Conductor for an electric machine

Abstract

The invention relates to a conductor (2) for an electric machine, comprising: a first winding element (3) made of an electrically conductive material and having a channel (7) through which a coolant can flow, the first winding element (3) being integrally formed with a first straight portion (8), a reverse portion (10), and a second straight portion (9) parallel to the first straight portion (8), wherein the first straight portion (8) has a first end section (12) and the second straight portion (9) has a second end section (13); a hollow connecting member (6) made of an electrically conductive material; wherein the hollow connecting member (6) and the first end section (12) of the winding element (3) are axially insertable into each other to form an axially overlapping electrical and fluid connection. The invention further relates to an electric machine (25) having such a conductor (2).

Description

Technical Field

[0001] The invention relates to a hollow winding element for an electric motor. The electric motor may be any type of motor having a wound stator. In particular, it is a permanent magnet synchronous motor, an induction motor, a field rotor synchronous motor or a switched reluctance motor. An electric motor is an electric motor which generally comprises a stator and a rotor. The stator carries a winding which is connected to an alternating current (AC) power source to generate a rotating magnetic field. Background Art

[0002] Document US2021 / 0249926 A1 discloses a coil skeleton that is attached to the stator core of a distributed winding radial gap type rotating electric machine and includes a tooth holding portion and a slot insulator made of an insulator. The tooth holding portion has: a first wall surface that covers a first circumferential side surface of a tooth of the stator core; a second wall surface that covers at least a portion of a second circumferential side surface of the tooth; and a third wall surface that covers two side surfaces in the axial direction of the tooth. The slot insulator is integrally formed with the first wall surface of the tooth holding portion and has a plurality of through holes extending in the axial direction and arranged in the radial direction.

[0003] From DE 10 2020 114 683 A1, an active part for an electric machine is known comprising a current conducting winding for generating a magnetic flux and an active part iron for holding the current conducting winding to conduct the magnetic flux of the winding. The active part iron has a plurality of axially extending grooves on the circumference, in which winding conductors are arranged. The winding conductors are formed as hollow conductors, thereby forming cooling channels for a coolant for cooling the active part. The winding is designed as a wave winding with an integral winding conductor.

[0004] From the document US2021 0091619A1 corresponding to WO 2019 038139A1, it is known that a winding assembly is to be inserted into one or more grooves of an electric machine. The winding assembly is in the shape of a hairpin, which is inserted into the groove of the electric machine. The winding assembly comprises two protrusions and a curved transition zone, which connects the two protrusions to each other. The protrusions each have: a first portion having a profile adjusted to the cross section of the groove; and an end portion having a circular profile. The winding assembly is formed as a hollow conductor having a through-channel through which a coolant can be discharged.

[0005] There are some known direct oil cooling solutions to cool the windings of a PMSM. Typically, these solutions focus on the end windings, while the active windings within the stator stack are kept relatively far away from any cooling source. As a result, the heat on the active windings is higher, with the conductor layer closest to the air gap containing the hot spots. Additionally, there are some solutions for active winding cooling, but all of them are away from the hot spots. Summary of the invention

[0006] The object of the present invention is to provide a conductor for an electric machine with an effective cooling structure which can be easily produced and cost-effectively. The object is further to provide an electric machine with such a conductor.

[0007] According to the invention, a conductor to be inserted into a slot of an electric machine is proposed, comprising: a first winding element made of a conductive material, as a hollow conductor with a channel through which a coolant can flow, wherein the first winding element comprises a first straight portion, a reverse portion, and a second straight portion parallel to the first straight portion, which are formed integrally, wherein the first straight portion has a first end section and the second straight portion has a second end section; a hollow connecting member made of a conductive material; wherein the hollow connecting member and the first end section of the winding element can be axially inserted into each other to form an axially overlapping electrical and fluid connection. The first straight portion, the reverse portion and the second straight portion form one piece, i.e., they are parts of the same winding element. The winding element can be described as hairpin-shaped.

[0008] The advantage of this conductor is that the hollow winding elements and the hollow connecting members can act as electrical conductors, wherein a coolant flow circulates inside these electrical conductors. For example, the cooling fluid can be oil or an oil-based fluid. The conductor consisting of a plurality of winding elements and the hollow members connecting them can be fed with a cooling fluid so that the winding can be cooled directly at the source of the heat losses it generates. This is a very efficient way to cool the windings, since the loss generation center point is solved.

