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Progress in R&D of coated conductor in M-PACC project
Izumi, T.,Ibi, A.,Nakaoka, K.,Taneda, T.,Yoshida, T.,Takagi, Y.,Nakamura, T.,Machi, T.,Katayama, K.,Sakai, N.,Yoshizumi, M.,Koizumi, T.,Kimura, K.,Kato, T.,Kiss, T.,Shiohara, Y. The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.2
The five-year national project in Japan for R&D of coated conductors and applications, named as the Materials and Power Applications of Coated Conductors (M-PACC) project, was finished at the end of FY2013. The project consists of four sub-themes as cable, transformer, SMES and coated conductors. In the theme of coated conductors, the fabrication process had been developed to satisfy the requirements from the applications such as in-field $I_c$ performance, low AC loss in the long tapes etc. Through the project, the remarkable progress was achieved as follows; a high in-field minimum $I_c$ value over 54A/cm-width under 3T at 77K was realized in a 200m long EuBCO tape with artificial pinning centers of $BaHfO_3$ by the pulsed laser deposition (PLD) technique on the IBAD template. On the other hand, the AC loss reduction was confirmed in the tapes fabricated by both PLD and the metal organic deposition (MOD) techniques by scribing 100m tapes into 10-filamments. Additionally, the mechanism of the delamination phenomenon was systematically investigated and the strength was improved by eliminating the origins of the weak points in the films. Through the development, all targeted goals were accomplished and the several results were appreciated as a world champion data.
Kwon, Y. G.,Ishiguro, M.,Shinnaka, Y.,Nakaoka, T.,Kuroda, D.,Hanayama, H.,Takahashi, J.,Baar, S.,Saito, T.,Kawabata, M.,Uemura, M.,Morokuma, T.,Murata, K. L.,Takagi, S.,Morihana, K.,Nagayama, T.,Sekig Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-
<P><I>Context.</I> Spectropolarimetry is a powerful technique for investigating the physical properties of gas and solid materials in cometary comae without mutual contamination, but only a few spectropolarimetric studies have been conducted to extract each component.</P><P><I>Aims.</I> We attempt to derive the continuum (i.e., scattered light from dust coma) polarization degree of comet 2P/Encke, free of the influence of molecular emissions. The target is unique in that its orbit is dynamically decoupled from Jupiter, like the main-belt asteroids, but it ejects gas and dust like ordinary comets.</P><P><I>Methods.</I> We observed the comet using the Hiroshima Optical and Near-Infrared Camera attached to the Cassegrain focus of the 150 cm Kanata telescope on UT 2017 February 21 when the comet was at the solar phase angle of <I>α</I> = 75°.7.</P><P><I>Results.</I> We find that the continuum polarization degree with respect to the scattering plane is <I>P</I>cont, r = 33.8 ± 2.7% at the effective wavelength of 0.82 <I>μ</I>m, which is significantly higher than those of cometary dust in a high-<I>P</I>max group at similar phase angles. Assuming that an ensemble polarimetric response of the dust of 2P/Encke as a function of phase angle is morphologically similar with those of other comets, its maximum polarization degree is estimated to <I>P</I>max ≳ 40% at <I>α</I>max ≈ 100°. In addition, we obtain the polarization degrees of the C2 swan bands (0.51-0.56 <I>μ</I>m), the NH2<I>α</I> bands (0.62-0.69 <I>μ</I>m), and the CN-red system (0.78-0.94 <I>μ</I>m) in a range of 3-19%, which depend on the molecular species and rotational quantum numbers of each branch. The polarization vector is aligned nearly perpendicularly to the scattering plane with an average of 0°.4 over a wavelength range of 0.50-0.97 <I>μ</I>m.</P><P><I>Conclusions.</I> From the observational evidence, we conjecture that the high polarization degree of 2P/Encke might be attributable to a dominance of large dust particles around the nucleus, which have remained after frequent perihelion passages near the Sun.</P>
J.Yoshitsugu,M.Ando,M.Rukonuzzaman,E.Hiraki,M.Nakaoka,K.Inoue 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
This paper presents a circuit of the quasi-resonant DC link to achieve soft-switching three phase inverter using intelligent IGBT power module. The soft-switching operation in this circuit is confirmed simulation and experimental results. Its conductive noise is measured for electrical AC motor drive as compared with that of the conventional hard switching inverter.<br/>
SINGLE-PHASE CURRENT SOURCE INVERTER WITH PULSE AREA MODULATION SCHEME FOR SOLAR POWER CONDITIONER
K.Hirachi,K.Matsumoto,M.Ishitobi,M.Ishibashi,M.Nakaoka 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
