Electric machine, in particular axial flux machine, with shielding structure

Abstract

The invention relates to an electric machine having a stator, a rotor, an air gap between the stator and the rotor by means of which the stator and the rotor are spaced apart from one another, and a shielding structure for reducing a capacitive coupling between the stator and the rotor. The shielding structure is coupled to a reference potential. The shielding structure is arranged in the air gap and has a plurality of conductors. The plurality of conductors each have a first portion, wherein elongations of the first portions of the plurality of conductors extend transversely to a magnetic flux direction of the electric machine. The plurality of conductors each have a second portion, wherein elongations of the second portions of the plurality of conductors extend, nested in one another in a comb-like or meander-like manner, transversely to the magnetic flux direction and in a direction that differs from a direction of the elongations of the first portions.

Description

[0001] Description

[0002] Title of the invention

[0003] Electrical machine, in particular axial flux machine, with shielding structure

[0004] field of technology

[0005] The present invention relates to an electrical machine, in particular an axial flux machine, with a shielding structure.

[0006] State of the art

[0007] Due to PWM control of electrical machines by power electronics, high-frequency interference signals are generated, which are radiated by windings and other components (e.g. a stator) of the electrical machine.

[0008] This EMC interference potential is particularly high in H-type axial flux machines (two lateral rotors and a central stator). Due to the often ungrounded stator cores, an additional (indirect) capacitive coupling occurs between the windings and rotor disks (via the stator cores), resulting in a large overall capacitive coupling between the windings and the rotor disks.

[0009] This must be minimized to comply with EMC requirements.

[0010] From the unpublished German patent application with the official file number 10 2023 109 815.2, a shielding structure for an axial flux machine is known, as shown in Fig. 9.

[0011] In Fig. 9, reference numeral 1 denotes a shielding structure, reference numeral 2 denotes a conductor, reference numeral 10 denotes a stator (only partially shown), and reference numeral 30 denotes an air gap. As shown in Fig. 9, the shielding structure 1 is arranged on the stator 10 on a side of the stator 10 facing the air gap 30. To keep eddy currents in the conductors 2 of the shielding structure 1 low, these are designed as thin conductors 2. These individual conductors 2 run radially, form elongated gaps, and serve as shielding elements. A common grounding of the conductors 2 is provided radially inward.

[0012] However, thin gaps between the individual conductors 2 serving as shielding elements become permeable to high-frequency EMC emissions with increasing frequency.

[0013] Summary of the invention

[0014] Technical task

[0015] It is therefore the object of the present invention to provide an electrical machine with an improved shielding structure which, in particular, reduces a capacitive coupling between a stator and a rotor by optimised shielding between these two.

[0016] Technical solution

[0017] The problem is solved by the measures specified in the independent claim.

[0018] According to one aspect, an electric machine comprises a stator, a rotor, an air gap located between the stator and the rotor, by means of which the stator and the rotor are arranged at a distance from one another, and a shielding structure for reducing a capacitive coupling between the stator and the rotor. The shielding structure is coupled to a reference potential. The shielding structure is arranged in the air gap and comprises a plurality of conductors. The plurality of conductors each have a first section, wherein longitudinal extensions of the first sections of the plurality of conductors extend transversely to a magnetic flux direction of the electric machine.The plurality of conductors each have a second section, wherein longitudinal extensions of the second sections of the plurality of conductors extend in a comb-like or meander-like manner interleaved transversely to the magnetic flux direction and in a direction different from a direction of the longitudinal extensions of the first sections.

[0019] According to this aspect, only short slots effectively transmit electromagnetic waves. These short slots only become permeable at significantly higher frequencies than, for example, straight slots that would run perpendicular to the magnetic flux direction across the entire length of the shielding structure.

[0020] The longitudinal dimensions of the respective sections are the dimensions of the sections of the respective conductors along a largest dimension of the respective conductors. In other words, the respective conductors or the sections of the respective conductors each have a longitudinal dimension, a height dimension, and a width dimension; the longitudinal dimension is greater than the height dimension and greater than the width dimension; and the longitudinal dimensions of the respective conductors or the sections of the respective conductors run along this longitudinal dimension.

