Generation of method AC Ampere force using eddy current inside a nonmagnetic thin plate and its effect on electrodynamic suspension

In this paper, we propose a novel method for magnetic levitation force generation. In our method, we utilized three AC electromagnets that generate the inductive and AC Ampere forces. One electromagnet is installed above the surface and the other two in both sides of thin plate. Phase conditions providing the maximum levitation force are derived from 2‐dimensional finite element analysis. In order to confirm the performance of the proposed method, we performed some experiments. The experimental results show that in difference from conventional AC methods, the magnetic levitation force is increased around 5.9 times for the same eddy current inside the aluminum plate. In addition, the relations between excitation frequency, plate thickness and total levitation force are explained in details. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 48–56, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20905     

中频感应熔炼设备在节能减排中的应用

为实现高效环保的金属熔炼工艺,转变冲天炉和工频熔炼炉高耗煤高耗能的传统模式,设计研究了一套中频感应熔炼系统。系统主要包括中频电气系统、炉体熔炼系统以及炉衬厚度检测装置等部分。中频电气系统由中频电源和电热电容器柜组成,炉体熔炼系统由无芯感应炉和冷却机组成。中频感应熔炼系统利用高密度磁力线切割金属材料,并利用涡流加热使材料迅速熔化,能高效地熔炼各类金属,且基本不生成有害废弃物。该系统在提高能源利用率和节能减排等方面具有良好的性能,自动化程度较高,在未来市场中有着广阔的应用前景。     

A study on the transverse edge effect of an eddy current brake with a solid steel secondary

The eddy current brake is a type of braking system used for railway vehicles. Because rail heating is a problem in this type of brakes, they have not been put to practical use in Japan. Therefore we proposed using a linear induction motor (LIM) for dynamic braking in the eddy current brake systems. In this paper, we investigate the transverse edge effect on an eddy current brake using an LIM with the solid steel rail as a secondary conductor. The objectives of this investigation are to clarify the transverse edge effect on a rail and to make it easier to determine the characteristics of such an eddy current brake. We find that the lateral surface of a solid steel rail must be considered as an electromagnetic overhang, and that the transverse edge effect of the rail is approximately the same as that of a simple U‐shaped steel plate or a wide, flat steel plate. These findings enable us to apply a simplified analysis method using a traditional modifying coefficient of the transverse edge effect, but from a new perspective. Because this simplified analysis method can easily evaluate the performance of eddy current brakes, it is useful in the early development stages of such brakes. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Eddy current magnetic levitation. Models and experiments

We present a simple demonstration of eddy-current magnetic levitation using a small copper coil, energized with 60 Hz AC and levitated over an aluminum plate. The processes that generate magnetic forces are identified using Maxwell's equations. Through this experiment, a method for determining lift-off power, levitation height and suspension resonant frequency is shown. The principles outlined in this article have numerous applications to magnetic levitation, induction heating and other electrodynamic processes involving induced eddy currents. Scaling laws show how to size a suspension conductor and power supply for a given levitated load     

A zone‐control induction heating (ZCIH) system for semiconductor processing

This paper proposes a new induction heating technology capable of controlling a precise exothermic distribution, which is termed zone‐control induction heating (ZCIH). The ZCIH system consists of two or more sets of a high‐frequency inverter unit and a work coil. The inverter units control the phase angle of the coil current to be in phase with each other. The ZCIH has the capability of operation with the mutual inductance, and enables locating the coils as close as possible. As a result, the ZCIH technology makes it possible to achieve rapid heating performance with extremely precise exothermic distribution. This paper presents experimental results of a 150‐kW six‐zone ZCIH system for semiconductor heat processing. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(1): 37–45, 2010; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20908     

