• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.14-16
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• 2015

Due to the considerable development of the technology of second generation high-temperature superconductors and a significant improvement in their mechanical and transport properties in the last few years it is possible to use HTS tapes in the magnetic levitation systems. The advantages of tapes on a metal substrate as compared with bulk YBCO material primarily in the strength, and the possibility of optimizing the convenience of manufacturing elements of levitation systems. In the present report presents the results of the magnetic levitation force measurements between the stack of HTS tapes containing $n=2{\div}200$ of tapes $12mm{\times}12mm$ and NdFeB permanent magnet in the FC and ZFC regimes. It was found a non- linear dependence of the levitation force from the height of the array of stack in both modes: linear growth at small thickness gives way to flattening and constant at large number of tapes in the stack. Established that the levitation force of stacks comparable to that of bulk samples. The numerical calculations using finite element method showed that without the screening of the applied field the levitation force of the bulk superconductor and the layered superconductor stack with a critical current of tapes increased by the filling factor is exactly the same, and taking into account the screening force slightly different.

• 한국초전도학회:학술대회논문집
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• v.16
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• pp.88-88
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• 2006

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.9
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• pp.442-447
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• 2003

Motors with HTS wires or bulks have been developing recently. Those are large synchronous motor with HTS wires at the field winding in the rotor, hysteresis and reluctance motors with HTS bulk in the rotor. This paper presents the fabrication and test results of an HTS induction motor. Conventional end rings and short bars were replaced with HTS wires in the motor. Stator of the conventional induction motor was used as the stator of the HTS motor. Rated capacity and rpm at full rotor of the conventional motor were 0.75[kW] and 1,710[rpm]. Two, HTS wires are used in parallel to make the end rings and bars. The critical current of the BSCCO-2223 HTS wire which was used in the bars and end rings were 115[A]. Electrodynamometer was coupled directly to the shaft of the rotor with HTS wires.

• Progress in Superconductivity
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• v.13 no.1
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• pp.58-63
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• 2011

Recently, superconductor flywheel energy storage systems (SFESs) have been developed for application to a regenerative power of train, a power quality improvement, the storage of distributed power sources such as solar and wind power, and a load leveling. As the high temperature superconductor (HTS) bearings offer dynamic stability without the use of active control, accurate analysis of the HTS bearing is very important for application to SFESs. Mechanical property of a HTS bearing is the main index for evaluating the capacity of an HTS bearing and is determined by the interaction between the HTS bulks and the permanent magnet (PM) rotor. HTS bearing rotor consists of PM and iron collector and the proper dimension design of them is very important to determine a supporting characteristics. In this study, we have optimized a rotor magnet array, which depends on the limited bulk size and performed various dimension layouts for thickness of the pole pitch and iron collector. HTS bearing rotor was installed into a single axis universal test machine for a stiffness test. A hydraulic pump was used to control the amplitude and frequency of the rotor vibration. As a result, the stiffness result showed a large difference more than 30 % according to the thickness of permanent magnet and iron collector. This is closely related to the bulk stiffness controlled by flux pining area, which is limited by the total bulk dimension. Finally, the optimized HTS bearing rotor was installed into a flywheel system for a dynamic stability test. We discussed the dynamic properties of the superconductor bearing rotor and these results can be used for the optimal design of HTS bearings of the 10kWh SFESs.

• Progress in Superconductivity and Cryogenics
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• v.20 no.1
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• pp.11-14
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• 2018

High Temperature Superconducting (HTS) power cables are capable of transmitting bulk power without any loss compared to conventional copper cables. The major challenge in the design of such HTS cables is the high stresses (electro-thermal/electro-mechanical) developed at high voltages, high currents and cryogenic temperatures. The safe and reliable operation of HTS cables involves lots of instrumentation for monitoring, measurement, control and safe operation. In principle, a four probe method for resistance (RTD PT-100) is used for temperature measurements at various locations of HTS cable. The number of connecting leads required for this is four times that of the number of sensors. The present paper discusses a novel way of connecting 128 RTD sensors with the help of only 14 leads using a cold electronics based multiplexer board. LabVIEW 11.0 software was used for interfacing and displaying the readings of all the sensors on computer screen.

