Characteristics of 300-Turn Smart Insulation Race-Track Coil in External Fluctuating Magnetic Field

Experiments and finite-element analyses were conducted to investigate the characteristics of a 300-turn smart insulation (SI) coil coated with vanadium trioxide (V
₂
O
₃
) placed in an external fluctuating magnetic field. The external fluctuating magnetic field generator was designed to allow sliding insertion through a fabricated non-rotating liquid-nitrogen tank inside the stator of a 1-MW superconducting rotating machine. The 300-turn SI coil was fabricated in a two-layer design with 150-turn windings in each layer. Experiments were conducted in such a manner that the SI coil did not rotate during the generation of the external fluctuating magnetic field owing to the rotating magnetic field of the stator. The SI coil with many turns showed no magnetic field delay because of the ramping time,thereby demonstrating controllability equivalent to that of a normal insulated coil. The stability of the SI coil was confirmed via repeated overcurrent tests, with and without an external fluctuating magnetic field.