[0009] The conductor is made of a plurality of single winding elements, which may also be referred to as conductor elements or hairpin elements. The two winding elements are connected to each other via corresponding connecting members. According to a first option, the connecting member may be a separate component, which is introduced into both adjacent winding elements in order to obtain mechanical, electrical and fluid connections. The connection may be established very easily by a simple insertion movement in the axial direction. No further connection means, such as welding, are required. The two winding elements are connected to each other on their straight portions using a connecting member, which may also be referred to as a tube or sleeve member. According to a second option, the connecting member may also be a part of the second winding element. In this case, the first winding element and the second winding element are directly inserted into each other. The two connected winding elements are arranged in the same slot of the stator and may have the same layer span and / or bending geometry.

[0010] Another advantage is that the tube component and the winding element(s) can be easily connected to one another by a simple plug-in connection. As mentioned above, welding is not required, which reduces process and time costs. Furthermore, since the connection is arranged in the slot of the motor, the reverse section of the winding element can be shaped as required with a particularly small overall length of the motor.

[0011] The hollow connecting member can be connected to the first end section of the winding element by interference fit. In this way, a particularly safe mechanical, electrical and fluid connection is achieved. However, it is to be understood that the connecting member and the winding element can also be configured with a transition fit or a small play fit. The end portion of the tube member and / or the end face of the winding element can have a conical chamfer so that the tube member is easily inserted into the hole of the winding member. The axial length of the tube member can be at least 0.1 times, in particular at least 0.2 times, the length of the first straight portion of the winding element. This contributes to a safe connection.

[0012] According to an embodiment, the wall thickness of the tube member may be smaller than the wall thickness of the winding element.

[0013] The end section of the winding element may have a connection hole extending from the end face of the winding element to the stop face. The hole forms an internal aperture which may be machined into the end section of the winding element so as to have a larger cross section than the passage of the winding element. Or, in other words, the inner diameter of the hole may be larger than the inner diameter of the passage of the winding element at a section adjacent to the end section. The connection tube may be inserted into the hole until it abuts axially against the stop face of the winding element. The connection tube may then be inserted into the second winding element with its other end.

[0014] The outer diameter of the connecting member can be larger than the inner diameter of the channel of the winding element. The connecting member has a minimum inner diameter, for example, the minimum inner diameter can be greater than 0.9 times the minimum inner diameter of the channel of the winding element and / or less than 1.1 times the minimum inner diameter of the channel of the winding element. In this way, any change in the cross section of the channel along the connection is small, and therefore any pressure jump is small. This contributes to a good flow of the cooling fluid through the channel. Preferably, the cross section and / or diameter of the channel is substantially constant along the connection area between the tube element and the winding element, so that a smooth flow is achieved.

[0015] The connecting member and / or the winding element may be made of copper, aluminum, stainless steel, or an alloy comprising at least one of copper, aluminum and stainless steel. The materials of the connecting member and the winding element may preferably be selected so that the difference between the thermal expansion coefficient of the material of the connecting member and the thermal expansion coefficient of the material of the winding element is less than 10% of the friction coefficient of either material.

[0016] According to a first embodiment, the second winding element can be provided with the same structure as the first winding element, wherein the first winding element and the second winding element are connected to each other via a hollow connecting member. On one side, the connecting member is axially inserted into the first end section of the first winding element, and on the other side, it is axially inserted into the second end section of the second winding element. The conductor can consist of a plurality of first winding elements and second winding elements, which are connected to each other via a plurality of connecting members, wherein the conductor forms a continuous cooling channel with an inlet and an outlet.

[0017] According to a second embodiment, the channel may include a plurality of first and second winding elements, with a straight intermediate element arranged between them. In this case, the first winding element may be connected to the straight intermediate element via a hollow connecting member, wherein one side of the hollow connecting member is axially inserted into the end section of the first winding element, and the other side of the hollow connecting member is axially inserted into the straight intermediate element. The other end of the straight intermediate element is connected to another winding element via another hollow connecting member, and so on, to form a continuous conductor. Further details about the connection between the winding element and the straight element via the hollow connecting member can be configured as described above.

[0018] The cooling fluid can be supplied to the circuit on the terminal rack. The terminal rack can have blocks instead of plates for the terminals, which allows not only the inverter terminal connection but also the oil inlet. At the neutral point of the winding arrangement, the conductor can be terminated in an open terminal, spraying oil on the end winding and to the motor oil sump. Hydraulically, all parallel wires of all phases can be connected in parallel.

