• Progress in Superconductivity and Cryogenics
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• v.26 no.1
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• pp.1-4
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• 2024

This study explores the use of a bulk type high-temperature superconductors (HTS) as trapped field magnets in synchronous motors. A HTS bulk is examined for its ability to generate powerful magnetic fields over a permanent magnet and to eliminate the need for a direct power supply connection compared to a tape form of HTS. A 150 kW interior-mounted bulk-type superconducting synchronous motor is designed and analyzed. The A-H formulation is used to numerical analysis. The results show superior electrical performance and weight reduction when comparing the designed model with the conventional permanent magnet synchronous motor of the same topology. This study presents HTS bulk synchronous motor's overall design process and highlights its potential in achieving relatively high power density than conventional permanent magnet synchronous motor.

• Proceedings of the SAREK Conference
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• 2008.11a
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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.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1361-1363
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• 2002

Micro-SMES(Superconducting Magnetic Energy Storage) has been studied as an impulsive high power supply for industrial applications. Recently, electric power reliability of our country has been improved. However, there are still remaining problems which are short-duration variations like instantaneous and momentary interruption and voltage sag by nature calamity ; typhoon, lightning, snow, etc. Besides, power quality ; harmonics, goes down because of using power electronics equipments. Malfunction of controller and stop machinery, and losing important data are caused by poor power quality at a couple of second in accuracy controllers. Due to those, battery based UPS has been used, but there are several disadvantages ; long charge and discharge time, environmental problem by acid and heavy metal, and short life time. Micro-SMES is an alternative to settle problems mentioned above. However, there need huge system apparatuses in order to verify the effect of system efficiency and stability considering the size of micro-SMES, the sort of converter type, and various conditions. This paper presents a cost effective simulation method of micro-SMES and power converter, and design for micro-SMES based system using PSCAD/EMTDC.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2039-2040
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• 2006

Persistent current switch (PCS) system in NMR, MRI, MAGLEV and SMES has many advantages, such as uniformity and durability of magnetic field and reducing a thermal loss, which enable many superconducting application to operate effectively. This paper deals with fabrication and test of heater trigger persistent current switch using coated conductor (CC) which has high n-index, critical current independency from external magnetic field and adaptable selectivity of stabilizer. PCS system consists of magnet power supply for energizing current to a magnet, heater, switch and magnet using coated conductor tape. Finite element method (FEM) is used to simulate thermal quench (switching) characteristic and design heater trigger. With FEM simulation, optimal length of heater is calculated by temperature and time analysis. Fabrication of PCS system and test of heater trigger characteristic were performed and compared with simulation result. This paper would be the foundation of researches of superconducting switching application.

• Progress in Superconductivity and Cryogenics
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• v.7 no.4
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• pp.28-31
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• 2005

To verify the feasibility of bifilar winding type superconducting fault current limiter (SFCL) using BSCCO tape, two types of magnets were fabricated and tested by short-circuit in this research. Even if the FCL using high Tc superconducting (HTS) tape has zero resistance in normal state, it needs to be wound as a bifilar winding for zero inductance. Solenoid type and pancake type bifilar winding magnets are designed and fabricated with the same length of BSCCO tape. The test system consists of AC power supply, transformer, fault switch, load and bifilar winding magnet. The applied AC voltages during fault duration, 0.1s, were from 0.5V to 20V. The test results without bifilar winding magnet were compared with those with each type magnets. The test results include voltage against magnet, transport current and generated resistance curve. Thermal stability, the recovery time, was studied from the results of two type magnets. The pancake type was the most effective to limit fault current but the solenoid type was thermally the most stable. From this research, short-circuit characteristics of the two types were obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.248-248
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• 2007

Demands for electricity are growing, whereas the rate of electricity infrastructure's construction declines gradually. To keep the balance of the demand and supply, the share of underground transmission line will be increased from 8.3% to 10.5% in 2020 but it will be accompanied with enormous public expenses. A great concern in high capacity transmission is on the increase so as to maximize the spacial efficiency. High Temperature Superconducting (HTS) cable is in the lime light which has the merits of environment-friendly, low transmission loss and high transmission with low voltage, but the reliability verification as a power system is yet to be solved. KEPCO completed the installation and acceptance of $3{\phi}$, 22.9kV, 1250A class HTS cable system in 2006 and the long term test is in progress. The test results focusing on long term reliability are presented in this paper.

• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.12-15
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• 2010

Important key technologies of high-$T_c$ superconducting (HTS) transformer may include the HTS wire technology, bushing technology, cooling technology, AC loss, reduction technology, large current technology, and cryogenic temperature insulation technology. From among others, the cryogenic temperature insulation technology may be specifically a core technology for ensuring reliability for the smaller size, stability, economic efficiency, and power supply of a transformer. Therefore, the electric insulation technology of a superconducting transformer should be prerequisite. Such relevant studies are ongoing, but still, they are very insufficient for establishing the cryogenic insulation technology as of yet. Therefore, this paper simulated HTS transformer applied with continuous transposed conductor (CTC), which has been studied as a way of reducing AC loss. Also, the paper analyzed the insulation configuration of HTS transformer and bushing, and, accordingly, reviewed various characteristics of insulation breakdown out of liquid nitrogen. Thus, the paper constituted insulation database, and it is going to design the insulation of a transmission class HTS transformer and bushing.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.101_102
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• 2009

KSTAR(Korea Superconducting Tokamak Advanced Reseach)장치는 차세대핵융합연구장치로써 30개의 초전도자석으로 구성된다. 이 초전도자석에 전원을 공급하게 되는 PF (Poloidal Field) MPS(Magnet Power Supply)는 12상 Pulse 운전을 하게 되는데 이때 $h=kp{\pm}1$의 특성고조파와 90%에 가까운 무효전력이 발생되어 KSTAR 전력계통과 인근 부하장치에 치명적인 영향을 줄 수 있어 고조파와 무효전력을 동시에 보상할 수 있는 최적의 무효전력보상장치의 도입은 필연적이다. 본 논문에서는 KSTAR 1st Plasma 실험시의 무효전력과 고조파를 저감하기 위해 설치했던 즉, 1단계 기계식 스위칭에 의한 RPC(Reactive power compensator)의 보상특성의 평가결과를 기반으로 KSTAR 2009년 Plasma 실험에 대비하여 이의 운전특성과 설치 공간에 따르는 제약 등을 고려하여 최적의 RPC 설계를 도출하기 위해 실시한 TSC(Thyristor Switch Capacitor)기반의 RPC[1] 모의해석 결과와 기술적 사항을 소개하고자 한다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2251-2252
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• 2008

Recently, voltage sag from sudden increasing loads is also one of the major problems inside the utility network. In order to compensate the voltage sag problem, power compensation device systems could be a good solution method. In case of voltage sag, an energy source is needed to overcome the energy loss caused by the voltage sag. Superconducting Magnetic Energy Storage (SMES) is a very promising source of this energy due to its fast response of charging and discharging time. Before constructing the power electronic delivering system for the SMES, it is necessary to simulate the system to understand its behavior. Nowadays, a lot of devices have been developed to compensate voltage sag such as Dynamic Voltage Restorer (DVR), Distribution Static Compensator (D-STATCOM) and Uninterruptible Power Supply (UPS). In this paper, focus is given only on DVR system which will be simulated by using PSCAD/EMTDC software.

• Progress in Superconductivity and Cryogenics
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• v.23 no.4
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• pp.19-24
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• 2021

The low normal zone propagation velocity (NZPV) of high-temperature superconducting (HTS) tape leads to a quench protection problem in HTS magnet applications. To overcome this limitation, various studies were conducted on HTS coils without turn-to-turn insulation (NI coils) that can achieve self-protection. On the other hand, NI coils have some disadvantages such as slow charging and discharging time. Previously, the HTS coils with turn-to-turn insulation (INS coils) were operated in power supply (PS) driven mode, which requires physical contact with the external PS at room-temperature, not in persistent current mode. When a quench occurs in INS coils, the low NZPV delays quench detection and protection, thereby damaging the coils. However, the rotary HTS flux pump supplies the DC voltage to the superconducting circuit with INS coils in a non-contact manner, which causes the INS coils to operate in a persistent current mode, while enabling quench protection. In this paper, a new protection characteristic of HTS coils is investigated with INS coils charging through the rotary HTS flux pump. To experimentally verify the quench protection characteristic of the INS coil, we investigated the current magnitude of the superconducting circuit through a quench, which was intentionally generated by thermal disturbances in the INS coil under charging or steady state. Our results confirmed the protection characteristic of INS coils using a rotary HTS flux pump.