Acta Medica Okayama1998Measuring system of magnetostriction under AC excitation using optical methods220220ENTomoyaNakaseMasanoriNakanoF.FujiwaraN.TakahashiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama1999Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux densityENMasanoriNakanoH.NishimotoK.FujiwaraN.TakahashiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama2251986Numerical analysis and experimental study of the error of magnetic field strength measurements with single sheet testers400402ENN.NakataN.TakahashiY.KawaseMasanoriNakanoM.MiuraJ. D.Sievert<p>The error of the measurement of the magnetic field strength with a single sheet tester has been studied. Two different methods, determination by means of field sensing coils (1) and from the magnetizing current (2), have been compared. The errors of methods(1) and (2) were calculated by the finite element method (FEM), different parameters having been varied, and method (2) was additionally studied experimentally. SSTs with wound yokes and stacked yokes were considered. The results will help to decide whether the more complicated and more accurate H coil method or the easier to handle, but less accurate m.c.method is chosen.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama14419973-D eddy current analysis in moving conductor of permanent magnet type of retarder using moving coordinate system13121317ENKazuhiroMuramatsuN.TakahashiT.HashioChujiYamadaMakotoOgawaS.KobayashiTohruKuwahara<p>A 3-D DC steady state eddy current analysis of a permanent magnet type of retarder which rotates at high speed is carried out using a moving coordinate system. The method of DC steady-state analysis using a moving coordinate system is described. The calculated braking torque is compared with measured data</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2651990Effects of eddy currents in the specimen in a single sheet tester on measurement errors16411643ENN.NakataN.TakahashiK.FujiwaraMasanoriNakanoT.Kayada<p>The most favorable construction of the yoke of a single-sheet tester (SST) has been studied by measurements and numerical analysis. It is shown that the eddy currents in a specimen affect the measurement error of the SST, and the error increases with increase in the overhang length and with decrease in the distance between yokes. It is concluded that the single-yoke-type tester has a large error due to eddy currents and that the double-yoke tester is superior. If a single-yoke-type SST is used, the lengths of the B and H coils should be chosen in such a way that the measured power loss is not affected by the eddy currents in the specimen</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2151985Finite element analysis of magnetic fields taking into account hysteresis characteristics18561858ENTakayoshiNakataN.TakahashiY.Kawase<p>A new technique for taking into account hysteresis has been developed. The paper describes the details of the method and the usefulness of the technique is clarified by applying it to the analysis of magnetic fields in single-phase transformer cores. The calculated results are in good agreement with the measured ones.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama19903-D Magnetic field analysis by using special elementsENTakayoshiNakataN.TakahashiK.FujiwaraY.ShirakiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama26219903-D open boundary magnetic field analysis using infinite element based on hybrid finite element method368370ENTakayoshiNakataN.TakahashiK.FujiwaraM.Sakaguchi<p>A method for analyzing 3-D open-boundary magnetic field problems using infinite elements has been developed. The infinite problem has the advantage that the bandwidth of the coefficient matrix and the number of unknown variables are reduced. Moreover, no experience is necessary in determining decay parameters. The effectiveness of the infinite-element method is illustrated by the accuracy and the CPU time obtained when various boundary conditions are applied</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2761991Optimal design of injection mold for plastic bonded magnet49924994ENTakayoshiNakataN.TakahashiK.FujiwaraT.Kawashima<p>The optimal design of an injection mold for producing a stronger multipole magnet is carried out using the finite element method and the direct search method. It is shown that the maximum flux density in the cavity obtained by the optimal design is about 2.6 times higher than that of the initial shape determined empirically. 3-D analysis of the nonlinear magnetic field in the injection mold with complicated structure is also carried out. The calculated flux distribution on the cavity surface is in good agreement with the measured one</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1961983New design method of permanent magnets by using the finite element method24942497ENTakayoshiNakataN.Takahashi<p>A new method for determining the shapes and sizes of magnets which produce the prescribed flux densities by using the finite element method has been developed. In this paper, the new technique is explained briefly, and then the finite element formulation for non-linear analysis is derived. Finally, the usefulness of the technique is shown by applying this method to the design of magnetic circuits.