• 한국초전도ㆍ저온공학회논문지
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• 제18권3호
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• pp.10-20
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• 2016

The Cable-In-Conduit-Conductor (CICC) for the ITER tokamak Central Solenoid (CS) has undergone design change since the first prototype conductor sample was tested in 2010. After tests showed that the performance of initial conductor samples degraded rapidly without stabilization, an alternate design with shorter sub-cable twist pitches was tested and discovered to satisfy performance requirements, namely that the minimum current sharing temperature ($T_{cs}$) remained above a given limit under DC bias. With consistent successful performance of ITER CS conductor CICC samples using the alternate design, an attempt is made here to revisit the internal electromagnetic properties of the CICC cable design to identify any correlation with conductor performance. Results of this study suggest that there may be a simple link between the $Nb_3Sn$ CICC internal self-field and its $T_{cs}$ performance. The study also suggests that an optimization process should exist that can further improve the performance of $Nb_3Sn$ based CICC.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.459-466
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• 2008

The KSTAR Magnet Power Supply (MPS) was dedicated to the SC coil commissioning and $1^{st}$ plasma experiment as a part of the system commissioning. Although many efforts to develop large-current power supplies that are useful for high power electronic devices have been made in various application fields, such as for large metal-plating devices, there were clear discrepancies between conventional power supply technologies and that for the SC coils due to the special SC coil load conditions. Therefore, most of the power supply technologies for the SC coils were a challenge in the domestic research area due to their limited application. However, the MPS commissioning result showed that all of the hardware and controlling software operated well, and this result finally led to the success of SC coil commissioning and the KSTAR $1^{st}$ plasma experiment. This paper will describe key features of KSTAR MPS for the $1^{st}$ plasma experiment, and will also report the commissioning results of the magnet power supplies.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.413-418
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• 2008

The toroidal field magnet power supply (TF MPS) for the KSTAR was constructed in August, 2007 and started the operation for the commissioning in March, 2008. The main role of the TF MPS is to supply the electric power to the TF magnet of the KSTAR. The water cooling components of the TF MPS are 16 stacks, busbar of 70 meters. For the cooling of the TF MPS, the D I water cooling system was designed and installed. The water cooling system consists of several pumps, heat exchangers, D I water polishing system and so on. The water cooling system for the TF MPS was tested under the 15 kA current charging condition. In this paper be discussed about the system performance and other parameters.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.522-531
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• 2002

In order to study the thermal-hydraulic behavior of the cable-in-conduit-conductor (CICC), a numerical model has been developed. In the model, the high heat transfer approximation between superconducting strands and supercritical helium is adopted. The strong coupling of heat transfer at the front of normal zone generates a contact discontinuity in temperature and density. In order to obtain the converged numerical solutions, a moving mesh method is used to capture the contact discontinuity in the short front region of the normal zone. The coupled equation is solved using the finite element method with the artificial viscosity term. Details of the numerical implementation are discussed and the validation of the code is performed for comparison of the results with thse of GANDALF and QSAIT.

• Nuclear Engineering and Technology
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• 제40권6호
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• pp.467-476
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• 2008

To keep the superconducting (SC) magnet coils of KSTAR at proper operating conditions, not only the coils but also other cold components, such as thermal shields (TS), magnet structures, SC bus-lines (BL), and current leads (CL) must be maintained at their respective cryogenic temperatures. A helium refrigeration system (RRS) with an exergetic equivalent cooling power of 9 kW at 4.5 K without liquid nitrogen ($LN_2$) pre-cooling has been manufactured and installed. The main components of the KST AR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The process helium is compressed from 1 bar to 22 bar passing through the WCS and is supplied to cryogenic devices. The main components of cryogenic devices are consist of cold box (C/B) and distribution box (D/B). The C/B cool-down and make the various cryogenic helium for the KSTAR Tokamak and the various cryogenic helium is distributed by the D/B as per the KSTAR requirement. In this proceeding, we will present the commissioning results of the KSTAR HRS. Circuits which can simulate the thermal loads and pressure drops corresponding to the cooling channels of each cold component of KSTAR have been integrated into the helium distribution system of the HRS. Using those circuits, the performance and the capability of the HRS, to fulfill the mission of establishing the appropriate operating condition for the KSTAR SC magnet coils, have been successfully demonstrated.

