Slip ring with an insulated fan hub

Abstract

The invention relates to a slip ring for a slip ring unit of an electric machine with a machine rotation axis AD, comprising at least one individual slip ring (12), at least two insulating regions (14) and an electrically insulating outer flange ring (16) arranged at an end, wherein the at least two insulating regions (14) and the at least one individual slip ring (12) are arranged concentrically with respect to the machine rotation axis AD and alternately axially adjacent to each other. The outer flange ring (16) acts as a fan hub and forms a receiving structure (18), which runs along the outer circumference, for attaching axial fan blades (20). The outer flange ring (16) fulfils the three functions of fan flange, electrical insulation and centrifugal force support for the slip ring connections.

Description

[0001] Slip ring with insulated fan hub

[0002] Description

[0003] The invention relates to a slip ring for a slip ring unit of an electrical machine with a machine rotation axis AD, comprising at least one individual slip ring, at least two insulating regions, and an electrically insulating outer flange ring arranged on the end face. The at least two insulating regions and the at least one individual slip ring are arranged concentrically to the machine rotation axis AD and alternately axially adjacent to one another.

[0004] The invention relates to a slip ring unit for a doubly fed asynchronous machine, which can be used, for example, in generators of wind turbines. A slip ring unit is used within the generator, which, together with stationary carbon brushes, ensures power transmission. The slip ring unit is exposed to high thermal loads during line transmission in the megawatt range. The slip ring unit requires forced ventilation or a fan to generate an air flow to cool the entire slip ring unit, consisting of slip rings and carbon brushes. When using a fan, a connection flange or a hub is required to accommodate the fan. The fan and flange must be mechanically robust and axially short, but also inexpensive. Furthermore, high demands are placed on concentricity and strength.From an electrical point of view, it must be ensured that all required clearance and creepage distances to the nearby electrical components are maintained.

[0005] Until now, this generator was operated either with a radial fan, which is positioned on the slip ring on a robust, expensive steel flange disk, or with an axial fan with its own fan hub, which has to be flanged on accordingly. In both cases, maintaining the clearance and creepage distances is difficult in the very limited installation space and makes the respective concepts expensive. DE 10 2013 217 306 AL, for example, shows an electric machine with a slip ring unit, carbon brushes and a radial fan. EP 3 322 047 A1 shows a slip ring unit in which at least one of the insulating segments or insulating areas is provided with pronounced features in order to generate a cooling air flow via the pronounced features during operation. A metallic fan flange is connected to one insulating area. An electrically insulating centrifugal ring is arranged on the front side of this fan flange.The metal fan flange is used to attach fan blades. Therefore, there is a need to find new ways to mount such fans to accommodate ever-increasing performance and larger machines with their increasingly limited installation space.

[0006] The object of the invention is to demonstrate measures that enable an improved fan concept in limited space situations.

[0007] The object is achieved by a slip ring unit having the features of claim 1. Preferred embodiments are specified in the subclaims and the following description, each of which, individually or in combination, may represent an aspect of the invention. If a feature is presented in combination with another feature, this merely serves to simplify the presentation of the invention and is in no way intended to imply that this feature cannot also be a further development of the invention without the other feature.One embodiment relates to a slip ring unit for an electrical machine with a machine rotation axis AD, comprising at least one individual slip ring, at least two insulating regions and an electrically insulating outer flange ring arranged on the end face, wherein the at least two insulating regions and the at least one individual slip ring are arranged concentrically to the machine rotation axis AD and alternately axially adjacent to one another and the outer flange ring is arranged directly adjacent to one of the insulating regions and, acting as a fan hub, forms an outer circumferential receiving structure for fastening axial fan blades.

[0008] The outer flange ring now provided has been modified compared to the conventional design in such a way that it can be used directly to accommodate and attach axial fan blades. The outer flange ring thus functions as both a fan hub and a centrifugal force ring. The outer flange ring can therefore continue to be used as a so-called centrifugal force ring. This eliminates the need for the conventional steel fan flange to which the fan or fan blades were attached.

