Behavior of Medium-frequency Core Loss in Fe-based Nanocrystalline Soft Magnetic Alloys

1. IntroductionFe-based nanocrystalline soft magnetic alloys exhibit excellent synthetical magnetic properties, inparticular, lower core losses at medium and highfrequenciesll~4], and are applied in considerable widefrequency range in more extensive fields. Therefore,the investigations of the core losses of these alloys appear more and more important. As far as the applications of these alloys are concerned, such a widefrequency range is artificially and roughly divided intothree segments, i.e…     

General Properties of Low-frequency Power Losses in. Fe-based Nanocrystalline Soft Magnetic Alloys

1. IotroductlonAs early as 1969, it was reported that the dynamicloss at 50 Hi in the high-grade grain-oriented 3%SiFereaches about 75% of the practical measured total lossP and is much larger than the so--called classical eddycurrent loss Pc,l']; It was also observed that the total loss per cycle p/f nonlinearly increases with increasing frequency f in the low frequency range notmore than 100 Hi[1]. The above mentioned nonlineardependences have early been observed in many crystalline and am…     

Hysteresis Properties of Magnetic/Non-Magnetic (M/NM) Multilayers: Monte Carlo Investigation

In this work, Monte Carlo simulation was used to model the dynamic hysteresis behavior of magnetic/non-magnetic multilayers in the framework of Heisenberg model using the spin-flip algorithm. The purpose is to investigate the hysteresis properties while varying the direction of external applied magnetic field and temperature taking account interface composition of magnetic/non-magnetic atoms. From the results, with thermal variation and interface composition, the simulated hysteresis loops change significantly due to the competition between magnetic anisotropy in magnetic films and the presence of isolated clusters at the interface.     

Analytical Computation of the Full Load Magnetic Losses in the Soft Magnetic Composite Stator of High-Speed Slotless Permanent Magnet Machines

This paper presents an analytical model for predicting the stator full load magnetic losses in high-speed slotless permanent-magnet machines with surface-mounted magnets on the rotor and a stator core made of isotropic and conductive soft magnetic composite material (SMC). The losses are derived from the computation of the two-dimensional magnetic field distribution created by the rotor magnets, the currents in the stator windings and the eddy currents that circulate in the SMC stator core, according to the time and space harmonics. Both eddy currents and hysteresis losses are computed. The model is cross-validated by 2-D FE analysis in terms of magnetic field distribution and eddy currents losses. 3-D FE simulations are also carried out to quantify the end-effect on the stator no-load eddy current losses. The developed model is an efficient machine design tool, used here to quantify the variations of both the eddy currents and hysteresis losses under full load operation when the control angle is modified.      

Dynamic and quasi-static behaviors of magneto-thermo-elastic stresses in a conducting infinite plate subjected to an arbitrary variation of magnetic field

Summary In the present paper, dynamic and quasi-static behaviors of magneto-thermo-elastic stresses in a conducting infinite plate subjected to an arbitrary variation of the magnetic field are investigated. It is assumed that a magnetic field defined by an arbitrary function of time acts on both side surfaces of the infinite plate in the direction parallel to its surfaces. Fundamental equations of one-dimensional electromagnetic, temperature and elastic fields are formulated. Then, solutions of magnetic field, eddy current, temperature change and both dynamic solutions and quasi-static ones of stresses and deformations in the infinite plate are derived analytically. The solutions of stresses are determined to be sums of thermal stress caused by eddy current loss and magnetic stress caused by Lorentz force. For the case that the arbitrary function is given by the sine function, the dynamic and quasi-static behaviors of the stresses are examined by numerical calculations.     

Peculiarities of Pinning and Microwave Absorption Hysteresis in Thin Superconducting Films

The results of experimental and theoretical studies of the hysteretic microwave absorption (MWA) in the superconducting Bi₂Sr₂CaCu₂O₈ thin films are presented. It has been found experimentally that the hysteresis loop manifests some unusual features such as the non-monotone hysteresis variation and the change of a hysteresis sign. We have shown that such unusual behavior is due to the special nature of the bulk pinning in a superconducting film with a thickness comparable with the field penetration depth. The theoretical model of the MWA hysteresis has been developed taking into account the inhomogeneous distribution of centers with different symmetry of a pinning potential and their variation with the magnetic field value.     

基于动态自由能磁滞模型的GMM-FBG电流传感器磁滞建模与参数辨识

为解决GMM-FBG电流传感器中存在的磁滞非线性和涡流损失问题,提出了一种耦合涡流损失模型的动态自由能磁滞模型,采用非线性遗传算法对该模型进行参数辨识和优化,提高了模型在工频下对磁滞曲线的预测精度.搭建了 GMM-FBG电流传感器实验平台,利用所建的磁滞模型对传感系统进行建模补偿和实验验证.实验结果表明该模型能够较好地...     

