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Magnetics, IEEE Transactions on

Issue 6  Part 2 • Date June 2011

 This issue contains several parts.Go to:  Part 1 

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

    Publication Year: 2011 , Page(s): C1
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  • IEEE Transactions on Magnetics publication information

    Publication Year: 2011 , Page(s): C2
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  • Table of contents

    Publication Year: 2011 , Page(s): 1645 - 1646
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  • Comparative Study of Biomimetic Iron Oxides Synthesized Using Microwave Induced and Conventional Method

    Publication Year: 2011 , Page(s): 1647 - 1652
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (477 KB) |  | HTML iconHTML  

    Aqueous ferrofluids having high steric stability were prepared biomimetically by chemical co-precipitation of iron salts in poly (vinyl) alcohol. Both conventional and microwave heating modes were used for the synthesis of the fluids; the bottleneck of conventional heating being low saturation magnetization. The uniqueness of this work lies in the fact that for the same initial constituents, microwave irradiation enhances saturation magnetization without compensating stability. Superparamagnetic iron oxide nanoparticles with a narrow size distribution were formed, and structural investigations of the dried fluid revealed that microwave irradiation increased the polydispersity and the average particle size of the nanocomposites which led to a loss of long-range ordering. X-ray diffraction patterns of the synthesized ferrofluids showed an increase in crystallinity for the microwave irradiated sample. All these structural rearrangements affected the saturation magnetization (Ms) which more than doubled from 12.97 to 27.07 kAm-1 with microwave irradiation. View full abstract»

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  • Transverse Ferromagnetic Resonance of Heisenberg Ferromagnets With Exchange Anisotropy

    Publication Year: 2011 , Page(s): 1653 - 1657
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (179 KB) |  | HTML iconHTML  

    The effect of oscillating magnetic field on the anisotropic susceptibility of a spin S = 1/2 anisotropic three-dimensional Heisenberg ferromagnet, is studied by the double-time Green's function method within Tyablikov approximation. The results show that the magnetic resonant frequencies directly and sensitively depend on the exchange anisotropic constant (α), and the directions of applied magnetic field. In the case of transverse oscillating field, the transverse susceptibilities exhibit strong resonant effect, and the positions of resonant frequency are sensitive and change monotonically to α. However, in the case of longitudinal oscillating field, the longitudinal susceptibilities are rather flat and display no resonant effect. Therefore, transverse ferromagnetic resonance is a precise technique to measure the magnitude of α, and this conclusion is very useful in the alloy multilayer application. View full abstract»

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  • Multiobjective Design Optimization of Five-Phase Halbach Array Permanent-Magnet Machine

    Publication Year: 2011 , Page(s): 1658 - 1666
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1159 KB) |  | HTML iconHTML  

    The multiphase Halbach array permanent-magnet machines are very good candidates for special applications such as marine and military applications due to the fault tolerance capability, high output torque, and high acceleration features. In this paper, an optimal design of a five-phase Halbach permanent-magnet machine for high efficiency, high torque, and high acceleration is investigated. A Genetic Algorithm method is used to optimize the design variables based on the analytical model of the motor, which is dependent only on motor geometrical and materials data. In this method, first the main machine design objectives such as efficiency, acceleration, and output power are optimized separately and then a multiobjective optimization considering all objectives simultaneously is given. The detailed finite-element analysis results are carried out to evaluate and verify the performance of the designed machine. View full abstract»

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  • A Novel Multimodal Optimization Algorithm Applied to Electromagnetic Optimization

    Publication Year: 2011 , Page(s): 1667 - 1673
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1020 KB) |  | HTML iconHTML  

    The selection of optimum parameters in electromagnetic design usually requires optimization of multimodal, nonlinear functions. This leads to extensive calculations which pose a huge inconvenience in the design process. This paper proposes a novel algorithm for dealing efficiently with this issue. The proposed algorithm interprets the problem as an unexplored terrain for climbing. Through the use of contour line concept coupled with Kriging, the algorithm finds out all the peaks in the problem domain with as few function calls as possible. The efficiency of the proposed algorithm is demonstrated by application to conventional test functions. In this paper, the simulation results show that skewing does not necessarily reduce the cogging torque but may cause it to increase for certain pole-arc to pole-pitch ratio. The developed algorithm is applied to the magnet shape optimization of an axial flux permanent magnet synchronous machine and the cogging torque was reduced to 79.8% of the initial one. View full abstract»

