Patent ID: 7679247

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 to provide for levitating the rotor; a stator assembly that is configured to receive an electrical current and to generate a magnetic flux therefrom; and at least one pole piece supported by said stator and having a cylindrical projecting section, in the form of a cylindrical member, having a cylindrical wall with a wall thickness extending downward toward said rotor face and including a lower surface that faces downward toward said rotor, and said projecting section is configured for channeling said magnetic flux toward said rotor to exert a magnetic lifting force upon said rotor upward and in said vertical direction such that said lifting force influences said vertical movement, wherein said rotor face defines a cutaway section cooperatively arranged with said projecting section in the form of an annular slot that is widthwise delimited by a pair of opposing upwardly extending peripheral sidewalls, having a width that is sufficient for receiving the wall thickness of the pole piece, and the sidewalls are arranged such that said projecting section is at least partially receivable in the cutaway section, between said sidewalls, responsive to the vertical movement of the rotor along said axis of rotation, and said annular slot has a floor that faces upward in a confronting relationship with said lower surface of said projecting section to define a gap, having a gap size, between said rotor and said pole piece, and said gap size changes in response to the vertical movement of the rotor along said axis of rotation, and said magnetic lifting force exhibits a gap sensitivity that is smaller as compared to a conventional gap sensitivity that would be exhibited in an absence of said cutaway section, and said rotor is operable in each one of (i) a large gap configuration corresponding to a large gap size, and (ii) a small gap configuration corresponding to a small gap size, and at least a selected one of the pair of sidewalls intersects a major surface of said rotor face to form a peripheral edge such that the peripheral edge joins the selected sidewall with the major surface, and in said large gap configuration a portion of said magnetic flux is oriented from said projecting section towards said peripheral edge to influence the magnetic levitation force such that the magnetic levitation force is larger as compared to a conventional large gap magnetic levitation force that would be exhibited in a conventional flywheel levitation apparatus having the same large gap size, and in the absence of said cutaway section.