• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제52권11호
• /
• pp.557-562
• /
• 2003

To develop a stable and compact small-sized superconducting magnetic energy storage (SMES) system, which provides electric power with high quality to sensitive electric loads, we fabricated a SMES coil and tested it. Because such a large-sized superconducting coil quenches far away from its critical current, the recovery current is frequently used as a stability criterion in the coil fabrication. Therefore, we first investigated the recovery current characteristics of the large current conductor, which was used in our SMES coil fabrication. The test results indicate that the recovery currents measured in the conductor are nearly identical to those based on the single wire. This implies that the recovery current is affected by the conductor's cooling condition rather than its size and current capacity. In the SMES coil test the first quench occurred at 1250 A, which is equivalent to the stored energy of about 2 MJ. It corresponds to the quench current density of about $130A/mm^2$ This value is much higher in comparison with that reported in the other work. In addition, the first quench current of the coil agrees well with the measured recovery current of the conductor having similar cooling condition with it. This means that to determine the recovery current of a conductor is, first of all, important in the design and fabrication of a large-sized superconducting coil.

• 한국초전도ㆍ저온공학회논문지
• /
• 제24권1호
• /
• pp.1-7
• /
• 2022

So far, large-scale scientific devices such as nuclear fusion tokamaks and high energy circular accelerators were constructed using high-current conductors made of metallic superconducting wires. Recently, as REBCO superconducting wires usable in high magnetic fields have been developed by several companies, researchesto apply high current cable type REBCO conductors to next-generation large superconducting magnets were also started. High critical currents of several kA or more in high magnetic fields have been successfully demonstrated on test samples of REBCO cable conductors by several research groups. In this review article, the main features and properties of the representative high current REBCO conductors such as CORC(Conductor On Round Core), TSTC(Twisted Stacked-Tape Cable) and RACC(Roebel-Assembled Coated Conductor), which are currently being developed at abroad are briefly introduced. Research activities of high-current density REBCO MHOS(Multi HTS layers on One Substrate) conductor at KERI, whose structure is different from other cable type REBCO conductors are also shortly introduced.

• 한국초전도ㆍ저온공학회논문지
• /
• 제10권1호
• /
• pp.32-36
• /
• 2008

An HTS conductor with parallel HTS tapes is essential for a large power HTS device to flow a large current. One of the most important factor for this conductor is a current distribution. Non-uniform current distribution in parallel tapes makes the critical current of the conductor low and the AC losses high. In this paper we proposed a non-contact method which measured each current in parallel tapes by using an array of Hall sensors. A matrix can be derived from this array for calibration. The current distributions of 4 and 6 parallel tapes were measured.

• 한국초전도ㆍ저온공학회논문지
• /
• 제12권3호
• /
• pp.16-20
• /
• 2010

For large scale power applications of HTS conductor, it is getting more important to have a stacked HTS coated conductor with low loss and large current capacity. But it was not easy to measure some electric properties. Stabilizer free YBCO CC for striated/ stacked conductors is easily burned out during the measurement of the critical current density because it has no stabilizer and it is difficult to set-up the current lead and voltage taps because it has many pieces of YBCO CC in a conductor. Instead of direct measuring the critical current of a stacked HTS coated conductor, indirect estimation from measuring a magnetization loss of HTS coated conductor could be useful for practical estimation of the critical current. The magnetization loss of a superconductor is supposed to be affected by a full penetrating magnetic field, and it tends to show an inflection point at the full penetrating magnetic field when we generate the graph of magnetization loss vs. external magnetic field. The full penetrating magnetic field depends on the shape of the conductor and its critical current density, so we can estimate the effective critical current density from measuring the magnetization loss. In this paper, to prove the effectiveness of this indirect estimation of the critical current, we prepared several different kinds of YBCO CC(coated conductor) including a stacked conductor short samples and measured the magnetization losses and the critical currents of each sample by using linked pick up coils and direct voltage measurement with transport current respectively.

