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| 1.
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山田, 外史 ; 岩原, 正吉
概要:
Recent papers by the authors have demonstrated the potential for providing rate-of-current-change (dl/dt) and current limiting protection for voltage source fed circuits through the use of a composite magnetic device. The
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application of such a device is presently hampered by the limited choice of commercially available permanent magnet and low saturation flux density materials with square B/H loops. This paper examines the operation of the passive dl/dt or current limiter with a view toward specifying the desired geometric device profile and material characteristics. A voltage source inverter design example is used to illustrate the method by which the design parameters for the device would be specified.<br />Proceedings of the IEEE 4th Workshop on Computers in Power Electronics; Trois-Rivieres, Que, Can; ; 7 August 1994 through 10 August 1994; Code 42401
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| 2.
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山田, 外史
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This paper presents a parallel computation model for the time-periodic nonlinear electromagnetic field analysis in the frequency domain using Harmonic Balance Finite Element Method (HBFEM). The proposed model, different from the
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traditional HBFEM technique that requires large memory and long CPU time, divides the global system matrix into a number of matrices in the frequency domain. Each computation unit has exactly the same number of elements and unknown values. The work involved in calculating the element matrices is equal, therefore the load can be well-balanced and the maximum speed-up will be M times if M processors are available (M is the number of harmonics considered in the electromagnetic field). The model is well-suited to MIMD parallel computer or multiple computers connected by Local Area Networks.<br />Conference Record of the 1996 IEEE Industry Applications 31th IAS Annual Meeting. Part 1 (of 4); San Diego, CA, USA; ; 6 October 1996 through 10 October 1996; Code 45752
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別所, 一夫 ; 山田, 外史
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The electromagnetic pump proposed by the authors is concerned with the magnetic shielding effect of eddy currents in a c
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onductive plate. In this paper we use FEM analysis to examine the shape of a copper plate for controlling eddy currents, and compare our findings with measured results. The proposed T-shaped plate improves shielding and reduces eddy-current losses compared with existing pumps. We also confirmed an improvement of the thrust force when used in a closed system for circulating a liquid alloy. © 1993 IEEE.
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山田, 外史
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Cancer is the most deadly disease in the world today. There is a variety of different treatment methods for cancer, incl
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uding radiotherapy and chemotherapy with anticancer drugs that have been in use over a long period of time. Hyperthermia is one of the cancer treatment methods that utilizes the property that cancer cells are more sensitive to temperature than normal cells. The control of temperature is an important task in achieving success using this treatment method. This paper reports the development of a novel needle-type nanosensor based on the spin-valve giant magnetoresistive (SV-GMR) technique to measure the magnetic flux density inside the body via pricking the needle. The sensor has been fabricated. The modeling and experimental results of flux density measurement have been reported. From the information of flux density, the temperature rise can be estimated to permit the delivery of controlled heating to precisely defined locations in controlled hyperthermia cancer treatment. The actual experiment with human is under investigation. © 2007, IEEE. All rights reserved.<br />Proceedings of the 1997 2nd International Conference on Power Electronics and Drive Systems, PEDS. Part 2 (of 2); Singapore, Singapore; ; 26 May 1997 through 29 May 1997; Code 47014
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山田, 外史 ; 岩原, 正吉
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This paper describes bare printed circuit board (PCB) inspection based on eddy-current testing (ECT) technique with high
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scanning speed. A high-frequency ECT probe composed of a meander coil as an exciting coil and the spin-valve giant magnetoresistance (SV-GMR) sensor was fabricated and is proposed. The ECT probe was designed based on crack inspection over flat surface, especially suitable for microdefect detection on high-density bare PCB. The ECT signal detected by the SV-GMR sensor was acquired by high-speed A/D converter for applying the signal processing based on digital technique. Harmonic analysis based on Fourier transform was used to analyze the ECT signal at fundamental frequency in order to increase inspection speed and this technique allowed the ECT probe to scan bare PCB, with high sampling frequency and with high-spatial resolution inspection. Experimental results verified the possibility and the performance of the proposed PCB inspection system based on ECT technique. © 2007 IEEE.<br />Power Electronics and Drive Systems, 1997. Proceedings., 1997 International Conference on
