• Progress in Superconductivity and Cryogenics
• /
• v.15 no.4
• /
• pp.48-52
• /
• 2013

This paper compares the features of second generation (2G) High Temperature Superconducting (HTS) field coil with those of magnesium diboride ($MgB_2$) field coil for a 10 MW class superconducting generator. Both coils can function effectively in their respective magnetic flux density range: 10-12 T for 2G HTS field coil, 2 T for $MgB_2$ superconducting field coil. Even though some leading researchers have been developing 10 MW class superconducting generator with 2G HTS field coil, other research groups have begun to focus on $MgB_2$ wire, which is more economical and suitable for mass production. However 2G HTS wire is still appealing in functions such as in-field property and critical temperature, it shows higher in-field property and critical temperature than $MgB_2$ wire.

• Progress in Superconductivity and Cryogenics
• /
• v.21 no.4
• /
• pp.29-33
• /
• 2019

2G HTS wire with high engineering current density is desired for applications where compact, high power density superconducting equipment is important. We have succeeded in enhancing engineering current density of commercial SuperOx 2G HTS wire based on GdBCO by increasing the HTS layer thickness without fast degradation of the HTS film microstructure. This was possible after improving the temperature uniformity along the HTS film deposition zone. In particular, the wire engineering current density was increased from 700-770 A/㎟ (for a 65 ㎛-thick wire without stabilisation) or 430-480 A/㎟ (for a 105 ㎛-thick stabilised wire) at the beginning of this study to almost 1200 A/㎟ (for a 67 ㎛-thick wire without stabilisation) or 770 A/㎟ (for a 107 ㎛-thick stabilised wire) at completion of this study.

• Progress in Superconductivity and Cryogenics
• /
• v.21 no.4
• /
• pp.24-28
• /
• 2019

Despite the second generation HTS tapes (2G HTS tape) have limits in critical current value, scientific and electric devices require more current density day after day. These requirements are realized by using different superconducting wires that consist of 2G HTS tapes designed in various combinations. Authors of this paper have developed the numerical model for estimation of total critical current in the superconducting wire and critical current in each 2G HTS tape placed in this superconducting wire. The current drop in six 2G HTS tapes having different constructions was analyzed. The result of this research is the decrease of critical current up to 25 % for the stack of tapes and up to 5 % for the parallel tapes in the same plane. In addition, what was also made is the estimation of the current distribution by length for six 25 m 2G HTS tapes in different constructions and determination of current deviation by length of the wire.

• Progress in Superconductivity and Cryogenics
• /
• v.9 no.1
• /
• pp.72-75
• /
• 2007

Magnetization loss of HTS wire is strongly dependent on the critical current density and the aspect ration of the HTS wire. This paper presents the magnetization loss of stacked BSCCO wire and stacked YBCO wires which had different critical current densities. Width of the BSCCO wire was 4mm and widths of two YBCO wires were 4mm and 8mm. Single wire, two stacked three stacked and four stacked wires were fabricated and tested. Ratio of magnetization loss of BSCCO wire to YBCO wire was presented at single wire. For stacked wire, ratio of magnetization loss of single wire to stacked wire was presented. Test results shows that magnetization losses of stacked wires were greater than that of single wire at large high magnetic field above critical magnetic field.

• Progress in Superconductivity and Cryogenics
• /
• v.9 no.1
• /
• pp.57-60
• /
• 2007

Superconducting electric power devices need to stack HTS wires to increase the current carrying capacity. Uniform multi-stacked wires(UMS) which were made of the same HTS wires have been used. This paper shows the magnetization loss of hybrid multi-stacked(HMS) wire made of BSCCO wires and YBCO wires. Five HMS wires, YB(YBCO-BSCCO), YYBB. YBYB, YBBY and BYYB, were made and tested. Magnetization losses of each UMS wire were compared with corresponding HMS wire. Test results show that magnetization losses per unit length of HMS wire are between the corresponding UMS BSCCO wire and HMS YBCO wire below critical magnetic field. Above the critical magnetic field, magnetization losses of HMS wires are larger than that of corresponding both VMS wires.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.3
• /
• pp.1166-1172
• /
• 2018

Degradation due to delamination occurs frequently in the high temperature superconductors (HTS) coil of rotating machines made with 2nd generation (2G) HTS wire, and the authors have observed other similar cases. Since an HTS field coil for a rotating machine is required to have stable current control and maintain a steady state, co-winding techniques for insulation material and epoxy resin for shape retention and heat transfer improvement are applied during coil fabrication. However, the most important limiting factor of this technique is delamination, which is known to be caused by the difference in thermal expansion between the epoxy resin and 2G HTS wire. Therefore, in this study, the experimental results of mixing the ratio of epoxy resin and alumina ($Al_2O3$) filler were applied to the fabrication of small and large test coils to solve the problem of degradation. For the verification of this scheme, eight prototypes of single pancake coils with different shapes were fabricated. They showed good results. The energization and operation maintenance tests of the stacked coils were carried out under liquid neon conditions similar to the operation temperature of an MW-class rotating machine. In conclusion, it was confirmed that the alumina powder mixed with epoxy resin in an appropriate ratio is an effective solution of de-lamination problem of 2G HTS coil.

• Progress in Superconductivity and Cryogenics
• /
• v.17 no.3
• /
• pp.37-40
• /
• 2015

Recently, the electrical insulation design for electrical apparatuses is important to cope with the tendency of high voltage. The degradation characteristics of a superconducting coil due to an electrical breakdown should be considered to design a high voltage superconducting coil. In this paper, the degradation characteristics of 2G high temperature superconducting (HTS) wires are studied with respect to electrical breakdown tests. To analyze the dependency of the degradation characteristics of 2G HTS wires, the electrical breakdown tests are performed with AC(alternating current) and DC(direct current) voltage. All tests are performed by applying various magnitudes of AC and DC breakdown voltages. To verify the degradation characteristics of 2G HTS wires, the tests are performed with various 2G HTS wires with respect to stabilizer materials. The degradation characteristics of 2G HTS wires, such as Ic(critical current) and index number are measured by performing electrical breakdown tests. It is found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it is concluded that the degradation characteristics of 2G HTS wires are affected by the stabilizer material and applied voltages. The cross-sectional view of 2G HTS wires is observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS wires are concerned with hardness and electrical conductivity of stabilizer layers.

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

• Proceedings of the KIEE Conference
• /
• 2006.10d
• /
• pp.71-73
• /
• 2006

AC loss on variation of external magnetic field is a very important factor in development of power applications. In this paper, we measured and compared AC loss of hybrid-multi stacked wire made of the combination of 1G wires and 2G wires and uniform-multi-stacked wire made of one type of wires, 1G wires or 2G wires. Measurement was performed using by the linked-picked coil method. As results, as the number of wires increase, AC loss per unit volume of both stacked wires in low external magnetic field is reduced. Also AC loss of 2G slacked wire is higher than that of 1G wire. AC loss per unit length of 2G stacked wire is less than that of 1G stacked wire. And AC loss of hybrid-multi stacked wire made of the combination of 1G wires and 2G wires was between uniform-multi-stacked wire made of 1G wires and 2G wires.

• 한국초전도학회:학술대회논문집
• /
• 2009.07a
• /
• pp.22-22
• /
• 2009