Liquid cooled permanent magnet rotor

• US 20100164310A1
• Filed: 12/30/2008
• Published: 07/01/2010
• Est. Priority Date: 12/30/2008
• Status: Active Grant

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Cruce, Perry G., Baumann, Jonathan M., Fee, David M., Dames, Matthew W.
• Granted Patent: US 8,022,582 B2
• Time in Patent Office: Days
• US Class Current: 310/54
• CPC Class Codes: H02K 1/278 Surface mounted magnets; Inset magnets
• CPC Class Codes: H02K 1/32 with channels or ducts for flow of cooling medium
• CPC Class Codes: H02K 9/197 in which the rotor or stator space is fluid-tight, e.g. to provide for different cooling media for rotor and stator
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine
• CPC Class Codes: Y10T 29/49012 Rotor

Abstract

A permanent magnet rotor for an electrical generator includes a rotor shaft and a rotor core mounted coaxially upon the rotor shaft. The rotor core defines a plurality of longitudinal core passages which include a segment of a rotor cooling circuit, and further includes a permanent magnet outer core component mounted on an inner core component and including a plurality of permanent magnets. A cooling liquid containment mechanism for the permanent magnet rotor includes a first liquid containment cover coupled to the inner core component and a second liquid containment cover coupled to the inner core component. The liquid containment covers are configured to contain cooling liquid passed from an inlet segment of the rotor cooling circuit defined by the rotor shaft into the plurality of longitudinal core passages, and thenceforth into an outlet segment of the rotor cooling circuit also defined by the rotor shaft. The liquid containment covers are mounted on the inner core component at locations radially inward of a cylindrical outer surface thereof.

Claims

1. A permanent magnet rotor for an electrical generator comprising:

a rotor shaft defining a longitudinal shaft axis, a first longitudinal shaft passage which includes an inlet segment of a rotor cooling circuit and a second longitudinal shaft passage which includes an outlet segment of the rotor cooling circuit;

a rotor core including an inner core component coaxial with the rotor shaft and defining a plurality of longitudinal core passages which include a third segment of the rotor cooling circuit, the rotor core further including a first axial inner core end, a second axial inner core end, a cylindrical outer surface and a permanent magnet outer core component having a plurality of permanent magnets mounted circumferentially about the cylindrical outer surface; and

a cooling liquid containment mechanism configured to contain a cooling liquid passed through the rotor cooling circuit, including a first liquid containment cover sealingly coupled to the inner core component at a first mounting location on the first axial inner core end and a second liquid containment cover sealingly coupled to the inner core component at a second mounting location on the second axial inner core end, each of the first mounting location and the second mounting location being radially inward of the cylindrical outer surface of the inner core component.

2. The permanent magnet rotor of claim 1 wherein the first liquid containment cover and the second liquid containment cover each include an axially outward side and an axially inward side, the axially inward side of the first liquid containment cover including a wetted wall of a first cavity fluidly connecting the inlet segment with the third segment and the axially inward side of the second liquid containment cover including a wetted wall of a second cavity fluidly connecting the third segment with the outlet segment.

3. The permanent magnet rotor of claim 2 wherein the plurality of longitudinal core passages are disposed radially symmetrically about the longitudinal shaft axis, the permanent magnet rotor defining a solid-to-solid heat rejection path extending from the plurality of permanent magnets into the inner core component and a solid-to-fluid heat rejection path extending from the inner core component into the plurality of longitudinal core passages.

4. The permanent magnet rotor of claim 2 further comprising:

a first radial land area located on the first axial inner core end and a second radial land area located on the second axial inner core end;

a first mounting interface including a first set of bolt holes defined by the inner core component for boltingly mounting the first liquid containment cover and extending axially inward from the first radial land area; and

a second mounting interface including a second set of bolt holes defined by the inner core component for boltingly mounting the second liquid containment cover and extending axially inward from the second radial land area.

5. The permanent magnet rotor of claim 4 wherein each of the first set of bolt holes and the second set of bolt holes includes at least one bolt hole arranged radially asymmetrically about the longitudinal axis with respect to the other bolt holes of the corresponding set to key the corresponding liquid containment cover to the rotor core at a single radial orientation about the longitudinal shaft axis.

6. The permanent magnet rotor of claim 4 further comprising:

a first bolted joint connecting the first liquid containment cover to the first radial land area and including a first set of bolts mated with the first set of bolt holes and a first O-ring seal positioned between the first radial land area and the first liquid containment cover; and

a second bolted joint connecting the second liquid containment cover to the second radial land area and including a second set of bolts mated with the second set of bolt holes and a second O-ring seal positioned between the second radial land area and the second liquid containment cover.

7. The permanent magnet rotor of claim 4 further comprising a rotor balancing mechanism having a first set of balancing mass mounts positioned on the first liquid containment cover and a second set of balancing mass mounts positioned on the second liquid containment cover, the first and second sets of balancing mass mounts being configured for mounting balancing mass thereon to change a mass distribution of the permanent magnet rotor.

8. The permanent magnet rotor of claim 7 wherein the first set of balancing mass mounts and the second set of balancing mass mounts each include a plurality of mass mounting studs extending in opposed first and second axially outward directions, respectively, the permanent magnet rotor further including a first set of mass elements mounted on the first set of balancing mass mounts and a second set of mass elements mounted on the second set of balancing mass mounts, and each of the first set of mass elements and the second set of mass elements being arranged asymmetrically about the longitudinal shaft axis.

