Electrical machines

1. An electrical machine comprising:

a stator; and

a housing having an internal bore;

the stator comprising an annular core removably mounted within the bore of the housing; wherein:

the core comprises at least one key projecting radially outwardly from a radially outer surface thereof;

the housing comprises at least one keyway in the bore;

the at least one key of the core being received within the at least one keyway of the housing;

the core comprises a plurality of circumferentially adjacent segments, each segment comprising at least one key of the at least one key; and

the core is retained axially in the housing by at least one retaining element extending over an axial end face of the core, wherein the at least one retaining element is removable from the housing to allow at least one segment of the core to be removed from the housing.

2. The electrical machine as claimed in claim 1 , wherein the at least one keyway comprises a shoulder at one axial end thereof, the corresponding at least one key of the core being retained between the shoulder and the retaining element.

3. The electrical machine as claimed in claim 2 , wherein the at least one retaining element comprises a plurality of clamping plates mounted to an axial end surface of the housing and radially overlapping the axial end face of the core.

4. The electrical machine as claimed in claim 3 , wherein the plurality of clamping plates includes three clamping plates.

5. The electrical machine as claimed in claim 1 , wherein the at least one key formed on the core and the at least one keyway formed in the housing have a form interlocking shape.

6. The electrical machine stator as claimed in claim 5 , wherein the at least one key comprises an enlarged or flared head portion and a neck portion extending from the flared head portion to the radially outer surface of the core, and the at least one keyway comprises an enlarged or flared base portion and a neck portion extending therefrom to the bore.

7. The electrical machine stator as claimed in claim 6 , wherein the core is retained in the housing an interference fit between the at least one key of the core and the at least one keyway of the housing and wherein there is an interference fit only between the head portion of the at least one key and the base portion of the at least one keyway.

8. The electrical machine as claimed in claim 5 , wherein the interlocking shape is a dovetail shape.

9. The electrical machine as claimed in claim 1 , wherein the core is made from CoFe.

10. The electrical machine as claimed in claim 1 , further comprising a rotor arranged radially within the core.

11. A method of assembling the electrical machine as claimed in claim 1 comprising:

mounting the core to the housing by positioning the at least one key of the core within the at least one keyway of the housing.

12. The electrical machine of claim 1 , wherein the at least one retaining element is mounted to the housing by threaded fasteners.

13. A method of repairing an electrical machine that includes a stator and a housing having an internal bore, wherein the stator includes an annular core mounted within the bore of the housing, and wherein: the core comprises at least one key projecting radially outwardly from a radially outer surface thereof; the housing comprises at least one keyway in the bore; and the at least one key of the core being received within the at least one keyway of the housing;

wherein the core is retained axially in the housing by at least one retaining element extending over an axial end face of the core and wherein the core comprises a plurality of circumferentially adjacent segments, each segment comprising at least one key of the at least one key, the method comprising:

removing at least one retaining element from the housing;

removing at least one core segment from the housing;

replacing the at least one core segment with a replacement core segment; and

mounting a replacement retaining element to the housing to retain the replacement core segment in the housing.

14. The method of claim 13 , wherein the replacement retaining element is different than the at least one retaining element.

15. The method of claim 13 , wherein the replacement retaining element is the same as the at least one retaining element.

16. An electrical machine comprising:

a stator; and

a housing having an internal bore;

the stator comprising an annular core mounted within the bore of the housing; wherein:

the core comprises at least one key projecting radially outwardly from a radially outer surface thereof;

the housing comprises at least one keyway in the bore;

the at least one key of the core being received within the at least one keyway of the housing;

the core comprises a plurality of circumferentially adjacent segments, each segment comprising at least one key of the at least one key; and

the core is retained in the housing by an interference fit between the at least one key of the core and the at least one keyway of the housing, wherein the at least one key formed on the core and the at least one keyway formed in the housing have a form interlocking shape, the at least one key comprises an enlarged or flared head portion and a narrower neck portion extending from the flared head portion to the radially outer surface of the core, the at least one keyway comprises an enlarged or flared base portion and a narrower neck portion extending therefrom to the bore, and there is an interference fit only between the head portion of the at least one key and the base portion of the at least one keyway.