• 한국초전도ㆍ저온공학회논문지
• /
• 제25권4호
• /
• pp.40-44
• /
• 2023

For high-temperature superconducting power applications that need large current capacity, a large current conductor manufactured using multiple superconducting tape is required. Conductors being studied for large currents capacity such as CORC, TSTC, and RACC have advantages and disadvantages, and in order to use these conductors in coil form and apply them to AC power devices, research on magnetization loss occurring in superconductors due to external magnetic fields is essential. To accurately measure magnetization loss in a conductor that is twisted by stacking straight conductors like TSTC, the correlation between the measuring system and the shape of the sample must be clearly known to accurately measure the loss. In this paper, we will confirm the difference in magnetization loss measurement values according to the correlation between the length of the pickup coil and the twist pitch of the sample in CORC and TSTC shapes, and review considerations for accurate magnetization loss measurement from the results.

• 한국초전도ㆍ저온공학회논문지
• /
• 제24권4호
• /
• pp.46-49
• /
• 2022

Since CORC^®(Conductor on Round Core) is made of multiple strands of a superconducting tape to conduct a large current, it is difficult to measure the critical current due to the limitation of a capacity of a power supply. The magnetization loss of a superconductor is dependent on the full penetration field. The full penetration field corresponds to the inflection point of the magnetization loss graph with respect to the external magnetic field. We propose a method to predict the critical current of CORC^® indirectly. This method uses the measured magnetization losses of various CORC^® samples for the prediction of the critical currents.

• 한국초전도ㆍ저온공학회논문지
• /
• 제23권4호
• /
• pp.10-13
• /
• 2021

Recently, cable conductors composed of numerous coated conductors have been developed to transport huge current for large-scale applications, for example accelerators and fusion reactors. Various cable conductors such as CORC (Conductor on round core), Roebel Cable, and TSTC (Twisted stacked tape cable) have been designed and tested to apply for large-scale applications. But, these cable conductors cannot improve the engineering critical current density (J_e) because they are made by simple stacking of coated conductors. In this study, multi-HTS (High temperature superconductor) layers on one substrate (MHOS) wire was fabricated to increase the engineering critical current density by using the exfoliation of superconducting layer from substrate and silver diffusion bonding method. By the repetition of these processes, the 10 m long 6-layer MHOS conductor was successfully fabricated without any intermediate layers like buffer or solder. 6-layer MHOS conductor exhibited a high critical current of 2,460A/12mm-w. and high engineering critical current density of 1,367A/mm² at liquid nitrogen temperature.

• 한국전기전자재료학회논문지
• /
• 제21권1호
• /
• pp.79-84
• /
• 2008

We are developing a small-sized high temperature superconducting magnetic energy storage (HTS-SMES) magnet with the nominal storage capacity of 600 kJ, which provides electric power with high quality to sensitive electric loads. Critical current and N-value of a high temperature superconductor with large current, which was selected for the development of the 600 kJ HTS-SMES magnet, were investigated in various oblique external magnetic fields. Based on the critical current and N-value measured for the short sample conductor, we discussed the DC V - I characteristic of a model coil fabricated with the same conductor of 500 m. The results show that the measured critical current and N-value of the conductor for parallel field are constant in external magnetic fields less than about 0.2 T. However, for oblique fields, its critical current and N -value abruptly decrease in all external magnetic fields. Moreover, the measured critical current of the model coil well agrees with the numerically calculated one based on the DC V - I characteristic measured for the short sample conductor. This suggest that losses and critical currents for an HTS-SMES magnet made up of a high temperature superconductor with anisotropic characteristic are predictable from the data of a short sample conductor.

• 전기학회논문지
• /
• 제59권1호
• /
• pp.51-56
• /
• 2010

AC loss is main issue for power applications using YBCO coated conductor. The striated YBCO CC(Coated Conductor) has been proposed by several researchers to decrease a magnetization loss. A continuously transposed coated conductor (CTCC), suggested by our research group before, could be very useful for lower magnetization loss of large current power applications. In this paper, an AC loss reduction effect by the stack, striation and transposition of YBCO CCs under a time varying external magnetic field. To estimate the reduction effects for perpendicular magnetization loss, several CTCC samples were prepared and tested. Also, we measured angular dependency of magnetization losses of various CTCC samples.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.1159_1160
• /
• 2009

본 논문에서는 초고속 자기부상열차의 유력한 후보가 될 수 있는 초전도 반발식 자기부상의 특성을 연구하기 위한 반발력을 3차원 유한요소 자기 해석을 통하여 계산하고 분석하였다. 본 해석의 결과에 따르면 움직이는 부분이 없는 정지형 시험기는 반발식 자기부상시험기로써 적용될 수 있다.