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1998Measuring System of Magnetostriction Under AC Excitation Using Optical Methods220220ENTomoyaNakaseMasanoriNakanoF.FujiwaraN.Takahashi<p>A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined. Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured up to 2.0 T </p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2005Evaluation of alternating flux leakage testing using 3-d non-linear eddy current analysis349349ENYujiGotohA.RadinN.TakahashiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama1999An open magnetic path type of single sheet tester for measurement of magnetostriction of electrical steel sheetENTomoyaNakaseMasanoriNakanoK.FujiwaraN.TakahashiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama2351987Optimization of permanent linear wiggler for free electron laser by using the 3-D finite element method37743776ENTakayoshiNakataN.TakahashiA.ImadaN.TabauchiM.Kumada<p>The optimal configuration of magnets of a linear wiggler, which produces the flux focussing and wiggling of an electron beam, has been investigated in order to improve the performance of a device for producing free electron lasers. The effects of the distribution of magnetization, the structure and the magnet height on the flux distribution in the wiggler are examined. The optimal configuration of the wiggler is obtained by numerical analysis.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2461988Comparison of various methods for 3-D eddy current analysis31593161ENTakayoshiNakataN.TakahashiK.FujiwaraKazuhiroMuramatsuZ. G.Cheng<p>Computer codes developed for the A-φ, A-φ-Ω, A-Ω, T-Ω, and E-Ω methods are considered. Their accuracy, storage requirements, and CPU time are compared for linear eddy-current models. It is shown that the A-φ-Ω and T-Ω methods are preferable from the viewpoint of accuracy. The A-Ω and E-Ω methods are preferable with respect to storage and CPU time</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2621990 Effects of permeability of magnetic materials on errors of the T-Ω method698701ENTakayoshiNakataN.TakahashiK.FujiwaraT.Imai<p>The error inherent in the T-Ω method due to cancellation between the current vector potential T and gradΩ terms is investigated by solving typical models. The cancellation error is examined using not only an axisymmetric simple model but also a three-dimensional one. The effect of permeability on the error of the T-Ω method is quantitatively examined using the simple model under DC and AC excitations. The errors in single precision and double precision are also investigated, and the allowable range of permeability is discussed. The magnetic field of the IEEJ model analyzed, and the calculated results are compared with measured ones. It is concluded that, although in general the error increases with the increase in permeability, the magnitude of the error is negligibly small if the calculation is carried out in double precision</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama24619883-D Finite element method for analyzing magnetic fields in electrical machines excited from voltage sources25822584ENTakayoshiNakataN.TakahashiK.FujiwaraAkiraAhagon<p>A method for analyzing 3-D magnetic fields and currents in electrical machines excited from voltage sources has been developed. It was obtained by expanding the 2-D finite-element method into three dimensions, using the A φ method. The basic idea and the finite-element formulation are described. The effectiveness of the method is shown by some application examples</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2621990Comparison of different finite elements for 3-D eddy current analysis434437ENTakayoshiNakataN.TakahashiK.FujiwaraY.Shiraki<p>In order to evaluate the best type of element for the finite-element analysis of 3-D eddy currents, a fundamental model is analyzed using the usual first-order tetrahedral, triangular prism, and brick nodal elements, and also the brick edge element. The effects of the types of elements on the flux and eddy-current distributions are investigated using the A-φ method and the T-Ω method. It is concluded that the brick edge element is best from the viewpoints of accuracy and CPU time</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama3652000Optimal design of efficient IPM motor using finite element method35373539ENTakumaOhnishiN.Takahashi<p>Techniques for the optimal design of permanent magnet motors considering rotation are investigated. The nonconforming mesh technique is used to take into account the rotation of the rotor. It is shown that the technique is especially useful for the optimal design using the finite element method, because no modification of mesh is necessary during the rotation. The mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator. By using the combined optimization technique of the experimental design method and Rosenbrock's method, the number of FEM calculations can be reduced. By applying the optimal design method, about 40% of volume of permanent magnet of IPM motor and about 15% of the torque ripple can be reduced</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2005Improvement of zone control induction heating equipment for high-speed processing of semiconductor10691070ENDaisukeMiyagiAisyaSaitohN.TakahashiN.UchidaKazuhiroOzaki<p>In this paper, the effect of dividing into several small coil groups having different current and frequency on heating characteristics is investigated using FEM (finite element method). The heating characteristics of graphite of each coil is examined, and a useful information for controlling current and frequency, which realize the nearly uniform heating, is obtained.