Electric machine, method for producing a flattened portion on a coil for an electric machine, and separately excited electric synchronous machine

Abstract

The invention relates to an electric machine (1) comprising a stator (2), which has a primary coil (3), and comprising a rotationally adjustable rotor (4), which has a secondary coil (5) that inductively interacts with the primary coil (3). The primary coil (4) and / or the secondary coil (5) has / have a winding (6) comprising two connection lines (8, 9), of which the first connection line (9) is referred to as a return line (9). The return line (9) extends along the winding (6) and has a line cross-section (10). It is essential to the invention that the return line (9) has a flattened portion (39), in which a height (11) of the line cross-section (10) of the return line (9) in a first transverse direction (13) is smaller than a width (12) of the line cross-section (10) in a second transverse direction (14). The invention relates in particular to a method for producing a flattened portion (39) on a coil for an electric machine (1) and to a separately excited electric synchronous machine having such an electric machine (1).

Description

[0001] Electric machine,

[0002] Method for producing a flattened section on a coil for an electrical machine and a separately excited electrical synchronous machine

[0003] The invention relates to an electrical machine according to the preamble of claim 1. The invention relates in particular to a method for producing a flattened section on a coil for an electrical machine and further in particular to a separately excited synchronous electrical machine having such an electrical machine.

[0004] An electrical machine of the type mentioned above is known, for example, from document DE 10 2013 010 578 A1. The electrical machine comprises a stator with a primary coil and a rotor with a secondary coil mounted on the stator for rotational adjustment. During operation of the electrical machine, the secondary coil is inductively coupled to the primary coil, so that electrical energy is transferred from the primary coil to the secondary coil or vice versa. The known electrical machine is relatively large, particularly due to an electrical return line running along the secondary coil, which is undesirable.

[0005] Furthermore, the documents US 6,598,824 B2, DE 2 000 672 A1 , FR 2 262 386 A1 , EP 1 914 762 B1 , US 8,525,625 B2 and EP 33 29 739 B1 disclose various coils.

[0006] The object of the invention is to provide an improved or at least different embodiment for an electrical machine. In the present invention, this object is achieved in particular by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims and the description.

[0007] The invention has recognized that an electrical machine can be made more compact by flattening a connecting line of a coil, which runs along the winding of the coil and is therefore also referred to as a return line.

[0008] Accordingly, an electrical machine, in particular a rotary transformer for a separately excited synchronous electrical machine, is proposed, which has a stator with a primary coil and a rotor with a secondary coil that is rotatably adjustable, for example on the stator or a housing of the electrical machine. The secondary coil is inductively coupled or can be inductively coupled to the primary coil during operation of the electrical machine, so that electrical energy is or can be transferred from the primary coil to the secondary coil. Furthermore, it is provided that the primary coil and / or the secondary coil has a cylindrical winding defining a longitudinal center axis and two connecting leads. The two connecting leads can be connected to the winding in one piece. The two connecting leads are expediently designed to provide simple electrical contact between the primary coil and the secondary coil, respectively.Furthermore, it is provided that a first connecting line, hereinafter referred to as the return line, of the two connecting lines of the primary coil and / or the secondary coil runs along the winding and has a line cross-section. Essential to the invention is that the return line has a flattened section in which a height of the line cross-section of the return line, which runs in a first transverse direction oriented transversely, in particular perpendicularly, to the longitudinal center axis, is smaller than a width of the line cross-section, which runs in a second transverse direction oriented transversely, in particular perpendicularly, to the longitudinal center axis and transversely, in particular perpendicularly, to the first transverse direction.

[0009] As a result, the flattened section of the return line is designed to be flattened, so to speak, which has the advantage that the winding requires relatively little installation space in the first transverse direction and / or radially to the longitudinal center axis. This has the particular advantage that the proposed electrical machine can be provided overall more compactly than previously known electrical machines. For example, a groove-like recess for accommodating the return line on a supporting structure of the electrical machine, for example, a transformer core or preferably a ferrite core, can also be relatively small.

