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Magnetics, IEEE Transactions on

Issue 2 • Date Feb. 2008

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Displaying Results 1 - 16 of 16
  • [Front cover]

    Publication Year: 2008 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2008 , Page(s): C2
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  • Table of contents

    Publication Year: 2008 , Page(s): 237
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  • Influence of Interface Roughness, Film Texture, and Magnetic Anisotropy on Exchange Bias in [{\hbox {Pt/Co}}]_{3}/{\hbox {IrMn}} and {\hbox {IrMn}}/[{\hbox {Co/Pt}}]_{3} Multilayers

    Publication Year: 2008 , Page(s): 238 - 245
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1166 KB) |  | HTML iconHTML  

    Co/Pt multilayers can exhibit considerable exchange bias along the film normal when grown onto or covered by an antiferromagnetic IrMn layer. The magnitude of the bias effect depends strongly on the selection of the buffer layers and is largest for Co/Pt multilayers with small perpendicular anisotropy. This counterintuitive result is explained by opposite dependencies of exchange bias and magnetic anisotropy on the degree of film texture and grain size. Interface roughness also influences the perpendicular exchange bias field. The largest biases are measured on smooth films. Interlayer mixing during post-deposition annealing procedures decreases the exchange bias field of IrMn-capped Co/Pt multilayers. View full abstract»

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  • The Effect of DC Bias Conditions on Ferrite Core Losses

    Publication Year: 2008 , Page(s): 246 - 252
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    In switched-mode power supplies - the predominant type of power converter in contemporary electronic equipment - ferrite magnetic components under dc bias conditions are typically large and have relatively high losses. The nature of these losses is not widely understood, and research in this area has been hampered by the difficulty of obtaining accurate core loss measurements. This paper reviews previous studies on the nature of core losses under dc bias, and presents new results, measured by a technique that has not previously been utilized for the measurement of core losses under dc bias conditions. The results show that ferrite core losses increase significantly with an increasing dc bias, and highlight the need for further research over a wider range of conditions to fully characterize the phenomenon. View full abstract»

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  • A 3-D Magnetic Charge Finite-Element Model of an Electrodynamic Wheel

    Publication Year: 2008 , Page(s): 253 - 265
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1885 KB) |  | HTML iconHTML  

    When a magnetic rotor is both rotated and translationally moved above a conductive, nonmagnetic, guideway eddy currents are induced that can simultaneously create lift, thrust, and lateral forces. In order to model these forces, a 3D finite-element model with a magnetic charge boundary has been created. The modeling of the rotational motion of magnets by using a fictitious complex magnetic charge boundary enables fast and accurate steady-state techniques to be used. The conductive regions have been modeled using the magnetic vector potential and nonconducting with the magnetic scalar potential. The steady-state model has been validated by comparing it with a Magsoft Flux 3D transient model (without translational velocity) and with experimental results. The 3D model is also compared with a previously presented 2D steady-state complex current sheet model. View full abstract»

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  • Design Optimization of a Low-Speed Single-Sided Linear Induction Motor for Improved Efficiency and Power Factor

    Publication Year: 2008 , Page(s): 266 - 272
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1127 KB) |  | HTML iconHTML  

    Although linear electrical motors (LMs) are increasingly used in industry to develop linear motion, they suffer from two major drawbacks: low efficiency and low power factor. These drawbacks cause high energy consumption and a rise in input current, and occupy transmission line capacity. We present a multiobjective optimization method to improve both efficiency and power factor, simultaneously. Our method uses an analytical model of the machine to calculate the efficiency and power factor. It allows us to investigate the effects of various motor specifications on the efficiency and the power factor. Motor parameters and dimensions can then be optimized by using a genetic algorithm in an appropriate objective function. The results show an enhancement in motor performance. We have used 2-D and 3-D time-stepping finite-element methods to evaluate the analytical results. A comparison of results validates our optimization method. View full abstract»

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  • Power Transformers Internal Insulation Design Improvements Using Electric Field Analysis Through Finite-Element Methods

    Publication Year: 2008 , Page(s): 273 - 278
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (606 KB) |  | HTML iconHTML  

    Understanding the potential and electric field distribution in the insulation system of a transformer during transients is vital to its construction. Therefore, we have developed a method for electric field analysis inside a power transformer. The method consists of the following steps. (1) A lumped parameter equivalent model is constructed by dividing transformer windings into several blocks. (2) The electric circuit parameters of this model are calculated. (3) Employing the results of the transformer transient model analysis as boundary conditions, a 2-D asymmetrical electric field finite-element analysis is performed to determine electric fields through the windings. The method has been examined employing power frequency and impulse voltages. We have also demonstrated successful application of the method to a transformer and have verified the computed results by comparison with measured results. View full abstract»

