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Degradation characteristics of 2G HTS tapes with respect to an electrical breakdown
Kang, Jong O,Lee, Onyou,Mo, Young Kyu,Kim, Junil,Bang, Seungmin,Lee, Hongseok,Lee, Jae-Hun,Jang, Cheolyeong,Kang, Hyoungku The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.1
The electrical insulation design for a superconducting coil system is important for developing high voltage superconducting apparatuses. Also, the degraded characteristics of superconducting tapes due to an electrical breakdown should be considered for superconducting coils design. In this study, the degradation characteristics of 2G high temperature superconducting (HTS) tapes were studied with respect to electrical breakdown tests. The degradation tests of 2G HTS tapes were performed with various stabilizer materials. The degradation characteristics of 2G HTS tapes such as critical current(Ic) and index number were observed by performing electrical breakdown tests. It was found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it was concluded that the degradation characteristics of 2G HTS tapes were affected by a stabilizer material and applied breakdown voltage. The cross sectional view of 2G HTS tapes was observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS tapes are concerned with hardness and electrical resistivity of stabilizer layers.
Seungmin Kang,Sungmin Ryu,Simon Song 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3
Vortex-induced vibration (VIV) based energy conversion is a promising methodology to generate electricity by utilizing the flow energy neglected and eventually dissipated in nature, as the power generation process is sustainable and free from emission of pollutants. In this vein, micro-scale energy convertors driven in low-Reynolds-number flows have caught the attention for engineering applications. As the performance of the convertors highly depends on the acting forces or VIV responses, VIV amplifications are necessary to elevate the power output or energy conversion efficiency toward a level of engineering practicability. The attachment of a pair of bumps on an elastically mounted circular cylinder was demonstrated as an effective way to elevate the energy output for VIV-based energy convertors. However, most of relevant studies were conducted for turbulent flows as high-capacity energy convertors are of significant interest for direct engineering applications. On the other hand, the effects of the bumps on the energy transfer have rarely been studied for low Reynolds number flows. This paper then aims to quantify the effects of the circumferential locations of a pair of bumps on the energy transfer ratio in a single circular cylinder VIV configuration for Reynolds number 150. The circumferential location of the bumps is optimized under the synchronization condition, and this is compared with the plain cylinder VIV configuration; the energy transfer ratio is appreciably elevated when the bumps are placed at θ = 60 or 75-degree.
Seungmin Kang,Sungmin Ryu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6
We present a semi-hollow body as an effective strategy to increase the driving force for vortex-induced vibrations (VIVs) of a circular cylinder. The hollow-body concept is evaluated numerically at Reynolds number Re = 200 and in a range of reduced velocity 3 ≤ U red≤ 8 with a mass-spring system released to vibrate in the transverse direction. Our numerical solutions reveal that, compared with solid-cylinder counterparts, the net transverse force is increased significantly through the semi-hollow body. The transverse force acting on the inner surface is found to be developed as a consequence of semi-confined flows driven by the cylinder oscillation. Furthermore, it is shown that the inner force has a phase difference with respect to the force acting on the outer surface. Based on a systematic force analysis, the appreciable increase in the transverse force is attributed to the constructive interference between the inner and outer forces.
Degradation Characteristics of Superconducting Wires With Respect to Electrical Breakdown Tests
Kang, Jong O.,Onyou Lee,Seungmin Bang,Junil Kim,Hongseok Lee,Jonggi Hong,Seokho Nam,Tae Kuk Ko,Yoon Do Chung,Hyoungku Kang Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3
<P>The electrical insulation design for a superconducting system is important when developing a high-voltage superconducting apparatus as a substitute for a conventional one. In this paper, the degradation characteristics of 2G high temperature superconducting (HTS) wires, with respect to electrical breakdown tests, were studied. It was found that the superconducting materials in 2G HTS wires can be damaged in electrical breakdown, and the damaged structure of 2G HTS wires results in the degradation of the Ic and index number. As a result, it was found that the degradation characteristics of the 2G HTS wires were affected by the stabilizer material and applied breakdown voltage. Thus, the hardness and electrical conductivity of a stabilizer material can be considered as design parameters in developing a high-voltage superconducting coil. Finally, the cross-sectional views of 2G HTS wires were presented using a scanning electron microscope.</P>
Kang, Jong O,Lee, Onyou,Mo, Young Kyu,Kim, Junil,Bang, Seungmin,Lee, Hongseok,Lee, Jae-Hun,Jang, Cheolyeong,Kang, Hyoungku The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.3
Recently, the electrical insulation design for electrical apparatuses is important to cope with the tendency of high voltage. The degradation characteristics of a superconducting coil due to an electrical breakdown should be considered to design a high voltage superconducting coil. In this paper, the degradation characteristics of 2G high temperature superconducting (HTS) wires are studied with respect to electrical breakdown tests. To analyze the dependency of the degradation characteristics of 2G HTS wires, the electrical breakdown tests are performed with AC(alternating current) and DC(direct current) voltage. All tests are performed by applying various magnitudes of AC and DC breakdown voltages. To verify the degradation characteristics of 2G HTS wires, the tests are performed with various 2G HTS wires with respect to stabilizer materials. The degradation characteristics of 2G HTS wires, such as Ic(critical current) and index number are measured by performing electrical breakdown tests. It is found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it is concluded that the degradation characteristics of 2G HTS wires are affected by the stabilizer material and applied voltages. The cross-sectional view of 2G HTS wires is observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS wires are concerned with hardness and electrical conductivity of stabilizer layers.