Showing papers in "IEEE Transactions on Magnetics in 1992"
TL;DR: In this article, various model parameters needed to describe hysteresis on the basis of the Jiles-Atherton theory can be calculated from experimental measurements of the coercivity, remanence, saturation magnetization, initial anhysteretic susceptibility, initial normal susceptibility, and maximum differential susceptibility.
Abstract: The authors describe how the various model parameters needed to describe hysteresis on the basis of the Jiles-Atherton theory can be calculated from experimental measurements of the coercivity, remanence, saturation magnetization, initial anhysteretic susceptibility, initial normal susceptibility, and maximum differential susceptibility. The determination of hysteresis parameters based on this limited set of magnetic properties is of the most practical use since these are the properties of magnetic materials that are most likely to be available. >
581 citations
TL;DR: In this article, the magnitude of the induced voltage between both ends of the a-wire is decided by a differential permeability regarding circumferential flux change which is considered to occur principally in the outer shell of a-wires.
Abstract: Circumferential magnetic properties of amorphous magnetic wires (a-wires, for short) with three kinds of compositions (FeSiB, CoSiB, and FeCoSiB) and diameters of 120 mu m and 50 mu m are investigated applying an AC current using a BH hysteresis tracer. The magnitude of the induced voltage between both ends of the a-wire is decided by a differential permeability regarding circumferential flux change which is considered to occur principally in the outer shell of a-wires. A sensitive magneto-inductive (MI) effect is found in a-wires, in which the value of the inductance of a zero-magnetostrictive a-wire of 5 mm length changes up to about 75% for an external field of 0.8 kA/m (10 Oe). This MI effect is shown to be applicable to small magnetic heads and a cordless data tablet. >
370 citations
TL;DR: In this paper, the requirements for 10 Gb/in/sup 2/media were examined, taking guidance from a recording model and known trends in high-performance media, and a read/write model was applied to examine the media properties required for this density in a practical drive application.
Abstract: The authors examine the requirements for 10 Gb/in/sup 2/ media, taking guidance from a recording model and known trends in high-performance media. They apply a read/write model to examining the media properties required for this density in a practical drive application. They find that the required magnetic and microstructural properties with the concomitant noise and supermagnetic limits demand significant improvements over existing media, to the extent that revolutionary improvements will likely be required. >
268 citations
TL;DR: A method for predicting the cogging torque in radial-field permanent magnet brushless motors, based on the analytical calculation of the airgap field distribution and the net lateral force acting on the stator teeth is developed and validated.
Abstract: A method for predicting the cogging torque in radial-field permanent magnet brushless motors, based on the analytical calculation of the airgap field distribution and the net lateral force acting on the stator teeth, is developed and validated. The technique is applicable to both internal and external rotor motor topologies, modeled in a cylindrical coordinate system. It can also be applied to variants of the basic motor topologies, such as those with shifted magnets (i.e. spaced unsymmetrically) or unevenly distributed stator slots, and thus it can enable design features aimed at reducing the level of cogging torque to be evaluated. Based on the proposed analytical model, the effects of varying the leading design parameters on the cogging torque can be investigated. Hence, an optimal combination of design parameters can be identified to enable low cogging torque motors to be designed. >
221 citations
TL;DR: In this article, the effects of nitrogen content on crystal structure and magnetic properties have been investigated in Sm/sub 2/Fe/sub 17/N/sub x/ specimens with 0 >
Abstract: Effects of nitrogen content on crystal structure and magnetic properties have been investigated in Sm/sub 2/Fe/sub 17/N/sub x/. Sm/sub 2/Fe/sub 17/N/sub x/ specimens with 0 >
211 citations
TL;DR: In this paper, a dynamic generalization of the Preisach hysteresis model is proposed, in which the rate of change of the flux associated with each elementary preisach loops is not infinite, as in the standard PreISach model, but proportional to the difference between the external field and the loop threshold fields.
Abstract: A dynamic generalization of the Preisach hysteresis model is proposed, in which the rate of change of the flux associated with each elementary Preisach loops is not infinite, as in the standard Preisach model, but proportional to the difference between the external field and the loop threshold fields. With this assumption, the shape of the elementary Preisach loops, as well as of the macroscopic hysteresis loops, becomes dependent on the magnetizing frequency f. In particular, it is found that the loop area follows a law of the form C/sub 0/+C/sub 1/ square root f. The model is well suited to applications in the field of power loss calculations in soft magnetic materials. >
196 citations
TL;DR: Different methods are presented for the calculation of torque as a function of rotation angle in an electrical machine, using Maxwell stress tensor, coenergy derivation, Coulomb's virtual work, and the magnetizing current method.
