Title —Ž—‹“dŠE”gŒ`’·ŽžŠÔ‹L˜^‘•’u‚ÌŠJ”­‚ÆŠÏ‘ªŒ‹‰Ê
Author(s) ‰Íè, ¼‰Y, ŽR–{, ’·’J, ’†“c, ’‡–ì, ’|“à
Journal “d‹CŠw‰ï˜_•¶ŽB, 111, 5, 521-528 (1991)
Abstract A new transient memory, which has 1 Mbytes buffer memories and can record the electric field changes due to lightning discharges for at most 524 mill seconds, is designed to study the whole process of the lightning discharge. To realize the system, a commercially available personal computer and a memory board are used and the special software is also developed. As the sensor, a new type slow antenna, which maintains the features of both so called slow antenna and fast antenna, is also manufactured. The system itself is controlled by the personal computer, and then without any manual operation the observation can be carried out. With this system the observations during both summer and winter thunderstorm seasons were performed. During summer the system recorded the electric field changes with multi strokes and continuous current. During winter it recorded the whole process of lightning discharges from the preliminary breakdown through the return stroke, and continuous current. The utility of the system can be approved and some remarkable features of lightning discharges are obtained.

Title —Ž—‹“dŽ¥ŠE‚Ì100kHz - 1MHzƒt[ƒŠƒGƒXƒyƒNƒgƒ‹‚Æ‘å’n“±“d—¦
Author(s) ‰Íè, ¼‰Y, ’‡–ì, ’|“à
Journal Res. Lett. Atmos. Electr., 11, 11-22 (1991)
Abstract The electric and magnetic fields caused by the lightning discharge have been observed. The Fourier spectra of them are calculated by using FFT and the influence of the propagation over land is discussed from the view point of statistics. Finally the conductivity and permittivity of the ground are estimated by applying Norton's formula to the estimated Fourier spectra.

Title “dŽ¥”g‹óŠÔˆÊ‘Š·–@‚ð—p‚¢‚½”ñÚG•”•ª•ú“dŒŸo–@
Author(s) ì“cA‰ÍèA¼‰YAìè
Journal “d‹CŠw‰ï˜_•¶ŽB, 115, 10, 1168-1173 (1995)
Abstract A new method is presented for detecting an occurrence of the partial discharge (PD) in a high-voltage electrical apparatus due to a dielectric material defect. This method uses the phase information of electromagnetic waves propagated through space. In case the electromagnetic wave due to an internal PD is to be measured when an electrical power apparatus is operating, the signal to noise ratio poses a problem to discuss. The mean power of the background noise is normally higher than that of the signal of interest, and the signal tends to be lost in the background noise. And it is important to develop a non-contact method for detecting the insulation fault. This paper experimentally shows that our proposed "spatial phase difference method" is able to apply to identification of electromagnetic waves due to PD. This method is shown to be useful for detecting prediction of insulation fault.

Title V‚µ‚¢‚Žü”gƒgƒ‰ƒ“ƒXƒŠƒ“ƒNƒ\ƒtƒgƒXƒCƒbƒ`ƒ“ƒOPWM DC-DCƒRƒ“ƒo[ƒ^‚ÆŠJƒ‹[ƒv“Á«
Author(s) “¹•½, ’†‰ª, •ÄX, M–Ø, ‰Íè, ¼‰Y
Journal “d‹CŠw‰ï˜_•¶ŽD, 116, 5, 546-555 (1996)
Abstract In the practical requirement for high-efficiency, high power density and high-performance in the switched-mode power supplies and their related application systems, a variety of circuit topologies of DC-DC converters incorporating soft-switching PDM, PFM and PWM control schemes have attracted special interest in the fields of low power and high power applications. Some types of quasi-resonant soft-switching PWM converters have remarkable advantages such as lowered switching losses of power semiconductor devices, reduced dynamic electrical stresses, constant frequency operation, simple control scheme as well as reduced EMI noise. However, most of soft-switched quasi-resonant PWM converters developed so far include some inherent items which have to be solved such as reduced power conversion efficiency due to significant circulating current generation. In recent years, the newly modified prototype of soft-switched PWM DC-DC converter with a high-frequency transformer link has been proposed, which is capable of excluding circulating current operation mode. This paper presents a novel high-frequency transformer link soft-switching PWM DC-DC converter using active switches in rectifier circuit. Its operating principle and unique features are described as compared with the previously developed DC-DC converter. Operating performance of this converter in steady-state are illustrated and discussed including the simulated analytical and experimental results.