Development and Testing of Hybrid HTS Conductor for Steady-State High-Current Applications

Second-generation rare Earth REBCO high-temperature superconductors (HTSs) exhibit a high critical current density and a higher critical magnetic field. HTS materials have the potential to generate magnetic fields that overcome the limitations of low-temperature superconductors. A hybrid high-temperature superconductor (HHTS) was developed by soldering five HTS strips (GdBCO, SUNAM Korea, and 4 mm in width) without insulation (NI) into a copper stabilizer. In addition, five NI-HTS strips without stabilizers were tested at room temperature and in liquid nitrogen (LN2). For the HTS strips, a maximum stable current of 270 A (at LN2 temperature) was achieved at 0.08 V, beyond which the current dropped sharply. The critical electric field (Ec) calculated from the voltage drop was 14 μV/mm. The HHTS demonstrated a current-carrying capacity up to 1000 A at an applied voltage of just 0.2 V and a corresponding electric field of 6.8 μV/mm. The simulation of HHTS was performed by using H-formulation at the cross section, applying currents from 500 to 1000 A, while varying the stabilizer width to 7, 9, and 12 mm. The results indicate stable current conduction up to 1000 A. The copper matrix provides stability during interruption in the cooling system, and the electric field in the HHTS allows operation at higher currents, offering advantages in voltage control and cooling efficiency.