Meidensha (Japan)

Many photovoltaic (PV) systems are installed in the distribution system, which complicates the voltage profile; voltage fluctuations due to PV cause frequent LRT and SVR operations and shorten equipment life. Therefore, we believe that voltage control can be achieved by understanding the voltage distribution in detail by estimating the state based on the information from the currently installed measurement devices. Using machine learning from the collected information, high-speed control can be achieved. Therefore, we propose a method to perform voltage control while considering the wear and tear of the devices using double DQN.

Series elastic actuator (SEA) is a combination of an actuator, a spring, and a load in series, and improves shock resistance and motion performance such as maximum torque and maximum speed compared to an actuator alone. In SEA, the spring accumulates the kinetic energy of the motor. The natural frequency can be lowered by increasing the moment of inertia by speed-up gear. By lowering the natural frequency, the time that large torque lasts in one direction can be increased. This study focuses on the miniaturization and weight reduction of SEA units. By integrating multiple functions into the components, we aim to develop a compact and lightweight SEA unit with improved versatility. We propose an SEA unit using a planetary gear reducer with integrated elasticity, which compresses the components by incorporating elasticity into the gear reducer.

Laporan keberlanjutan adalah laporan kinerja yang dibuat oleh perusahaan untuk mengukur, mengungkapkan, dan mengelola perubahan dalam rangka membuat kegiatan yang keberlanjutan. Peneliti menggunakan desain studi deskriptif dengan metode analisis isi secara kuantitatif dan kualitatif. Objek penelitian adalah 30 (tiga puluh) perusahaan yang konsisten menerbitkan laporan keberlanjutan disertai dengan pernyataan asurans dengan standar AA1000AS dan ISAE3000 periode tahun 2020 – 2022. Hasil penelitian menunjukkan tingkat kepatuhan berdasarkan gabungan elemen standar AA1000AS dan ISAE3000 berdasarkan total skor rata-rata secara kuantitatif berada pada tingkat 73% dan secara kualitatif berada pada tingkat 75%. Kesimpulan penelitian menunjukkan tingkat kualitas pernyataan asurans yang tinggi pada semua aspek berdasarkan penyedia jasa asurans, standar asurans yang digunakan, negara penelitian, tahun penelitian, perusahaan, dan sektor industri. Kata kunci : Kualitas, pernyataan asurans, laporan keberlanjutan

The accelerated testing methodology (ATM) developed by the authors is the methodology for predicting statistically long-term life of CFRP structures based on the viscoelasticity including the time-temperature superposition principle for matrix resin. The formulae of ATM are expressed as the product of static strength at room temperature, its dispersion, and the viscoelastic parameter of matrix resin that changes with time and temperature history. This methodology ATM was applied to the prediction of long-term creep failure life for unidirectional CFRP with heat-resistant epoxy resin as matrix under heat degradation in this study. Resin impregnated CFRP strands with heat-resistant epoxy resin were molded using a filament winding system as virgin specimens of unidirectional CFRP. Then, heat-degraded specimens were prepared by exposing the virgin specimens under acceleration conditions determined based on the time-temperature superposition principle for chemical deterioration assuming the condition of practical temperature 110°C and period 10 years. Second, the creep strengths of virgin and heat-degraded CFRP strands were statistically predicted based on ATM and the effect of heat degradation on the long-term life of CFRP strands was evaluated. As results, it was cleared that when the creep strength of CFRP strands undergoes thermal aging at the practical condition, in addition to the strength decrease to time due to the viscoelasticity of the resin, a comparable decrease in static strength and increase in this scatter occur.

