The motivation of applying superconducting field
windings was on the history of water cooling field windings.
By use of superconducting magnet for field winding,
larger magnetic induction Bg would be obtained then
larger output coefficient could be gotten. Larger Bg leads
to stater without iron core, then air-gap armature
winding could be introduced. (In conventional generators,
armature windings are placed in slots of iron core.)