Faculty Profiles - KODAMA Naoto

Papers - KODAMA Naoto

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High-temperature properties of dry air used as arc quenching medium and its mixture with vaporized C<inf>2</inf> F<inf>4</inf> : reaction products and critical reduced electric field strength at 300-3000 K

Yokomizu Y., Kodama N., Yamamoto I., Uchiyama S., Sato M., Nakamura Y., Edo T.

Journal of Physics D: Applied Physics Vol. 57 ( 21 ) 2024.5

Publisher：Journal of Physics D: Applied Physics

Recently, electric power equipment manufacturers released a joint statement with the aim of developing high-voltage electrical equipment completely free of fluorinated gases such as fluoroketones and fluoronitriles, which are considered as alternatives to S F 6 and artificially produced compounds of F. This paper considers air as a typical gas present naturally in the environment to investigate its high-temperature properties, including an air mixture with C 2 F 4 vapor injected from a polytetrafluoroethylene nozzle, for application as an arc-quenching medium in a high-voltage circuit breaker equipped with a nozzle. Chemical composition results for the reaction products at 300-3000 K show that the admixture of C 2 F 4 vapor causes a decrease in the molar number of O 2 contained in the air, owing to the production of O-containing compounds such as C O 2 and C O . Additionally, the results reveal that the admixture of C 2 F 4 vapor lead to the production of C F 4 as the predominant F-containing compound. Furthermore, the boundary condition for O 2 production in terms of O 2 molar number X O 2 and C 2 F 4 molar number X C 2 F 4 is formulated. Such evaluation of the mixture composition enables the determination of a reduced effective collision ionization coefficient α ˉ / N and a critical reduced electric field strength E c r / N , resulting in α ˉ / N = 0. The strength E c r / N for the mixture with 30%-100% C 2 F 4 molar fraction rises to approximately 150 Td (1 Td = 1 × 10 − 21 V m2) over 300-3000 K, which is 20-50 Td higher than that for high-temperature air unmixed with C 2 F 4 vapor. The variation in E c r / N is discussed in terms of predominant electron impact processes and the electron energy distribution function in the mixture.

DOI： 10.1088/1361-6463/ad2a15

Scopus

Development of Electrical Circuit Protection DeviceBased on Gas Properties Analysis of High-Temperature Arc and Hot Gas Invited Reviewed

Naoto Kodama

Proceeding of ISPlasma2024/IC-PLANTS2024/APSPT13 2024.3

Spatiotemporal evolution of electrical conductivity in current-limiting-fuse arc Reviewed

Inada, Y; Fukai, Y; Takayasu, N; Nakano, Y; Zen, SG; Ohnishi, W; Yamano, Y; Maeyama, M; Kodama, N

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 56 ( 50 ) 2023.12

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

To improve the interruption capacity of a current-limiting fuse, a detailed diagnosis of the spatial electrical conductivity distribution inside the fuse arc under the current limiting phase around current zero is required, because this distribution determines the distribution of transient recovery voltage inside the fuse. However, well-established methodologies applicable to fuse arcs are lacking, so the spatial distribution remains unknown. This study presents a borescope-integrated spectroscopic system that simultaneously obtains single-shot recordings of the axial distributions of the electron density and arc temperature in the fuse arc just before extinction. Combining the electron densities and arc temperatures, we can identify the fuse arc composition and hence calculate the axial electrical conductivity distribution under the first Chapman-Enskog approximation. The electrical conductivity provided by this systematic methodology includes no large uncertainties, thus demonstrating its superiority against previous estimation methods of the electrical conductivity.

DOI： 10.1088/1361-6463/acf9b2

Web of Science

Scopus

Direct current arc quenching performance of a model electric fuse equipped with SiO<sub>2</sub> sand and additive silicone resin as an arc quenching medium: the effect of a vaporized silicone decomposition mixture on transient arc resistance Reviewed

Takenaka, W; Kodama, N; Yokomizu, Y; Nakamura, K; Shimizu, H

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 56 ( 47 ) 2023.11

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

Most high-power electric fuses installed in DC distributions of automobiles employ silica sand (chemical formula SiO2) as arc quenching material to implement the limitation and subsequent interruption of high direct currents. This paper on arc quenching material describes the effects of the addition of silicone resin (chemical formula C2H6SiO) on SiO2 sand, based on the resistance of an arc discharge in SiO2 vapor mixed with silicone resin vapor. The measurement results obtained for the fuse operation of a model electric fuse show that the addition of silicone resin, e.g. an even coating of silicone resin on the surface of a Cu fuse element, attains a shorter arc quenching time. This phenomenon is subsequently explained based on the rise effect of an arc column resistance achieved by mixing with silicone vapor decomposition. The chemical compositions of high-temperature SiO2 vapor mixed with C2H6SiO vapor decomposition are evaluated to show the predominant chemical species at 30 000 K-5000 K for several C2H6SiO vapor concentrations, X C H . The results obtained for X C H of 10%-50% reveal that a H atom originating from C2H6SiO is present at high molar fractions above 0.1 over a wide temperature range of 12 000 K-5000 K. Further evaluations of the electrical resistivity ρ R for the high-temperature vapor show that mixing with C2H6SiO vapor contributes to a rise in ρ R at temperatures of 10 000 K-6000 K. A contribution analysis of the ρ R reveals that the rise effect of the ρ R is accomplished chiefly by the presence of a H atom that has dissociated from C2H6SiO.

DOI： 10.1088/1361-6463/acee92

Web of Science

Scopus

高温ドライエアへの高分子分解蒸気混入による反応生成物および耐電界特性 -高分子材C2F4あるいはC6H4S-

山本伊織, 横水康伸, 兒玉直人, 内山隼輔, 佐藤基宗, 中村泰規, 江戸貴広