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The quantitative analysis of the iron loss taking magnetic hysteresis behavior into account is essential for the development of high-efficiency electric machines. In a previous paper, a novel magnetic circuit model incorporating a play model, which is one of the phenomenological models of magnetic hysteresis, was proposed. It was clear that the proposed model can calculate the hysteresis loop of a ring core with high speed and high accuracy. However, this method was applied only for the objects with simple shapes. Thus, it is necessary to extend the applicable range for the objects with more complicated shapes. This paper presents a novel reluctance network analysis (RNA) model incorporating the play model and indicates the validity of the proposed RNA model by using a three-phase-laminated-core variable inductor as an object of discussion. [ABSTRACT FROM AUTHOR]

In this paper, we study the isotropic properties of a ring-shaped magnetoelectric composites made of Terfenol-D and PZT-5H. We presented a theoretical model to estimate the output via areal strain considering the effect of magnetic hysteresis. Test samples were prepared by stacking and bonding together both the ring-shaped magnetostrictive material, Terfenol-D, and the piezoelectric material, PZT-5H. The results show that the magnetoelectric composites have an ac resonant frequency $f_{\mathrm {ac}}$ of about 32 kHz. When the dc bias magnetic field $H_{\mathbf {dc}} = 280$ Oe and $f_{\mathrm {ac}} = 32$ kHz, the linear fit of the relation between the output and the ac magnetic field provides a high coefficient of determination (R-square = 0.95), and the magnetoelectric voltage coefficient is 4.28 V/ $\text {cm}\cdot \text {Oe}$. These values indicate a good linear relationship, thus confirming that the composites present the basic performance of a magnetic sensor. The isotropic properties of the sample were fitted with the curve obtained from the theory. The results show that the isotropic ratio is theoretically equal to 7:1 at a resonant frequency of 32 kHz, which keeps highly consistent with test data. The coefficient of determination (R-square = 0.94) between the test data and calculated values confirms the goodness of the fit, thus indicating the correctness and reliability of the theoretical model. The model presented in this paper provides a theoretical basis to analyze and improve the isotropic properties of magnetoelectric sensors. [ABSTRACT FROM AUTHOR]

Through numerical simulations and calibrated experiments, the aim of the work presented in this paper is placed on the development of a polarity changeable magnetizing platform for a rotary magnetic encoder using a permanent magnet and thin silicon steel plate. Parameter studies are conducted via finite-element analyses to obtain optimized geometric design parameters for the magnetizer, leading to desirable magnetic flux density and effective magnetized patterns on the magnetic media. [ABSTRACT FROM AUTHOR]

Accurate and simple magnetic material behavior law is necessary to correctly model complete electromagnetic systems. In this paper, a new formulation based on the scalar quasi-static hysteresis Preisach model extended to dynamic behavior using fractional derivation dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to correctly obtain simulation results on a very large frequency bandwidth. By using such formulation, space discretization techniques (finite differences, finite elements) are avoided which are highly space and time consuming while keeping the global simulation results precise. The numerical implementation of the problem and some experimental validations are shown in this paper. [ABSTRACT FROM AUTHOR]

We propose a new high performance magnetometer using a single magneto-impedance (MI) sensor with a peak-to-peak voltage detector by synchronized switching (shortened: Pk-pk VD-type MI magnetometer), which is aimed to measure an extremely weak magnetic field ranging from nT ( 10^-9 T) to pT ( 10^-12 T), based upon the conventional MI magnetometer, which is used in the electronic compass. In order to enhance sensitivity and reduce noise, the Pk-pk VD-type MI magnetometer detects both the positive peak and the negative peak in induced voltage waveform of pickup coil. In this paper, for demonstrating the performances of the Pk-pk VD-type MI magnetometer, we investigate the magnetic field sensitivity and the magnetic noise spectral density. We demonstrated that the noise level of the Pk-pk VD-type MI magnetometer is lower than 2 pT/Hz ^1/2 for the frequency range from 1 to 100 Hz, which is much better than the conventional MI magnetometer. We discuss the noise performance of the Pk-pk VD-type MI magnetometer. According to the results obtained in this paper, we expect that this proposed MI magnetometer can be widely used for extremely weak magnetic field detection. [ABSTRACT FROM AUTHOR]

The field calculus for electrical machines (EMs) is realized solving subdomain problems. Most often, the latter are solved using either finite element analysis (FEA) or the semi-analytical solution of a Laplace or Poisson equation obtained by separation of variables. The first option can capture complex geometries but becomes slow for high accuracy, whereas the second is fast but limited to simple periodic geometries and linear or infinite permeable materials. This paper presents the 2-D implementation of the spectral element method (SEM) for the modeling of EMs. The polynomial basis functions used to approximate the solution in each domain are reaching exponential convergence similar to the semi-analytical solution. Moreover, each element can be represented by a non-square shape resulting in the possibility to model complex geometries. Following the results in this paper, significantly fewer degrees of freedom are needed for the SEM to achieve the approximation similar to the FEA, and consequently less memory and computational time are required. [ABSTRACT FROM AUTHOR]

