Faculty Profiles - KODAMA Naoto

Papers - KODAMA Naoto

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電気接点の摺動・開離における電流減少プロセスの理論計算―転流回路インダクタンスに対する残留電流の依存性―

川端大海，横水康伸，兒玉直人，渡邉幹太，福塚隆司

電気学会研究会資料放電・プラズマ・パルスパワー/開閉保護/高電圧合同研究会 2021.11

珪砂-Silicone材併用時のDCアーク抵抗上昇効果の検討

竹中湧，兒玉直人，中村晃也，横水康伸，山村直希

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2021.7

N2/O2/HFO-1336mzz(E)混合ガスにおける衝突電離係数・電子付着係数および臨界電界—温度1500 K，HFO-1336mzz(E)混合率0~20%

杉田武弘，横水康伸，兒玉直人，中村泰規，佐藤基宗

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2021.7

SiC-MOSFETの熱インピーダンスの過渡特性を表すCauer型等価熱回路の構築:パワー半導体を用いた低電圧DC遮断器への適用

渡邉幹太，横水康伸，兒玉直人

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2021.7

Increasing Arc Column Resistance During DC Arc-Quenching Through Arrangement of Polymer Cylinder in Silica Sand Reviewed

Nakamura, K; Kodama, N; Yokomizu, Y; Takahashi, A; Kondo, Y

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING Vol. 16 ( 6 ) page： 905 - 915 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEJ Transactions on Electrical and Electronic Engineering

In this study, experiments pertaining to direct current (DC) interruptions are performed in an arc-quenching chamber filled with silica sand. First, the arc column resistance is measured during DC arc-quenching to demonstrate the elementary aspects of the arc in the silica-sand-filled space. Subsequently, an arrangement comprising a polymer cylinder between electrodes in the silica-sand-filled space is proposed to increase the arc column resistance during DC arc-quenching. A polymethyl methacrylate (PMMA) cylinder is used in the experiments. Measurement results indicate that the arrangement of the PMMA cylinder causes the arc column resistance to increase approximately twofold in comparison with the no-PMMA cylinder arrangement. Finally, the effect of increasing the arc column resistance is discussed in terms of PMMA and silica vapor. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

DOI： 10.1002/tee.23368

Web of Science

Scopus

Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF6 and ablation products of C2F4/BN in the temperature range of 300-3000 K Reviewed

Yokomizu, Y; Terada, M; Kodama, N; Ishii, T; Kojima, Y; Kuroda, M; Urai, H

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 54 ( 16 ) 2021.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics D: Applied Physics

For a high voltage SF6 circuit breaker equipped with a boron nitride (BN)-filled polytetrafluoroethylene ((C2F4)n nozzle, the predominant reaction products in a high-temperature SF6 mixture with vapor decomposition of C2F4 and BN at temperatures of 300-3000 K are determined based on calculations of equilibrium composition. The calculation is performed by considering the molecular products obtained by chemical reactions with boron atoms (e.g. BN, BS, BC, BF, BF2 and BF3), nitrogen atoms (e.g. N2, N3, CN, NS, NF, NF2 and NF3) and carbon atoms (e.g. CS, CS2, C2F4, CF2, CF3 and CF4). The results obtained for the C2F4-BN molar fraction X CFBN of 20%-80% reveal that BF3, N2 and CF4, the molecules originating from the nozzle material, are produced at high molar fractions over a range of 300-3000 K. Such an evaluation of the gas composition allows the derivation of a reduced collision ionization coefficient α/N and a reduced electron attachment coefficient η/N of the gas, considering various electron impact processes such as BF3 + e BF2 + F- and CF4 + e CF3 + F-. The evaluation subsequently enables us to determine a critical reduced electric field strength causing . The results suggest that the decomposed C2F4-BN mixture at XCFBN of 80% causes the reduction of to 110 Td in the range of 1000-2000 K at a gas pressure of 1.0 MPa. This strength is 20 Td lower than that determined separately for the SF6 gas mixture with only 80% C2F4 vapor decomposition, because of the CF4 molar fraction reduction in the SF6/C2F4-BN mixture.

