Electrostatic stabilizer for a passive magnetic bearing system
View Patent ↗Electrostatic stabilizers are provided for passive bearing systems composed of annular magnets having a net positive stiffness against radial displacements and that have a negative stiffness for vertical displacements, resulting in a vertical instability. Further embodiments are shown of a radial electrostatic stabilizer geometry (using circuitry similar to that employed in the vertical stabilizer). This version is suitable for stabilizing radial (lateral) displacements of a rotor that is levitated by annular permanent magnets that are stable against vertical displacements but are unstable against radial displacements.
1. An apparatus, comprising:
a right cylindrical rotor configured for rotation about a longitudinal axis, wherein said rotor comprises a metallic outer cylindrical surface;
a passive magnetic bearing system configured to provide at least axial stabilization of said rotor as said rotor rotates;
a first plurality of pairs of electrodes, wherein each electrode of each pair of said pairs is spaced from each other electrode and from said metallic outer cylindrical surface, wherein said plurality of pairs of electrodes are spaced around said metallic outer cylindrical surface;
at least one individual inductor connected to each pair of said first plurality of pairs of electrodes; and
at least one source of RF voltage connected across each pair of said plurality of pairs of electrodes.
2. The apparatus of claim 1 , wherein said first plurality of pairs of electrodes comprises four pairs of stationary curved electrodes, the azimuthal width of which is about 45° less the space between each electrode of each pair of said pairs.
3. The apparatus of claim 1 , further comprising:
a second plurality of pairs of electrodes spaced from said first plurality of pairs of electrodes, wherein each electrode of each pair of said second plurality of pairs is spaced from each other and from said metallic outer cylindrical surface, wherein said second plurality of pairs of electrodes are spaced around said metallic outer cylindrical surface;
at least one individual inductor connected to each pair of said second plurality of pairs of electrodes; and
means for providing RF voltage across each pair of said second plurality of pairs of electrodes.
4. A method, comprising:
providing an apparatus comprising:
a right cylindrical rotor configured for rotation about a longitudinal axis, wherein said rotor comprises a metallic outer cylindrical surface;
a passive magnetic bearing system configured to provide at least axial stabilization of said rotor as said rotor rotates;
a first plurality of pairs of electrodes, wherein each electrode of each pair of said pairs is spaced from each other and from said metallic outer cylindrical surface, wherein said plurality of pairs of electrodes are spaced around said metallic outer cylindrical surface;
at least one individual inductor connected to each pair of said pairs;
at least one source of RF voltage connected across each pair of said plurality of pairs of electrodes to form a plurality of series resonant circuits, each comprising a resonant frequency;
rotating said rotor; and
providing said RF voltage at a frequency that is higher than said resonant frequency.
5. The method of claim 4 , wherein said first plurality of pairs of electrodes comprises four pairs of stationary curved electrodes, the azimuthal width of which is about 45° less the space between each electrode of each pair of said pairs.
6. The method of claim 4 , further comprising:
a second plurality of pairs of electrodes spaced from said first plurality of pairs of electrodes, wherein each electrode of each pair of said second plurality of pairs is spaced from each other and from said metallic outer cylindrical surface, wherein said second plurality of pairs of electrodes are spaced around said metallic outer cylindrical surface;
at least one individual inductor connected to each pair of said second plurality of pairs of electrodes;
means for providing RF voltage across each pair of said second plurality of pairs of electrodes to form a plurality of series resonant circuits, each comprising a second resonant frequency; and
providing said RF voltage at a frequency that is higher than said second resonant frequency.
7. An apparatus, comprising:
four pairs of adjacent electrodes fixedly located relative to a longitudinal system axis, wherein said electrodes are arranged in a circle around said system axis, wherein said circle is perpendicular to said system axis, wherein said electrodes are curved with a radius of curvature having its origin at said system axis, wherein each electrode is spaced apart from all of its adjacent electrodes, wherein at least one of the electrodes of each pair is connected to an inductor, wherein said inductor is connected to one output node of at least one source of radio frequency energy, wherein the other electrode of each pair is connected to another output node of the source of radio frequency energy;
a cylindrical rotor having a longitudinal axis of rotation and a metallic cylindrical outer surface, wherein said rotor is movably located within said circle and is able to rotate about said longitudinal system axis, wherein when said rotor is rotating and said longitudinal axis of rotation overlaps and is collinear with said longitudinal system axis, a uniform gap will exist between each of said electrodes and said metallic cylindrical outer surface; and
means for stabilizing said cylindrical rotor along said longitudinal system axis.
8. The apparatus of claim 7 , wherein a capacitor is formed between each electrode and said metallic cylindrical outer surface such that four series circuits are formed, wherein each series circuit comprises a connection from one said output node to one said inductor to one said capacitor through said outer metallic surface to another one said capacitor to another said output node.
9. The apparatus of claim 8 , wherein each inductor comprises a value selected to produce a first resonant frequency within each said series circuit when said uniform gap exists.