Abstract: Different methods are presented for the calculation of torque as a function of rotation angle in an electrical machine. These methods are integrated in a calculation code by using the finite element method. The movement is taken into account by means of the moving band technique, involving quadrilateral finite elements in the airgap. The torque is calculated during the displacement of the moving part by using the following methods: Maxwell stress tensor, coenergy derivation, Coulomb's virtual work, A. Arkkio's method (1988), and the magnetizing current method. The results obtained by the different methods are compared with experimental data and make it possible to obtain practical information concerning the advantages and limitations of each method. >
142 citations
TL;DR: In this paper, the stator iron loss of a brushless DC motor with due account of the operating condition of the drive system is predicted using finite element analysis, for which the instantaneous currents are derived from a dynamic simulation of a drive system.
Abstract: A procedure has been developed to predict the stator iron loss of a brushless DC motor with due account of the operating condition of the drive system. Finite-element analysis is used to obtain a series of instantaneous magnetostatic field distributions within a motor, for which the instantaneous currents are derived from a dynamic simulation of the drive system. Analysis of the temporal and spatial variation of the flux density distribution then enables localized iron loss densities to be determined. It is shown that the iron loss changes markedly with the operating condition. >
128 citations
TL;DR: A planar microtransformer for use in microswitching converters of portable equipment is described, consisting of planar coils and CoZrRe amorphous magnetic layers on a Si substrate, which operates well at 32 MHz.
Abstract: A planar microtransformer for use in microswitching converters of portable equipment is described. This microtransformer, consisting of planar coils and CoZrRe amorphous magnetic layers on a Si substrate, is fabricated by a dry process. It is about 0.3-mm thick, and 3*4 mm/sup 2/. Its coils provide a relatively high inductance of 33 nH/mm/sup 2/. This microtransformer is implemented in a forward converter, which operates well at 32 MHz. >
126 citations
TL;DR: In this article, the authors present some experimental tests and numerical results on the impulsive response of ground systems when nonlinear ionization phenomena take place, and verify the reliability of the code in the behavior analysis of a ground system excited by high impulsive currents.
Abstract: The authors present some experimental tests and numerical results on the impulsive response of ground systems when nonlinear ionization phenomena take place. The aim of this work is to verify the reliability of the code in the behavior analysis of a ground system excited by high impulsive currents. Experimental tests and numerical results are presented for some typical configurations of ground electrodes. >
114 citations
TL;DR: In this paper, a generalization of the theory of hysteresis to cover asymmetric or minor loops is presented, with the objective of demonstrating the morphology of the solutions.
Abstract: The author describes a generalization of the theory of hysteresis to cover asymmetric or minor hysteresis loop excursions. The original description of the model was found to be particularly useful because it enabled hysteresis loops of magnetic materials to be successfully modeled with a limited set of only five physically based parameters. The extension of the model presented is completely self-consistent with the original formulation and requires no additional parameters to describe the minor loops. Results of the model calculations are shown with the objective of demonstrating the morphology of the solutions. These display the expected behavior and also include the phenomena of minor loop crossing the partial coincidence of minor loops under certain conditions. >
TL;DR: The efficiency of the fast Fourier transform makes it almost always the faster method for any large-size system, while the multipole algorithm remains effective for more complex geometries and systems with highly irregular or nonuniform particle distributions.
Abstract: Evaluation of the long-range magnetostatic field is the most time-consuming part in a micromagnetic simulation. In a magnetic system with N particles, the traditional direct pairwise summation method yields O(N/sup 2/) asymptotic computation time. An adaptive fast algorithm fully implementing the multipole and local expansions of the field integral is shown to yield O(N) computation time. Fast Fourier transform techniques are generalized to entail finite size magnetic systems with nonperiodic boundary conditions, yielding O(N log/sub 2/ N) computation time. Examples are given for calculating domain wall structures in Permalloy thin films. The efficiency of the fast Fourier transform makes it almost always the faster method for any large-size system, while the multipole algorithm remains effective for more complex geometries and systems with highly irregular or nonuniform particle distributions. >
TL;DR: A novel transformation, called the parallelepipedic shell transformation, is developed and this transformation and the manner of implementation of these techniques in Flux3d software lead to an efficient tool for modeling an open boundary problem by means of the finite-element method.
