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Magnetics, IEEE Transactions on

Issue 11 • Date Nov. 2010

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Displaying Results 1 - 25 of 25
  • [Front cover]

    Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Page(s): C2
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  • Table of contents

    Page(s): 3829 - 3830
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  • Increase of Coercivity and Composition Distribution in Fluoride-Diffused NdFeB Sintered Magnets Treated by Fluoride Solutions

    Page(s): 3831 - 3833
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB) |  | HTML iconHTML  

    Rare-earth and fluorine were diffused along grain boundaries in NdFeB sintered magnets during heat treatment after rare-earth fluoride liquid coating. In the case of Dy fluoride coating, the coercivity for NdFeB sintered magnets with a thickness of 1 mm after the diffusion was increased from 0.80 MA/m to 1.13 MA/m (41%) with remanence reduction of 0.6%. Segregations for Dy atoms near the grain boundaries and fluorine atoms at the grain boundary were found by TEM observations. The increase of coercivity per the weight of the rare-earth fluorides has a correlation with the anisotropy field of the RE2Fe14B (RE is rare-earth elements). Furthermore, the Dy quantity required for the observed increase of coercivity can be reduced to 1/3 compared to the previous NdFeB sintered magnets using the fluoride coating and diffusion process. View full abstract»

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  • Refinements in Anhysteretic Characterization and Permeability Modeling

    Page(s): 3834 - 3843
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    This paper sets forth several refinements in the anhysteretic characterization and permeability modeling of ferromagnetic and ferrimagnetic materials. The refinements are focused on reducing the engineering time required to carry out the characterization and to make the magnetization and permeability functions numerically robust. View full abstract»

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  • Identifying Hysteresis Losses in Magnetic Media

    Page(s): 3844 - 3847
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    A magnetic medium can have different hysteresis losses when subject to a rotating field. We discuss the pertinent parameters that determine these losses and a method of identifying them. We discuss the effect of particle interaction, and isotropic and anisotropic media. View full abstract»

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  • A Modified Formulation of the Volume Integral Equations Method for 3-D Magnetostatics

    Page(s): 3848 - 3859
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1595 KB) |  | HTML iconHTML  

    A magnetization-based formulation of the volume integral equations method for 3-D magnetostatics is discussed. The magnetization of each element is related, via the constitutive law of the material, to the average magnetic flux density within the element rather than to the value at the center as is usually done. This assumption leads to more accurate distribution of magnetization and allows a faster convergence of the solution. Moreover, it leads to more symmetric matrix of the coefficients and reduces the numerical instability due to looping patterns of magnetization, which is inherent to integral methods. The formulation is made effective by the use of a hybrid numerical and analytical approach, which allows for the fast and accurate calculation of the coefficients. The proposed model is validated and compared with the usual model both for saturable and linear material with high susceptibility. View full abstract»

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  • Analytical Design of Permanent Magnet Radial Couplings

    Page(s): 3860 - 3865
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (930 KB) |  | HTML iconHTML  

    This paper presents a three-dimensional analytical approach for computing the torque transmitted by synchronous radial couplings with radially polarized tile permanent magnets. An expression is given as a finite sum of elliptic functions, which has no underlying simplificating assumptions. Such an expression allows parametric studies and optimizations of coupling structures. It is applied first to the study of conventional radial couplings. Then, structures with “short pitch” magnets are considered and compared with conventional ones. Eventually, special designs are presented, as the ones dedicated to screwing applications, for instance, which require creating an asymmetrical torque. View full abstract»

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  • Magnetostatic Field Penetration into Multiple Annular Apertures

    Page(s): 3866 - 3869
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB) |  | HTML iconHTML  

    We investigated magnetostatic field penetration into multiple annular apertures in a thick conducting plane. We rigorously solved a magnetostatic boundary-value problem of multiple annular apertures using the Hankel transform, eigenfunction expansion, and superposition. We represented magnetic polarizability in a rapidly convergent series and computed it in terms of aperture geometry and incident angles to understand the magnetostatic field penetration. View full abstract»

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  • Analytical Modeling of Magnetic Field in Surface Mounted Permanent-Magnet Tubular Linear Machines

    Page(s): 3870 - 3884
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (689 KB) |  | HTML iconHTML  

    We present an exact 2-D analytical model for predicting the magnetic field in idealized structures of surface mounted permanent-magnet tubular linear machines that account for the stator slotting effect. The open-circuit and armature reaction magnetic field distributions are analytically derived and compared to finite-element analyses. The on-load magnetic field calculation is based on the superposition of the component fields due to permanent magnets and armature field reaction. Our model can be advantageously used for the analysis and design of a class of linear tubular machines. View full abstract»

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  • Impedance Calculation of a Bobbin Coil in a Conductive Tube With Eccentric Walls