9. The permanent magnet rotor of claim 4 wherein the first liquid containment cover and the second liquid containment cover each include a uniform cylindrical inner peripheral edge surface mated with the rotor shaft, an outer peripheral edge surface, and a sloping profile between the corresponding inner peripheral edge surface and outer peripheral edge surface.

10. The permanent magnet rotor of claim 9 wherein each of the first liquid containment cover and the second liquid containment cover includes a first radial region adjoining the corresponding inner peripheral edge surface, a second radial region adjoining the corresponding outer peripheral edge surface and a middle radial region extending between the corresponding first radial region and second radial region which includes the sloping profile, and wherein each of the first radial region and the middle radial region includes a uniform material thickness between the axially outward side and the axially inward side of the corresponding liquid containment cover.

11. A method of operating an electrical generator rotor having a rotor shaft with a longitudinal axis and a permanent magnet rotor core mounted to rotate within a stator and being positioned coaxially on the rotor shaft, the method comprising:

inducing a temperature increase in a plurality of permanent magnets of an outer core component of the permanent magnet rotor core at least in part by rotating the permanent magnet rotor core within the stator;

dissipating heat from the permanent magnet rotor core at least in part by passing a cooling liquid between a shaft passage extending longitudinally in the rotor shaft and a plurality of core cooling passages extending longitudinally in an inner core component of the permanent magnet rotor core; and

containing the cooling liquid via a first liquid containment cover sealingly coupled to a first axial inner core end of the inner core component and a second liquid containment cover sealingly coupled to a second axial inner core end of the inner core component.

12. The method of claim 11 further comprising retaining the first liquid containment cover and the second liquid containment cover on the inner core component via a first bolted joint and a second bolted joint, respectively, each being positioned radially inward of a cylindrical outer surface of the inner core component.

13. The method of claim 12 wherein containing the cooling liquid further includes containing cooling liquid passing from a first longitudinal shaft passage to the plurality of core passages via a first cavity defined in part by an axially inward side of the first liquid containment cover and containing cooling liquid passing from the plurality of core cooling passages to a second longitudinal shaft passage via a second cavity defined in part by an axially inward side of the second liquid containment cover.

14. A method of assembling a permanent magnet rotor for an electrical generator comprising:

mounting an inner core component having a plurality of longitudinally extending core passages coaxially on a rotor shaft defining a first longitudinally extending shaft passage and a second longitudinally extending shaft passage;

positioning a permanent magnet outer core component circumferentially about the inner core component;

fluidly connecting a first rotor cooling circuit segment which includes the first longitudinally extending shaft passage with a second rotor cooling circuit segment which includes the plurality of longitudinally extending core passages via sealingly coupling a first liquid containment cover to a first axial end of the inner core component at a first mounting location which is radially inward of a cylindrical outer surface of the inner core component; and

fluidly connecting the second rotor cooling circuit segment with a third rotor cooling circuit segment which includes the second longitudinally extending shaft passage via sealingly coupling a second liquid containment cover to a second axial end of the inner core component at a second mounting location which is radially inward of the cylindrical outer surface of inner core component.

15. The method of claim 14 further comprising:

establishing a solid-to-solid heat rejection path extending radially inward from a plurality of permanent magnets of the permanent magnet outer core component into the inner core component by way of positioning the permanent magnet outer core component circumferentially about the inner core component; and

establishing a solid-to-fluid heat rejection path extending from the inner core component into the second rotor cooling circuit segment by way of fluidly connecting the first rotor cooling circuit segment with the second rotor cooling circuit segment and fluidly connecting the second rotor cooling circuit segment with the third rotor cooling circuit segment.

16. A permanent magnet rotor for an electrical generator comprising:

a rotor shaft defining a longitudinal shaft axis, a first longitudinal shaft passage and a second longitudinal shaft passage;

a permanent magnet rotor core mounted coaxially on the rotor shaft and defining a plurality of longitudinal core passages;

a rotor cooling circuit having a first segment which includes the first longitudinal shaft passage, a second segment which includes the plurality of longitudinal core passages and a third segment which includes the second longitudinal shaft passage; and

a first liquid containment cover sealingly coupled to the permanent magnet rotor core and including an axially outward side and an axially inward side, the axially inward side including a first profiled wetted surface of the rotor cooling circuit which is configured to deflect a cooling liquid passing out of the first segment into the second segment of the rotor cooling circuit; and

a second liquid containment cover sealingly coupled to the permanent magnet rotor core and also including an axially outward side and an axially inward side, the axially inward side of the second liquid containment cover including a second profiled wetted surface of the rotor cooling circuit which is configured to deflect cooling liquid passing out of the second segment into the third segment of the rotor cooling circuit.

17. The permanent magnet rotor of claim 16 wherein the permanent magnet rotor includes an outer core component and an inner core component having a first axial end, a second axial end and a cylindrical outer surface;

the first liquid containment cover is mounted to the first axial end at a first mounting location which is radially inward of the cylindrical outer surface; and

the second liquid containment cover is mounted to the second axial end at a second mounting location which is radially inward of the cylindrical outer surface.

18. The permanent magnet rotor of claim 17 wherein the outer core component includes a plurality of permanent magnets mounted on the cylindrical outer surface of the inner core component.

19. The permanent magnet rotor of claim 18 wherein the first liquid containment cover and the second liquid containment cover each include a uniform cylindrical inner peripheral edge surface mated with the rotor shaft, an outer peripheral edge surface and a sloping profile between the corresponding inner peripheral edge surface and outer peripheral edge surface.