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  • Self-Biased Microstrip Junction Circulator Based on Barium Ferrite Thin Films for Monolithic Microwave Integrated Circuits

    Publication Year: 2011 , Page(s): 1674 - 1677
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (964 KB) |  | HTML iconHTML  

    Barium hexaferrite thin films with thickness of 8 μm had been deposited on a sapphire substrate by radio-frequency magnetron sputtering. The results show that the grain size is about 2 μm in diameter. The coercivity is about 2.2 kOe and the saturation magnetization is about 4000 Gs with remanence ratio of 0.58. Based on the sputtered thin films, a self-biased microstrip junction circulator had been developed. The measured S-parameters indicate that a nonreciprocal effect greater than 10 dB occurs at about 26 GHz. The maximum isolation is 44 dB and the minimum insertion loss is 27 dB. The origins of the large insertion losses have been discussed. View full abstract»

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  • Design and Fabrication of On-Chip Coupled Inductors Integrated With Magnetic Material for Voltage Regulators

    Publication Year: 2011 , Page(s): 1678 - 1686
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1073 KB) |  | HTML iconHTML  

    On-chip strip-line coupled inductors integrated with magnetic material are a promising technology option to enable on-chip voltage regulators for improving power management in microelectronics. We report on design methodologies where several examples of parameter tradeoffs are presented. When considered with practical integration constraints, these result in an optimized structure. Strip-line inductors integrated with Ni80Fe20 were then fabricated, electrically characterized, and compared to models. Electrical characterization included frequency dependent measurements of effective self and mutual inductance, effective resistance, coupling coefficient, and saturation effects. View full abstract»

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  • Improving Magnet Designs With High and Low Field Regions

    Publication Year: 2011 , Page(s): 1687 - 1692
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB) |  | HTML iconHTML  

    A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays have to deliver high field regions in close proximity to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example, these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material used by 42% while increasing the difference in flux density between a high and a low field region by 45%. View full abstract»

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  • An Improved Subdomain Model for Predicting Magnetic Field of Surface-Mounted Permanent Magnet Machines Accounting for Tooth-Tips

    Publication Year: 2011 , Page(s): 1693 - 1704
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1147 KB) |  | HTML iconHTML  

    The paper developed an improved analytical subdomain model for predicting the open-circuit magnetic field in surface-mounted permanent magnet machines accounting for the tooth-tips in the slots. The whole field domain is divided into four types of simple subdomains, viz. magnets, air-gap, slot openings, and slots. The analytical expression of each subdomain is derived and the field solution is obtained by applying the boundary conditions and interface conditions between subdomains. Compared with the conventional subdomain models, the subdomain model accounting for tooth-tips can accurately predict the flux density inside the slots. Based on the developed field model, the cogging torque is computed by the Maxwell stress tensor. The finite element analysis is carried out to validate the analytical model. It shows that the developed subdomain model accounting for tooth-tips is more accurate, especially for the machines having larger slot opening width compared with tooth-tip height. View full abstract»

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  • Coding and Detection for Rectangular-Grain TDMR Models

    Publication Year: 2011 , Page(s): 1705 - 1711
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    This paper studies the performance of a serial turbo code on two simplified rectangular-grain models of recording media for two-dimensional (2-D) magnetic recording at a density of more than 0.5 bits/grain. We derive one-dimensional (1-D) and 2-D rectangular-grain media models and from these present finite-state-machine (FSM) representations. From the FSM for the 1-D model we computed achievable information rates assuming independent and uniformly distributed (i.u.d.) binary inputs. From the (approximate) FSM for the 2-D model, we present a detector. We then present a serial turbo code architecture with constituent convolutional codes that is capable of achieving 80% of i.u.d. capacity for the 1-D model and 65% of the average of published upper and lower bounds on capacity for the 2-D model. We also present schemes which combine the advantages of an (inner) repetition code and an (outer) serial turbo code. One such scheme cleverly arranges the three bits in each three-fold repetition into the shape of an “L”. This obviates the need for a sequence detector and converts the 2-D channel model into an equivalent binary symmetric channel. View full abstract»