</p>No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2621990Investigation of effectiveness of various methods with different unknown variables for 3-D eddy current analysis442445ENTakayoshiNakataN.TakahashiK.FujiwaraKazuhiroMuramatsu<p>Computer codes using the A-φ, A-φ-Ω, A*-0Ω-E, T-Ω, and E-Ω methods were developed. The effects of the volume ratio of the conductor region to the whole region, the shape of the conductor, and the ratio of the hole region to the conductor region on the computer storage, the CPU time, and the accuracy of the methods are investigated systematically using a few simple models. The effect of the conductivity of the conductor is also examined. The computer storage, the CPU time, and the error are found to increase with increase of the volume ratio of the conductor region to the whole region. The computer storage and the CPU time are affected by the shape of the conductor in some methods of analysis. The error of the A*-Ω(E-Ω) method is larger than that of the other methods</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1992Improvement of measuring method of DC magnetization curve using ring specimen153153ENTakayoshiNakataN.TakahashiK.FujiwaraMasanoriNakanoY.OguraK.MatsubaraNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama1998Measuring System of Magnetostriction Under AC Excitation Using Optical Methods220220ENTomoyaNakaseMsanoriNakanoF.FujiwaraN.Takahashi<p>A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined. Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured up to 2.0 T </p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2161985New approximate method for calculating three-dimensional magnetic fields in laminated cores23742377ENTakayoshiNakataN.TakahashiY.Kawase<p>A new approximate method for calculating three-dimensional magnetic fields in laminated cores has been developed by modifying the two-dimensional finite element method. Using this new method, both computer storage and computing time can be considerably reduced compared with a three-dimensional analysis. In this paper, the new technique is explained, and then its usefulness is shown by applying it to the analysis of flux distributions at the T-joint of the so-called scrap-less type three-phase transformer core.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2051984Influence of lamination orientation and stacking on magnetic characteristics of grain-oriented silicon steel laminations17741776ENTakayoshiNakataN.TakahashiY.KawaseN.Nakano<p>Analytical and experimental investigations have been carried out upon the behaviour of flux in laminations, where the rolling directions of adjacent sheets are reversed. The paper clarifies the mechanism of the greatly different magnetic characteristics between such laminations and usual ones, where the rolling directions of adjacent sheets are coincident.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2751991Comparison of various methods of analysis and finite elements in 3-D magnetic field analysis40734076ENTakayoshiNakataN.TakahashiK.FujiwaraT.ImaiKazuhiroMuramatsu<p>In order to evaluate the most suitable method of analysis (A- phi or T- Omega method) and finite element (nodal or edge element) for a given problem, the features of each method and element have been investigated. The accuracy, computer storage, and CPU time of each method and element are compared for a 3-D nonlinear magnetostatic model and a 3-D eddy current model. The flux and eddy current densities calculated are compared with those measured. It is shown that the accuracy and the CPU time of the edge element are better than those of the nodal element. The A- phi method is better than T- Omega method for nonlinear problems from the viewpoint of convergence characteristics of nonlinear iterations.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2161985Finite element analysis of magnetic circuits composed of axisymmetric and rectangular regions21992202ENTakayoshiNakataN.TakahashiY.KawaseH.FunakoshiS.Ito<p>A new approximate method is developed for calculating three-dimensional magnetic fields in magnetic circuits composed of connected axisymmetric and rectangular regions. Using this new method, fairly accurate solutions can be obtained when the leakage flux from the magnetic circuit is small. In this paper, the new method is explained and then the usefulness of the technique is clarified by comparing calculated and measured flux densities.