High Temperature Superconducting Quasi-Permanent Magnets and Their Application to Superconducting Motor

Abstract

We succeeded in obtaining Y-Ba-Cu-O superconducting bulk magnets (abbreviated as Supermagnets) which can trap the magnetic fields exceeding those of ordinary permanent magnets. The flux motion during the pulsed field magnetization (PFM) was evaluated at 77 K. The flux penetration into the sample is sluggish when the field is low, but it suddenly penetrates when the external field exceeds 1.5 T. The PFM technique was applied at temperatures below 77 K to magnetize Supermagnets. The highest flux density of 2.1 T was achieved at the surface of the sample when magnetized by PFM at 30 K by using a cryocooler.
A superconducting motor was constructed for the first time in the world by using Supermagnets as field magnets. The motor performances at 77 K and 65 K reached the values of 2 kW and 3.5 kW, respectively. We have technically established that Supermagnets can be used in various practical applications.