Current status of superconducting synchronous motor in Saga University

Since there are no iron cores in the rotor and stator windings of superconducting synchronous motors, some reactances are intrinsically smaller than those of conventional motors. Low synchronous reactance would be expected to improve the torque-ampere ratio stability and the overload capacity of superconducting machines. Two types of 30 kVA synchronous motors, such as rotating armature and rotating field types, have been constructed. The rotating armature type motor had been fabricated and tested. The results show the difficulty of holding a stator cryostat in a low-heat leak condition. The low synchronous impedance requires some control of the armature current and/or the motor field current. The rotating field type motor encountered balancing problems due to the triple-pipe configuration of the helium supplier in the torque tube.