[0010] The proposed electrical machine can, in particular, implement a rotary transformer for a separately excited synchronous machine. The rotary transformer can be used for the contactless transmission of an excitation current to the rotor of a separately excited synchronous machine, which is preferably designed as a traction motor for a vehicle. The proposed electrical machine could alternatively implement another rotating machine, preferably a motor or a generator.

[0011] The primary coil is expediently constructed from a continuous, electrically conductive conductor. Accordingly, the winding of the primary coil and the connecting leads of the primary coil are connected to one another in one piece. The electrically conductive conductor of the primary coil can preferably be formed from several electrically conductive individual wires, resulting in good formability of the electrically conductive conductor of the primary coil. Alternatively, the electrically conductive conductor of the primary coil can be formed from a single electrically conductive wire.

[0012] The above can apply analogously to the secondary coil. Accordingly, the secondary coil is expediently constructed from a continuous, electrically conductive conductor. As a result, the winding of the secondary coil and the connecting leads of the secondary coil are connected to one another in one piece. The electrically conductive conductor of the secondary coil can preferably be formed from several electrically conductive individual wires, resulting in good formability of the electrically conductive conductor of the secondary coil. Alternatively, the electrically conductive conductor of the secondary coil can be formed from a single electrically conductive wire.

[0013] The cylindrically shaped winding can expediently have a round or polygonal, in particular rectangular, winding cross-section

[0014] The cable cross-section is expediently oriented transversely and, in particular, at right angles to a main direction of extension of the return line. The main direction of extension of the return line can run parallel to the longitudinal center axis of the winding, at least in sections and, in particular, in the area of ​​the winding.

[0015] It can expediently be provided that the height of the line cross-section of the return line in the flattened section is a maximum of 50% of the width of the line cross-section of the return line in the flattened section. Additionally or alternatively, it can be provided that the height of the line cross-section of the return line in the flattened section is a minimum of 25% of the width of the line cross-section of the return line in the flattened section. With appropriate dimensioning, the return line is constructed relatively compactly as desired and at the same time has sufficient mechanical stability, for example for assembly purposes. In particular, it can be provided that the height of the line cross-section of the return line in the flattened section is a maximum of 1.0 mm and the width of the line cross-section of the return line in the flattened section is 3.2 mm.This provides a preferred embodiment for the line cross-section of the return line of the primary coil and / or the secondary coil.

[0016] Furthermore, it can be provided that the cable cross-section of the return line in the flattened section is rectangular or oval. In this case, a cable cross-section of the return line in a section that is not the flattened section can, for example, be round. This gives the return line an advantageous cable cross-section, allowing the proposed electric machine to be compact.

[0017] It can expediently be provided that the flattened section of the return line extends completely or at least partially over the return line. The proposed flattening of the line cross-section of the return line thus extends completely over the entire length of the return line or, alternatively, only over a predetermined section of the entire length of the return line. The entire length of the return line can, for example, be defined by the extension of the return line in a main extension direction of the return line. Thus, the return line is compact over its entire length or, if the proposed flattening is only partially formed on the return line, can advantageously be provided cost-effectively.

[0018] Furthermore, it can expediently be provided that the flattened section of the return line is designed as a flat wire. This provides an advantageous shape for the flattened section of the return line. In particular, it can be provided that the flattened section of the return line has a contacting section of the return line designed to establish an electrical connection. Additionally or alternatively, it can be provided that the contacting section of the return line is a free line end of the return line and forms a flat cable connection for electrical contact, in particular a flat cable lug, by deformation, for example pressing. As a result, the return line can be electrically contacted relatively easily, for example connected to a voltage source.Said flat cable connection can be formed, in particular pressed, in such a way that its mechanical strength is increased compared to the mechanical strength of the remaining return line. This allows the flat cable connection to be screwed or clamped, for example. The flat cable connection can have at least one opening passing through the flat cable connection for receiving a fastening screw or the like. The flat cable connection can have a flat cable connection height in the first transverse direction and a flat cable connection width in the second transverse direction, wherein the flat cable connection height is preferably smaller than the flat cable connection width and the width of the line cross-section of the return line in the flattened section.

