Abstract
A shaft includes a bushing for a current conductor, and a holder for positioning the current conductor. The holder secures the current conductor in or over an inflection point of a curve of the current conductor.
Claims
1.-13. (canceled)
14. A shaft, comprising: a bushing for a current conductor; and a holder for positioning the current conductor, said holder securing the current conductor in or over an inflection point of a curve of the current conductor.
15. The shaft of claim 14, wherein the holder includes a base and a cover arranged to enable passage of the current conductor there between.
16. The shaft of claim 14, wherein the shaft includes a slot for receiving the current conductor.
17. The shaft of claim 14, wherein the shaft is a shaft of a slip ring rotor.
18. The shaft of claim 16, wherein the shaft includes three of said slots, with each of the three slots provided for a phase.
19. The shaft of claim 18, wherein each of the three slots receives two of said current conductor.
20. The shaft of claim 14, wherein the current conductor is a stranded wire.
21. The shaft of claim 16, wherein the holder is received in the slot.
22. The shaft of claim 14, wherein the holder has a shape which corresponds to a shape of the current conductor.
23. The shaft of claim 14, further comprising a shaft core, said holder being fastened to the shaft core by a screw connection.
24. The shaft of claim 14, wherein the holder is potted.
25. The shaft of claim 14, wherein the current conductor is potted.
26. The shaft of claim 14, further comprising a binding in a region of the holder to secure the holder in place.
27. The shaft of claim 14, wherein the bushing extends at an angle of 20 degrees to 30 degrees with respect to an axis of the shaft.
28. A method for operating a shaft as set forth in claim 14, said method comprising simulating an operation of the shaft.
29. A computer program product for operating a shaft, comprising a computer-executable program embodied in a non-transitory computer readable medium storing computer readable data, wherein the computer-executable program when loaded into a processor of the computer readable medium and executed by the processor causes the processor to carry out a method as set forth in claim 28.
Description
[0020] The invention and further advantageous configurations of the invention are explained in more detail with the aid of exemplary embodiments illustrated in principle, in which:
[0021] FIG. 1 shows an, in principle, double-fed asynchronous machine,
[0022] FIG. 2 shows a partial longitudinal section of the double-fed asynchronous machine,
[0023] FIG. 3 shows a partial longitudinal section through a shaft,
[0024] FIG. 4 shows a perspective illustration of slots in the shaft,
[0025] FIG. 5 shows an enlarged perspective illustration of a slot in the shaft,
[0026] FIG. 6 shows a longitudinal section through a slot,
[0027] FIG. 7 shows a perspective illustration of a routing of current conductors via the slots,
[0028] FIG. 8 shows a perspective longitudinal section through a shaft,
[0029] FIG. 9 shows a holder for routing the current conductor in the slot,
[0030] FIG. 10 shows a fastening of the current conductor on a fastening ring,
[0031] FIG. 11 shows the cover of the holder in a plan view,
[0032] FIG. 12 shows the cover of the holder looking onto the skis which faces the current conductors, and
[0033] FIG. 13 shows the cover in a rear view.
[0034] In the following figures, similar elements are denoted by the same reference signs.
[0035] FIG. 1 shows a double-fed asynchronous machine 1 having a stator 2 and a slip ring rotor 3, wherein the stator 2 has a winding system 4 which has end windings 5 at the end faces of the stator 2. The slip ring rotor 3 also has a winding system 6, which likewise forms end windings 7. The slip ring rotor 3 is connected to a shaft 8, having an axis 23, in a torsion-resistant manner, which shaft likewise has a slip ring system 9 on an axial end, in particular the OS side (OS: operating side). In this case, the slip ring system 9 has slip rings 18 (see FIG. 2) rotating with the shaft 8, which, via supply lines 13 and 14, provide electric power to the slip ring rotor 3 via one or more brushes 19 (see FIG. 2) in each case, which are mounted on a brush holder 20 (see FIG. 2) in a stationary manner. The supply lines 13 and 14 are current conductors. In a three-phase rotary current system, there are at least three current conductors, wherein only 2 current conductors 13 and 14 are shown in the illustration according to FIG. 1. The current conductors 13 and 14 exit from bushings 12, wherein the bushings 12 can be realized as bores in the shaft 8, wherein the bushings 12 are illustrated in FIG. 2. The bores end in a hollow shaft portion 11 (see FIG. 2) of the shaft 8. If 150 mm.sup.2 stranded wires are used, for example due to relatively low electric currents, the shaft bores can be drilled at an angle of 45°. Owing to the resultant more steeply angled exit and the smaller bend radius of the stranded wires, a cable clamp fastened on the rotor is sufficient to secure the stranded wires. If stranded wires which have a cross-section larger than 150 mm.sup.2 are required owing to higher electric currents, problems can arise with regard to the bend radius.
