Sectoral core for magnetic bearing

• US 5,095,237 A
• Filed: 01/10/1991
• Issued: 03/10/1992
• Est. Priority Date: 03/20/1990
• Status: Expired due to Fees

• Current Assignee: NOVA Corp. of Alberta (TC Energy Corp.)
• Original Assignee: NOVA Corp. of Alberta (TC Energy Corp.)
• Inventors: Oleksuk, Cal, Brailean, Gordon, Bardas, Theodor, Kulle, Vaclav, Harris, Timothy A.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): REBSCH, DONALD
• Application Number:
  US07/639,349
• Time in Patent Office: 425 Days
• Field of Search: 310/90.5, 310/254, 310/67 R, 310/185, 310/186, 310/188, 310/208, 310/216, 310/217
• US Class Current: 310/90.5
• CPC Class Codes: F16C 32/0459 Details of the magnetic circuit
• CPC Class Codes: F16C 32/0465 with permanent magnets provided in the magnetic circuit of the electromagnets
• CPC Class Codes: F16C 32/048 with active support of two degrees of freedom, e.g. radial magnetic bearings
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

A rotary electrical machine comprises a rotor assembly and a stator assembly separated by an air gap. The stator is formed from discrete generally pie-shaped pole pieces having a progressively increasing radial slot to accommodate winding of the coil. The pole pieces are preferably wound from a grain oriented ferromagnetic tape to improve the permeability of the pole and its saturation level. Groups of poles may be separated into sectors. In an alternative embodiment, at least some of the pole pieces are formed from both a permanent magnet and ferromagnetic tape to provide a constant bias between the rotor and stator assemblies.

Claims

1. A radial magnetic bearing comprising a rotor assembly secured to and rotating with rotating components of said bearing and a stator assembly secured to stationary components of said bearing, said assemblies having opposed peripheral surfaces separated by an air gap with said stator assembly comprising a plurality of pole pieces arranged in seriatim about the axis of rotation of said machine, each pole piece being formed as a discrete unit and having a pair of circumferentially spaced limbs, each of which terminates in a pole at the respective peripheral surface, said limbs being separated by a radial slot extending from an axially extending discontinuity in the peripheral surface that separates the poles and having a portion of greater circumferential width than said discontinuity, said pole pieces being segregated into at least two sectors, each containing an integral number of pole pieces, each sector having means associated therewith for generating and adjusting the magnetic flux in the pole pieces of its respective sector independently of the adjacent sectors and thereby adjusting the force exerted by the respective sector on said rotor assembly.

2. A magnetic bearing according to claim 1 wherein each of said generation and adjustment means includes a coil means and current supply means, said coil means encompassing at least a portion of each pole piece in the respective sector.

3. A bearing according to claim 2 wherein said slot progressively increases in width in a radial direction away from said peripheral surface.

4. A bearing according to claim 3 wherein said limbs converge toward said peripheral surface.

5. A bearing according to claim 4 wherein said pole pieces are pie-shaped and limbs of adjacent pole pieces abut.

6. A bearing according to claim 5 wherein said coil means includes a coil encompassing abutting limbs of adjacent pole pieces in the respective sector.

7. A bearing according to claim 6 wherein each sector is delimited by a pole piece having a limb abutting a limb of a pole piece of an adjacent sector, said coil encompassing the other limb of said pole piece.

8. A bearing according to claim 1 wherein at least a portion of at least one of said pole pieces is formed from laminations extending between said poles and abutting faces of said laminations lie in planes generally parallel to the axis of rotation.

9. A bearing according to claim 8 wherein said laminations are lengths of ferromagnetic tape with an oriented grain structure.

10. A bearing according to claim 9 wherein each of said pole pieces are pie-shaped and said limbs are interconnected by a circumferentially extending connecting portion.

11. A bearing according to claim 10 wherein said limbs and connecting portion have a substantially uniform cross-section.

12. A bearing according to claim 11 wherein limbs of adjacent pole pieces in each sector abut.

13. A bearing according to claim 12 wherein said coil means includes a coil encompassing abutting pairs of limbs of adjacent pole pieces in the respective sector.

14. A bearing according to claim 9 wherein at least one of said pole pieces is formed entirely from said laminations.

15. A bearing according to claim 1 wherein at least one of said pole pieces is formed in part from a permanently magnetized material.

16. A bearing according to claim 8 wherein selected ones of said pole pieces are formed at least in part from material exhibiting enhanced magnetic characteristics relative to the other of said pole pieces.

17. A rotary electrical machine comprising a rotor assembly secured to and rotating with rotating components of said machine and a stator assembly secured to stationary components of said machine, said assemblies having opposed peripheral surfaces separated by an air gap, said stator assembly comprising a plurality of pole pieces arranged in seriatim about the axis of rotation of said machine, each pole piece having a pair of spaced limbs each of which terminates in a pole at the respective peripheral surface, at least one of said pole pieces being formed at least in part from laminations extending between said poles with abutting faces of said laminations being in planes generally parallel to the axis of rotation of said rotating assembly, said pole pieces being pie-shaped with a correspondingly-shaped radial slot between said limbs, said slot extending to said peripheral surface to define a discontinuity therein to separate said poles, at least one pair of abutting limbs being encompassed by a coil formed from multiple turns of a conductor arranged in layers, said turns being located in the radial slots of each of said pair of pole pieces and said layers having a cumulative thickness greater than the discontinuity between said limbs.