This paper presents an engineering modeling methodology for magnetostrictive materials based on a simplified piezo-electric governing equation. For verifying the modeling performance, a proof-of-concept non-contact strain sensor utilizing a prototype magnetostrictive (Fe–Ga alloy, Galfenol) strip on a steel plate is used to evaluate sensor performance prediction. Typically, the performance of Galfenol is measured in a compressional load region because it has a higher response. However, in this paper, we are aiming to develop a sensor for tensile stress measurement. To achieve a compression effect from a tension load in the sensing element, a Galfenol strip is aligned perpendicular to a tension bar so that tension in the bar creates compression in the strip via the Poisson effect. The experimental setup in this paper consists of a polycrystalline Galfenol strip bonded in the horizontal direction of a steel dog-bone shaped tension specimen. Permanent magnets are attached at each end of the Galfenol strip to provide an even magnetic bias field through the strip. The magnetic flux through the Galfenol strip is measured with non-contact Hall sensors during the tensile load test. The simulation results agree well with the experiments for the value of $H$ studied. [ABSTRACT FROM AUTHOR]

In this paper, the influences of design parameters on the on-load demagnetization behavior of a switched flux hybrid magnet memory machine (SF-HMMM) are evaluated, which aims to provide a useful design guideline to avoid this performance degradation. The machine topology and on-load demagnetization phenomenon are described, respectively. Furthermore, some key design parameters are selected to optimize to elevate the operating point of the low coercive force (LCF) permanent magnets (PMs). Then, some geometric modifications are suggested to alleviate the on-load demagnetization effects. Finally, an SF-HMMM prototype is fabricated and tested to experimentally verify the finite-element analysis. [ABSTRACT FROM AUTHOR]

Extensive research and experiments have shown that rotational core loss, which usually exists in the corner joints of multi-phase transformers and behind the teeth of rotational motors, may amount to more than 50% of the total core loss. The frequency of rotational magnetic field can reach even kilohertz level in high-speed motors. In this paper, a new magnetizer of double-yoke vertical structure made of ultrathin steel sheet (0.05 mm) and the corresponding $B$ – $H$ sensing structure are proposed and constructed. Both the alternating and 2-D rotational magnetic properties for non-oriented steel B35A210 and grain-oriented steel B27R090 are measured and characterized up to kilohertz. The magnetic anisotropy of silicon steel is observed and analyzed from its origin mechanism. Moreover, the alternating, 2-D circular and elliptical rotational core losses are compared and discussed. This paper can provide a reference for core loss modeling and the calculation of electrical machines or transformers under different magnetization conditions. [ABSTRACT FROM AUTHOR]

The utilization of a bismuth-substituted iron garnet as a magnetooptic Faraday rotator (MOFR) has been reported for all-optical networking purposes as well as for other applications. Our measurements and observations demonstrate that the MOFR saturates once a significantly large magnetic field (>225 G) is applied. After the applied magnetic field enters the saturation region, the material’s magnetic domains can become pinned at intermediate levels of magnetization. Pinning in this form has not been reported nor well studied for this application. In this paper, a method to detect and describe anomalous pinning in terms of Faraday rotation is presented. Measurements on the changes in the state of polarization that a pinned material produces are examined. This paper will also present practical methods for unpinning the MOFR material, which are traditionally considered to be challenging. [ABSTRACT FROM AUTHOR]

In this paper, we propose a loss calculation method considering minor hysteresis loops for permanent magnet (PM) motors driven by pulsewidth modulated (PWM) inverters. In the governing equation of the proposed method, both the effects of the major and minor hysteresis phenomena are expressed by a reaction magnetic field. This field is determined by iterative calculations of finite-element analysis (FEA) with a simple hysteresis modeling that considers the minor loops. The proposed method is applied to a PM motor, and the experimental verification is carried out. It is clarified that the minor hysteresis loops affect not only the hysteresis loss but also the eddy current loss because the skin depth varies with the differential permeability of the minor loops. [ABSTRACT FROM AUTHOR]

This paper presents an identification algorithm of the scalar Preisach model by using a set of symmetric minor hysteresis loops and suggests an improved vector Preisach model to describe the vector and anisotropic hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under rotating magnetic fields. Symmetric minor hysteresis loop is quite easy measured, so an identification algorithm based on symmetric minor hysteresis loop instead of first-order reverse curve is presented in this paper. The vector Preisach model employs a nonlinear coefficient, which is a function of magnitude and a direction of magnetic flux density, to describe the anisotropic property of the NO ESS and increases the numerical accuracy. The validity of the suggested vector Preisach model is investigated through comparisons with the experimental results under various magnetic field conditions. [ABSTRACT FROM AUTHOR]

Accurate modeling of three-phase asymmetric (three- and five-limb) transformers is still a challenge. In this paper, a method for the calculation of the major hysteresis loop for three-phase asymmetric transformers is proposed. All necessary information can be obtained from measurements taken at the transformer terminals without breaking the connections and using only standard tests. For illustration and validation, the method is applied to Wye–wye and Wye–delta connections for three-limb and five-limb transformers, but the method is applicable to all transformer connections. The obtained hysteresis loops are implemented in three-phase dual-reversible models. Simulation results are validated with laboratory experiments. The excellent agreement between simulations and measurements gives great confidence that the method is practical for engineering work. [ABSTRACT FROM AUTHOR]

