FAULT-TOLERANT SYNCHRONOUS PERMANENT MAGNET MACHINE

• US 20080143207A1
• Filed: 12/19/2006
• Published: 06/19/2008
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: GE Global Research (General Electric Co. (Italy))
• Inventors: Shah, Manoj Ramprasad, EL-Refaie, Ayman Mohamed Fawzi
• Granted Patent: US 7,791,237 B2
• Time in Patent Office: Days
• US Class Current: 310/156.08
• CPC Class Codes: H02K 1/146 consisting of a generally annular yoke with salient poles
• CPC Class Codes: H02K 1/278 Surface mounted magnets; Inset magnets
• CPC Class Codes: H02K 11/012 Shields associated with rotating parts, e.g. rotor cores or rotary shafts
• CPC Class Codes: H02K 21/16 having annular armature cores with salient poles with homopolar co-operation H02K21/20

Abstract

A fault tolerant synchronous permanent magnet machine is disclosed that reduces rotor losses by limiting eddy-current losses in the retaining sleeve. The machine limits eddy-current loss by any one or combination of axially segmenting the retaining sleeve, providing a highly electrically conductive non-magnetic shield to the retaining sleeve, and by configuring stator teeth width, stator teeth tip width, and slot distribution of the stator.

Claims

1. A fault-tolerant synchronous permanent magnet machine, comprising:

a stator having an axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said teeth having two side faces terminating at a distal head, each of said distal heads having a head end that provides a plurality of head ends spaced around said interior cylindrical surface;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core facing the interior cylindrical surface of the stator;

a retaining sleeve having an axial length and disposed between the permanent magnets and the interior cylindrical surface of the stator,

wherein the retaining ring defines a gap between the retaining sleeve and the interior cylindrical surface of the stator; and

wherein the retaining sleeve is axially segmented.

2. A fault-tolerant synchronous permanent magnet machine, comprising:

a stator having an axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said distal heads having a head end that provides a plurality of head ends spaced around said interior cylindrical surface;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core facing the interior cylindrical surface of the stator;

a retaining sleeve having an axial length and an outer radial surface and disposed between the permanent magnets and the interior cylindrical surface of the stator;

a shield disposed upon the outer radial surface of the retaining sleeve; and

a gap between the shield and the interior cylindrical surface of the stator.

3. The machine of claim 2, wherein the retaining sleeve is axially segmented.

4. The machine of claim 2, wherein the shield comprises an electrically conductive, non-magnetic material.

5. The machine of claim 3, wherein the shield comprises an electrically conductive, non-magnetic material.

6. The machine of claim 4, wherein the shield comprises copper.

7. The machine of claim 5, wherein the shield comprises copper.

8. A fault-tolerant synchronous permanent magnet machine, comprising:

a stator having an axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said distal heads have a head end that provides a plurality of head ends that circumferentially span said interior cylindrical surface and spaced to create slot openings to the slots;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core facing the interior cylindrical surface of the stator;

a retaining sleeve having an axial length and an outer radial surface and disposed between the permanent magnets and the interior cylindrical surface of the stator,

wherein the retaining sleeve defines a gap between the retaining sleeve and the interior cylindrical surface of the stator, and

wherein the slots between the plurality of teeth of the stator are irregularly circumferentially spaced.

9. The machine of claim 8, wherein the slots of the stator are irregularly spaced because of a variable thickness of the stator teeth.

10. The machine of claim 8, wherein the slot openings are irregularly circumferentially spaced.

11. The machine of claim 9, wherein the slot openings are irregularly circumferentially spaced.

12. The machine of claim 8, wherein the retaining sleeve is axially segmented.

13. The machine of claim 8, wherein a shield is disposed on the outer radial surface of the retaining sleeve.

14. The machine of claim 13, wherein a shield is disposed on the outer radial surface of the retaining sleeve.

15. The machine of claim 15, wherein the shield comprises copper.

16. A method of reducing eddy-current losses in a permanent magnet machine, comprising:

providing an permanent magnet machine comprising;

a stator having and axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said teeth having two side faces terminating at a distal head, each of said distal heads having a head end that provides a plurality of head ends spaced around said interior cylindrical surface;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core facing the interior cylindrical surface of the stator; and

a retaining sleeve having an axial length and an outer radial surface and disposed between the permanent magnets and the interior cylindrical surface of the stator;

wherein the retaining sleeve defines a gap between the retaining sleeve and the interior cylindrical surface of the stator; and

axially segmenting the retaining sleeve.

17. The method of claim 16, further comprising:

providing a copper shield upon the outer radial surface of the retaining sleeve.

18. A method of reducing eddy-current losses in a permanent magnet machine, comprising:

providing an permanent magnet machine comprising;

a stator having an axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said teeth having two side faces terminating at a distal head, each of said distal heads having a head end that provides a plurality of head ends spaced around said interior cylindrical surface;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core f facing the interior cylindrical surface of the stator; and

a retaining sleeve having an axial length and an outer radial surface and disposed between the permanent magnets and the interior cylindrical surface of the stator;

wherein the retaining sleeve defines a gap between the retaining sleeve and the interior cylindrical surface of the stator; and

providing a copper shield upon the outer radial surface of the retaining sleeve.

19. A method of reducing eddy-current losses in a permanent magnet machine, comprising:

providing an permanent magnet machine comprising;

a stator having an axial length and a plurality of teeth spaced to define slots therebetween and circumferentially aligned to define an interior cylindrical surface for the stator, each of said teeth having two side faces terminating at a distal head, each of said distal heads have a head end that provides a plurality of head ends that circumferentially span said interior cylindrical surface and spaced to create slot openings to the slots;

a rotor having an axial length and comprising a rotor core fixed to a rotatable shaft for rotation therewith and a plurality of permanent magnets mounted on said rotor core at a plurality of locations circumferentially spaced around said rotor core facing the interior cylindrical surface of the stator; and

a retaining sleeve having an axial length and an outer radial surface and disposed between the permanent magnets and the interior cylindrical surface of the stator;

wherein the retaining sleeve defines a gap between the retaining sleeve and the interior cylindrical surface of the stator; and

forming the slots between the plurality of teeth of the stator such that that slots are irregularly circumferentially spaced.

20. The method of claim 19, further comprising:

forming the head ends to irregularly circumferentially space the slot openings.