Rotor for a separately excited synchronous machine, separately excited synchronous machine and motor vehicle

Abstract

The invention relates to a rotor (10) for a separately excited synchronous machine, comprising a base body (12) with several pole shoes (16) distributed evenly around the circumference, each having an excitation winding (18), wherein the base body (12) is made of a ferromagnetic material, wherein the rotor (10) has a number of cover bodies (20-1 to 20-6) corresponding to the number of pole shoes (16) radially outside and the cover bodies (20-1 to 20-6) are arranged in the circumferential direction (u) across the pole shoes, wherein the cover bodies (20-1 to 20-6) associated with a pole shoe (16) are each spaced apart from each other such that a pole shoe surface section (16-4) without a cover body remains for each pole shoe (16). The invention is characterized in that the cover bodies (20-1 to 20-6) are made of an anisotropic ferromagnetic material and are arranged alternately in the circumferential direction (u),are arranged having a first magnetic preferred direction and a second magnetic preferred direction, and that each pole shoe (16) is assigned two cover bodies (20-1 to 20-6) having different magnetic preferred directions, wherein each pole shoe (16) has a pole leg (16-1) carrying the excitation winding (18) and a pole head (16-2) radially outwardly delimiting the excitation winding (18), wherein the pole head (16-2) has a central extension (16-3) extending radially outward from the pole head (16-2), over which the cover bodies (20-1 to 20-6) assigned to a pole shoe (16) are arranged spaced apart from each other, and whose radial outer surface forms the cover-body-less pole shoe surface section (16-4), wherein each pole shoe (16) has two magnetic flux barriers (30, 32),which are arranged to the left and right of the central extension (16-3) when viewed in the circumferential direction (u) and which are arranged in the radial direction (r) between the pole head (16-2) and the associated cover bodies (20-1 to 20-6).

Description

[0001] The invention relates to a rotor for a separately excited synchronous machine of the type specified in the preamble of claim 1, a separately excited synchronous machine according to claim 6, and a motor vehicle according to claim 7.

[0002] Rotors for separately excited synchronous machines, methods for their manufacture, corresponding separately excited synchronous machines, and motor vehicles that use such separately excited synchronous machines as drives are sufficiently known from the prior art. Reference is made to DE 10 2020 129 142 A1 by way of example only.

[0003] It is also known that by utilizing the reluctance effect, i.e., by increasing the reluctance torque, the efficiency of a separately excited synchronous machine can be significantly improved. The generic patent DE 10 2020 103 695 A1 proposes to design each rotor pole with a recess and to arrange an anisotropic material in the recess such that the anisotropic material causes an increase in the reluctance torque.

[0004] A rotor of the generic type, having the features of the preamble of claim 1, for a separately excited synchronous machine is disclosed in DE 10 2018 213 567 B3.

[0005] To optimize the magnetic flux, EP 2 999 088 A1 proposes that the pole shoe has a material which, at least in certain areas, exhibits magnetic anisotropy with a light axis and a heavy axis of magnetizability.

[0006] For a better understanding of the present invention, reference is also made to page 219 of the book "Fundamentals of Electrical Machines", 9th, completely revised edition, 2006, ISBN 978-3-527-40524-4, authors: Müller, Germar and Ponick, Bernd: "In main elements with pronounced poles (see Figure 2.2.3), the magnetic circuit consists of the yoke and the poles with pole core and pole shoes. The basic structure is shown in Figure 2.3.1. The pole shoe and pole core are often manufactured as a single unit." That is, in the literature, the term "pole shoe" is used to designate a section of a rotor pole, namely the section that connects radially to the pole core—and not, as in the following disclosure, to designate a rotor pole per se.

[0007] The invention is based on the objective of providing an improved rotor for a separately excited synchronous machine.

[0008] This problem is solved by the characterizing features of claim 1 in conjunction with its preamble features.

[0009] In a known manner, the rotor of a separately excited synchronous machine comprises a base body with several pole shoes, each containing an excitation winding, evenly distributed around its circumference. "Several pole shoes evenly distributed around the circumference" means that the rotor has 2, 4, 6, 8, etc. rotor poles, which, for example in the case of a 6-pole rotor, are arranged evenly distributed around the circumference at 60° intervals. The base body, and thus the pole shoes, are made of a ferromagnetic material in a known manner.