A coaxial magnetic gear (CMG) consisting of an inner ring, outer ring, and flux modulator exhibits relatively large torque density at low operating cost and low noise level. To guide the selection of soft magnetic materials for the flux modulator, this paper first incorporates the Jiles–Atherton model within a finite-element (FE) framework. The influence of nonlinear magnetic properties on end-effect losses (magnetic flux leakage and fringing) is then investigated with the objective of maximizing the pullout torque. For flux modulators whose initial magnetic permeability and saturation flux density exceed certain threshold value, the pullout torque of a CMG becomes insensitive to magnetic properties and end-effect losses can be efficiently calculated from a 2-D FE model together with a constant torque reduction ratio. This paper presents a systematic torque surface method that can decouple the analysis of average torque and torque ripples. This method has been implemented to evaluate load dependence and rotation speed fluctuation of a CMG. [ABSTRACT FROM AUTHOR]

Non-oriented (NO) electrical steels are widely used as core materials in rotating electrical machines, whereas for measurements under alternating magnetization (AM), standardized methods exist; measurements under rotational magnetization (RM) prove to represent a significant problem. In this paper, we performed measurements of both circular rotational and alternating losses in rolling and transverse directions for four types of NO materials of different Si contents and thicknesses by means of a hexagonal rotational single-sheet tester at different frequencies and flux density values. The losses were measured by the electrodynamical method and for confirmation also by the thermal (rise-of-temperature) method. The estimated rotational losses by means of established well-known methods are correlated with the measured ones. Literature reports attempt to estimate losses $P^{\mathrm {(RM)}}$ for circular RM on the basis of losses $P^{\mathrm {(AM)}}$ for AM. A loss ratio factor $\Gamma = P^{\mathrm {(RM)}}/P^{\mathrm {(AM)}}$ is defined which is reported to be close to $\Gamma = 2$. In this paper, $\Gamma $ factors were determined for three different grades of material. The results indicate a rather weak dependence of $\Gamma $ on the grade, however, a strong one on the intensity $B$ of induction. In approximation, $\Gamma = 2$ is valid for rather weak induction of the order $B = 0.6$ T. Induction increases in steps of $\Delta B = 0.1$ T yield decreases of loss ratio by about $\Delta \Gamma = 3$ %. This enables a rough estimation of rotational losses. However, the possibility of estimation is restricted to the circular case of constant modulus and angular velocity of the $B$ vector. Other cases are characterized by different values of both eddy current losses and hysteresis losses, RM involving completely different domain reconstructions compared to AM. For increased frequency, the decrease in $\Gamma $ becomes weaker due to more dominant eddy current losses. [ABSTRACT FROM AUTHOR]

Accurate modeling of soft- and hard-magnetic materials for the numerical simulation of rotating electrical machines is required to allow predictions on the operational characteristics along the torque–speed map, already in the design stage. The full potential of most appropriate material selection and concurrent geometry adaption can only be utilized if models can represent actual material behavior. The accurate prediction of iron losses of soft-magnetic materials for various frequencies and magnetic flux densities, as well as the degradation due to manufacturing is eminent for the design of electrical machines. Therefore, advanced material models need to be adapted and their accuracy examined to further improve the modeling and enable progression. This paper will give an overview of the current modeling approaches applied at the Institute of Electrical Machines for soft- and hard-magnetic materials in the simulation of rotating electrical machines. A case example in the form of a traction drive is presented to which the models are applied. For the machine modeling, the inhouse solver pyMOOSE is utilized. In order to determine the losses with regard to manufacturing processes, the iron-loss model with material degradation is used in combination with a machine simulation scheme of the entire operating range of the machine. Here, various simulation approaches are combined to form the entire computational toolchain to obtain accurate results in the entire operational range. [ABSTRACT FROM AUTHOR]

In this paper, the iron loss models for electrical machines are first reviewed. One of the most accurate iron loss models, when the temperature is constant, is identified. An improved temperature-dependent iron loss model is also introduced. By applying the improved iron loss model to the electrical machine thermal analysis, the thermal and loss analyses can be fully coupled. Based on this, an improved thermal-loss coupling analysis method for electrical machine is developed in this paper. The electrical machine iron loss tests are carried out. The analysis and measurement results are then compared in order to validate the improved thermal-loss coupling analysis method. The comparison results indicate that the temperature prediction accuracy can be significantly improved by using the improved thermal-loss coupling analysis method. [ABSTRACT FROM AUTHOR]

This paper presents a detailed theoretical background of the saturation wave model (SWM), which offers a simplified homogenized solution of the nonlinear diffusion phenomena inside soft magnetic steel sheets (SMSSs). The SWM is capable of predicting the complicated dynamic magnetization of SMSS without discretization of the cross section of the SMSSs. Despite its simplicity, the SWM predicts exact solutions of the discussed problems when step-like magnetization curves are assumed and reasonably accurate solutions for real magnetization curves. In this paper, the SWM is analyzed in comparison to the numerical solution of the diffusion phenomena using the parametric magnetodynamic model, where interesting properties of the SWM are discussed and pointed out. [ABSTRACT FROM PUBLISHER]

