3-D Modeling of Current Decay in a Closed HTS Racetrack Coil Under Traveling Magnetic Fields

High temperature superconducting (HTS) magnets working in persistent current mode (PCM) have shown a superior potential in electrodynamic suspension (EDS) train applications. When exposed to the external traveling magnetic fields generated by the propulsion coils, the on-board HTS coils used as the secondary of synchronous motor will suffer a non-negligible loss resulting from dynamic resistance which is much larger than caused by joint resistance. In this work, we build a 3-D finite element model of a real scale HTS racetrack coil to predict its behaviour. In the modeling, homogenization technique and the symmetry plane are adopted for accelerating computation, and the proper boundary conditions are used for field-cooling excitation as well as applying traveling fields. Firstly, the effectiveness of the model has been validated by comparing with experimental results of a small prototype. Then based on the method, a real scale HTS racetrack magnet model with the symmetry modified as to adapt the EDS scenario is built for investigating the current decay property varying with the external fields. Moreover, the effect mechanism of the instantaneous AC loss on the current attenuation is deeply analyzed.