In a superconductive electrodynamic suspension system, superconducting coils experience space harmonic magnetic field generated by induced current in the levitation coils installed along the guideway. Current in a superconducting coils varies to keep the total magnetic flux constant when the coil is exposed in an external magnetic field. However, superconducting coil current was treated as constant in the conventional analysis, because the electromagnetic forces can be estimated easily.
The purpose of this paper is to know the behaviour of the persistent current to make reliable and tough superconducting magnets. A simple method to analyze fluctuating persistent current in a superconducting coil is proposed at first. Calculated results for the normal running condition showed that the fluctuations of persistent current is less than 1% of the initially excited current for the side-wall levitation system, and less than 2% for ground levitation coil system. Even when the null flux guidance cable is short-circuited, the fluctuation is less than 5%. Considering that the magnetic shield effects by the conductive cryostat vessels was neglected in this analysis, the fluctuating magnetic field by levitation coils will never affect stability for a superconducting magnet.
J-STAGEがリニューアルされました！https://www.jstage.jst.go.jp/browse/-char/ja/
