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H Okubo - One of the best experts on this subject based on the ideXlab platform.
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hvdc Electrical Insulation performance in oil pressboard composite Insulation system based on kerr electro optic field measurement and electric field analysis
IEEE Transactions on Dielectrics and Electrical Insulation, 2018Co-Authors: H OkuboAbstract:For the development of HVDC Electrical Insulation performance in liquid dielectric systems such as oil-pressboard (PB) composite systems in DC converter transformers, a Kerr electro-optic electric field measurement (Kerr-EOM) technique has been well established and will be considered as the key technique to be introduced. In this paper, the Kerr-EOM was experimentally applied to identify the electric field stress distribution and clarify charging activities in oil/PB composite Insulation systems, under HVDC and DC polarity reversal (DC-PR) conditions. The physical mechanisms of charge movement and the amount of charge accumulation in liquid/solid Insulation systems are also thoroughly investigated and discussed. Moreover, the breakdown discharge initiation by accumulated charges on the PB was observed and discussed together with the field measurement results. Secondly, by combining the Kerr-EOM with the electric field analysis using the Finite Element Method (FEM), the enhancement of the Electrical Insulation performance for HVDC applications was discussed and the critical testing voltage conditions in DC converter transformers were addressed. This paper is based on the Hans Tropper Memorial Lecture given at the IEEE DEIS, International Conference on Dielectric Liquids (ICDL) in 2017 in Manchester, UK.
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electric field distribution with dynamic charge activity in composite Insulation systems under hvdc and dc polarity reversal conditions
Conference on Electrical Insulation and Dielectric Phenomena, 2017Co-Authors: H Okubo, R Nakane, K Takabayashi, K KatoAbstract:As for the development of AC/DC converter power transformers, it is necessary to enhance their Electrical Insulation performance while taking specific DC behaviors, such as DC electric field distribution, dynamic charge accumulation and DC polarity reversal characteristics, into consideration. In this paper, the electric field distributions in an oil-impregnated pressboard composite structure were calculated under AC, DC steady-state and DC polarity reversal conditions, by an analysis with the Finite Element Method (FEM), and their Electrical Insulation performances were quantitatively investigated and discussed. The results clarified that it was very important to well arrange the pressboard barriers in oil to reduce the emerging electric stresses, based on the beforehand accumulated charge amount under DC steady-state conditions, especially at the instant of DC polarity reversal, which will be the most critical conditions.
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kerr electro optic electric field measurement and Electrical Insulation performance in hvdc liquid dielectric systems
International Conference on Dielectric Liquids, 2017Co-Authors: H OkuboAbstract:A Kerr electro-optic electric field measurement technique was introduced for the direct measurement of electric field distributions and charging activities for a pressboard (PB) arrangement in oil/PB composite Insulation systems, under HVDC and DC polarity reversal conditions. Next, under different PB arrangements in oil, the time dependent behavior of electric field stress was measured under both DC voltage and DC polarity reversal (DC-PR) conditions. The physical mechanisms of the movement and accumulation of charge carriers in the Insulation systems were also clarified. Moreover, the breakdown discharge initiation by accumulated charges on PB was investigated and analyzed. FEM based electric field analysis techniques were also applied for liquid dielectric Insulation systems, especially for the DC converter transformer structure. Finally, the Electrical Insulation performance for HVDC applications was discussed.
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enhancement of Electrical Insulation performance in power equipment based on dielectric material properties
IEEE Transactions on Dielectrics and Electrical Insulation, 2012Co-Authors: H OkuboAbstract:Research and development results of enhancement techniques of Electrical Insulation performance for higher electric field application in power transmission/substation equipment, such as transformers, switchgears and cables, are described, especially based on the view point of dielectric materials. Firstly, the electric field analysis, field optimization and field measurement techniques are introduced to discuss higher electric field stress applications in power equipment. Secondly, material types, including gases, liquids, solids, vacuum and their composite systems are discussed to make power equipment with higher Insulation performance, lower losses, lower environmental impact and higher reliability. In the process of development, a highly sophisticated new approach to clarify the physical mechanisms of partial discharges was developed and applied. By the introduction and applications of the above mentioned new Electrical Insulation techniques based on dielectric materials, concepts of future power equipment with higher electric field stress are proposed. This paper is based on the Whitehead Memorial Lecture given at the IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) 2011 in Cancun, Mexico.
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recent trend and future perspectives in Electrical Insulation techniques in relation to sulfur hexafluoride sf 6 substitutes for high voltage electric power equipment
IEEE Electrical Insulation Magazine, 2011Co-Authors: H Okubo, A BeroualAbstract:The recent technical trend of sulfur hexafluoride (SF6) substitutes and future perspectives in the development of Electrical Insulation techniques for electric power equipment are reviewed and discussed.
Chingping Wong - One of the best experts on this subject based on the ideXlab platform.
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flexible thermal interfacial materials with covalent bond connections for improving high thermal conductivity
Chemical Engineering Journal, 2020Co-Authors: Shuaishuai Cheng, Zhiyi Zhang, Yaqing Liu, Xiaoyuan Duan, Yanjuan Ren, Zhijian Sun, Chingping WongAbstract:Abstract Owing to the rapid development of modern electronic devices, high through-plane thermal conductive thermal interface materials (TIMs) with satisfied Electrical Insulation property have become increasingly important in affecting the lifetime and reliability of electronics. Meanwhile, how to maximize the performance comprehensively over all aspects undoubtedly inspired the research interests. Here, BN/CNTs/NR composites were synthesized by the vacuum-assisted method and the highest thermal conductivity could reach 1.34 W m−1 K−1. The covalently bonded connections of BN/CNTs hybrids had a significant contribution for the thermal conductivity by reducing the filler/filler interfacial thermal resistance and phonon scatterings. In addition, the sensitive response ability of thermal and satisfactory Electrical Insulation further demonstrated its strong potential practicality in TIMs. More importantly, this approach opened up a novel way to design TIMs and showed promising applications in the modern electronic devices.
