Levitation force transition of High-Tc Superconducting bulks within a maglev vehicle system under different dynamic operation

In the practical application of a High-Tc Superconducting (HTS) maglev vehicle, the onboard HTS bulks are inevitably exposed to a varying inhomogeneous magnetic field due to limited magnetic field precision during the processing and assembling of the permanent magnetic guideway (PMG). To explore the levitation force of YBa₂ Cu₃O_7-x bulk samples with respect to a PMG in such changing external magnetic fields, we study experimentally the wave detail and general transition of the levitation force at different dynamic operation modes with the aid of a spinning circular PMG. The rotation of the circular PMG simulates translational movement of the superconductor with respect to a PMG and the rotational speed was set under several shift processes for simulating the different running operation speeds of HTS maglev vehicle. The highest linear equivalent experimental speed was 238 km/h. The change in levitation force was almost instantaneous in accordance to the varying of the vertical component of the applied field, and generally attenuated with running time. The saturation behavior after a change in speed was discussed thoroughly. This observed phenomenon is of great importance in the design and application of the HTS maglev system.