[0010] Furthermore, the rotor has a number of cover bodies corresponding to the number of pole shoes on its radial outer surface, i.e., on its radial outer circumferential surface, which are arranged across pole shoes when viewed in the circumferential direction u, wherein the cover bodies assigned to a pole shoe and thus to an excitation winding are each spaced apart from each other in such a way that a central pole shoe surface section without cover bodies remains for each pole shoe.

[0011] According to the invention, it is now provided that the base body is made of an isotropic ferromagnetic material, in particular soft iron, and the cover bodies are made of an anisotropic ferromagnetic material, such as grain-oriented electrical steel sheets, and that the cover bodies are arranged alternately in the circumferential direction u, having a first magnetic preferred direction and a second magnetic preferred direction, wherein, in the circumferential direction u, the cover bodies are arranged across pole shoes in such a way that each pole shoe and thus each excitation winding is assigned two cover bodies having different magnetic preferred directions.

[0012] For the sake of completeness, it should be noted that the cover bodies made of an anisotropic ferromagnetic material, exhibiting a preferred magnetic direction, have a better magnetic conductivity and thus a higher permeability when viewed in the direction of their preferred magnetic direction than the base body made of an isotropic ferromagnetic material. That is, viewed in the direction of their preferred direction, the cover bodies act as a "flux amplifier".

[0013] The targeted setting or provision of a preferred magnetic direction is made possible in a simple way, e.g. when forming the cover bodies from grain-oriented electrical steel sheets, by a corresponding orientation of the rolling direction.

[0014] The formulation, namely that the cover bodies assigned to a pole shoe have first and second magnetic preferred directions, is to be understood in particular as meaning that the magnetic preferred directions of the cover bodies are aligned in directions of rotation of the magnetic field induced by the excitation winding of the pole shoe, i.e. essentially in the flux direction of the field lines of the magnetic field induced by the excitation winding.

[0015] The arrangement of the cover bodies according to the invention has the effect that – when operating in a separately excited synchronous machine – the cover bodies associated with a pole shoe act as “flux amplifiers” along the main axis or the d-axis of the rotor pole due to their magnetic preferred directions being aligned essentially in the direction of the field lines of the excitation winding. That is, the inductance of the main axis Ld increases, which in turn – since the inductance in the direction of the transverse axis Lq remains essentially unaffected – leads to an increase in the ratio of the inductance of the main axis to the transverse axis Ld / Lq, which in turn results in an increased reluctance torque.

[0016] A further advantage of the arrangement of the cover bodies according to the invention is that – since these now cover the gap or cavity between the excitation coils of two adjacent pole shoes, as viewed in the circumferential direction u – both the windings of the excitation coils and any potting material, for example based on a resin material, filled into the gap or cavity are held in position by the cover bodies. This means that additional components, such as so-called wedge slots, to hold the potting material and the windings in position at the high rotational speeds and to prevent vibrations, are no longer required due to the design of the rotor according to the invention.

[0017] According to the invention, each pole shoe has a pole leg supporting the excitation winding and a pole head radially outwardly delimiting the excitation winding. The pole head is designed such that it has a central, rib-shaped extension extending radially outward from the pole head, over which the cover bodies associated with a pole shoe, and thus with an excitation winding, are arranged spaced apart from one another in the circumferential direction u, and whose radial outer surface forms the pole shoe section without cover bodies.This design proves particularly advantageous with regard to manufacturing, since on the one hand the limiting effect of the pole head in the radial direction facilitates the application of the excitation winding, and on the other hand the radially extending, web-shaped extension ensures a precise fit of the cover bodies associated with a pole shoe.

[0018] Furthermore, according to the invention, each pole shoe also has two magnetic flux barriers, which – viewed in the circumferential direction u – are arranged to the left and right of the central extension and – viewed in the radial direction r – between the pole head and the associated cover bodies. This design proves to be particularly advantageous because, when operating in a separately excited synchronous machine, the flux barriers now cause a reduction in inductance in the direction of the transverse axis, i.e., a reduction of Lq. This means that the ratio of the inductances Ld / Lq increases, which in turn results in an increase in the reluctance torque.

[0019] Preferably, each pole head has first molded sections, and the cover bodies have correspondingly shaped second molded sections via which the cover bodies and the associated pole shoes engage with each other in a positive-locking manner in the radial direction. An advantage of this design is that, due to the positive-locking connection between the cover bodies and the pole shoes, simple and quick assembly is ensured.

