• 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
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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.

• Progress in Superconductivity
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• v.5 no.1
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• pp.61-64
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• 2003

In HTS transformer with double pancake windings, the perpendicular component of leakage magnetic flux density ($B_{r}$ ) applied to HTS tapes of double pancake windings of HTS transformer acts as a cause to decrease the critical current in HTS tape. So, in this paper, HTS transformer with reciprocal arrangement winding is designed. And in order to investigate the$ B_{r}$ applied to HTS windings, the 2-D non-linear electromagnetic analysis of HTS transformer is performed by using the OPERA 2D. The maximum $B_{r}$ applied to winding of HTS transformer is 0.112 T and the characteristics of HTS transformer were also obtained. But in this type of winding arrangement, reciprocal arrangement, the generated ac-loss to the HTS windings is very high because of the applied $B_{r}$ to HTS windings. Therefore, in order to reduce the generated ac-loss to the HTS windings, the new design of HTS transformer with concentric winding arrangement is presented in this paper and the 2-D non-linear electromagnetic analysis and the ac-loss for HTS transformer with the concentric winding arrangement is also carried out.

• Progress in Superconductivity and Cryogenics
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• v.2 no.2
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• pp.37-43
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• 2000

This paper describes the construction and test results of a 10kVA single phase HTS transformer. Double pancake windings with BSCCO-2223 HTS tape and G10-FRP cryostat with room temperature bore are used in the transformer. Two double pancake windings are connected in series to provide 188 turns and other two double pancake windings are connected in parallel to conduct the secondary current of 45.4[A]. Coefficients of the constructed transformer are obtained using the fundamental teats of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounds the sryostat.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.321-323
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• 2000

This paper describes the construction and test results of a 10kVA single phase HTS transformer. Double pancake windings with BSCCO-2223 HTS tape and GFRP cryostat with room temperature bore are used in the transformer. Two double pancake windings are connected in series to provide 184 turns and two double pancake windings are connected in parallel to conduct the secondary current of 45.4A. Coefficients of the constructed transformer are obtained using the fundamental tests of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounded the cryostat.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.246-249
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• 2003

AC loss which is generated in an HTS wire varies with the direction of the magnetic field. This paper calculated and measured the AC loss in the HTS double pancake windings. Brandt equation is used to calculate the loss by perpendicular magnetic field. Calorimetric method is used to measure the AC loss. Results of calculated AC loss are compared with measured AC loss.

• Progress in Superconductivity and Cryogenics
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• v.4 no.2
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• pp.31-37
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• 2002

A 100 〔HP〕 rated synchronous motor with superconducting rotating field winding has been designed based on the formulated equations established from 2 dimensional magnetic field distributions in a cylindrical coordinate The cross-section was drawn based on calculated design results via Fortran program and then modeled with FEM (Finite Element Method) to investigate the machine performances. First of all, the magnetic field distributions are analysed in many ways according to the field directions and the armature currents. Especially after the rotating Held winding is arranged with BSCCO-2223 high-temperature superconducting(HTS) pancake coils, the exerted magnetic field normally on the HTS tape is calculated through FEM. And the machine output power is calculated according to the torque ang1es which lie between the field and the armature main flux lines. Moreover, this Paper includes the eddy-current loss variations of a copper damper located between the field and the armature coils and design considerations of the 100 HP HTS motor utilizing ferro-magnetic material.

• Progress in Superconductivity and Cryogenics
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• v.9 no.2
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• pp.7-10
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• 2007

Persistent mode HTS pancake coil has been fabricated using a coated conductor by a "wind-and-flip" method. A coated conductor with the length of 1.2 meters was divided at the center along the length. The sliced coated conductor was wound on a pair of bobbins with a diameter of around 4 cm and two pancake coils connected superconductively without a resistive joint were prepared. By flipping one of the pancake coils, the magnetic field generated by each coil is to be aligned to the same direction and generate meaningful magnetic field while the magnetic fields of two spit coils are canceled without flipping. Permanent current was induced by flowing current to the coil immersed in liquid nitrogen pool using a power supply. A magnetic field of 48.8 Gauss was generated when 20 A of current was flowing in the pancake coils. The "Wind and flip" method can be applied for the fabrication of a long solenoid magnet by winding a sliced coated conductor on a cylindrical bobbin. It is also introduced that the construction of multiple sets of pancake (or solenoid) coils is possible by a "wind-and-flip" method using a wide coated conductor.

• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.50-53
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• 2015

The properties of High Temperature Superconducting (HTS) tapes are progressing, as HTS tapes evolve from 1st generation to 2nd generation. This paper presents design and construction of a 2nd generation HTS magnet consisting of two nested GdBCO and YBCO pancake coils. Two HTS tapes of different widths were used to wind the HTS nested magnet. Considering that a higher magnetic field is applied to the inner magnet than to the outer magnet, 12 mm GdBCO tape was used for winding the inner magnet, which consisted of four single pancake windings. Eight double pancake windings wound with 4.4 mm YBCO tapes were used for the outer magnet. The test results show that the central magnetic field of the HTS nested magnet was 920 mT. The measured critical currents of the inner and outer magnet at 77K were 80.8 A and 32.6 A, respectively.

• Progress in Superconductivity and Cryogenics
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• v.13 no.4
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• pp.26-29
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• 2011

In a High temperature superconducting (HTS) tape with high aspect ratio, the magnetic field applied to the HTS tape can be different considerably within the HTS tape. The current distribution in the HTS tape is generally non-uniform because the current distribution is strongly dependent on the applied magnetic field. Non-uniform current distribution in a HTS tape has not been properly considered when the critical current has been estimated. This paper shows the calculation of critical current of a HTS magnet consisting of pancake windings. Non-uniform distribution of current in the HTS tape is considered during the calculation of the critical current. Results of calculation show the current concentrated in the middle part of the HTS tape which is used for one pancake winding.