Development of Conduction-Cooled Superconducting Split Coil for Metal Melting by DC Induction Heating

DC induction heating with a superconducting magnet has the capability to melt metal in a short time. We have been investigating high-temperature superconductor coils using REBCO-coated conductors to apply to dc induction heating. In order to obtain a large magnetic field for the aluminum melting examinations, we designed, prepared, and evaluated a split coil. The split coil pair was comprised of three rectangle-shaped double pancake coils on each side. The lengths of the outer short and long side and the inductance of each coil winding were about 270, 340 mm, and 200 mH, respectively. A coil winding contains about 700-m REBCO tapes. The arrangement of six coils was determined by their transport properties at liquid nitrogen temperature. The split coil pair was cooled by conduction cooling and evaluated the coil properties evaluated by excitation. It was confirmed that the split coil successfully generated the magnetic field according to design. The temperature of the coil was guessed at about 50 K according to the magnetic field dependence of the critical current at various temperatures for the tapes used in the split coil pair. We observed aluminum melting, although incomplete, after a rotation of 1200 r/min in 100 s, with a coil current of 114 A in the aluminum melting test. These results suggested the effectiveness of the REBCO split coil to the aluminum melting process but there is a room to improve the split coil especially as the conduction cooling.