[0021] Further advantageous embodiments of the present invention are the subject of the dependent claims.

[0022] According to one embodiment, a coupling of conductors of the plurality of conductors that are adjacent to one another in a circumferential direction to the reference potential is formed radially inward or radially outward along the circumferential direction or alternately radially inward and radially outward.

[0023] According to a further embodiment, the plurality of conductors comprise a plurality of first conductors arranged in a first layer and a plurality of second conductors arranged in a second layer, and the first layer and the second layer are arranged one above the other in the magnetic flux direction.

[0024] According to a further embodiment, the plurality of conductors of the first layer and the plurality of conductors of the second layer are arranged at least partially adjacent to one another in a plan view of the stator in the direction of the axis of rotation.

[0025] According to a further embodiment, the reference potential is a potential of a housing of the electrical machine or a ground potential.

[0026] According to a further embodiment, the shielding structure is formed from an electrically conductive material.

[0027] According to a further embodiment, the shielding structure is arranged on the stator.

[0028] According to a further embodiment, the shielding structure surrounds windings and winding heads of the stator.

[0029] According to a further embodiment, the electrical machine is designed as an axial flux machine, the longitudinal extensions of the first sections extend in a radial direction of the electrical machine and the longitudinal extensions of the second sections extend at least partially in a circumferential direction of the electrical machine.

[0030] According to a further embodiment, the axial flux machine has two stators and a rotor arranged in an axial direction between the two stators, and each of the two stators has the shielding structure.

[0031] According to a further embodiment, the axial flux machine has two rotors and a stator arranged in an axial direction between the two rotors. According to a further embodiment, the electric machine is designed as a radial flux machine, the longitudinal dimensions of the first sections extend in an axial direction of the electric machine, and the longitudinal dimensions of the second sections extend at least partially in a circumferential direction of the electric machine.

[0032] In other words, according to the preceding aspect or embodiments, the following measures are carried out:

[0033] Straight, elongated gaps between adjacent conductors of the shielding structure are avoided.

[0034] Coverage is increased by constructing the shielding structure in multiple layers. Preferably, the individual conductors from different layers are offset from one another in such a way that, viewed together, the individual conductors form the most closed surface possible in a top view or projection onto the shielding structure.

[0035] Alternating radially inner and radially outer couplings of adjacent conductors of the shielding structure lead to opposite current directions in the adjacent conductors of the shielding structure, thereby reducing the inductance of the individual conductors of the shielding structure and consequently optimizing the high-frequency behavior of the electrical machine.

[0036] Short description of the drawings

[0037] The present invention will be explained in more detail below by describing embodiments with reference to the accompanying drawings.

[0038] In the drawing: Fig. 1 shows a schematic sectional view of a basic structure of an axial flow machine;

[0039] Fig. 2 is a schematic sectional view of a basic structure of an axial flow machine in a so-called I-arrangement;

[0040] Fig. 3 is a schematic sectional view of a basic structure of an axial flow machine in a so-called H-arrangement;

[0041] 4a and 4b are schematic views of a shielding structure according to a first embodiment of the present invention;

[0042] 5a and 5b are schematic views of a shielding structure according to a second embodiment of the present invention;

[0043] 6a and 6b are schematic views of a shielding structure according to a third embodiment of the present invention;

[0044] 7a and 7b are schematic views of the shielding structure according to the third embodiment of the present invention;

[0045] Fig. 8a and 8b are schematic views of the shielding structure according to the third embodiment of the present invention; and

[0046] Fig. 9 shows a section of an axial flow machine with a shielding structure in the prior art.

[0047] Description of the embodiments

[0048] Before various embodiments are described in detail below, it should be noted that all embodiments described below are applied to an electrical machine or with an electrical machine, and in particular an electrical axial flux machine.

[0049] Fig. 1 shows a schematic sectional view of a basic structure of an axial flow machine.

