METHOD FOR REWORKING A FAULTY WELDED JOINT OF A HAIRPIN WINDING

Abstract

A method for reworking a defective welded connection of a hairpin winding for a rotor or stator of an electrical machine, including providing the hairpin winding applied to a winding support. The hairpin winding has at least one conductor formed from multiple conductor sections. The conductor sections of the respective conductor are welded in pairs at a respective welded connection by a first welding method, and at least one of the welded connections is a defective welded connection. The defective welded connection is severed, and the conductor sections to be welded, which were previously connected by the defective welded connection, are connected by way of a connecting method that differs from the first welding method.

Claims

1-8. (Canceled)

9. A method for reworking a defective welded connection of a hair-pin winding for a rotor or stator of an electrical machine, comprising: providing the hairpin winding applied to a winding support, wherein the hairpin winding has at least one conductor formed from multiple conductor sections, wherein the conductor sections of the respective conductor are welded in pairs at a respective welded connection by a first welding method, wherein at least one of the welded connections is a defective welded connection, severing the defective welded connection, and connecting the conductor sections to be welded, which were previously connected by the defective welded connection, by way of a connecting method that differs from the first welding method, in particular by way of a second welding method.

10. The method as claimed in claim 9, wherein a connection method is used as the connection method which applies additional material to the conductor sections to be welded and/or in that the first welding method is a beam welding method.

11. The method as claimed in claim 10, wherein gas metal arc welding is used as the connection method.

12. The method as claimed in claim 10, wherein CMT welding or metal inert gas welding or metal active gas welding is used as the connection method.

13. The method as claimed in claim 9, wherein the defective welded connection is severed by cutting off an area comprising the defective welded connection from the conductor sections to be connected.

14. The method as claimed in claim 10, wherein a volume of the additional material is applied by the connection method that is between 50% and 200% or between 80% and 120% of the volume of the cut off area.

15. The method as claimed in claim 9, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

16. The method as claimed in claim 9, wherein the provision of the hairpin winding applied to a winding support comprises: providing a winding support and multiple bracket-shaped conductor sections, axially inserting the conductor sections into the winding support in such a way that two slot sections of each conductor section extend in a respective slot of the winding support, bending the free ends of the slot sections in a respective direction in the circumferential direction of the winding support, connecting a respective free end to a free end of a respective further conductor section by way of a first welding method to form at least one conductor, wherein at least one of the welded connections is a defective welded connection.

17. The method as claimed in claim 11, wherein CMT welding or metal inert gas welding or metal active gas welding is used as the connection method.

18. The method as claimed in claim 10, wherein the defective welded connection is severed by cutting off an area comprising the defective welded connection from the conductor sections to be connected.

19. The method as claimed in claim 11, wherein the defective welded connection is severed by cutting off an area comprising the defective welded connection from the conductor sections to be connected.

20. The method as claimed in claim 4, wherein the defective welded connection is severed by cutting off an area comprising the defective welded connection from the conductor sections to be connected.

21. The method as claimed in claim 11, wherein a volume of the additional material is applied by the connection method that is between 50% and 200% or between 80% and 120% of the volume of the cut off area.

22. The method as claimed in claim 12, wherein a volume of the additional material is applied by the connection method that is between 50% and 200% or between 80% and 120% of the volume of the cut off area.

23. The method as claimed in claim 13, wherein a volume of the additional material is applied by the connection method that is between 50% and 200% or between 80% and 120% of the volume of the cut off area.

24. The method as claimed in claim 10, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

25. The method as claimed in claim 11, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

26. The method as claimed in claim 12, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

27. The method as claimed in claim 13, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

28. The method as claimed in claim 14, wherein after the conductor sections to be connected have been connected, at least the welded connections of the winding are immersed in a bath of insulating material in the axial direction of the rotor or the stator.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0034] Further advantages and details of the invention result from the following exemplary embodiments and the associated drawings. In the schematic figures:

[0035] FIG. 1 shows a sectional detail view of a hairpin winding for a rotor or stator of an electrical machine, and

[0036] FIG. 2 shows the state of a welded connection to be reworked in various steps of an exemplary embodiment of the method according to the invention.

