Patent ID: 8314527

Claim:
A flywheel levitation apparatus for a flywheel driven power storage system, said apparatus comprising: a rotor having a rotor face, that faces upward in a vertical direction, and an axis of rotation that is at least approximately aligned with said vertical direction, and said rotor is supported for (i) rotation around said axis and (ii) a limited amount of vertical movement along the axis that is sufficient to provide for levitating the rotor; a stator assembly that is configured to receive a variable electrical current and to generate a variable magnetic flux therefrom which varies responsive to changes in said variable electrical current; and at least one pole piece supported by said stator and having a projecting section, extending downward toward said rotor face, for channeling said variable magnetic flux toward said rotor to exert a variable magnetic lifting force upon said rotor upward and in said vertical direction such that said variable magnetic lifting force at least provides a component of a total lifting force to influence said vertical movement, wherein said rotor face defines a cutaway section such that said projecting section is at least partially receivable in the cutaway section responsive to an upward vertical movement of the rotor along said axis of rotation, and said variable magnetic lifting force exhibits a modified gap sensitivity that is smaller as compared to a conventional gap sensitivity that would be exhibited in an absence of said cutaway section.