Rotor of an electrical machine

Abstract

The present invention relates to a rotor (1) of an electrical machine (10) comprising a rotor body (2) extending around a rotor axis (100), in particular a rotor core, with a plurality of salient poles (4), wherein a rotor slot (5) is formed between each adjacent salient pole (4), an excitation winding (6a) comprising a plurality of excitation coils (6), each enclosing a pole shaft (4a) of one of the salient poles (4), and a rotor sleeve (7) surrounding the rotor body (2) with respect to a circumferential direction (300) around the rotor axis (100), characterized in that at least one prestress transmission element (8) is provided in at least one of the rotor slots (5), which is arranged in the radial direction (200) between the rotor sleeve (7) and the excitation winding (6a) and is designed to transmit a mechanical prestress of the rotor sleeve (7) to the excitation winding (6a).

Description

Prior ArtThe present invention relates to a rotor of an electric machine. The invention also relates to an electric machine having such a rotor. The rotor has a prestressed field winding.Electrical machines are known from the prior art, which have a rotor with an exciter winding. To avoid air turbulence, it is known to use rotor sleeves. For example, DE 10 2020 130 123 A1 discloses an electric machine having a rotor, wherein the rotor has a rotor sleeve. The rotor sleeve is arranged on the rotor side of the air gap and covers, at least in the circumferential direction, given distances between the salient poles with respect to the air gap, i.e. toward the air gap. This helps, in particular at relatively high rotational speeds, to avoid turbulences of a medium present in the air gap-typically the air flowing around the rotor in the air gap-during rotation of the rotor.Disclosure of the InventionThe rotor according to the invention allows the rotor winding to be prestressed by a rotor sleeve. On the one hand, this prevents the rotor winding from slipping off during operation of the rotor, and on the other hand, high slot fill factors are made possible.The rotor for an electric machine has a rotor body which extends about a rotor axis and has a plurality of salient poles. A rotor groove is formed between adjacent salient poles. The rotor body is preferably a laminated rotor core.The rotor also has an exciter winding. This comprises a plurality of excitation coils, each of which surrounds a pole shaft of one of the salient poles. Furthermore, the rotor has a rotor sleeve which surrounds the rotor body about the rotor axis with respect to a circumferential direction.At least one prestress transmission element is provided in at least one of the rotor grooves. The prestress transmission element is arranged in the radial direction between the rotor sleeve and the exciter winding and is also designed to transmit a mechanical prestress of the rotor sleeve to the exciter winding. In this way, in particular a radial prestressing force can be applied to the exciter winding.The dependent claims show preferred developments of the invention.The salient poles are preferably formed without pole shoes. This enables the excitation coils to be radially plugged onto the pole shafts. The excitation coils can thus be wound in advance and can be plugged onto the pole shafts in the wound state. This simplifies the production of the excitation coils. For this purpose, it is made possible for exciting coils which are plugged onto adjacent pole shafts to have only a minimum gap with respect to one another, as a result of which a groove fill factor is maximized. The groove fill factor is preferably above 54%, preferably above 60%. In particular, groove fill factors of up to about 67% are made possible. It is also provided that the prestress transmission element is a separate insert part. The biasing transmission member extends in the axial direction of the rotor groove. The prestressing transmission element can preferably be inserted into the rotor groove after the excitation windings have been plugged onto the pole shafts.The respective prestress transmission element preferably protrudes from the rotor body in the axial direction. This ensures in particular that the prestress by the rotor sleeve is transmitted by the prestress transmission element along the entire axial dimension of the rotor groove. Furthermore, it is preferably provided that the prestress transmission element is surrounded by the rotor sleeve. The rotor sleeve completely surrounds the prestress-transfer element in the circumferential direction.Thus, smooth transmission of the biasing force from the rotor sleeve to the biasing transmission member is achieved.Particularly advantageously, the respective prestress transmission element extends beyond the salient poles of the respective rotor groove in the radial direction. It is thereby possible for the rotor sleeve to press against the prestressing transmission element. This leads in particular to the transmission of a prestressing force from the rotor sleeve via the respective prestressing transmission elements to the exciter winding. In this way, a reliable prestressing of the exciter winding can be realized.It is preferably also provided that the respective prestress transmission element is positively fastened or anchored at its ends in the circumferential direction to the salient poles of the respective rotor groove. This is achieved in particular by the prestressing transmission element being clamped in the circumferential direction between the salient poles of the respective rotor groove. Thereby, the biasing transmission member is fixedly disposed within the rotor groove. Moving out of the prestressing transmission element is made more difficult or prevented, in particular even at high rotational speeds of the rotor. This in particular relieves the rotor sleeve which does not have to absorb the entire centrifugal forces emanating from