PASSIVE MAGNETIC BEARING SYSTEM

• US 20120175985A1
• Filed: 01/06/2011
• Published: 07/12/2012
• Est. Priority Date: 01/06/2011
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Inventors: Post, Richard F.
• Granted Patent: US 8,823,233 B2
• Time in Patent Office: Days
• US Class Current: 310/90.5
• CPC Class Codes: F16C 2361/55 Flywheel systems
• CPC Class Codes: F16C 32/0436 with a conductor on one part movable with respect to a magnetic field, e.g. a body of copper on one part and a permanent magnet on the other part
• CPC Class Codes: F16C 32/0448 by using the electromagnet itself as sensor, e.g. sensorless magnetic bearings

Abstract

An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

Claims

1. An apparatus, comprising:

a rotor having an axis of rotation;

a first magnet fixedly attached to said rotor;

a second magnet fixedly attached to said rotor, wherein said first magnet is spaced apart from said second magnet;

a first Halbach array attached to said rotor;

a second Halbach array attached to said rotor, wherein said first Halbach array is spaced apart from said second Halbach array and wherein said first Halbach array and said second Halbach array are both located between said first magnet and said second magnet;

a first bearing magnet fixedly mounted external to said rotor and configured to attract said first magnet;

a second bearing magnet fixedly mounted external to said rotor and configured to repel said second magnet; and

a conductor array fixedly mounted external to said rotor and positioned between said first Halbach array and said second Halbach array, wherein said conductor array comprises windings.

2. The apparatus of claim 1, wherein said conductor array comprises a periodicity of one-half of the azimuthal wavelength of said first Halbach array and said second Halbach array.

3. The apparatus of claim 2, wherein said rotor is cylindrical and comprises an inner wall an outer wall, a first end and a second end.

4. The apparatus of claim 3, wherein said first magnet is fixedly attached to said inner wall, wherein said second Halbach array is fixedly attached to said inner wall.

5. The apparatus of claim 1, wherein the positive (attracting) stiffness for radial displacements of said first magnet with respect to said first bearing magnet is greater than the negative (repelling) stiffness of said second magnet with respect to said second bearing magnet.

6. The apparatus of claim 3, wherein said first magnet comprises a ring shape and is contiguously attached to said inner wall, wherein said second magnet comprises a ring shape and is contiguously attached to said inner wall, wherein said first Halbach array comprises a ring shape and is contiguously attached to said inner wall, wherein said second Halbach array comprises a ring shape and is contiguously attached to said inner wall of said cylinder and spaced apart from and parallel with said first Halbach array, wherein said first bearing magnet comprises a ring shape and wherein said second hearing magnet comprises a ring shape.

7. The apparatus of claim 1, wherein said windings comprises a plurality of windings, wherein equal gaps are located between all of the radially directed conductors.

8. The apparatus of claim 1, wherein a first end of said windings terminates at a first termination and a second end of said windings terminates at a second termination.

9. The apparatus of claim 8, further comprising a first lead connected to said first termination and a second lead connected to said second termination.

10. The apparatus of claim 9, wherein said first lead is electrically connected to a first side of a load and wherein said second lead is electrically connected to a second side of said load.

11. The apparatus of claim 9, further comprising means for producing a measured voltage by measuring the voltage appearing across said first lead to said second lead, said apparatus further comprising at least one switch that utilizes said measured voltage to switch between two different loading inductances.

12. The apparatus of claim 1, further comprising a bi-metallic support in rigid contact with said second hearing magnet, further comprising means for measuring temperature, wherein said bi-metallic support is activated by a change in said temperature.

24. The method of claim 12, further comprising a bi-metallic support in rigid contact with said second bearing magnet, further comprising means for measuring temperature, wherein said bi-metallic support is activated by a change in said temperature.

13. A method, comprising:

attaching a first magnet to a rotor having an axis of rotation;

attaching a second magnet to said rotor, wherein said first magnet is spaced apart from said second magnet;

attaching a first Halbach array to said rotor;

attaching a second Halbach array to said rotor, wherein said first Halbach array is spaced apart from said second Halbach array and wherein said first Halbach array and said second Halbach array are both located between said first magnet and said second magnet;

attaching a first bearing magnet to a mount located external to said rotor, wherein said first bearing magnet is configured to attract said first magnet;

attaching a second bearing magnet fixedly to a mount located external to said rotor and configured to repel said second magnet; and

attaching a conductor array to a mount located external to said rotor and positioned between said first Halbach array and said second Halbach array, wherein said conductor array comprises windings.

14. The method of claim 13, wherein said conductor array comprises a periodicity of one-half of the azimuthal wavelength of said first Halbach array and said second Halbach array.