[0050] In Fig. 1, reference numeral 10 denotes a stator, reference numeral 20 denotes a rotor, reference numeral 30 denotes an air gap, reference numeral 40 denotes a rotation axis, and reference numeral 50 denotes a magnetic flux direction.

[0051] An axial direction is defined as a direction along the direction of the rotational axis. A radial direction is defined as a direction that runs from a center point of the preferably disc-shaped stator 10 or rotor 20, through which the rotational axis 40 runs, from radially inside to radially outside, or vice versa. A circumferential direction is defined as a direction that runs along a circumference of the preferably disc-shaped stator 10 or rotor 20.

[0052] Fig. 1 shows a sectional view cut along a plane in which the axis of rotation of the axial flux machine runs.

[0053] As shown in Fig. 1, in the axial flux machine, the magnetic flux direction 50 between the stator 10 and the rotor 20 runs parallel to the rotational axis 40 of the rotor 20 of the axial flux machine, i.e., in the axial direction of the axial flux machine. Often, both the stator 10 and the rotor 20 are largely disk-shaped. Axial flux machines are particularly advantageous when the axially available installation space is limited in a given application. In addition to the shortened axial length, another advantage of the axial flux machine is its comparatively high torque density.

[0054] An electric axial flux machine can be designed in an I-arrangement or an H-arrangement. Fig. 2 shows a schematic view of a basic design of an axial flux machine in a so-called I-arrangement.

[0055] In Fig. 2, the same or corresponding parts are designated by the same or corresponding reference numerals as in Fig. 1, so that with regard to these same or corresponding parts, reference is made to Fig. 1 and its description and a repeated description is omitted at this point.

[0056] In the I-arrangement, the rotor 20 is arranged axially next to the stator 10 or, as shown in Fig. 2, between two stators 10.

[0057] Fig. 3 shows a schematic view of a basic structure of an axial flux machine in a so-called H-arrangement.

[0058] In Fig. 3, the same or corresponding parts as in Fig. 1 and Fig. 2 are designated by the same or corresponding reference numerals, so that with regard to these same or corresponding parts, reference is made to Fig. 1 and Fig. 2 and their description and a repeated description is omitted at this point.

[0059] In the H-arrangement, two rotors 20 are arranged on opposite axial sides of a stator 10.

[0060] The following embodiments can be applied to both of the aforementioned arrangements, but are particularly advantageously applicable to an H-arrangement.

[0061] The following embodiments also show and describe the individual features using the example of an axial flux machine with an annular disk-shaped air gap. However, these can also be implemented for a radial flux machine with a cylindrical wall-shaped air gap or for other designs of electrical machines, for example, a linear motor. The shielding structures described in detail below are arranged in the air gap 30 to reduce capacitive coupling between the stator 10 and the rotor 20 and are preferably arranged on the stator 10 and coupled to a reference potential. The reference potential is preferably a potential of a housing of the electrical machine and / or a ground potential.

[0062] A first embodiment is described below.

[0063] Figs. 4a and 4b show schematic views of a shielding structure according to a first embodiment of the present invention.

[0064] In Fig. 4a and Fig. 4b, the reference number 1 denotes the shielding structure, the reference number 2 denotes respective conductors of the shielding structure 1, the reference number 2a denotes respective first sections of the conductors 2, the reference number 2b denotes respective second sections of the conductors 2 and the reference number A denotes a first region, which is shown enlarged in Fig. 4b compared to Fig. 4a.

[0065] According to this embodiment, long slots running straight in one direction only between the respective conductors 2 are avoided.

[0066] Through the meandering or wavy respective conductors 2 with the first sections 2a extending with their longitudinal extents transversely to the magnetic flux direction and the second sections 2b nested with their longitudinal extents in a meandering manner transversely to the magnetic flux direction and extending in a direction different from a direction of the longitudinal extents of the first sections 2a, gaps run between the respective conductors 2 in a wave shape.

[0067] This results in only effectively short slots for electromagnetic waves. These short slots only become permeable at significantly higher frequencies than, for example, straight slots, which would run across their entire length perpendicular to the magnetic flux direction—i.e., in the case of an axial flux machine, across their entire radial length or exclusively in the radial direction of the shielding structure 1.