[0019] The above object is further achieved by an electric machine comprising a stator and a rotor, wherein the stator comprises a plurality of longitudinal slots distributed on a circumference, wherein a plurality of conductors are arranged in each longitudinal slot of the stator for generating an electromagnetic field, wherein at least two of the plurality of conductors are configured according to any one of the above embodiments. The slots extend in the longitudinal direction of the stator (i.e., in the axial direction) and may also be designated as grooves.

[0020] The advantages of this motor correspond to those described above in connection with the conductor. Direct cooling of the conductor core and / or the heat source is achieved. Assuming the same current density, this allows the motor to be operated at a lower temperature, thereby reducing the deterioration of the insulation system. Thus, for the same current density, a higher torque density of the motor can be obtained. To achieve maximum operating conditions, the current of the cooling fluid can be increased, resulting in improved continuous operating torque and speed envelopes, as well as higher peak torque and power.

[0021] According to an embodiment, the stator may comprise at least four conductors in each slot, wherein at least two of the plurality of conductors are configured as solid conductors. In other words, the motor may be provided with a partial number of hollow conductors configured according to the invention and a partial number of solid conductors. Preferably, at least one hollow conductor is arranged in each slot of the stator. The connecting pipes of the plurality of conductors are preferably arranged in a central plane, which is arranged between a first end face and an opposite second end face of the stator. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The preferred embodiments are described below with reference to the accompanying drawings. Figure 1A A conductor portion according to the invention is shown in a perspective view; Figure 1B An exploded view showing Figure 1A A connecting member of two winding elements; Figure 1C Shows Figure 1A an end section of a winding element of a conductor portion; Figure 1D Shows Figure 1A The connection area between two winding elements of the conductor section; Figure 2A The axial view shows Figure 1A The connecting members of the conductor parts are as details; Figure 2B Shown in side view Figure 2A connecting components; Figure 3A The stator of the electric machine is shown in an axial exploded view. Figure 1A The conductor part; Figure 3B The axial view shows Figure 3A stator and conductor parts; Figure 4 A conductor according to the present invention is shown, the conductor having a plurality of winding elements connected to each other to form a plurality of straight portions and reverse portions on a circumference; Figure 5A A three-dimensional exploded view of the stator of the electric machine is shown. Figure 4 Conductor; Figure 5B Shows Figure 4 and Figure 5A The inlet and outlet of the conductor as details; Figure 5C The 3D view shows the installed Figure 5A stator and conductors; Figure 6 An electric machine according to the invention is shown in an axial view, the electric machine having a plurality of conductors according to the invention; Fig. 7A The conductor part according to the invention in a second embodiment is shown in a perspective exploded view; Figure 7B A set of conductor sections is shown in a perspective exploded view; Figure 7C A conductor having a plurality of first and second winding elements and intermediate elements is shown in a perspective exploded view; Fig. 8A The exploded view shows the Figure 7B a stator having a plurality of conductor sections; Figure 8B The longitudinal cross-sectional view shows a Fig. 8A a stator having a plurality of conductor sections; Figure 8C Shown in a larger view Figure 8B Details of 8C. DETAILED DESCRIPTION

[0023] It will be described below Figures 1A to 1D A portion of a conductor 2 according to the invention is shown. The conductor 2 is to be mounted in a plurality of circumferentially distributed slots of a stator of an electrical machine (not shown here).

[0024] The conductor 2 comprises a plurality of winding elements 3, 4, 5 connected to each other via a connecting member 6. The connecting member 6 is Figure 2A and Figure 2B, and may also be referred to as a tube or sleeve member. The winding elements 3, 4, 5 and the connecting member 6 are made of an electrically conductive material. In the installed condition, they form a hollow conductor 2 having a channel 7 through which a coolant can flow. The conductor 2 thus has two functions, namely, conducting current and conducting coolant.

[0025] The winding elements 3, 4 can be made of copper, aluminum, stainless steel, or an alloy comprising at least one of copper, aluminum and stainless steel. The same applies to the material of the connecting member 6. The materials of the connecting member 6 and the winding elements 3, 4 are preferably selected so that the difference between the thermal expansion coefficient of the material of the connecting member and the thermal expansion coefficient of the material of the winding elements is less than 10% of the friction coefficient of one of the materials.

