helpful for a qualitative grasp of the problem. The design is greatly simplified by coupling the MF of the transformer to external circuitry. We do it on a COMSOL platform. Sweeping number of turns, height of the windings, values of resonant capacitors, and so on, we can arrive at an optimal design point. Most of the simulations were done in the frequency domain. Following this procedure, we built and extensively characterized several 20-kV, 1-kW transformers with high-potential insulation sized to 150 kV in a wide range of switching frequencies centered around 50 kHz. A transformer of choice was tested at high voltage (HV) and nominal power in ambient air. The transformer efficiency was >92%, with the largest overheat of 50 °C being on the primary winding.

Spin transfer torque and exchange coupling in Josephson junctions with ferromagnetic superconductor reservoirs

In this paper, the spin transfer torque (STT) and the exchange coupling of the Josephson junctions containing the interesting cases of diffusive/ballistic-triplet/singlet ferromagnetic superconductor (FS) materials are investigated. First, the diffusive FS1/Fc/FS2 structures with Fc being a junction consisting of ferromagnetic and normal metal parts as well as insulating barriers are investigated. Secondly, the ballistic Josephson junction containing the triplet chiral p/wave FS reservoirs is studied. Using the Nazarov quantum circuit theory for the diffusive structures, it is found that the antiparallel/parallel or vice versa parallel/antiparallel transition of the favorable exchange coupling takes place due to the appearance of the only out-of-plane STT. Furthermore, the analyze of the phase difference interval in which an interlayer length-induced antiparallel/parallel transition can be occurred, is performed. Afterward, the mentioned ballistic structure is dealt with solving the 16 16 Bogoliubov–de-Gennes equation. It is found that although the exchange fields of the FS are laid in the z and y direction, the STT interestingly exists in all three directions of x, y and z. This exciting finding suggests that the favorable equilibrium configuration concerning the least exchange coupling occurs in the relative exchange field direction different from 0 or .

Metamagnetic texture in a polar antiferromagnet

The notion of a simple ordered state implies homogeneity. If the order is established by a broken symmetry, elementary Landau theory of phase transitions shows that only one symmetry mode describes this state. Precisely at points of phase coexistence domain states formed of large regions of different phases can be stabilized by long range interactions. In uniaxial antiferromagnets the so-called metamagnetism is an example of such a behavior, when an antiferromagnetic and field-induced spin-polarized paramagnetic/ferromagnetic state co-exist at a jump-like transition in the magnetic phase diagram. Here, combining experiment with theoretical analysis, we show that a different type of mixed state between antiferromagnetism and ferromagnetism can be created in certain acentric materials. In the small-angle neutron scattering experiments we observe a field-driven spin-state in the layered antiferromagnet Ca3Ru2O7, which is modulated on a scale between 8 and 20 nm and has both antiferromagnetic and ferromagnetic parts. We call this state a metamagnetic texture and explain its appearance by the chiral twisting effects of the asymmetric Dzyaloshinskii-Moriya (DM) exchange. The observation can be understood as an extraordinary coexistence, in one thermodynamic state, of spin orders belonging to different symmetries. Experimentally, the complex nature of this metamagnetic state is demonstrated by measurements of anomalies in electronic transport which reflect the spin-polarization in the metamagnetic texture, determination of the magnetic orbital moments, which supports the existence of strong spin-orbit effects, a pre-requisite for the mechanism of twisted magnetic states in this material.

Direct Calculation Method of Fringing Field Reluctance in MEC Analysis for An Axisymmetric Solenoid Actuator

In this paper, a method is introduced to directly calculate the reluctances of fringing fields in analyzing a magnetic equivalent circuit model for an axisymmetric solenoid actuator including radial air gaps as well as axial air gaps. The introduced method was motivated by the possibility to calculate the cross section area depending on the radial position of an infinitesimal element when the infinitesimal element is defined to be integrated in the flux flow direction in a circular-arc straight-line model of an axisymmetric model. In this method, the reluctance of fringing field near an air gap can be calculated directly. For an objective model, the MEC analysis was performed using the introduced method and an iterative method. In the iterative method, the nonlinearity of the ferromagnetic material parts is resolved. In order to validate the introduced method, MEC analysis and FEA results are compared. And for validating the method in a view of computation also, an optimized design satisfying pre-defined constraints was searched using MEC analysis, and then the results of the MEC analysis using the introduced method and FEA results are compared for the searched design and the initial design.