• 한국진공학회지
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• 제17권1호
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• pp.58-66
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• 2008

KSTAR 전류전송제어시스템은 네트워크기반의 실시간 분산제어시스템으로 EPICS (Experimental Physics and Industrial Control System)를 미들웨어로 채용하여 구축하였다. 전류전송제어시스템은 초전도자석시스템에 전류를 전송하기 위한 시스템으로서 전류전송과 동시에 초전도자석이 초전도상태를 유지하기 위한 냉매의 전송도 담당하고 있다. 주제어실에서의 원격운전을 위하여 EPICS IOC(Input Output Controller) 서버를 현장에 설치하였고 이를 통하여 전류전송제어시스템은 고유의 이름(PV)에 적절한 조작 및 감시 명령을 부여하여 주제어실의 운전화면을 통하여 시스템의 감시 및 조작이 가능하도록 하였다. EPICS와 PLC의 통신을 위하여 ether-ip 드라이버를 이용하여 EPICS IOC를 구축하였으며, 시험 결과 안정성 및 운용성 측면에서 만족할 만한 결과를 획득하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제24권1호
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• pp.1-7
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• 2022

So far, large-scale scientific devices such as nuclear fusion tokamaks and high energy circular accelerators were constructed using high-current conductors made of metallic superconducting wires. Recently, as REBCO superconducting wires usable in high magnetic fields have been developed by several companies, researchesto apply high current cable type REBCO conductors to next-generation large superconducting magnets were also started. High critical currents of several kA or more in high magnetic fields have been successfully demonstrated on test samples of REBCO cable conductors by several research groups. In this review article, the main features and properties of the representative high current REBCO conductors such as CORC(Conductor On Round Core), TSTC(Twisted Stacked-Tape Cable) and RACC(Roebel-Assembled Coated Conductor), which are currently being developed at abroad are briefly introduced. Research activities of high-current density REBCO MHOS(Multi HTS layers on One Substrate) conductor at KERI, whose structure is different from other cable type REBCO conductors are also shortly introduced.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 추계학술대회
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• pp.130-131
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• 2019

국제 핵융합실험로(ITER)를 위해 한국이 제작, 시험, 설치 및 시운전을 하기로 되어 있는 CS(Central Solenoid) 초전도 자석용 전원장치의 시험 및 그 결과에 관하여 논의하고자 한다. 토카막 운전에서 플라즈마 발생 및 제어를 위한 대전류, 고전압, 270 kA 단락 용량 및 4상한 운전 특성을 갖는 45 kA/1050 V의 12펄스 싸이리스터 AC/DC 컨버터 및 제어기를 제작완료하였으며, ITER 부지로 운송하기 전에 공장의 전원 및 부하용량을 고려하여 시험절차서를 개발하였으며, 공장시험(FAT, Factory Acceptance Test)를 진행하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제5권1호
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• pp.71-75
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• 2003

The conduit fer superconducting cable is welded and plastically deformed during the jacketing process to make the CICC (Cable-in-Conduit-Conductors) fer a fusion magnet. The jacketing process of KSTAR (Korea Superconducting Tokamak Advanced Research) conductors is composed of several sequential steps such as rounding, welding, sizing, and square-rolling. Since the welded zone in Incoloy 908 conduit is brittle and easy to have flaws, there may be a possibility of stress corrosion cracking during the heat treatment of coil when both the induced tensile residual stress and the concentration of oxygen in the furnace are sufficiently high. The steps of the jacketing process were simulated using the finite element method of the commercial ABAQUS code, and the stress distribution in the conduit in each step was calculated, respectively. Furthermore, the variations of residual welding stresses through the steps of the jacketing process were calculated and analyzed to anticipate the possibility of the stress corrosion cracking in the conduit. The concentrated high tensile residual welding stresses along the welding bead decrease by the plastic deformation of the following sizing step. The distribution in residual stresses in the conductor for magnet coil is mainly governed by the last step of square-rolling.

• Journal of Electrical Engineering and Technology
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• 제7권2호
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• pp.178-183
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• 2012

The design of the integrated quench protection (QP) system for the high current superconducting magnet (SCM) has been fabricated and tested for the toroidal field (TF) coil system of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. The QP system is capable of protecting the TF SCM, which consists of 16 identical coils serially connected with a stored energy of 495 MJ at the design operation level at 35.2 kA per turn. Given that the power supply for the TF coils can only ramp up and maintain the coil current, the design of the QP system includes two features. The first is a basic fast discharge function to protect the TF SCM by a dump resistor circuit with a 7 s time constant in case of coil quench event. The second is a slow discharge function with a time constant of 360 s for a daily TF discharge or for a stop demand from the tokamak control system. The QP system has been successfully tested up to 40 kA with a short circuit and up to 34 kA with TF SCM in the second campaign of KSTAR. This paper describes the characteristics of the TF QP systems and test results of the plasma experiment of KSTAR in 2009.