[0019] It can expediently be provided that the return line runs along the winding parallel or at least substantially parallel to the longitudinal center axis. Furthermore, the flattened section of the return line and the winding can be arranged adjacent to one another in the first transverse direction. It can also be provided that the flattened section of the return line extends completely or at least partially over an axial length of the winding. The axial length of the winding is expediently determined by the extent of the winding in the direction of the longitudinal center axis. The return line and the winding are expediently evenly spaced from one another in the direction of the first transverse direction, ie in particular that a distance in the direction of the first transverse direction between the return line and, for example, the longitudinal center axis of the winding is set constant.This provides an advantageous arrangement of winding and return line, which can provide a compact electrical machine.

[0020] Furthermore, it can be expediently provided that the winding has an inner circumferential side facing the longitudinal center axis and an outer circumferential side opposite the inner circumferential side and facing away from the longitudinal center axis. The return line can run radially inward along the inner circumferential side of the winding or, alternatively, radially outward along the outer circumferential side of the winding. Furthermore, according to the understanding of the invention, the winding of the primary coil and / or the winding of the secondary coil expediently has at least one or preferably several turns that extend at least partially and preferably completely around the respective longitudinal center axis.

[0021] In a preferred embodiment of the electrical machine, the winding can be realized as a single-layer winding or a multi-layer winding. In a single-layer winding, the winding turns formed by the electrical conductor run adjacent to one another in the direction of the longitudinal center axis and are not arranged in layers in the radial direction or in the direction of the first transverse direction. In a multi-layer winding, the winding turns formed by the electrical conductor run adjacent to one another in the direction of the longitudinal center axis and are arranged in layers in the radial direction or in the direction of the first transverse direction.It can expediently be provided that the winding has two opposing axial end faces, wherein a contacting section of the return line, configured to establish an electrical connection, is arranged on the same axial end face of the winding as a contacting section of the second connecting line, hereinafter referred to as the supply line, configured to establish an electrical connection. This provides a preferred, particularly cost-effective design for the primary coil and / or the secondary coil.

[0022] In particular, it can be provided that the flattened section of the return line and the winding are arranged adjacent to one another in the first transverse direction. In this case, the winding has turns with turning cross-sections, wherein the turning cross-sections of turns arranged directly adjacent to the flattened section of the return line in the first transverse direction each have a first height in the first transverse direction that is smaller than second heights of turning cross-sections of turns that are not directly adjacent to the flattened section of the return line. In other words, the winding is designed to be partially flattened, in particular such that the turns of the winding arranged on the flattened section of the return line or in the region of the flattened section of the return line have turning cross-sections with reduced heights.Together with the flattened section of the return line, which is also flattened, the primary coil and / or the secondary coil can be constructed relatively compactly radially with respect to the longitudinal center axis and / or with respect to the first transverse direction.

[0023] In a preferred embodiment of the electrical machine, it can be provided, for example, that the sum of a said first height of a turn of the winding and the height of the line cross-section of the return line in the flattening section is identical or substantially identical to a height of the second connecting line, referred to as the supply line, running in the direction of the first transverse direction.

[0024] Furthermore, it can expediently be provided that the second connecting line, hereinafter referred to as the supply line, has a supply line cross-section. The supply line cross-section can have a height running in the direction of the first transverse direction, wherein the height of the line cross-section of the return line in the flattened section is a maximum of 50% of the height of the supply line cross-section of the supply line. Additionally or alternatively, the height of the line cross-section of the return line in the flattened section can be a minimum of 25% of the height of the supply line cross-section of the supply line. Furthermore, the supply line can preferably have a round supply line cross-section. In other words, the line cross-section of the supply line is not flattened. As a result, the line cross-section of the flattened section has a height designed with respect to the height of the supply line cross-section of the supply line.