• Progress in Superconductivity and Cryogenics
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• v.10 no.2
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• pp.1-11
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• 2008

The application of bulk superconducting materials to electrical power systems is very attractive because bulk high temperature superconductors offer excellent electromagnetic properties. In recent years there has been significant progresses in the research and fabrication of superconducting bulk materials. Numerous efforts have been made worldwide to make bulk YBCO as a replacement of the conventional magnets to produce larger magnetic field and hence to improve the device performance in electrical power applications. This paper gives a comprehensive review of different applications of bulk HTS materials, concentrating in three areas including superconducting bearing, superconducting motors and high field magnets. The advantages of applying superconducting material into each application are analysed. The status of current research in each section is summarized and examples are given to demonstrate how YBCO bulk materials can benefit the design of electrical devices. Several numerical models which calculate the electromagnetic properties of bulk superconductors are introduced and finally the article concludes with a review on the studies of the demagnetisation effect in superconducting bulk magnets which is extremely relevant to applying superconducting technology to rotating machines.

• Progress in Superconductivity
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• v.12 no.1
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• pp.27-31
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• 2010

A superconductor flywheel energy storage system (SFES) is an electro-mechanical battery which transforms electrical energy into mechanical energy for storage, and vice versa. Many aspects of the quasi-static behavior of flywheel rotors still need to be studied closely, and the rotors require a stable and highly efficient supporting system such as high temperature superconductor (HTS) bearings, which offer dynamic stability without the use of active control. Quasi-static properties of HTS bearings in the radial direction provide data to solve problems which may occur in a running system. Since stiffness in countering rotor vibration is the main parameter for designing an HTS bearing system, we investigated the quasi-static properties of the magnetic force between permanent magnets(PMs) and HTS bulks in the radial direction. We measured radial stiffness, and discovered that bearing stiffness varied greatly depending on the number of active HTS bulks. This is valuable data for predicting the change in stiffness during partial HTS bearing failure. The quasi-static test results are used for optimal design and performance prediction for the 100 kWh class superconductor bearing.

• Progress in Superconductivity and Cryogenics
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• v.12 no.1
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• pp.32-36
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• 2010

Superconducting current leads are indispensible for reducing power loss when subjecting current into superconducting magnets. HTS(High-Tc superconducting) current leads are divided into two types; one is bulk type and the other is tape type. In this paper, conceptual design on the HTS current leads which adopts tape type for nuclear fusion magnets is carried out using magnetic field analysis and thermal analysis. When large current flows through superconducting current leads, strong self magnetic field is generated and applied to the superconducting tapes. This phenomenon leads to the critical current decrease of the superconducting tape. Therefore, we analyzed magnetic field distribution of current leads and found the proper arrangement with respect to the various HTS tapes. In addition to the magnetic field analysis, heat leak through the current leads was also calculated to know which HTS tape is superior than others in thermal aspect. Magnetical field analysis and calculation of heat leak are performed to design 2 kA class HTS current leads.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04a
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• pp.88-95
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• 2002

Recent development in the field of RE-Ba-Cu-O (REBCO, RE: Y or rare earth elements) bulk high-Tc superconductors (HTS) is reviewed in the present paper. After the fatal weak link problem of sintered REBCO superconductors has been overcome by melt processing, this field has been greatly advanced during last ten years. The critical current density $J_c$ at 77 K has been enhanced by introducing effective flux pinning sites into the $REBa_2Cu_3O_y$ (RE123) superconducting matrix. Large melt-textured REBCO bulk crystals have been fabricated with the TSMG(top-seeded melt growth) technique. Mechanical properties of REBCO bulks have been improved by using the Ag additive or epoxy resin. Real bulk applications such as current lead, fault current limiter, flywheel energy storage system, magnetic field source, magnetic separation system, and etc., surely come true near future.

• Progress in Superconductivity and Cryogenics
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• v.23 no.3
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• pp.37-40
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• 2021

Nickel (Ni) is a kind of the rare earth resources. Since Ni-containing waste is drained after several plating operations in the factories, the effective recycling technique has been expected to be introduced. An actual magnetic separation technique using HTS bulk magnet generating the strong magnetic field has succeeded in collecting the paramagnetic slurry containing Ni-sulphate coarse crystals which were fabricated from the Ni-plating waste. The Ni compound in the collected slurry was identified as NiSO₄/6H₂O, showing slight differences in the particle size and magnetic susceptibility between the samples attracted and not-attract to the magnetic pole. This preferential extraction suggests us a novel recycling method of Ni resource because the compound is capable of recycling back to the plating processes as a raw material.