Development of a Hybrid Analytical Model for a Fast Computation of Magnetic Losses and Optimization of Coaxial Magnetic Gears

This paper focuses on a two-dimensional (2-D) analytical model for a fast computation of magnetic losses due to eddy currents in the permanent magnets as well as iron losses in the ferromagnetic parts within coaxial magnetic gears. The magnetic field distribution is computed in yokes and permanent magnets by solving both Maxwell's equations, whereas for pole pieces, the magnetic field is computed by coupling the previous analytical model with a reluctance network model. Both the eddy current losses and iron losses are determined from this hybrid analytical model. The iron loss model takes into account the temporal and spatial variations of flux density. The eddy current loss model takes into account the magnet splitting. Results of this magnetostatic eddy current loss model are then compared to the results obtained with a 2-D magnetodynamic finite element model. A verification of validity limits is also proposed. The final function of this analytical model is to ensure integration into a set of models in the aim of a global mechatronic optimization of magnetic gears, for their insertion into multimegawatt wind turbines. A preliminary bi-objective, mass-efficiency optimization protocol is subsequently proposed along with an analysis of the computation time reduction via the presented models.

Magnetic focusing method and sensor in surface topography testing for ferromagnetic materials

As the precision of the manufacturing process and the quality of ferromagnetic parts are further enhanced, surface topography is playing a significant role in guaranteeing the service performance and lifetime of mechanical parts. Thus, a novel magnetic focusing method (MFM) that is not susceptible to a hostile environment in a sophisticated and online manufacturing process is proposed, which is demonstrated to be an effective and feasible technique with higher detection resolution and a higher signal-to-noise ratio (SNR). By a theoretical introduction of the magnetic focusing mechanism and finite element simulations and calculations for six main MFM sensor structural parameters, the MFM sensor characterizations and optimal structural parameters are presented. Furthermore, the feasibility and validity of the proposed novel method and sensor in surface topography inspection for ferromagnetic materials were verified in the experiments. Finally, the advantages and disadvantages of the common surface topography testing methods were compared. These results demonstrate the great promise in the application of MFM and the corresponding sensor in practical engineering.

Global Quantities Computation Using Mesh-Based Generated Reluctance Networks

Global Quantities Computation Using Mesh-Based Generated Reluctance Networks

Finite Element Analysis Simulation of Switched Reluctance Motor Drive

This paper presents a simulation by finite element analysis of the switched reluctance motor, using a half bridge asymmetric converter, in order to verify the flux densities in the ferromagnetic parts of the motor to avoid a high level of saturation. The results obtained from the simulation shows that the motor operates under the saturation point of the stator as well as the rotor materials.

Magnetic disturbance field compensation of a geomagnetic vector measuring instrument

Magnetic disturbance field from ferromagnetic structural parts is a dominant factor that influences the accuracy of a geomagnetic vector measuring instrument. In this paper, a new vector compensation method for a three‐axis magnetometer is proposed. In the first step, combined with posture information from inertial sensors, the dataset of the three‐axis magnetometer outputs in different postures is utilized to construct linear equations of the error parameters; then the soft‐iron parameters are determined with singular value decomposition. In the second step, the hard‐iron parameters are estimated by changing the fixing direction of the three‐axis magnetometer. Simulations and experiments are performed to assess the performance of the proposed method. The results show that the error parameters can be accurately estimated, and the measurement errors of geomagnetic field vectors and magnitude are suppressed greatly. After compensation, the standard deviations of the errors of the magnetic vector components decrease from hundreds of nT to tens of nT. The main advantages of this proposed method are as follows: (i) it can compensate not only the scalar error but also the vector error, and (ii) it compensates the errors of vectors and magnitude with higher accuracy. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Nonlinear three-port magnetic-circuit elements for simulating bending magnets

PurposeThe purpose of this paper is to show that constructing magnetic equivalent circuits (MECs) for simulating accelerator magnets is possible by defining a three-port magnetic element for modelling the T-shape field distribution, where the flux leaves the yoke and enters the aperture.Design/methodology/approachA linear three-port magnetic element is extracted from an analytical field solution and can be represented by a number of two-port elements. Its nonlinear counterpart is obtained as a combination of the corresponding nonlinear two-port elements. An improved nonlinear three-port element is developed on the basis of an embedded nonlinear one-dimensional finite element model.FindingsThe T-shaped field distribution comes together with a complicated interplay between the saturation of the ferromagnetic yoke parts and flux leaking to the aperture. This is more accurately modelled by the improved nonlinear three-port magnetic element.Research limitations/implicationsMECs have a limited validity range, especially for configurations where a high saturation level and fringing flux effects coexist.Practical implicationsThe results of the paper appeal to be careful with applying nonlinear MECs for simulating bending magnets.Originality/valueA new nonlinear three-port magnetic element for ferromagnetic yoke parts with T-shaped flux distribution has been developed.