Arrays of nanosized hollow spheres of Ni were studied using micromagnetic simulation by the Object Oriented Micromagnetic Framework. Before all the results, we will present an analysis of the properties for an individual hollow sphere in order to separate the real effects due to the array. The results in this paper are divided into three parts in order to analyze the magnetic behaviors in the static and dynamic regimes. The first part presents calculations for the magnetic field applied parallel to the plane of the array; specifically, we present the magnetization for equilibrium configurations. The obtained magnetization curves show that decreasing the thickness of the shell decreases the coercive field and it is difficult to obtain magnetic saturation. The values of the coercive field obtained in our work are of the same order as reported in experimental studies in the literature. The magnetic response in our study is dominated by the shape effects and we obtained high values for the reduced remanence, Mr/MS = 0.8 . In the second part of this paper, we have changed the orientation of the magnetic field and calculated hysteresis curves to study the angular dependence of the coercive field and remanence. In thin shells, we have observed how the moments are oriented tangentially to the spherical surface. For the inversion of the magnetic moments we have observed the formation of vortex and onion modes. In the third part of this paper, we present an analysis for the process of magnetization reversal in the dynamic regime. The analysis showed that inversion occurs in the nonhomogeneous configuration. We could see that self-demagnetizing effects are predominant in the magnetic properties of the array. We could also observe that there are two contributions: one due to the shell as an independent object and the other due to the effects of the array. [ABSTRACT FROM PUBLISHER]

The ongoing miniaturization trend of electric machines increases the demand for higher rotational speeds to provide a required power level at decreased size. In this paper, new concepts for bearingless machines with ultra-high rotational speeds exceeding 25 million rotations per minute are researched. While the mechanical properties of the employed sub-millimeter-sized spherical steel rotors are documented, insufficient information is available on the electromagnetic characteristics that are crucial for magnetic levitation and acceleration. This paper outlines the relations between the relative permeability and conductivity of the rotor material and the achievable active magnetic bearing force and angular acceleration. Measured results for complete hysteresis curves of different rotor steels are presented. [ABSTRACT FROM PUBLISHER]

This paper presents the magnetic and electrical equivalent circuits of a hysteresis interior permanent magnet (IPM) motor. A hysteresis IPM motor is a solid rotor hybrid synchronous motor combining hysteresis phenomena and permanent excitation in the rotor. When installed in thousands of feet under the sea to drive an electric submersible pump (ESP), it can self-start the ESP without the need of any position sensors, and can improve the efficiency, the performance, and the reliability of the ESP. In this paper, equivalent circuit models are used to predict the transient run-up responses of a 2.5 kW prototype hysteresis IPM motor. Analysis results are compared with 2-D finite-element analysis (FEA) results as well as experimental results. There exists a reasonably close agreement between analytical, FEA, and experimental results, which validates the accuracy of the equivalent circuit models of a hysteresis IPM motor. [ABSTRACT FROM PUBLISHER]

In this paper, optimization of the control of an electrical machine allowing a minimization of its total losses is described. It is based on the use of an iron loss model [loss surface (LS) model] coupled to the electromagnetic finite-element simulations of the machine. The LS model is a scalar and dynamic hysteresis model developed many years ago at G2Elab and tested for iron loss prediction in several cases of electric machines. It is first characterized and improved in this paper for M330-35A SiFe sheets. Then, it is associated with a finite-element analysis to compute, in a post-processor mode, the local and global magnetic losses in the machine. For electric vehicle application, the whole torque–speed variation should be investigated. To do that, a quick response surface is constructed from a small number of simulations and the iron loss is determined. Then, a suitable optimization algorithm is developed. This approach is then illustrated by a case study and compared with classical optimization in which only the copper losses in conductors are considered. Gains of up to 50% reduction in the total losses of the machine in certain operating areas are observed. [ABSTRACT FROM AUTHOR]

In previous studies on precise computation methods of iron loss, it has been shown that the 1-D dynamic magnetic field analysis with hysteresis in post-processing is effective. However, there is a problem in that the hysteresis makes the convergence of nonlinear iterations unstable. This paper proposes a stabilization method for the 1-D dynamic magnetic field analysis with hysteresis. The proposed method is characterized as an approach for improving the initial value and the step size in the Newton–Raphson method. The results of this paper showed that the convergence characteristic of the nonlinear 1-D magnetic field analysis for variety flux density waveforms of each part in an electric motor is improved using the proposed method. [ABSTRACT FROM AUTHOR]

Recently, the demagnetization has been actively researched to reduce the magnetic field of a warship according to the development of the magnetic detection technology of the magnetic mines. In these studies, it was assumed that the warship was composed of one magnetic material in order to establish an effective deperming protocol. However, since the actual warship was composed of various materials, the magnetic interaction between the materials inevitably occurs during the demagnetization process. Due to the interaction, demagnetization may not be performed well. Therefore, in this paper, the effects of interactions in demagnetization of multiple materials were studied by using the Preisach model, and the optimal protocol was proposed. [ABSTRACT FROM AUTHOR]

