Electromagnetic and Levitation Characteristics of a High-Temperature Superconducting Bulk Above an Electromagnet Guideway

Abstract

An electromagnet guideway unit (EMGU) that can form an electromagnet guideway (EMG) with only a small gap, or even no gap, between multiple EMGUs was designed. The magnetic characteristics of such EMGU(s), including the homogeneity of the magnetic field along the EMGU(s) and the transverse magnetic field distribution were first investigated. As expected, the EMGU(s) can provide a homogeneous magnetic field in order to levitate bulk superconductors. Simulation results from an EMGU model implemented in COMSOL Multiphysics were verified using experimentally measured data, which indicated the established model can be used for further study and analysis. Next, the levitation characteristics of a high-temperature superconducting (HTS) bulk above the EMGU, including the levitation force acting on HTS bulk due to its interaction with the EMGU, as well as the stability of the bulk when experiencing a lateral disturbance and when varying the current of the EMGU, were investigated through experiment and simulation. The behavior of the levitation force during re-magnetization of the EMGU indicated that a larger re-magnetizing current is needed to suppress the internal magnetic field (trapped field) obtained from the pre-magnetization process, thereby providing a repulsive force to the superconductor. The stability study showed that the HTS maglev system with an EMGU with adjustable current can not only deal with a reduction of the levitation force but can also increase the restoring force when the superconductor is disturbed laterally. Finally, in order to clarify the mechanism of these levitation characteristics, the internal electromagnetic characteristics of the HTS bulk were analyzed using a 2D model.