Experimental Characterization of a No-Insulation HTS Racetrack Coil Subjected to Travelling Magnetic Fields

To investigate the electromagnetic characterization of a high temperature superconducting (HTS) coil when subjected to travelling magnetic fields, a no-insulation (NI) racetrack coil was wound with YBCO coated tapes. For comparison, another HTS coil which has the same geometric and structural parameter was wound with insulated tape between the layers. The charge-discharge performance and other typical characteristics were investigated first. The terminal voltage fluctuation of the insulation (INS) coil during the critical current test proved that the NI coil has a better electrical stability. In addition, a flat stator which has traditional copper windings and a controllable three-phase inverter were introduced to provide travelling magnetic field. The HTS coils were injected with DC current and exposed to the external field generated from the stator, respectively. Different terminal voltage and current responses of the coils were measured by experiments. The INS coil burned out when the AC current in the stator rose up to 20 A @30 Hz but the NI coil kept stable during and after all the experiments even with excessive current in the coil. The terminal voltage and current results indicated that the NI coil, which is potentially going to perform as the field magnet of a HTS linear synchronous motor (LSM), has better electromagnetic stability when subjected to the external field from the stator and thus it shows better application prospects in the LSM.