Viscosity-based magnetodynamic model of soft magnetic materials

A time-stepping method based on the concept of magnetic viscosity developed to reproduce the excess loss in electrical steel is proposed. A numerical scheme for simultaneous solution of Maxwell equations and equations describing the magnetic viscosity has been developed. The method is suitable for describing arbitrary magnetization regimes such as waveforms associated with pulsewidth modulation (PWM) voltage excitation, and the model differential equations can be conveniently combined with equations of an external electric circuit. The accuracy of the proposed dynamic model is shown using three nonoriented electrical steel as examples. Fitting of the magnetic viscosity parameters for one sinusoidal flux regime enables dynamic hysteresis loops and losses to be predicted with high accuracy over a wide range of frequencies and amplitudes of sinusoidal or nonsinusoidal flux densities.     

Magnetic field dependence of ac losses in multi-filamentary superconducting wires

The magnetic field dependence of ac losses due to nonlinear flux penetration into superconducting filaments, ie, nonlinearity between an applied magnetic field and a penetrated flux, has been studied experimentally for multi-filamentary superconducting wires with Nb-Tl filaments and Cu matrix. In order to observe this effect, ac loss measurements were extensively carried out for the cases of applied transverse ac magnetic fields ranging from 0.06 to 50 Hz in frequency and from 10^?3 to 0.2 T in amplitude. Shifting of the frequency corresponding to the peak of the eddy current loss with the amplitude of applied magnetic fields was revealed experimentally. The results obtained were explained by taking into account the magnetic field dependence of the effective permeability of the wire originated from nonlinear flux penetration into superconducting filaments. The associated frequency dependence of the hysteresis loss is also discussed.     

A finite element method to compute three-dimensional magnetic field distribution in transformer cores

A numerical method is proposed to compute three-dimensional magnetic field distributions in nonlinear nonhomogeneous media, neglecting hysteresis and eddy currents. The magnetic field is derived from a scalar potential satisfying a nonlinear elliptic equation, which is solved by a convergent iterative method. A finite element program has been developed to compute the magnetic field distribution in transformer cores. Some numerical results for a butt and lap corner configuration are discussed.     

A viscous-type dynamic hysteresis model as a tool for loss separation in conducting ferromagnetic laminations

A viscous-type dynamic hysteresis model (DHM) that is compatible with any static hysteresis model is described. In contrast to existing dynamic models, the DHM is characterized by fixed desired properties over an infinite frequency range and provides the possibility of changing the shape of the steady-state hysteresis loop. The way the DHM is combined with Maxwell equations makes it possible for the first time to separate all three components of the total loss in conducting ferromagnetic laminations. These are the static hysteresis loss, classical eddy-current loss, and the excess loss treated as a dynamic hysteresis component. The study of their frequency dependencies opens a possibility of accurate iron loss prediction based on the loss separation principle.     

ON A NUMERICAL METHOD FOR THE EVALUATION OF ELECTROMAGNETIC LOSSES IN ELECTRIC MACHINERY

The paper deals with a numerical method for the evaluation of the magnetic iron losses in steel laminations used in rotating electric machinery. The magnetic hysteresis and the eddy current effects are directly and simultaneously taken into account. Hereby commonly used analytic expressions for the distribution function in the widely adapted Preisach hysteresis model are found to be not quite accurate. The magnetic circuit is decomposed into magnetic and air gap network elements, connected by fundamental loops. The magnetic network elements show a finite element structure. The kinematics of the electric machine is deliberately taken into account by an interpolation technique. Although the model retains the essential features of a cumbersome 3-D problem, a relatively simple algorithm may be developed. For the resulting algebraic system, we propose a suitable decoupling technique, which is efficient from the computational point of view. Numerical experiments show that the results obtained by our numerical approach are in good agreement with the known behaviour of the magnetic material.     

Methods for magnetically nonlinear problems involving significanthysteresis and eddy currents

The authors consider the modelling of magnetic saturation and hysteresis within finite-element eddy-current calculation procedures. Specific attention is given to time-stepping methods which deal with both saturation and hysteresis and to single-harmonic time-periodic approximations for cycle problems. It is shown that time stepping results are very close to measured losses in cases where there are significant saturation, hysteresis, and eddy currents. It is also shown that periodic approximations can produce solutions which also agree well on loss but rather less well on other parameters, particularly stored energy. Rotation field components are shown to be a major modelling problem     

Heat transfer from plates to conductors: from toroidal field model coil tests analysis to ITER model

During a safety discharge of toroidal field type magnets, eddy currents and associated heat generation are induced in the plates. A model has been developed from the thermohydraulic code Gandalf with introduction of the equations of the heat diffusion from plates to conductors through the steel and insulation. The comparison of calculation and experimental results for the ITER toroidal field model coil is presented.Preliminary analysis for the ITER toroidal field coils is also presented, taking into account the conductor parameters, the magnetic field and the external hydraulic circuit. The possible quench of the magnetic system is discussed.     

