近年，電力供給対象の増大と多様化を背景として，DC-DC変換器やDC-AC変換器などの電力変換システム，ならびにモータやアクチュエータなどの電気-機械エネルギー変換システムの高効率化・高機能化が進んでいる。さらに，ワイヤレス給電やエネルギーハーベストなど新しいエネルギー

Efficiency of power electronics circuit in switching power supply and motor drive system is being improved by developing SiC and GaN semiconductor power devices. On the other hand, power losses of magnetic parts including transformer, reactor, and motor are relatively noticeable. To overcome the above problem, it is necessary to establish a quantitative analysis method for power losses of magnetic devices. This paper introduces three recent topics of loss analysis of magnetic devices based on equivalent circuit method. The first one is an analysis of eddy current loss of Mn-Zn ferrite taking account of microstructure, the second one is a magnetic circuit model incorporating a play model, the last one is eddy current analysis of permanent magnet motor based on electric- and magnetic-coupled network model.

In this paper, recent topics of low loss technologies of magnetic components for high frequency power converters are discussed. We mainly describe the equivalent circuit model for the ferrite inductor considering high-frequency magnetic loss, new magnetic material technologies for the magnetic components to reduce the loss, and the loss-reduced design technology of high-frequency transformers for the isolated DC-DC converter.

In this paper, the authors focus on the power generation system in the energy conversion system and describe the recent topics of the vibration power generation technology using the iron-based magnetostrictive material for sensor power supply and the super multi-pole permanent magnet reluctance generator for the small wind power / micro hydraulic power generation.

We report our researches in magnetics applied technology supporting improvements of converter performance. This paper mainly describes the magnetic material, the winding structure, the inductor, the current resonant converter technique for MHz band operation using the magnetic plated wire, and high-frequency operation technique of current resonant converter using GaN transistor. From the various viewpoints including magnetic materials and power magnetic components for the performance improvement of converter operations, we discuss the magnetic application technology of the converter. We hope this paper will be useful to researchers in related specialized fields.

Recently, technologies of wireless power transfer (WPT) using magnetic field resonance coupling have been studied and developed for consumer electrical appliances, and charging systems of electric vehicles, among other applications. This paper reports on recent advances and applications in wireless power transfer on power-magnetics. First, advanced technologies of direct-current (DC)-resonance WPT which has an ability of generating electromagnetic field resonance from DC power source using switching power conversion circuit are described. Second, recent advances in electromagnetic field analysis for WPT are described. Finally, advanced technologies of optimum design and the layouts of transmitting and receiving coils are introduced.

Determining an optimum layout transferring and receiving coils is very important for electromagnetic field resonance type wireless power transfer, in order to obtain target receiving power or efficiency. In this paper, an approach for identifying a coil layout for electromagnetic field resonance type wireless power transfer is proposed. First, a simulation model of coil layout identification has been described. Second, the proposed approach has been applied to identifying an optimum layout of flux phase-shifter coils between transferring and receiving coils, when receiving currents are achieved to target currents. Also, the proposed approach has been applied to identifying an optimum layout of flux phase-shifter coils between transferring and receiving coils, when efficiency is achieved to target one. Further, the approach has been applied to identifying a layout of flux phase-shifter coils, when three receiving currents were balanced three phase currents. As a result, the identified results have been verified the validity of the approach.

One of the challenging issues of iron loss calculation is proper modeling of anomalous eddy current loss. We investigated contribution ratio of anomalous loss in eddy current loss due to higher harmonic component of distorted waveform of flux density and the estimation accuracy of anomalous loss is demonstrated by using hysteresis loops with minor loops.

The Biomagnetism measurement is required shielding effect 1/S≦1/10^-7 for using SQUID magnetometer. The superconducting shield is possible to realize ideal low magnetic noise space. But it is required to attenuate every external field inside hollow superconducting cylinder equally. Especially, radial external field decreases gently comparison to axial field. At this time the length of cylinder needs 4.4 m for diameter 1 m to realize shielding effect 1/S≦1/10^-7. On the other hand, it is only 2.1 m for axial field. For that reason, we devised two methods to attenuate radial field rapidly coupled with permalloy.

6.5%Si steel possesses excellent soft magnetic properties, which can be improved by texture control. In this investigation, we report magnetic properties of grain-oriented 6.5%Si steel with 0.1 mm thickness. The specimens are prepared by cold rolling of grain-oriented 3%Si steel and siliconizing process instead of secondary recrystallization in order to obtain thin and fine-grained specimens to decrease high-frequency iron loss. The grain-oriented 6.5%Si steel shows low iron loss, high flux density and low magnetostriction. This material also shows low iron loss under compressive stress due to its low λ₁₀₀.

To detect the magnetic field using polarization of a light, transparent magnetic material having a Faraday-effect is required. The Co-MgF₂ granular film is promising as a candidate of the Faraday element for the magnetic field sensing. In this study, Fabry-pérot resonant structure was introduced into the Co-MgF₂ granular film to enhance the Faraday-effect. It was found that the Faraday-effect per unit film-thickness [deg./µm] was enhanced due to a light localized in the Co-MgF₂ granular layer sandwiched by Bragg-mirror of the insulator multilayer. The maximum Faraday-effect of the proposed structure was -1.24 deg./µm, which was about 3.4 times enhancement compared with a single Co-MgF₂ film, when the number of layer period x in Fabry-pérot resonant multilayer was 5, where the structure was substrate/ (Ta₂O₅/SiO₂)^x/Co-MgF₂/(SiO₂/Ta₂O₅)²/Air. Furthermore, the multi cavity structure, consisting of the Fabry-pérot resonant multilayer film continuously placed, exhibited a 50% increase of Figure of merit (FOM) defined as Faraday-rotation angle per transmission loss [deg./dB].