Persistent Current Analysis of Superconducting Coils in a Linear Synchronous Motor for Maglev Passenger Transport System

Abstract

In a superconductive linear synchronous motor for magnetically suspended trains, on-board superconducting coils experience space harmonic magnetic field generated by armature coils installed along the guideway. Current in a superconducting coil varies to keep total linkage magnetic flux constant when the coil is exposed in an external magnetic field.
In the conventional analysis, current in a superconducting coil was treated as constant, because the electromagnetic forces can be estimated easily and in sufficient accuracy compared to that obtained by constant flux mode analysis. However, it is important to know the behaviour of the persistent current to make reliable and tough superconducting magnets.
This paper proposed a simple method to analyze fluctuating persistent current in a superconducting coil, and discuss its characteristics through the typical calculation models.
Calculations for the normal running condition showed that the fluctuation of persistent current is less than one percent of the initial magnetomotive force. Then, the fluctuating magnetic field generated by armature coils will never affect stability for superconducting magnets, and the constant current mode analysis will predict accurate electromagnetic forces.