神经网络预测应用于横向磁通感应加热中涡流场与温度场的有限元分析

利用神经网络预测横向磁通感应加热中连续运动金属薄板表面涡流分布和温度分布。所采用的两条神经网络中，一条对涡流场分布进行预测，另一条对温度场分布进行预测。在抽取的检测样本中，预测温度分布的相对误差平均值为1．6～3．2％，以神经网络预测结果作为非线性有限元离散方程组迭代求解的初值，比薄板初始温度作为初值的情况节省55．6～67．6％的迭代次数。     

Surface charge analysis in eddy current problems

To estimate the characteristics of electric machines that have conductors of complicated shape, it is effective to analyze the surface charge related to eddy current phenomena. However, the eddy current field is generally treated as a quasi‐static field in which the displacement current is neglected and the electric field is not defined in the nonconductive region in the calculation process. Therefore, when we use only the A –? finite element method (FEM) as a field analysis method, it is difficult to calculate the surface charge directly at the interface between conductive and nonconductive regions. In this paper, with this background, we propose a novel method of analysis of the surface charge based on both the A –? FEM with edge elements and the integral equation. This approach enables us to precisely calculate the surface charge. Some numerical results that demonstrate the validity of the proposed method are also presented, such as the surface charge analysis of linear induction motors for evaluating the relationships among the surface charge, eddy current, and conductor shape. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 145(1): 59–66, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10173     

零机械能输出感应电机

传统电机是机-电能量转换,损耗与温升是电机设计时需要削弱和避免的问题。该文从传统电机损耗与温升出发,提出了用于加热的零机械能输出感应电机。利用绕组所产生的径向磁场在实心结构的定子和转子铁心中感应产生涡流,将输入的电能全部转化为热能,具有定子、转子双边加热的特点。其独特的双边加热效果可解决挤塑类设备旋转螺杆加热瓶颈问题。建立了系统等效模型,给出了电磁功率解析表达式,采用有限元法分析了系统涡流分布与铁心端部效应。对样机进行加热实验,结果证明该种电机与传统线圈缠绕式电磁加热相比,具有节能高效、预热时间短、径向温差小等优点。     

电磁感应加热中加热物体位置的选择

在电磁感应加热中为了精确高效地实现目标温度分布,讨论了如何确定物体理想的加热位置。首先,分析并得出了在同一位置上涡流密度与空载磁场成正比例的结论,据此可知对加热物体位置的选择仅需研究加热装置的空载磁场。然后,由目标温度分布引出空载磁场的目标分布,由毕奥-萨伐尔定理推导出目标函数,并用数值计算方法求出目标函数值,由此可得物体理想的加热位置。最后,将该数学方法所得结果和软件仿真结果进行了对比,验证了该位置选择方法的合理性。运用Matlab程序实现此确定加热物体理想加热位置的数学方法,输入加热装置结构参数和目标温度分布能够简便有效地确定物体的加热位置。     

Eddy currents and electrical surface charges

In eddy current calculations, the displacement current in the non‐conducting space surrounding the eddy current region is usually neglected. This assumption enforces that the electric charge density and the accompanying normal components of the eddy current density on the surface of the eddy current region must vanish. If the field exiting source currents are not accompanied by charges this assumption may yield acceptable results for the eddy current distribution. However, if the field exiting source currents are accompanied by charges, this assumption may lead to totally wrong results for the current distribution in the eddy current region. An example is given which makes plain this point. To obtain correct results it is not necessary to employ the full set of Maxwell's equations capable to describe wave propagation phenomena also outside the eddy current region. It is shown in the paper that by replacing the displacement current density in the field describing equations by a specifically chosen current density function makes it possible to determine eddy currents and surface charges within the quasi‐stationary calculation scheme for arbitrary field exciting source currents which may or may not be accompanied by charges. The solution obtained in this way is shown to be unique. Copyright © 2003 John Wiley & Sons, Ltd.     