Temperature-dependent ferroelectric switching of 1–3 type piezocomposites: an experimental and theoretical study

An investigation on the temperature-dependent behavior of 1–3 piezocomposites for different fiber volume fractions and bulk piezoceramics is carried out. Experiments are conducted on 1–3 piezocomposites at room and elevated temperatures under a high cyclic electric field to understand the behavior of these materials. Temperature-dependent effective properties of piezocomposites are measured using resonance technique. A simple analytical model based on equivalent layered approach is proposed for the determination of the effective properties of 1–3 piezocomposites at elevated temperature. A uniaxial constitutive model has been developed based on a thermodynamic approach, to predict the nonlinear behavior of 1–3 piezocomposites under thermo-electrical loading conditions. Volume fractions of three distinct uniaxial variants are used as internal variables to describe the microscopic state of the material. A nonlinear hardening parameter based on a Gaussian function is used to describe the grain boundary effects. The predicted effective properties are used in the proposed uniaxial model and the classical dielectric hysteresis (electric displacement vs. electric field) as well as butterfly curves (strain vs. electric field) are simulated and compared with experimental data. It is observed that the variation in fiber volume fraction and temperature has a strong influence on the response of 1–3 piezocomposites.     

偏转磁芯铁氧体材料的磁滞损耗分析

对偏转磁芯所采用的铁氧体材料的磁滞损耗特性进行了分析,得出了磁滞损耗功率与频率、磁通密度和温度的经验公式。对磁滞回线中涡流的影响进行了分析,得出在目前应用的偏转频率下,磁芯损耗中磁滞损耗占主要部分。根据经验公式,对计算磁滞损耗的方法和在计算温度分布中的应用进行了介绍。     

Effects of Biaxial Crystal Field on the Magnetic Properties on?a?Spin-1?Ising?System

Within the effective field theory (EFT) with a probability distribution technique that accounts for the self spin correlation functions, the magnetic properties such as the hysteresis loops, susceptibility and magnetization of a spin-1 Ising system with effects of a biaxial crystal field are studied. The effects of the biaxial crystal field on the magnetic properties are discussed and numerical calculations are performed and analyzed for the cases of the honeycomb lattice. A number of interesting phenomena such as the shape of the hysteresis loops and the susceptibility have been found.     

Measuring the Hysteresis Loop of Permanent Magnets With the Pulsed Field Magnetometer

We discuss a comprehensive approach to the characterization of permanent magnets with the pulsed field magnetometer. The approach is based on a systematic comparison of the results obtained by this method with those from the conventional closed-circuit and open-sample methods and on the assessment of the dynamic phenomena engendered by the application of the fast exciting field pulse. Such phenomena derive from the thermal fluctuation after effect and the eddy currents, whose contributions to hysteresis loop swelling are brought to light and separately evaluated. We show that the quasi-static hysteresis loop can be retrieved from the dynamically obtained one by compensating for the magnetic viscosity field, found to be proportional to the coercive field, and the eddy-current counterfield. A simple analytical formulation accounts for and predicts the effect of the counterfield.     

Hysteretic dynamics of active particles in a periodic orienting field

Active motion of living organisms and artificial self-propelling particles has been an area of intense research at the interface of biology, chemistry and physics. Significant progress in understanding these phenomena has been related to the observation that dynamic self-organization in active systems has much in common with ordering in equilibrium condensed matter such as spontaneous magnetization in ferromagnets. The velocities of active particles may behave similar to magnetic dipoles and develop global alignment, although interactions between the individuals might be completely different. In this work, we show that the dynamics of active particles in external fields can also be described in a way that resembles equilibrium condensed matter. It follows simple general laws, which are independent of the microscopic details of the system. The dynamics is revealed through hysteresis of the mean velocity of active particles subjected to a periodic orienting field. The hysteresis is measured in computer simulations and experiments on unicellular organisms. We find that the ability of the particles to follow the field scales with the ratio of the field variation period to the particles'' orientational relaxation time, which, in turn, is related to the particle self-propulsion power and the energy dissipation rate. The collective behaviour of the particles due to aligning interactions manifests itself at low frequencies via increased persistence of the swarm motion when compared with motion of an individual. By contrast, at high field frequencies, the active group fails to develop the alignment and tends to behave like a set of independent individuals even in the presence of interactions. We also report on asymptotic laws for the hysteretic dynamics of active particles, which resemble those in magnetic systems. The generality of the assumptions in the underlying model suggests that the observed laws might apply to a variety of dynamic phenomena from the motion of synthetic active particles to crowd or opinion dynamics.     

Alternating Current Losses in Ag-Sheathed (Bi, Pb)-2223 Multifilamentary Tape at Liquid-Nitrogen Temperature

The alternating current losses have been investigated at 77 K on the silver-sheathed (Bi, Pb)-2223 multifilamentary tape having 37 filaments using an inductive technique under ac magnetic field with frequencies between 100 and 510 Hz. The measured data on the multifilamentary tape have been discussed vis-à-vis that reported for monofilamentary tapes. The results obtained could be accounted fairly well by considering contributions from the eddy current losses in the silver matrix along with the hysteresis losses in the superconducting filaments.