Superconductivity, ferromagnetism, and antiferromagnetism in the Hubbard model

Using the simplest one-loop approximation, it is possible to observe both ferromagnetic and antiferromagnetic nonoverlapping parts of the phase diagram, each of which overlaps with the domain of existence of the superconducting ordering.

A model to predict the ultrasonic field radiated by magnetostrictive effects induced by EMAT in ferromagnetic parts

An Electro-Magnetic Acoustic Transducer (EMAT) is a non-contact source used in Ultrasonic Testing (UT) which generates three types of dynamic excitations into a ferromagnetic part: Lorentz force, magnetisation force, and magnetostrictive effect. This latter excitation is a strain resulting from a magnetoelastic interaction between the external magnetic field and the mechanical part. Here, a tensor model is developed to transform this effect into an equivalent body force. It assumes weak magnetoelastic coupling and a dynamic magnetic field much smaller than the static one. This approach rigorously formulates the longitudinal Joule’s magnetostriction, and makes it possible to deal with arbitrary material geometries and EMAT configurations. Transduction processes induced by an EMAT in ferromagnetic media are then modelled as equivalent body forces. But many models developed for efficiently predicting ultrasonic field radiation in solids assume source terms given as surface distributions of stress. To use these models, a mathematical method able to accurately transform these body forces into equivalent surface stresses has been developed. By combining these formalisms, the magnetostrictive strain is transformed into equivalent surface stresses, and the ultrasonic field radiated by magnetostrictive effects induced by an EMAT can be both accurately and efficiently predicted. Numerical examples are given for illustration.

Compensation of Geomagnetic Vector Measurement System With Differential Magnetic Field Method

The accurate measurement of a geomagnetic field is a key technology in many applications, such as magnetic anomaly detection, underwater geomagnetic navigation, and motion tracking. However, the magnetic interference fields, such as ferromagnetic parts and other electric equipments, will seriously influence the measurement accuracy of geomagnetic vector measurement system, and thus should be compensated. In this paper, a new compensation method using differential magnetic field is proposed. As a first step, a permanent magnet with different relative positions is used to change the ambient magnetic field to construct the error model equations about unknown quantities, and the soft-iron error parameters can be estimated by solving equations with nonlinear least square method. Then, the hard-iron error parameters can be estimated by changing the fixation direction of the three-axis magnetometer. Finally, the estimated error parameters are used for compensating the magnetic interference field. In order to verify effectiveness of the proposed method, simulation and experiment are performed, and the results demonstrate that the proposed method estimates error parameters accurately and improves the measurement accuracy of geomagnetic vector measurement system greatly.

A new method for distortion magnetic field compensation of a geomagnetic vector measurement system

The geomagnetic vector measurement system mainly consists of three-axis magnetometer and an INS (inertial navigation system), which have many ferromagnetic parts on them. The magnetometer is always distorted by ferromagnetic parts and other electric equipments such as INS and power circuit module within the system, which can lead to geomagnetic vector measurement error of thousands of nT. Thus, the geomagnetic vector measurement system has to be compensated in order to guarantee the measurement accuracy. In this paper, a new distortion magnetic field compensation method is proposed, in which a permanent magnet with different relative positions is used to change the ambient magnetic field to construct equations of the error model parameters, and the parameters can be accurately estimated by solving linear equations. In order to verify effectiveness of the proposed method, the experiment is conducted, and the results demonstrate that, after compensation, the components errors of measured geomagnetic field are reduced significantly. It demonstrates that the proposed method can effectively improve the accuracy of the geomagnetic vector measurement system.

