Abstract
A stator (20) for an electric machine (21) is proposed, the stator (20) comprising slots (22) for receiving electric windings (23), and at least two teeth (24), wherein respectively one tooth (24) of the stator (20) is formed between two adjacent slots (22), wherein at least two of the teeth (24) have a recess (25) extending at least partially through the respective tooth (24), and within the recesses (25), at least two electric conductors (26) each are arranged which are short-circuited to one another. Moreover, an electric machine (21) is proposed.
Claims
1. A stator for an electric machine, the stator comprising: slots for receiving electric windings, and at least two teeth, wherein respectively one tooth of the stator is formed between two adjacent slots, wherein at least two of the teeth have a recess extending at least partially through the respective tooth, and within the recesses, at least two electric conductors each are arranged which are short-circuited to one another.
2. The stator according to claim 1, in which the recesses each extend in a radial direction, wherein the radial directions each run in parallel to a radius in a cross-section through the stator, and the radius runs through the respective tooth.
3. The stator according to claim 1, in which at least every second tooth has one of the recesses.
4. The stator according to claim 1, in which at least one of the electric conductors cannot be electrically contacted from outside the stator.
5. The stator according to claim 1, in which the electric conductors respectively do not fill the recesses completely.
6. The stator according to claim 1, in which electric conductors within two recesses are electrically connected together.
7. The stator according to the preceding claim, in which electric conductors within two further recesses are electrically connected together, wherein the electric conductors within the two recesses are electrically isolated from the electric conductors within the two further recesses.
8. The stator according to claim 1, in which the electric conductors have a metal.
9. The stator according to claim 1, in which the recesses each comprise an additional slot.
10. The stator according to claim 1, in which the recesses each have an additional slot extending completely through the stator from an inside to an outside.
11. An electric machine having a stator according to any one of the preceding claims, and a rotor that is movable relative to the stator.
12. The electric machine according to the preceding claim, in which an operating wave of the magnetomotive force is different from a fundamental wave of the magnetic flux during operation.
13. The electric machine according to claim 11, in which the recesses are in connection with an air gap arranged between the rotor and the stator.
14. The electric machine according to claim 11, in which the recesses are open towards the side of the stator facing away from the rotor.
Description
[0030] Hereinafter, the stator described herein and the electric machine will be explained in more detail in conjunction with exemplary embodiments and the associated Figures.
[0031] In FIG. 1, a cross-section through an exemplary embodiment of the stator is shown.
[0032] In FIG. 2, a cross-section through an exemplary embodiment of the electric machine is shown.
[0033] FIG. 3 shows a cross-section through an example of a stator.
[0034] In FIG. 4, the magnetic flux density within the air gap is plotted for different harmonic components.
[0035] In FIG. 5, the torque over time is plotted for different electric machines.
[0036] In FIG. 6, a cross-section through a further exemplary embodiment of the electric machine is shown.
[0037] FIG. 1 shows a cross-section through an exemplary embodiment of the stator 20 for an electric machine 21. The stator 20 has slots 22 for receiving electric windings 23. In total, the stator 20 has twelve slots 22. The slots 22 are arranged along the circumference of the stator 20. Moreover, the slots 22 are open towards an inside 29 of the stator 20. Within the slots 22, electric windings 23 are arranged. It is illustrated in FIG. 1 in which direction electric current flows within the electric windings 23 during operation of the electric machine 21. The slots 22 extend partially through the stator 20 in radial directions r. The radial directions r each run in parallel to a radius in a cross-section through the stator 20. The stator 20 has a plurality of laminated sheet packages 33 into which the slots 22 are introduced.
[0038] Moreover, the stator 20 has at least two teeth 24, wherein one tooth 24 of the stator 20 is respectively formed between two adjacent slots 22. The teeth 24 are arranged distributed along the circumference of the stator 20. In total, the stator 20 has twelve teeth 24. The electric windings 23 are wound around each tooth 24 along the circumference of the stator 20.
[0039] The teeth 24, around which none of the electric windings 23 is wound, each have a recess 25 extending at least partially through the respective tooth 24. Thus, every second tooth 24 has a recess 25. The recesses 25 each extend in a radial direction r, wherein the respective radial direction r runs through the respective tooth 24. The recesses 25 each may comprise an additional slot 28. The recesses 25, like the slots 22, extend completely through the stator 20 along a longitudinal axis of the stator 20. Moreover, the recesses 25 or the additional slots 28 extend completely through the stator 20 from an inside 29 towards an outside 30 of the stator 20.
[0040] Furthermore, at least two electric conductors 26 which are short-circuited to one another, are arranged within the recesses 25. In this exemplary embodiment, five electric conductors 26 each are arranged within each recess 25. The electric conductors 26 have an electrically conductive material, for example, a metal. The electric conductors 26 each do not fill the recesses completely. This means that, apart from the electric conductor 26, air is arranged within the recesses 25. At least one of the electric conductors 26 is arranged within the stator 20 such that the electric conductor 26 cannot be electrically contacted from outside the stator 20. This means that this electric conductor 26 is not accessible from outside the stator 20.
