Composite stator for axial flux electric machines and methods of assembling the same

1. A stator comprising:

an annular back iron for an axial flux machine, said annular back iron defining an axis of rotation therethrough, said annular back iron comprising a first material; and

a plurality of stator module packs annularly disposed around said annular back iron, each stator module pack of said plurality of stator module packs including:

a housing defining an enclosed volume;

a plurality of stator teeth attached to said housing and disposed in the enclosed volume, said plurality of stator teeth extending axially from said annular back iron and annularly disposed around said annular back iron, each stator tooth of said plurality of stator teeth having a first end proximate said annular back iron and a second end, said plurality of stator teeth comprising said first material; and

a plurality of tooth tips attached to said plurality of stator teeth, each tooth tip of said plurality of tooth tips attached to said second end of a different stator tooth of said plurality of stator teeth, said plurality of tooth tips comprising a second material different than said first material.

2. The stator in accordance with claim 1 , wherein said first material comprises laminated steel.

3. The stator in accordance with claim 1 , wherein said second material comprises a soft magnetic composite (SMC) material.

4. The stator in accordance with claim 1 , wherein said plurality of tooth tips is attached to said plurality of stator teeth using an adhesive.

5. The stator in accordance with claim 1 , further comprising a plurality of stator windings, each stator winding wound on a different tooth of said plurality of stator teeth.

6. The stator in accordance with claim 1 , wherein each tooth tip extends beyond an edge of a respective stator tooth toward an adjacent tooth of said plurality of stator teeth.

7. The stator in accordance with claim 1 , wherein each tooth tip of said plurality of tooth tips is substantially planar.

8. The stator in accordance with claim 1 , wherein at least one tooth tip of said plurality of tooth tips has a non-planar shape.

9. The stator in accordance with claim 1 , wherein each said stator module pack of said plurality of stator module packs includes a plurality of stator modules, each stator module of said plurality of stator modules including at least one stator tooth of said plurality of stator teeth and a winding disposed on said at least one stator tooth of said plurality of stator teeth.

10. The stator in accordance with claim 9 , wherein each said stator module pack of said plurality of stator module packs includes a circuit board attached to said plurality of stator modules and disposed at least partially in the enclosed volume.

11. A method of assembling a stator having an annular back iron of a first material, the method comprising:

arranging a plurality of stator module packs annularly around the annular back iron, each stator module pack of the plurality of stator module packs including a housing defining an enclosed volume and a plurality of stator teeth attached to housing and disposed in the enclosed volume, the plurality of stator teeth extending axially from the annular back iron, each stator tooth of the plurality of stator teeth having a first end proximate the annular back iron and a second end, the plurality of stator teeth comprising the first material, adjacent stator teeth of the plurality of stator teeth defining a slot with a substantially constant width from the first end to the second end of each adjacent stator tooth;

winding stator windings on each stator tooth without needle winding; and

attaching a plurality of tooth tips to the plurality of stator teeth, wherein each tooth tip of the plurality of tooth tips is attached to the second end of a different stator tooth of the plurality of stator teeth, the plurality of tooth tips comprising a second material different than the first material.

12. The method in accordance with claim 11 , wherein attaching the plurality of tooth tips comprises attaching the plurality of tooth tips sized to produce an air gap between adjacent teeth that is smaller than the substantially constant width of the slot.

13. The method in accordance with claim 12 , wherein attaching the plurality of tooth tips sized to produce an air gap between adjacent teeth that is smaller than the substantially constant width of the slot comprises attaching the plurality of tooth tops sized to produce an air gap sized to require needle winding if the stator windings are wound on the plurality of stator teeth after tooth tips are attached to the plurality of stator teeth.

14. The method in accordance with claim 11 , wherein attaching the plurality of tooth tips comprises attaching the plurality of tooth tips to the plurality of stator teeth with adhesive.

15. The method in accordance with claim 14 , wherein the first material comprises laminated steel.

16. The method in accordance with claim 11 , wherein the second material comprises a soft magnetic composite (SMC) material.