[0036] FIG. 2 shows, in a more detailed illustration, the slip ring system 9 with part of the slip ring rotor 3. In this case, the supply lines 13 and 14 lead from contact points 21 and 22 on the slip ring system 9, via supply lines 13 and 14 inserted into a hollow shaft portion 11, to the bores 12 at the end of the hollow shaft portion 11 and can thus supply the winding system 6 of the slip ring rotor 3 with electric power. The bores 12 are bushings through a shaft core 28 for routing the current conductors 13 and 14. The shaft core 28 is in particular a solid material, in particular comprising steel. The slip ring system 9, which makes up an axial part of a hollow shaft portion 11 of the shaft 8, is mounted on the shaft portion 10. Such slip ring rotors 3 are used for example in wind power plants, which have double-fed asynchronous machines as a generator.
[0037] FIG. 3 shows a partial longitudinal section through the shaft 8. This shows, in an enlarged illustration, the passage of the current conductor 14 through the shaft core 28, which has an axis 23. In this case, the current conductor 14 is routed through a sleeve 17 in the bushing 12. The current conductor 14 is also located in a hollow shaft portion 11 in the shaft 8. The electrical connection between the rotor and the slip ring (not illustrated in FIG. 3) is realized for example by two 240 mm.sup.2 stranded wires for each phase and routed into the shaft 8 through corresponding bores 12. The electric machine (i.e. in particular the dynamoelectric machine) is in particular a three-phase electric machine for a rotary current application, as is the case in wind generators. For mechanical securing, after the placement of the current conductor(s), the shaft bore, i.e. the hollow shaft portion 11, can then be at least partially filled with potting compound 41.
[0038] FIG. 4 shows a perspective illustration of slots 29 and 30 in the shaft 8 or in the shaft core 28. The shaft core 28 has three slots here, which are uniformly distributed over the circumference of the shaft core 28, wherein only two slots 29 and 30 are illustrated according to FIG. 4. Since 150 mm.sup.2 stranded wires were hitherto used in wind generators owing to relatively low currents, the bushings (shaft bores), not shown in FIG. 4, could be drilled at an angle of ca. 45°. Owing to the resultant more steeply angled exit and the smaller bend radius of the stranded wires, a cable clamp fastened on the rotor was hitherto sufficient to secure the stranded wires. An increased weight of the stranded wires due to the greater diameter for higher current strengths in more powerful wind generators and an altered geometry of the bores as bushings for the current conductor, i.e. in particular for one or more stranded wires, at an angle of for example ca. 25° in the shaft 8, can cause cracks to occur, in particular when a potting material is present. It can be assumed from this that the stranded wires will become deformed. This in turn results in damage to the stranded wires and can consequently result in failure of the machine. As a result of using slots 29, 30, the geometrical extent of the stranded wires or the current conductors can be altered, in particular improved. The smaller the diameter of the current conductor, the smaller the minimum bend radius. With a small bend radius, it is possible to select a large angle of e.g. 40° to 50° in the shaft for the bushing. The greater the diameter of the current conductor (e.g. >=240 mm.sup.2), the greater the minimum bend radius. With a large minimum bend radius, it is necessary to select a larger angle of e.g. 20° to 30° in the shaft for the bushing. The angle relates to the longitudinal alignment of the bushing in relation to the axis 23. The use of slots 29, 30 adjoining the respective bushing can influence the applied bend radius of the current conductors. Cracks, which would otherwise be expected in an embodiment without slots, can thus be prevented from occurring as a result of a larger bend radius e.g. of stranded wires with large diameters. Deformation of the stranded wires can namely be assumed from the cracks. This in turn results in damage to the wires and can therefore result in failure of the machine. To facilitate the placement of the current conductors, in particular the stranded wires, and/or to ensure that the minimum bend radius is observed, at least three slots are milled into the shaft 8, i.e. into the shaft core 28. Only two slots 29, 30 are shown in FIG. 4, wherein the third slot is located on the rear side of the shaft illustrated in a perspective view. In one configuration of the shaft 8, one slot is provided for each electric phase (U, V, W).
[0039] FIG. 5 shows an enlarged perspective illustration of the slot 29 in the shaft 8. From a somewhat altered perspective, two bushings 12, through which current conductors can be routed, can now be seen in FIG. 5. The bushings 12 directly adjoin the slot 29. Notches 33, 33′ are also shown, in which protrusions 32, 32′ of a holder 24 can engage.
[0040] FIG. 6 shows a longitudinal section through the shaft 8 and through the slot 29 with the notch 33 and a bushing 12, which adjoins the slot 29. Two further bushings 12 are also shown, although they adjoin a different slot which is not shown in FIG. 6.