the prestressing transmission elements.The respective prestressing transmission element has, in particular, lamellae which are embedded in a matrix. The lamellae are preferably stamped. The matrix is preferably made of plastic. As a result, in particular the prestress transmission element has a low electrical conductivity and is simple and cost-effective to produce and is of stable design.In a further preferred embodiment, salient poles have pole shoes. The pole shoes project with two pole collars into the two adjacent rotor grooves. It is provided that the pole collars of the pole shoes can each be bent plastically about an axis at the base of the respective pole collar, whereby a plugging of the respective excitation coil onto the respective salient pole is made possible. Particularly advantageously, the pole collars can be bent plastically in such a way that they are oriented aligned with the pole shafts in the radial direction. This makes it possible to plug on the excitation windings in a simple manner, analogous to the case in which no pole shoes were present. The pole collars of the same rotor groove form the bias transmission elements, respectively. In particular, the pole collars can be bent back after the excitation windings have been plugged on, in order to extend in particular perpendicularly or in the circumferential direction from the respective pole shank. The pole collars allow a transmission of force from the rotor sleeve to the exciter winding, whereby the exciter winding can be prestressed.The pole collars particularly preferably each have at least one weakening at their bases. The weakening serves to reduce the bending resistance, so that the pole collars are easily plastically deformable, in particular for plugging on the winding. The weakening is preferably formed by a recess or indentation. This makes it possible to deform the pole collars and thus to mount the exciter windings in a simple and low-complexity manner.The respective bias transmission element is preferably designed to be magnetically and / or electrically insulating. Alternatively, it is preferably provided that the bias transmission element has no or a partial magnetic conductivity. Thus, in particular, a risk of a magnetic or electrical short circuit between two salient poles is avoided or reduced. An influence on the magnetic fluxes of the rotor and / or the electric machine is also minimized.Preferably, an air gap remains within a rotor groove between two coil sides of two excitation coils. The air gap is in particular formed as a cooling channel. For example, in the case of a dip-impregnated winding, the gap serves as an axial cooling channel for increasing the continuous power. In particular, the cooling medium is introduced via a shaft and a flow-connected rotor sheet section or a flow-connected balancing disk.Each excitation coil is advantageously fully or at least partially impregnated with an impregnating material. The impregnating material is in particular resin. Alternatively or additionally, each rotor groove is cast with a casting material, in particular with resin. This in particular increases the mechanical stability of the rotor and improves the thermal properties of the rotor.The rotor sleeve preferably has a wall thickness of at least 0.5 mm, preferably at least 0.6 mm and at most 1.5 mm, preferably 1.4 mm. This leads to an optimum prestress which can be applied from the rotor sleeve to the exciter winding.The prestressing force of the rotor sleeve leads in particular to a pressure which is applied to the excitation coils which is at least 1000 MPA, preferably at least 1200 MPA, and / or at most 3000 MPA, preferably at most 1600 MPA.A pole number is preferably in the range between 6 and 16. By preparing the excitation coils separately and biasing the excitation coils, on the other hand, high slot fill factors can be achieved even with high numbers of poles.Preferably, the respective prestressing transmission element is of slot-wedge-shaped design. Alternatively or additionally, the respective prestress transmission element is of circular section-shaped or arcuate configuration in cross section.The invention also relates to an electric machine, which is in particular a salient pole machine. The electric machine has a stator and a rotor which can be driven by the stator, as described above.Brief Description of the DrawingsHereinafter, embodiments of the invention will be described in detail with reference to the accompanying drawings. In the drawing, the following is: FIG. 1 shows a schematic illustration of a salient pole machine according to an exemplary embodiment of the invention, FIGS. 2 to 5 are schematic diagrams of different steps in the production of a rotor according to a first exemplary embodiment of the invention, FIG. 6 shows a schematic detailed view of the rotor according to the first exemplary embodiment of the invention, FIGS. 7 to 9 are schematic diagrams of different steps in the production of a rotor according to a second exemplary embodiment of the invention; and FIG. 10 is a schematic illustration of a rotor according to a third exemplary embodiment of the invention.Embodiments of the InventionAll the same components, elements and / or units are preferably provided with the same reference numerals in all the figures.FIG. 1 shows a schematic view of an electric machine 11 which is designed as a salient pole machine. The electric machine 11 has a stator 12 and a rotor 1 that can be driven by the stator 12.The rotor 1 has a rotor body 2 extending about a rotor axis 100 and having a plurality of salient poles 4. The rotor body 2 is in particular a laminated rotor core. Between adjacent salient poles 4 a rotor groove 5 is formed. Each pole shaft 4a of one of the salient poles is surrounded by an exciting coil 6. The rotor 1 has an excitation winding 6a which includes all these excitation coils.In addition, a rotor sleeve 7 is provided