    Page(s): 3885 - 3892
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (602 KB) |  | HTML iconHTML  

    The complex impedance of an air-cored coil in a conductive tube with eccentric inner and outer cylindrical surfaces is calculated. The analytic expressions for the induced fields and the impedance variation due to the eddy-current flow inside the tube wall are derived using a second-order potential approach. The addition theorem of Bessel functions is employed to perform the transition between the local coordinate systems that conform to the boundaries of the structure. Although the model can be used for any coil shape and orientation, we focus our study on the configuration of a bobbin coil with axis parallel to the axes of the tube surfaces, but not necessarily coinciding with either of them. The results of the presented analysis are verified by a finite-element-method (FEM) solution. View full abstract»

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  • Application of Shell Element Method to 3-D Finite-Element Computation of the Force on One Body in Contact With Others

    Page(s): 3893 - 3898
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (281 KB) |  | HTML iconHTML  

    A general formulation of nodal virtual work force computation for three-dimensional finite-element analysis is presented. For problems with objects touching each other, a special shell element is used and its implementation methodology is presented. It is noted that additional surface integration is needed when volume integration changes to surface integration. Numerical results are compared and validated using their corresponding analytical solutions. View full abstract»

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  • Inter-Track Interference Mitigation for Bit-Patterned Magnetic Recording

    Page(s): 3899 - 3908
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1568 KB) |  | HTML iconHTML  

    In bit-patterned magnetic recording (BPMR), inter-track interference (ITI) becomes a major impairment due to the small track pitch. One way to mitigate the ITI is to equalize the read channel to a two dimensional (2D) partial-response (PR) target. However, we find that the channel detection on the center track cannot take advantage of the 2D target without good estimation of the data on the sidetracks. Therefore, we propose a multi-track detection technique, where the detection on the center track is aided by the information obtained from the detection of the sidetracks. This technique works with any equalizer capable of equalizing the channel to a 2D target. We apply this method to joint-track equalized and 2D equalized BPMR channels. Our simulation results show that the proposed technique provides a significant performance improvement. View full abstract»

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  • Magnet Segmentation for Commutation Torque Ripple Reduction in a Brushless DC Motor Drive

    Page(s): 3909 - 3919
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1970 KB) |  | HTML iconHTML  

    We present a new brushless DC motor (BDCM) design based on a model elaborated from a finite-element method associated to controller circuit equations represented in a Matlab-Simulink environment. The simulation model takes into account the commutation period effect and is based on the true system design implementation. The simulation results show that there is an effect between this commutation (a major source of torque ripple) and appropriate permanent-magnet segmentation design, particularly when the angle of advance between the back-electromotive force (EMF) and the current is adequately set. Current control strategies are found limited and may require complex implementation. Concentration on back-EMF and ultimately on permanent-magnet design are interesting aspects of torque ripple as well as rotor losses over wide speed range. After validation of the simulation model using an experimental kit set for the purpose, we perform an optimization procedure based on an indirect coupled field circuit approach that has led to an optimal design for which the torque ripple is minimal (less than 6%). An analytical design provided support for the study. The new design shows a lower cogging torque. Overall, the new design helps to provide a low-cost BDCM system for many applications using a simple square wave circuit controller. View full abstract»

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  • Design of a Flux-Shunt Permanent Magnet DC Motor With Hybrid Magnetomotive Force and Anti-Demagnetization Property

    Page(s): 3920 - 3927
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1063 KB) |  | HTML iconHTML  

    Rare-earth magnets of high-energy products have been widely used to improve the efficiency, as well as the power and torque per unit weight, of permanent-magnet machines. In addition to the drawbacks of limited resources and high prices, the rare-earth magnet may risk irreversible demagnetization during field weakening or malfunctioning in machine operation. To solve this problem, we investigate the antidemagnetization property due to the flux shunt mechanism and hybrid magnetomotive force in a permanent-magnet direct-current motor. The hybrid magnetomotive force is provided by low-grade permanent magnets and additional field windings, between which are ferromagnetic media that shunt the adjustable magnetic flux in the machine. We performed an optimal machine design and verified it with a finite-element analysis. We fabricated a prototype, and the experimental results show that machine efficiency and torque are increased by increasing the current of the field winding and that machine speed can be extended by reducing the field current. Finally, we proved that the antidemagnetization mechanism is effective by investigating the reduction of back electromagnetic force after demagnetization. View full abstract»

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  • A Novel Air-Gap Profile of Single-Phase Permanent-Magnet Brushless DC Motor for Starting Torque Improvement and Cogging Torque Reduction

    Page(s): 3928 - 3932
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (421 KB) |  | HTML iconHTML  