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  • Practical Implementation of the Bridge Configured Winding for Producing Controllable Transverse Forces in Electrical Machines

    Publication Year: 2011 , Page(s): 1712 - 1718
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (500 KB) |  | HTML iconHTML  

    It is now evident that the value of endowing rotating machines with the capability to produce transverse forces in addition to their normal torque-producing function can be extremely high. The bridge configured winding is a cost-saving connection scheme for electrical machines to exploit transverse magnetic forces on the rotors. The winding scheme retains the machine's three-phase terminals such that ordinary motor inverters can be employed for the normal torque-producing function while providing separate terminals for transverse force action. This paper describes the practical implementation of such a winding connection in a conventional electric machine and demonstrates that controllable transverse forces can be produced. View full abstract»

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  • Analysis of the Mutual Inductance in Current Transformers Taking Primary Conductors Eccentricity Into Account

    Publication Year: 2011 , Page(s): 1719 - 1725
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (429 KB) |  | HTML iconHTML  

    In this work a current transformer (CT) with toroidal core is analyzed from the viewpoint of the eccentricity of the primary circuit where one conductor goes through the core's window and the other is outside the core. The research is focused on the influence of the position of the primary circuit conductors on the evaluation of the mutual inductance between the primary circuit and the secondary winding-an influential factor on the CT's amplitude error. Purely analytical results and closed-form expressions for the mutual inductance are obtained when the core is made of a nonmagnetic material. A finite-element method is also utilized for the numerical computation of the mutual inductance, for nonmagnetic and ferromagnetic cores. Results are cross-validated using both methods. Results are presented and discussed taking into account the system geometry and the number of turns of the secondary winding. This novel contribution shows that the response of nonmagnetic-core current transformers can be significantly affected by the positional eccentricity of the primary circuit, especially when the secondary winding does not possess a large number of turns. View full abstract»

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  • Shape Optimization of Coils and Cooling Ducts in Dry-Type Transformers Using Computational Fluid Dynamics and Genetic Algorithm

    Publication Year: 2011 , Page(s): 1726 - 1731
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB) |  | HTML iconHTML  

    In this paper, shapes of cooling ducts in dry-type transformers are optimized using computational fluid dynamics (CFD) and the Genetic Algorithm (GA). The GA is used to optimize diameters of both ducts and coils. Constraints in the optimization process are the minimum distance between the high-voltage (HV) and the low-voltage (LV) windings and the outer diameter of coils. Since the investigated transformer is a special unit, two objective functions (OF) were applied to minimize the average and the maximum temperature of the windings, and thus the coil power losses. The OF value is determined using a CFD model that accounts for all three heat transfer modes. The local total heat fluxes are specified on the model external boundaries. The thermal properties of the coils and core are treated as anisotropic and temperature-dependent quantities, while the power losses are treated as heat sources and are computed based on the coupled CFD-EMAG model. Both coil properties and losses vary with each generated coil configuration. The results show that the nonuniform positioning of the wires and air ducts can significantly improve the heat dissipation. Consequently, the coil losses are substantially reduced. View full abstract»

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  • Torque Analysis With Saturation Effects for Non-Salient Single-Phase Permanent-Magnet Machines

    Publication Year: 2011 , Page(s): 1732 - 1738
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (462 KB) |  | HTML iconHTML  

    The effects of saturation on torque production for non-salient, single-phase, permanent-magnet machines are studied in this paper. An analytical torque equation is proposed to predict the instantaneous torque with saturation effects. Compared to the existing methods, it is computationally faster and easier to calculate the torque using the analytical equation proposed. It can also handle arbitrary armature current waveforms and arbitrary flux linkage waveforms produced by the rotor permanent magnets. The results obtained by using the proposed torque equation are validated using finite-element results, and experimental results obtained on a prototype single-phase permanent-magnet machine. View full abstract»