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2461988Periodic boundary condition for 3-D magnetic field analysis and its applications to electrical machines26942696ENTakayoshiNakataN.TakahashiK.FujiwaraAkiraAhagon<p>A periodic boundary condition in 3-D analysis is examined. The definition of 3-D periodic phenomena is clarified, and the periodic conditions for the A-φ boundary conditions are shown by analyzing some models and observing that the CPU time is considerably decreased. The periodic condition is applied to the analysis of an actual induction motor</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2621990Finite element analysis of induced currents in axisymmetric multi-conductors connected in parallel to voltage sources968970ENTakayoshiNakataN.TakahashiK.FujiwaraH.NiinobeK.Misawa<p>A method for analyzing induced currents, including both eddy currents and circulating currents, in axisymmetric multiconductors connected in parallel to voltage sources has been developed using the finite-elements method. The method has the advantage that the nonlinear analysis of induced currents in conductors connected to voltage sources with distorted waveforms (for example, an inverted-fed transformer) is possible. Because the method can take into account the voltage sources, the external impedances, and the nonlinearity of the core it becomes possible to analyze flux and current distributions under actual operating conditions and to design windings which produce the minimum power loss. The effectiveness of the method is illustrated by applying it to a transformer model</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2251986Analysis of magnetic characteristics of a brushless DC motor taking into account the distribution of magnetization10841086ENTakayoshiNakataN.TakahashiK.Uehara<p>Magnetic characteristics of a brushless d.c. motor have been analyzed taking into account the magnetization distribution in the rotor magnet. The magnetization is calculated taking into account the magnetizing process of a magnet. This paper describes a method for calculating the magnetization in the magnet, and the effects of the pattern of magnetization distribution and the shape of the coil on torque ripples. The calculated results are in good agreement with the results measured. Because the flux distribution and the torque characteristics can be calculated, the optimum design of the brushless d.c. motor will be possible without repeating a trial manufacture.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama19923-D Adaptive Mesh Refinement Using Nonconforming MeshENKazuhiroMuramatsuTakayoshiNakataN.TakahashiK.FujiwaraNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama1861982Magnetic performance of step-lap joints in distribution transformer cores10551057ENTakayoshiNakataN.TakahashiY.Kawase<p>The magnetic characteristis of cores with step-lap joints are analyzed by using the finite element method taking into account eddy current and magnetic saturation. The effects of the following factors on the magnetic characteristics such as flux and eddy current distributions and magnetizing current are clarified quantitatively. 1)step-lap length 2)length of air gap at the joint 3)number of laminations per one stagger layer 4)flux density (magnetic saturation) Obtained results give useful suggestions improving the design of the joints of transformer cores.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2851992An improved method for determining the DC magnetization curve using a ring specimen24562458ENTakayoshiNakataN.TakahashiK.FujiwaraMasanoriNakanoY.Ogura<p>When the DC magnetization curve (B-H) of nonoriented material is measured in a ring specimen, there is an intrinsic error due to the assumption that the mean magnetic path length is equal to the mean geometric path length. A novel method for determining the B-H curve accurately is proposed. The validity of the method is verified by experiments</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2251986New technique for producing a strong multi-pole magnet10721074ENTakayoshiNakataN.TakahashiG.KawashimaK.Fujiwara<p>A new technique for producing strong multipole magnet is developed. A cylindrical magnet oriented with its easy axis of magnetization perpendicular to the cylinder axis is magnetized by a multipole magnetizer. This procedure results in a multipole magnet with a flux density almost sixty percent greater than the flux density produced by a multi-pole magnet which is not oriented. The technique is especially effective for producing small cylindrical magnets with many poles and agreement of a theoretical analysis with experimental results is very good, with deviations of no more than a few percent.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama20053-D FEM Analysis of SPT Head Dimension on Recording Characteristics575576ENMasayaOhtakeA.SadatoshiN.Takahashi<p>In this paper, the effect of the width of write head on behavior of flux and magnetization in the case of continuous track media and discrete track media is investigated using 3-D read/write simulation system. The effect of width of read head on the output is also examined.