Rotor for externally excited synchronous machine

Abstract

The present invention relates to a rotor (1) for an externally excited synchronous machine (2), comprising a rotor winding (4) arranged on a hollow rotor shaft (3). Essential to the present invention is that a rotary transformer rotor (7) is arranged on a hollow rotor shaft (3), comprising a secondary winding (8) and a ferrite core (9) at least partially surrounding the secondary winding (8), and the ferrite core (9) has at least two separate ring segments (10) arranged between and penetrating ring segments (10) in the circumferential direction (27), and at least two ring segments (10) are supported on the rotor shaft (3).

Description

Technical Field

[0001] The present invention relates to a rotor for a separately excited synchronous machine as described in the generic concept of claim 1. The present invention further relates to a separately excited synchronous machine equipped with such a rotor, a traction motor or a servo motor for an automobile.

[0002] From German Patent Application Publication No. 102020207000, a rotor as described in the generic concept for a separately excited synchronous machine with rotor windings arranged in a hollow rotor shaft is known. The energy transmission system is arranged on the rotor such that the excitation rotor (secondary winding) is fixedly coupled to the rotor shaft. The excitation stator (primary winding) is arranged inside the excitation rotor.

[0003] From German Patent Application Publication No. 102020206998, a method for increasing the efficiency of an energy transmission device in which energy is wirelessly transmitted using a magnetic field is known.

[0004] From U.S. Patent No. 7230363 and U.S. Patent No. 11286848, another rotor is known.

[0005] For a so-called separately excited synchronous machine, a direct current is required in its rotor to generate a magnetic rotor magnetic field. This process is called "rotor excitation". Wear-free transmission of the direct current is preferably carried out inductively, i.e., wirelessly. The basic functional mode of the above-mentioned inductive energy transmission is based on a transformer. In this case, the primary winding of the transformer is fixedly arranged on the synchronous machine, and the secondary winding is arranged on the rotating rotor.

[0006] In particular, the secondary winding in the hollow rotor shaft for realizing a rotating transformer rotor is surrounded by a ring-shaped ferrite core to attenuate high-frequency electromagnetic interference signals. Due to such a ring-shaped ferrite core, the efficiency is increased due to its high magnetic conductivity.

[0007] However, a drawback of such ring-shaped ferrite cores in rotating components is that, because ferrite is a relatively brittle material, large tensile stresses can be generated in the ferrite core, particularly due to the centrifugal force generated during rotation. These tensile stresses can, in some cases, cause the ferrite core to rupture, and ultimately damage the rotor.

[0008] Therefore, the present invention addresses the challenge of providing an improved embodiment, or at least one alternative embodiment, for the type of rotor described in the broader concept, that overcomes the shortcomings known from the prior art in particular.

[0009] This problem is solved by the present invention as described in independent claim 1. Advantageous embodiments are described in the dependent claims.

[0010] The present invention is based on the general idea that a ferrite core, which is conventionally closed in a ring shape in the circumferential direction and subjected to large tensile stress due to centrifugal force during rotation, can be segmented, i.e., divided into ring segments, and these ring segments are supported on the inner circumferential surface of a hollow rotor shaft, particularly surface-wise, thereby avoiding the tensile stress in the ferrite core that was conventionally caused by centrifugal force due to the closed ring shape. Theoretically, axial segmentation of the ferrite core is also possible, which offers advantages in manufacturing. However, in this case, the axial segments must remain in contact with each other in order to maintain magnetic flux. By segmenting the originally closed ring-shaped ferrite core, the ferrite core has at least two, preferably four or more, ring segments that are not bonded to each other, each supported on the inner surface of the rotor shaft, and thus no longer subjected to circumferential tensile force. The rotor according to the present invention for a separately excited synchronous machine has the hollow rotor shaft described above, on which the rotor windings are arranged. A rotating transformer rotor is arranged on a hollow rotor shaft, comprising a secondary winding and a ferrite core that at least partially surrounds the secondary winding. According to the present invention, this ferrite core has at least two separate ring segments arranged between and penetrating ring segments in the circumferential direction, with at least two gaps between them, and the at least two ring segments are separately supported on the rotor shaft. This completely avoids the tensile stress caused by centrifugal force due to a conventionally closed ring-shaped ferrite core. This is a significant advantage, especially since the ferrite core itself is formed from a brittle material, and its failure due to tensile stress is unpredictable or extremely difficult to predict.By segmenting the ferrite core into at least two separate ring segments, the originally ring-shaped core is interrupted circumferentially, so that while centrifugal force certainly acts on the individual ring segments when the rotor is rotating, these ring segments can be supported by their outer circumferential surfaces, for example, on the inner circumferential surface of a hollow rotor shaft, in which case no tensile stress acts on this inner circumferential surface. Only the centrifugal force-induced pressing force that presses the individual ring segments against the inner circumferential surface of the hollow rotor shaft must be absorbed, which is considerably easier for the ring segments than absorbing tensile stress. The rotor constructed according to the present invention can increase the absolute load level, and at least indirectly, its durability.

