Analysis and performance of an axial-gap superconductor motor

The performance of a variable-speed, AC, superconducting motor has been evaluated. A novel axial-gap geometry was chosen for four-pole, 1800-r/min operation, using a superconducting stator and normal armature. The pool-boiling cryostat contains four solenoidal field windings of filamentary Nb-Ti conductor and has a maximum field of 7 T and an air-gap field of 2-3 T. The armature windings are formed from copper Litz wire and are arranged in 48 radial slots. The wires inside diameter and outside diameter are 17.18 and 69.24 cm, respectively. The armature is driven by three-phase power supplied via slip rings and an adjustable-speed drive. The maximum design power is 100 hp, which can be doubled by using two armatures. Motor-performance data as a function of speed and air-gap flux density are presented for initial low-power tests with a drive capable of delivering 60 A per phase to the armature.