WO2021233724A1

WO2021233724A1 - Rotor for an electric machine

Info

Publication number: WO2021233724A1
Application number: PCT/EP2021/062391
Authority: WO
Inventors: Martin Schabasser
Original assignee: Voith Patent Gmbh
Priority date: 2020-05-20
Filing date: 2021-05-11
Publication date: 2021-11-25
Also published as: DE102020113625A1; EP4154387A1

Abstract

The invention relates to a rotor for an electric machine, said rotor comprising a rotor axis (9), a rotor hub (6), and poles (7), wherein at least one portion of a pole (7) is connected to the rest of the rotor by means of a claw construction having at least one projection and at least one groove which interlock in a claw-like manner, and wherein the rotor comprises at least one hydraulic fastening element (1) which is positioned and designed to fasten and prestress the claw construction, wherein the hydraulic fastening element (1) comprises a sleeve (2) which encloses a space filled with hydraulic fluid (3), and wherein the hydraulic fastening element (1) comprises a device for fastening and releasing same, wherein the hydraulic fastening element (1) can be fastened by putting the hydraulic fluid (3) under a sufficiently high positive pressure.

Description

Rotor for an electric machine

The invention relates to a rotor for an electrical machine, in particular for a large electrical machine as used in water power plants.

The rotor includes a rotor hub and poles. At least part of a pole (e.g. the pole piece) is connected to the rest of the rotor by means of an arrangement of (usually axially extending) projections and grooves. Often the poles as a whole are also connected to the rotor hub by means of such arrangements.

Such an arrangement of projections and grooves is also referred to as a claw construction, since the projections engage in the associated grooves in a claw-like manner. A distinction is made between rectangular, round and dovetail claws. Constructions with rectangular claws, which are widely used, are also known as hammer head connections. CH 345064 discloses a number of such claw designs. The present invention is not limited to any of the known jaw designs.

Since these claw constructions as such enable an (axial) displacement of the two interconnected parts, which is used for the assembly and disassembly of these parts, they must be secured against such displacement during operation of the electrical machine by means of suitable fastening means. Usually wedges are used for this. The introduction of the wedges results in a pretensioning of the claw connection, so that an axial displacement due to frictional engagement is prevented. The preload also serves to avoid play in the claw connection, since such play can lead to severe damage in the area of the claw connection, especially when the electrical machine is started and stopped frequently. Fastening by means of wedges is disclosed, for example, in documents CH 122159, US 2 308 028, EP 0 866 540 A2, US 3 740 600 and GB 2 022 324 A, the latter document disclosing the use of tubular resilient fastening means. The prestress applied with the known fastening means cannot be dosed in a satisfactory manner, since the forces introduced thereby are limited and cannot really be controlled. The inventor has set himself the task of specifying fastening means that allow a precisely defined pretension.

According to the invention, this object is achieved by an embodiment in accordance with the independent claim. Further advantageous embodiments can be found in the subclaims.

The present invention is explained below with reference to figures. The figures show in detail:

Fig.1 Flydraulic fastening elements in cross section; 2 hydraulic fastening element in longitudinal section - detail;

3 shows an arrangement according to the invention in a first embodiment;

4 shows the arrangement according to the invention in a further embodiment;

5 shows the arrangement according to the invention in a section through the rotor axis; 6 shows the arrangement according to the invention in a further embodiment in a lateral view;

7 shows the arrangement according to FIG. 6 in cross section;

