• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.234-236
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• 2003

The cryogenic system for inductive superconducting fault current limiter (SFCL) has been investigated recently. In this investigation, the sub-cooled nitrogen cryogenic system was adopted to enhance the performance of DC reactor for 6.6㎸/200A inductive SFCL. In sub-cooled nitrogen state at 64K, the critical current value and the thermal conductivity are larger than those of saturated nitrogen state at 77K and the electrical insulation capacitance should be remarkably enhanced. The solenoid type of 84mH superconducting DC reactor was fabricated and cooled down to 64K by using sub-cooled cooling method with GM-cryocooler and rotary pump. The fabrication techniques of cryogenic system and some experimental results such as cooling down characteristic are introduced in this study. Moreover, the sub-cooled nitrogen cryogenic system was detailedly introduced in this paper.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.588-593
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• 2007

The 600kJ class high temperature superconducting magnetic energy storage (HTS SMES) system is being developed by Korean Electrotechnology Research Institute (KERI). The system is operated in cryogenic temperature and high vacuum condition. The SMS magnet was cooled by conduction cooling method using a Gifford-McMahon cycle cryocooler. Thus, electric insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish compact design 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 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 and Cryogenics
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• v.19 no.1
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• pp.13-16
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• 2017

Water issue, especially water pollution, is a serious issue of 21st century. Being an significant technique for securing water resources, superconducting magnetic separation wastewater system was indispensable. A large bore conduction-cooled magnet was custom-tailored for wastewater treatment. The superconducting magnet has been designed, fabricated and tested. The superconducting magnet was composed of NbTi solenoid coils with an effective horizontal warm bore of 400 mm and a maximum central field of 2.56T. The superconducting magnet system was cooled by a two-stage 1.5W 4K GM cryocooler. The NbTi solenoid coils were wound around an aluminum former that is thermally connected to the second stage cold head of the cryocooler through a conductive copper link. The temperature distribution along the conductive link was measured during the cool-down process as well as at steady state. The magnet was cooled down to 4.8K in approximately 65 hours. The test of the magnetic field and quench analysis has been performed to verify the safe operation for the magnet system. Experimental results show that the superconducting magnet reached the designed magnetic performance.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.587-589
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• 2000

In this paper, the stability criterion for cryocooler-cooled high-temperature superconducting (HTS) coils is discussed. We choose the current, Itr at which "thermal runaway" occurs, as a stability criterion and adopt the relationship between the cooling power of GM cryocooler and the heat generation in coil system to evaluate Itr. We also investigate the transient behavior during a quench process in HTS coils by a newly developed FEM computer program.

• 한국초전도학회:학술대회논문집
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• 2008.08a
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• pp.64-64
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• 2008

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.45-48
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• 2006

The conduction-cooled HTS SMES is operated in cryogenic and high vacuum condition. Thus. Insulation design at cryogenic temperature and high vacuum is a key and an important element that should be established to accomplish compact design is a big advantage of HTS SMES. However, the behaviors of insulators for cryogenic conditions in vacuum are virtually unknown. Therefore, active research and development of insulation concerning application of the conduction cooled HTS SMES was needed. In this study, the insulation characteristics at experimented high vacuum and cryogenic similar to running condition of SMES system. Also, investigated about insulation characteristics of suitable some materials to insulator for conduction-cooled HTS SMES. As these results. the basis data was obtained for insulation materials selection and insulation design for development of 600kJ class conduction-cooled HTS SMES.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.266-268
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• 2003

The neon liquefier by using GM cryocooler is designed and in process of manufacturing for the cooling of 100 hp high temperature superconductor (HTS) motor. It was used the principle of thermosyphon that the rotor of the motor is cooled by the latent heat of liquidized neon. The cold-box was designed to minimize heat loss by conduction, convection, radiation. Two heat exchanger were made to liquefy neon by the direct contact of neon gas on the cold head. As a first stage of our project, evaporation apparatus will be setup in the inner field of the cold-box and then the performance of neon liquefier will be test.

• Progress in Superconductivity and Cryogenics
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• v.8 no.1
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• pp.59-64
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• 2006

A closed-loop cryogenic cooling system for high field magnets is presented. This design is motivated by our recent development of cooling system for 21 tesla Fourier Transform ion Cyclotron Resonance (FT-ICR) superconducting magnets without any replenishment of cryogen. The low temperature superconducting magnets are immersed in a subcooled 1.8 K bath, which is connected hydraulically to the 4.2 K reservoir through a narrow channel. Saturated liquid helium is cooled by Joule-Thomson heat exchanger and flows through the JT valve, isenthalpically dropping its pressure to approximately 1 6 kPa, corresponding saturation temperature of 1.8 K. Helium gas exhausted from pump is now recondensed by two-stage cryocooler located after vapor purify system. The amount of cryogenic Heat loads and required mass flow rate through closed-loop are estimated by a relevant heat transfer analysis, from which dimensions of JT heat exchanger and He II heat exchanger are determined. The detailed design of cryocooler heat exchanger for helium recondensing is performed. The effect of cryogenic loads, especially superfluid heat leak through the gap of weight load relief valve, on the dimensions of cryogenic system is also investigated.

• Progress in Superconductivity
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• v.5 no.2
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• pp.149-152
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• 2004

The design and the fabrication of a 1 MVA single-phase HTS transformer are presented in this paper, The rated voltages are 22.9 ㎸ for primary and 6.6 ㎸ for secondary, and the rated currents are 44 A and 152 A respectively. The transformer has HTS double pancake type windings. This type of winding has many advantages such as ease of fabrication and maintenance, good distribution of surge voltage and insulation of windings. Single HTS wire was used for primary winding and four HTS parallel wires were used for secondary winding. These windings are arranged reciprocally with the shell type iron core. An FRP cryostat with room temperature bore was fabricated to isolate the iron core from the coolant. The winding will be cooled down to 65 K with sub-cooled liquid nitrogen using a GM-cryocooler. The sub-cooled liquid nitrogen has advantages of good insulation because of no bubbles as well as increased current capacity of HTS wire.