Hysteresis loss free soft magnetic ferrites based on Larmor precession

A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite,the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field,and the hysteresis loss disappears in the ferrites.Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field.A higher Q value with relatively low permeability can be achieved by increasing the transverse field,which ensures that the ferrite can be operated at high frequencies,with magnetic loss being very low.

Calculation of Skin Depths and Eddy-Current Power Losses for Magnetic Position Sensors

We present a theoretic model to calculate skin depths and eddy-current power losses for a magnetic position sensor. Eddy-current, arised from the operation of an alternating-current excitation, induces secondary currents and fields between magnetic material and magnetic position sensor. In this paper, a magnetic position sensor system is simplified to be an outer-winding coil along the axial direction of a low carbon steel bar. The analytical model is derived from basic field and circuit theory considering a linear approximation for a nonlinear permeability. Thus the skin depths and eddy-current power losses from the model in eddy-current modeling techniques at various frequencies of an excited current source can be calculated. The proposed configuration is capable of predicting the skin depths and eddy-current power losses for a magnetic position sensor and has a consistence with experiments.

Magnetostrictive and Kinematic Model Considering the Dynamic Hysteresis and Energy Loss for GMA

Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.

A Physical Core-Loss Model for Laminated Magnetic Sheet Steels

A full-frequency instant core-loss equation built from the induction physical model of magnetic materials, where the iron loss, eddy loss, and hysteresis loss no longer have an integral term, and this new equation provides high simulation accuracy and performs dynamic core loss analysis on non-sinusoidal or pulse magnetic fields. The simulation examples use a high-grade electrical steel sheet 65CS400 by Epstein experimental data covering magnetic field 0.1 - 1.8 T and frequency 50 - 5000 Hz, and the average error of the simulated core loss is less than 4%. Since the simulation is converged by magnetic physical parameters, so the physical relevance of the similar laminated materials can be compared with the coefficient results. .

A Review of Medium Voltage Single-Core Cable Armouring, Induced Currents and Losses

Insulated underground cables have the potential to reduce power outages, maintenance costs, and transmission losses compared to overhead lines. On the other hand, they are exposed to several risks and physical damages, since they are buried in the ground. Though the cables are armoured in order to provide mechanical protection and achieve tensile strength, and also to provide effective conductance of earth fault currents. The main purpose of this paper is to introduce insulated underground cables, armouring process, and to analyze the induced currents in metallic parts such as sheath and armour that causeohmic losses which are categorized mainly in two groups as circulating current and eddy current. This paper presents a review on analytical techniques used to analyze the effect of magnetic fields, andcalculate the losses in the armour of the cables, besides providing the strategies and solutions used for armour loss reduction.

Magnetic Hysteresis and Complex Initial Permeability of Cr³⁺Substituted Mn-Zn Ferrites

The impact of Cr3+ ion on the magnetic properties of Mn0.50Zn0.50CrxFe2-xO4 (with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) has been studied. Ferrite samples were synthesized by combustion method and sintered at various temperatures (1250°C, 1300°C and 1350°C). The structural properties were investigated by means of X-ray diffraction patterns and indicated that the samples possess single phase cubic spinel structure. The lattice parameter decreases with the increase in Cr3+ content, as the ionic radius of Cr3+ ion is smaller than that of Fe3+. The average grain size (D), bulk density (ρB) and initial permeability (μi’ )decreases with increase in Cr3+ content whereas porosity follows its opposite trend. The ρB was found to increase with increase in Cr3+ content as the sintering temperature (Ts) is increased from 1250°C to 1350°C. The Ts affects the densification, grain growth and (μi’ ) of the samples. The (μi’ ) strongly depends on average grain size, density and intragranular porosity. The B-H loops of the compositions were measured at room temperature. The saturation magnetization (Ms), coercivity (Hc) and hysteresis losses were studied as a function of Cr3+ content. The Ms was found to decrease with the increase of Cr3+ content, which is attributed to the dilution of A-B interaction.

