Low Loss Bi:2212 Superconductors for Electric Aircraft

This work presents recent results on a low loss Bi:2212 superconductor strand which has great promise for electric aircraft applications. AC loss measurements are presented which show low hysteretic as well as low eddy-coupling current losses. The strands ranged from 0.30 mm down to 0.16 mm OD, and contained 54 filaments. M-H was measured from -1 T to 1 T, with ramp rates up to 70 mT/s, at 4 K, 20 K, and 40 K. The M-H loops were integrated to give Q vs dB/dt, and hysteretic and coupling current components of the loss were extracted. With the use of standard expressions it was possible to extract deff values (a key parameter for hysteretic loss), as well as effective transverse resistivity values, ρeff, an important metric for coupling currents. Values of deff = 50-100 μm were seen, as well as ρeff ≅ 2-3 μΩ cm. When AC losses for the strands are projected into the regimes of interest, taken to be 200-300 Hz, at 0.5 T sweep, and the values are beginning to be competitive with very low loss MgB2 conductors and are relevant to electric aircraft needs.