PURPOSE: To brake superconductors and obtain a stable superconducting state by dividing side spacers on the sides of a superconducting rotor, which has the superconductors fitted in a slot, into at least three pieces in the direction of the width of the slot, with the intermediate pieces of the divided spacers of wedge structure.

CONSTITUTION: The divided pieces 16a and 16c of side spacers 16 and an intermediate spacer 14 are arranged in a slot 7 and superconductors 8 are arranged between the intermediate spacer 14 and the spacers 16a. Spacers 16b are inserted between the spacers 16a and 16c. Because the spacers 16b have wedge-shaped cross sections in the direction of the depth of the slot 7, the sides of the superconductors 8 are fastened by the side spacers 16. Therefore, the superconductors 8 are not moved in the direction of the width of the slot 7 and frictional heat is not generated between the superconductors 8 and the side spacers 16, obtaining a stable superconducting state.