Abstract: A finite element method for the computation of open boundary problems using transformations is presented. The principle of the method is presented. A novel transformation, called the parallelepipedic shell transformation, is developed. This transformation and the manner of implementation of these techniques in Flux3d software lead to an efficient tool for modeling an open boundary problem by means of the finite-element method. Validation, results, and application are presented. >
TL;DR: Several finite element formulations of three-dimensional magnetostatic fields are reviewed in this article, where both nodal and edge elements are considered and the aim is to suggest remedies to some shortcomings of widely used methods.
Abstract: Several finite-element formulations of three-dimensional magnetostatic fields are reviewed. Both nodal and edge elements are considered. The aim is to suggest remedies to some shortcomings of widely used methods. Various formulations are compared based on results for Problem No. 13 of the TEAM Workshops, a nonlinear magnetostatic problem involving thin iron plates. >
TL;DR: In this article, a local force calculation method based on the virtual work principle and the use of the edge element is presented, where the magnetic force is obtained by the derivative of magnetic coenergy or energy with respect to configuration parameters while keeping the circulation of magnetic field or the magnetic flux constant.
Abstract: A local force calculation method based on the virtual work principle and the use of the edge element is presented. In the edge elements, the magnetic coenergy or magnetic energy is expressed by the circulation of magnetic field along edges or by the magnetic flux density across facets according to the use of a magnetic formulation or an electric formulation. The magnetic force is obtained by the derivative of magnetic coenergy or energy with respect to configuration parameters while keeping the circulation of magnetic field or the magnetic flux constant. An eddy current problem is taken as a numerical example. The magnetic force is calculated by the present method and by the j*b method. Results are compared with analytical ones. It is shown that a better accuracy is obtained by the present method. >
TL;DR: In this paper, the relationship between the stored energy and the torque predicted by both the energy method and Maxwell stress integration is discussed and demonstrated by case studies, and recommendations for their implementation are presented.
Abstract: The accuracy of the predicted torque from a finite-element calculation is determined largely by the level of discretization, as well as the evaluation method employed. The stored energy is used to gauge the adequacy of the meshing density in a finite element model for the prediction of the cogging torque in permanent magnet excited motors. The relationship between the stored energy and the torque predicted by both the energy method and Maxwell stress integration is discussed and demonstrated by case studies, and recommendations for their implementation are presented. >
TL;DR: An optimizing environment is described which uses integral methods for calculating user-defined objective functions and results are presented which combine stochastic and direct search techniques to find a satisfactory design optimum of practical problems.
Abstract: Problems of optimization in computational electromagnetics are discussed with particular reference to the determination of the global minimum of practical objective functions. An optimizing environment is described which uses integral methods for calculating user-defined objective functions. Results are presented which combine stochastic and direct search techniques to find a satisfactory design optimum of practical problems. >
TL;DR: In this paper, the authors derived analytical formulae to calculate the magnetic flux distribution in different configurations of nonradially excited machines (stator or rotor excitation, with or without a soft iron return yoke).
Abstract: It is pointed out that a new mode of permanent magnet excitation consisting of segments magnetized nonradially, with different directions of magnetization, produces quite new solutions to the critical problems of permanent magnet excited electrical machines. The authors derive analytical formulae to calculate the magnetic flux distribution in different configurations of nonradially excited machines (stator or rotor excitation, with or without a soft iron return yoke). They also use a numerical method to compute the flux distribution in a 6-pole motor with the excitation on the rotor and in a large 48-pole machine. The advantages of the new excitation as compared with the usual radially magnetized magnets are discussed. >
TL;DR: A technique for use in finite-element models for coupling independent three-dimensional meshes together using Lagrange multipliers and was used to model a switched reluctance motor.
Abstract: A technique for use in finite-element models for coupling independent three-dimensional meshes together is presented. The coupling is done at an interface using Lagrange multipliers which can be identified as the normal component of B on the interface. This technique is particularly well suited to the analysis of devices with moving parts where the modeling of the moving parts at different positions is required. The proposed scheme was used to model a switched reluctance motor which has been modeled previously using conventional finite elements. >
TL;DR: In this article, the authors present a novel formulation which allows the inclusion of the circuit equations in the finite element analysis in two dimensions, allowing the solution of two-dimensional magnetic problems with all kinds of electric connections between conductors, which consist of impedances (R, L and C) fed by sinusoidal sources.