[0011] In another preferred embodiment of the solution according to the present invention, the ferrite core has four separated ring segments having four gaps arranged between and penetrating the ring segments in the circumferential direction. The four ring segments form a ring interrupted by gaps in the circumferential direction, and the gaps extend parallel to the axis of the ferrite core formed by the four separated ring segments. Dividing the ferrite core into four separated ring segments can further reduce the centrifugal force acting on the ring segments, because each of the four separated ring segments, when observed in itself, weighs less than, for example, a ferrite core formed from only two separated ring segments.

[0012] In another advantageous embodiment of the rotor according to the present invention, at least one ring segment has a sheath and at least one end face that surrounds the secondary windings at the longitudinal end and faces inward. Naturally, there may be two such end faces, one opposite to the other and facing inward, so that the secondary windings are surrounded by the sheath radially outward and by the two end faces that are opposite to each other axially. The ring segment thus formed simultaneously forms a retaining portion for the individual windings of the secondary windings. The end face positioned at the longitudinal end can further reduce, and preferably even block, undesirable electromagnetic radiation through the axial end face.

[0013] In one particularly preferred embodiment of the rotor according to the present invention, two conductors for the electrical contact connection of the secondary windings are guided through gaps in the ferrite core, particularly two gaps located opposite each other. This allows the gaps in the ferrite core to be utilized to guide the conductors, thereby guiding the conductors radially outward between two adjacent ring segments of the ferrite core, thereby reducing the axial and radial installation space.

[0014] In another advantageous embodiment of the rotor according to the present invention, at least one gap between two adjacent ring segments forms a cooling passage for a cooling fluid. In addition to preventing circumferential tensile forces, the gaps positioned between each pair of adjacent ring segments further allow the cooling fluid to pass through these gaps, which offers the significant advantage of achieving significantly improved cooling of the rotor. This improved cooling of the rotor also improves the output of an electromechanical device equipped with such a rotor, such as a separately excited synchronous machine, at least indirectly.

[0015] The rotor shaft is advantageously provided with housings formed complementary to the outer contours of the ring segments, and the ring segments are preferably supported surfacely by their outer contours, i.e., their outer circumferential surfaces, within the housings. This allows for surface, and therefore uniform, support of each ring segment within the housings of the rotor shaft, thereby enabling significantly higher rotational speeds. This is because uniform support reduces the load on each individual ring segment.

[0016] The present invention further relates to the general idea of ​​equipping a separately excited synchronous machine with a rotor, corresponding to the previous paragraph, and simultaneously providing a fixed bearing pin on which the primary winding of a rotating transstator is located, and pressing the hollow rotor shaft of the rotor, equipped with a rotating transrotor, into this bearing pin. In this way, the rotating transstator engages with the hollow rotor shaft, and the primary winding is located within the secondary winding. A major advantage of such a separately excited synchronous machine with a rotor according to the present invention is that the ferrite core of the secondary winding is still subjected to compressive stress, for example, solely due to centrifugal force, but no longer subjected to tensile stress, thereby allowing the rotor to withstand significantly higher rotational speeds.

[0017] In another advantageous embodiment of a separately excited synchronous machine, a rectifier is provided that is electrically connected to the secondary winding and axially adjacent to the secondary winding, and is located on the rotor outside the rotor shaft. This rectifier is preferably located within a balancing plate and / or within a cover, thereby enabling an optimized and protected arrangement of the rectifier, particularly in terms of installation space. Purely theoretically, an arrangement arranged radially vertically is also conceivable.

[0018] The balancing plate may also have openings, which are positioned to allow cooling fluid to be sprayed onto the endwinding located on the longitudinal end of the rotor winding. This enables improved cooling of the rotor, and indirectly, cooling of the separately excited synchronous machine, thereby enabling even higher power output. However, the openings in the balancing plate not only allow for spraying onto the endwinding, but also significantly improve the cooling of the rectifier located inside the balancing plate and / or under the cover, or generally the electronic components located therein. Of course, it is also possible to spray the cooling medium directly onto the rectifier, i.e., without openings.

[0019] In one particularly preferred embodiment of a separately excited synchronous machine, bearings for supporting the rotor are located radially inward of the balancing plate and / or cover, on bearing pins. In this case, the rotor is supported via the balancing plate and / or cover, and a support ring may be provided between the balancing plate and / or cover and the bearing, which may be configured as a ball bearing or a roller bearing.

[0020] Another important feature and advantage of the present invention will become apparent from the dependent claims, from the drawings, and from the relevant descriptions of the drawings.

