IEEJ Transactions on Electrical and Electronic Engineering最新文献

To improve the dielectric strength in vacuum, spark conditioning through repetitive breakdowns by AC or impulse voltage is an effective method. AC conditioning at commercial power frequencies has been widely used due to its cost-effectiveness, but the breakdown voltage after AC conditioning is generally lower compared to impulse conditioning. We have confirmed that multiple breakdowns occur successively in a half cycle of AC voltage application. It is considered that the multiple breakdowns are harmful for conditioning and triggered due to the previous breakdown in the same half cycle. In this paper, we discuss dielectric strength improvement by high frequency AC conditioning and how the multiple breakdowns are induced. We experimentally confirmed that the AC conditioning effect is improved by increasing the frequency of AC voltage for different applied AC conditioning voltages in a sphere-plane electrode system. We focused on the breakdown position from the light emission images during AC conditioning to investigate whether the multiple breakdowns were induced or affected by the previous breakdown. We found that the multiple breakdowns occurred close to the previous breakdown position. The multiple breakdowns would be induced by the collision of metal particles due to the previous breakdown with the counter electrode. These breakdowns do not contribute to removing protrusion and would lead to damage to the electrode surface. The increasing frequency of AC conditioning would suppress the multiple breakdowns and improve the dielectric strength in vacuum. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

With the development and application of 5G technology, more efficient and faster mobile communication has become an essential tool in logistics transportation and warehousing processes. Logistics supply chain management (SCM) is a logistics management system centered around the core products or business of the supply chain, as well as a logistics management system organized around the core logistics business. As an important part of logistics SCM, logistics control requires real-time monitoring and adjustment of transportation, warehousing, distribution, and other links. Mobile communication technology can provide real-time positioning, tracking, monitoring, and data transmission functions, which provides strong technical support for logistics control. It can also optimize logistics scheduling and improve logistics efficiency and accuracy, thereby reducing transportation costs and improving logistics quality and efficiency. This article aimed to explore the relationship between mobile communication technology and logistics SCM and control, and to use Principal Component Analysis (PCA) for research. The research results indicated that under the same other conditions, 38 and 37 people rated the X system as liked by companies A and B, accounting for 95% and 92.5% respectively; only 4 and 1 people rated the Y system as liked, accounting for 10% and 2.5% respectively; the likes and dislikes of the X system were much higher than those of the Y system. This indicated a positive relationship between mobile communication technology and logistics SCM and control systems. Logistics SCM and control based on mobile communication technology has become an important direction and development trend in current research on logistics SCM and control. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Composite materials with high heat dissipation and acceptable insulating properties are being developed. Minimizing filler contacts in the composite and is crucial for composite insulating materials. Here, an electrostatic adsorption method was used to prepare thermoplastic polyimide (tpPI) / orientation micro-sized hexagonal boron nitride (h-BN) composite insulating materials. Then the effects of h-BN particle size on the thermal conductivity and DC breakdown strength were investigated. Additionally, the finite element method was used for heat conduction analysis and the results were compared to the measurements. The particle size of the h-BN significantly influences the dc breakdown strength and the thermal conductivity. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In this study, ultra-thin films of Al, Co, and multilayered Al/Co were fabricated using the magnetron sputtering technique on a very thin glass substrate. Subsequently, electromagnetic wave shielding measurements were conducted utilizing the transmission-reflection line method with the aid of a vector network analyzer. In measurements conducted within the X-band microwave frequency range within the waveguide, the maximum electromagnetic interference shielding effectiveness (EMI SE) values obtained were determined as 46 dB for Al, 24 dB for Co, and 48 dB for the multilayered Al/Co film. The structural and morphological analyses of these shielding films were included in the study using x-ray Diffraction (XRD), energy dispersive x-ray analysis (EDAX), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM) techniques. Scattering parameter results indicated that increasing conductivity values enhance the shielding effectiveness (SE) while also demonstrating an additional positive impact on the SE value for multilayered structures. This finding indicates that nanometer-thick Al or Al/Co multilayer films could significantly protect electronic devices or individuals exposed to X-band microwave radiation. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