which surrounds the rotor body 2 about the rotor axis 100 with respect to a circumferential direction 300. The rotor sleeve 7 preferably has a wall thickness of at least 0.5 mm, preferably at least 0.6 mm and at most 1.5 mm, preferably 1.4 mm.In the rotor grooves 5, at least one prestress transmission element 8 is provided, which is arranged between the rotor sleeve 7 and the field winding 6 ain the radial direction 200. The prestress transmission element 8 is designed to transmit a mechanical prestress of the rotor sleeve 7 to the field winding 6 a. Various variants of the bias transmission member 8 will be described below.The production of a first variant is illustrated in FIGS. 2 to 5, each figure showing a different point in time during production.FIG. 2 shows the rotor body 2 of the rotor 1, and the salient poles 4 are formed without pole shoes, which allows the exciting coils 6 to be radially inserted onto the pole shafts 4a. As shown in FIG. 1, each field winding may be wound on a tool 14 in advance. A single tooth winding thus takes place. By winding outside the rotor slot 5, optimum excitation windings 6a can be prepared and high slot fill levels can be achieved. FIG. 3 shows schematically the sliding-on of an excitation coil 6; FIG. 4 shows a state in which all salient poles 4 are provided with an excitation coil 6.In each rotor groove 5, a biasing transmission member 8 is provided as a separate insert. The biasing transmission members 8 extend in the axial direction of the rotor groove 5, i.e., along the rotor axis 100. The respective prestress transmission element 8 protrudes in the radial direction 200 beyond the salient poles 4 of the respective rotor groove 5.As shown in FIG. 5, a rotor sleeve 7 is attached. The rotor sleeve 7 applies a biasing force to the biasing transmission members 8, and the biasing transmission members 8 transmit the biasing force to the respective portions of the exciting coils 6 in the respective rotor groove 5. The prestressing of the exciter winding 6a in the radial direction 200 is thus achieved.The biasing transmission elements 8 protrude from the rotor body 2 in the axial direction. In the circumferential direction 300 about the rotor axis 100, the prestressing transmission elements 8 are surrounded by that of the rotor sleeve 7. In this way, the prestressing of the rotor sleeve 7 is uniformly applied to the field winding 6a by means of the prestressing transmission elements 8. In particular, the transfer of the prestress takes place over an entire axial length of the rotor body 2.FIG. 6 shows a schematic detailed view of the rotor 1 according to the first exemplary embodiment. It is provided in particular that the respective prestress transmission element 8 is positively fastened or anchored at its ends to the salient poles 4 of the respective rotor groove 5 in the circumferential direction 300. This is effected in particular by each prestressing transmission element 8 being clamped in the circumferential direction 300 between the salient poles 4 of the respective rotor groove 5.It is also provided that an air gap 10 remains within a rotor groove 5 between two coil sides of two excitation coils 6. This air gap 10 serves in particular as an immersion-impregnated winding as an axial cooling channel for increasing the continuous power. For this purpose, the cooling medium is introduced via a shaft and a flow-connected rotor sheet section or a rotor-driven balancing disk.FIGS. 7 to 9 schematically show different states during the production of the rotor 1 according to a second variant. In this case, the salient poles 4 have pole shoes, which each project with two pole collars 9 into the two adjacent rotor grooves 5. FIG. 7 shows such a diagram,The excitation coils 6 are again prefabricated as separate components, for example by winding on a tool 14. This allows the respective excitation coil 6 to be plugged onto the respective salient pole 4, in particular pole shaft 4 a. By bending, it is possible in particular to orient the pole collars 9 in alignment with the pole shafts 4 ain the radial direction 200. After the excitation coil 6 has been plugged on, the pole collars 9 can be bent back. It is provided that the pole collars 9 of the same rotor groove 5 respectively form the prestressing transmission elements 8.FIG. 8 shows the pole collars 7 in a bent state, wherein the excitation coils 6 are applied to all salient poles 4. The pole collars 9 are subsequently bent back and are surrounded at least partially in the circumferential direction 300 by a rotor sleeve 7. This state is shown in FIG. 9.The pole collars 9 each have at least one weakening 9 aat their bases. This weakening has in particular a recess or indentation for reducing the bending resistance. The respective bias transmission element 8 is designed to be magnetically and / or electrically insulating or is partially magnetically conductive.FIG. 10 schematically shows an illustration of a rotor 1 according to a third variant. In this variant, the salient poles 4 are formed without pole shoes, so that the excitation windings 6 can be applied to the pole shafts 4 ain a manner analogous to the first variant. It is provided that the respective prestress transmission element 8 has stamped, lamellae 9 b, which are embedded in a matrix, in particular made of plastic. In particular, the prestressing transmission elements 8 form loose pole collars which cooperate with the salient poles 4 in a pole shoe-like manner.In all variants, the excitation coils 6 are fully or at least partially impregnated with an impregnating material. The impregnating material is preferably resin. Alternatively or additionally, each rotor groove 5 is preferably cast with a casting material. The potting material is also in particular resin. This improves the stability, aerodynamics and temperature behavior of the rotor 1.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2020 130 123 A1