[0020] Preferably, the two magnetic flux barriers are arranged such that, with respect to a width b of the pole leg of the pole shoe carrying the excitation winding, the following applies for a distance d between the left and the right magnetic flux barrier: Distance d between the magnetic flux barriers; width b of the pole arm ≥ 1 This advantageously ensures that the flux barriers do not influence the field lines running along the main axis or d-axis, and thus the flux barriers do not act as a "magnetic bottleneck" with respect to the field lines aligned along the main axis or d-axis.

[0021] Preferably, the magnetic flux barriers are designed as through-holes extending in the axial direction a. This design as through-holes results in a lighter rotor and thus lower rotational inertia. A further advantage is that the flux barriers designed as through-holes can serve to cool the rotor; for example, if the through-holes are filled with air or a coolant. It is particularly preferred that—in the case of cooling by means of a coolant—a hose, e.g., made of plastic or copper, is passed through the through-holes, containing the coolant.

[0022] Alternatively, it is also conceivable that the openings are filled with a non-magnetic material, such as plastic, a resin material or copper.

[0023] A process for manufacturing the rotor includes the following steps: • Providing the base body containing the pole shoes; • Providing the cover plates; • Applying the exciter windings to the pole legs of the pole shoes, • Sliding the cover bodies onto the pole shoes in an axial direction, thus creating a positive connection between the cover bodies and the pole shoes; • Filling the remaining cavities between two pole shoes with a potting material, such as an elastomer or a resin material.

[0024] A particularly advantageous feature is that the axial sliding of the cover bodies creates a positive connection between the cover bodies and the pole shoes, eliminating the need for additional fastening steps and / or measures. This ensures a simple, quick, and cost-effective installation.

[0025] The invention further aims to provide a separately excited synchronous machine comprising a stator and a rotor rotatably mounted in the stator, with an improved efficiency.

[0026] This problem is solved by designing the rotor according to one of claims 1 to 5.

[0027] As already explained, the cover bodies and flux barriers provided and arranged according to the invention lead to a significant increase in the Ld / Lq ratio and thus to an increase in the reluctance torque. This means that, due to these measures, the synchronous machine according to the invention exhibits a higher torque and thus an improved efficiency for the same excitation current.

[0028] The invention further aims to develop a motor vehicle comprising a separately excited synchronous machine as a drive unit in such a way as to enable a greater range.

[0029] This problem is solved by designing the externally excited synchronous machine according to claim 6.

[0030] Since, as already explained, the synchronous machine according to the invention has an improved efficiency and thus a reduced consumption of electrical energy, an increased range is advantageously ensured.

[0031] Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the embodiment shown in the drawing.

[0032] In the drawing, this means: Fig. 1 a rotor according to the invention for a separately excited synchronous machine in cross-section; Fig. 2 an enlarged view of a pole shoe of the rotor according to the invention made of Fig. 1; Fig. 3a a perspective representation of the basic body connected with a wave at the beginning of the manufacturing process; Fig. 3b the basic body made of Fig. 3a in a sectional view; Fig. 4a the basic body made of Fig. 3a after the pathogen windings were applied; Fig. 4b the basic body from Fig. 4a in a sectional view; Fig. 5 the process step of sliding a cover body onto the base body; Fig. 6a the basic body made of Fig. 4a after all cover bodies are attached; Fig. 6b the cover body 6a in a sectional view; Fig. 7a the finished rotor 10, i.e. after the gap or cavity between two pole shoes has been filled with a potting material, and Fig. 7b turn the rotor off Fig. 7a in a sectional view.

[0033] In Fig. Figure 1 shows a cross-sectional view of a rotor for a separately excited synchronous machine, designated by the reference numeral 10. The rotor 10 comprises a base body 12, which is connected to a shaft 14 in a known manner to prevent rotation.

[0034] How Fig. As can be seen further in Figure 1, the rotor 10 comprises six pole shoes 16 arranged evenly distributed around its circumference, i.e., offset by 60° in this case, each of which is assigned an excitation winding 18 in a known manner. The axis along which the magnetic flux of the pole shoes 16 runs is designated by the reference symbol d-axis; correspondingly, the quadrature axes, which in the illustrated 6-pole configuration are each oriented 30° to the left and right of the d-axis, are designated by the reference symbol q-axis.

[0035] For the sake of clarity, in Fig. 1 only a pole shoe and an excitation winding are provided with the corresponding reference numbers 16, 18 and the axis designations d-axis, q-axis.