[0026] As a representative of several winding elements 3, 4 for the stator, one winding element 3 is described in more detail. The winding element 3 is in the shape of a hairpin, comprising a first straight portion 8, a second straight portion 9 parallel to the first straight portion, and a reverse portion 10 connecting the first straight portion 8 and the second straight portion 9 to each other. Figure 1B and Figure 1C As can be seen in the figure, the first straight section 8 and the second straight section 9 have a respective first end section 12 and a second end section 13, into which respective connecting members 6 can be axially inserted in order to connect the winding elements 3, 4 to each other. The connecting members 6 can be connected to the first winding element 3 and the second winding element 4 by means of an interference fit. In order to easily introduce the connecting members 6 into the respective winding elements 3, 4, any of the elements can optionally have a conical chamfer. In the mounted state, as Figure 1D As shown, an axially overlapping mechanical, electrical and fluid connection is formed by the elements 3, 4, 6. The axial length L7 of the connecting member 6 can be, for example, at least 0.1 times, in particular at least 0.2 times, the length L8 of the first straight portion 8 of the winding element 3. Thus, a secure axially overlapping connection is obtained. Figure 1D As can be seen in FIG. 4 , the wall thickness of the connecting member 6 can be smaller than the wall thickness of the winding elements 3 , 4 .

[0027] The end section 12 of the winding element 3 has a connecting hole 14, which extends from the end face 15 of the winding element to the stop surface 16. The hole 14 forms an internal aperture, which can be machined into the end section of the winding element 3 so as to have a cross section and / or diameter d14 that is larger than the cross section and / or diameter d7 of the passage 7 of the winding element. The stop surface 16 can act as a stop for the connecting member 6 to be inserted into the hole 14. The other end of the connecting member 6 is inserted into the hole of the adjacent winding element 4.

[0028] As in Figure 1D As can be seen in FIG. 1 , the outer diameter D6 of the connection member 6 is larger than the inner diameter d7 of the channel of the winding elements 3, 4. The inner diameter d6 of the connection member 6 corresponds substantially to the inner diameter d7 of the channel 7 of the winding elements, so that a good cooling flow is achieved without a pressure drop. The ratio between the inner diameter d6 of the connection member 6 and the inner diameter d7 of the channel 7 can be, for example, between 0.9 and 1.1, i.e. 0.9 <d6 / d7<1.1。

[0029] Figure 3A and Figure 3B The diagram shows a circuit having winding elements 3, 4, 5. Figure 1A The conductor 2 of the motor is provided with a stator core 20 of the motor. The stator core 20 is generally annular around a stator axis A20 and comprises a plurality of slots 21 distributed on an inner circumferential face 24 around the axis A20. The stator core 20 can be produced, for example, by laminating a plurality of electromagnetic steel sheets or soft magnetic materials. Figure 4 A complete conductor 2 consisting of a plurality of winding elements 3, 4, 5 and constituting an electrical and fluid channel is shown in FIG. The conductor 2 shown here includes 16 pairs of straight portions (8, 9) and reverse portions (10, 11) which form a serpentine structure on the circumference. The straight portions are to be arranged in corresponding slots 21 of the stator core 20, wherein a plurality of straight portions are accommodated in each slot. The reverse portions 10, 11 are arranged axially adjacent to the stator core 20 and span a plurality of slots in the circumferential direction. As shown in FIG. Figure 4 As can be seen in the drawings, each conductor 2 has an inlet 22 and an outlet 23, so that a cooling fluid can be supplied through the conductor circuit. The cooling fluid can be supplied to the circuit on a terminal frame (not shown).

[0030] Figure 5A , Figure 5B and Figure 5C In combination with the stator core 20, Figure 4 The complete winding structure used to form the complete stator of the motor can have Figure 4 There are 6 conductors 2 of the type shown. However, it is to be understood that this number is merely exemplary and that, depending on the number of slots arranged on the circumference and the number of conducting channels in each slot, the number of conductors may vary accordingly.

[0031] Figure 62 shows an electric machine 25 according to the present invention. The electric machine 25 includes a stator 26 and a rotor 27 coaxially arranged therein. The stator 26 includes a stator core 20 and a winding 28 composed of a plurality of conductors 2 according to the present invention. The electric machine 25 is configured in the form of a permanent magnet synchronous motor (PMSM). The winding 28 is connected to an AC power supply to generate a rotating magnetic field. The rotor 27 includes a rotor member 29 and a plurality of permanent magnets 30 embedded therein to generate a constant magnetic field. In an activated state, the rotor 27 rotates about a rotation axis A27 to drive a drive shaft 31 connected to the rotor member 29.

