• Progress in Superconductivity and Cryogenics
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• v.17 no.3
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• pp.18-22
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• 2015

This paper deals with high-Tc superconducting (HTS) power charging system with GdBCO magnet, photo-voltaic (PV) controller, and solar panels to charge solar energy. When combining the HTS magnet and the solar energy charging system, additional power source is not required therefore it is possible to obtain high power efficiency. Since there is no resistance in superconducting magnet carrying DC transport current the energy losses caused by joule heating can be reduced. In this paper, the charging characteristics of HTS power charging system was simulated by using PSIM. The charging current of HTS superconducting power charging system is measured and compared with the simulation results. Using the simulation of HTS power charging system, it can be applied to the solar energy applications.

• Progress in Superconductivity and Cryogenics
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• v.14 no.3
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• pp.53-59
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• 2012

Adiabatic demagnetization refrigerator (ADR) for hydrogen re-liquefaction operating between 24 K and 20 K has been designed. $Dy_{0.9}Gd_{0.1}Ni_2$, whose Curie temperature is 24 K, is selected as a magnetic refrigerant. The magnetic refrigerant powder is sintered with oxygen-free high purity copper (OFHC) powder to enhance its effective thermal conductivity as well as to achieve relatively high frequency. A perforated plate heat exchanger (PPHE) operated with forced convection is utilized as a heat switch. The forced convection heat switch is expected to have fast response relative to a conventional gas-gap heat switch. A conduction-cooled high Tc superconducting (HTS) magnet is employed to apply external magnetic field variation on a magnetic refrigerant. $2^{nd}$ generation GdBCO coated conductor HTS tape with Kapton$^{(R)}$ insulation (SUNAM Inc.) will be utilized for the HTS magnet. The magnetization and demagnetization processes are to be achieved by the AC operation of the HTS magnet. The designed magnetic field and target ramp rate of the HTS magnet are over 4 T with 180 A and 0.4 T/s, respectively. AC loss distribution on HTS magnet is theoretically estimated.

• Progress in Superconductivity and Cryogenics
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• v.5 no.1
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• pp.92-96
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• 2003

This paper deals with the characteristics of persistent current switch (rCS) system fer applied HTS magnet system. To apply the high-Tc superconductor in superconducting machine such as motror, generator, MAGLEV, MRI, and NMR, the study on high-Tc superconducting persistent current mode must be performed. In this experiment, the PCS system consists otd superconducting magnet, PCS and magnet power supply. The superconducting magnet was fabricated by connecting four double pancake coils (DPCs) in series. The PCS was inductive double pancake coil type and heated up by the SUS 303L tape heater. The optimal length of PCS was calculated and thermal quench state of PCS was simulated by using finite element method(FEM) and compared with experimental results. The optimal energy to normalize the PCS was calculated and introduced. Finally, the persistent current was observed with respect to various ramping up rate and magnitude of charging current.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.4
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• pp.159-164
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• 2002

This paper presents the design and fabrication of a high-Tc superconducting (HTS) power supply for charging of the HTS magnet load, and its characteristics have been analyzed through experiments. HTS power supply consists of two heaters, an electromagnet, a Bi-2223 solenoid and a Bi-2223 pancake magnet load. In this experiment, 331 mH electromagnet and 0.8 A dc heater current were used, and 8.5 sec and 17 sec were used for pumping period. Mechanism of the superconducting switch is used for heater-trigger. In order to measure the pumping-current with respect to the magnet flux changes, hall sensor was installed at the center of the Bi-2223 pancake load. The experimental observations have been compared with the theoretical predictions. In this experiment, the pumping-current has reached about 1.2 A. In computer simulation, the maximum pumping-current of the system has been predicted to be about 2.7 A.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.30-34
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• 2009