[0041] FIG. 7 shows a perspective illustration of the routing of current conductors 13, 13′, 14, 14′, 15, 15′. The routing of the current conductors 13, 13′ is shown in the still open slot 29. The slot 29 has notches 33, 33′. The current conductors 14, 14′ are routed in the slot 30. The current conductors 15, 15′ are routed in the slot 31, wherein the slot 31 in FIG. 7 is located on the rear side in this view due to the perspective illustration and is therefore not illustrated. The current conductors 13, 13′, 14, 14′ 15, 15′ are fastened on a web 37. The web 37 is designed to be annular and has a spoke 42. Two stranded wires are placed in each slot and then secured by a cable holder 43, which in particular comprises plastic material.
[0042] FIG. 8 shows a perspective longitudinal section through the shaft 8. It is shown how the holder 24 holds the current conductor 13 in the slot 29. It is furthermore shown how the conductors 13, 15, 15′ are routed into the hollow shaft portion 11. The current conductors can also be completely or partially potted therein, although this is not shown in FIG. 8. In the example according to FIG. 8, two stranded wires are placed by way of example in each slot and then secured by a plastic cable holder. The shape of the holder 24 is adapted to the stranded-wire diameter and the slot 29 in the shaft 8 and thus ensures an optimum and preferably stress-free extent of the stranded wires, such as the stranded wire 13. The holder for the current conductor(s) can be made from a plastic material. The holders, like the holder 29, can each be fastened on the shaft 8, i.e. on the shaft core 28, by 2×M8 screws (not illustrated in FIG. 8). The holders hold the current conductors, for example stranded wires, in position. Gaps between the shaft 8, the holders and the stranded wires can be filled with potting compound (not illustrated in FIG. 8). After the potting compound has hardened, the region of the shaft is in particular bound and then impregnated with the fully assembled rotor.
[0043] FIG. 9 shows a holder 24 for routing the current conductor in the slot. The holder 24 has a base 25 and a cover 26. The current conductor 13 is routed between the base 25 and the cover 26. The current conductor 13 has a curve 35, which has an inflection point 40 in a region between the base 25 and the cover 26. The inflection point is a mathematical term. The term is known from curve sketching. In the inflection point, the 2.sup.nd derivation of the considered function of a graph is zero. At the inflection point, the graph, i.e. the curve here, alters the direction of its curvature. As FIG. 9 shows, the holder 24 can be secured by means of a binding 16. By using the holder 24, the placement of the current conductors (for example as stranded wires or as a solid material) can be clearly defined whilst observing the bend radii. The current conductors are sunk in the shaft and the active centrifugal forces caused by rotation are absorbed by the holder, in particular the cover 26 and/or the binding. The load on the current conductors is in particular reduced to a minimum and the formation of cracks can be prevented or reduced. This in turn has the consequence of ensuring the function of the machine, in particular the generator.
[0044] FIG. 10 shows an illustration similar to FIG. 7, wherein the fastening of the current conductors on a fastening ring 38 is illustrated from a different perspective. FIG. 10 shows that the slots through the holder 24 are closed in particular such that they are flush with the further surface of the shaft 8. In this case, the cover of the holder 24 is visible from the outside. In one configuration of the shaft, to facilitate the placement of the current conductors, in particular the stranded wires, and to ensure that the minimum bend radii are observed, three slots, one for each phase, are incorporated, in particular milled, into the shaft.
[0045] FIG. 11 shows the cover 26 of the holder in a plan view. The cover 26 has prongs 36, 36′, 36″. A space for routing a current conductor is located between the prongs 36 and 36′. This likewise applies to the space between the prongs 36′ and 36″. The cover 26 has protrusions 32 and 32′. A hole, through which a fastening screw (not illustrated) can be guided, is located in these protrusions. Owing to the shape of the holder (which can also be referred to as a cable holder), it is possible to minimize the exit angle of the current conductor. This is achieved in particular since an optimum adaptation to the stranded-wire geometry can be realized in two separate channels. The channels are constructed in particular as grooves, such as are also illustrated in FIGS. 12 and 13. By minimizing the exit angle, it is possible to prevent additional stresses occurring as a result of the bend radii being smaller than the minimum. Contact with sharp edge surfaces of the shaft 8 can also be prevented. The use of the holder 24 also reduces the quantity of the required potting compound which can have a negative effect on the centrifugal forces.
[0046] FIG. 12 shows the cover 26 (according to FIG. 11) of the holder looking onto the side which faces the current conductors. It is shown how the prong 36′ merges into a web 37, wherein the web 37 positions and separates the current conductors to be received. FIG. 12 shows a view 39 of the cover 26 from the rear, which is incorporated in the following FIG. 13.
[0047] FIG. 13 shows the cover in a rear view, wherein grooves 34, 34′ and the position of the web 37 are clearly evident.