[0025] It can expediently be provided that the electrical machine has a primary coil support structure, for example a transformer core or preferably a ferrite core, with a recess for receiving the return line of the primary coil and / or a secondary support structure, for example a transformer core or preferably a ferrite core, with a recess for receiving the return line of the secondary coil. In this case, a depth of the recess running in the first transverse direction for receiving the return line of the primary coil can be smaller than a width of the recess running in the second transverse direction for receiving the return line of the primary coil. Furthermore, a depth of the recess running in the first transverse direction for receiving the return line of the secondary coil can be smaller than a width of the recess running in the second transverse direction for receiving the return line of the secondary coil.As a result, the recess in the primary coil support structure for accommodating the return line of the primary coil, for example, a longitudinal groove, is relatively compact in the first transverse direction. Furthermore, the recess in the secondary coil support structure for accommodating the return line of the secondary coil, for example, a longitudinal groove, can be relatively compact in the first transverse direction. This allows for the provision of an overall compact electrical machine.

[0026] According to a further basic idea of ​​the invention, a method for producing a flattened section on a coil for an electrical machine, in particular the primary coil and / or the secondary coil of the electrical machine according to the preceding description, is proposed. Within the scope of the method, it is provided that

[0027] - a coil made of a continuous conductor comprising a plurality of electrically conductive individual wires, in particular the primary coil and / or the secondary coil according to the preceding description, is provided with a single-layer or multi-layer, cylindrical winding defining a longitudinal center axis and two connecting leads,

[0028] - wherein a first connecting line, hereinafter referred to as the return line, is provided with an unprocessed line cross-section which has a height extending in a first transverse direction oriented transversely, in particular perpendicularly, to the longitudinal center axis and a second transverse direction width extending transversely, in particular perpendicularly, to the longitudinal center axis and transversely, in particular perpendicularly, to the first transverse direction,

[0029] - whereby an electrical insulation of the conductor is removed in a planned flattening section of the return line,

[0030] - wherein the electrically conductive individual wires of the conductor are untwisted in the planned flattening section and arranged parallel or substantially parallel to each other,

[0031] - wherein the electrically conductive individual wires of the conductor are flattened in the planned flattening section by forming, in particular pressing, in such a way that the height of the line cross-section of the return line in the first transverse direction is smaller than the width of the line cross-section in the second transverse direction,

[0032] - wherein an insulator for electrical insulation is then applied to the electrically conductive individual wires of the conductor in the flattened section.

[0033] This allows the proposed flattening section of the return line to be implemented efficiently and, for example, cost-effectively.

[0034] According to a further basic concept of the invention, a separately excited synchronous machine, in particular a traction motor for a vehicle, is proposed, which comprises an electric machine according to the preceding description. The electric machine is expediently designed as a rotary transformer configured for contactless transmission of an excitation current to the rotor of the separately excited synchronous machine.

[0035] In summary, the present invention preferably relates to an electrical machine with a stator having a primary coil and a rotatably adjustable rotor having a secondary coil that interacts inductively with the primary coil. The primary coil and / or the secondary coil have a winding with two connecting lines, of which the first connecting line is referred to as the return line. The return line runs along the winding and has a line cross-section. It is essential for the invention that the return line has a flattened section in which a height of the line cross-section of the return line in a first transverse direction is smaller than a width of the line cross-section in a second transverse direction. The invention relates in particular to a method for producing a flattened section on a coil for an electrical machine.

[0036] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0037] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0038] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein like reference numerals refer to like or similar or functionally identical components.

[0039] They show, schematically

[0040] Fig. 1 is a sectional view of a preferred embodiment of an electrical machine,

[0041] Fig. 2 shows a sectional view of a preferred embodiment of a primary or secondary coil of the electrical machine from Fig. 1,

[0042] Fig. 3 the primary or secondary coil of the electrical machine from Fig.