Figure 1 shows a schematic representation of hydraulic fastening elements in cross section, as they are used in the present invention. A hydraulic fastening element, which is denoted by 1, each comprises a shell, which is denoted by 2. The shell 2 encloses a space which is filled with hydraulic fluid. The hydraulic fluid is denoted by 3. The embodiment shown on the left has a circular cross section, and the embodiment shown on the right has a square cross section. Such fastening elements can, however, also have any other cross-section, for example a rectangular cross-section (cf. FIG. 3). Figure 2 shows a hydraulic fastening element 1 in longitudinal section. Here, FIG. 2 shows the end of the hydraulic fastening element 1, which has the device for fastening and releasing the hydraulic fastening element 1. In principle, the opposite end could also have such a device, so that the fastening element 1 can be fastened or released from both ends. As a rule, however, it is sufficient if such a device is only located at one end. At the other end there is then only one wall of the casing 2 that closes the end. The fastening element comprises a piston, which is denoted by 4 and is designed so that it can pressurize the hydraulic fluid 3 enclosed in the casing 2. It is clear that both the shell 2 and the piston 4 must be designed to be correspondingly tight. The sealing of the piston indicated in FIG. 2 can of course also be designed differently. The fastening element 1 further comprises a device for actuating the piston 4, which is designated by 5. A simple and expedient embodiment for this device 5 for actuating the piston 4 consists of a screw and a thread which are designed so that the screw presses the piston 4 into the space filled with hydraulic fluid when it is screwed in. The tightening torque of the screw serves as a measure for the pressure of the hydraulic fluid. Means can also be provided which protect the screw from unintentional loosening (screw locking).

Alternatively, the device 5 for fastening and releasing the hydraulic fastening element 1 could also comprise a valve and a connection for connecting a pressure source. In any case, the fastening element 1 is fastened in that the hydraulic fluid 3 located inside is placed under a sufficiently high overpressure. The release takes place by reducing the overpressure. FIG. 3 shows an arrangement according to the invention in a first embodiment. FIG. 3 shows the connection between a rotor hub, which is labeled 6, and a pole, which is labeled 7. The element labeled 6 could also be a pole body, and the element labeled 7 designated element could also be a pole piece, which is otherwise connected to the rotor hub. In the embodiment shown in Figure 3, the claw connection is designed as a dovetail connection. The projection is connected to the element 7 and the associated groove is located in the element 6. Of course, it could also be the other way around. This also applies to all other connections shown in this application. The connection shown is fastened and pretensioned with a hydraulic fastening element, which is denoted by 1 and is arranged in the groove base. The hydraulic fastening element 1 shown has a rectangular cross section. The cross section could also be designed differently. Appropriate means (for example a groove or projections), which are not shown in FIG. 3, could advantageously be provided for the lateral guidance of the fastening element 1. In the case of a dovetail connection, the two fitting surfaces, which are pressed against one another by the preload and by the centrifugal force during operation of the electrical machine, are arranged at an angle to one another. The dovetail connection shown in FIG. 3 comprises a projection and an associated groove. A plurality of projections and a corresponding number of grooves could also be provided. The projections and grooves are arranged in the axial direction, ie FIG. 3 shows a section perpendicular to the rotor axis. The axial arrangement of the grooves and projections has the advantage that a pole or a pole piece can be expanded in the axial direction. In this way, a pole or pole shoe can be removed without the rotor having to be removed from the stator, which would be very expensive, particularly in the case of large electrical machines such as those used in water power plants. In principle, however, the present invention is not limited to axially aligned projections and grooves, even if such are only rarely used in reality. FIG. 4 shows an arrangement according to the invention in a further embodiment. In the embodiment shown in Figure 4, the claw connection is designed as a double flame head connection. In the case of a flame head connection, the two mating surfaces that are created by the preload and by the Centrifugal force are pressed against each other during operation of the electrical machine, arranged in one plane. In principle, hammer head connections are also conceivable with only one fitting surface located on one side or with two fitting surfaces which are arranged in different parallel planes. However, such modifications are rarely used. In the arrangement shown in FIG. 4, there is an optional spacer element, one of which is denoted by 8, between two fitting surfaces which are pressed against one another by the preload and by the centrifugal force during operation of the electrical machine. By using such spacer elements 8, the connection can be further optimized, since the spacer elements 8 can have a lower internal rigidity or higher elasticity in comparison to the adjoining material.