DOI： 10.1088/1361-6463/abda80

Web of Science

Scopus

Interpretation of Arc Column Resistance Rise on basis of Temperature and Cu Vapor Concentration of DC Arc Established in Silica Sand Filling Space

Kodama Naoto, Yokomizu Yasunobu, Takahashi Asato, Nakamura Koya, Yamamura Naoki

IEEJ Transactions on Power and Energy Vol. 141 ( 11 ) page： 725 - 733 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

DC arc interruptions were carried out under following two conditions: (1) silica sand filling without any cylinder arrangement (designation: Silica), and (2) The silica sand filling with a quartz cylinder arrangement (designation: SilicaQuartz). During these experiments, optical emission spectroscopy (OES) measurements were carried out to investigate an arc column resistance rise by the quartz cylinder arrangement. An arc temperature T and a Cu vapor concentration were evaluated from the OES results. As a result, T were measured to be around 24 kK for the Silica condition and 17kK for the SilicaQuartz condition at a current peak. The Cu vapor concentration under the Silica condition gradually decreased with T decaying. On the other hands, the quartz cylinder arrangement in the silica sand filling space drastically decreased the Cu vapor concentration during an arc-quenching process. This drastic decrease in the Cu vapor concentration is one of key factors to increase rcol under the cylinder arrangement in the silica sand filling space. This verification result can be useful to increase an interruption capacity of fuse.

DOI： 10.1541/ieejpes.141.725

Scopus

CiNii Research

High Temperature Properties of CO2 Gas Mixture with O2 and HFO-1234yf Decompositions: Predominant Molecular Products and Critical Electric Field Strength at 300-3000 K

Yokomizu Yasunobu, Kodama Naoto, Sugita Takehiro, Ishii Tatsuya, Sato Motohiro, Nakamura Yasunori

IEEJ Transactions on Power and Energy Vol. 141 ( 11 ) page： 700 - 711 2021

Language：English Publishing type：Research paper (scientific journal) Publisher：The Institute of Electrical Engineers of Japan

The gases used in high voltage electric power equipment are required to withstand against an externally applied electric field strength. It is therefore essential to find out the electrical insulation strength of the gas. However the high temperature gas formed after the current zero through the arc extinction process in a circuit breaker shows different insulation strengths from that at room temperature, because the high temperature gas consists of various molecular products different from the original gas at room temperature. The CF3CFCH2 (called as HFO-1234yf) at room temperature is known to have a remarkable electrical insulation property similar to SF6. After describing the products generated in CO2 gas mixture with O2 and HFO-1234yf decompositions at temperatures below 3000K, this paper mentions dielectric breakdown properties of the mixtures in view of the molar fractions of the molecular products. Discussions are furthermore made to compare dielectric breakdown properties of CO2 gas and CO2/O2 gas mixture at high temperatures.

DOI： 10.1541/ieejpes.141.700

Scopus

CiNii Research

Characteristic Analysis of Thermal Plasma Formed Inside Power Protection Equipment and Development of DC Protection Device Invited Reviewed

Naoto Kodama

Vol. 45 ( 3 ) page： 112 - 113 2021

DC arc resistance rise by PMMA cylinder ablation with arc shrinking in silica-sand filled space

Koya Nakamura,Naoto Kodama,Yasunobu Yokomizu,Naoki Yamamura

The Papers of Technical Meeting, IEEJAPAN　12nd International Workshop on High Voltage Engineering (IWHV2020) 2020.11

珪砂を用いた直流遮断過程におけるアーク内銅蒸気の二次元分布観測と濃度に関する検討

兒玉直人，横水康伸，中村晃也，高橋明里，山村直希

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2020.9

C3H2F4を混合した代替消弧ガスCO2/O2: 8%混合率，温度300-3000 Kにおける衝突電離・電子付着係数および臨界電界

杉田武弘，横水康伸，兒玉直人，石井達也，佐藤基宗，中村秦規

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2020.9

Chemical species produced in arc-quenching gas CO2/O-2 mixed with C3H2F4, C4-FN or C5-FK: prevention of condensed-phase carbon formation and its formulation Reviewed International journal

Yokomizu Y, Sato M, Kodama N, Edo T, Kokura K

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 53 ( 14 ) 2020.4

珪砂中への円筒設置時における直流アーク温度の測定とアーク電圧上昇機構の検討

兒玉直人，横水康伸，中村晃也，高橋明里，近藤祐介

電気学会研究会資料放電・プラズマ・パルスパワー/開閉保護/高電圧合同研究会 2019.12

Approach to Mechanism Interpretation of Arc Voltage Rise by Polymer Cylinder Installation in Silica-Sand Reviewed International journal

Kodama N, Yokomizu Y, Nakamura K, Takahashi A, Kondo Y

Proceedings of the 2019 5th International Conference on Electric Power Equipment - Switching Technology: Frontiers of Switching Technology for a Future Sustainable Power System, ICEPE-ST 2019 page： 243 - 248 2019.10

Authorship：Lead author,　Last author,　Corresponding author Language：English Publishing type：Research paper (international conference proceedings) Publisher：Proceedings of the 2019 5th International Conference on Electric Power Equipment - Switching Technology: Frontiers of Switching Technology for a Future Sustainable Power System, ICEPE-ST 2019