Spark conditioning is an effective method of increasing the dielectric strength in vacuum. In this article, we discuss the breakdown (BD) charge dependence of counter electrode material adhesion and dielectric strength after spark conditioning. We have applied a negative impulse voltage to a rod-plane electrode configuration with a cathode and an anode made of stainless steel (SUS) that is defined as SUS304 by JIS G 4303 or oxygen-free high-conductivity copper (Cu). The electrode system of cathode SUS and anode Cu is called SUS–Cu electrode system, and the electrode system of cathode Cu and anode SUS is called Cu–SUS electrode system. We have changed BD charge ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {BD}}$ </tex-math></inline-formula> ) in conditioning by changing the limiting resistance in the experimental circuit. As a result, in both cases of SUS–Cu and Cu–SUS electrode systems, the larger the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {BD}}$ </tex-math></inline-formula> , the smaller the amount of the anode material adhered to the cathode surface. When <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {BD}}$ </tex-math></inline-formula> is large, the dielectric strength increases in SUS–Cu electrode system and decreases in Cu–SUS electrode system. From these results, when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {BD}}$ </tex-math></inline-formula> is large, we consider that the conditioning characteristics are less likely to be dominated by the anode material, i.e., Cu in the case of SUS–Cu electrode system and SUS in the case of Cu–SUS electrode system. In other words, the decisive parameters, such as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {BD}}$ </tex-math></inline-formula> to maximize the dielectric strength, may depend on the combination of electrode materials.

Replacing petrochemical-derived mineral oil with biodegradable bio-derived ester oil for the electrical insulating oil used in transformers has gained attention in recent years. In general, ester oil has a high saturated moisture content, and in the case of transformers, the residual moisture of both the conductor-coated insulation paper and pressboard is transferred into the ester oil, thereby suppressing the degradation of the solid insulation. Therefore, they are expected to extend the lives of transformers. The insulation properties of three types of biodegradable insulating oil were investigated using an inter-section insulation model of transformer windings, simulating the case of a lightning impulse applied to an oil-immersed transformer. As a result, V-t characteristics were obtained, in which the dielectric breakdown characteristics improved with the applied short tail of the lightning impulse waveforms. The dielectric breakdown voltages at room and elevated temperatures showed a large difference in the dispersion of the measured data, although the average values and V-t characteristics were almost the same. We further analysed the data using the Weibull probability distribution and compared the results.

This paper describes a brief history leading up to the present situation that VCB became a candidate for SF <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</inf> -free switching equipment is reviewed from the perspective of a Japanese VCB manufacturer. Next, some basic considerations in the development of high-voltage vacuum interrupters, structural innovations of VCBs necessary to withstand the high gas pressure of dry air insulation, and high current interruptions are presented. Finally, test methods for VCBs where conventional methods and standards do not work well are presented.

To understand the vacuum arc comprehensively, the information of the neutral and ion temperature is indispensable. In this paper, we present the measured results of excitation temperature for Cu II (Cu+) together with that for Cu I (Cu neutral) in the vacuum arc, using spectroscopic and multiple-image optical measurements in case of CuCr and Cu electrodes. The basic relationships between the excitation temperature of Cu II and other parameters such as current, gap length, and Cr ratio were investigated, and 2-D distribution features of the temperature were discussed. In most part of gap, Cu II takes higher temperature than Cu I. But when plasma is heated sufficiently, Cu II temperature decreases whereas Cu I temperature increases. This phenomenon may be explained as follows. The electron collisional cross section of ions is larger than that of neutrals, the ions are heated to a higher temperature immediately. The collision between such high-energy ions and neutrals may lead energy transfer to the neutrals. A more detailed quantitative study should be carried out as future work.

The application of input-series output-series (ISOS) connected dual active bridge (DAB) converters has advantages in bidirectional power transmission and isolation. However, their application makes it difficult to maintain the voltage balance. In this study, a voltage balancing control method for ISOS-connected DAB converters with no auxiliary circuits is proposed. The proposed control changes methods according to the amount of load. Furthermore, a hierarchized simple controller is proposed to connect a large number of DAB converters for transmission and isolation in high voltage DC (HVDC) systems. The simulation and experimental results indicate that the proposed method can balance the voltage in bidirectional power transmission between two DC grids with unequal voltages.