[0036] The base body 12 and the pole shoes 16, which are integrally connected to it, are made of an isotropic ferromagnetic material, for example soft iron.

[0037] How Fig. As can be seen further in Figure 1, the rotor 10 has a number of cover bodies on its radial outer circumferential surface corresponding to the number of pole shoes 16 – in this case, six – which are designated by the reference numerals 20-1 to 20-6. The cover bodies 20-1 to 20-6 are made of an anisotropic ferromagnetic material, for example, grain-oriented electrical steel sheets. That is, the cover bodies 20-1 to 20-6 have a so-called preferred magnetic direction in which they exhibit better magnetic conductivity and thus a higher permeability than the base body 12.

[0038] The magnetic preferred direction of the cover bodies 20-1 to 20-6 is in Fig. 1 symbolically represented by the orientation of the hatching. As can be seen from the hatching, the cover bodies 20-1 to 20-6 are arranged alternately in the circumferential direction u such that cover bodies 20-1, 20-3 and 20-5 have a first magnetic preferred direction and cover bodies 20-2, 20-4 and 20-6 have a second magnetic preferred direction.

[0039] Furthermore, as can be seen from Fig. 1 can be seen, the cover bodies 20-1 to 20-6 are arranged across pole shoes in such a way that each pole shoe 16 is assigned two cover bodies with different magnetic preferred directions.

[0040] So they are, as from Fig. As can be seen in Figure 2, the depicted pole shoe 16 is assigned two cover bodies, namely cover body 20-1 with a first preferred magnetic direction, and cover body 20-2 with a second preferred magnetic direction. It is only additionally noted that in Fig. 2 the rotor 10 is shown in the installed state, i.e. next to the pole shoe 16 of the rotor 10 a stator designated with reference numeral 22 with associated stator windings 24 is shown section by section.

[0041] This includes, as can be seen from Fig. 2 as can be seen from the hatching shown, the magnetic preferred directions of the cover bodies 20-1 and 20-2 are chosen or “set” so that they are aligned in directions of rotation of the magnetic field induced by the excitation winding 18 of the pole shoe 16, i.e. essentially in the flux direction of the field lines of the magnetic field induced by the excitation winding 18.

[0042] Furthermore, as can be seen from Fig. 1 can be seen, the cover bodies assigned to a pole shoe 16 are arranged at such a distance from each other that a central pole shoe surface section 16-4 remains for each pole shoe 16, without a cover body.

[0043] In the present case, as can be seen in particular from the following: Fig. As can be seen in the enlarged illustration of the pole shoe 16, the pole shoes 16 are designed such that each has a pole leg 16-1 carrying the excitation winding 18, and a pole head 16-2 radially outwardly delimiting the excitation winding 18. The pole head 16-2 is designed such that it has a central extension 16-3 extending radially outward from the pole head 16-2, over which the cover bodies associated with the pole shoe 16, i.e., according to Fig. 2 the cover bodies 20-1 and 20-2 are arranged apart from each other, and its radial outer surface forms the cover-body-less pole shoe section 16-4.

[0044] In order to enable a positive-locking attachment of the cover bodies 20-1 to 20-6 to the rotor 10, the pole heads 16-2 each have first molded sections 26 and the cover bodies have correspondingly designed second molded sections 28, via which the cover bodies and pole shoe engage positively with each other in radial direction r, cf. Fig. 2 as well as Fig. 3b and Fig. 5.

[0045] Furthermore, it shows - as shown by Fig. 1 and Fig. 2. As can be seen, each pole shoe 16 has two magnetic flux barriers 30, 32, arranged in the circumferential direction u to the left and right of the central extension 16-3 and in the radial direction r between the pole head 16-3 and the associated cover bodies. The distance d between the flux barriers 30, 32 is chosen such that it corresponds at least to the width b of the pole leg 16-1, cf. Fig. 1, in other words, distance d ≥ width b.

[0046] In the present case, the river barriers 30 and 32 are designed in the form of passage openings extending in axial direction a.

[0047] The design of the rotor 10 according to the invention has the effect that the cover bodies 20-1 to 20-6 assigned to the pole shoes 16 act as "flux amplifiers" along the d-axis of the rotor pole 16 due to their magnetic preferred directions being oriented essentially in the direction of the field lines of the excitation winding 18, and thus lead to an increase in the inductance of the main axis Ld, and that the flux barriers 30 and 32, due to their arrangement, cause a reduction in the inductance in the direction of the q-axis, i.e. a reduction of Lq.