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  • Measurement and Modeling of Rotational Core Losses of Soft Magnetic Materials Used in Electrical Machines: A Review

    Publication Year: 2008 , Page(s): 279 - 291
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    In many situations, for example, in the cores of a rotating electrical machine and the T-joints of multiphase transformers, the magnetic flux varies with time in terms of both magnitude and direction, i.e., the local flux density vector rotates with varying magnitude and varying speed. Therefore, it is important that the magnetic properties of the core materials under various rotational magnetizations be properly investigated, modeled, and applied in the design and analysis of electromagnetic devices with rotational flux. Drawing from the huge amount of papers published by various researchers in the past century, this paper presents an extensive survey on the measurement and modeling of rotational core losses of soft magnetic materials used in electrical machines, particularly from the view of practical engineering application. The paper aims to provide a broad picture of the historical development of measuring techniques, measuring apparatus, and practical models of rotational core losses. View full abstract»

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  • Magnetic Bearing Configurations: Theoretical and Experimental Studies

    Publication Year: 2008 , Page(s): 292 - 300
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (829 KB) |  | HTML iconHTML  

    A radial magnetic bearing, consisting of two permanent magnets, is an attractive choice because of its zero wear, negligible friction, and low cost, but it suffers from low load capacity, low radial stiffness, lack of damping, and high axial instability. To enhance the radial load and radial stiffness, and reduce the axial thrust, we have made a theoretical and experimental study of various radial configurations, including hydrodynamic lubrication to improve dynamic performance of the magnetic bearing. We developed an experimental setup to investigate the performance of bearing configurations under different operating conditions. The motion of a rotating shaft is mapped by two displacement sensors with a data acquisition system and personal computer. The first critical speed of each configuration is determined experimentally and verified through frequency analysis. We present a polar plot of displacement data. View full abstract»

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  • Two-Level Response and Parameter Mapping Optimization for Magnetic Shielding

    Publication Year: 2008 , Page(s): 301 - 308
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    We present a new technique for reducing computation time of numerical solutions to optimal design problems. We incorporate in the optimization procedure a coarse model. Our technique, the two-level response and parameter mapping (RPM) algorithm, is based on space mapping and manifold mapping. Space mapping (SM) performs a mapping between the parameter spaces of the coarse and fine models, while manifold mapping (MM) makes a mapping between the response spaces of the coarse and fine models through the use of response correction. Here, we use and compare the three two-level optimization procedures, SM, MM, and RPM, for the optimization of passive and active shields in induction heating. The results demonstrate accurate and time-efficient optimization of magnetic shields by the RPM algorithm. View full abstract»

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  • Fly Height Measurement Based on Phase Comparison Michelson Interferometry Using Low-Coherence Light Source

    Publication Year: 2008 , Page(s): 309 - 314
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1015 KB) |  | HTML iconHTML  

    We present a method for measuring head fly height in hard disk drives using phase comparison Michelson interferometry (PCMI), which compares the phases of two interference fringe patterns formed respectively on the inner surface of a glass disk and the air-bearing surface of a fly head slider through the glass disk. To suppress interference noise and further enhance measurement accuracy, we adopted a low-coherence light source as an illumination source to replace a high-coherence laser. The captured fringe images enabled us to extract ridge lines much more accurately than with a laser. We compared our measurements in the sub-10 nm spacing range with calculations and found excellent agreement. View full abstract»

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  • Implementation-Friendly Constraint for Adaptive Finite Impulse Response Filters for Equalization

    Publication Year: 2008 , Page(s): 315 - 319
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    In read channels in magnetic recording systems, a finite impulse response (FIR) filter is often used as an equalizer, and the filter coefficients are adapted via a least mean squares (LMS) algorithm. This equalizer adaptation loop can interfere with the timing recovery (TR) loop and the automatic gain control (AGC) loop that are also present in such channels. In a previous paper by L. Du et al., a linear constraint is proposed for the LMS loop so that it is decoupled from the TR and the AGC loops. In this paper, we generalize that constraint, and propose a new constraint that offers the advantage of easier implementation. View full abstract»

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    Publication Year: 2008 , Page(s): 320
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  • IEEE Magnetics Society Information

    Publication Year: 2008 , Page(s): C3
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  • IEEE Transactions on Magnetics institutional listings

    Publication Year: 2008 , Page(s): C4
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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology