Reduction of coupling current losses by internal resistive barrier structures in multifilamentary Bi(2223) tapes in external magnetic fields

AC Loss Reduction in Bi2223 Tapes with Interfilamentary Oxide Barriers

“…For the AC losses generated in the composite superconducting wire with normal metal matrix, it is widely known that the per-cycle coupling current loss component Q c generated in the matrix part show the maximum at coupling frequency f c , which is related to the decay time constant of coupling current τ c with following equation [3][4][5][6]:…”

“…Although Q c decreases with increasing the frequency when the operating frequency f op of a tape is higher than f c , the superconducting filaments start to couple each other and the hysteresis loss Q h becomes considerably larger than completely decoupled case, at the condition of field amplitude B 0 above the full penetration field B p [12]. To achieve a significant loss reduction by decoupling the filaments, therefore, the f c value should at least be higher than the operating frequency f op [3][4][5][6][8][9][10]. Fig.2 shows the frequency dependence of AC losses per-cycle Q m in a perpendicular field at 77 K for SrZrO 3 + Bi2212 barrier tapes with different L t .…”

“…The introduction of highly resistive layers as barriers around each filament is considered to be effective methods to increase the transverse resistivity [4][5][6][7][8][9][10]. The oxide material usable as the barriers should be highly-resistive, nonpoisonous to Bi2223 phase during heat treatment, and also should be easily deformed during cold working.…”

Fabrication and characterization of Bi2223 tapes with Al2O3 barriers for reduction of AC losses

“…The measured AC losses for all tapes are composed of the hysteresis loss (Q h ) in the filaments and the coupling current loss (Q c ). The Q c component per-cycle shows the maximum at characteristic frequency f c [4][5][6][7][8][9][11][12][13][14]. If the tape geometries and applied field direction are identical, the f c values are proportional to only the transverse resistivity (q t ) of tape.…”

Interfilamentary coupling properties of Bi2223/Ag tapes with oxide barriers subjected to AC perpendicular magnetic field

“…Most popular method for introducing barriers is the coating of oxide powder on the surface of monocore wire [5][6][7][8][9][10][11][12][13][14][15][16]. The oxide material usable as barriers should be highly-resistive, non-poisonous to Bi2223 phase formation during heat treatment, and also should be deformable during cold working such as drawing and flat rolling.…”