In this paper, the dc biasing magnetomotive force (mmf) in presaturated core fault current limiter (PCFCL) is replaced with permanent magnet (PM) to overcome the well-known drawbacks of the dc biased PCFCLs. These drawbacks are excessively induced voltage across the terminals of the dc coil during fault condition and high total power losses during the steady-state condition. The novel contributions of this paper are the introduction of the selection criteria of PM material and its representation by actual nonlinear $B$ – $H$ hysteresis loop of Jiles-Atherton method, and the use of PM alone as an equivalent to the dc biasing coils for three-phase fault current limiter (FCL), contrary to work reported in earlier papers. Single- and three-phase PCFCLs are modified by replacement of dc saturation coil by the equivalent PM through time-domain finite element (FE) simulation of COMSOL Multiphysics package. Experimental verification shows that the implementation of accurate nonlinear representation of PM demagnetization curve with FE simulation gives a realistic performance of the PM biased PCFCL, especially in the fault condition. The performance of PCFCL can be evaluated through the voltage drop and total power losses during the steady-state condition and the fault current clipping ratio during fault condition of the grid. Furthermore, a comparative investigation of dynamic behavior is considered between dc and PM biased PCFCLs. It is found that the PM biased PCFCL has enriched capability of limiting any type of fault current with leading advantages of reduced voltage drop and power losses significantly together with risk elimination of the high induced voltage across dc coil terminals. Moreover, the governing parameters of PM biased PCFCLs are subjected to performance analysis to study their inherent effects. [ABSTRACT FROM AUTHOR]

In this paper, we propose an approach to the design of a magnetostrictive electric power generator for energy harvesting from traffic, and we validate it experimentally. We use the dynamic Preisach hysteresis model (DPM) for magnetostrictive materials, operating in hysteretic and time-varying nonlinear regimes to design and simulate a magnetostrictive electrical power generator. The DPM is a development of the classical Preisach model, which is able to include the dynamical features in the mathematical model of hysteresis. We measure the output power capability of the generator, and we show how it is comparable to other energy-harvesting technologies. [ABSTRACT FROM AUTHOR]

In the fabrication of linear magnetic tunnel junction (MTJ) sensors, the utilization of magnetic bias field along the easy-axis direction makes the response of MTJ nonlinear, and the Néel and magnetostatic coupling usually induces a strong interlayer coupling field along the hard-axis direction. In this paper, we investigated the influence of hard-axis and easy-axis bias fields on the linearity of MTJ magnetic sensor. The prediction and optimization of linearity were done by applying an appropriate hard-axis bias field in the specific easy-axis bias field and the practical tunnel magneto-resistance (TMR) ratio, and the model was verified by experiments. This paper can give guidance to improve the linearity and to maximize the practical TMR ratio of the MTJ sensors under a given linearity requirement. [ABSTRACT FROM AUTHOR]

This paper proposed a temperature-dependent iron loss model and corresponding dynamic hysteresis model, where temperature coefficient k is introduced to consider the thermal effect on eddy-current loss. The iron loss model is validated by massive experimental measurement of test samples, 1174 combinations of various temperatures, magnetic inductions, and frequencies for nonoriented silicon steel specimen. The relative error of the model is $\sim 11$ % in a wide range of 50–400 Hz, 26 °C–200 °C, and 0–2 T. The proposed method can be applicable to other types of magnetic materials as long as whose resistivity rate exhibits approximately linear thermal dependence within a temperature range of 26 °C–200 °C. [ABSTRACT FROM AUTHOR]

This paper discusses fundamental physical mechanisms that are responsible for specific errors of standardized methods of magnetic loss measurements on laminated soft magnetic materials. It is shown that the Poyntings theorem offers an exact distinction between localized loss portions on the one hand and total losses on the other hand. Further, a clear distinction is suggested between mechanisms of hysteresis and eddy currents. The correct applicability of experimental measurements proves to be restricted to cases where the Poynting vector is restricted to normal off-plane components. This represents the only case where total losses can be determined on the basis of surface field and cross-sectional averaged induction. As a consequence, physically “correct” loss measurements are to be restricted to sample regions that exhibit mere axial magnetization, in exact ways. This is attainable with a single sheet tester, the homogeneously magnetized region of which is equipped with an induction coil and a large-area tangential field coil, in consistent ways. [ABSTRACT FROM AUTHOR]

This paper presents the methodology and computation results for the torque and iron losses in a bearingless synchronous reluctance machine. The aim is to compute the hysteresis torque related to the asynchronous operation of the machine under the effect of the levitation field rotating at twice the synchronous speed. For this purpose, and because it is impossible to compute the hysteresis torque with a single-valued B–H characteristic, a magneto-dynamic vector hysteresis model is used. The computations show that the hysteresis-related shaft power is considerable under no-load operation of the machine. It is also shown that the asynchronous torque can be approximated by the classical equivalent circuit of an induction machine. [ABSTRACT FROM AUTHOR]

Rare-earth permanent magnets (REPMs) are central to the electromagnetic energy conversion process in permanent-magnet synchronous and flux-switching machines. To design the magnetic circuit and a magnetizing circuit for post-assembly magnetization, it is indispensable to describe the magnetization behavior of the REPMs accurately. Commonly, simplified models are used that are often not capable to replicate the non-linearity, magnetic hysteresis, and magnetic anisotropy. In this paper, four different REPMs are methodologically characterized by using a pulsed-field magnetometer. Their first-order return curves and magnetization behavior, starting from the virgin state, are recorded and used to parameterize and validate two different pragmatic hysteresis models. [ABSTRACT FROM AUTHOR]