[0009] The outer flange ring according to the invention is shaped so that the fan blades can be optimally accommodated and connected. At the same time, the outer flange ring meets the requirements for system insulation, compliance with air and creepage distances, and protection of the connecting bolts against centrifugal force. The key difference from conventional designs is that the shape of the fan feet of the fan blades is completely integrated into the outer flange ring, which is manufactured as an insulating molded part made of plastic. This component avoids the high costs of the previous solution, which consisted of stainless steel and generated significant waste during production. The inventive solution eliminates the need for a separate fan hub, as is common with axial fans.Furthermore, it avoids the need to manufacture a die-cast fan hub, as this would involve high molding costs and the problem of maintaining clearance and creepage distances, which would require additional insulation components. This integrated, insulating component in the form of the outer flange ring reduces the required installation space and eliminates the need for additional insulation components. Overall, this design is significantly more cost-effective. The outer flange ring fulfills three functions in one: fan mount or hub, electrical insulation, and centrifugal support for the slip ring connections.

[0010] In a preferred embodiment, a connection device is provided that is electrically and mechanically connected to the at least one individual slip ring and has at least one connecting bolt that protrudes axially through the outer flange ring. Each of the individual slip rings is electrically connected to one or more connecting bolts, so that the electrical energy provided on a running surface of the respective individual slip ring can be supplied to the connecting bolt.

[0011] In a further preferred embodiment, the receiving structure consists of a circumferential sequence of receiving pockets and lateral limiting cams. The receiving pockets are bordered on each circumferential side by a limiting cam. The opposing side walls of the limiting cams are expediently tapered towards one another, viewed axially, so that a fan blade inserted radially from the outside sits in a receiving funnel and is firmly held. Differently shaped receiving pockets can also be provided. The fan blades are held in place by the limiting cams on the blade base and by bores on the receiving flange and an opposite thrust ring having corresponding bores.

[0012] In a further preferred embodiment, the receiving pockets are each delimited in the axial direction by a radial abutment collar. The radial abutment collar serves in particular as a defined axial stop against which the fan blades are placed and preferably also fastened, e.g., screwed. With regard to the material properties of the outer flange ring, it is particularly preferred if it is designed as a plastic molded part or as a plastic milled part. In this case, the outer flange ring can be designed as a composite metal-plastic component with a metal core and a plastic coating.

[0013] In a particularly preferred and alternative embodiment, it is provided that the insulating region adjacent to the outer flange ring is formed integrally with the outer flange ring.

[0014] A preferred embodiment includes a hollow shaft arranged concentrically within the at least one individual slip ring and within the at least two insulating regions, and the outer flange ring is attached to the hollow shaft at the end. In a specific embodiment, the hollow shaft may extend into a central bore of the outer flange ring, and the hollow shaft and the outer flange ring are connected to one another in the axially overlapping region.

[0015] The object is also achieved by an electrical machine, in particular for a wind turbine, comprising a slip ring unit as described above.

[0016] Finally, the task is also solved by a wind turbine with a similar electrical machine.

[0017] The invention will be explained below by way of example with reference to the accompanying drawings using preferred embodiments, wherein the features presented below can represent an aspect of the invention both individually and in combination. They show:

[0018] Fig. 1 : a view of a slip ring unit;

[0019] Fig. 2: a detailed view of the slip ring according to Figure 1; Fig. 3: an axial section of a slip ring with an outer flange ring for accommodating fan blades;

[0020] Fig.4: a perspective view of a slip ring with an outer flange ring for receiving fan blades;

[0021] Fig. 5a), 5b): further details of a slip ring and

[0022] Fig. 6: another perspective view of a slip ring.

[0023] Figure 1 shows an axial end of a conventional example of a slip ring unit 2, which may be a slip ring unit of a generator of a wind turbine. The slip ring unit 2 includes a slip ring 10 comprising several individual slip rings 12, namely one for each of the three electrical phases and one for potential equalization. The slip ring 10 is tapped by a brush arrangement 6 of conventional design. The slip ring 10 is mounted within the slip ring unit 2 of an electrical machine for rotation about a machine rotation axis AD.