Abstract: The authors present a novel formulation which allows the inclusion of the circuit equations in the finite element analysis in two dimensions. Two types of magnetic conductors are considered: massive conductors which can develop eddy currents and 'fine wire' without eddy current. Kirchhoff's voltage and current equations have been established for these conductors in accordance with magnetic equations. Furthermore, these conductors have been integrated into an external electric network. This formulation allows the solution of two-dimensional magnetic problems with all kinds of electric connections between conductors, which consist of impedances (R, L, and C) fed by sinusoidal sources. The modeling of an asynchronous machine with a squirrel cage (with simulation of end rings) is given to illustrate one application of the formulation. >
TL;DR: Regularization techniques, the stability of solutions, and nonlinear phenomena are shown to be topics closely related to global optimization and inverse problems.
Abstract: Both higher-order (pseudo)deterministic and zeroth-order probabilistic optimization methods have been analyzed and tested for solving the global optimization problems arising in computational electromagnetics. Previously recommended, but seemingly independent schemes (evolution strategies, simulated annealing, Monte Carlo iteration) have been unified into a robust general method: the global evolution strategy (GES). Regularization techniques, the stability of solutions, and nonlinear phenomena are shown to be topics closely related to global optimization and inverse problems. The speed of convergence is evaluated for different optimization methods. A real-world application (from nuclear magnetic resonance and magnetic resonance imaging) demonstrates the favorable behavior of GES in the context of the finite element method. >
TL;DR: In this paper, a modified Newton-Raphson method was proposed to overcome the divergence of the original NN iteration in the nonlinear magnetic field analysis, a relaxation factor was introduced and its optimum value was examined.
Abstract: In order to overcome the divergence of the Newton-Raphson iteration in the nonlinear magnetic field analysis, a relaxation factor is introduced and its optimum value is examined. It is shown that the modified Newton-Raphson method proposed exhibits quick and successful convergence even in the case when the conventional Newton-Raphson method fails in convergence. >
IBM1
TL;DR: A numerical approach for application to micromagnetics problems and the corresponding three-dimensional finite element code has been formulated and implemented and has been applied to the study of hysteretic behavior and domain walls in a variety of samples.
Abstract: The authors have formulated a numerical approach for application to micromagnetics problems and have implemented the corresponding three-dimensional finite element code. The program has been applied to the study of hysteretic behavior and domain walls in a variety of samples. The authors discuss the numerical method and give results of its application to small, rectangular Permalloy particles. >
TL;DR: In this article, a sensitivity analysis for the shape design problems of a two-dimensional nonlinear magnetostatic system is presented, where the algebraic equation resulting from the finite element method is exploited and the adjoint variable method is used.
Abstract: The authors present a sensitivity analysis for the shape design problems of a two-dimensional nonlinear magnetostatic system. In order to derive the design sensitivity, the algebraic equation resulting from the finite element method is exploited and the adjoint variable method is used. This algorithm is applied to the shape design problem of a quadrupole magnet which operates in the magnetic saturation region. Numerical results validate the algorithm. The optimal pole shape with a tolerable deviation is obtained after several iterations. >
TL;DR: A spiral inductor with closed magnetic circuit was fabricated by an RF sputtering machine and photolithography techniques as mentioned in this paper, and the inductance was twice as large as that of a reference sandwiched inductor.
Abstract: A spiral inductor with closed magnetic circuit was fabricated by an RF sputtering machine and photolithography techniques. The inductance was twice as large as that of a reference sandwiched inductor. The authors analyzed the frequency characteristics of the proposed inductor from three points of view: inner current distribution, flux distribution, and eddy current in the magnetic film. The calculated results agree with the measured ones. It is demonstrated that the current distribution inside the inductors is mostly limited to within the area of the conductor up to several hundred megahertz. The frequency characteristics are influenced by the eddy current loss in the Permalloy film and the stray capacitance between the inductor and the ground plane. The permeability of the Permalloy film is less than that of its as-deposited state, but the closed magnetic circuit structure helps to reduce the influence of the demagnetizing field. >
TL;DR: The geometry of a salient pole generator so as to achieve a desired field configuration in the airgap is used as an illustrative numerical example to demonstrate the geometric parametrization technique, emphasize the importance of constraints in engineering design, and highlight the advantageous features of the augmented Lagrangian multiplier method for nonlinear constrained optimization.