[0041] In FIG. 1, it is further illustrated, in which direction current flows in the electric conductors 26 during operation of the electric machine 21. This is achieved in that electric conductors 26 within two recesses 25, which are opposite to one another in a cross-section through the stator 20, are electrically connected together. Electric conductor 26 in adjacent recesses 25 are electrically isolated from one another. Moreover, the stator 20 has four further recesses 27. The further recesses 27 have the same structure as the recesses 25. The electric conductors 26 within two further recesses 27, which are opposite to one another in a cross-section through the stator 20, are electrically connected together. This applies to all of the four further recesses 27. Thus, the stator 20 has three pairs of recesses 25, 27, in which the electric conductors 26 are short-circuited to one another for each pair. Moreover, in each pair of the recesses 25, 27, the recesses 25, 27 are arranged at opposite sides of the stator 20.
[0042] In FIG. 2, a cross-section through an exemplary embodiment of the electric machine 21 is shown. The electric machine 21 has the stator 20 and a rotor 31 that is movable relative to the stator 20. The stator 20 has the structure shown in FIG. 1. The rotor 31 is arranged as an internal rotor at the inside 29 of the stator 20. Between the stator 20 and the rotor 31, an air gap 32 is arranged. The recesses 25, 27 of the stator 20 are in connection with the air gap 32. Moreover, the recesses 25, 27 extend completely through the stator 20 in radial directions r, so that the recesses 25, 27 are open toward the side of the stator 20 facing away from the rotor 31. The rotor 31 has 14 permanent magnets 34 arranged at an outside 30 of the rotor 31. The outside 30 of the rotor 31 is facing the air gap 32. In the electric machine 21, the operating wave of the magnetomotive force is different from the fundamental wave of the magnetic flux during operation. This means that it is not the fundamental wave of the magnetic flux that is utilized for generating torque, but that it is the seventh harmonic component of the magnetomotive force.
[0043] In FIG. 3, a cross-section through an example of a stator 20 is shown. The example shown in FIG. 3 is not an exemplary embodiment. In contrast to the stator 20 shown in FIG. 1, no electric conductors 26 are arranged within the recesses 25 in the example in FIG. 3.
[0044] In FIG. 4, the magnetic flux density within the air gap 32 is plotted for different harmonic components. The order of the harmonic components is plotted on the x-axis. The magnetic flux density is potted in Tesla on the y-axis. The white bars indicate the magnetic flux density for the example of a stator 20 shown in FIG. 3, and the black bars indicate the magnetic flux density for the exemplary embodiment of the stator 20 shown in FIG. 1. Thus, FIG. 4 illustrates the advantages of the exemplary embodiment of the stator 20 shown in FIG. 1.
[0045] In an electric machine having the stator 20 shown in FIG. 1, the 7.sup.th harmonic component of the magnetomotive force is used as an operating wave. This means that the component is utilized for generating torque. Other components of the magnetomotive force have the effect of losses. Consequently, it is advantageous to reduce the magnetic flux density of sub-harmonics and higher harmonics. As compared to an electric machine having the stator 20 of FIG. 3, the magnetic flux density for the fundamental wave is significantly reduced in an electric machine having the exemplary embodiment of the stator 20 of FIG. 1. Further, the magnetic flux density for the harmonic components of the orders 3, 5 and 9 is reduced. Moreover, for an electric machine having the stator 20 of FIG. 1, the magnetic flux density of the 7.sup.th harmonic component is higher than for an electric machine having the stator 20 of FIG. 3. Thus, with an electric machine having the stator 20 of FIG. 1 and the exemplary embodiment of the electric machine 21 of FIG. 2, a higher torque may be generated during operation, and the losses are reduced as compared to an electric machine having the stator 20 of FIG. 3, which has no electric conductors 26. Thus, the electric conductors 26 enable an electric machine having the stator 20 of FIG. 1 and the electric machine 21 of FIG. 2 to be operated more efficiently than an electric machine having the stator 20 of FIG. 3.
[0046] In FIG. 5, the torque over time is plotted for two different electric machines 21. Time is plotted in seconds on the x-axis. The torque is plotted in Nm on the y-axis. The dashed line shows the torque for an electric machine having the stator 20 of FIG. 3. The solid line shows the torque for an electric machine having the stator 20 of FIG. 1. For the stator of FIG. 1, the torque shows a longer transient response, however in total, the torque has a higher value than for the stator 20 of FIG. 3. Thus, the electric conductor 26 within the recesses 25 advantageously enable a higher torque to be generated.
[0047] In FIG. 6, a cross-section through a further exemplary embodiment of the electric machine 21 is shown. In contrast to the exemplary embodiments shown in FIGS. 1 and 2, the recesses 25 extend not completely but only partially through the stator 20 in radial directions r. The recesses 25 each are open towards the air gap 32. Towards an outside 30 of the stator 20 facing away from the air gap 32, the recesses 25 are closed.
[0048] This structure to a decrease of the magnetic resistance for the magnetic flux developed by the voltage induced in the electric conductors 26. Thereby, the losses in the electric machine 21 are further reduced. The torque has the same value as the exemplary embodiment of the electric machine 21 shown in FIG. 2. Consequently, the efficiency degree and thus the efficiency for the exemplary embodiment shown in FIG. 6 is higher than for the exemplary embodiment shown in FIG. 2.