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a polymer based thermal management material with enhanced thermal conductivity by introducing three dimensional networks and covalent bond connections
Carbon, 2019Co-Authors: Shuaishuai Cheng, Zhiyi Zhang, Can Jiang, Haoming Fang, Yaqing Liu, Chingping WongAbstract:Abstract With the growing challenges of modern electronics in heat dissipation, developing thermal management materials with high thermal conductivity and Electrical Insulation property remains an important issue for electronics. In this work, a novel three-dimensional network (3D) of boron nitride/reduced graphene oxide (BN/rGO) with covalent bond connections were fabricated by using the surface modification and ice-templated methods. The as-prepared boron nitride/reduced graphene oxide/nature rubber composites (BN/rGO/NR) possessed an enhanced through-plane thermal conductivity of 1.28 W m−1 K−1 and satisfactory Electrical Insulation at a low filler loading of 4.9 vol%. The results demonstrated that the covalent bond connections and three-dimensional networks of fillers greatly reduced the interfacial thermal resistance as well as phonon scatterings at the filler/filler and filler/matrix interface simultaneously. More importantly, this strategy provided a creative insight to the design of advanced thermal management materials and also presented a bright application prospect for next-generation electronic packing.
You Zeng - One of the best experts on this subject based on the ideXlab platform.
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silica coating onto graphene for improving thermal conductivity and Electrical Insulation of graphene polydimethylsiloxane nanocomposites
Journal of Materials Science & Technology, 2019Co-Authors: Chaoxuan Shen, Han Wang, Tengxin Zhang, You ZengAbstract:Abstract Graphene possess extremely high thermal conductivity, and they have been regarded as prominent candidates to be used in thermal management of electronic devices. However, addition of graphene inevitably causes dramatic decrease in Electrical Insulation, which is generally unacceptable for thermal interface materials (TIMs) in real electronic industry. Developing graphene-based nanocomposites with high thermal conductivity and satisfactory Electrical Insulation is still a challenging issue. In this study, we developed a novel hybrid nanocomposite by incorporating silica-coated graphene nanoplatelets (Silica@GNPs) with polydimethylsiloxane (PDMS) matrix. The obtained Silica@GNP/PDMS composites showed satisfactory Electrical Insulation (Electrical resistivity of over 1013 Ω cm) and high thermal conductivity of 0.497 W m−1 K−1, increasing by 155% compared with that of neat PDMS, even higher than that of GNP/PDMS composites. Such high thermal conductivity and satisfactory Electrical Insulation is mainly attributed to the insulating silica-coating, good compatibility between components, strong interfacial bonding, uniform dispersion, and high-efficiency heat transport pathways. There is great potential for the Silica@GNP/PDMS composites to be used as high-performance TIMs in electronic industry.
Ping Zhang - One of the best experts on this subject based on the ideXlab platform.
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segregated double network enabled effective electromagnetic shielding composites with extraordinary Electrical Insulation and thermal conductivity
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: Ping Zhang, Xin Ding, Yanyan Wang, Yi GongAbstract:Abstract Miniaturization and high frequency are two key features of the next generation electronic devices, thus advanced electronic packaging materials with high thermal conductivity and excellent electromagnetic shielding performance (EMI SE) are highly expected. This work presents poly (vinylidene fluoride)@multi-wall carbon nanotube/boron nitride (PVDF@MWCNT/BN) composites with effective EMI SE and satisfactory Insulation and thermal conductivity through a tailor-made segregated double network. PVDF@MWCNT composite microspheres were fabricated as the thermal and Electrical conductive micro-network, then another BN macro-network was further prepared to provide Electrical Insulation and further thermal conductivity enhancement. This so-called double segregated network of PVDF@MWCNT/BN composites shows a thermal conductivity of 0.83 W m−1 K−1, electron Insulation of 8.33 × 10−14 S cm−1 and electromagnetic shielding of 8.68 dB at 8.2 GHz when loaded 5 wt% MWCNT and 40 wt% BN. The study sheds new lights on the development of special functional materials and the PVDF@MWCNT/BN composites are highly promising as a future electronic packaging material.
Yi Gong - One of the best experts on this subject based on the ideXlab platform.
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segregated double network enabled effective electromagnetic shielding composites with extraordinary Electrical Insulation and thermal conductivity
Composites Part A-applied Science and Manufacturing, 2019Co-Authors: Ping Zhang, Xin Ding, Yanyan Wang, Yi GongAbstract:Abstract Miniaturization and high frequency are two key features of the next generation electronic devices, thus advanced electronic packaging materials with high thermal conductivity and excellent electromagnetic shielding performance (EMI SE) are highly expected. This work presents poly (vinylidene fluoride)@multi-wall carbon nanotube/boron nitride (PVDF@MWCNT/BN) composites with effective EMI SE and satisfactory Insulation and thermal conductivity through a tailor-made segregated double network. PVDF@MWCNT composite microspheres were fabricated as the thermal and Electrical conductive micro-network, then another BN macro-network was further prepared to provide Electrical Insulation and further thermal conductivity enhancement. This so-called double segregated network of PVDF@MWCNT/BN composites shows a thermal conductivity of 0.83 W m−1 K−1, electron Insulation of 8.33 × 10−14 S cm−1 and electromagnetic shielding of 8.68 dB at 8.2 GHz when loaded 5 wt% MWCNT and 40 wt% BN. The study sheds new lights on the development of special functional materials and the PVDF@MWCNT/BN composites are highly promising as a future electronic packaging material.