This paper introduces a comparative study of two different hysteresis models, limiting loop model and elemental operator model. The former is regarded as a mathematical approach based on the traditional Preisach model. To circumvent the difficulty of determining the distribution function in the Preisach model, the data of the limiting hysteresis loop and a function transform on the Preisach diagram are employed. The latter is a physical method which adopts a vectorial elemental operator with biaxial anisotropy based on the magnetization mechanisms of the ferromagnetic material. These two models are analyzed and compared in terms of the underlying principle, numerical implementation, and calculation accuracy in this paper. To verify the introduced models, the magnetic properties of non-oriented silicon steel Lycore-140 and soft magnetic composite material Somaloy 500 under alternating excitations are measured and compared with simulated results, which show the validity and practicability of the models but with different calculation accuracy and speed. [ABSTRACT FROM AUTHOR]

This paper presents integrated inductors with Co-Zr-Ta-B (CZTB) thin films on flexible organic substrates for MHz–GHz applications. This paper demonstrated the fabrication and characterization of magnetic thin-film inductors on flexible organic substrates, such as polyimide and Ajinomoto build-up film thin films. These films have thicknesses of only tens of micrometer and thus are very flexible compared to the same inductor structures fabricated on rigid substrates, such as quartz. The magnetic films on flexible substrates were observed to maintain similar magnetic properties compared with those on Si substrate, but with greater coercivity likely due to the increased roughness of the substrate surface. The fabricated thin-film inductors on organic substrates with inductance $L$ , measured by RF characteristics, have shown significantly increased inductance compared to air-core inductors (without magnetic core materials). This paper also demonstrated a high frequency response, clearly over GHz, consistent with the CZTB type of materials. The frequency response, as well as inductance and Q values, remains similar even after many iterations of bending to a large degree, indicating the robustness of the inductor on flexible organic substrates, as well as that of the magnetic thin films. [ABSTRACT FROM AUTHOR]

Energy harvesting allows the conversion of environmental energy into electrical energy to feed low-power consumption electronics. In particular, this method can be exploited to supply wireless sensors nodes for structural health monitoring (SHM) when the electric network source is not present. Indeed, vibrations induced by vehicle traffic on a bridge could be converted into electrical energy, but suitable devices are needed. This paper presents experimental tests over a device based on three Galfenol rods, where electrical and magnetic parameters are changed and tested with different mechanical sources in order to seek the best performance. [ABSTRACT FROM AUTHOR]

A self-start interior permanent magnet (IPM) motor can be a potential replacement of the conventional induction motor because of its high torque density, smaller size, higher efficiency, and power factor. Traditional self-start IPM motors are equipped with cage windings in the rotor for providing the starting as well as the damping torque. Cage-quipped IPM motors have limited starting and synchronization capabilities. This paper introduces a novel self-start radial flux (RF) hysteresis IPM motor. The rotor of the hysteresis IPM motor has a cylindrical hysteresis ring made of semi-hard magnetic material. High energy density Nd–B–Fe magnets are buried inside the rotor hysteresis ring. The ring is supported by a laminated steel sleeve, allowing the flux to travel radially inside the hysteresis ring. In this paper, the design and performance analysis of a 3-phase 4-pole 1-HP RF-hysteresis IPM motor is carried out using finite-element analysis. The performance of the designed RF-hysteresis IPM motor is compared with similar 1-HP circumferential flux type hysteresis and cage-equipped IPM motors. Based on analysis and simulation, the RF-hysteresis IPM motor demonstrates higher starting and synchronization capabilities than conventional self-start IPM motors. [ABSTRACT FROM AUTHOR]

To analyze the heating phase of an induction heated injection molding tool precisely, the temperature-dependent magneticproperties, B–H curves, and the hysteresis loss are necessary for the molding tool materials. Hence, injection molding tool steels, corematerials among other materials have, in this paper, been characterized for their temperature-dependent magnetic properties. Theproperties have been measured using a vibrating sample magnetometer, able to reach to 350 °C. The established material databasecomprises the B–H loops, from which the mean B–H curve, relative permeability versus magnetic flux density, and hysteresis lossversus magnetic flux density have been extracted and are presented. [ABSTRACT FROM AUTHOR]

In the past decade, nondestructive electromagnetic techniques have been extensively used for the characterization of materials. In this paper, the relation between the microstructural/mechanical characteristics of D2 tool steel with magnetic and electrical properties and eddy current (EC) test outputs has been established. Quenched samples obtained from different austenitizing temperatures (from 1000 °C to 1130 °C) were used to investigate the effect of retained austenite, martensite, and carbides phase fraction as well as prior austenite grain size, on the electromagnetic properties such as electrical resistivity and magnetic saturation. Variations of induced voltage in the pickup coil and location of impedance point in the impedance plane as a function of austenitizing temperature were interpreted by considering the changes in magnetic saturation and electrical resistivity and their effects on the EC outputs. This paper indicated that there is a good correlation between the EC parameters and retained austenite. [ABSTRACT FROM AUTHOR]