    We propose a new air-gap profile for single-phase permanent-magnet brushless dc (SP PM BLDC) motor to improve starting torque and to reduce cogging torque. We calculate starting torque and cogging torque using finite-element (FE) analysis. We perform a parametric analysis to study the effect of variation of proposed profile dimensions on cogging torque and starting torque. More than 70% improvement in starting torque and considerable reduction in magnitude of cogging torque is achieved compared to existing tapered air-gap profiles. View full abstract»

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  • Axial Flux and Eddy-Current Loss in Active Region of a Large-Sized Squirrel-Cage Induction Motor

    Page(s): 3933 - 3938
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (707 KB) |  | HTML iconHTML  

    This paper analyzes the axial flux and the corresponding eddy currents inside the laminated cores of a large-sized squirrel-cage induction motor running under the steady-state operation in order for possible optimum design of large-sized induction motors used in industry. The analysis was based on a complete 3-D numerical model. In the model, the laminated cores were replaced by anisotropic solid bodies, and the eddy currents inside the end portion of the stator frame were modeled with the standard impedance boundary condition. A time-harmonic finite-element analysis based on the magnetic vector potential-electric scalar potential formulation was performed. According to the results, under steady-state no-load, the axial flux, caused mainly by the air-gap fringing flux and the end-winding leakage flux, appears in the end portion of the cores, and decays rapidly toward the middle of the cores. The corresponding planar eddy currents inside the laminations of the stator core are mainly concentrated near the edges of the stator teeth. The eddy-current loss is small, but the distribution of the loss over the laminations is definitely non-uniform. View full abstract»

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  • Optimum Design of Single-Sided Linear Induction Motors for Improved Motor Performance

    Page(s): 3939 - 3947
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1841 KB) |  | HTML iconHTML  

    Linear induction motors (LIMs) are the best solution to the problem of producing linear motion directly, but the low efficiency, low power factor, and longitudinal end effect (LEE) are their major problems. These problems become more baneful in high-power and high-speed applications. For example, in the transport industry, they lead to high energy consumption, high input current that occupies transmission line capacity, and phase unbalance. Thus, it is necessary to overcome these problems; furthermore, the decrease in motor weight results in lower cost and better performance of linear induction motors. In this paper, first we present an accurate equivalent circuit model (ECM). Then, we introduce a new factor, Klee, which can illustrate the end effect intensity in the LIM. At the next stage, we investigate the influence of motor design parameters on the efficiency, power factor, and end effect intensity. Then we develop several different muliobjective functions, which will be used to improve efficiency, power factor, end effect intensity, and motor weight. This procedure will be done by analytic method and by using the particle swarm optimization technique. Results will show the accuracy of the equivalent circuit model and the improvement of objective functions at the end of the optimization procedure. Two-dimensional finite-element analysis evaluates the results from the ECM. View full abstract»

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  • A Simple 2-D Finite-Element Geometry for Analyzing Surface-Mounted Synchronous Machines With Skewed Rotor Magnets

    Page(s): 3948 - 3954
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (813 KB) |  | HTML iconHTML  

    We present a new 2-D FEM-based system for analyzing permanent-magnet surface-mounted synchronous machines with skewed rotor magnets. The system is based on generating a geometric equivalent non-skewed permanent-magnet distribution that accounts for the skewed distribution of the practical rotor. An appealing feature of the proposed system is that it can be easily performed in any 2-D electromagnetic FEM package by performing a simple change in the geometry of the magnets. Attributes of the method presented here include simplicity, high accuracy, low computational burden, and high speed compared to 3-D and 2-D multislice FEM analysis. Experimental results with both healthy and faulty machines corroborate the effectiveness of the model proposed in this work. View full abstract»

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  • Accounting for the Armature Magnetic Reaction and Saturation Effects in the Reluctance Model of a New Concept of Claw-Pole Alternator

    Page(s): 3955 - 3961
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (653 KB) |  | HTML iconHTML  

    We describe the development and the experimental validation of a magnetic equivalent circuit (MEC) of a new claw pole alternator where the DC-excitation winding is located in the stator (CPAES), rather than in the rotor in conventional claw pole alternator. Thus, we discarded the brush-ring system and achieved crucial cost, compactness, and reliability benefits. The proposed MEC treats both no-load and loaded armature operations. It also accounts for the saturation of the magnetic circuit. We numerically solve the established MEC using the Newton-Raphson algorithm. We validated the established MEC by considering experimental tests carried out on a prototype of the CPAES. We found that the results yielded by the proposed MEC and those given by the experimental tests are in good agreement. View full abstract»

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  • Scitopia.org [advertisement]

    Page(s): 3962
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  • IEEE Magnetics Letters

    Page(s): 3963
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  • The IEEE Digital Library [advertisement]

    Page(s): 3964
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  • IEEE Magnetics Society Information

    Page(s): C3
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  • IEEE Transactions on Magnetics institutional listings

    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