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  • Slotless Permanent-Magnet Machines: General Analytical Magnetic Field Calculation

    Publication Year: 2011 , Page(s): 1739 - 1752
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB) |  | HTML iconHTML  

    This paper presents a general analytical model for predicting the magnetic field of slotless permanent-magnet machines. The model takes into account the effect of eddy currents in conductive regions and notably in conductive permanent magnets without neglecting their remanent field. The modeling of this effect is important for the design of very high speed slotless permanent-magnet machines, as the power losses are linked with the frequency of the field. The model takes into account any number of layers. It implies that, for one, the fields can easily be calculated in a design including a permanent magnet and a conductive retaining sleeve. The model is applicable both to internal rotor and external rotor permanent-magnet machines. The effect of the relative permeability and of the conductivity of the permanent magnet or of the yoke on the magnetic fields is also taken into account. Any magnetization can be taken into account, in particular a Halbach type permanent magnet, or a radially magnetized permanent magnet can be considered. View full abstract»

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  • Modeling of Air Core Permanent-Magnet Linear Motors With a Simplified Nonlinear Magnetic Analysis

    Publication Year: 2011 , Page(s): 1753 - 1762
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1339 KB) |  | HTML iconHTML  

    This paper presents a new analysis method for air core permanent-magnet synchronous linear motor design optimization problems with a large search space. The aim is to reduce the total computational time by replacing most of the finite-element analysis (FEA) steps with an analytical model of the motor consisting of nonlinear equivalent magnetic circuit and flux density distribution models. A small number of FEA steps are used to determine some parameters of the analytical model. The result of the proposed method is compared with results of both a pure FEA design and experiments on a real motor. The proposed method has similar performance to FEA, although computationally it is at least two orders of magnitude faster. View full abstract»

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  • Analytical Magnetic Field Distribution of Slotless Brushless Machines With Inset Permanent Magnets

    Publication Year: 2011 , Page(s): 1763 - 1774
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1845 KB) |  | HTML iconHTML  

    An analytical open-circuit magnetic field distribution for slotless brushless machines with inset permanent magnets is presented. Three different magnetization patterns (radial, parallel, and Halbach) have been considered and their results compared with each other. The induced back-electromotive force (EMF) is also presented for each magnetization pattern. The effects of iron inter-pole on the magnetic flux density and back-EMF have been studied. To verify the model, the results have been compared with those obtained from finite element analyses (FEA). View full abstract»

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  • Stator Inductance Fluctuation of Induction Motor as an Eccentricity Fault Index

    Publication Year: 2011 , Page(s): 1775 - 1785
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    A new index is introduced for eccentricity fault diagnosis in three-phase squirrel-cage induction motors. Basically, some physical quantities of the motors structure such as air gap length influence this index, while other operational factors including motor supply, control type, load level, and its fluctuation cannot affect the proposed index. The influence of various eccentricity faults upon this index is investigated and shows the segregation ability of different eccentricity types by the index. It is indicated that the change of load, speed, and saturation level can slightly change the index value. Experimental results confirm the simulation results. View full abstract»

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  • Improvement of Convergence Characteristics for Steady-State Analysis of Motors With Simplified Singularity Decomposition-Explicit Error Correction Method*

    Publication Year: 2011 , Page(s): 1786 - 1789
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1131 KB) |  | HTML iconHTML  

    In order to improve the convergence for steady-state analysis, the simplified singularity decomposition-explicit error correction (SD-EEC) method is developed. This paper proposes techniques to apply the simplified SD-EEC method to an interior permanent magnet (IPM) motor and to an induction motor. The usefulness of the techniques is verified through the applications to an interior permanent magnet (IPM) motor and an induction motor. View full abstract»

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  • Why we joined ... [advertisement]

    Publication Year: 2011 , Page(s): 1790
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    Freely Available from IEEE
  • 2011 IEEE membership form

    Publication Year: 2011 , Page(s): 1791 - 1792
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  • IEEE Magnetics Society Information

    Publication Year: 2011 , Page(s): C3
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  • IEEE Transactions on Magnetics institutional listings

    Publication Year: 2011 , 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