Katsuhiko Yoshida
Toshiba
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Featured researches published by Katsuhiko Yoshida.
IEEE Transactions on Electrical Insulation | 1981
Hisayasu Mitsui; Katsuhiko Yoshida; Y. Inoue; K. Kawahara
Several kinds of insulation systems, which were developed for high voltage coil insulation for motors and generators, are examined for insulation damage caused by mechanical stresses. Tests have been carried out on electrical properties under bending stress, i. e. the critical deformation characteristics which are defined as the maximum deformations able to withstand a fixed proof voltage, the fatigue characteristics under repeated bending stresses, and the voltage life characteristics under bending stress. Breakdown voltage, BDV, decreases with an increase of bending stress. Moreover, a remarkable increase of the base tan6 value, tan6o, and tan6 tip-up can be seen due to the delamination of mica-splittings, especially in the case of the insulation using mica splitting. An insulation system in which a flexible binder is used has a far greater critical deformation. The decrease of residual breakdown voltage RBDV, and the increase of tan6o and tan6 tip-up are seen at less repeated bending stress in the insulation system with mica-splitting tapes than in the insulation system with only mica-paper, because of the weakness of mica-splittings under repeated bending stress. Effects of the temperature on the repeated bending fatigue characteristics from -55 to 1550C are greatly influenced by the binder of the mica tape and/or the impregnating resin. Moreover, voltage life under a static bending stress becomes extremely short beyond a certain stress. Lastly, experimental equations are proposed for estimating the relationship between RBDV and the numbers of repeated bending cycles, and the voltage life under a static bending stress.
IEEE Power & Energy Magazine | 1983
Hisayasu Mitsui; Katsuhiko Yoshida; Y. Inoue; S. Kenjo
Thermal cyclic degradation of epoxy micaceous insulation for ac high voltage generators and motors was investigated. From the experimental results, it is made clear as follows. Thermal cyclic degradation begins with a separation of the innermost main insulation layer from the strand insulation at the end of the iron core. It propagates in a mode of mica delamination and the formation of cracks. This degradation condition agrees well with the measurement results of non-destructive insulation tests using divided electrodes. The compatibility between a strand insulation and a main insulation greatly affects thermal cyclic degradation. Thermal degradation cannot be ignored under certain thermal cycle condition. Thermal cyclic degradation increases with an increase in the peak conductor temperature. Even in the case of a post impregnated insulation system where the coil insulation adheres to the iron core, the thermal cyclic degradation is little for a core length below 1.4 m and a 160 °C hottest conductor temperature. Non-destructive insulation diagnoisis of hydrogen filled water-cooled turbine-driven generator insulation shows little thermal cyclic degradation after approximately 15 years normal operations. Lastly, it is proposed that a thermal cylce test under voltage application is important hereafter, to grasp the degradation of actual machines precisely.
IEEE Power & Energy Magazine | 1981
H. Terase; Hisayasu Mitsui; Y. Inoue; Katsuhiko Yoshida; S. Kenjo
Gap or void discharge and Creeping discharge were measured in several kinds of gases at different pressures with model specimens, such as a gap model between two parallel plates of glass, a model of single plate of glass, epoxy-mica insulation coils, and a motorette degraded by a series of functional test., From the experimental results, it is made clear that discharges in open type (ventilated) void and creeping discharges are remarkably suppressed with increasing the gas pressure, and discharges in high voltage rotating machine winding are also suppressed in compressed gas due to the transition of included voids from closed type to open type. The latter was confirmed by the measurements of a turbine generator after long service. These effects are most distinguished in SF6 gas and hydrogen gas above 1.5 atg was superior in the discharge suppression effect to the air at O atg. Moreover, the breakdown voltage of epoxy mica insulation containing many ventilated voids rises remarkably with increasing gas pressure, approaches to that of epoxy vacuum-pressure impregnated coil when SF6 gas at 6 atg is filled. Based on these data, the authors proposed the availability of GF (gas filled) insulation system in the rotating machine.
IEEE Power & Energy Magazine | 1983
Hisayasu Mitsui; T. Tanii; Katsuhiko Yoshida; S. Kenjo
Motorette test based on IEEE Std. 275 have been usually adopted as a thermal evaluation method for rotating machinery insulation. There are some problems in performing thest tests. The tests required a considerably time. And, as the tests predict the life at an operational temperature by an extraporation method based on the data at higher temperatures, there is a possibility of missing a change in the temperature dependence of the thermal degradation mechanism. Therefore, the thermal life evaluation method by an EGA-GC (Evolved Gas Analysis-Gas Chromatograph) was examined in comparison with the motorette test method.
Archive | 2003
Katsuhiko Yoshida; Noriyuki Iwata; Hiroshi Hatano; Susumu Nagano; Shinobu Sekito; Toshimitsu Yamada; Makoto Kawahara
Archive | 2001
Fumiko Sugano; Daisuke Taguchi; Katsuhiko Yoshida; 勝彦 吉田; 大介 田口; 富美子 菅野
Archive | 2002
Katsuhiko Yoshida; Noriyuki Iwata; Hiroshi Hatano; Susumu Nagano; S. Esute-City-Shonan-Mutsuura Sekito; Toshimitsu Yamada; Makoto Kawahara
Archive | 2008
Hiroshi Hatano; Katsuhiko Yoshida; Toshimitsu Yamada; Shinobu Sekito; Susumu Nagano; Hiroyoshi Tsuchiya
Archive | 2002
Takashi Sato; Katsuhiko Yoshida; 隆 佐藤; 勝彦 吉田
Archive | 2001
Hiroshi Hatano; Noriyuki Iwata; Makoto Kawahara; Susumu Nagano; Shinobu Sekido; Toshimitsu Yamada; Katsuhiko Yoshida; 勝彦 吉田; 利光 山田; 憲之 岩田; 浩 幡野; 誠 河原; 進 長野; 忍 関戸