Single phase motor with positive torque parking positions

• US 5,773,908 A
• Filed: 12/05/1996
• Issued: 06/30/1998
• Est. Priority Date: 02/22/1993
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Stephens, Charles M., Soong, Wen Liang
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): ENAD, ELVIN GENARGUE
• Application Number:
  US08/760,755
• Time in Patent Office: 572 Days
• Field of Search: 310/179, 310/49 R, 310/168, 310/156, 310/264
• US Class Current: 310/216.094
• CPC Class Codes: H02K 1/146 consisting of a generally annular yoke with salient poles
• CPC Class Codes: H02K 2201/06 Magnetic cores, or permanent magnets characterised by their skew
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02P 25/04 Single phase motors, e.g. capacitor motors
• CPC Class Codes: H02P 6/26 Arrangements for controlling single phase motors

Abstract

A motor with positive torque parking positions. The motor includes a rotor which is rotatable about an axis of rotation and a stator in magnetic coupling relation with the rotor. The stator includes a plurality of teeth each having a radially extending shaft and an axially extending face. The faces of the stator teeth define an aperture for receiving the rotor and the faces of the stator teeth and the rotor define an air gap therebetween. Each stator tooth has a notch in its face that is approximately at least as wide as the shaft of the stator tooth so that the stator has a magnetic configuration relative to the rotor for parking the rotor in a rest position corresponding to a positive torque starting position. The motor also includes a winding on the shafts of the stator teeth and a control circuit for controlling current in the winding whereby an electromagnetic field is produced for rotating the rotor at a desired speed or torque during operation of the motor.

Claims

1. A motor comprising:

a rotor rotatable about an axis of rotation;

a stator in magnetic coupling relation with the rotor, said stator including a plurality of teeth each having a radially extending pole body and an axially extending face, said pole bodies of the stator teeth each having a generally uniform thickness throughout its radial extent, said faces of the stator teeth defining an aperture for receiving the rotor, said faces of the stator teeth and said rotor defining an air gap therebetween, each stator tooth having a notch in its face which is approximately at least as wide as the thickness of the pole body of the respective stator tooth, said notch defining a modified air gap reluctivity between the stator and the rotor for parking the rotor in a rest position corresponding to a positive torque starting position;

a winding on the pole bodies of the stator teeth; and

a control circuit for controlling current in the winding whereby an electromagnetic field is produced for rotating the rotor at a desired speed or torque during operation of the motor.

2. The motor of claim 1 wherein each notch has a generally rectangular cross section transverse to the axis of rotation.

3. The motor of claim 1 wherein each notch has a width and a depth relative to the face of its respective stator tooth, said depth being a function of the inverse of said width.

4. The motor of claim 1 wherein each notch has a width relative to the face of its respective stator tooth between approximately 60°

(electrical) and 90°

(electrical).

5. The motor of claim 1 wherein each notch is offset relative to a center line of its respective stator tooth thereby defining an asymmetrical air gap relative to the center line.

6. The motor of claim 1 wherein the stator comprises a generally cylindrical stator core having two axially facing ends and a stator reluctance section positioned axially adjacent one of the ends of the stator core.

7. The motor of claim 6 wherein the pole bodies of the stator teeth extend radially from the stator core so that each stator tooth has two axially facing surfaces and wherein the stator reluctance section has a plurality of legs, each leg of the stator reluctance section corresponding to one of the stator teeth and being positioned axially adjacent one of the axially facing surfaces of its corresponding stator tooth.

8. The motor of claim 7 wherein a portion of each leg of the stator reluctance section is substantially coterminous with the pole body of its corresponding stator tooth.

9. The motor of claim 8 wherein another portion of each leg of the stator reluctance section extends into the air gap between the stator and the rotor at the notch of its corresponding stator tooth.

10. The motor of claim 6 wherein the stator includes a non-magnetic spacer section between the stator core and the stator reluctance section.

11. The motor of claim 6 wherein the rotor comprises a generally cylindrical rotor core having two axially facing ends and a rotor reluctance section positioned axially adjacent one of the ends of the rotor core.

