IEEJ Transactions on Fundamentals and Materials
Online ISSN : 1347-5533
Print ISSN : 0385-4205
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Paper
  • Atsushi Tsujita, Masashi Ohchi, Takayuki Wakimoto
    2018 Volume 138 Issue 8 Pages 400-407
    Published: August 01, 2018
    Released: August 01, 2018
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    We have been studying on estimating distribution of permittivity between measurement electrodes using capacitance and electric potential. Two arc electrodes were separated by long distance and there electrodes were surrounded by additional electrodes respectively. In past research work, we carried out numerical electric analysis for calculating the capacitance and electric potential using Finite Element Method(FEM) and compared with experimental and numerical results. The capacitance values were almost agree with experimental and numerical results. However, the electric potential values were different between experimental and numerical results in conventional studies. In this paper, we proposed an equivalent circuit including the stray capacity and measurement method for capacitance, the electric potential in space between long distance electrodes was estimeded.

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  • Yukihiro Tozawa, Makoto Sugihashi, Takeshi Ishida, Osamu Fujiwara, Shu ...
    2018 Volume 138 Issue 8 Pages 408-415
    Published: August 01, 2018
    Released: August 01, 2018
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    The International Electrotechnical Commission (IEC) 61000-4-2 specifies an air discharge testing method as a mandatory electrostatic discharge (ESD) immunity test, since an actual charged human accompanies air discharges. In addition, the IEC standard also prescribes the holding time of over 5 s where the decrease of the discharge electrode voltage due to current leakage, prior to the air discharge, should not be greater than 10%, whereas no measurement method has been specified. In this study, a method is proposed for measuring the holding output voltage of an ESD generator in air discharge mode with a commercially available high voltage probe connected through a wire to a small metal sphere for contact discharges and air discharges. The proposed method consists of two steps that measure the peak voltages for contact discharge with a test voltage and for air discharge with the same test voltage but in 5 seconds after the trigger. The ratio of the latter peak voltage to the former one provides the ratio of the holding output voltage to the test voltage. The measurement principle is shown theoretically using the equivalent circuits for a measurement setup, and is validated numerically and experimentally. To demonstrate the effectiveness of the presented method, measurements of the holding output voltages for two defective ESD generators collected from the market are conducted in comparison with a normal ESD generator.

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  • Chenglin Li, Mahmudul Kabir, Noboru Yoshimura
    2018 Volume 138 Issue 8 Pages 416-421
    Published: August 01, 2018
    Released: August 01, 2018
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    Illumination covers almost 20%-30% of total electric consumption in office buildings. Using daylight may be a good choice to reduce lighting power consumption. However, the sunlight is dazzling when it enters the room directly and thus cannot be used as a direct light source. Therefore, it is necessary to develop a window system that combines seasonal strong light shielding and daylight utilization as well. In this paper the angle change type blind reflection plate is proposed where the entering sunlight will be reflected to the ceiling and act as a light source for the interior illumination. We have made a simulator for interior illumination system which can be used in any season in a year and it is also applicable in any size of the room. The simulator can use the daylight and has showed a very accurate illumination distribution results which supports the idea that using daylight in interior illumination is good for reducing the electricity consumption in offices.

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  • Hirofumi Maruyama, Kensuke Matsuo, Masahiro Kozako, Masayuki Hikita, K ...
    2018 Volume 138 Issue 8 Pages 422-427
    Published: August 01, 2018
    Released: August 01, 2018
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    It is crucial for cast resin transformer to detect void and delamination existing in the cast resin because these defects reduce insulation performance of cast resin equipment. Furthermore, defects are likely to be mixed in cast resin because of several surface boundaries between resin and conductor. It is considered that detecting partial discharge (PD) is effectiveness to diagnose equipment of power equipment. However, it is reported that withstand lightning impulse voltage test may give influence on AC partial discharge test, especially partial discharge inception voltage (PDIV). This paper deals with accumulated charge in a void under AC voltage to investigate the effect of the impulse voltage pre-stress on subsequent ac PD characteristics in cast resin transformer. AC PD characteristics were compared before and after impulse application. In addition, recovery of PD characteristics was measured to investigate charge decay. As a result, the mechanism of pre-stress effect is revealed and surface charge density is estimated quantitatively in cast resin transformer.

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  • Toshifumi Kobori, Takeshi Fukuda, Norihiko Kamata
    2018 Volume 138 Issue 8 Pages 428-434
    Published: August 01, 2018
    Released: August 01, 2018
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    In this stduy, we investigated the effect of electron transport layer (ETL) on performances of inverted organic photovoltaic cells (OPVs) fabricated on flexible polyethylene naphthalate (PEN) substrates using poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thio-hene)-2-carboxylate-2-6-diyl)] and [6,6]-phenyl C71-butyric acid methyl ester blend film as a photoactive layer. The photoconversion efficiency (PCE) of 5.92% was observed when using the sol-gel derived ZnO ETL, and was lower than that of reference device on a glass substrate (9.51%). In addition, a light soaking effect (LSE) and a relatively flat ZnO film surface were observed only the case of PEN substrate. This indicates that large number of defects in ZnO were generated due to the slow polycondensation speed of the sol-gel precursor solution when the PEN substrate was used and the carrier transport is inefficient. By using the nano-particle ZnO and the poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) as ETLs, the short circuit current density and fill factor were improved due to the reduced LSE compared when the sol-gel derived ZnO film was used. This result indicates that one reason of inferior OPV characteristics with the sol-gel derived ZnO ETL comes from the inhibition of electron transport/extraction due to the incomplete ZnO structure. As a result, we realized the highest PCE of 8.71% on the flexible PEN substrate.

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  • Tamotsu Minamitani, Toshiyuki Ueno
    2018 Volume 138 Issue 8 Pages 435-440
    Published: August 01, 2018
    Released: August 01, 2018
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    As the performance of modules improved and the Internet became widespread, various electric appliances in daily life became connected to the Internet. Along with this, related to the method of supplying power to the module, attention is being paid to energy harvesting such as vibrational power generator. A magnetostrictive vibration generator comprising a magnetostrictive material (Fe-Ga alloy) and a vibrating material is a promising device capable of generating small size and high power. However, selection of the optimum vibration material and analysis of the magnetic circuit for the magnetic characteristics of the Fe-Ga alloy were insufficient, and it was thought that the vibration power generation device could not fully demonstrate the performance. In this paper, magnetic properties of monocrystalline Fe-Ga alloy and vibrating material are grasped and magnetic analysis using finite element method is carried out. In addition, actually samples were prepared and compared with the results of magnetic analysis. From this result, we examined the effect of combinations of materials on device performance.

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  • Norimitsu Takamura, Nobutaka Araoka, Seiya Kamohara, Yuta Hino, Takuya ...
    2018 Volume 138 Issue 8 Pages 441-448
    Published: August 01, 2018
    Released: August 01, 2018
    JOURNALS RESTRICTED ACCESS

    We investigated the fundamental insulation characteristics of pure water using a negative lightning impulse voltage. The breakdown characteristics of pure water were similar between the up-and-down test and the progressive stress test. The breakdown strength of pure water was equal to or greater than the minimum breakdown strength required for insulating oil. The polar effect was confirmed in the breakdown characteristics of pure water due to the difference in electrode composition. In addition, the average breakdown voltage of pressurized pure water was approximately 1.3 times higher than that of non-pressurized pure water. The standard deviation of pressurized pure water was approximately 30% lower than that of non-pressurized pure water. These results were similar to those of insulating oils, which suggests that the breakdown of pure water was considered to be caused by the bubble theory.

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