Spoke permanent magnet machine with reduced torque ripple and method of manufacturing thereof

Patent metadata

Field	Value
Publication number	US-9287742-B2
Application number	US-201313958693-A
Country	US
Kind code	B2
Filing date	Aug 5, 2013
Priority date	Aug 5, 2013
Publication date	Mar 15, 2016
Grant date	Mar 15, 2016

Abstract

An internal permanent magnet machine includes a rotor assembly having a shaft comprising a plurality of protrusions extending radially outward from a main shaft body and being formed circumferentially about the main shaft body and along an axial length of the main shaft body. A plurality of stacks of laminations are arranged circumferentially about the shaft to receive the plurality of protrusions therein, with each stack of laminations including a plurality of lamination groups arranged axially along a length of the shaft and with permanent magnets being disposed between the stacks of laminations. Each of the laminations includes a shaft protrusion cut formed therein to receive a respective shaft protrusion and, for each of the stacks of laminations, the shaft protrusion cuts formed in the laminations of a respective lamination group are angularly offset from the shaft protrusion cuts formed in the laminations in an adjacent lamination group.

First claim

What is claimed is:

1. An internal permanent magnet machine comprising:
a stator assembly comprising:
a stator core including a plurality of stator teeth; and
stator windings wound about the plurality of stator teeth to generate a stator magnetic field when excited with alternating currents

a rotor assembly disposed within a cavity defined by the stator assembly and configured to rotate relative to the stator assembly, wherein the rotor assembly comprises:
a shaft comprising a plurality of protrusions extending radially outward from a main shaft body, the plurality of protrusions being formed circumferentially about the main shaft body and along an axial length of the main shaft body;
a plurality of stacks of laminations arranged circumferentially about the shaft to receive the plurality of protrusions therein, wherein each of the plurality of stacks of laminations comprises a plurality of lamination groups arranged axially along a length of the shaft and wherein each of the plurality of lamination groups comprises a plurality of laminations; and
a plurality of permanent magnets configured to generate a magnetic field that interacts with the stator magnetic field to produce a torque, wherein each permanent magnet is disposed between a respective pair of adjacent stacks of laminations;

wherein each of the plurality of laminations includes a shaft protrusion cut formed therein to receive a respective shaft protrusion, and wherein, for each of the plurality of lamination stacks, the shaft protrusion cuts formed in the laminations of a respective lamination group are angularly offset from the shaft protrusion cuts formed in the laminations in an adjacent lamination group.

2. The machine of claim 1 wherein the shaft comprises a single continuous shaft, with the plurality of protrusions being formed integrally with the main shaft body.

3. The machine of claim 1 wherein each permanent magnet disposed between a respective pair of adjacent stacks of laminations comprises a number of magnet blocks, with a magnet block corresponding to each of the lamination groups.

4. The machine of claim 3 wherein the plurality of stacks of laminations collectively form a rotor core, and wherein each of the plurality of lamination stacks forms a rotor pole of the rotor core.

5. The machine of claim 1 wherein the plurality of lamination groups includes a first lamination group, a second lamination group, and a third lamination group, wherein the second lamination group is axially positioned between the first lamination group and the third lamination group.

6. The machine of claim 5 wherein the shaft protrusion cuts formed in the laminations of the second lamination group are formed so as to be centered on the laminations.

7. The machine of claim 6 wherein the shaft protrusion cuts formed in the laminations of the first lamination group and the laminations of the third lamination group are formed so as to be offset from center on the laminations, with the shaft protrusion cuts formed in the laminations of the first lamination group being offset from center in a first angular direction and the shaft protrusion cuts formed in the laminations of the third lamination group being offset from center in a second angular direction opposite the first angular direction.

8. The machine of claim 7 wherein the shaft protrusion cuts formed in the laminations of the first lamination group and the laminations of the third lamination group are offset from center by an equal angle so as to be symmetrically formed about the shaft protrusion cuts formed in the laminations of the second lamination group.

9. The machine of claim 7 wherein the shaft protrusion cuts formed in the laminations of the first lamination group and the laminations of the third lamination group are offset from center by a different angle so as to be asymmetrically formed about the shaft protrusion cuts formed in the laminations of the second lamination group.

10. The machine of claim 1 wherein the angular offset between the shaft protrusion cuts formed in the laminations of adjacent lamination groups is equal to or less than half of a stator slot pitch.

11. The machine of claim 1 wherein the stator assembly and rotor assembly make up a segmented spoke electric motor having distributed windings.

12. A method for assembling an internal permanent magnet machine, the method comprising:
providing a stator assembly comprising a stator core having a plurality of stator teeth, with stator windings wound on the stator teeth to generate a stator magnetic field when excited with alternating currents; and
providing a rotor assembly that is rotatable within a cavity formed by the stator assembly, wherein providing the rotor assembly comprises:
providing a shaft comprising a plurality of protrusions, wherein the protrusions extend radially along an axial length of the rotating shaft and are formed circumferentially about the shaft;
placing a plurality of stacks of laminations onto the plurality of shaft protrusions of the shaft such that the plurality of stacks of laminations are positioned circumferentially around the shaft and such that each of the plurality of stacks of laminations is arranged into a plurality of lamination groups along the axial length of the shaft, with the plurality of stacks of laminations being placed onto the plurality of shaft protrusions of the shaft such that adjacent lamination groups in each stack of laminations are positioned on the shaft to have an angular offset relative to each other; and
securing a plurality of permanent magnets in openings defined by the plurality of stacks of laminations, the plurality of permanent magnets generating a magnetic field that interacts with the stator magnetic field to produce a torque.

13. The method of claim 12 wherein providing the shaft comprises extruding the shaft as a single integral shaft.

14. The method of claim 12 further comprising forming a shaft protrusion cut in each lamination in the plurality of stacks of laminations, the shaft protrusion cut configured to receive a shaft protrusion therein.

15. The method of claim 14 wherein forming the shaft protrusion cut comprises laser cutting the shaft protrusion cut in the lamination.

16. The method of claim 14 wherein, for each of the plurality of lamination stacks, the shaft protrusion cuts formed in the laminations of a respective lamination group are angularly offset from the shaft protrusion cuts formed in the laminations in an adjacent lamination group.

17. The method of claim 16 wherein the angular offset between the shaft protrusion cuts in adjacent lamination groups is half of a stator slot pitch.

18. A rotor assembly for use in an internal permanent magnet machine, the rotor assembly comprising:
a shaft including a shaft body and a plurality of protrusions extending radially outward from the shaft body, the plurality of protrusions being formed along an axial length of the shaft and circumferentially about the shaft;
a plurality of stacks of laminations disposed on the radial protrusions, wherein each of the plurality of stacks of laminations comprises a plurality of lamination groups arranged axially along the shaft and wherein each of the plurality of lamination groups comprises a plurality of laminations; and
a plurality of permanent magnets disposed between the plurality of stacks of laminations;
wherein a shape of the laminations in each of the plurality of lamination groups of a stack of laminations is different from the shape of the laminations in others of the plurality of lamination

Assignees

• Gen Electric

Inventors

• Reddy Patel Bhageerath
• El-Refaie Ayman Mohamed Fawzi
• Huh Kum-Kang
• Alexander James Pellegrino

Classifications

• H02K21/16 Primary

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

• H02K2201/06

  Magnetic cores, or permanent magnets characterised by their skew · CPC title

• H02K1/30

  using intermediate parts, e.g. spiders · CPC title

• Y10T29/49012

  Rotor · CPC title

• H02K15/03

  having permanent magnets · CPC title