Study on improving levitation stability from high frequency vibration for the application of a seismic isolation device

Abstract

The stability of superconductor levitation is depending on the pinning force. However, when an external force such as the earthquake with a high magnitude higher than the pinning force is exerted, the levitated permanent magnet (PM) can become unstable and destroyed. In order to improve the stability of the levitation, a copper plate was inserted in between the HTS (high temperature superconductor) bulk and the PM. And the more stabilized levitation can be achieved by applying eddy current that is caused by PM and the copper plate. In this study, various arrangements of PM, the thickness of copper plate, the area and gap length between PM and the copper plate were carried out. The eddy current was greater in the arrangement where polarity was changed with parallel to a moving shaker than the arrangement where polarity was not changed. And also, the eddy current became greater as the gap length between the PM and copper plate decreased. The highest value of the eddy current was measured at a copper plate thickness of 5 mm and a size of 80 mm x 80 mm. From the eddy current experiments, a copper plate (80 mm x 80 mm x 5 mm) inserted between the 7 mm gap length of the HIS bulk and the PM was resulted in a higher stiffness value of 65% compared to no copper plate stiffness value.