This paper deals with charging and persistent-current mode operating characteristics of BSCCO magnet load using high-temperature superconducting (HTS) power supply. The HTS power supply consists of two heater-triggered switches, an iron-core transformer with the primary copper winding and the secondary BSCCO solenoid, and a BSCCO magnet load. The magnet load was fabricated by double pancake winding and its inductance is about 21 mH. A hall sensor was installed at the middle of the magnet load to measure the current in the load. In order to investigate the efficient pumping characteristics, operating tests of heater-triggered switch with respect to dc heater current were carried out, and the electromagnet current was determined by considering saturation characteristics of its iron core. The saturation characteristics of charged current in the magnet load were observed with respect to various pumping periods: 12 s, 14 s, 24 s and 32 s. After charging the magnet load, the persistent current was measured. The operating characteristics of the persistent current mode were mainly determined by joint resistance and magnet load.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.318-321
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• 2002

Superconductivity has various applications in the whole industry such as the generation of high magnetic field for medical care and diagnosis, the lossless power transmission, environment-friendly vehicles and clean energy storage systems. This paper deals with the High-Tc superconducting(HTS) power supply using heater-triggered switch for the charging of the superconducting magnets. HTS superconducting power supply consists of two heaters, an electromagnet, and Bi-2223 solenoid and Bi-2223 pancake is used as a superconducting load, similar to real HTS magnet. The timing sequential control of two heaters and an electromagnet is an important factor to generate pumping- current in the Bi-2223 load. The thermal analysis of switching parts of the Bi-2223 solenoid according to the heater input was carried out. Based upon the analysis, the 0.8A of heater current were optimally derived. The maximum pumping current reached 1.7A.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.149-150
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• 2005

According to the trend for electric power equipment of high capacity and reduction of its size, the needs for the new high performance electric equipments become more and more important. On of the possible solution is high temperature superconducting (HTS) power application. Following the successful development of practical HTS wires, there have been renewed activities in developing superconducting power equipment. HTS equipments have to be operated in a coolant such as liquid nitrogen ($LN_2$) or cooled by conduction-cooling method such as using Gifford-McMahon (G-M) cryocooler to maintain the temperature below critical level. In this paper, the dielectric strength of unfilled epoxy and filled epoxy in $LN_2$ was analyzed. The filled epoxy composite not only compensates for this fragile property but enhances its dielectric strength.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.20-24
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• 2009

The superconducting property measurement system is used to acquire electrical and thermal properties on short HTS tape samples and the system is composed of specimen holder for mounting HTS tape and a magnet for applying magnetic fields externally. The magnet consists of two split racetrack windings and is designed to produce maximum 3T of center field. The temperature of specimen holder can be varied in range from 10K to 77K. The field homogeneity is required less than 300 gauss stray field contour within 20cm axially and 3cm radially from origin. We have worked on the conceptual designs of the conduction-cooled magnet for the superconducting characteristic measurement system. The measurement system will be fabricated in near future based on the design parameters presented in this paper.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.3-5
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• 2001

Racetrack coils are used in many areas of superconductivity applications such as generators, motors, maglev, wiggler magnets and so on. The fabrication and characteristics of race-track type High Tc Superconducting (HTS) magnets were carried out. The Magnet is composed of 3 pancake coils wound by 37-filamental Bi-2223/ Ag-alloy tapes. Quench current ($I_q$) of both whole magnet and 3 pancake coils were measured. At 77K under the self-field, $I_q$ of magnet was 12A, while in the case of middle pancake coil, $I_q$ was 15A. The upper pancake coils of racetrack magnet with iron plates, magnet having optimized current distribution and initial magnet are compared with each other through 3D FEA, manufacturing and testing these magnets. The measured performance of the upper pancake coil #3 with iron plates improved by 50% on the basis of initial pancake coil #3. Quench current ($I_q$) of field winding was 12A. In addition, the fabrication processes and the characteristics of HTS magnet are described.

• Progress in Superconductivity and Cryogenics
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• v.11 no.1
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• pp.49-54
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• 2009

This paper presents the numerical simulation results on the moving type electrodynamic suspension (EDS) simulator and static type EDS simulator using high-Tc superconducting (HTS) levitation magnet. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible two ways to simulate the EDS system were simulated in this paper by using finite element method (FEM). The first way was the moving type simulator which consists of the fixed HTS magnet and the moving ground conductor. The second way was the static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.