The importance of interfilamentary barrier resistance in YBCO coated conductor to minimize ac losses

-Striating HTS coated conductor (CC) tapes into narrow filaments offers the possibility of reducing the tapes' magnetization losses without unreasonably decreasing their current-carrying capability. However, realizing well-separated striations presents technological challenges, especially if the number of filaments is large and/or if a thick layer of metallic stabilizer is present. In these situations, the filaments can be easily coupled and their effectiveness to reduce magnetization losses is strongly diminished or eliminated. While the onset of coupling is well visible from magnetization loss measurements, the actual path of the coupling current is unknown. In this contribution we present a systematic study of the transverse resistance in HTS CC samples in order to get a deeper understanding of those paths. The measured samples differ in terms of manufacturer (SuperPower and SuperOx), and presence and thickness of stabilizer material. In addition, oxidation is used as a means to increase the resistance between the filaments in non-stabilized samples. The results are interpreted with a chain network model. This work provides useful insights on the factors determining the transverse resistance in striated HTS CCs, thus indicating ways to improve the effectiveness of the striation process for AC loss reduction.

Section: Introductionmentioning

confidence: 99%

Interfilament Resistance at 77 K in Striated HTS Coated Conductors

Gyuráki

Godfrin

Jung

et al. 2016

“…The problem for power generator armature windings is that complex bends are required to interlace the phase belts in most winding configurations. The Gramme ring winding [7] requires no twist with the Rutherford architecture which provides already transposed filaments. A fault current limiter may use the Rutherford tape configuration to advantage if the cooling and protection issues are addressed.…”

Section: Potential Applications For the Rutherford Tapementioning

confidence: 99%

“…After applying the bottom YBCO coating (Fig. 6) on the buffer protected metal substrate, filamentary barriers are produced [7]. Laser cut barriers couple the filaments through the substrate by redeposited material and the transverse resistivity becomes too low to be effective for high frequency [8].…”

Section: Process Limitations For the Rutherford Configurationmentioning

confidence: 99%

Conceptual approach to the ultimate low AC loss YBCO Superconductor

Oberly

Razidlo

Rodrı́guez

2005

Wide tapes of YBCO coated conductors make minimization of ac loss very difficult. Subdivision of the tape into narrow filaments does not provide complete transposition when twisted and current sharing is not equalized due to inductance differences. For ac power applications operating near 400 Hz for military aircraft power systems, equal inductance filaments and short twist pitch are very important to loss minimization. A fully transposed YBCO tape that approximates a Rutherford cable has been conceived to minimize ac loss at high frequency. Retention of optimal texture of YBCO in edge turnaround regions and filament crossovers in the Rutherford tape is essential.

“…Although expected AC losses reduction has been shown over short segments of multifilamentary tapes [10], coupling losses need to be suppressed by transposing the filaments in order for this technique to be effective over long lengths [11]. Some solutions based on tape cabling techniques [12] have been proposed to solve the coupling issue where the tape is bend and/or twisted to achieve the transposed configuration.…”

Section: Introductionmentioning

confidence: 99%

AC Loss Reduction in Multifilamentary Coated Conductors With Transposed Filaments

Yahia

Majoroš

et al. 2017

Filamentization has been shown to be an effective method in reducing magnetization AC loss of RE-Ba-Cu-O (REBCO) coated conductors. We have used a laser striation method followed by selective electroplating of copper to fabricate fully-stabilized multifilamentary REBCO tapes with 12, 24 and 46 filaments. While expected levels of AC loss reduction has been confirmed in short segments of such multifilamentary tapes, electric coupling between the filaments of long tapes needs to be suppressed by transposition of the filaments. In this work, a technique was developed and implemented to reduce AC losses in REBCO multifilamentary coated conductors through a new design that allows to transpose the filaments without any mechanical twisting. The process consists of patterning REBCO tapes by laser ablation followed by partial insulation and bonding. A twofold reduction of AC magnetization losses was achieved in the transposed multifilamentary REBCO tape when subject to an external perpendicular magnetic field at frequencies between 50 and 200 Hz and peak field values up to 88 mT. The filament-tofilament resistance and its effect on the coupling has also been investigated.