This paper concerns the detection of local magnetic induction in peripheral regions of transformer cores. Induction distributions are important for the interpretation of local losses and magnetostriction. Most authors use advanced numerical modeling-like FEM for the computation of local induction values. However, effective estimations tend to be impossible due to non-linearity, extreme anisotropy, and complex effects of hysteresis. As an alternative to FEM, the conventional method for local measurements is to use arrays of single-turn search coils. However, this method is laborious, and it affects the measured values in strong ways due to the thickness of the arranged wires and artifacts from the drilled holes. This paper presents a novel approach for peripheral core regions based on measurements with a tangential induction coil, i.e., a field coil with a ferromagnetic core. The sensor was tested on a model transformer core stacked from three packages of different widths of grain-oriented electrical steel, for the nominal induction of 1.7 T. As an advantageous effect, the sensor does not cause any interlaminar air gaps and detects the amplitude of the induction not only in planar, but also in lateral positions. Results from \boldsymbol \sim 100 measuring positions are presented. They show that the induction distribution is inhomogeneous with variations up to \boldsymbol \sim 15 %. High induction values were measured in the widest main package of the core, in contrast to much lower ones in the outer packages. On the other hand, the corners, yokes, and T-joints show much more uniformly flux distribution. The findings of this paper can be assumed to be relevant for industry in order to optimize the construction of cores for the purpose of their uniform utilization. [ABSTRACT FROM AUTHOR]

Through the conversion from mechanical to electrical energy it is possible to monitor a vibrating machine of any kind by exploiting the mechanical energy produced by the vibration. To this end, one can use direct force devices inserted in the supports or in the kinematic chain of the vibrating contrivance or cantilever devices with seismic masses. Regarding the devices of the first type, the maximization of the electrical output depends on various parameters. This paper, through a combined experimental and modeling approach, analyzes the behavior of a transducer based on a rod of Terfenol-D. Many parameters are analyzed, such as the frequency of the vibration, amplitude of the force transmitted by the vibration, characteristics of the coupled electrical circuit, magnetic, and mechanical bias. It is shown how the output power and electrical current are strongly influenced by the mechanical and magnetic bias. In addition, avoiding tensile stresses, this paper shows how the maximum output power is obtained when the mechanical bias is close to the amplitude of the dynamic force imposed by the vibration. [ABSTRACT FROM AUTHOR]

An energy saving permanent magnet type magnetizer is proposed, examined, and validated in this paper for the manufacturing of linear pattered magnetic medium for the precision control application. With the ultimate goal placed on providing sufficient magnetic field to overwrite and modify patterns on the magnetic media, parameter studies are conducted through finite element studies with results validated by magnetic flux density distribution measurements from produced incremental and index point patterns. Feasibility of utilizing the patterned medium for positioning control is validated through repeatability measurements, indicating that the proposed magnetizer can produce magnetic patterns rendering adequate magnetic signal strength and repeatability in linear precision control applications. [ABSTRACT FROM AUTHOR]

This paper presents the characteristic analysis and experiment of surface-mounted type variable-flux permanent-magnet machines considering magnetization and demagnetization based on electromagnetic transfer relations. For this purpose, we derive the analytical solutions for the magnetic fields generated by the magnetization level of AlNiCo magnets and currents on the basis of the transfer relations in terms of a 2-D polar coordinate system. The magnetization levels of the AlNiCo magnets are determined by the magnetic fields generated by the armature reaction field. A 2-D permeance function is also introduced to consider slotting effects. The analytical results of the magnetic field are validated extensively with finite-element (FE) analyses. On the basis of these solutions, the induced voltage is also determined analytically. Finally, the predictions are compared with FE analyses and measured data to confirm the validity of the analysis methods presented in this paper. [ABSTRACT FROM AUTHOR]

In this paper, we show that perpendicular magnetic anisotropy can be achieved in polycrystalline Ni80Fe20 films on MgO underlayers grown on thermally oxidized Si substrates. The perpendicular magnetic anisotropy is already present in the as-deposited films and preserved after thermal annealing. This paper points out the crucial role of the capping layer on the perpendicular magnetic anisotropy stabilization. By changing the nature of the capping from MgO, V, Nb to Ta, the value of the surface anisotropy constant is increased from 0.3 ± 0.05 erg/ \mathrmcm^\textbf 2 in the case of the MgO to 0.79 ± 0.06 erg/ \mathrmcm^\textbf 2 in the case of the Ta capping, respectively. For Ta capped samples, the perpendicular magnetization is achieved for Ni80Fe20 films with an effective thickness below 1.1 nm. [ABSTRACT FROM AUTHOR]

This paper reports the results of investigation on deposition and characterization of (Ni80Fe20)100–xCrx ( $x = 20$ , 40, 60, 80) alloy thin films onto Si (100) substrates at room temperature by direct current (dc) magnetron sputtering. Hysteresis loops on vibrating sample magnetometer graphs indicate that the addition of Cr increases coercivity of (Ni80Fe20)80Cr20 and (Ni80Fe20)60Cr40 films, whereas (Ni80Fe20)40Cr60 and (Ni80Fe20)20Cr80 films indicate no significant hysteresis loops. X-ray diffraction (XRD) results confirm that thin film samples are found to have face-centered-cubic structure with the preferred orientation mostly along (111) diffraction plane. In addition, crystallite size calculations were obtained from the Scherrer equation. Finally, the surface topography of the films is analyzed by means of the atomic force microscopy technique and correlated with XRD patterns. Our results suggest that Cr addition has a significant influence on the magnetic and structural properties of (Ni80Fe20)100–xCrx thin films. [ABSTRACT FROM PUBLISHER]