[0021] Naturally, the features described above and those further described below can be used in other combinations or individually, not just in the combinations described, without departing from the scope of the present invention. The components described above and those further described below, each separately, of a higher-level unit, such as a mechanism, device, or assembly, may constitute separate components or parts of the unit, or an integrated region or section of the unit, even if shown differently in the drawings.

[0022] Preferred embodiments of the present invention are shown in the drawings and will be described in more detail in the following description. [Brief explanation of the drawing]

[0023] [Figure 1] This diagram schematically shows a secondary winding for incorporation into the rotor shaft of a rotor according to the present invention, which has a ferrite core having four separated ring segments arranged between the ring segments in the circumferential direction and having four gaps through which they pass. [Figure 2] This is a schematic diagram showing the rotor according to the present invention. [Figure 3] This is a schematic cross-sectional view of the rotor according to the present invention. [Figure 4] This figure provides a schematic overview of the details of Figure 3.

[0024] Corresponding to Figures 2 to 4, a rotor 1 according to the present invention for an externally excited synchronous machine 2, which is not further illustrated in other respects, has a hollow rotor shaft 3 on which rotor windings 4 are arranged. The rotor windings 4 have end windings 5 ​​on the longitudinal end side as is known. The rotor windings 4 generally extend through a laminate 6 used as a winding support. A rotary transformer rotor 7 (see Figure 1) is arranged on the hollow rotor shaft 3, which has secondary windings 8 and a ferrite core 9 that at least partially surrounds the secondary windings 8.

[0025] According to the present invention, this ferrite core 9 has at least two, indeed four according to FIG. 1, ring segments 10, which have at least two, here four gaps 11 arranged between and penetrating through the ring segments 10 in the circumferential direction. At least two of the ring segments 10 are supported by the rotor shaft 3. The gaps 11 extend axially with respect to the axis 12 of the rotor 1. As can be further seen corresponding to FIG. 1, the individual ring segments 10 do not contact each other in the circumferential direction. Thus, in this embodiment, compared with a ferrite core that was conventionally closed in a ring shape, during operation of the rotor 1, that is, during rotation of the rotor 1, tensile stress caused by centrifugal force does not occur. Theoretically, it is also possible to segment the ferrite core 9 axially into at least two axial segments 28a, 28b, which provides advantages in manufacturing. However, in this case, in order to maintain the magnetic flux, the individual axial segments 28a, 28b would have to remain in contact with each other.

[0026] The ferrite core 9, or the individual ring segments 10 of the ferrite core 9, are made of a hard but extremely brittle material, which is at risk of crumbling and is particularly difficult or impossible to design with respect to the tensile stress that occurs. In contrast, compressive stress can be absorbed much better by the ferrite core 9. By dividing a conventionally circumferentially closed ring-shaped ferrite core into individual ring segments 10 according to the present invention, the tensile stress load on the ferrite core 9 can be significantly reduced or even completely avoided. This is because during rotation of the rotor 1, the individual ring segments 10 only receive a pressing force due to centrifugal force, and due to this pressing force, the individual ring segments 10 are pressed against the corresponding receiving portions 13 of the hollow rotor shaft 3 (see FIGS. 3 and 4).

[0027] At least one of the ring segments 10 has a jacket part 14 and at least one end face 15 that surrounds the secondary winding 8 on the longitudinal end side and faces inward, whereby support by shape connection of the secondary winding 8 in the ring segment 10 becomes possible.

[0028] When observing the ferrite core 9 corresponding to FIGS. 1 and 4, it can be identified that the ring segment 10 shown in FIGS. 1 and 4 has only an end face 15 that surrounds the secondary winding 8 on the longitudinal end side and faces inward, whereas a ring disk 16 is arranged on the end face located on the opposite side. This ring disk 16 may be closed in the circumferential direction and may likewise be supported in the receiving part 13 in the hollow rotor shaft 3 by an outer covering, whereby the tensile force caused by centrifugal force is reduced. By the ring disk 16, axial holding of the secondary winding 8 becomes possible.

[0029] When further observing FIG. 1, it can be identified that two conductors 17 for electrical contact connection of the secondary winding 8 are led through two gaps 11 located on opposite sides of the ferrite core 9. The two conductors 17 of the secondary winding 8 each proceed radially outward through the corresponding gap 11 and then change their direction axially. The rotor shaft 3 may further be provided with two openings 18 for drawing in the two conductors 17 of the secondary winding 8, and through the openings 18, the secondary winding 8 is electrically contact-connected to, for example, a rectifier 19. The rectifier 19 may be arranged, for example, axially adjacent to the secondary winding 8 and on the rotor 1 outside the rotor shaft 3, and in particular, the arrangement of the rectifier 19 may be carried out within the balancing plate 20 and / or the cover 21. The rectifier 19 is covered by the cover 21 (see FIGS. 2 to 4), and the cover 21 is simultaneously used as a cooling surface for cooling the rectifier 19 or another electronic component arranged under the cover 21.

