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Optimum Reduction of Self Field Effects in a Bi-2223 Stacked Super Conducting Bus Bar
Nah,Wansoo,Kang,Hyoungku,Park,Ii-Han,Joo,Jinho,Oh,Sang-Soo,Ryu,Kang-Sik,Yoo,Jaimoo 성균관대학교 1998 학술회의지원논문목록집 Vol.1998 No.-
High Tc Superconductors. such as Bi-2223, have been promising candidates far an eleclrical bus bar because bus bar has relatively low self magnetic field. It has been found that the critical current of Bi-2223 stacked tapes is much less than the total summation of critical currents of each tape, which in mainly attributed to the self magnetic fields. Furthemore, since the critical current degradation of Bi-2223 tape is greater in the normal magnetic field (to the tape surface) than in the parallel one, detailed magnetic field configuration are required to reduce the self field effects. Conceptually by rearranging each stacked tape properly, the self field effects could be minimized In this paper, we calculate the self field effects of stacked conductor defining self field factors of normal and parallel magnetic fields to the tape surface. And we propose an optimum shape of octagonal structured bus bar which has minimum self field effects.
Self Field Effect Analysis of Bi-2223 Tape-Stacked-Cable With Constant Current Density Assumption
Nah, Wansoo,Joo, Jinnho The Korean Institute of Electrical and Electronic 2000 Transactions on Electrical and Electronic Material Vol.1 No.1
In this paper, we analyze self field effects of Bi-2223 tape-stacked cable assuming constant current density in the cross section of stacked cable. Generally, the critical current of Bi-2223 tape-stacked-cable in much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of Bi-2223 tape-stacked-cable, we needs to analyze the self filed effects on the stacked cable as well as critical current density data(J$\_$C/) of one tape. To make it more complex, the critical current degradation of Bi-2223 tape is an-isotropic; the critical current is lower in the normal magnetic field(to the tape surface) than in the parallel field. In the paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J$\_$C/-B curve of one tape is presented with the assumption of constant current density across the stacked cable, The approach basically includes the load analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.
Analytic Approaches to Quench Behaviours of Superconducting Transformer
Nah,Wansoo,Joo,Jinho,Cha, Guee Soo 성균관대학교 1997 학술회의지원논문목록집 Vol.1997 No.-
This paper describes the quenches in superconducting transformer. Magnetizing current effecfs have been considered for the maximum temperature rise estimation during quenches. By introducing the first order model of the infinite solenoid, we calculated the mutual and Ieskage inductances of the coaxial-wound-superconducting transformers. As the permeability of the ttansformer core goes up the leakage inductances of the transformer goes down. These varying permeability effects could be explained through the suggested models. In this paper, the analytical results on the maximum temperature rise estimation, taking account of the magnetizing current, are presented.
나완수 成均館大學校 科學技術硏究所 1996 論文集 Vol.47 No.2
Superconducting transformers are superior to conventional ones in many respects, such as in high efficiency, light weight, and low life-cycle cost. These advatages mainly come from high current density in supercondcuting windings. But, due to high resistivity of matrix around superconductors, this high current density could lead to high density of heat when quench occurrs in superconducting windings. Of course, quench protection scheme should be included in superconducting transformer system, but. the situation is different from DC superconducting magnet system, e.g. MRI magnet system, due to intrinsic AC operation of transformer. In this paper two essential quench protection schemes are studied and the protection principles are established for AC conditions. Finally a protection scheme without auxiliary windings is suggested, using derived equations in this paper.
永久電流 모드를 가지는 超傳導 MRI 마그네트의 勵磁에 대한 硏究
나완수 成均館大學校 科學技術硏究所 1996 論文集 Vol.47 No.1
Superconducting MRI(Magnetic Resonance Image) magnets have various shim coils for the uniform magnetic field, operating in persistent-current-mode. The shim coils, especially between the Z^2 shim and main coils, are magnetically strongly-coupled such as transformer, which disturbs the magnetic uniformities during energization. Since the resistances of the coils are absolutely zero (at DC current) in the superconducting state, the final target currents get contaminated by the magnetically-coupled--shim-coil energization. In this paper, the energization circuits for superconducitng MRI manget are analyzed and the effective way of energizations are proposed. Finally, distributions of magnetic fields after energizations are reported.
NaHyun Kim,Wansoo Nah,SoYoung Kim 대한전자공학회 2014 Journal of semiconductor technology and science Vol.14 No.2
The bulk current injection (BCI) and direct power injection (DPI) method have been established as the standards for the electromagnetic susceptibility (EMS) test. Because the BCI test uses a probe to inject magnetically coupled electromagnetic (EM) noise, there is a significant difference between the power supplied by the radio frequency (RF) generator and that transferred to the integrated circuit (IC). Thus, the immunity estimated by the forward power cannot show the susceptibility of the IC itself. This paper derives the real injected power at the failure point of the IC using the power transfer efficiency of the BCI method. We propose and mathematically derive the power transfer efficiency based on equivalent circuit models representing the BCI test setup. The BCI test is performed on I/O buffers with and without decoupling capacitors, and their immunities are evaluated based on the traditional forward power and the real injected power proposed in this work. The real injected power shows the actual noise power level that the IC can tolerate. Using the real injected power as an indicator for the EMS test, we show that the on-chip decoupling capacitor enhances the EM noise immunity.
Kim, NaHyun,Nah, Wansoo,Kim, SoYoung The Institute of Electronics and Information Engin 2014 Journal of semiconductor technology and science Vol.14 No.2
The bulk current injection (BCI) and direct power injection (DPI) method have been established as the standards for the electromagnetic susceptibility (EMS) test. Because the BCI test uses a probe to inject magnetically coupled electromagnetic (EM) noise, there is a significant difference between the power supplied by the radio frequency (RF) generator and that transferred to the integrated circuit (IC). Thus, the immunity estimated by the forward power cannot show the susceptibility of the IC itself. This paper derives the real injected power at the failure point of the IC using the power transfer efficiency of the BCI method. We propose and mathematically derive the power transfer efficiency based on equivalent circuit models representing the BCI test setup. The BCI test is performed on I/O buffers with and without decoupling capacitors, and their immunities are evaluated based on the traditional forward power and the real injected power proposed in this work. The real injected power shows the actual noise power level that the IC can tolerate. Using the real injected power as an indicator for the EMS test, we show that the on-chip decoupling capacitor enhances the EM noise immunity.