[0048] That is, the ratio of the inductances Ld / Lq increases, so that an increased reluctance torque occurs or can be observed.

[0049] In Fig. Figures 3a to 7b show the different process steps for manufacturing the rotor 10 according to the invention.

[0050] Fig. 3a and Fig. Figure 3b shows the base body 12, which has the pole shoes 16 and is already rotationally fixed to a shaft 14, in a perspective view, cf. Fig. 3a, and a sectional view, see 3b.

[0051] Fig. 4a and Fig. 4b shows the rotor from Fig. 3a, Fig. 3b after the pathogen windings 18 were applied.

[0052] Fig. Figure 5 shows the attachment of the cover body 22-1 to the rotor 10. As shown from Fig. As can be seen in Figure 5, this is done by sliding the cover body in the axial direction a. The situation after all cover bodies 22-1 to 22-6 are attached is shown in Fig. 6a and Fig. Figure 6b shows the gap or cavity remaining between two excitation coils 18, which is designated by the reference numeral 34.

[0053] Fig. 7a and Fig. Figure 7b shows the rotor 10 after the last process step, i.e., the gaps or cavities 34 were filled with a potting material 36.

Claims

[1] Rotor (10) for a separately excited synchronous machine, comprising a base body (12) with a plurality of pole shoes (16) evenly distributed over the circumference, each having an excitation winding (18), wherein the base body (12) is formed from a ferromagnetic material, wherein the rotor (10) has, radially outwardly, a number of cover bodies (20-1 to 20-6) corresponding to the number of pole shoes (16), and the cover bodies (20-1 to 20-6) are arranged across the pole shoes in the circumferential direction (u), wherein the cover bodies (20-1 to 20-6) assigned to a pole shoe (16) are each arranged at a distance from one another such that a pole shoe surface section (16-4) without a cover body remains for each pole shoe (16), characterized bythat the base body (12) is formed from an isotropic ferromagnetic material and that the cover bodies (20-1 to 20-6) are formed from an anisotropic ferromagnetic material and are arranged alternately in the circumferential direction (u), having a first magnetic preferred direction and a second magnetic preferred direction, and that each pole shoe (16) is assigned two cover bodies (20-1 to 20-6) having different magnetic preferred directions, wherein each pole shoe (16) has a pole leg (16-1) carrying the excitation winding (18) and a pole head (16-2) delimiting the excitation winding (18) radially outwards, wherein the pole head (16-2) has a central extension (16-3) extending further radially outwards from the pole head (16-2), via which the cover bodies assigned to a pole shoe (16) (20-1 to 20-6) are arranged at a distance from each other,and whose radial outer surface forms the cover-body-free pole shoe surface section (16-4), wherein each pole shoe (16) has two magnetic flux barriers (30, 32) which, viewed in the circumferential direction (u), are arranged to the left and right of the central extension (16-3) and which, in the radial direction (r), are arranged between the pole head (16-2) and the associated cover bodies (20-1 to 20-6). [2] Rotor (10) according to claim 1, characterized by that the pole head (16-2) has first shaped sections (26) and the cover bodies (20-1 to 20-6) have second shaped sections (28) corresponding thereto, via which the cover bodies (20-1 to 20-6) and pole shoes (16) are in positive engagement with one another. [3] Rotor (10) according to claim 1, characterized bythat the two magnetic flux barriers (30, 32) are arranged such that, based on a width (b) of the pole leg (16-1) of the pole shoe (16) carrying the excitation winding (18), the following applies to a distance (d) between the left and right magnetic flux barriers (30, 32): Distance (d) between the magnetic flux barriers (30, 32) Width (b) of the pole leg (16) ≥ 1 [4] Rotor (10) according to claim 1, characterized by that the magnetic flux barriers (30, 32) are designed in the form of passage openings extending in the axial direction (a). [5] Rotor (10) according to claim 4, characterized by that the openings are filled with a non-magnetic material. [6] Separately excited synchronous machine, comprising a stator (22) and a rotor (10) rotatably mounted in the stator (22), characterized by that the rotor (10) is designed according to one of claims 1 to 5. [7] Motor vehicle comprising a separately excited synchronous machine, characterized by that the separately excited synchronous machine is designed according to claim 6.

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