[0043] 2 with a view according to an arrow III shown in Fig. 2, Fig. 4 in a sectional view a further preferred embodiment of a primary or secondary coil of the electrical machine from Fig. 1,

[0044] Fig. 5 shows a sectional view of another preferred embodiment of a primary or secondary coil of the electrical machine from Fig. 1,

[0045] Fig. 6 shows a perspective view of a contacting section of a return line of another preferred embodiment of a primary or secondary coil of the electrical machine from Fig. 1,

[0046] Fig.7 to 9 method steps of a method for producing a flattened section on a primary coil and / or secondary coil of the electrical machine from Fig. 1.

[0047] Fig. 1 shows a preferred embodiment of an electrical machine, designated overall by the reference numeral 1, designed as a rotary transformer, which is installed in a separately excited synchronous machine (not discussed in more detail) and is configured for contactless transmission of an excitation current to a rotor 4. The electrical machine 1 has a stator 2 with a primary coil 3 and a rotor 4, which is rotatably mounted on the stator 2 and has a secondary coil 5. During operation of the electrical machine 1, the secondary coil 5 is inductively coupled to the primary coil 3, so that electrical energy is transferred in a manner known per se from the primary coil 3 to the secondary coil 5, or vice versa. Furthermore, the secondary coil 5 of the rotor 4 is electrically coupled to an excitation coil of the rotor 4. The primary coil 3 is accommodated in a primary coil support structure 30, for example a transformer core or preferably a ferrite core.Furthermore, the secondary coil 5 is accommodated in a secondary support structure 31, for example a transformer core or preferably a ferrite core.

[0048] Fig. 2 to 5 each show a preferred embodiment of a primary or secondary coil 3, 5 of the electrical machine 1 from Fig. 1, wherein it can be seen that the primary coil 3 and / or the secondary coil 5 has a cylindrical winding 6 defining a longitudinal center axis 7 and two connecting lines 8, 9 integrally connected to the winding 6.

[0049] The primary coil 3 and / or the secondary coil 5 is, as can be seen particularly in Fig. 8, constructed from a continuous, electrically conductive conductor 15 formed from several electrically conductive individual wires 16. Accordingly, the winding 6 and the connecting leads 8, 9 of the primary coil 3 and / or the secondary coil 5 are integrally connected to one another.

[0050] The winding 6 is designed in Figs. 2 to 5 as a single-layer winding 6 and has an inner circumferential side 19 facing the longitudinal center axis 7 and an outer circumferential side 20 opposite the inner circumferential side 19 and facing away from the longitudinal center axis 7, as well as two axial end faces 21a, 21b opposite one another in the direction of the longitudinal center axis 7.

[0051] The first connecting line 9 is referred to herein as the return line, which is due to the fact that it runs parallel to the longitudinal center axis 7 along the winding 6. In Figs. 2 and 5, it is specifically provided that the return line 9 runs radially outward along the outer circumferential side 20 of the winding 6 along the winding 6. A distance can be established between the outer circumferential side 20 of the winding 6 and the return line 9. Alternatively, the return line 9 can be supported in contact with the outer circumferential side 20 of the winding 6. In Fig. 4, as an alternative, it is provided that the return line 9 runs radially inward along the inner circumferential side 19 of the winding 6 along the winding 6. In this case, a distance can be established between the inner circumferential side 19 of the winding 6 and the return line 9, or the return line 9 can be supported in contact with the inner circumferential side 19 of the winding 6.

[0052] Furthermore, it can be seen in Figs. 2 to 5 that the return line 9 and the second connecting line 8, referred to herein as the supply line, terminate in the same axial end face 21a of the winding 6 and each form a free line end 40, 44 there. To establish an electrical connection between the primary coil 3 and / or the secondary coil 5, for example, with a voltage source (not illustrated), it can be provided that the return line 9 or its free line end 40 has a contacting section 18 of the return line 9 and the supply line 8 or its free line end 44 has a further contacting section 38. The contacting sections 18, 38 are each designed to establish an electrical connection.