不同焊后热处理方式对P92钢近表面组织性能的影响

分别采用电阻加热及感应加热方式对P92 钢进行焊后热处理,分析了这2 种加热方式对P92 钢近表面组织性能的影响。结果表明：感应加热趋肤效应不会对趋肤层内母材产生明显影响;无论采用电阻加热还是感应加热,母材近表面碳化物的体积均明显大于母材中部碳化物,导致近表层母材金属抗拉强度降低,在满足热处理后焊缝性能要求的前提下,应尽可能降低热处理温度。     

Moment method analysis for capacitance and charge distribution of dielectric coated metallic disk and closed truncated cone isolated in free space

This paper presents a method for the evaluation of capacitance and charge distribution of a dielectric coated metallic disk and a dielectric coated metallic hollow truncated cone with top and bottom cover plates using the method of moments (MoM) based on pulse basis function and point matching. Boundary conditions for the potential on the conductor surfaces and continuity of the normal component of the displacement density at the dielectric‐free space interface is used to generate two integral equations. Two sets of simultaneous equations are formed from the two integral equations by using MoM. The total free charge on the conductor surface is found from the solution for the set of simultaneous equations. The validity of the analysis has been justified by comparing the data on capacitance available in the literature for metallic disk and hollow truncated cone with top and bottom cover plates, with the data on the capacitance, computed by the presented method for similar structures considering very low dielectric constant as well as very thin dielectric coating. Copyright © 2012 John Wiley & Sons, Ltd.     

热轧平板钢坯边部均温加热的感应透热技术研究

热轧钢板是电力、机械等重大装备行业的基本原材料,如何提高其生产率降低损耗是设备制造行业要研究的问题。针对热轧平板生产过程中的热轧平板边部温度降低所产生的问题进行了研究,并将中频感应加热技术应用于解决这一难题,详细分析了热轧平板边部电磁场感应加热技术的工作机理,提出了设计实用大型边部感应加热器应注意的事项。对准备开发生产热轧板边部感应加热器的企业有指导性作用。     

A systematic method for the development of a three‐phase transformer non‐linear model

In this work, a novel three‐phase transformer non‐linear model is developed. The proposed model takes into account the magnetic core topology and the windings connections. The non‐linear characteristic curve of the core material is introduced by its magnetization curve or by its hysteresis loop using the mathematical hysteresis model proposed by Tellinen or the macroscopic hysteresis model proposed by Jiles–Atherton. The eddy currents effects are included through non‐linear resistors using Bertotti's work. The proposed model presents several advantages. An incremental linear circuit, having the same topology with the magnetic circuit of the core, is used in order to directly write the differential equations of the magnetic part of the transformer. The matrix L _d that describes the coupling between the windings of the transformer is systematically derived. The electrical equations of the transformer can be easily written for any possible connection of the primary and secondary windings using the unconnected windings equations and transformation matrices. The proposed methods for the calculation of the coupling between the windings, the representation of the eddy currents and the inclusion of the core material characteristic curve can be used to develop a transformer model appropriate for the EMTP/ATP‐type programs. Copyright © 2009 John Wiley & Sons, Ltd.     

积分方程与解析法组合计算薄钢板的涡流损耗

介绍了采用将数值与解析联合起来计算矩形导电媒质涡流损耗的方法。首先利用积分方程法求出磁介质表面网格点的入射磁密,然后对这些任意分布的离散磁密点用双重傅立叶级数进行逼近,最后计算涡流损耗。通过验证,计算值与测量值吻合很好,证明了该方法的可行性。     

Improvement of heating characteristics of molybdenum silicide thin film electric heaters

