Superconducting axial bearing for induction machines with active radial magnetic bearings

A superconducting passive axial bearing has been developed for an induction machine with vertical rotor and two active radial magnetic bearings, resulting in a fully levitating system. This prototype has been designed on the basis of a previous one reported by Salazar-Stephan as a 4-pole 2-phase induction machine using windings of a standard motor. Each active radial bearing measures four shaft-positions using eddy-current sensors, each displaced by 90 degrees. The levitation has been performed using two NdFeB permanent magnets and bulk pieces of seeded-melt-textured YBCO. The YBCO pieces have been characterized by measuring the levitation forces and mapping the remanent magnetic field with Hall probes. The radial stability of the system is modeled and discussed.