15. The method of claim 14, wherein said rotor is cylindrical and comprises an inner wall an outer wall, a first end and a second end.

16. The method of claim 15, wherein said first magnet is fixedly attached to said inner wall, wherein said second Halbach array is fixedly attached to said inner wall.

17. The method of claim 13, wherein the positive (attracting) stiffness for radial displacements of said first magnet with respect to said first bearing magnet is greater than the negative (repelling) stiffness of said second magnet with respect to said second bearing magnet.

18. The method of claim 15, wherein said first magnet comprises a ring shape and is contiguously attached to said inner wall, wherein said second magnet comprises a ring shape and is contiguously attached to said inner wall, wherein said first Halbach array comprises a ring shape and is contiguously attached to said inner wall, wherein said second Halbach array comprises a ring shape and is contiguously attached to said inner wall of said cylinder and spaced apart from and parallel with said first Halbach array, wherein said first bearing magnet comprises a ring shape and wherein said second bearing magnet comprises a ring shape.

19. The method of claim 13, wherein said windings comprises a plurality of windings, wherein equal gaps are located between all of the radially directed conductors.

20. The method of claim 13, wherein a first end of said windings terminates at a first termination and a second end of said windings terminates at a second termination.

21. The method of claim 20, further comprising a first lead connected to said first termination and a second lead connected to said second termination.

22. The method of claim 21, wherein said first lead is electrically connected to a first side of a load and wherein said second lead is electrically connected to a second side of said load.

23. The method of claim 21, further comprising means for producing a measured voltage by measuring the voltage appearing across said first lead to said second lead, said apparatus further comprising at least one switch that utilizes said measured voltage to switch between two different loading inductances.

25. An apparatus comprising:

a rotor having an axis of rotation;

a first Halbach array connected to said rotor;

a conductor array comprising windings, wherein said conductor array is fixedly mounted external to said rotor, wherein said windings consist essentially of wire, wherein said conductor array comprises a periodicity of one-half of the azimuthal wavelength of said first Halbach array.

26. The apparatus of claim 25, further comprising:

a first magnet fixedly attached to said rotor;

a second magnet fixedly attached to said rotor, wherein said first magnet is spaced apart from said second magnet;

a second Halbach array attached to said rotor, wherein said first Halbach array is spaced apart from said second. Halbach array and wherein said first Halbach array and said second Halbach array are both located between said first magnet and said second magnet;

a first bearing magnet fixedly mounted external to said rotor and configured to attract said first magnet;

a second bearing magnet fixedly mounted external to said rotor and configured to repel said second magnet; and

a conductor array fixedly mounted external to said rotor and positioned between said first Halbach array and said second Halbach array, wherein said conductor array comprises windings.

27. The apparatus of claim 25, wherein said first Halbach array comprises a cylindrical shape, wherein said windings comprises a series-connected group of windings having a width of one half-wavelength of said Halbach array and wherein said windings have crossover connections configured to cancel the voltage generated by the windings when the axis of said windings coincides with the axis of rotation of the Halbach array.

28. The apparatus of claim 27, wherein said windings comprise a first end and a second end, wherein said first end and said second end are electrically connected to opposite ends of an inductance.

29. The apparatus of claim 28, wherein said inductance comprises a value selected to limit the displacement-dependent current in the winding to achieve the positive stiffness required to achieve stabilization of the passive bearing system.

30. The apparatus of claim 25, wherein said windings comprise four separate quadrant sections, wherein opposite-side quadrants are connected in opposing series and the two remaining winding ends of said opposite-side quadrants are connected to an inductance with a first value, wherein the remaining two quadrants are connected in opposing series and are connected to an inductance with a second value not equal to said first value to produce an asymmetric stiffness for suppressing rotor-dynamic whirl instabilities.

31. The apparatus of claim 26, wherein the positive (attracting) stiffness between said first magnet with respect to said first bearing magnet is greater than the negative (repelling) stiffness of said second magnet with respect to said second bearing magnet.

32. The apparatus of claim 25, wherein said windings comprises a plurality of windings, wherein equal gaps are located between all of the radially directed conductors.

33. The apparatus of claim 25, wherein a first end of said windings terminates at a first termination and a second end of said windings terminates at a second termination, further comprising a first lead connected to said first termination and a second lead connected to said second termination, wherein said first lead is electrically connected to a first side of a load and wherein said second lead is electrically connected to a second side of said load, further comprising means for producing a measured voltage by measuring the voltage appearing across said first lead to said second lead, said apparatus further comprising at least one switch that utilizes said measured voltage to switch between two different loading inductances.

34. The apparatus of claim 25, further comprising a bi-metallic support in rigid contact with said second bearing magnet, further comprising means for measuring temperature, wherein said bi-metallic support is activated by a change in said temperature.