12. The motor of claim 11 wherein the rotor comprises a plurality of permanent magnet elements situated radially on an outer surface of the rotor core so that each permanent magnet element has two axially facing ends substantially level with the ends of the rotor core and wherein the rotor reluctance section has a plurality of legs, each leg of the rotor reluctance section corresponding to one of the permanent magnet elements and being positioned axially adjacent one of the axially facing ends of its corresponding permanent magnet element.

13. The motor of claim 12 wherein each leg of the rotor reluctance section overlaps at least in part one of the ends of the permanent magnet elements and extends into the air gap between the stator and the rotor.

14. The motor of claim 12 wherein each leg of the rotor reluctance section has a width less than that of its corresponding permanent magnet element.

15. The motor of claim 12 wherein each leg of the rotor reluctance section is situated on one of the ends of its corresponding permanent magnet element at a predetermined angular position relative to the permanent magnet element.

16. The motor of claim 11 wherein the rotor has an end cap on each of its ends and wherein the rotor reluctance section is positioned on one of the end caps.

17. The motor of claim 11 wherein the rotor and stator reluctance sections are positioned radially adjacent each other.

18. The motor of claim 1 wherein the rotor comprises a generally cylindrical rotor core and a plurality of permanent magnet elements situated radially on an outer surface of the rotor core along a helical path which traverses a skew angle θ

with respect to the axis of rotation.

19. The motor of claim 18 wherein the skew angle 0 is between approximately 60°

(electrical) and 90°

(electrical).

20. The motor of claim 1 comprising a single phase, single winding, electronically commutated dynamoelectric machine.

21. A stationary assembly for a motor, said motor having a rotor which is rotatable about an axis of rotation, said stationary assembly being in magnetic coupling relation with the rotor, said stationary assembly comprising:

a stator core having a plurality of teeth, said teeth each having a radially extending pole body and an axially extending face, said pole bodies of the stator teeth each having a generally uniform thickness throughout its radial extent, said faces of the teeth defining an aperture for receiving the rotor, said faces of the teeth and said rotor defining an air gap therebetween, each tooth having a notch in its face which is approximately at least as wide as the thickness of the pole body of the respective stator tooth, said notch defining a modified air gap reluctivity between the stator core and the rotor for and the rotor in a rest position corresponding to a positive torque starting position; and

a winding on the pole bodies of the teeth, said winding being adapted to be energized for producing an electromagnetic field to rotate the rotor at a desired speed or torque during operation of the motor.

22. The stationary assembly of claim 21 wherein each notch has a generally rectangular cross section transverse to the axis of rotation.

23. The stationary assembly of claim 21 wherein each notch has a width and a depth relative to the face of its respective tooth, said depth being a function of the inverse of said width.

24. The stationary assembly of claim 21 wherein each notch has a width relative to the face of its respective tooth between approximately 60°

(electrical) and 90°

(electrical).

25. The stationary assembly of claim 21 wherein each notch is offset relative to a center line of its respective tooth thereby defining an asymmetrical air gap relative to the center line.

26. The stationary assembly of claim 21 wherein the stator core is generally cylindrical and has two axially facing ends and further comprising a reluctance section positioned axially adjacent one of the ends of the stator core.

27. The stationary assembly of claim 26 wherein the teeth extend radially from the stator core so that each tooth has two axially facing surfaces and wherein the reluctance section has a plurality of legs, each leg of the reluctance section corresponding to one of the teeth and being positioned axially adjacent one of the axially facing surfaces of its corresponding tooth.

28. The stationary assembly of claim 27 wherein a portion of each leg of the stator reluctance section is substantially coterminous with the pole body of its corresponding stator tooth.

29. The stationary assembly of claim 28 wherein another portion of each leg of the stator reluctance section extends into the air gap between the stator and the rotor at the notch of its corresponding stator tooth.

30. The stationary assembly of claim 26 wherein the stator includes a non-magnetic spacer section between the stator core and the stator reluctance section.