When an airplane flies in an electric field under a thundercloud, electric fields at the edges and projected portions of the airplane are enhanced and leaders emanate from there. When a positive leader emanating upward from the airplane connects with a downward negative leader from the bottom of an ordinary thundercloud and a negative leader emanating downward from the airplane connects with an upward positive leader from the ground, a large lightning current flows along the channel bridged between the thundercloud and the ground through the airplane. Recently, a method to reduce the risk of lightning strikes to airplanes has been proposed. It controls the charge on the surface of an airplane to suppress the electric field at edges and projected portions of the airplane. In this paper, an airplane under a thundercloud is represented with a vertical conducting bar or a horizontal conducting bar with a small projected portion, which is placed between impulse-high-voltage-applied two flat electrodes, and it is analyzed using the finite-difference time-domain (FDTD) method. Corona and leader discharges emanating from edges and projected portions of an airplane model are considered with their engineering representations: 40-μS/m and 0.02 S/m conducting regions for corona and leader discharges, respectively. The airplane model is not pre-charged or pre-charged negatively. It follows from the FDTD-computed results that pre-charging an airplane model with a relevant amount of negative charge can avoid discharges from and to the airplane model. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In this study, we employed a high-frequency-driven thin-film magnetic sensor to precisely measure the magnetic near field with enhanced spatial resolution, a challenge often faced by conventional loop antennas. Our study introduced an innovative approach utilizing this magnetic sensor to assess the magnetic near field in wireless power transfer systems, comparing its performance against that of a loop antenna. Our findings demonstrate that the magnetic sensor achieves its peak signal-to-noise ratio at a DC bias field of 4.7 Oe and carrier frequency of 0.5 GHz, boasting a detection limit for magnetic fields of ~0.4 A/m. Moreover, the magnetic field trend measured by the magnetic sensor closely aligns with simulation results, exhibiting sharper changes around the center compared to the loop antenna. These results highlight the superior sensitivity and spatial resolution of the magnetic sensor over conventional loop antennas. By enhancing the reliability of electronic systems across diverse applications, these sensors pave the way for advanced EMI/EMC evaluation techniques. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

To provide a hold-up time function in DC-DC supplies for cell site stations or data centers, using a boost converter with a bulk output capacitor as a front-end converter stage is a simple and highly cost-effective solution. However, conventional boost converters with a hard-switching operation result in low conversion efficiency and increased electromagnetic interference emissions. In this paper, a boost converter with a new non-dissipative snubber is proposed that only requires two additional diodes, an inductor, and a multilayer ceramic capacitor. The main feature of the proposed snubber is that the components are not located on the main power processing path. This means they only require low ratings, improving cost-effectiveness. A prototype converter is analyzed, realized, and applied to a 300 W redundant DC-DC power supply module for a 5G cell base station. © 2024 The Author(s). IEEJ Transactions on Electrical and Electronic Engineering published by Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

This paper provides an in-depth study of the winding mechanical properties in generators under rotor interturn short circuit (RISC) cases. Unlike previous studies, this research investigates not only the influence of RISC degrees, but also the RISC positions and the eccentricity on the winding mechanical properties. The electromagnetic force (EF) formulas as well as the electromagnetic-structure coupling model are first proposed to derive the mechanical winding response characteristics, such as the vibration, deformation, the strain, and the stress. Subsequently, both finite element analysis (FEA) and experimental investigations are conducted to validate the theoretical findings. The results reveal that RISC introduces additional harmonics to the EF. Furthermore, as the eccentricity/RISC degree or the distance between the short circuit position and the N-pole increases, the end winding vibrations become more pronounced. When comparing single eccentricity and RISC faults to cases where both faults occur simultaneously, it is observed that the combined faults have a more detrimental impact on the end winding mechanical properties. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

In this work, intrinsic spin Hall conductivity of β-W and its alloy with V has been theoretically studied by the combination of ab initio method with the tight binding method. Both two possible configurations of V in β-W structure are fully considered and their total energy difference used to estimate the thermodynamic average SHC of alloy by using Maxwell-Boltzmann distribution. It is found that due to the small total energy difference between two configurations, there is a significant contribution to the thermodynamic average SHC of the alloy from both configurations, which results in the average SHC of alloy being enhanced up to 12.3% compared with the pristine β-W. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.