PURPOSE: To design a small-sized, light-weight and low reactance machine by setting the axial length at the linear part of an air gap armature winding equal to or shorter than that of the coil of a superconducting field winding closest to the pole side.

CONSTITUTION: The axial length ('A') at the linear part of a honeycomb air gap armature winding 5 is set shorter than that ('B') of the coil 2a of a saddle type superconducting field winding 2 closest to the pole side and set substantially equal to that of the coil 2a at the linear part thereof. This structure realizes a generator producing higher output with the same constitution and synchronous reactance. In other words, a small-sized, light-weight and low reactance machine can be designed.