Permanent magnet synchronous machine

1. A permanent magnet synchronous machine, comprising:

a stator; and

a rotor defining with the stator an air gap and having permanent magnets which are aligned in flux concentration direction and arranged to define a pole pitch,

wherein the stator includes a plurality of teeth disposed in spaced-apart circumferential relationship and separated from one another by a tooth pitch, each of the teeth including a tooth pole terminating in a tooth head adjacent the air gap, with the tooth heads of neighboring teeth being separated from one another by a slot, said tooth heads being constructed to prevent saturation,

wherein a pitch ratio of tooth pitch to pole pitch is ≧2.5.

2. The synchronous machine of claim 1 , wherein the tooth heads have a same height in the circumferential direction.

3. The synchronous machine of claim 1 , wherein the tooth heads have each a height which satisfies the requirement h zk ≧τ p /2 at least from a point τ p /2, whereby b≧τ p /2, wherein h zk is the height of the tooth head, τ p is the pole pitch, and b is the slot opening width.

4. The synchronous machine of claim 1 , wherein the teeth of the stator are arranged in a star-shaped configuration.

5. The synchronous machine of claim 1 , wherein the stator is made of different materials.

6. The synchronous machine of claim 1 , wherein the stator has different tooth pitches in the circumferential direction so that slot openings between neighboring teeth are off-center between symmetry axes of the teeth.

7. The synchronous machine of claim 1 , wherein the stator is made of axially stacked laminations which are made of single segmental sheets or of single-piece construction, said laminations being arranged in a predetermined sequence.

8. The synchronous machine of claim 1 , wherein the tooth heads have a same radial height.

9. The synchronous machine of claim 1 , wherein the stator has a stator yoke for connection of the teeth, wherein the tooth heads, on one hand, and the tooth poles and the yoke, on the other hand, are made of different materials.

10. The synchronous machine of claim 9 , wherein the tooth heads are made of magnetizable material, and wherein the tooth poles and yoke are made of amagnetic material.

11. The synchronous machine of claim 5 , wherein the the tooth head is made of magnetizable material whereas the shaft and the yoke are made of plastic.

12. The synchronous machine of claim 1 , wherein the stator has a stator yoke for connection of the teeth, at least a plurality of the tooth poles being attached to the yoke by a form-fitting connection or by frictional engagement.

13. The synchronous machine of claim 1 , wherein the plurality of the tooth poles is attached to the yoke by a snap connection.

14. The synchronous machine of claim 1 , wherein the tooth heads have a top face comprised of a sequence of straight sections.

15. The synchronous machine of claim 1 , wherein the tooth heads have a curved top face.

16. The synchronous machine of claim 1 , wherein the tooth heads have a stepped top face.

17. The synchronous machine of claim 1 , wherein each of the tooth heads is defined by a symmetry axis and has a top face which is shallower in a marginal area than in an area adjacent to the symmetry axis.

18. The synchronous machine of claim 1 , wherein the permanent magnets are aligned radially inwards in flux concentration direction.

19. The synchronous machine of claim 1 , wherein the tooth heads are of salient configuration.

20. The synchronous machine of claim 1 , wherein neighboring teeth have different configuration.

21. The synchronous machine of claim 20 , wherein the tooth poles of neighboring teeth have different width.

22. The synchronous machine of claim 20 , wherein the tooth heads of neighboring teeth have different width.