[0030] The rotor 1 described above can be placed in an externally excited synchronous machine 2, which further has a fixed bearing pin 22 on which the primary winding 23 of the rotating transstator 24 is placed, and the bearing pin 22 engages with the secondary winding 8 together with the primary winding 23.

[0031] On the radially inward side of the balancing plate 20 or cover 21, a bearing 25 for supporting the rotor 1 or rotor shaft 3 is positioned on a bearing pin 22.

[0032] The ballast plate 20 further has an opening 26 through which cooling fluid can be sprayed onto the end winding 5 of the rotor winding 4, thereby cooling the rotor winding 4. Naturally, the cover 21 can also have such an opening 26a, so that the cooling fluid can reach the inside of the cover 21 through the opening 26a and cool electronic components located there, such as a rectifier 19.

[0033] Overall, the rotor 1 and synchronous machine 2 according to the present invention significantly reduce the risk of damaging the ferrite core 9. This is because, in particular, the segmentation of the ferrite core 9 makes it possible to minimize or eliminate the tensile load caused by centrifugal force in the ferrite core 9, because the divided ring segments 10 of the ferrite core 9 are now preferably arranged planarly in the housing portion 13 of the hollow rotor shaft 3, and are preferably subjected exclusively to compressive loads in the housing portion 13. Furthermore, the gap 11 located between two circumferentially adjacent ring segments 10 allows for improved cooling when the gap 11 is used as a cooling passage for the cooling fluid.

Claims

1. In a rotor (1) for a separately excited synchronous machine (2), which is equipped with rotor windings (4) arranged on a hollow rotor shaft (3), A rotary transformer rotor (7) is arranged on the hollow rotor shaft (3), and the rotor rotor (7) is equipped with a secondary winding (8) and a ferrite core (9) that at least partially surrounds the secondary winding (8). The rotor (1) is characterized in that the ferrite core (9) has at least two separate ring segments (10), each ring segment (10) having at least two gaps (11) arranged between and penetrating the ring segments (10) in the circumferential direction (27), and at least two of the ring segments (10) are supported by the rotor shaft (3).

2. The rotor according to claim 1, characterized in that the ferrite core (9) has four separate ring segments (10) arranged between the ring segments (10) in the circumferential direction and having four gaps (11) through which they penetrate.

3. The rotor according to claim 1 or 2, characterized in that at least one ring segment (10) has an outer sheath (14) and at least one end face (15) that surrounds the secondary winding (8) at its longitudinal end and faces inward.

4. The rotor according to any one of claims 1 to 3, characterized in that two conductors (17) for electrical contact connection of the secondary winding (8) are led through two gaps (11) located on opposite sides of the ferrite core (9).

5. The rotor according to claim 4, characterized in that the rotor shaft (3) has two openings (18) for drawing in the two conductors (17) of the secondary winding (8).

6. The rotor according to any one of claims 1 to 5, characterized in that a cooling passage for a cooling fluid is formed by at least one gap (11) between two adjacent ring segments (10).

7. The rotor according to any one of claims 1 to 6, characterized in that a housing portion (13) formed complementary to the outer contour of the ring segment (10) is arranged on the hollow rotor shaft (3), and the ring segment (10) is supported by the housing portion (13) in a planar manner by its outer contour.

8. A separately excited synchronous machine (2) or a traction motor or servo motor for an automobile, comprising a rotor (1) according to any one of claims 1 to 7, and a fixed bearing pin (22) having a primary winding (23) of a rotating transformer stator (24) that engages with the secondary winding (8) and is positioned on the bearing pin (22).

9. The separately excited synchronous machine (2) or traction motor or servo motor for an automobile according to claim 8, characterized in that a rectifier (19) is provided which is electrically connected to the secondary winding (8) and is adjacent to the secondary winding (8) in the axial direction, and is located on the rotor (1) outside the rotor shaft (3).

10. The separately excited synchronous motor (2) or traction motor or servo motor for an automobile according to claim 8 or 9, characterized in that the rectifier (19) is located within a balancing plate (20) and / or cover (21).

11. The separately excited synchronous machine (2) or traction motor or servo motor for an automobile according to claim 10, characterized in that an end winding (5) is arranged on the longitudinal end side of the rotor winding (4), and the ballasting plate (20) has an opening (26) for blowing cooling fluid onto the end winding (5).

12. A separately excited synchronous machine (2) or a traction motor or servo motor for an automobile according to claim 10 or 11, characterized in that a bearing (25) for supporting the rotor shaft (3) on the bearing pin (22) is disposed radially inward of the ballast plate (20) and / or the cover (21).

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