[0024] On the front side of the slip ring 10 are a centrifugal ring 4 and a fan flange 5 made of steel, which represent two separate components. The fan flange 5 serves to attach a radial fan ring 8 with fan blades. The centrifugal ring 4 is made electrically insulating. Connecting bolts 24 protrude from the centrifugal ring 4, distributed axially around its circumference. The connecting bolts 24 are part of a connecting device 22 that electrically connects the individual slip rings 12 to the respective connecting bolts 24.

[0025] Figure 2 shows a detail of the entire slip ring 10 already described in relation to Figure 1. Insulating regions 14 are arranged between the individual slip rings 12 in order to electrically insulate the individual slip rings 12 from one another. Between the centrifugal ring 4 and the adjacent insulating region 14 is the steel fan flange 5, to which the radial fan ring 8 can be fastened; see Figure 1 for this. Figures 3 and 4 show the slip ring 10 in a possible embodiment according to the invention. An outer flange ring 16 is provided which is electrically insulating and arranged on the end face. The outer flange ring 16 is an integrated component and functions as a fan hub on the one hand and as a centrifugal ring on the other. A separate component which merely performs the function of a metallic fan flange is therefore dispensed with.The outer flange ring 16 is designed to replace the conventional centrifugal ring and the steel fan flange and to integrate their functions. The outer flange ring 16 forms an outer peripheral receiving structure 18 for attaching axial fan blades 20, as can be seen particularly in the perspective view of Figure 4.

[0026] The slip ring 10 has a hollow shaft 32 arranged concentrically within the individual slip rings 12 and within the insulating areas 14. The individual slip rings 12 are held in a rotationally fixed manner relative to the hollow shaft 32. The connection between the hollow shaft 32 and the outer flange ring 16 is designed such that the outer flange ring 16 is attached to the hollow shaft 32 at its end. In this case, the hollow shaft 32 projects into a central bore 34 of the outer flange ring 16, and the hollow shaft 32 and the outer flange ring 16 are connected to one another in the axially overlapping area.

[0027] The receiving structure 18 consists of a circumferential sequence of receiving pockets 26 and lateral limiting cams 28. The receiving pockets 26 are each delimited in the axial direction by a radial contact collar 30. The contact collar 30 is designed as part of the outer flange ring. The receiving pockets 26 are bordered on each circumferential side by a limiting cam 28. The opposite side walls 36 of adjacent limiting cams 28 are, viewed in an axial view, tapered towards one another, so that an axial fan blade 20 inserted radially from the outside sits in a receiving funnel 38 and is firmly held. Figures 5a) and 5b) show further details of the slip ring 10, in particular the fastening of the fan blades 20 relative to the outer flange ring 16 or its receiving structure 18.A thrust ring 40 is provided, which corresponds to the contact collar 30 and is held by screw connections 42 relative to the limiting cams 28. In the circumferential direction between screw connections 42, both the contact collar 30 and the thrust ring 40 have bores 44, preferably two each, into which retaining pins 46 of the fan blades 20, projecting in both axial directions, engage. The hold of the fan blades 20 relative to the outer flange ring 16 is ensured by the contact collar 30, the thrust ring 40, and the retaining pins 46. Furthermore, an axially directed overlap 48 can be seen in Figure 5a). The overlap 48 covers the thrust ring 40 radially on the outside and absorbs the centrifugal force of the thrust ring 40 acting during operation, if the thrust ring 40 is of segmented design.

[0028] Figure 6 shows a further perspective axial view of the slip ring 10 with the circumferential thrust ring 40, which is held relative to the outer flange ring 16 by the screw connections 42. In the present case, the thrust ring 40 is designed in three parts, so that each individual part of the thrust ring 40 covers a circumference of 180°. Consequently, in the transition areas between the individual parts of the thrust ring 40, two screw connections 42 are provided directly adjacent to the outer flange ring 16.