[0053] In order for the proposed electrical machine 1 to be compact in a radial direction running through the longitudinal center axis 7 or in a first transverse direction 13 oriented transversely and in particular perpendicularly to the longitudinal center axis 7, it is provided that the return line 9 has a line cross-section 10 and a flattened section 39, see in particular Figs. 2 to 5. It is provided that in the flattened section 39, a height 11 of the line cross-section 10 of the return line 9, which runs in the first transverse direction 13, is smaller than a width 12 of the line cross-section 10, which runs in a second transverse direction 14 oriented transversely, in particular perpendicularly, to the longitudinal center axis 7 and transversely, in particular perpendicularly, to the first transverse direction 13. The line cross-section 10 of the return line 9 in the flattened section 39 can preferably be rectangular or oval, see Fig. 3. Furthermore, in the present embodiments according to Fig.2 to 5, it is provided that the flattened section 39 and the winding 6 are arranged adjacent to one another in the first transverse direction 13 and the flattened section 39 extends completely over an axial length 42 of the winding 6, which is to be determined in the direction of the longitudinal center axis 7. The supply line 8 has a supply line cross-section 27. The supply line cross-section 27 of the supply line 8 has a height 28 running in the direction of the first transverse direction 13, which is greater than the height 11 of the line cross-section 10 of the return line 9 in the flattened section 39. As a result, the flattened section 39 of the return line 9 is designed to be flattened, so to speak, which has the advantage that the winding 6 requires relatively little installation space in the direction of the first transverse direction 13.

[0054] 2 to 5, it is further provided that the winding 6 has a plurality of turns 43 which run helically in the direction of the longitudinal center axis 7 and which each have a turn cross-section 22. While in the embodiments according to FIGS. 2 to 4 the turn cross-sections 22 of the turns 43 are of constant area throughout, according to the embodiment according to FIG. 5, the turn cross-sections 22 of turns 43 which are arranged in the first transverse direction 13 directly adjacent to the flattened section 39 of the return line 9 each have a first height 24 in the first transverse direction 13. The first heights 24 of these turn cross-sections 22 are smaller than second heights 26 of turn cross-sections 22 of turns 43 which are not arranged directly adjacent to the flattened section 39 of the return line 9. As a result, the winding 6 is, so to speak, partially flattened.

[0055] According to Fig. 6, it is provided that the above-described contacting section 18 of the return line 9 or the free line end 40 of the return line 9 is formed into a flat cable connection 41 by forming, such as pressing. The flat cable connection 41 is configured for electrical contact and, purely by way of example, has an opening 45 passing through the flat cable connection 41 for receiving a fastening screw (not illustrated) or the like.

[0056] 7 to 9 show some method steps of a method for producing a flattened section 39 of the return line 9 of the primary coil 3 and / or the secondary coil 5 of the electrical machine 1 from Fig. 1. Within the scope of the proposed method, it is provided that firstly a primary coil 3 and / or secondary coil 5 is provided, which is made from a continuous conductor 15 having a plurality of electrically conductive individual wires 16 and has a single-layer, cylindrical winding 6 defining a longitudinal center axis 7 and two connecting lines 8, 9. A first connecting line 9, referred to as the return line, has an unprocessed line cross-section which has a height 11 running in a first transverse direction 13 oriented transversely to the longitudinal center axis 7 and a width 12 running in a second transverse direction 14 oriented transversely to the longitudinal center axis 7 and transversely to the first transverse direction 13.Then, an electrical insulation of the conductor 15 is removed in a planned flattening section 39 of the return line 9, see Fig. 7. Subsequently, the electrically conductive individual wires 16 of the conductor 15 are untwisted in the planned flattening section 39 and arranged parallel or substantially parallel to one another, see Fig. 8. Then, the electrically conductive individual wires 16 of the conductor 15 are flattened in the planned flattening section 39 by forming, in particular pressing, in such a way that the height 11 of the line cross-section 10 of the return line 9 in the first transverse direction 13 is smaller than the width 12 of the line cross-section 10 in the second transverse direction 14, see Figs. 8 and 9. Furthermore, an insulator for electrical insulation is applied to the electrically conductive individual wires 16 of the conductor 15 in the flattening section 39, see Figs. 8 and 9.