[0068] A coupling of conductors 2 adjacent to one another in a circumferential direction to a reference potential, such as a housing of the electrical machine and / or a ground potential, is provided radially outwardly on the first sections 2a. However, the coupling of conductors 2 adjacent to one another in the circumferential direction can also be formed radially outwardly or alternately radially inwardly and radially outwardly on the first sections 2a.

[0069] A second embodiment is described below.

[0070] Figs. 5a and 5b show schematic views of a shielding structure according to the second embodiment of the present invention.

[0071] In Fig. 5A and Fig. 5B, the same or corresponding reference numerals designate the same or corresponding parts as in Fig. 4A and Fig. 4B, so that a repeated description of these and the same or corresponding parts is omitted in the following and reference is made to Fig. 4A and Fig. 4B and only the differences from the first embodiment shown in Fig. 4A and Fig. 4B are discussed below.

[0072] According to this embodiment, long slots running straight in one direction only between the respective conductors 2 are also avoided.

[0073] Through the comb-shaped respective conductors 2 with the first sections 2a extending with their longitudinal extents transversely to the magnetic flux direction and the second sections 2b nested with their longitudinal extents in a comb-shaped manner, transversely to the magnetic flux direction and extending in a direction different from a direction of the longitudinal extents of the first sections 2a, gaps run between the respective conductors 2 along the comb shape.

[0074] This means that only effectively short slits result for electromagnetic waves.

[0075] These short slots only become permeable at significantly higher frequencies than, for example, straight slots which would run over a complete length transverse to the magnetic flux direction, ie in the case of the axial flux machine over a complete radial length or exclusively in the radial direction of the shielding structure 1.

[0076] A coupling of conductors 2 adjacent to one another in a circumferential direction to a reference potential, such as a housing of the electrical machine and / or a ground potential, is provided radially outwardly on the first sections 2a. However, the coupling of conductors 2 adjacent to one another in the circumferential direction can also be formed radially outwardly or alternately radially inwardly and radially outwardly on the first sections 2a.

[0077] In other words, adjacent conductors form a comb structure with respective prongs on each side of the first sections 2a through the second sections 2b.

[0078] The interlocking prongs of the adjacent conductors 2 form only short, straight slots running in only one direction.

[0079] To avoid eddy currents, the individual conductors 2 can have dimensions close to the limits of a feasible width of conductor tracks and distances between conductor tracks in printed circuit boards. For example, conductor widths of 0.4 mm for the conductors 2 and distances between adjacent conductors 2 of 0.4 mm can be provided. Technically, the conductor widths of the conductors 2 can be smaller than the distances between adjacent conductors 2. Significantly thinner conductors 2 compared to the distance between adjacent conductors 2 consequently have a less favorable area ratio between areas with shielding and intermediate regions. Thus, the conductor widths are preferably not significantly smaller than the distances between adjacent conductors 2.

[0080] A third embodiment is described below.

[0081] Figs. 6a to 8b show schematic views of a shielding structure according to the third embodiment of the present invention.

[0082] In Fig. 6A to Fig. 8B, the same or corresponding reference numerals designate the same or corresponding parts as in Fig. 4A to Fig. 5B, so that a repeated description of these and the same or corresponding parts is omitted in the following and reference is made to Fig. 4A to Fig. 5B and only the differences from the first embodiment shown in Fig. 4A and Fig. 4B and the second embodiment shown in Fig. 5A and Fig. 5B are discussed below.