[0032] In this embodiment, the stator core 20 comprises 48 slots 21 on the circumference, wherein four conductor wires are arranged in each slot 21. However, it is to be understood that these numbers are merely exemplary, and stators with other numbers of slots and conductor wires are possible, which can be selected according to technical requirements.

[0033] The advantage of an electric machine 25 comprising a conductor 2 according to the invention is that the hollow winding elements 3, 4 and the connecting members 6 can act as both electrical conductors and cooling conductors. The conductor 2 can be fed with a cooling fluid so that the winding 28 can be cooled directly where heat is generated. The coolant can be fed by a high voltage connector and can leave at the neutral phase of the electric machine 25. The coolant can be collected or extracted to a heat exchanger, or it can be collected in a carter inside the electric machine, depending on whether a wet or dry motor design is provided. The coolant can be fed on a given parallel winding. The coolant feed can be implemented indistinctively for all phases in the motor at the first, second, third or fourth parallel line, thereby ensuring a balanced neutral voltage.

[0034] Further advantages and special features are: structure and construction are easy, which is well compatible with mass production and is therefore very cost-effective. The molded hollow winding elements 3, 4 are physically and electrically connected by means of a connecting member 6, which can robustly transmit the flow of coolant and current. The winding elements 3, 4 can be axially contacted to conduct current so as to form a supplementary current path to the channel cross section. In order to maximize the current transfer path, other shapes, such as cylindrical shapes, can be considered. As mentioned above, the connecting member 6 can be installed with a press-fit configuration using two half hairpins (hairpin halve), thereby ensuring interference (interference), and is intended to achieve perfect contact between the conductor 2 and the connecting sleeve. The manufacturing process is defined as allowing easy assembly. As required, the connecting member 6 can be located in the middle of the stator 25, or in different positions close to the end winding. In a modified embodiment, additional connecting sleeves can be realized to apply existing winding elements 3, 4 for different stacking lengths to form equipment. This may require, for example, two connections in the straight sides of the winding elements 3 , 4 .

[0035] Fig. 7A A portion of a conductor 2 according to the invention in a second embodiment is shown. The conductor portion corresponds broadly to the embodiment according to Figures 1 to 5, the description of which is referred to here with regard to similarity. Identical or corresponding details are provided with the same reference symbols as in the above figures.

[0036] The conductor 2 comprises a plurality of winding elements 3, 4 which are connected to one another by means of connecting members 6, 6' via intermediate elements 19. The winding elements 3, 4, the intermediate elements 19 and the connecting members 6, 6' are made of an electrically conductive material. In the installed state, they form a hollow conductor 2 having a channel 7 through which a coolant can flow.

[0037] according to Fig. 7A A characteristic feature of the embodiment of is that the conductor comprises not only the first winding 3 and the second winding 4, but also a straight intermediate element 19 to be inserted into the slots of the stator. Therefore, the straight parts 8, 9 of the first winding 3 and the second winding 4 are shorter than in the first embodiment. Apart from this, the structure and design of the winding elements 3, 4 correspond to the above-described embodiment according to Figures 1 to 5. The intermediate element 19 comprises a first end section 29 to be connected to an end section of the first winding element 3 via a first connecting member 6 and a second end section 29' to be connected to an end section of the second winding element 4 via a second connecting member 6'. The connection between the winding elements 3, 4 and the intermediate element 19 via the connecting members 6, 6' is realized as described with respect to Figures 1 to 5, which are mentioned for the sake of simplicity.

[0038] Figure 7B A set of conductor sections is shown which are to be connected to further conductor sections (not shown) to together form a single conductor for an electric machine.

[0039] Figure 7C A conductor comprising a plurality of conductor parts is shown in an exploded view. The conductor 2 is hollow and forms a channel 7 through which a coolant can flow. As in the above-described embodiments, the conductor 2 has two functions, namely, conducting an electric current and conducting a coolant. The conductor 2 has an inlet 22 and an outlet 23, so that a cooling fluid can be supplied through the conductor circuit.