Calculation of AC Losses of CICC for Superconducting Outsert Coils in a Hybrid Magnet

This paper is devoted to predict AC loss of cable in conduit conductor （CICC） which is of importance in the design of conductors. The consideration for the conductor＇s design and main parameters for the magnets are introduced. In order to attain a good accuracy in the calculation of AC losses, the field distribution within superconducting outsert should be considered. Calculation of the AC losses, including hysteresis losses and coupling losses, is conducted. An emphasis is put on the hysteresis loss during the ramp up of the current to the operational current （15.3 kA） and the coupling loss of the conductor in a power-down condition for insert. The results are obtained to be 74.9 kJ and 950 J for 40 T hybrid magnets, respectively. Based on the calculation, a brief analysis of losses effect on the conductor design and the operation of magnet is given for the purpose that the capacity of the cryogenertor can be evaluated and the stability regime can be improved in our future work on the hybrid magnets.

Optimization of Power Transformer Design: Losses, Voltage Regulation and Tests

This paper presents the design approach used in designing transformers mostly used in power supplies and power systems. The paper will cover theoretical principles applied in analyzing magnetic circuits to better understand the operation of the transformer. Since well-designed transformer is supposed to meet the specifications of the environment that it is going to be used, there is a need to confirm after the transformer is built to make sure that it is going to operate efficiently and without a failure. Therefore, this paper will also present the traditional methods used to test transformers in the industries to make sure that it will operate within the prescribed loading limits and voltages. This paper will cover the transformer losses in detail including the test methods used to calculate nameplate parameters for power transformers used in power systems.

非正弦激励下高频变压器铁心动态磁滞特性模拟方法

高频变压器是DC/DC变换器的核心部件,其激励波形一般为非正弦波,工作频率可达数千赫兹以上,导致铁心损耗显著增加,准确模拟非正弦激励下高频变压器铁心动态磁滞特性,有助于铁心损耗计算以及变压器的电磁暂态分析。首先,该文考虑铁心磁化物理过程,利用系统级电力电子仿真软件PLECS中底层模块和语言编写程序,建立基于静态J-A磁滞模型和磁导-电容类比法的铁心静态磁滞磁导模型;然后,考虑高频条件下涡流效应与弛豫效应对铁心动态磁滞特性的影响,根据损耗统计理论建立铁心动态磁滞磁导模型;最后,基于模拟退火与Levinberg-Marquardt混合算法提取静态J-A磁滞模型参数,根据铁心损耗特性曲线采用最小二乘法提取动态损耗系数。对比分析不同占空比、高频方波电压激励下电流波形以及磁滞回线的仿真结果与实验测量结果,验证了模型的有效性。

高低频复合励磁磁心损耗量化的研究

针对高低频复合励磁磁元件磁心损耗难以精确测量和建模的问题,在详细分析现有磁心损耗测量方法和磁心损耗模型局限性的基础上,根据直流功率法测量原理搭建高低频复合励磁磁心损耗测量系统,利用损耗能精确测量的空心电感验证其测量精度。最后,基于直流偏置下脉宽调制(pulse width modulation,PWM)波励磁的磁心损耗模型,提出高低频复合励磁磁性元件的磁心损耗预测模型,并实验验证预测模型最大相对误差为-8.83%,具有较高的精度。

高速永磁电机铁耗精确计算两项式模型

基于分段带补偿项的铁耗计算方法,本文提出了一种适用于高速永磁电机铁耗精确计算的两项式数学模型。通过结合高速电机运行特性对频率和磁密区间进行双重划分,在Jordan损耗分离模型的基础上引入涡流及磁滞损耗补偿项考虑磁饱和、局部磁滞回环及涡流趋肤效应等非线性因素对硅钢片单位损耗特性的影响。该模型新增参数均为随频率和磁密变化的分段常函数,通过L-M算法拟合求解,在减小计算量的同时明确反映铁磁材料非线性对铁耗计算的影响,实现铁耗精确计算。最后,以某高速电机用硅钢片35SWH1900为例,对比了本文所提模型与Jordan损耗分离模型在单位损耗上的计算误差,实验结果表明所提模型计算误差基本在15%以内,能够有效提升高速永磁电机铁耗的计算精度。