[0083] In Fig. 6a to Fig. 8b, reference numeral 3 denotes respective first conductors of the shielding structure 1, reference numeral 3a denotes respective first sections of the first conductors 3, reference numeral 3b denotes respective second sections of the first conductors 3, reference numeral 4 denotes respective second conductors of the shielding structure 1, reference numeral 4a denotes respective first sections of the second conductors 4, reference numeral 4b denotes respective second sections of the second conductors 4, reference numeral B denotes a second region, which is shown enlarged in Fig. 7b compared to Fig. 7a, and reference numeral C denotes a third region, which is shown enlarged in Fig. 8b compared to Fig. 8a. It should be noted that Fig. 6A and Fig. 6B each show a plan view in the direction of the axis of rotation 40, Fig. 7A and Fig. 7B show a first perspective view, and Fig. 8A and Fig.8B shows a second perspective view different from the first perspective view in order to clarify the features of this embodiment, in particular with regard to possible spatial relationships of the first conductors 3 and the second conductors 4 to one another.

[0084] According to this embodiment, long slots running straight in one direction only between the respective conductors 3, 4 are also avoided.

[0085] This is achieved according to the third embodiment by means of the first sections 3a of the first conductors 3, the second sections 3b of the first conductors 3, the first sections 4a of the second conductors 4, and the second sections 4b of the second conductors 4, wherein the first conductors 3 are arranged on a different support than the second layer 4. It should be noted that the further features of the first sections 3a, 4a and the second sections 3b, 4b are analogous to the features of the first sections 2a and the second sections 2b of the second embodiment, and therefore, with regard to these further features of the first sections 3a, 4a and the second sections 3b, 4b, reference is made to the preceding statements regarding the first sections 2a and the second sections 2b of the second embodiment in order to avoid a repeated description.

[0086] According to this embodiment, the shielding structure 1 is designed in multiple layers, with a two-layer design being shown as an example.

[0087] The multi-layer shielding structure comprises respective first conductors 3 in a first layer and respective second conductors 4 in a second layer in order to optimize the area ratio between the shielded areas and the intermediate regions. The conductors 3, 4 of the individual layers are offset from one another (parallel or skew) such that, in a projection or plan view in the direction of the rotation axis, the individual layers 3, 4 complement one another, thus resulting in the most closed shielding surface possible. Compared to the previously described second embodiment, the distances between the conductors 3, 4 and the width of the individual conductors 3, 4 are the same as those of the conductors 2.

[0088] However, compared to the second embodiment, the area coverage with two layers in the third embodiment is significantly larger.

[0089] According to the third embodiment, the first layer and the second layer are arranged one above the other in the magnetic flux direction and the plurality of conductors 3 of the first layer and the plurality of conductors 4 of the second layer are arranged at least partially adjacent to one another in a plan view of the stator 10 in the direction of the rotation axis.

[0090] The following describes configurations of the first to third embodiments.

[0091] Connections for a reference potential, such as a ground potential, earth potential and / or a potential of a housing of the electrical machine of adjacent conductors 2, 3, 4 can be formed on alternating radial sides (radially inside and radially outside).

[0092] By setting adjacent conductors 2, 3, 4 of the shielding structure 1 at opposite radial ends, ie radially inside and radially outside, to reference potential or being coupled to the reference potential, current directions of these adjacent conductors 2, 3, 4 are at least partially opposite.

[0093] The opposite current directions reduce the effective inductance of the individual conductors 2, 3, 4.

[0094] The possibly only partially opposing current directions are partly due to the fact that the current strength increases with increasing proximity to a conductor coupled to the reference potential. Due to the different sides of the coupling to the reference potential, the current strengths are different at a radial height. Furthermore, adjacent conductors coupled to the reference potential experience different excitations, which also lead to different current strengths and also result in different temporal current profiles.

[0095] This effect of reducing inductance also occurs in conductors 2, 3, 4 of adjacent comb teeth.

[0096] Furthermore, the shielding structure 1 in the first to third embodiments can be designed such that the shielding structure 1 surrounds windings and / or winding heads of the stator 10.

[0097] The previously described embodiments can be combined with each other in any reasonable manner, whereby in particular the multi-layer design of the third embodiment can also be applied to the meander-shaped design of the first embodiment.

[0098] Although the present invention has been described above with reference to embodiments, it should be understood that various modifications and changes may be made without departing from the scope of the present invention as defined in the appended claims.

[0099] With regard to further features and advantages of the present invention, express reference is made to the disclosure of the drawing.