In general, a singte-phase current-fed PWM inverter using IGBTs has some unique advantages for small scale distributed utility-interactive power supply system as compared with voltage-fed PWM inverter. In particular, this is more suitable and acceptable for a non-isolated type utility-interactive power conditioner, which is going to be widely used for residential solar photovoltaic (PV) power generation system in Japan However, this current-fed PWM inverter has a significant disadvantage. The output current of this inverter includes large harmonic contents when the inductance of smoothing reactor in its DC side is not large enough to eliminate its current ripple components of this inverter In order to overcome this problem, a new conceptual pulse area modulation scheme for this inverter is introduced in difference with conventional PWM strategy. This paper presents a new effective control implementation of this PV power conditioner which is able to reduce the harmonic component in the output current produced by the single-phase current-fed PWM inverter even when the npple current in the smoothing DC reactor is relatively large. The operating principle of the proposed control strategy introdued for this inverter system is described, and its simulation results are evaluated and discussed herein.<br/>
Ahmad M. Eid,Hyun Woo Lee,Mutsuo Nakaoka 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4
Various methods have been discussed to reduce detent force in a tubular permanent magnet type linear single phase AC generator. In particular, the proposed methods depend on variations of the permanent magnet construction. These methods include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of optimizing the magnet length. The undesired detent force ripples were calculated by a two dimensional Finite Element Method (FEM). Moreover, the generated electromotive force in the stator coils was calculated for each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the detent force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that sloping the permanent magnet decreased the detent force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.
Efficient Linear Generator Design with Reduced Output Voltage Harmonics
Ahmad M. Eid,S. K. Kwon,Ki-Young Sub,Hyun Woo Lee,Mutsuo Nakaoka 전력전자학회 2005 전력전자학술대회 논문집 Vol.- No.-
Two-dimensional finite element method was used in the analysis to calculate the magnetic field parameters in a radial permanent magnet linear single-phase AC alternator. Both surface (SPM-LA) and internal permanent magnet (IPM-LA) prototype schemes are analyzed and compared according to three different parameters; the cogging force, the induced AC voltage and the THD of the induced AC voltage. Three different methods were used to reduce the THD of the induced voltage, tooth shoe, stepped tooth and chamfered tooth. It was found that the cogging force of the IPM-LA prototype scheme is always less than that of SPM-LA configuration due to the pole shoe. The stepped and chamfered tooth methods could achieve standard values for the THD of the induced voltage of the SPM-LA scheme. The cogging force was much reduced using the stator optimal length; for both schemes, as well as, the total alternator weight is reduced.
Rukonuzzaman, M.,Nakaoka, Mutsuo The Korean Institute of Power Electronics 2002 JOURNAL OF POWER ELECTRONICS Vol.2 No.1
An advanced active power filter for the compensation of instantaneous harmonic current components in nonlinear current load is presented in this paper. A novel signal processing technique using an adaptive neural network algorithm is applied for the detection of harmonic components generated by three-phase nonlinear current loads and this method can efficiently determine the instantaneous harmonic components in real time. The control strategy of the switching signals to compensate current harmonics of the three-phase inverter is also discussed and its switching signals are generated with the space voltage vector modulation scheme. The validity of this active filtering processing system to compensate current harmonics is substantiated on the basis of simulation results.
PERFORMANCE AND DESIGN OF A SINGLE-PHASE LINEAR SYNCHRONOUS GENERATOR USING FINITE ELEMENT METHOD
Ahmad M. Eid,김성준(Sung-Jun Kim),강주성(Ju-Sung Kang),이현우(Hyun-Woo Lee),Mutsuo Nakaoka 한국조명·전기설비학회 2005 한국조명·전기설비학회 학술대회논문집 Vol.2005 No.11월
This paper presents a general proposal to design and calculate the performance of a tubular permanent magnet linear generator treated here on the basis of the Finite Element Method. Optimizing the linear generator dimensions reduces the cogging force, which occurs due to the interaction between stator teeth and the permanent magnets. The generated AC voltage is analyzed and evaluated for both no load and load cases to take the armature reaction effects on the air gap flux density. A repetitive routine is followed to calculate the output AC voltage front the change of flux and tile speed of the single-phase linear generator. The AC output voltage is calculated for different resistive loads, and hence, tile linear generator load characteristic is obtained. The designed linear generator is capable to generate an output power of 5.3kW with AC output voltage of 222V with an efficiency of 96.8% at full load of 23.8A. The full load current is chosen based on the thermal properties of the coil wire Insulations.