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Kideok Sim,Seokho Kim,SeokJu Lee,Jeonwook Cho,Tae Kuk Ko IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>A method for estimating the current distribution on the HTS strands which is composed of the HTS power cable was developed. A group of hall sensors which are well-arranged around the HTS cable were used in measuring the circumferential magnetic field. The current distribution can be calculated by solving a matrix equation which contains the measured magnetic field values as its elements. The contribution of the magnetic field generated by each strand in each hall sensor should be known to solve the matrix equation. The contribution can be calculated by FEM analysis simulating the HTS cable or can be measured using a duplicated short HTS cable of which current terminals are modified to apply the current to each strand independently. A simple computer simulation was performed to investigate the feasibility of the method and the performance characteristics of the method was examined for the HTS cable which is composed of several HTS strands. In this paper, a simple mathematics for estimating the current distribution and the results of experiment using the designed and manufactured measuring apparatus will be introduced.</P>
AC Loss Analysis of HTS Power Cable With RABiTS Coated Conductor
Seokho Kim,Kideok Sim,Jeonwook Cho,Hyun-Man Jang,Minwon Park IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>Numerical analysis of AC loss for a HTS power cable is investigated using commercial FEM software package. AC loss of the HTS power cable, which is made by 2 G conductor, is hard to experimentally measure due to very small signal compared to that made by 1G conductor. The FEM model describes current distribution and AC loss inside the HTS conductor for the AC transport current through nonlinear E-J correlation. For the verification of the AC loss analysis model, the results were compared with the well known analytic solution of a single strip HTS conductor and experiments. Unlike IBAD substrate, magnetization of the RABiTS has influence on the precise estimation of the AC loss and it is also considered in the FEM model. Moreover, several conductors should be stacked to meet the large transport current because of the small critical current at present and the effect of stacking configuration is also investigated. In this paper, AC loss analysis results are presented for various HTS power cable configurations such as stacking directions. The results are compared with the experimental results of a model HTS power cable and the best configuration to minimize AC loss is suggested.</P>
Estimation of the critical current of race-track HTS magnet considering angular dependency
Lee, Kyubong,Sim, Kideok,Lee, Changyoung,Kim, Seokho The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.3
The high temperature superconducting (HTS) magnet has been developed for the high magnetic field applications such as NMR, MRI and other industrial machinery. In designing process of these HTS magnets, the accurate estimation on the critical current (Ic) is essential to predict and secure the electromagnetic performance. The critical current of 2G HTS tape has anisotropic Ic degradation characteristics with the application of magnetic field - angular dependency of critical current. It is known that the perpendicular magnetic field to the face of HTS tape makes dominant degradation on the critical current for conventional 2G HTS tape. However, recently developed 2G HTS tape has more complex characteristics due to the artificial pinning center. Therefore, the method for Ic estimation reflecting such characteristics of 2G HTS tape needs to be devised. The method considering the angular dependency is introduced in this paper. And the result of newly devised method is compared with that of previous method.
Sukjin Choi,Sangjin Lee,Kideok Sim,Jeonwook Cho,Soogil Lee,Sang-Geun Lee,Kyu Won Lee,Sang Young Lee,Dong Ho Kim,Tae Kuk Ko IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>In Korea, the superconducting power cable has been developed since 2001, with the basic specifications of 22.9 kV/50 MVA. The superconducting power cable can carry more than 2 to 5 times higher electric power compared with conventional ones. It is important to test the DC critical current related with its power capacity before applying to the real power grid. In 1995, several international standards organizations including IEC, decided to unify the use of statistical terms related with 'accuracy' or 'precision' in their standards. It was decided to use the word 'uncertainty' for all quantitative (associated with a number) statistical expressions. In this paper, we measured DC critical current of 22.9 kV/50 MVA superconducting power cable with several voltage tap and analyzed the uncertainty with these results. These analyzed results can be applied the standardization of the superconducting power cable.</P>
Controllability of the Contact Resistance of 2G HTS Coil With Metal Insulation
Sohn, Myung-Hwan,Sim, Kideok,Eom, Beomyong,Ha, Hong-Soo,Kim, Ho-Yong,Seong, Kichul Institute of Electrical and Electronics Engineers 2018 IEEE transactions on applied superconductivity Vol.28 No.3
<P>The turn-to-turn contact resistance of second-gene-ration (2G) HTS coil with metal insulation is a very important parameter in the viewpoint of the stability and current charging speed of the HTS coil. Controllability of the contact surface resistance of the 2G HTS coil with advanced metal insulation was observed in contrast with the case of the stainless steel (SS) metal insulation (MI). Three types of model coils—a no insulation coil, a metal insulation coil cowound with SS tape, and an MI coil cowound with copper (Cu) electroplated SS tape—were prepared and evaluated. The contact surface resistances between two Cu-plated 2G HTS tapes, between a Cu-plated 2G HTS tape and an SS tape, and between a Cu-plated 2G HTS tape and a Cu-plated SS tape are 6.3, 362.4, and 7.9 <I>μ</I> Ω·cm<SUP>2</SUP>, respectively. Dramatic reduction of the turn-to-turn contact surface resistance in model coils was achieved by using MI coil cowound with the Cu-plated SS tape. Also, the possibility of changing such contact surface resistance will be useful for designing the MI magnet.</P>
Stability of 2G HTS Double Pancake Coil With Metal Insulation and Two Parallel Resistors
Myung-Hwan Sohn,Kideok Sim,Haejong Kim,Beomyong Eom,Kichul Seong,Jeonwook Cho Institute of Electrical and Electronics Engineers 2017 IEEE transactions on applied superconductivity Vol.27 No.4
<P>The enhanced stability of 2G HTS double pancake (DP) coil with metal insulation and parallel resistor was observed in contrast with the case of only metal insulation. Here, we used stainless steel tape and additional indium metal sheet as metal insulator and parallel resistor. The total length of the DP coil was 66 m and the critical current (I<SUB>c</SUB>) of the DP coil was about 78.1 A in liquid nitrogen in the criterion of 0.1 μV/cm. Minimum quench energies (MQEs) were 3.154 J at 60 A of the coil current in liquid nitrogen. MQE was 1.295 J at 60 A of the coil current and 77 K in conduction cool. New DP coil was fabricated by using the indium sheet resistor. MQE was 10.935 J in liquid nitrogen and 1.306 J in conduction cool. In this case, 2G DP MI coil attached with parallel resistors was robust under the condition of the quench induced by the heater.</P>