AC loss reduction of YBCO coated conductors by multifilamentary structure

TLDR

YBCO coated conductors have a large aspect ratio that causes significant magnetization loss in transverse AC magnetic fields. This study experimentally investigates the magnetization loss of a multifilamentary YBCO coated conductor. A 100‑mm long, laser‑ablated, 10‑mm wide YBCO conductor with 0.4‑mm filaments was tested for magnetization loss in transverse AC fields across a range of frequencies. Striation reduced magnetization loss to under 9 % of the non‑striated conductor at 11.3 Hz, and the reduction persisted up to 171 Hz despite increased coupling loss; the measured transverse resistance (38 µΩ/m at 80 K) implies a coupling length exceeding the sample length, so the filaments remain largely decoupled.

Abstract

The large cross-sectional aspect ratio of YBCO coated conductors leads to a large magnetization loss in an AC transverse magnetic field. In this work, the magnetization loss of a multifilamentary YBCO coated conductor was studied experimentally. A 100 mm length of striated multifilamentary YBCO coated conductor was prepared where the conductor and filaments were 10 mm wide and 0.4 mm wide, respectively. Striations in the sample were accomplished by laser ablation. The magnetization loss of this striated conductor as well as a reference non-striated conductor was measured in AC transverse magnetic fields normal to the conductor at various frequencies. The measured magnetization loss of the 100 mm striated conductor was less than 9% of the measured loss of the non-striated conductor at f = 11.3 Hz and H/Hcc = 8.8 (Hcc = Ic/πwc; Ic: critical current, wc: conductor width). Even though the coupling loss component increases the magnetization loss in the striated conductor, the AC loss reduction by striation is still apparent even at 171.0 Hz. The transverse resistance between filaments estimated by a four-probe measurement was 38 µΩ for 1 m at 80 K. The coupling length estimated using this transverse resistance is much longer than the sample length even at 171.0 Hz, suggesting that the filaments in the striated conductor are far from 'completely coupled' or 'saturated'.