[0100] List of reference symbols

[0101] A First magnification area

[0102] B Second magnification area

[0103] C Third magnification area

[0104] 1 Shielding structure

[0105] 2 conductors

[0106] 2a First section of the ladder

[0107] 2b Second section of the ladder

[0108] 3 First Director

[0109] 3a First section of the first ladder

[0110] 3b Second section of the first ladder

[0111] 4 Second Director

[0112] 4a First section of the second ladder

[0113] 4b Second section of the second conductor

[0114] 10 Stator

[0115] 20 rotors

[0116] 30 air gap

[0117] 40 axis of rotation

[0118] 50 Magnetic flux direction

Claims

Claims 1 . An electrical machine comprising: a stator (10); a rotor (20); an air gap (30) located between the stator (10) and the rotor (20), by means of which the stator (10) and the rotor (20) are arranged at a distance from one another; and a shielding structure (1) for reducing a capacitive coupling between the stator (10) and the rotor (20), wherein the shielding structure (1) is coupled to a reference potential, wherein the shielding structure (1) is arranged in the air gap (30) and has a plurality of conductors (2, 3, 4), the plurality of conductors (2, 3, 4) each have a first section (2a, 3a, 4a), wherein longitudinal extents of the first sections (2a, 3a, 4a) of the plurality of conductors (2) extend transversely to a magnetic flux direction (50) of the electrical machine, and the plurality of conductors (2, 3, 4) each have a second section (2b, 3b, 4b), wherein longitudinal extents of the second sections (2b, 3b, 4b) of the plurality of conductors (2;3, 4) are interleaved in a comb-like or meandering manner transversely to the magnetic flux direction (50) and extend in a direction different from a direction of the longitudinal extents of the first sections (2a, 3a, 4a); 2. Electrical machine according to claim 1, wherein a coupling of conductors (2, 3, 4) of the plurality of conductors (2, 3, 4) adjacent to one another in a circumferential direction to the reference potential is formed radially inward or radially outward or alternately radially inward and radially outward along the circumferential direction.

3. Electrical machine according to claim 1 or 2, wherein the plurality of conductors (3, 4) comprise a plurality of first conductors (3) arranged in a first layer and a plurality of second conductors (4) arranged in a second layer, and the first layer and the second layer are arranged one above the other in the direction of the magnetic flux.

4. Electrical machine according to claim 3, wherein the plurality of conductors (3) of the first layer and the plurality of conductors (4) of the second layer are arranged at least partially adjacent to one another in a plan view of the stator (10) in the direction of the axis of rotation (40).

5. Electrical machine according to one of claims 1 to 4, wherein the reference potential is a potential of a housing of the electrical machine or a ground potential.

6. Electrical machine according to one of claims 1 to 5, wherein the shielding structure (1) is formed from an electrically conductive material.

7. Electrical machine according to one of claims 1 to 6, wherein the shielding structure (1) is arranged on the stator (10).

8. Electrical machine according to one of claims 1 to 7, wherein the shielding structure (1) surrounds windings and winding heads of the stator (10).

9. Electrical machine according to one of claims 1 to 8, wherein the electrical machine is designed as an axial flux machine, the longitudinal extents of the first sections (2a, 3a, 4a) extend in a radial direction of the electrical machine, and the longitudinal extents of the second sections (2b, 3b, 4b) extend at least partially in a circumferential direction of the electrical machine.

10. Electrical machine according to claim 9, wherein the axial flux machine has two stators (10) and a rotor (20) arranged in an axial direction between the two stators (10), and each of the two stators (10) has the shielding structure (1).

11. Electrical machine according to claim 9, wherein the axial flux machine has two rotors (20) and a stator (10) arranged in an axial direction between the two rotors (20).

12. Electrical machine according to claim 1, wherein the electrical machine is designed as a radial flux machine, the longitudinal extents of the first sections (2a, 3a, 4a) extend in an axial direction of the electrical machine, and the longitudinal extents of the second sections (2b, 3b, 4b) extend at least partially in a circumferential direction of the electrical machine.

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