The arrangement shown in FIG. 4 comprises a total of eight fastening elements, one of which is denoted by 1. Half of the fastening elements 1 are arranged in the bottom of the groove and the other half are each flanking the hammer head projections. The closed dashed lines indicate the force flows introduced by the fastening elements. The fastening elements 1 have a circular cross-section and are guided in corresponding grooves. In this, too, as in all embodiments, the fastening elements 1 could have a different cross section. The embodiments shown in Figures 3 and 4 show only by way of example two of very many different possible embodiments that result from any combination of claw shapes, number of claws, orientation of the claws, number, arrangement and cross-sectional shape of the hydraulic fastening elements and the optional use of spacer elements. Further possible combinations result from the various embodiments of the hydraulic fastening means with regard to the designs which are explained in FIGS. 2 and 5 to 7 and the associated text passages.

FIG. 5 shows an arrangement according to the invention in a section through the rotor axis, which is denoted by 9. Figure 5 is used to different To illustrate possibilities of the arrangement of fastening elements 1. On the right side of FIG. 5 there is a single fastening element between the rotor hub or the pole body 6 and the pole or pole shoe 7. On the left side of FIG. 5 there are two fastening elements between the rotor hub or the pole body 6 and the pole or pole shoe 7. The longitudinal axis of the fastening elements 1 is aligned parallel to the rotor axis 9. In each case one end of the fastening elements 1 protrudes beyond the rotor in the axial direction. The device for fastening and releasing the respective hydraulic fastening element 1 is arranged at this end, ie for example the arrangement according to FIG. 2 or a valve and a connection for a pressure source. The arrangement according to the right-hand side of FIG. 5 is advantageous when the rotor of the electrical machine is only accessible from one axial side. The arrangement according to the left-hand side of FIG. 5, on the other hand, can be used when the rotor is accessible from both axial sides. In this way, shorter fastening elements 1 can be used.

The connections according to the invention are generally implemented as follows: The pole or pole shoe is installed (usually in the axial direction) by pushing the projections into the associated grooves. Then the fasteners are attached to the intended locations. Then the fasteners are activated. This happens either in that the pistons are pressed in according to FIG. 2, or in that the hydraulic fluid in the fastening elements is pressurized by a pressure source. Due to the overpressure of the hydraulic fluid inside the casing, the casing walls of the fastening elements are pressed outwards, whereby the connection is pretensioned. Due to the homogeneously distributing pressure inside the fastening elements, the forces which prestress the connection are also distributed very homogeneously, so that the arrangement according to the invention enables a significant improvement in terms of the prestressing of such a connection.

FIG. 6 shows a modification of the arrangement from FIG. 4. Only the fastening elements from FIG. 4 are shown schematically in a lateral view. the dashed lines indicate the upper or lower end of the rotor. The fastening elements 1 are alternately connected to one another above and below the rotor in such a way that a continuous strand results. The connection is made with pressure lines, ie for example pressure hoses or pressure pipes. These pressure lines are designed in such a way that they can withstand the expected internal pressure without any significant expansion. The strand shown in FIG. 6 thus represents, as it were, the shell of a single fastening element, which in turn is filled with hydraulic fluid. When the hydraulic fluid is pressurized, the axially extending sections each act like a single fastening element as described above. The device for generating the overpressure can be attached anywhere in the line. In this way, the fastening elements in the string have a common means for fastening and loosening. For example, the device shown in FIG. 2 could be arranged at one of the ends of the strand. The other end would then simply be the closed end of the envelope. This end can of course simply terminate axially there with the rotor, so that the arcuate stub shown in FIG. 6 can be omitted there. Another possibility is that both ends of the string include valves. Then the string can be empty during assembly. The filling with hydraulic fluid takes place only after all elements including the connections have been installed. After the overpressure has been applied by means of a pressure source, both valves are then closed. To release the connection, one of the valves is then opened and the escaping hydraulic fluid is collected. FIG. 7 shows the arrangement of FIG. 6 in a section perpendicular to the rotor axis. The connecting lines between the axially extending sections of the fastening elements are shown alternately with solid and dashed lines in order to indicate the corresponding position of the same above or below the rotor. The connecting lines are arranged in such a way that, in this perspective, they are located completely in the area of the pole or pole shoe designated in FIG. 4 with 7. This ensures that the pole or pole shoe can be easily removed in the axial direction. Alternatively, all could Connecting lines can also be arranged completely in the area of the rotor hub or of the pole body 6. Axial expansion is then also possible without any problems.