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岩原, 正吉 ; 山田, 外史
概要:
This paper reports on the development of a new horizontal-shaft hybrid-type magnetic bearing system. The bearing system
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will be used for a horizontal-shaft machine. The rotor is levitated due to the repulsive force between a stator and a rotor permanent magnet (PM). A lower cost and higher radial stiffness have been achieved by using a strontium-ferrite magnet on the rotor and an Nd-Fe-B PM above and below the rotor magnet. A finite-element analysis was performed to calculate the levitation force and radial stiffness. An upper stator magnet subtending an angle of 45° provides the best compromise between a large levitation force and radial stiffness. A model for the horizontal-shaft hybrid magnetic bearing system has been developed and includes the effect of the rotordynamics and the electromagnetic forces. An integral servocontroller was designed to stabilize the axial position. The controller has been implemented in a digital signal processor. Experimental results performed on a prototype system are in agreement with the theoretical results.<br />Third IEEE International Workshop on Electronic Design, Test and Applications, DELTA 2006; Kuala Lumpur; Malaysia; 17 January 2006 through 19 January 2006; Category numberP2500; Code 69206
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山田, 外史
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Numerical modeling and analysis are effective techniques to assist in the design of high-frequency switching power suppl
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ies. Striving for high power densities and higher efficiencies has pushed the operating frequencies up, resulting in new circuit configurations and different component architecture. This paper presents a numerical method that is used to analyze magnetic systems for switching power supplies, in particular the switching resonant dc-dc converters. The method uses the harmonic balance technique combined with finite element methods and is referred to as the harmonic balance-finite element method (HBFEM). The HBFEM is used to solve various harmonic, eddy-current, hysteresis, and nonlinear problems applied to magnetic circuits used in switching power supplies. To evaluate the numerical results, comparisons are made with experimental results. © 1996 IEEE.
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| 8.
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岩原, 正吉 ; 山田, 外史 ; 別所, 一夫
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This paper presents a new 3-dimensional finite element analysis to ac electromagnetic machines with nonlinear magnetic characteristics in a steady state. The method enables us to calculate the time-periodic (non-sinusoidal)
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characteristics in harmonic domain. Unlike the field calculations in time domain, we can obtain only the steady-state solution directly. The application of the parallel processing to this approach is discussed. The analyses of the inductor with shading coil and the model of the flux-concentration type electromagnetic pump are presented.
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| 9.
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岩原, 正吉 ; 山田, 外史
概要:
Static power converters are being used increasingly in power system applications. The power semiconductor switches within the converter systems must be rated to accommodate power system fault currents and system overvoltages.
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Significant cost reductions can be attained by reducing the magnitude of power system fault currents. In this paper we propose the use of a novel passive current limiter to accomplish this task. The limiter consists of two magnetic devices connected in series and in magnetic counter opposition to each other. Each magnetic device consists of three slices of NdFeB permanent magnet material sandwiched between the three end poles of two ferrite E cores. Experimental and finite element results are presented and are found to be in good agreement with each other. The need for 3D modeling in the future is demonstrated. The operating characteristics of the current limiter are experimentally verified using a scaled down version of a power system.
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| 10.
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岩原, 正吉 ; 山田, 外史
概要:
A numerical method for solving electro-magnetically coupled problems with a magnetic nonlinearity such as hysteresis and eddy current is described in the form of matrix tableau equation, and its numerical procedure is shown. The
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method has been applied to a magnetic pulse compression (MPC) circuit, which is made of saturable inductors and capacitors, and is used to laser and particle beam accelerator power supplies. Taking a model circuit of two-stage MPC circuit, the dependency of capacitor ratio was estimated, and the influence of eddy current in the circuit has been demonstrated numerically.
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