• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.303-305
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• 2002

SSTF(Samsung Superconducting Test Facility) has been constructed at Samsung Advanced Institute of Technology to test the KSTAR(Korea Superconducting Tokamak Advanced Research) superconducting magnets and conductors. The SSTF DAC(Data Acquisition and Control) system basically consists of VME I/O modules, host PCs, and Ethernet links. VxWorks is used for the real-time OS of the VME IOC(Input/output Controller). EPICS (Experimental Physics and Industrial Control System) provides a software architecture for the communication between IOCs and host PCs. For the efficient management of measured data, the database management programs through NFS(Network File System) have been developed and successfully operated. In this paper, the current status of the SSTF DAC system, DBMS(DataBase Management System), recent test results, and future plans are presented.

• Progress in Superconductivity and Cryogenics
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• v.10 no.3
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• pp.43-46
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• 2008

Design of current lead for 21T superconducting magnets is presented. The current lead is composed of a normal metal element, conducting the current from room temperature to intermediate temperature, and an HTS element, conducting the current down to liquid helium temperature. The metal element is disengaged from the HTS element without breaking vacuum after excitation. The optimization of the lead is performed to minimize the thermal heat load when carrying operational current with some margin. In order to confirm the feasibility of our new design, the intermediate joint between a normal metal and HTS element is fabricated and the reliability is tested during engage and disengage performance. The effects of vacuum level and performance cycle on the electrical contact resistance are also investigated.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.6
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• pp.57-62
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• 2011

This paper proposed a method which is the three types of magnet model for improving field inhomogeneity of superconducting magnet. The length of coil wire was compared for the optimized current pattern using minimum power methods and field inhomogeneity under the specific simulation condition in case of same magnet field strength about each magnet type field inhomogeneity. Length of wire and field inhomogeneity were compared under the same condition(18 target points, 20cm DSV). According to the simulation results, the smaller target points can reduce the wire length but it can not improve the field inhomogeneity. Length of wire and low field inhomogeneity can not improve in same time. However, small DSV and reducing target points can overcome the these problem. And to conclude, if it processes shimming as reducing target points in case of magnet model which is open to space, about the size of same imaging region it needs a lot of current values(or the length of wire) and decreases field homogeneity but it is useful to get small ROI.

• Journal of the Korean Vacuum Society
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• v.16 no.5
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• pp.388-396
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• 2007

KSTAR (Korea Superconducting Tokamak Advanced Research) current lead system (CLS) has a role to interconnect magnet power supply (MPS) in room temperature (300 K) and superconducting (SC) bus-line, electrically. For the first plasma experiments, it should be assembled 4 current leads (CL) on toroidal field (TF) current lead box (CLB) and 14 leads on poloidal field (PF) CLB. Two current leads, with the design currents 17.5 kA, and SC bus-lines are connected in parallel to supply 35 kA DC currents on TF magnet. Whereas, it could supply $20\;{\sim}\;26\;kA$ to each pairs of PF magnets during more than 350 s. At the cold terminals of the leads, there are joined SC bus-lines and it was constructed helium coolant control system, aside from main tokamak system, to protect heat flux through current leads and enhanced Joule heat due to supplied currents. Throughout the establishment processes, it was tested the high vacuum pumping, helium leak of the helium lines and hardwares mounted between the helium lines, flow controls for CL, and liquid nitrogen cool-down of possible parts (current leads, CL helium lines, and thermal shield helium lines for CLB), for the accomplishment of the required performances.

• Progress in Superconductivity and Cryogenics
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• v.3 no.2
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• pp.15-20
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• 2001

This paper describes a model flux pump experiment recently performed at the MIT Francis Bitter Magnet Laboratory. The results of the model flux pump will be used in the development of a prototype flux pump that will be couple to a high-temperature superconductor (HTS) insert coil of a high-field NMR (Nuclear Magnetic Resonance) magnet, Such an HTS insert is unlikely to operate in persistent model because of the conductors low index(n) The flux pump can compensate fro field decay in the HTS insert coil and make the insert operate effectively in persistent mode . The flux pump, comprised essentially of a transformer an two switches. all made of superconductor, transfers into the insert coil a fraction of a magnetic energy that is first introduced in the secondary circuit of the transformer by a current supplied to the primary circuit. A model flux pump has been designed. fabricated, and operated to demonstrate that a flux pump can indeed supply a small metered current into a load superconducting magnet. A current increment in the range of microamperes has been measured in the magnet after each pumping action. The superconducting model flux pump is made of Nb$_3$ Sn tape, The pump is placed in a gaseous environment above the liquid helium level to keep its heat dissipation from directly discharged in the liquid: the effluent helium vapor maintains the thermal stability of the flux pump.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.610-619
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• 2000