[0029] The outer flange ring 16 can be designed as a plastic molded part or as a plastic milled part. The outer flange ring 16 can also be designed as a composite metal-plastic component with a metal core and a plastic coating.

[0030] In a further integrated variant not shown, the insulating region 14 adjacent to the outer flange ring 16 is formed integrally with the outer flange ring 16. List of reference symbols

[0031] 2 slip ring unit

[0032] 4 centrifugal ring

[0033] 5 Fan flange

[0034] 6 brush arrangement

[0035] 8 Radial fan ring

[0036] 10 slip ring

[0037] 12 single slip rings

[0038] 14 isolation areas

[0039] 16 Outer flange ring

[0040] 18 Recording structure

[0041] 20 axial fan blades

[0042] 22 Connection device

[0043] 24 connecting bolts

[0044] 26 Recording pocket

[0045] 28 Limit cam

[0046] 30 Investment Association

[0047] 32 hollow shaft

[0048] 34 Hole

[0049] 36 pages

[0050] 38 receiving hoppers

[0051] 40 pressure ring

[0052] 42 screw connection

[0053] 44 bore

[0054] 46 retaining pins

[0055] 48 Coverage

Claims

Patent claims 1. A slip ring (10) for a slip ring unit (2) of an electric machine with a machine axis of rotation AD, comprising at least one individual slip ring (12), at least two insulating regions (14) and an axially arranged, electrically insulating outer flange ring (16), wherein the at least two insulating regions (14) and the at least one individual slip ring (12) are arranged concentrically with respect to the machine axis of rotation AD and are axially adjacent to one another in an alternating manner, and the outer flange ring (16) is arranged immediately adjacent to one of the insulating regions (14) and forms an axially circumferentially extending receiving structure (18) for fastening axial fan blades (20) acting as a fan hub.

2. Slip ring (10) according to claim 1, characterized in that a connection device (22) is provided which is electrically and mechanically connected to the at least one individual slip ring (12) and has at least one connection bolt (24) projecting axially through the outer flange ring (16).

3. Slip ring (10) according to claim 1 or 2, characterized in that the receiving structure (18) consists of a circumferential sequence of receiving pockets (26) and lateral limiting cams (28).

4. Slip ring (10) according to claim 3, characterized in that the limiting cams (28) are designed as separate inserts of the outer flange ring (16).

5. Slip ring (10) according to claim 3 or 4, characterized in that the receiving pockets (26) are each delimited in the axial direction by a radial contact collar (30).

6. Slip ring (10) according to claim 5, characterized in that axially mutually to the contact collar (30) and circumferential, preferably three-part, pressure ring (40) is provided.

7. Slip ring (10) according to one of claims 1 to 6, characterized in that the outer flange ring (16) is designed as a plastic pressed part or as a plastic milled part.

8. Slip ring (10) according to one of claims 1 to 7, characterized in that the outer flange ring (16) is designed as a composite metal-plastic component with a metal core and a plastic coating.

9. Slip ring (10) according to one of claims 1 to 8, characterized in that the insulating region (14) adjacent to the outer flange ring (16) is formed integrally with the outer flange ring (16).

10. Slip ring (10) according to one of claims 1 to 9, characterized in that a hollow shaft (32) arranged concentrically within the at least one individual slip ring (12) and within the at least two insulating regions (14) is provided and the outer flange ring (16) is attached to the hollow shaft (32) at the end.

11. Slip ring (10) according to claim 10, characterized in that the hollow shaft (32) projects into a central bore (34) of the outer flange ring (16) and the hollow shaft (32) and the outer flange ring (16) are connected to one another in the region overlapping in the axial direction.

12. Slip ring unit (2), in particular for a wind turbine, comprising a slip ring (10) according to one of the preceding claims.

13. Wind turbine comprising a slip ring unit (2) according to claim 12.

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