Torque characteristics of a motor using bulk superconductors in the rotor in the transient phase

A motor using bulk superconductors in the rotor (bulk superconducting motor) is considered to achieve higher power density than conventional machines. When the bulk superconducting motor is operated with slip, for example at startup or during overload operations, traveling electrical fields are applied to the bulk superconductors. In slip operation, the characteristics of the motor are complex because, under the traveling field, flux flow occurs in the bulk superconductors, which causes the increase in the current but at the same time generates heat, which decreases the critical current density of the bulk superconductors. In order to analyze the characteristics of the bulk superconducting motor in the transient phase and those of a bulk superconductor in traveling fields, pull out tests and locked rotor tests were performed using an experimental apparatus for a hysteresis motor with bulk superconductors in the rotor. Numerical analysis when operated with slip was also performed to know the electromagnetic phenomena in the bulk superconductor used in the motor when the effect of the heat is ignored.