This report describes experimental results on DC interruption for three experiments: (1) silica-sand filling (designation: Silica), (2) polymer cylinder installation without silica-sand filling (designation: P5-Air), and (3) polymer cylinder installation with silica-sand filling (designation: P5-Silica). The shape of polymer cylinder was fixed at an inner diameter of 5 mm and a length of 15 mm. A damping DC with a peak current of 750 A was supplied to an established experimental system. A current and a voltage between electrodes were measured during the current supplying period. As experimental results, the arc resistance between electrodes were measured to be 0.15 for Silica, 0.20 for P5-Air and 0.56 for P5-Silica at a peak current, respectively. This implies that silica-sand confined in the polymer cylinder effectively contributes to the arc voltage rise at around a peak current. During a current decaying periods, the arc resistance for P5-Air was measured to be almost same value for P5-Silica. This also implies that an interaction between the polymer and the arc rises the arc resistance during the current decaying period.

DOI： 10.1109/ICEPE-ST.2019.8928816

Scopus

Rise Effect of DC Arc Voltage in Silica Sand: Various Interelectrode Distances and Arrangement of PA66-Cylinder

Takahashi A., Kodama N., Yokomizu Y., Kondo Y.

Publisher：Proceedings of the 2019 5th International Conference on Electric Power Equipment - Switching Technology: Frontiers of Switching Technology for a Future Sustainable Power System, ICEPE-ST 2019

The following three experiments were conducted as an attempt to raise the DC arc voltage during current interrupting process in silica sand. The purpose of the first experiment is to examine the influence of the interelectrode distance of the graphite electrode on the arc length. The three types of interelectrode distance were set in the arc quenching chamber and supplied a damping DC current. As experimental results, voltage between electrodes was not effectively rose with elongation in interelectrode distance in the silica sand. The purpose of the second experiment is to achieve further rise in the arc voltage. In this experiment, PA66-cylinder was arranged between electrodes. As the experiment result, arrangement of PA66-cylinder effectively increases the arc voltage. This may be because the expansion of the arc diameter was restricted to the interaction between the arc and the inner wall of the cylinder. The purpose of the third experiment is to investigate the influence of arc voltage rise effect on the inner diameter of the cylinder. The main factors causing the arc voltage rise are the effect of limiting the arc diameter by the inner diameter and the effect of ablating of silica sand.

DOI： 10.1109/ICEPE-ST.2019.8928782

Scopus

珪砂-高分子円筒併設時の直流アーク抵抗上昇機構に関する検討

中村晃也，兒玉直人，横水康伸，高橋明里，近藤祐介

電気学会研究会資料放電・プラズマ・パルスパワー/静止器/開閉保護合同研究会 2019.7

Fundamental study on role of silica-sand and polymer cylinder in terms of gas properties during DC interruption Reviewed

Kodama N., Yokomizu Y., Takahashi A., Nakamura K., Kondo Y.

Proceeding of XXXIV International Conference on Phenomena in Ionized Gases/ 10th International Conference on Reactive Plasmas 2019.7

Efficient modification of Si/SiOz nanoparticles by pulse-modulated plasma flash evaporation for an improved capacity of lithium-ion storage Reviewed International journal

M.Kambara, S.Hamazaki, N. Kodama, Yasunori Tanaka

Journal of Physics D: Applied Physics Vol. 52 ( 32 ) page： 325502 2019.7

Spatial distribution of Ti vapor admixture ratio in Ar induction thermal plasma torch during Ti feedstock injection Reviewed

Naoto Kodama, Yasunori Tanaka, Yosuke Ishisaka, Kotaro Shimizu, Yoshihiko Uesugi, Tatsuo Ishijima, Shu Watanabe, Shiori Sueyasu, Keitaro Nakamura

Japanese Journal of Applied Physics Vol. 57 ( 3 ) 2018.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Applied Physics

The spatial distribution of the Ti vapor admixture ratio (X Ti) was determined together with Ti excitation temperature () from two-dimensional (2D) optical emission spectroscopy (OES) during Ti feedstock injection into an Ar induction thermal plasma (ICTP) torch for Ti nanoparticle synthesis. The X Ti is one important parameter affecting ICTP properties such as its electrical conductivity. The value of X Ti was estimated from the radiation intensity ratio of the Ar atomic line to the Ti atomic line, and obtained from 2D OES observation. Furthermore the electron density (n e) was also determined from the estimated results of and X Ti through the equilibrium composition. These 2D OES results revealed as 2500-4000 K at around the central axis of the ICTP torch, although it was higher than 4000 K in the off-axis region. In the off-axis region, X Ti and n e were much higher than in the on-axis region.

DOI： 10.7567/JJAP.57.036101

Scopus

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Papers - KODAMA Naoto