FIG. 7 shows a pressure sensor which is located on the string of the hydraulic fastening elements and is denoted by 10. With the aid of the pressure sensor 10, the internal pressure of the entire string and thus the holding function of the hydraulic fastening elements contained in the string can be monitored. The measured values recorded by the pressure sensor 10 can be transmitted to the control system of the electrical installation either wirelessly, for example via Bluetooth, or by means of slip rings. Of course, more fastening elements than those shown in FIGS. 6 and 7 can also be integrated in one strand, for example all hydraulic fastening elements built into the rotor. To remove a pole or pole piece, one or two of the connecting lines between the fastening elements must then of course be removed.

List of reference symbols

Hydraulic fastener shell

Hydraulic fluid

Pistons

Device for actuating the piston

Rotor hub / pole body

Pole / pole piece

Spacer element

Rotor axis

Pressure sensor

Claims

1. Rotor for an electrical machine comprising a rotor axis (9), a rotor hub (6) and poles (7), at least part of a pole (7) being connected to the rest of the rotor by means of a claw construction with at least one projection and at least one groove, which intermesh in a claw-like manner, characterized in that the rotor comprises at least one hydraulic fastening element (1) which is arranged and designed such that it can fasten and pretension the claw construction, the hydraulic fastening element (1) having a casing (2) which encloses a space filled with hydraulic fluid (3), and wherein the hydraulic fastening element (1) comprises a device for fastening and loosening the same, wherein the hydraulic fastening element (1) can be fastened in that the hydraulic fluid (3) under a sufficiently high overpressure is set.

2. Rotor according to claim 1, wherein the hydraulic fastening element (1) comprises a piston (4) which is designed so that the same can be pressed into the hydraulic fluid (3) to the hydraulic fluid

(3) to pressurize, and wherein the hydraulic fastener (1) has means (5) for actuating the piston

(4) includes.

3. Rotor according to claim 2, wherein the means (5) for actuating the piston (4) comprises a screw.

4. Rotor according to claim 1, wherein the hydraulic fastening element (1) comprises a valve and a connection for a pressure source.

5. Rotor according to one of the preceding claims, wherein the claw construction comprises mating surfaces which are arranged so that they are pressed against one another by the preload can, and wherein a spacer element (8) is arranged between the mating surfaces.

6. Rotor according to one of the preceding claims, wherein the hydraulic fastening element (1) is arranged in a groove bottom.

7. Rotor according to one of the preceding claims, wherein the hydraulic

Fastening element (1) is arranged flanking a projection.

8. Rotor according to one of the preceding claims, wherein the cross section of the fastening element (1) is circular, square or rectangular.

9. Rotor according to one of the preceding claims, wherein the longitudinal axis of the hydraulic fastening element (1) is aligned parallel to the rotor axis (9), and one end of the hydraulic fastening element (1) projects beyond the rotor in the axial direction, and at this end the Means for attaching and loosening the same is arranged.

10. Rotor according to one of the preceding claims, wherein the rotor is a

A plurality of hydraulic fastening elements (1) comprises, and the ends of the hydraulic fastening elements (1) are connected to one another with pressure lines so that they form a continuous strand.

11. Rotor according to claim 10, wherein the hydraulic fastening elements (1) in the string have a common means for fastening and loosening.

12. Rotor according to claim 10 or 11, wherein the strand comprises a pressure sensor (10) which is designed so that with the same of

Internal pressure of the strand can be monitored.