This paper presents an off-line UPS using the high temperature superconductive magnetic bearing. FES(Flywheel Energy Storage) system has good advantages in compare with lead acid battery. So, high efficiency FES using high temperature SMB(superconductive magnetic bearing) was composed in this paper. The outer rotor type of PMSM(Permanent Magnet Synchronous Motor) as motor/generator was used for the experiment, and square wave current and sinusoidal wave control methods was compared for high efficiency operation of motor/generator. The circuit for in phase sinusoidal wave current control with EMF in the full speed range was designed and the proposed flywheel energy storage system was applied in single phase off-line UPS system. As the stable operation characteristics of prototype system was confirmed, the its excellence as energy storage device in Off-line UPS was proved.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.226-229
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• 2003

Following the successful development of practical high temperature superconducting (HTS) wires, there has been renewed activity in the development of superconducting power equipments. HTS equipments must be operated in the coolant, such as liquid nitrogen (L$N_2$) or cooled by cooler, such as GM-cryocooler to maintain the temperature below critical temperature. In this paper, dielectric strength of some insulating materials, such as epoxy, teflon, and glass fiber reinforced plastic (GFRP) in L$N_2$was measured. Surface breakdown voltage of GFRP which is basic property in design of HTS solenoid coil was measured. Epoxy is a goof insulating material but it is fragile at cryogenic temperature. The multi-layer insulating method of current lead is suggested to compensate this fragile property. It consists of teflon tape layer and epoxy layer fixed with texture. Based on these measurements, the 6.6㎸ class HTS magnet for DC reactor type high-T$_{c}$ superconducting fault current limiter (SFCL) was successfully fabricated and tested.d.

• Electrical & Electronic Materials
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• v.3 no.2
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• pp.90-98
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• 1990

Y-Bi-Ba-Cu-O계 초전도체를 보통의 ceramic방법과 screen printing과 소결법으로 원판형과 후막형으로 제작하였다. B $i_{2}$ $O_{3}$를 첨가하여 소결한 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 초전도 성질은 전기저항측정과 자석위에 부상 유무로 조사하였다. 또한 B $i_{2}$ $O_{3}$를 첨가함에 따라 소결된 시편의 미세구조에 어떠한 영향을 주었는지 알아보았다. 전기저항 측정시 Yttrium 대신에 Bi로 부분적으로 치환한 경우인 $Y_{0.85}$B $i_{0.15}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 상온 저항치가 기본조성인 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$의 그것보다 향상된 미세구조로 인해 더 작은 값을 나타낸다. 반면 $Y_{1}$B $a_{2}$C $u_{3}$ $O_{7-y}$에다가 초과로 B $i_{2}$ $O_{3}$를 첨가한 경우 오히려 미세구조는 불량하고 상온저항치도 더 높다. 이러한 사실은 입계에 잔류하는 이차상은 전기적 성질에는 크게 영향을 주나 자기적 성질에는 거의 영향을 주지않는 것으로 보인다. 후막으로 Y-Bi-Ba-Cu-O를 제작시 기판에 의해 좌우되는데 단지 magnesia 기판에서 소결시 bulk시편과 유사한 성질을 나타냈다.질을 나타냈다.다.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.37-40
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• 1996

Cable-In-Conduit Conductor(CICC) is widely accepted as an advanced superconductor configuration for large scale applications such as tokamak fusion reactors, MAGLEV (MAGnetic LEVitation), and SMES (Superconducting Magnetic Energy Storage). The stability of CICC cooled with supercritical helium can be very high if it is operated below a certain limiting current. This limiting current can be determined by Stekly type heat balance equation. The stability characteristic of CICC for AC operation is more complicated than that of DC because there are additional instability sources which are associated with local flux change. Ramp-rate limitation is a phenomenon discovered during US-DPC (United States-Demonstration Poloidal Coil) program, which showed apparent quench current degradation associated with high dB/dt. This paper describes recent experimental investigation results on the ramp-rate limitation and discusses current imbalance, induced current, current redistribution due to local quench of the strand in the cable.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1992.11a
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• pp.35-38
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• 1992

The feasibility of magnetohydrodynamic (MHD) Ship propulsion using superconduction magnets is reviewed in light of recent advances in high-temperature superconducting. The propulsion using a screw propeller in the noise reduction has it's own limitation. The epochal noiseless MHD propulsion method which does not have this disadvantage is studying nowadays. The subject of a marine MHD as propulsion has been examined before and was found to be interesting because of relatively low magnetic flux densities. It is demonstrated that the MHD propulsion is technically interesting with high magnetic flux density. The development of large-scale magnets using the high-temperature superconductors now under development could make it practical to construct submersibles for high-speed and silent operation.