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1.
采用传统陶瓷工艺制备了BaCoTiFe10O19铁氧体,结合相结构、显微形貌分析和对材料磁化机理的讨论,主要研究了Bi2O3加入量和烧结温度对钡铁氧体高频磁性的影响.实验表明,起始磁导率和共振频率随Bi2O3加入量的变化存在极值,当Bi2O3的加入量为7.5mol%时钡铁氧体具有较高的磁导率和较低的磁共振频率,偏离7.5mol%均导致磁导率的降低和磁共振频率的升高;高烧结温度导致晶粒尺寸的长大和晶格结构的完善,有利于提高材料的磁导率,同时降低磁共振频率. 相似文献
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Qiangyuan Zhang Peng Zheng Liang Zheng Jijun Zhou Huibin Qin 《Journal of Electroceramics》2014,32(2-3):230-233
MnZn power ferrites with a composition of Mn0.681-xZn0.246Fe2.073CoxO4 were prepared by conventional ceramic technique. The samples were sintered in a computer-driven furnace at 1320 °C for 4 h. Then the influences of Co-substitution on the crystalline structure, microstructure and the magnetic properties of MnZn power ferrite were studied. It shows that Co-substitution has not changed the structure of MnZn ferrite, but improved the crystallization. With the increase of Co substitution content, Co2+ ions firstly replace Mn2+ ions and then replace Fe3+ ions. And at room temperature, the initial permeability increases with the increase of Co-substitution content. Co-substitution can also reduce the porosity and the power loss. In addition, the corresponding temperature of the minimum power loss shifts to a lower temperature. 相似文献
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The measurement of the iron loss in ferrites is important for developing high‐efficiency switching power supplies. The authors have proposed the dynamic magnetic loss parameter, λf, for evaluating the iron loss in ferrites. In previous studies, the parameter was assumed to be a constant value for an individual ferrite material and defined for one period of a small B–H loop. In this paper, assuming that λf is a function of the time derivative of the magnetic flux density, dB/dt, a novel measurement method of λf of a Ni‐Zn ferrite is proposed using rectangular wave voltage excitation and the Fourier expansion of the exciting current. In order to realize an iron loss measurement system with the rectangular wave voltage excitation, a high‐frequency FET inverter has been developed. The results of measuring λf show that it is uniquely determined by dB/dt regardless of the B–H loop size. The measured dB/dt characteristics of λf are applied to practical examples for switching power supplies and sinusoidal wave voltage excitations. Their experimental and computational results coincide and it is clarified that the measured dB/dt characteristics are effective and useful. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(1): 1–6, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20101 相似文献
4.
《International Journal of Circuit Theory and Applications》2017,45(10):1439-1446
This paper presents a cumulative current‐magnetizing method for magnetization of permanent magnet, aimed at alleviating the bulky capacitor problem of traditional capacitor‐discharged impulse magnetizers. The method employs circuit resonance to boost the output voltage. The resonant alternative current (ac) voltage is then directly discharged to the magnetizing coil without using any rectifier. The proposed resonant ac discharge repeats a number of times over several milliseconds. This allows the magnetizing current to increase incrementally until it reaches the peak that is sufficient to fully magnetize the permanent magnet. With this design, the energy for magnetization is accumulated by small steps, and each increment would require much lower energy. This results in smaller capacitors needed compared to traditional designs. To validate the effectiveness of the proposed scheme, several pieces of ferrite magnet without being pre‐magnetized were tested using the developed magnetizer. The test results support the feasibility and practicability of the scheme for potential applications. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
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应用电磁场微扰理论,参照IEE556标准建立铁磁共振线宽测量系统,用传输式谐振腔法设计新的波谐振腔体,可在33GHz下测试旋磁材料的铁磁共振线宽,并分析了测试误差,解决了目前毫米波六角材料的线宽测试问题。 相似文献
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Masakazu Michihira Mitsuo Ueda Tsuyoshi Funaki Zen‐Ichiro Kawasaki Kenji Matsu‐ura 《Electrical Engineering in Japan》2000,130(2):88-98
In recent years, the soft‐switching techniques have attracted attention for their peculiar advantages such as low switching loss, high power density, EMI/RFI noise reduction, and so on. The authors have previously reported on a quasi‐resonant dc–dc converter using new phase‐shift PWM control scheme. By using the proposed control scheme, circulating current is eliminated and ZVS (Zero Voltage Switching) is achieved with small commutating current. As a result, the conduction losses caused by their currents are substantially reduced. In this paper, the authors apply a proposed control scheme to a quasi‐resonant high‐frequency transformer link dc–ac converter. As a result, all switching devises in this dc–ac converter can achieve soft switching with small commutating current irrespective of inverter mode and rectifier mode. Its operating principle and unique features are described as compared with the symmetrical control scheme of dc–ac converter. Operating performance of this dc–ac converter in the steady state is illustrated by means of simulation results. © 1999 Scripta Technica, Electr Eng Jpn, 130(2): 88–98, 2000 相似文献
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Yoshifumi Ajishi Osamu Ishii Hiroshi Osada Kyoshiro Seki 《Electrical Engineering in Japan》1999,129(4):17-23
Up to now, only bulk materials and thick films were available for use as temperature-sensitive substances. However, due to the high heat capacity of these substances, their sensitivity is too low for the detection of minute temperature variations. General trends toward the miniaturization and weight reduction of electronic equipment necessitate development of thin films having magnetic properties. No technology for the preparation of temperature-sensitive magnetic thin films (TMF) has existed so far because of difficulties related to the adjustment of the mixture ratio of TMF materials composed of Fe, Mn, and Zn oxides. The authors investigated a method of fabrication of TMF by annealing of the film formed by the sputtering of a target consisting of temperature-sensitive ferrites with low Curie temperature. This method involves a two-step processing: depositing the metal components of temperature-sensitive ferrites on a substrate by sputtering and a high-temperature annealing treatment performed in a flow of argon gas in a tank containing oxygen. As a result, a ferrite thin film (thickness 1.5 μm) with spinel structure can be fabricated. The TMF characteristics closely reproduce parameters of the temperature-sensitive ferrites used in the target. The TMF so obtained also have an exceptional temperature dependence and a low heat capacity, thus providing for a prompt response to minute temperature variations of the order of 10–1 °C. Therefore, the TMF are expected to find use in such applications as pyromagnetic sensors, optimized artificial sensors, and biosensors. © 1999 Scripta Technica, Electr Eng Jpn, 129(4): 17–23, 1999 相似文献
9.