Friction Coefficient and Worn Surface of Ferromagnetic Materials under Magnetic Fields

Several machine components including a part of electrical circuit box, an electrical motor and an automotive part were common ferromagnetic materials used under the magnetic fields. In the general, their friction had occurred in the magnetized materials during operation. The friction coefficient of the sample under magnetic fields was different from the sample without magnetic field treatment. Its friction coefficient had correlation with wear behavior of specimens. The wear protection procedures for the ferromagnetic parts during operation are recognized different from others without magnetization. Its friction coefficient was thus used to measure the wear characteristics with a ball on disc friction tester. The microstructure of wear trace and debris was investigated by scanning electron microscope. From the results, the magnetic fields affected the change of friction coefficient. The friction coefficient was decreased with an increasing magnetic intensity. This was because the wear debris was induced and thus decreased the adhesive wear mode during friction test.

Calibration of Hall sensor array for critical current measurement of YBCO tape with ferromagnetic substrate

HAS (Hall sensor array) is a powerful tool to detect the uniformity of HTS (high temperature superconductor) tape through mapping the distribution of remanent or shielding field along the surface of the tape. However, measurement of HTS tape with ferromagnetic parts by HSA is still an issue because the ferromagnetic substrate has influence on the magnetic field around the HTS layer. In this work, a continuous HSA system has been designed to measure the critical current of the YBCO tape with ferromagnetic substrate. The relationship between the remanent field and critical current was calibrated by the finite element method. The result showed that the HSA is an effective method for evaluating the critical current of the HTS tape with ferromagnetic substrate.

A Study on the Relationship between Hardness and Magnetic Properties of Ultra-High Strength Steel

Magnetic nondestructive testing methods including eddy current testing, magnetic memory, magnetic Barkhausen noise and so on are widely used in testing mechanical properties of ferromagnetic parts. Experiments were done to study the relationship between hardness and magnetic properties of ultra-high strength steel (UHSS), which plays an important role in automobile industry. The magnetic properties of UHSS specimens with different hardness were studied. The result shows that there is a strong connection between hardness and magnetic properties. Coercive force of UHSS is proportional to the hardness. This can be used to explain certain mechanism of magnetic nondestructive testing method such as connection between hardness and Barkhausen noise.

FeNi-based flat magnetoimpedance nanostructures with open magnetic flux: New topological approaches

Classic flat MI multilayers consist of top and bottom ferromagnetic parts of equal thickness separated by a conductive lead. In previous studies symmetric MI structures were considered because they provide the highest sensitivity with respect to uniform external magnetic fields. There are a number of applications where non-uniform magnetic fields of complex configurations must be detected. Non-symmetric MI structures can be advantageous in this particular case. We describe our experience in design, fabrication and characterization of symmetric and non-symmetric MI multilayers with open magnetic flux. Non-symmetry of the structures was obtained by the deposition of top and bottom ferromagnetic parts of MI element of different thickness. MI responses of the structures with even or odd configurations of the FeNi layers were also considered.

Dynamic Preisach model identification applying FEM and measured BH curve

Purpose – The purpose of this paper is to develop a viscous-type frequency dependent scalar Preisach hysteresis model and to identify the model using measured data and nonlinear numerical field analysis. The hysteresis model must be fast and well applicable in electromagnetic field simulations. Design/methodology/approach – Iron parts of electrical machines are made of non-oriented isotropic ferromagnetic materials. The finite element method (FEM) is usually applied in the numerical field analysis and design of this equipment. The scalar Preisach hysteresis model has been implemented for the simulation of static and dynamic magnetic effects inside the ferromagnetic parts of different electrical equipment. Findings – The comparison between measured and simulated data using a toroidal core shows a good agreement. A modified nonlinear version of TEAM Problem No. 30.a is also shown to test the hysteresis model in the FEM procedure. Originality/value – The dynamic model is an extension of the static one; an extra magnetic field intensity term is added to the output of the static inverse model. This is a viscosity-type dynamic model. The fixed-point method with stable scheme has been realized to take frequency dependent anomalous losses into account in FEM. This scheme can be used efficiently in the frame of any potential formulations of Maxwell's equations.

An investigation of a two–pole rotating magnetic field with no secondary medium present using the finite element method

The field of a two–pole magnetic system, consisting of an AC electric machine stator with no secondary medium present, was computed using the finite–element method. The influence of the slot wedge value and that of the nonlinearity of the ferromagnetic parts on the field inhomogeneity and on the magnetic flux were determined. The application of an approximative expression for the flux density is specified.