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2851992A low loss transformer using a rotating magnetic field21632165ENTakayoshiNakataN.TakahashiK.FujiwaraMasanoriNakanoM.Nagao<p>A type of transformer with reduced iron loss, which is excited by a semirotating magnetic field, has been investigated. Factors (method of excitation and slits in the core) affecting iron losses are examined. The iron loss of this type of transformer can be reduced below the material loss as measured for normal AC excitation by introducing a slit which cuts the eddy current path, and by improving the method of excitation</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama26519903-D magnetic field analysis using special elements23792381ENTakayoshiNakataN.TakahashiK.FujiwaraY.Shiraki<p>Three-dimensional special elements, called the gap element, the expanding element, and the shielding element, have been conceived for discretizing narrow gaps in an iron core, the long legs of a transformer core, and thin shielding plates. The concept of the 3D special element and its finite-element formulation are described. The special elements are applied to several models, and the effects of the elements on accuracy and CPU time are discussed. It is shown that CPU time can be reduced by using the special elements</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2412006efficient solving techniques of matrix equations for finite element analysis of eddy currents170173ENTakayoshiNakataN.TakahashiK.Fujiwara<p>Two efficient techniques for solving matrix equations for 2-D finite element analysis of eddy currents in electrical machinery connected to constant voltage sources are presented. In these analyses, in which the existing currents are treated as unknown variables, the coefficient matrix becomes unsymmetrical. By treating the components of grad φ as variables and introducing a symmetrization technique, the computer storage and the computing time can be considerably reduced</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2921993A simple algorithm for adaptive refinement of tetrahedral meshes combined with edge elements18981901ENPiotrOlszewskiTakayoshiNakataN.TakahashiK.Fujiwara<p>A simple algorithm yielding unique face subdivision patterns of locally refined tetrahedral elements by the Delaunay tessellation process is presented. Due to the numerous advantages of edge elements, the algorithm is combined with the magnetostatic edge element computer code. A comparative analysis of four different error estimates used to locate elements for refinement, including a new one suitable for edge elements, is described. The performance of the proposed algorithm and the effectiveness of the error estimates are demonstrated by means of three-dimensional test problems </p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama3051994An improved numerical analysis of flux distributions in anisotropic materials33953398ENTakayoshiNakataK.FujiwaraN.TakahashiMasanoriNakanoN.Okamoto<p>The method for analyzing flux distributions in transformer cores made of grain-oriented silicon steel is improved in order to reduce error in calculation due to anisotropy in magnetic materials. A model to verify the improved method is proposed, and the calculated results are compared with measured ones</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2961993Measurement of magnetic characteristics along arbitrary directions of grain-oriented silicon steel up to high flux densities35443546ENTakayoshiNakataN.TakahashiK.FujiwaraMasanoriNakano<p>A technique for measuring B-H curves of grain-oriented silicon steel along arbitrary directions has been developed. As the control of waveform is not necessary in this technique, it is possible to measure B-H curves up to high flux densities which are required for calculating flux distribution using the finite element method</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2251986Numerical analysis of transient magnetic field in a capacitor-discharge impulse magnetizer526528ENTakayoshiNakataN.Takahashi<p>A method for analyzing the magnetic field in a capacitor-discharge impulse magnetizer is established by modifying the finite element method. The effects of charging voltage, capacitance and resistance on the behaviour of the localized fluxes in the Impulse magnetizer are analyzed quantitatively. As the detailed distribution of the flux density can be obtained, the optimum design of the magnetizer which produce desired magnet will be possible using our new method.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2621990Investigation of a model to verify softwares for 3-D nonlinear eddy current analysis501504ENTakayoshiNakataN.TakahashiK.Fujiwara<p>The general characteristics of the most suitable model for 3-D nonlinear eddy-current analysis are examined and some factors that might affect the calculated and experimental results are investigated. For example, various types of elements are compared with each other. A transient nonlinear model is proposed and the flux and eddy current distributions obtained by the finite-element method are compared with experimental results</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama2005Optimal design of efficient IPM motor using finite element method252252ENTakumaOhnishiN.TakahashiNo potential conflict of interest relevant to this article was reported.Acta Medica Okayama2821992Improvements of convergence characteristics of Newton-Raphson method for