Power electronics today is one of a wide range of well defined technologies. It has a key role in the transformation and adaptation of electrical energy between the supplier and the user. The object of this paper is to review the history of power electronics in Japan. Considering general trend, important researches and epoch-making new products are listed in several important areas. Technical events from overseas, which caused great impacts in Japan, are also cited.

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This paper studies the history of high voltage circuit breaker engineering. Methods of analysis are (1) to collect facts in regard to its development, (2) to review the history in order to find essential factors and (3) to identify its pros and cons from engineering point of view.
The tool of analysis is "Stage Model";which is commonly used in the historical study of engineering. As the result, it is found that the engineering of gas circuit breakers is supported by unique technology developed in Japan due to her geographical conditions and social needs.

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The Senju (Thermal) Power Station was constructed by the Tokyo Electric Light Company in 1925 as an auxiliary/emergency plant that supplements the needs of the hydroelectric power plants.Since 1929, the company has successfully operated three 25, 000 kVA Turbo-Generators as synchronous condensers at the Senju Power Station. The generators at the Senju Station produce electrical energy for half of the year.
For the remaining half of the year, they are disconnected from turbines and run as synchronous condensers. Used this way, these machines perform double duty. One reason for this arrangement was that the greater capacity of the synchronous condenser was required for the high water season.A second was economic benefits.
After the success of the Senju Station, more than 40 utility Turbo-Generators in Japan were altered for use as synchronous condensers, and others were designed and constructed specifically for this purpose. The use of Turbo-Generators as synchronous condensers was an original development of the Japanese electric power companies.
This note provides an overview of alterations made to the generators at the Senju Station.

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This paper studies the history of power systems engineering in Japan, collecting the fact and analyzing them with the Stage Model. The power systems engineering is a kind of software technology which could be identified as the reflection of its society and culture. Its history will be studied with papers and books in the field. The power systems in Japan were composed without much delay from that in Europe and America. Its development in quality is remarkable due to the high economic growth and the needs of high reliability in Japan.
This paper confirms how the "flexibility"; is needed and established for the power systems engineering. The reason is that the power systems are affected seriously by the social and economic circumstances of the region they are located and that the society and economy in the region will be continuously changing. The paper suggests that the analysis of historical facts in power systems in Japan will provide Japanese power systems engineer with the sound objective of their R & D activity that is the study of "flexibility"; from social, economic and historical point of view. In this manner the historical study of engineering will make engineering improved and refreshed so that it faces the new century and that it creates an ever brighter future.

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Research and development of electronic computers started in late 40's in Japan. After the invention of transistors in the US and parametrons in Japan, laboratories and manufacturers started developing computers using transistors or parametrons as logical elements. Therefore only four vacuum tube computers were manufactured in Japan. These are Electronic Computer at Osaka University, FUJIC of Fuji Photo Film Company, TAC of University of Tokyo and ECL RTC. Though the first generation of computers was rather short in Japan, the technical contribution of the development of vacuum tube computers is valuable. This paper reviews the development efforts of the former two vacuum tube computers, Osaka University's and FUJIC.

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As for the protection relay, the innovations of relay technology was accomplished for 30 years leaping-ly. This relay technology innovations corresponded to the expansion of the electric power system are accomplished by the foresight.
In the composition of the protection relay equipment, it improved from the mobile contact-type relay of electromagnetic power to the solid state-type relay and moreover the technology was innovative at the digital-type relay by MPU. Then, the innovations of this hardware technology could be achieved by the establishment of the technology which make relay systems a high degree of the reliability by automatic and watching over equipment itself. On the other hand, because the innovations of this relay hardware technology could leave out the limitation of the protection relay function, it brought about the innovations of the software technology which protect bulk power systems to a high degree. The protection relay technology in Japan is the technology which have been most advanced in the world and is the technology which fitted in with the Japanese state of the affairs. As for this paper, it introduces the outline about the contents of the technology innovations and the big results of the technology innovations.

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The experimental investigations of the discharge characteristics of planar type surface wave prosessing plasmas(SWP) have been carried out. On this apparatus, the efficiency of microwave power absorption into the plasma depends strongly on the thickness of the dielectric window. Especially at the thickness of 12mm, it has been found that more than 80% of microwave power is absorbed into the plasma. In order that the uniform power absorption is brought about effectively in a wide range of gas pressure, the dielectric waveg-uide that is placed above the dielectric window needs the air gap between them. These experimental results will enable us to improve the apparatus configuration to achieve better operational performances of surface wave plasmas.