Molybdenum silicide (MoSi₂) has an electrical conductivity as high as that of a metal, and greater chemical stability than that of, for example, SiC, in various atmospheres. Therefore, many kinds of MoSi₂ bulk‐type heaters are used in practical operations up to 1800^°C, which is higher than the temperature of SiC heaters. However, MoSi₂ is fragile at room temperature and has low creep resistance at high temperature. The purpose of this study is to fabricate heaters using thin films of MoSi₂ deposited on alumina substrates and crucibles by RF magnetron sputtering and to evaluate their characteristics. MoSi₂ thin film was deposited on the outside of an alumina crucible without heating the substrate and then Pt wire was attached using a Pt paste with sintering in a vacuum. This MoSi₂ thin film heater showed almost linear resistance–temperature (R–T) characteristics and a uniform heating state. It also showed good controllability of voltage and stability in the power–T characteristics for operations up to 1000^°C. However, at a heating temperature of 1300^°C, the heating area of MoSi₂ thin film decreased because of the reaction between Pt and MoSi₂ in the case of long‐term heating. Thus, Mo thin film was deposited as a buffer layer between Pt and MoSi₂ thin film to prevent such a reaction. This thin film heater showed good linear R–T characteristics up to 1200^°C. However, the temperature coefficient of resistance changed with repeated heating operation as a result of the diffusion of Mo atoms into MoSi₂. Thus, a thin film heater was fabricated with Mo₃Si, having a higher Mo content than MoSi₂. This heater showed a low degree of diffusion of Mo or Pt atoms into the thin film and had excellent practical characteristics up to 1000^°C. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(2): 11–19, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20806     

感应加热电源站动态特性的仿真研究

随着感应加热电源系统容量的不断扩大,进一步发展由多个逆变器并联工作的感应加热电源站业已成为研究的新课题。本文借助于计算机仿真,对感应加热电源站的动态特性如负载及备用电源的投切、停机及故障保护等进行了初步研究,以供感应加热电源站分析与设计参考。     

Restraint Method for Overcoming Heating Irregularity and Improving Heating Equipment Efficiency for Beverage Cans Using High‐Frequency Induction Heating

We were able to reduce heating irregularities in equipment for heating beverage cans by using the high‐frequency induction heating method and determining the resulting improvement in the heating efficiency. The heating irregularity between the top and bottom of the can was reduced to less than 3°C by improving the arrangement of the heating coils for the beverage can by thinning the winding and changing the circuit configuration. The efficiency of power conversion was improved from 93.0% to 97.4%. In this paper, the configuration of the equipment and the experimental results are reported.     

SPICE‐aided modelling of dc characteristics of power bipolar transistors with self‐heating taken into account

This paper deals with the problem of calculations of the dc characteristics of power bipolar transistors (BJTs) with self‐heating taken into account. The electrothermal model of the considered devices dedicated for PSPICE is presented. The correctness of the model was verified experimentally in all ranges of the BJT operation. Two transistors—BD285 and 2N3055—were arbitrarily selected for investigation. A good agreement between the measured and calculated characteristics of these transistors was observed. Copyright © 2009 John Wiley & Sons, Ltd.     

A highly accurate algorithm for SF6 leakage detection

Sulfur hexafluoride (SF₆) is widely used in high‐voltage applications such as gas‐insulated switchgear (GIS) because of its excellent arc‐quenching properties. The main drawback of SF₆ is that it is a strong greenhouse gas. Detecting small SF₆ leakages in GIS is very important to protect the environment and to prevent the failure of aged GIS. To detect SF₆ leakage, the gas pressure is measured and compensated by gas temperature. Usually, the temperature of the container surface is measured instead of the actual gas temperature. However, the temperature of the container surface is affected by ohmic heating of the internal components and by ambient temperature changes. These factors lead to a difference in temperature between the container surface and the gas inside the container, causing significant fluctuations in the compensated gas pressure. To remove such fluctuations, we have developed a computational fluid dynamics (CFD) transient model that simulates the correlation between the mean gas temperature inside the container and the container's surface temperature. The CFD simulation factors in the load current and ambient temperature to estimate the true temperature of the gas inside the container as accurately as possible. The mean gas temperature inside the container is obtained using CFD simulation and by measuring the surface temperature. The fluctuations in the compensated gas pressure were reduced from 2.4 to 0.48% by using the proposed algorithm based on pressure compensation with the mean gas temperature. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.