Charanjeet Singh S. Bindra-Narang Inderjeet Singh Hudiara K. Sudheendran K. C. James Raju 《Journal of Electroceramics》2011,27(3-4):120-125
The complex permittivity and complex permeability of synthesized M-type hexagonal ferrite powders, Ba0.5Sr0.5CoxRuxFe(12-2x)O19 (x?=?0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) are measured at X-Band. The experimental results conclude that Co2+ and Ru4+ ions substitution enhances electromagnetic properties, rendering the use of ferrite for lossy applications. The acceleration in hoping mechanism between Fe2+ and Fe3+ ions leads to dominance of ??? and ??? over ??? and ??? along entire frequency band. 相似文献
10.
The recent miniaturization and increased complexity of electrical devices have increased the influence of impurities on device performance, especially the influence of small conductive particles with a size on the order of micrometers. Therefore, the inspection of devices during the manufacturing process has become important. In this study, changes in the resonance properties of a microwave cavity were used to detect a metal particle. The decrease in the resonant frequency for a 100‐µm stainless steel sphere was about 0.1 MHz, which was less than 1 ppm of the resonant frequency used. This frequency change is too small to detect directly in the output of a particle detector. Transmission measurements (the scattering parameter S21) at a frequency that was a few megahertz higher than the resonant frequency where the S21 changes sharply were used to magnify signal changes resulting from the introduction of a small conductive particle. A resonant frequency of 13.3 GHz and a frequency 3 MHz higher were chosen for obtaining measurements in the present study. By applying a filtering technique, it was shown that the minimum detectable sphere size is around 50 µm. This sensitivity was experimentally shown to be uneven along the long axis of the cavity. The unevenness was related to the electrical field strength of the standing wave at the resonant frequency. For practical industrial inspection of devices, multiple frequencies should be employed in view of the present discussion. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(2): 61–67, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22490 相似文献
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Hideo Saotome Shun Kuwahara 《IEEJ Transactions on Electrical and Electronic Engineering》2007,2(5):556-560
Ferrite cores are used for power electronics circuits operating under excitation conditions of frequency ranging from hundreds of kilohertz to several tens of megahertz. Development of a mathematical model enabling the estimation of the power loss of ferrites in high‐frequency regions, contributes to the designing of power circuits. The power loss in high‐frequency regions consists of hysteresis and dynamic magnetic losses. Although hysteresis loss does not depend on the excitation frequency, the dynamic magnetic loss increases with increasing excitation frequency. The dynamic magnetic loss parameter, λf, has been introduced for identifying the power loss in high‐frequency regions. In this study, λf − dB/dt characteristics are experimentally obtained by a newly introduced hysteresis model that uses a normal distribution function. It is found that the λf − dB/dt characteristics do not depend on the size of B − H loops. The instantaneous power loss of a ferrite core in the high‐frequency region can be calculated using the λf − dB/dt characteristics. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. 相似文献
13.
M. Penchal Reddy W. Madhuri N. Ramamanohar Reddy K. V. Siva Kumar V. R. K. Murthy R. Ramakrishna Reddy 《Journal of Electroceramics》2012,28(1):1-9
The effect of zinc ion substitution for nickel on structural and magnetic properties of NiZn ferrites is reported. The spinel
ferrite system Ni1-xZnxFe2O4 with x = 0.2, 0.3, 0.4 and 0.5 was prepared by microwave sintering method. The uniaxially pressed samples were sintered at
various temperatures such as 900°C, 1000°C and 1100°C for 30 min. X-ray diffraction patterns of the samples indicate the formation
of single-phase cubic spinel structure. SEM micrographs show that grain size increases with increasing zinc content and sintering
temperature. The elemental composition of these ferrites was analyzed by EDS. Lattice constant increases with increase in
zinc content, obeying Vegard’s law. The effect of composition and sintering temperature on initial permeability as the function
of frequency and temperature was studied. The initial permeability of NiZn ferrite increases greatly with increasing Zn content
and sintering temperature. The dependence of initial permeability with respect to temperature shows the decrease in the Curie
point with increase in zinc content, is the normal behavior of ferrites. The relative loss factor (tand