矩形波激励对纳米晶合金高频磁化过程的微观影响机理

高频变压器工作时会面临占空比变化的激励情况,由于存在磁弛豫现象,矩形波占空比能通过改变铁心用材料纳米晶合金磁化时间,影响高频变压器能否达到饱和工作点。建立纳米晶合金微磁学模型,对该模型分别施加不同占空比D的矩形波激励,并定义了磁化速率v,从磁滞损耗P_(v)、v及磁矩偏转角速度ω三方面分析D对磁化过程的影响。结果表明,D=0.5时P_(v)最小,增大或减小D,都会导致P_(v)的增加,且满足两组不同占空比和为1的矩形波激励下,材料产生的P_(v)相同。若激励磁场处在上升沿,D=0.1时的v与ω最小,D=0.9时的v与ω最大;若处在下降沿,D=0.9时的v与ω最小,D=0.1时的v与ω最大。D会影响材料磁化时间,由于磁弛豫现象,改变磁化时间可决定材料能否达到饱和磁化状态,因此存在一个临界状态,该文将其定义为临界占空比D_(c)。结果表明,当D<0.5时D_(c1)的范围应处在0.2~0.21,D>0.5时D_(c2)的范围应处在0.8~0.81,为不同工况下高频变压器工作点的选取提供了参考依据。

基于NI myDAQ的积木式磁滞回线实验设计与教学实践

传统的磁滞回线教学实验仪使用的变压器铁磁材料和线圈都已固定,不利于比较硬磁材料和软磁材料的磁性质,不利于学生深入理解磁滞现象与磁材料物性的关系.结合多层次实验教学规范,设计了“积木式”磁滞回线实验装置,可更换磁性材料,通过用NI myDAQ采集次级线圈电压后,用数值积分获得磁感应强度,并使测量更准确、更直观,可加深学生对测量物理过程的理解.在教学上拓展到广义力(磁场强度)和广义位移(磁感应强度)概念,测量磁滞损耗(广义功)及其与磁场强度或磁感应强度之间的相位差关系.

The impact of magnetic field periodicity on the hysteresis loss in superconducting magnetic bearings

Since the discovery of high‐temperature superconductors(HTS),superconducting magnetic bearings(SMB)have attracted much attention for practical applications such as flywheel energy storage systems,electrical machines,gyroscopes,etc.,because of their ability to provide passive stable levitation under high‐load conditions.Despite providing contactless linear and rotational motion,SMBs gradually decelerate by AC losses mainly generated by magnetic field inhomogeneity.The main component of AC losses at low rotational speeds is hysteresis loss,which is said to be independent of rotational speed,intrinsic to HTS,and proportional to the cube of magnetic field inhomogeneity.Although the state‐of‐the‐art analytical expression of hysteresis loss in SMBs captures the general physics of the loss mechanism,it ignores the periodicity of the magnetic field in one complete rotation of the bearing.In this paper,the analytical expression of hysteresis loss is modified,taking into account the impact of magnetic field periodicity and the distribution of loss over the bearing surface.The new expression is tested by performing spin‐down experiments with magnets of different levels of inhomogeneity in an actual SMB environment.The impact of magnetic field inhomogeneity on the dynamic behaviour of the bearing is also investigated.The results show consistency between modified analytical calculations and experimental data.

DC performance and AC loss of cable-in-conduit conductors for International Thermonuclear Experimental Reactor

A reliable prediction of AC loss is essential for the application of International Thermonuclear Experimental Reactor(ITER) cable-in-conduit conductors(CICCs);however,the calculation of AC loss of ITER CICCs is a cumbersome task due to the complicated geometry of the multistage cables and the extreme operating conditions in ITER.In this paper,we described the models developed for hysteresis and coupling loss calculation,which can be suitable for the construction of ITER magnetic system.Meanwhile,we compared the results of theoretical analysis with the SULTAN test result to evaluate the numerical model we used.In addition,we introduced the n-value and AC loss with transport current for CICCs based on the DC measurement results at SULTAN,which lays the foundation for the further study.

Finite Element CAD Experiments on the Effect of Magnetic Loss in Power Transformers with Laminated Cores

The paper describes a simulated experiment that focuses on the numeric computation of magnetic loss in the laminated core of a single-phase power transformer. The students’ laboratory work is part of the library of experiments of the Electrical Machines virtual laboratory and makes use of the two-dimensional open-access electromagnetic field analysis software Finite Element Method Magnetics. The idea of the simulated exercise is to demonstrate how the magnetic loss caused by time-varying excitations affects the magnetic permeability, μ, of the laminated core and the terminal quantities of the energizing winding. A parametric analysis employing different values for the electrical conductivity and maximum hysteresis-induced angle of the laminated material yields five different field problems with increasing magnetic loss. Electric circuits characterized by the (I-V) operating point and reflected impedance of the energizing winding provide the information required to compute the changes in real power ΔP, reactive power ΔQ and magnetically stored energy ΔWm between successive problems characterized by increasing magnetic loss. The concept of reflected impedance helps to explain the physical meaning of the changes in power dissipation and energy storage in the laminated core.

