Electromagnetic-vibrational behaviors of bulk high-temperature superconductor containing slot defect under permanent magnet motion

Abstract A bulk high-temperature superconductor (HTS) employed in the high-temperature superconducting levitation device is susceptible to cracks or defects during its fabrication and utilization. This may cause changes in the electromagnetic (EM) and vibrational behaviors of the HTS, even affecting the normal operation of the device. To this end, based on the magnetic, thermal and motion field equations for the transversely isotropic superconducting material, we establish a 3D coupled model of a levitation system containing an HTS with a slot defect and permanent magnet (PM), to investigate the vibrational and EM behaviors of the HTS with the defect above the PM, and discuss the effects of the depth of the defect, frequency of the external excitation, and combined defect on the behaviors in the time or frequency domains. The results show that the intrinsic frequencies of the HTS with defects of different depths are in the ranges of 6–8 Hz, 13–16 Hz and 19–20 Hz. With the increase of the defect depth, the intrinsic frequencies and EM losses increase but the vibration amplitude decreases. Under the action of the simple harmonic excitation with the same amplitude, the larger the defect depth, the lower the vibration amplitude and the better the stability of the phase trajectory. With the increase of the excitation frequency, the vibration amplitude decreases and the losses increase. However, when the excitation frequency is close to the intrinsic frequency, the HTS resonates and its internal fluxes undergo the violent motion. When the HTS contains a composite defect consisting of two single defects, its intrinsic frequencies are higher than those for the HTS with either defect included. And its EM losses are greater than the sum of their losses. The modeling method presented here can provide an idea and a reference for the research of EM-vibration behaviors of superconducting levitation systems containing defects.