[0002]

Claims

Rotor (1) of an electric machine (10), having - a rotor body (2) extending about a rotor axis (100), in particular a laminated rotor stack, having a plurality of salient poles (4), wherein in each case a rotor groove (5) is formed between adjacent salient poles (4), - an excitation winding (6a) comprising a plurality of excitation coils (6) which in each case enclose a pole shaft (4a) of one of the salient poles (4), and - a rotor sleeve (7) which surrounds the rotor body (2) about the rotor axis (100) with respect to a circumferential direction (300), characterized in that - at least one prestress transmission element (8) is provided in at least one of the rotor grooves (5), which is arranged in the radial direction (200) between the rotor sleeve (7) and the exciter winding (6a) and is designed to transmit a mechanical prestress of the rotor sleeve (7) to the exciter winding (6a).Rotor (1) according to Claim 1, characterized in that the salient poles (4) are designed without pole shoes for radially plugging the excitation coils (6) onto the pole shafts (4a), and the prestressing transmission element (8) is a separate insert part which extends in the axial direction of the rotor groove (5).Rotor (1) according to Claim 2, characterized in that the respective prestressing transmission element (8) projects from the rotor body (2) in the axial direction and is surrounded by the rotor sleeve (7).Rotor (1) according to one of Claims 2 to 3, characterized in that the respective prestressing transmission element (8) extends beyond the salient poles (4) of the respective rotor groove (5) in the radial direction (200).Rotor (1) according to one of Claims 2 to 4, characterized in that the respective prestressing transmission element (8) is fastened or anchored in a positive-locking manner at its ends to the salient poles (4) of the respective rotor groove (5) in the circumferential direction (300), in particular is clamped between the salient poles (4) of the respective rotor groove (5) in the circumferential direction (300).Rotor (1) according to one of Claims 2 to 5, characterized in that the respective prestressing transmission element (8), in particular stamped, has lamellae (9b), which are embedded in a matrix, in particular made of plastic.Rotor (1) according to Claim 1, characterized in that the salient poles (4) have pole shoes which project in each case with two pole collars (9) into the two adjacent rotor slots (5), the pole collars (9) of the pole shoes being capable of being bent plastically in each case about an axis at the base of the respective pole collar (9) in order to plug the respective excitation coil (6) onto the respective salient pole (4), in particular in order to be oriented so as to be aligned with the pole shafts (4a) in the radial direction (200), the pole collars (9) of the same rotor slot (5) in each case forming the prestressing transmission elements (8).Rotor (1) according to Claim 7, characterized in that the pole collars (9) each have at least one weakening (9a), in particular a recess or indentation, at their foot for reducing the bending resistance.Rotor (1) according to one of the preceding claims, characterized in that the respective bias transmission element (8) is designed to be magnetically and / or electrically insulating or is partially magnetically conductive.Rotor (1) according to one of the preceding claims, characterized in that an air gap (10) remains within a rotor groove (5) between two coil sides of two excitation coils (6), which air gap is formed in particular as a cooling duct.Rotor (1) according to one of the preceding claims, characterized in that each excitation coil (6) is impregnated wholly or at least partly with an impregnating material, in particular with resin, and / or each rotor groove (5) is encapsulated with a potting material, in particular with resin.Electric machine (11), in particular salient pole machine, having a stator (12) and a rotor (1) according to one of the preceding claims, which can be driven by the stator (12).

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