This paper shows that there is very little effect of the silicon content on the hysteresis component of the magnetic losses when two steels with 2.45% and 3.3% silicon were compared. Two non-oriented steels with 2.45 wt% and 3.3 wt% Si have been investigated. The Hysteresis component was measured by two techniques, in an Epstein frame: by a quasi-static test at 5 MHz and by extrapolating the total loss from frequencies above 50 Hz. The results showed that the quasi-static hysteresis loss (5 MHz) is not affected by increased Si content. The method of measurement by extrapolating—from frequencies above 50 Hz—($W_{h}^\ast $) proved inaccurate, as it is influenced by the electrical resistivity of the steels. [ABSTRACT FROM AUTHOR]

This paper reports on a strongly physics-based minimal circuit model for polycrystalline cores, such as ferrites, including dimensional resonance (DR). The models and main properties of DR and hysteresis are recalled, a circuit model is described that incorporates the various phenomena, and it is mentioned how its parameters are extracted by broadband linear response and low-frequency nonlinear measurements. Finally, the simulations are validated with measurements for a specific example. The model turns out to predict accurately the magnetic behavior in the high-frequency nonlinear region. [ABSTRACT FROM AUTHOR]

In this paper, a general method for making nanoscale Au–Fe3O4 clusters in an oil-in-water emulsion is reported, which involves thermolytic decomposition of Fe(acac)3 and reduction of AuCl3 in a hot oleyl amine–oleic acid mixture. A detailed investigation by transmission electron microscopy (TEM), X-ray diffraction, UV-vis, and vibrating-sample magnetometry was done in order to study the morphology and properties of the hybrid nanoparticulate clusters (NPCs). The NPCs are all spherical and their building blocks are individual Au and Fe3O4 nanoparticles (NPs) with an average diameter of 9.6 and 7.1 nm, respectively. TEM images show that these clusters have a flower-like morphology with controllable size. It is found that the cetyltrimethylammonium bromide concentration, the time, and the temperature of reaction are three important parameters that significantly affect the shape, size, and magnetic properties of these clusters. Magnetic measurements reveal the superparamagnetic behavior of individual NPs of Fe3O4 with a blocking $T_{\mathrm {B}}= 80.2$ K. The blocking temperature is significantly shifted to higher temperatures in the case of the clusters. The Au–Fe3O4 NPCs show a plasmonic peak at 530 nm and have a much higher magnetization than the individual NPs, making them better suited for biomedical applications. [ABSTRACT FROM AUTHOR]

In this paper, the partitioned stator (PS) structure is extended to variable-flux memory machines, forming two newly emerged PS switched-flux memory machines (PS-SFMMs) with series and parallel hybrid magnet configurations. From the perspective of geometry, both two PS-SFMMs share identical outer stator and rotor segments, while two different types of permanent magnet (PM) arrangements are employed in the inner stationary part. Thus, the developed machines can inherent the geometric separation of the armature winding and PM excitations from the PS design, thus achieving acceptable torque capability, and excellent air-gap flux control. A comparative study between PS-SFMMs with series and parallel structures is established. First, the topologies and operating principle are introduced, respectively. In addition, the design tradeoffs and PM sizing of the two PS machines are revealed and optimized with a simplified magnetic circuit model. Then, the electromagnetic characteristics of PS-SFMMs with different magnetic circuits are investigated and compared with the finite-element (FE) method. The FE results are validated by the experiments on a parallel prototype. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical and experimental study on high-frequency (>5000 Hz) output characteristics of the giant magnetostrictive transducer (GMT) at varied operating conditions. Based on the Jiles–Atherton model, Maxwell’s equations, Newton’s law, and Fourier’s heat transfer equation, a nonlinear electromagnetic–mechanical–thermal multi-field coupled finite element model for GMT is established. The output displacement amplitude of the magnetostrictive rod and the acceleration of vibrating horn at the GMT device are measured and analyzed at varied exciting amplitude of ac magnetic field and frequencies (from 5600 to 7000 Hz). The frequency dependences of permeability and magnetoelastic coupling coefficient obtained from the experimental results are used in revising the model parameters. These output characteristics analysis results can provide theoretical and experimental guidance in the optimization of structural design and precise controlling for high-frequency GMT system. [ABSTRACT FROM AUTHOR]

This paper presents a 3-D magnetic equivalent circuit (MEC) network that integrates the hysteresis model for the analysis of the axial field flux-switching (AFFS) memory (AFFSM) machine. Similar to finite element method, meshing is used to subdivide the model into smaller domains called elements, over which a set of element equations and a reluctance network equation are built. Newton–Raphson method is adopted to handle the nonlinear problems. The fixed-point technique is introduced to cope with the problem involving hysteresis. The proposed method is capable of predicting the operation of the low coercive force permanent magnet during flux regulation and the electromagnetic field distribution of the machine. Finally, the proposed 3-D MEC method is implemented for analysis of the AFFSM machine. MEC results are compared with 3-D finite element analysis and experimental results. The results show that the proposed method offers reasonable accuracy with moderate computational effort. [ABSTRACT FROM AUTHOR]

This paper investigates the effectiveness of the Cauer circuit modeling for dynamic hysteretic property in iron loss analyses of rotating machines. We apply the method to an interior permanent magnet synchronous motors fed by pulsewidth modulation inverter and compare their performance with a conventional iron loss estimation method based on 1-D finite-element analyses. As a result, almost the same iron loss is obtained by using the Cauer circuit modeling with lower computational cost. [ABSTRACT FROM AUTHOR]