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Plasma CVD is widely used for deposition of hydrogenated amorphous silicon (a-Si:H) based materials. To obtain desired properties of deposited film in this technique, controllable parameters such as gas pressure, gas flow rate and discharge power are varied empirically, and no precise simulation is so far available. Thus in this work, an analysis based on macroscopic model was developed to provide a tool to understand the relationship between those controllable parameters and the film properties such as germanium content in a-SiGe:H alloy films. The results were compared with some experiments, and it was shown that these are in good agreement.

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Photocatalytic TiO₂ Thin-films Deposited by Pulsed Laser Deposition Technique Masahiro Terashima, Non-Member(National Defense Academy), Narumi Inoue, Member (National Defense Academy), Shigeru Kashiwabara, Member (National Defense Academy), Ryozo Fujimoto, Member(Nippon Bunri University)Photocatalytic Tio₂ thin films have been prepared by the pulsed laser deposition (PLD) method and their crystalline and electrochemical characteristics have been investigated by X-ray diffraction (XRD) and electrochemical measurements. The results show that the anatase crystal is grown at lower substrate temperature than other deposition methods. The XRD data of the films are also studied as a function of the film thickness and the repetition frequency of laser pulse. At the substrate temperature of 300°C, the XRD peaks of anatase increase as film thickness increases. Also the XRD anatase peaks of the films deposited at high repetition frequency increase. These facts indicate that the temperature difference between the substrate and the surface of the growing film causes the change in crystalinity. From the results of electro-chemical experiment, on the other hand, it is found that the current density of the sample fabricated at the substrate temperature 100-200°C with the thickness of about 1 μm is the highest.

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We have investigated the effects of fabrication conditions on EL properties for organic light-emitting-diodes (OLED). The initial EL properties (luminance-current density-voltage) depended on the deposition rate of Alg3 but did not on TPD's. The half-life of OLED became shorter by the low deposition rate of Alq3 and the fast one of TPD.

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Influence of a crack in an insulator with a backside electrode upon AC breakdown voltage (BDV) was investigated in air. In the test insulator, the crack runs parallel with the plane backside electrode. The breakdown path from the HV electrode propagates through the crack to the counter electrode. The experimental results show that BDV depends upon the width of the crack in the area of the electrode distances longer than 50mm. In this area of the electrode distances, BDV decreases with a decrease in the width of the creak when the width is smaller than 500μm. For example, in the electrode distance of 120mm, BDV at 200μm of the crack width is about 0.85 times lower than that at 600μm of the width. The decrease in BDV for the width _??_500μm may result from the propagation of a positive surface leader. The positive leader propagates to the counter electrode before the breakdown only in the range of the width _??_500μm. The appearance of the positive leader may be due to the electric field enhancement by charge accumulated on the insulator surface in the crack. In the width _??_500μm, on the other hand, BDVs are almost independent of the width. The positive leader does not appear, but the negative leader appears significantly in the range of the width _??_500μm. It was observed in the range of the width _??_500μm that the propagation of the positive leader is longer than that of the negative leader. The decrease in BDV for the range of the width _??_500μm may result from the longer propagation of the positive leader through the crack.

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In order to investigate the deterioration of low-density polyethylene (LDPE) by partial discharge(PD), experiments were conducted in an air atmosphere containing oxygen. Specimens subjected to PD were examined by atomic force microscope (AFM) and Fourier transform infrared (FTIR) analysis. The AFM images revealed the generation of pits in the deteriorated LDPE specimens, and the FTIR spectra indicated that carbonyl compounds were produced due to the presence of oxygen during PD. It is suggested that the generation of pits by PD is greatly influenced by oxygen content in the atmosphere.

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An application that assists the beginners to learn logic circuits is proposed. A logic circuit is drawn by handling a mouse to select various logic elements provided with menu screen, and to connect them with lines on the display. When the timing simulation is executed, the operation situation of the making circuits are easily understood because from input end to output end they are displayed in red if it is true (1), and in blue if it is false (0). And then, by those timing charts the logic relations of the drawn circuits can be verified.

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Investigation of space charge distribution up to electrical breakdown is important for understanding electrical breakdown phenomena of polymeric insulating materials. Using the short interval pulsed electroacoustic method, a space charge distribution was measured on a 100μm thick low-density polyethylene (LDPE) film in high temperature region. In this paper, we report the change of the space charge distribution it thinks to influence the electrical breakdown phenomena at 90°C in LDPE film was measured.

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