Abstract: The shape optimization of magnetic devices is efficiently performed with field calculation and sensitivity analysis based on the finite element method. Several sequential unconstrained optimization techniques are discussed and evaluated with respect to their application in engineering design. The optimization of the geometry of a salient pole generator so as to achieve a desired field configuration in the airgap is used as an illustrative numerical example to demonstrate the geometric parametrization technique, emphasize the importance of constraints in engineering design, and highlight the advantageous features of the augmented Lagrangian multiplier method for nonlinear constrained optimization. For the required geometric parametrization a recent novel use of structural mapping is extended to incorporate constrained optimization. The associated equations of structural mapping are presented. >
TL;DR: In this paper, the Helmholtz theorem is used to describe electromagnetic phenomena in superconductors and the Meissner effect is treated by introducing the magnetizing vector M. The current flow due to flux invasion into the superconductor is evaluated using the current vector potential together with constitutive equations expressing critical state models.
Abstract: Governing equations for describing electromagnetic phenomena in superconductors were derived by using the Helmholtz theorem. The Meissner effect, which is common to type-I and type-II superconductors, is treated by introducing the magnetizing vector M. The current flow due to flux invasion into the superconductor, which is a particular phenomenon in the type-II superconductor, is evaluated using the current vector potential together with constitutive equations expressing critical state models. Numerical results based on a two-dimensional finite-element code showed excellent agreement with analytical solutions. >
TL;DR: A combined strategy for optimization of electromagnetic devices based on a two-stage scheme is described, and showed good behavior, saving, in the best case, up to 70% of the iterations needed for a complete simulated annealing run.
Abstract: A combined strategy for optimization of electromagnetic devices based on a two-stage scheme is described Two different ways of implementing a simulated annealing algorithm, one for discrete and one for continuous variables, have been implemented and tested The second one proved to be more reliable and problem-independent than the other This technique was used in a combined optimization strategy in combination with a pattern search method The combined strategy was tested versus analytical and numerical objective functions and showed good behavior, saving, in the best case, up to 70% of the iterations needed for a complete simulated annealing run The combined strategy was also tested in magnet design problems, with both analytical objective functions and objective functions evaluated by means of finite element codes The results obtained were encouraging in terms of the objective function values obtained and in the computer time needed >
TL;DR: In this paper, a novel type of optical waveguide isolator is proposed, which relies only on the TM/sub 0/ mode propagating in a strip waveguide which is divided by a compensation wall.
Abstract: A novel type of optical waveguide isolator is proposed. It relies only on the TM/sub 0/ mode propagating in a strip waveguide which is divided by a compensation wall. The intensity distribution is different for forward and backward propagation. The backward mode can thus be eliminated by localized optical absorption. Detailed calculations exhibit the required geometry and material parameters. Furthermore, it is demonstrated that optical modulators can be realized using dynamical mode conversion introduced by ferrimagnetic, domain, and domain lattice resonances. Dynamical conversion efficiencies of 10% at frequencies up to 3 GHz are measured. The additional optical absorption caused by impurities incorporated into the garnet films during the epitaxial growth process can be reduced considerably by controlling the growth parameters, or by annealing treatments. Absorption constants of 0.2 cm/sup -1/ at 1.3 mu m wavelength have been achieved. >
TL;DR: In this paper, a new scalar potential formulation for 3D magnetostatic field analysis is presented, based on a convenient partition of the magnetic field that permits representation of multiply connected multifilamentary conductors by means of a fictitious field with known distribution.
Abstract: The authors present a new scalar potential formulation for 3-D magnetostatic field analysis. The method is based on a convenient partition of the magnetic field that permits representation of multiply connected multifilamentary conductors by means of a fictitious field with known distribution. This technique permits the efficient modeling of laminated iron cores with or without air gaps and needs no prior source field calculation. It is implemented in a finite element scheme using first-order tetrahedral elements. The method is validated by comparing the results to an almost-closed-form solution in the case of an iron-free 3-D problem. A transformer example has also been treated. >