Claims

Claims 1. Electrical machine (1), in particular a rotary transformer for a separately excited synchronous electrical machine, - with a stator (2) having a primary coil (3) and a rotatably adjustable rotor (4) having a secondary coil (5), - wherein the secondary coil (5) is inductively coupled to the primary coil (3) during operation of the electrical machine (1), so that electrical energy is transferred from the primary coil (3) to the secondary coil (5), - wherein the primary coil (3) and / or the secondary coil (5) has a cylindrical winding (6) defining a longitudinal center axis (7) and two connecting lines (8, 9), - wherein a first connecting line (9), hereinafter referred to as the return line, runs along the winding (6) and has a line cross-section (10), characterized in that - the return line (9) has a flattening section (39) in which a height (11) of the line cross-section (10) of the return line (9), which runs in a first transverse direction (13) oriented transversely to the longitudinal center axis (7), is smaller than a width (12) of the line cross-section (10), which runs in a second transverse direction (14) oriented transversely to the longitudinal center axis (7) and transversely to the first transverse direction (13).

2. Electrical machine (1) according to claim 1, characterized in that - the height (11) of the line cross-section (10) of the return line (9) in the flattened section (39) is a maximum of 50% of the width (12) of the line cross-section (10) of the return line (9) in the flattened section (39) and / or - the height (11) of the line cross-section (10) of the return line (9) in the flattening section (39) is at least 25% of the width (12) of the line cross-section (10) of the return line (9) in the flattening section (39).

3. Electrical machine (1) according to claim 1 or 2, characterized in that - the height (11) of the line cross-section (10) of the return line (9) in the flattened section (39) is a maximum of 1 mm and the width (12) of the line cross-section (10) of the return line (9) in the flattened section (39) is 3.2 mm.

4. Electrical machine (1) according to one of the preceding claims, characterized in that - the line cross-section (10) of the return line (9) in the flattened section (39) is rectangular or oval.

5. Electrical machine (1) according to one of the preceding claims, characterized in that - the flattened section (39) of the return line (9) extends completely or at least partially over the return line (9).

6. Electrical machine (1) according to one of the preceding claims, characterized in that - the flattened section (39) of the return line (9) has a contacting section (18) of the return line (9) designed to establish an electrical connection, and / or - the contacting section (18) of the return line (9) has a free line end (40) of the return line (9) and by forming a flat cable connection (41) for electrical contact.

7. Electrical machine (1) according to one of the preceding claims, characterized in that - the return line (9) runs along the winding (6) parallel or at least substantially parallel to the longitudinal center axis (7), and / or - the flattened section (39) of the return line (9) and the winding (6) are arranged adjacent to one another in the first transverse direction (13), and / or - the flattened section (39) of the return line (9) extends completely or at least partially over an axial length (42) of the winding (6).

8. Electrical machine (1) according to one of the preceding claims, characterized in that - the winding (6) has an inner circumferential side (19) facing the longitudinal center axis (7) and an outer circumferential side (20) opposite the inner circumferential side (19) and facing away from the longitudinal center axis (7), - wherein the return line (9) runs radially inward along the inner circumferential side (19) of the winding (6) on the winding (6), or - wherein the return line (9) runs radially outwardly along the outer circumferential side (20) of the winding (6) on the winding (6).

9. Electrical machine (1) according to one of the preceding claims, characterized in that - the winding (6) is realized by a single-layer winding (6) or a multi-layer winding (6).