Effect of Ball Scribing on Power Loss Separation of Fe-3%Si Grain-oriented Silicon Steel

Power loss of Fe-3%Sigrain-oriented silicon steelwas measured after ballscribing with different spacing using a self-designed tool.Three different sections of power loss,including hysteresis loss,abnormalloss,and eddy current loss,were measured and calculated,respectively.The loss variation and ratio were analyzed based on the experimentaldata.At 1.0 T,hysteresis loss of tested steelwith scribing spacing of 8 mm descends by 8.2% compared to samples without scribing,which is similar to the totalloss variation,and abnormalloss descends by 16.8%.At 1.0 T,hysteresis loss ratio of the steelwith scribing spacing of 16 mm ascends from 55.7% to 57.9%,and eddy current loss increases from 17.4% to 24.1%,while abnormalloss descends from 26.9% to 23.7%.The experimentalresults show that the reduction of power loss after scribing is mainly due to decreasing of hysteresis loss and abnormalloss.

变温条件下钐钴永磁材料损耗特性测量与定量分析

大功率永磁电机较高的工作温度会对转子永磁体的磁性能和损耗特性产生较大影响。本文通过自主研制的变温条件下永磁体交流损耗测试系统,对钐钴永磁体开展多磁通密度、宽频率、宽温度范围内的交流损耗测量实验,并基于测量数据在Bertotti损耗分离理论的基础上提出变温条件下交流损耗计算公式,对不同频率下交流损耗随温度升高的变化情况进行解释和验证。结果表明:钐钴永磁材料的磁滞损耗与温度呈正相关,而涡流损耗与温度呈负相关。且当交流磁场频率升高时,总损耗中涡流损耗占比增加而磁滞损耗占比下降,导致在不同频率交流磁场下总损耗随温度升高呈现出不同的变化趋势。研究结果可为实际工况下钐钴永磁电机的优化和设计提供重要参考。

成型压力和脱模剂添加量对FeNiMo磁粉芯磁导率和损耗的影响

采用溶胶-凝胶法实现对FeNiMo的SiO_(2)绝缘包覆后制备磁粉芯,考察了硬脂酸锌脱模剂和粉芯成型压力对粉芯磁导率和功率损耗的影响。结果表明,在100 mT/100 kHz条件下,脱模剂的添加对粉芯的磁滞损耗影响较小,对涡流损耗的影响较大。添加适量的硬脂酸锌可提高粉芯的密度和电阻率。随着成型压力增大,粉芯密度逐渐增大,电阻率逐渐降低,导致涡流损耗显著增高。对于不同压力成型的样品,总损耗主要来源于磁滞损耗,这主要由粉芯的矫顽力所决定的。经过优化后的硬脂酸锌添加量为0.25 wt%,成型压力为10 MPa,对应的有效磁导率和总损耗分别为56.8和709.7 kW/m^(3)(100 mT/100 kHz)。相比于其它的SiO_(2)包覆的磁粉芯,经过本实验优化的脱模剂添加量和成型压力制备的FeNiMo粉芯,具有更高的有效磁导率和更低的总损耗。

电感对DC/DC变换效率影响分析

针对电感对DC/DC变换性能影响的问题,以Boost变换器为例,对非理想情况下Boost变换等效电路和转换效率影响因素进行了分析,得到电感参数与电路输出电压、转换效率的关系。根据电感参数对电流纹波和电路转换效率影响的分析,在传统以临界连续电流为依据设计滤波电感值的基础上,提出了一种约束电感值选择范围的方法,并对KS226-075A磁芯的局部磁滞损耗和铜耗进行了计算,得到DC/DC变换器转换效率随电感值增大的变化趋势。最后,通过实验验证了理论的正确性和方法的可行性,同时根据实验结果修正了电感值的选取范围,并对计算结果与实验结果存在的误差进行了分析说明。