nonlinear magnetic field analysis10481051ENTakayoshiNakataN.TakahashiK.FujiwaraN.OkamotoKazuhiroMuramatsu<p>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</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama3652000Optimal design of efficient IPM motor using finite element method35373539ENTakumaOhnishiN.Takahashi<p>Techniques for the optimal design of permanent magnet motors considering rotation are investigated. The nonconforming mesh technique is used to take into account the rotation of the rotor. It is shown that the technique is especially useful for the optimal design using the finite element method, because no modification of mesh is necessary during the rotation. The mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator. By using the combined optimization technique of the experimental design method and Rosenbrock's method, the number of FEM calculations can be reduced. By applying the optimal design method, about 40% of volume of permanent magnet of IPM motor and about 15% of the torque ripple can be reduced</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1861982Application of the finite element method to the design of permanent magnets10491051ENTakayoshiNakataN.Takahashi<p>A new method of determining the lengths of magnets in a magnetic circuit by using the finite element method has been developed. This method has the advantage that the lengths of magnets which produce the prescribed flux distribution can be directly calculated. In this paper, the error of this method is discussed at first, and then an example of application determining the shape of a magnet is shown. This method is effective for the design of magnetic circuits consisting of several permanent magnets and the determination of the shapes of magnets.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama1821982Direct finite element analysis of flux and current distributions under specified conditions325330ENTakayoshiNakataN.Takahashi<p>When the flux distribution of a magnetic circuit is analyzed by using the conventional finite element method, the magnetizing currents must be given. Therefore, if the flux distribution is specified, it is difficult to obtain the distributions of magnetomotive forces or configuration of magnets producing the specified field distribution by the conventional finite element method. New methods which are called the "finite element method taking account of external power source" and the "finite element method with shape modification" have been developed. The processes of calculation in these methods are contrary to the conventional technique. These new methods have the following advantages: (a) If there are many unknown independent magnetizing currents, these currents are directly calculated by the new method. (b) When a flux distribution is specified, the optimum shapes of the magnets can be directly calculated. (c) As these new methods need no repetition, computing time can be considerably reduced. The principles and the finite element formulations of these new methods are described, and a few examples of application of these methods are shown. These new methods make it possible to design the optimum magnetic circuits by using the finite element method.</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama3652000Optimal design of efficient IPM motor using finite element method35373539ENTakumaOhnishiN.Takahashi<p>Techniques for the optimal design of permanent magnet motors considering rotation are investigated. The nonconforming mesh technique is used to take into account the rotation of the rotor. It is shown that the technique is especially useful for the optimal design using the finite element method, because no modification of mesh is necessary during the rotation. The mesh at each angle of rotation can be obtained by only combining meshes of a rotor and a stator. By using the combined optimization technique of the experimental design method and Rosenbrock's method, the number of FEM calculations can be reduced. By applying the optimal design method, about 40% of volume of permanent magnet of IPM motor and about 15% of the torque ripple can be reduced</p>
No potential conflict of interest relevant to this article was reported.Acta Medica Okayama411020053-D FEM analysis of the effects of SPT head dimensions on recording in discrete and continuous media28932895ENMasayaOhtakeA.SadatoshiN.Takahashi<p>Due to the considerable increase of magnetic recording density, the deviation of the head from the centerline of the track becomes a serious problem for the cross-track interference. In this paper, a three-dimensional read/write simulation system was used to investigate the effect of the width of the write head on the behavior of the flux and magnetization for continuous track medium and discrete track medium. It is shown that the magnetization in a neighboring track of the discrete track medium is smaller than that of the continuous track medium. The output of the read head using the discrete track medium is larger than that of the continuous track medium when a suitable read head width is chosen so that the cross talk is negligible.</p>
No potential conflict of interest relevant to this article was reported.