10. Electrical machine (1) according to one of the preceding claims, characterized in that - the winding (6) has two opposite axial end faces (21a, 21b), - wherein a contacting section (18) of the return line (9) designed to establish an electrical connection is arranged on the same axial end face (21a, 21b) of the winding (6) as a contacting section (38) of the second connecting line (8, 9) designated as the supply line (8), designed to establish an electrical connection. 11 . Electrical machine (1) according to one of the preceding claims, characterized in that - the flattened section (39) of the return line (9) and the winding (6) are arranged adjacent to one another in the first transverse direction (13), - the winding (6) has turns (43) with turn cross-sections (22), - wherein the winding cross-sections (22) of windings (43) which are arranged in the first transverse direction (13) immediately adjacent to the flattened section (39) of the return line (9) each have a first height (24) in the first transverse direction (13) which is smaller than second heights (26) of winding cross-sections (22) of windings (43) which are not immediately adjacent to the flattened section (39) of the return line (9).

12. Electrical machine (1) according to one of the preceding claims, characterized in that - the second connecting line (8), hereinafter referred to as the supply line, has a supply line cross-section (27), - wherein the supply line cross-section (27) has a height (28) extending in the direction of the first transverse direction (13), - wherein the height (11) of the line cross-section (10) of the return line (9) in the flattening section (39) is a maximum of 50% of the height (28) of the supply line cross-section (27) of the supply line (8), and / or - wherein the height (11) of the line cross-section (10) of the return line (9) in the flattened section (39) is at least 25% of the height (28) of the supply line cross-section (27) of the supply line (8).

13. Electrical machine (1) according to one of the preceding claims, characterized in that - the electrical machine (1) has a primary coil support structure (30) with a recess for receiving the return line (9) of the primary coil (3), and / or - the electrical machine (1) has a secondary support structure (31) with a recess for receiving the return line (9) of the secondary coil (5), - wherein a depth of the recess for receiving the return line (9) of the primary coil (3) extending in the first transverse direction (13) is smaller than a width of the recess for receiving the return line (9) of the primary coil (4) extending in the second transverse direction (14), and / or - wherein a depth of the recess for receiving the return line (9) of the secondary coil (5) extending in the first transverse direction (13) is smaller than a width of the recess for receiving the return line (9) of the secondary coil (5) extending in the second transverse direction (14).

14. Method for producing a flattened section on a coil for an electrical machine, in particular implemented as a rotary transformer, in particular the primary coil (3) and / or the secondary coil (5) of the electrical machine (1) according to one of the preceding claims, - in the framework of which a coil made of a continuous conductor (15) comprising several electrically conductive individual wires (16), in particular the primary coil (3) and / or the secondary coil (5) according to a of the preceding claims, with a single-layer or multi-layer, cylindrical winding (6) defining a longitudinal center axis (7) and two connecting lines (8, 9), - wherein a first connecting line (9), hereinafter referred to as the return line, is provided with a line cross-section which has a height (11) extending in a first transverse direction (13) oriented transversely to the longitudinal center axis (7) and a width (12) extending in a second transverse direction (14) oriented transversely to the longitudinal center axis (7) and transversely to the first transverse direction (13), - wherein an electrical insulation of the conductor (15) is removed in a planned flattening section (39) of the return line (9), - wherein the electrically conductive individual wires (16) of the conductor (15) are untwisted in the planned flattening section (39) and arranged parallel or substantially parallel to one another, - wherein the electrically conductive individual wires (16) of the conductor (15) are flattened in the planned flattening section (39) by forming, in particular pressing, in such a way that the height (11) of the line cross-section (10) of the return line (9) in the first transverse direction (13) is smaller than the width (12) of the line cross-section (10) in the second transverse direction (14), - wherein an insulator for electrical insulation is then applied to the electrically conductive individual wires (16) of the conductor (15) in the flattened section (39).

15. Separately excited electrical synchronous machine, in particular a traction motor for a vehicle, comprising an electrical machine (1), in particular a rotary transformer, according to one of the preceding claims 1 to 13.

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