Improvement of a magnetically levitated stepping motor using high T/sub c/ bulk superconductor

A magnetically levitated stepping motor using high T/sub c/ superconductor has been studied. The levitated stepping motor consists of a cylindrical rotor with superconductors and a stator with eight electromagnets. The rotor measures 10 mm in diameter, 46 mm in length, and 18 g in mass. The superconductors of the rotor are field-cooled in liquid nitrogen. The levitated rotor is driven by four-phase and eight-phase excitations. The rotation angles by each step are 90 and 35 deg, respectively. The rotor spins as the excitation phase shifts one by one. This paper discusses the dynamics of the motor driven by the four-phase and eight-phase excitations.