Systems and methods for constructing permanent magnet motors having increased power density

Patent metadata

Field	Value
Publication number	US-10680476-B2
Application number	US-201815879544-A
Country	US
Kind code	B2
Filing date	Jan 25, 2018
Priority date	Jan 25, 2018
Publication date	Jun 9, 2020
Grant date	Jun 9, 2020

Abstract

Systems and methods for constructing permanent magnet electric motors in which rotors have magnetically permeable end rings that are active for torque production. In one embodiment, a rotor section has a set of flat, generally annular laminations stacked on an inner rotor sleeve, with a pair of end rings positioned at opposing ends of the lamination stack to secure the stack. One or both of the end rings is made of a magnetically permeable and highly resistive material such as a soft magnetic composite, so that the end ring(s) actively produce torque during operation of the motor without significant increase in core loss at end rings. A set of permanent magnets are installed in or on the rotor core formed by the laminations. These magnets or other magnets may be positioned to axially overlap with the end rings and aid active torque production by the end rings.

First claim

What is claimed is:

1. An apparatus comprising:
an end ring for retaining adapted to retain a rotor lamination stack, wherein the end ring is generally annular, wherein the end ring is made of a magnetically permeable material with high resistivity and actively produces torque in the presence of a stator magnetic field, wherein the end ring has a relative magnetic permeability of at least 500 and a resistivity of greater than 1.43×10−7 Ohm-meter;
wherein the end ring is configured to be mounted in a rotor section, such that the end ring secures a plurality of rotor laminations in a stack that forms a rotor core; and

further comprising a plurality of magnets that are mounted on the end ring.

2. The apparatus of claim 1 , wherein the magnetically permeable material of the end ring comprises a soft magnetic composite, wherein the soft magnetic composite comprises particles of a magnetically permeable material which are bonded with a coating of an organic material to produce high electrical resistivity.

3. The apparatus of claim 1 , wherein the end ring has an inward-facing surface that is threaded, wherein the threaded inward-facing surface is capable of being threaded onto a rotor inner sleeve, thereby securing the end ring to the rotor inner sleeve.

4. A system comprising:
a downhole motor;
wherein the motor includes
a stator having a bore therethrough, and
a rotor mounted on a shaft, wherein the rotor and shaft are rotatably positioned within the stator bore;
wherein the stator has a plurality of stator windings and wherein the stator windings are energized to produce magnetic fields that drive the rotor to rotate within the stator bore;
wherein the rotor comprises one or more rotor sections, and wherein each rotor section comprises
a plurality of flat, generally annular laminations, wherein each of the laminations is magnetically permeable, and wherein the laminations are stacked to form a magnetically permeable rotor core,
a pair of end rings positioned at opposing ends of the stacked laminations, wherein the end rings secure the stacked laminations on the rotor section, wherein at least one of the end rings is made of a magnetically permeable material with high resistivity and actively produces torque during operation of the motor, wherein the at least one of the end rings has a relative magnetic permeability of at least 500, and
a plurality of permanent magnets installed in the rotor core and end rings;
wherein the magnetically permeable material has a resistivity of greater than 1.43×10−7 Ohm-meter.

5. The system of claim 4 , wherein the magnetically permeable material has a resistivity of between 1×10−4 Ohm-meter and 1×10−3 Ohm-meter.

6. A system comprising:
a downhole motor;
wherein the motor includes
a stator having a bore therethrough, and
a rotor mounted on a shaft, wherein the rotor and shaft are rotatably positioned within the stator bore;
wherein the stator has a plurality of stator windings and wherein the stator windings are energized to produce magnetic fields that drive the rotor to rotate within the stator bore;
wherein the rotor comprises one or more rotor sections, and wherein each rotor section comprises
a plurality of flat, generally annular laminations, wherein each of the laminations is magnetically permeable, and wherein the laminations are stacked to form a magnetically permeable rotor core,
a pair of end rings positioned at opposing ends of the stacked laminations, wherein the end rings secure the stacked laminations on the rotor section, wherein at least one of the end rings is made of a magnetically permeable material with high resistivity and actively produces torque during operation of the motor, wherein the at least one of the end rings has a relative magnetic permeability of at least 500, and
a plurality of permanent magnets installed in the rotor core and end rings;
wherein the magnetically permeable material and highly resistive comprises a soft magnetic composite; and
wherein the soft magnetic composite comprises particles of a magnetically permeable material which are bonded with a coating of an organic material to produce high electrical resistivity.

7. The system of claim 6 , wherein the coated particles are annealed and bonded into a solid material.

8. The system of claim 6 , wherein the particles comprise either a metal or a metal alloy.

9. The system of claim 6 , wherein the plurality of permanent magnets include a set of magnets that are mounted on the at least one of the end rings.

10. The system of claim 9 , wherein the plurality of permanent magnets include; a first set of magnets that are mounted on the rotor core and axially overlap only the rotor core; and a second set of magnets that are mounted on the at least one of the end rings and axially overlap only the at least one of the end rings.

11. The system of claim 6 , wherein one or more of the plurality of permanent magnets axially overlap both the rotor core and the at least one of the end rings.

12. The system of claim 6 , further comprising a tubular inner sleeve on which the stacked plurality of laminations are mounted, wherein an outward-facing surface of the inner sleeve is threaded at each end, wherein each of the end rings is threaded on an inward-facing surface, and wherein each of the end rings is secured to the inner sleeve with the threads of the
end ring engaging the threads on a corresponding one of the ends of the inner sleeve.

13. The system of claim 6 , further comprising a plurality of threaded rods that extend through the stacked plurality of laminations, wherein a first end of each threaded rod is secured to a first one of the end rings and a second end of each threaded rod is secured to a second one of the end rings, thereby securing the stacked plurality of laminations together.

14. The system of claim 4 , wherein the magnetically permeable material and highly resistive comprises a soft magnetic composite.

15. The system of claim 4 , wherein the plurality of permanent magnets include a set of magnets that are mounted on the at least one of the end rings.

16. The system of claim 15 , wherein the plurality of permanent magnets include; a first set of magnets that are mounted on the rotor core and axially overlap only the rotor core; and a second set of magnets that are mounted on the at least one of the end rings and axially overlap only the at least one of the end rings.

17. The system of claim 4 , wherein one or more of the plurality of permanent magnets axially overlap both the rotor core and the at least one of the end rings.

18. The system of claim 4 , further comprising a tubular inner sleeve on which the stacked plurality of laminations are mounted, wherein an outward-facing surface of the inner sleeve is threaded at each end, wherein each of the end rings is threaded on an inward-facing surface, and wherein each of the end rings is secured to the inner sleeve with the threads of the end ring engaging the threads on a corresponding one of the ends of the inner sleeve.

19. The system of claim 4 , further comprising a plurality of threaded rods that extend through the stacked plurality of laminations, wherein a first end of each threaded rod is secured to a first one of the end rings and a second end of each threaded rod is secured to a second one of the end rings, thereby securing the stacked plurality of laminations together.

Assignees

• Li Yong
• Clingman James C
• Baker Hughes A Ge Co Llc

Inventors

• Li Yong
• Clingman James C

Classifications

• H02K49/06

  of the synchronous type {(H02K49/10 takes precedence)} · CPC title

• E21B4/00

  Drives for drilling, used in the borehole · CPC title

• H02K1/278 Primary

  Surface mounted magnets; Inset magnets · CPC title

• H02K15/03

  having permanent magnets · CPC title

• H02K21/16

  having annular armature cores with salient poles (with homopolar co-operation H02K21/20) · CPC title