Magnetic bearings for flywheel rotor levitation with radial stabilization

A flywheel system, comprising:

• a fixture including a bottom support;
• a rotor having a gravitational load and configured to rotate above the bottom support about a rotation axis;
• and
• a bottom magnetic levitation bearing including:
• a ring of first permanent magnets mechanically coupled with a bottom end of the rotor, the ring of first permanent magnets having a first height and a first diameter, and the first permanent magnets having an upper first pole, a lower second pole and a magnetic field parallel to the rotation axis,
• a ring of second permanent magnets mechanically coupled to the bottom support, the ring of second permanent magnets having a second height lower than the first height and a second diameter approximately equal to the first diameter, and the second permanent magnets having a upper second pole repelling the lower second pole of the first permanent magnets to magnetically support at least a portion of the gravitational load above the bottom support,
• a ring of third permanent magnets mechanically coupled with the bottom end of the rotor, the ring of third permanent magnets having a third height greater than the first height and a third diameter greater than the first diameter, and the third permanent magnets having an inner second pole, an outer first pole and a magnetic field orthogonal to the rotation axis, and
• a ring of fourth permanent magnets mechanically coupled to the bottom support, the ring of fourth permanent magnets having a fourth height greater than the first height and less than the third height, and a fourth diameter greater than the third diameter, and the fourth permanent magnets having an inner first pole repelling the outer first pole of the third permanent magnets to at least reduce radial decentering of the rotor relative to the fixture;
• wherein the upper first pole of the first permanent magnets is closer to the inner second pole of the third permanent magnets than to the outer first pole of the third permanent magnets, and the inner second pole of the third permanent magnets is closer to the upper first pole of first permanent magnets than to the lower second pole of first permanent magnets;
• the flywheel system further comprising:
• a generator including:
• a plurality of first generator permanent magnets mechanically coupled with the rotor, and
• a generator stator mechanically coupled to the fixture and configured to cooperate with the first generator permanent magnets to convert between rotational energy of the rotor and electric current in windings of the generator stator;
• an active magnetic bearing including:
• a plurality of magnetizable elements mechanically coupled with the rotor, and
• a plurality of electromagnets mechanically coupled to the fixture and configured to magnetically couple with the plurality of magnetizable elements to actively stabilize the rotor relative to the fixture;
• and
• a passive magnetic backup bearing including:
• a plurality of first passive backup bearing permanent magnets mechanically coupled with the rotor, and
• a plurality of second passive backup bearing permanent magnets mechanically coupled to the fixture and configured to magnetically couple with the first passive backup bearing permanent magnets to provide backup stabilization of the rotor relative to the fixture if the active magnetic bearing fails.