DETAILED DESCRIPTION

[0037] FIG. 1 shows a detailed view of a stator 1 of an electrical machine. The stator 1 comprises a winding support 2 having multiple slots 15, which carries multiple continuous conductors 3, 4 of a hairpin winding. The conductors 3, 4 can, for example, form windings for different phases or can be be windings of one phase connected in parallel. For reasons of clarity, only two such conductors 3, 4 are shown in FIG. 1, wherein one or more conductors 3, 4 are typically used for three phases in real electrical machines.

[0038] The windings formed by the conductors 3, 4 are produced by a method in which the winding support 2 and a large number of bracket-shaped conductor sections 5 are provided, after which the conductor sections are arranged in a basket shape and are inserted axially into the winding support 2 in such a way that two slot sections 6, 7 of each conductor section 5 extend in a respective slot 15 of the winding support, wherein the slot sections 6, 7 are connected by a connecting section 8. The free ends 9 to 12 of the slot sections 6, 7 or the conductor sections 5 are bent in the manner shown in FIG. 1, so that two free ends 10, 11 or 9, 12 come to rest directly adjacent to one another. This is also known as twisting. The free ends 10, 11 and 9, 12 are then welded by a first welding method, for example laser welding or another beam welding method, to produce respective welded connections 13, 14.

[0039] In the procedure described, a large number of welded connections 13, 14 are produced between different conductor sections 5, for example more than 200 welded connections, so that even with a relatively low error rate of the welding method of, for example, 0.1%, there is a relatively high proportion of defective stators in which at least one of the welded connections 13, 14 is defective.

[0040] Defective welded connections 13, 14 can be detected, for example, by a manual or automatic inspection. It is assumed hereinafter that the welded connection 13 is defective. A method for reworking this welded connection 13 is therefore then carried out for the welded connection 13, which is explained in more detail hereinafter with reference to FIG. 2.

[0041] In this case, in step S1, the hairpin winding applied to the winding support 2 is first provided, as explained above. After the defective welded connection 13 has been detected, in step S2, an area 15 comprising the defective welded connection 13 is cut off from the conductor sections 5 to be connected or from the free ends 10, 11, for example by a cutting process.

[0042] As can be seen in FIG. 2, the stripped length 16 of the conductor ends is reduced to a shorter stripped length 17 as a result. If a beam welding method were to be used again to reconnect the conductor sections 5 or the free ends 10, 11, this would potentially result in a large heat input in the area of the insulation, by which this can be damaged. On the other hand, after such reworking, the welded connection 13 would be considerably shorter than the non-reworked welded connections 14, which would be disadvantageous, for example, if the welded connections 13, 14 are immersed in a bath of insulating material after the connecting, since in this case the reworked welded connections 13 cannot be reliably insulated under certain circumstances.

[0043] Therefore, in step S3, a connection method differing from the first welding method, thus in particular not a beam welding method, is used to reconnect the conductor sections 5 or their free ends 10, 11. In order to avoid the above-explained disadvantages, a connection method is used here that applies additional material 18 to the conductor sections 5 to be welded or to their free ends 10, 11. Gas metal arc welding can be used as the connection method, in which the welding electrode is partially melted and forms a part of the welded connection. CMT welding can be used particularly advantageously, since in this case there is a particularly low heat input and damage to the insulation of the conductor sections 5 can thus be particularly reliably avoided.

[0044] A volume of additional material 18 is preferably applied in the connection method, which essentially corresponds to the volume of the severed region 15, so that, as can be seen in FIG. 2 from a comparison of the state in step S1 and the state after step S3, overall an at least similar shape of the welded connection 13 results as before the reworking. In particular, the stripped length 16 or the length by which the welded connection 13 protrudes beyond the winding support 2 after such reworking can essentially correspond to the corresponding lengths for other welded connections 14 for which no reworking has taken place.

[0045] After all defective welds 13 have been reworked, connection bridges can be placed and/or the welded joints 13, 14 can be insulated, for example, by immersing the welded connections in a bath of insulating material in the axial direction of the rotor or stator, respectively, in order to complete the production of the rotor or stator, respectively.