• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.51-54
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• 2013

This paper deals with harmonic components of the voltage on high temperature superconducting wire carrying an alternating current. HTS wire is used to manufacture superconducting power applications carrying an alternating current. Typically, international standard, IEC 61788-3 is used for critical current measurement. Thus, it is not ideal that critical current criteria in dc are adapted to superconducting power devices to decide the operating current of the devices. In this paper, we confirmed odd harmonic voltage on HTS wires carrying an AC. The ratio between harmonic components and fundamental component can be significant clues to decide the critical current criteria for HTS wire and its power applications in AC circumstance.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.53-58
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• 2019

The critical current is one of the key parameters of high temperature superconducting (HTS) racetrack coils. Therefore, it is significant to calculate critical currents of HTS coils. This paper introduces a fast iterative algorithm for calculating the critical current of second generation (2G) HTS coils. This model does not need to solve long charging transients which greatly reduced the amount of calculation. To validate this model, the V-I curve of four 2G HTS double racetrack coils are measured. The effect of the silicon steel sheet on the critical current of the racetrack coil is also studied based on this algorithm.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.32-36
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• 2007

The 600 kJ calss high-temperature superconducting(HTS) SMES(superconducting magnetic energy storage) system is being developed by Korean Electrotechnology Research Institute(KERI). The system is operated in cryogenic temperature and high vacuum condition. The SMES magnet was cooled by conduction cooling method using a Gifford-McMahon cycle cryocooler. Thus the electric insulation design at cryogenic temperature and high vacuum is a key and an important element. Because it accomplish compact design that is a big advantage of HTS SMES. This paper describes the electric insulation design, fabrication and experimental results for a mini model of conduction cooled HTS SMES.

• Progress in Superconductivity
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• v.3 no.1
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• pp.23-27
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• 2001

We have investigated the mixed-state magnetoresistance of high quality c-axis-oriented MgB2 thin film for magnetic field from 0.5 T to 5.0 T, applied normal to ab-plane. The temperature dependence of magnetoresistance was well described by vortex glass and fluctuation theories for different temperature regimes. We observed glassy exponent of v(z-1)~3 and upper critical field of $H_{c2}$(0)~35 T, which is consistent with previous data obtained from direct $H_{c2}$(0) measurements. Interestingly, the thermally activated flux flow region was observed to be very narrow, suggesting that the pinning strength of this compound is very strong. This finding is closely related to the recent reports that the bulk pinning is dominant in $MgB_2$and the critical current density of $MgB_2$ thin film is very high, comparable to that of cuprate superconductor. The present results further suggest that $MgB_2$is beneficial to technical applications.ons.

• Progress in Superconductivity and Cryogenics
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• v.2 no.1
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• pp.36-39
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• 2000

The main issues for the power application of high Tc superconducting tape are lower AC loss and higher stability conditions. HTS tape has large stability margin by high heat capacity of superconductor itself and high temperature margin. But, it can be damaged by continuous heat generation at quench point, because normal zone propagation velocity by generating heat is very low. Here, we analyze the quench propagation characteristics using finite element method for BSCCO-2223 HTS tape.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.26-29
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• 2003

Nowadays, one of the serious problems in KEPCO system is much higher fault current than the SCC(Short Circuit Capacity) of circuit breaker. As the superconductivity technology has developed, the HTS-FCL(High Temperature Superconductor-Fault Current Limiter) can be one of the attractive alternatives to solve the fault current problem. But the parameters of HTS-FCL should be designed optimally to have the best performance. Under this background, this paper presents the optimal design method of parameters for resistive type HTS-FCL using Monte Carlo technique.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.1-5
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• 2015

With the increasing development of renewable energy, it is expected that large-scale renewable power would be transported from the west and north area of China to the east and south area. For this reason, it will be necessary to develop a wide-area power grid in which the renewable energy would be the dominant power source, and the power grid will be faced by some critical challenges such as long-distance large-capacity power transmission, the stability of the wide-area power grid and the land use problem for the power grid. The superconducting technology for power (STP) would be a possible alternative for the development of China's future power grid. In last decade, STP has been extensively developed in China. In this paper, we present an overview of the R&D of STP last decade in China including: 1) the development of high temperature superconducting (HTS) materials, 2) DC power cables, 3) superconducting power substations, 4) fault current limiters and 5) superconducting magnetic energy storage (SMES).

• Progress in Superconductivity and Cryogenics
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• v.25 no.2
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• pp.1-4
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• 2023

Over the past decade, the exploration of high-temperature superconductivity and the discovery of a wide range of exotic superconducting states in Fe-based materials have propelled condensed matter physics research to new frontiers. These materials exhibit intriguing phenomena arising from their multiband electronic structure, strongly orbital-dependent effects, extremely small Fermi energy, electronic nematicity, and topological aspects. Among the various factors influencing their superconducting properties, high magnetic fields play a crucial role as a control knob capable of disrupting the subtle balance between the spin, charge, lattice, and orbital degrees of freedom, leading to the emergence of various exotic superconducting states. In this review, we provide an overview of the current understanding of the exotic superconducting states observed in Fe-based superconductors, with a particular focus on FeSe and Sr₂VO₃FeAs, under the influence of high magnetic fields.

• Progress in Superconductivity
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• v.13 no.2
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• pp.65-84
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• 2011

Study of superconductivity in layered iron-based materials was initiated in 2006 by Hosono's group, and boosted in 2008 by the superconducting transition temperature, $T_c$, of 26 K in $LaFeAsO_{1-X}F_X$. Since then, enormous researches have been done on the materials, with $T_c$ reaching as high as 55 K. Here, we review briefly experimental and theoretical results on atomic and electronic structures and magnetic and superconducting properties of FeAs-based superconductors and related compounds. We seek for clues for unconventional superconductivity in the materials.

• Progress in Superconductivity and Cryogenics
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• v.11 no.2
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• pp.33-36
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• 2009

A 1 MW class HTS (High-Temperature Superconducting) synchronous motor has been developed. This motor is aimed to be utilized for industrial application such as large motors operating in large plants. The HTS field coil of the developed motor is cooled by way of neon thermo siphonmechanism and the stator (armature) coil is cooled by water through hollow copper conductor. This paper also describes evaluation of some electrical parameters from performance test results of our motor, which was conducted at steady state in generator mode and motor mode. Open and short circuit tests were conducted in generator mode while a 1.1 MW rated induction machine was rotating the HTS machine. Electrical parameters such as mutual inductance and synchronous inductance are deduced from these tests. Load test was done upto rating torque during motor mode and efficiency was measured at each load torque.