• Progress in Superconductivity and Cryogenics
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• v.11 no.4
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• pp.33-36
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• 2009

An air gap between the pancake windings was provided in this paper to increase the central magnetic field of a high temperature superconducting (HTS) magnet consisting of pancake windings. Unlike the LTS magnet, providing an air gap between the pancake windings increases the central magnetic field of a HTS magnet. Furthermore, the uniformity of the magnetic field near the center of the magnet increased because the pancake windings spread out in wider area. Effects of the air gap on the central magnetic field of an HTS magnet was described in this paper, Calculation of the critical current was carried out by using E-J relation of the HTS wire and the optimization technique was adopted to obtain the appropriate critical current which could maximize the central magnetic field. Pancake windings with BSCCO-2223 HTS wire were wound on glass epoxy bobbin. 6 double pancake windings with 200 turns were used to construct a HTS magnet. Characteristics of the HTS magnet including the central magnetic field and the uniformity of the magnetic field were measured and compared with the results of calculation.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.107-109
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• 2007

Pancake windings have merits that are easier to make high field magnets and replace windings when an accident happens and windings are aged. The current of the whole magnet consisted of windings connected in series was limited by the minimum current of the top and bottom pancake windings where maximum perpendicular magnetic field was applied. This paper propose a optimal design of a HTS magnet excited by a single source, where evolution strategy was adopted for optimal design algorithm. A magnet consisted of 8 BSCCO pancakes was chosen to prove the effectiveness of this optimal design method. Magnetic field at the center of a magnet was chosen as the object function and it was used maximized. Results of the optimal design shows that the increment of the number of turns of the pancake winding make the magnetic field of the center of the magnet increase but the current of the winding decrease for the larger perpendicular magnetic field.

• Progress in Superconductivity and Cryogenics
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• v.12 no.4
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• pp.31-35
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• 2010

In superconducting magnet applications, winding methods of the superconducting magnet can be classified into a layer winding and a pancake winding. The superconducting magnet using high temperature superconductor (HTS) with rectangular shape is generally fabricated using the pancake winding method. On the other hand, low temperature superconducting (LTS) magnet may be wound by either a pancake winding or a layer winding. Compared with the layer winding, the pancake winding method has a merit of easy replacement of a damaged pancake module, but it also has a demerit of requirement of splicing between each double pancake modules. In this paper, we investigated characteristics of the layer and pancake winding methods using HTS. Six samples were wound out of BSCCO and Coated Conductors (CCs) by two winding methods and their characteristics were experimentally observed.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.215-218
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• 2002

HTS motors and generators have some advantages over LTS machines because of higher operating temperature. Very low temperature nakes LTS machines need higher refrigeration cost and large facilities. However, HTS machines are expected to be comparable with conventional counterparts at smaller machine ratings than LTS generators in terms of efficiency and size. As the operating temperature increases, the magnetic flux density generated by HTS field coils decreases relatively. For example, 1000hp HTS synchronous motor developed in a few years ago has maximum field density of 1.5T. At this point, magnetic material used in conventional machines is able to pass magnetic flux easily with high permeability. In order to investigate the effect, we arranged magnetic core only inside of magnet vessel of a 100hp target machine. By way of FEM analysis, we concluded that the magnetic core can reduce amount of expensive BSCCO conductor so much.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.260-263
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• 1997

In this paper, we describe the mechanical strain effects on the critical current density of HTS (BSCCO) pancake-type-magnet. Firstly the strain of pancake coil is calculated in terms of coil length, which is also a function of angle, and then the critical current density degradation due to strain is calculated along the coil. We assumed that the critical current density degradation pattern is same with that of $Nb_{3}Sn$. We also modelled the effects of magnetic field on the critical curent degradation, and the results are compared with those with null magnetic field.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1228-1230
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• 2005

This paper deals with design of heater trigger switching in a persistent current system(PCS) by finite element method(FEM) analysis of YBCO coated conductor(CC) tape. Most promising superconducting wire is YBCO coated conductor tape in these days for its high n value and critical current independency from external magnetic field. It is expected to be used many superconducting application such as fault current limiter and cable etc. The superconducting magnet which is operated in persistent current mode in SMES, NMR, MRI and MAGLEV has many advantages such as a high uniformity of a magnetic field and reducing a thermal loss. A PCS system consists of magnet power supply (MPS) which energized current to a magnet, heater, a coated conductor tape for switching, and superconducting magnet. In this paper, the characteristic of thermal quench of the YBCO CC tape and BSCCO tape by heater trigger analyzed by FEM. And optimal length of heater is calculated by temperature and time analysis. This heater trigger analysis is expected to be a basic concept of PCS application design.

• Progress in Superconductivity and Cryogenics
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• v.5 no.2
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• pp.30-35
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• 2003

The inductive superconducting fault current limiter (SFCLJ limits the fault current with its dc reactor. To fabricate the optimal dc reactor for inductive SFCL, several design and manufacturing technologies are necessary. In this paper, the manufacturing technology for dc reactor and cryogenic cooling method are described in detail. GM-cryocooler was used enlarge the critical current of dc reactor by cooling down the temperature of dc reactor about 20 K. Moreover, the results of short circuit test were described. Finally, the thermal characteristics of conduction-cooled system were discussed and then, sub-cooled nitrogen system was proposed to enhance the thermal stability of dc reactor.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.196-199
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• 2003

Characteristics of a heater-triggered switch has been analyzed through the simulations and experiments. It was for the charging of Bi-2223 double pancake load with 1.7 mH and two heaters were used. The timing of the sequential control and the heating current with two heaters are important factors to generate pumping-current. The thermal analysis of the switch considering the heater input and time was carried out. Based on the analysis just mentioned. heater-triggered switch was fabricated. Characteristic analysis was carried out through two modes having different sequential timing controls. Maximum pumping-current reached 18 A and the pumping rate was 113 mA/s at that time.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.812-813
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• 2008

본 연구에서는 외부인가 자장을 위한 초전도 특성평가장 치용 레이스트랙형 초전도 마그네트의 개념설계를 하였다. 초전도 특성 평가장치는 외부인가 자장과 온도를 변화시켜가며 고온 초전도 선재의 특성을 측정할 수 있는 장치이다. 초전도 전력기기가 응용될 수 있는 온도범위인 $10K{\sim}77K$ 온도범위에서 초전도 선재의 특성을 평가하기 위해서 약 20cm 정도 길이의 시편이 차지하는 공간이 필요하고 이 공간에 1% 이하의 자장균일도와 최소 3T 이상을 가지는 마그네트가 필요하다. 이러한 조건을 만족시키는 초전도 마그네트는 필연적으로 레이스트랙형 마그네트를 가지는 split형이어야 한다. DI-BSCCO H type과 HT type 두 가지 선재에 대한 전자장 해석을 통하여 제한조건을 만족시키는 마그네트 설계를 하였다. 이렇게 설계된 초전도 마그네트는 초전도 특성평가장치 제작에 활용될 것이다.