[0040] FIG. 8A to FIG. 8C The diagram shows a circuit with winding elements 3, 4 and an intermediate element 19. Figure 7C The conductor 2 of the motor is provided together with the stator core 20 of the motor. The stator core 20 is configured as described in the first embodiment, and the description of the first embodiment is referred to here, wherein the same or corresponding components are provided with the same reference symbols. The conductor 2 shown here comprises 16 pairs of straight intermediate elements 11, which are connected with the corresponding winding elements 3, 4 to form a channel 2 with a meander-like structure on the circumference. The straight intermediate elements 11 are arranged in the corresponding slots 21 of the stator core 20, wherein a plurality of intermediate elements 11 are accommodated in each slot 21. As particularly in Figure 8B and Figure 8C As can be seen in the figure, the intermediate element 11 is axially longer than the axial extension of the stator core 20. The ends 34, 34' of the straight elements just protrude beyond the end faces 32, 33 of the stator core 20, in particular by less than half the length L6 of the connecting members 6, 6'.

[0041] The winding elements 3, 4 are arranged axially adjacent to the stator core 20 and span a plurality of slots 21 in the circumferential direction. The inlet 22 and outlet 23 of the conductor 2 may be located at Fig. 8A Cooling fluid may be supplied to the circuit on the terminal block (not shown). For simplicity, Fig. 8A and Figure 8B Only one channel 2 is shown. However, it is to be understood that in the fully installed condition, the stator 25 comprises a plurality of channels 2, such as for example in combination with Figure 6 Just as described.

[0042] Reference Numbers 2 conductors 3 Winding elements 4 Winding elements 5 Winding elements 6Connecting components 7 channels 8 straight parts 9 straight part 10 Reverse section 11 Reverse section 12 End section 13 End section 14 holes 15 End face 16 Stop surface 17 End face 18 stop surface 20 stator core 19Intermediate components 21 Slots 22Entrance 23Exit 24 inside 25 Motor 26 stator 27 rotors 28 Winding 29, 29' end section 30 permanent magnets 31 Drive shaft 32 end face 33 end face 34, 34' end A axis d, D diameter L length

Claims

1. A conductor to be inserted into a slot of an electric machine, comprising: A first winding element (3) made of an electrically conductive material, as a hollow conductor having a channel (7) through which a coolant can flow, wherein the first winding element (3) is integrally formed with a first straight portion (8), a reverse portion (10), and a second straight portion (9) parallel to the first straight portion (8), wherein the first straight portion (8) has a first end section (12), and the second straight portion (9) has a second end section (13), and a hollow connecting member (6) made of a conductive material, Features The hollow connecting member (6) and the first end section (12) of the winding element (3) can be axially inserted into each other to form an axially overlapping electrical and fluid connection.

2. The conductor according to claim 1, Features The hollow connecting member (6) is connected to the first end section (12) of the winding element (3) by means of an interference fit.

3. The conductor according to any one of claims 1 or 2, Features The end sections (12, 13) have connecting holes (14, 17) which extend from the end faces (15) of the winding elements (3, 4) to the stop faces (16, 18) and have a larger cross section than the channel (7).

4. The conductor according to any one of claims 1 to 3, Features In the inserted state, the hollow connecting member (6) is in axial abutment with the stop surfaces (16, 18) of the winding elements (3, 4).

5. The conductor according to any one of claims 1 to 4, Features The outer diameter (D6) of the hollow connecting member (6) is larger than the inner diameter (d7) of the channel (7) of the winding elements (3, 4).

6. The conductor according to any one of claims 1 to 5, Features The minimum inner diameter (d6) of the hollow connecting member (6) is greater than 0.9 times the minimum inner diameter (d7) of the channel (7) of the winding elements (3, 4).

7. The conductor according to any one of claims 1 to 6, Features The axial length of the hollow connecting member (6) is at least 0.1 times, in particular at least 0.2 times, the length of the first straight portion (8, 9) of the winding elements (3, 4).

8. The conductor according to any one of claims 1 to 7, Features At least one of the hollow connection member (6) and the winding elements (3, 4) is made of copper, aluminum, stainless steel, or an alloy including at least one of copper, aluminum and stainless steel.

9. The conductor according to any one of claims 1 to 8, Features The materials of the hollow connection member (6) and the winding elements (3, 4) are selected so that the difference between the thermal expansion coefficient of the material of the hollow connection member (6) and the thermal expansion coefficient of the material of the winding elements (3, 4) is less than 10%.

10. The conductor according to any one of claims 1 to 9, Features providing a second winding element (4), the second winding element (4) having the same structure as the first winding element (3), The first winding element (3) and the second winding element (4) are connected to each other via a hollow connecting member (6), on one side, the hollow connecting member (6) is axially inserted into a first end section of the first winding element (3), and on the other side, the hollow connecting member (6) is axially inserted into a second end section (13) of the second winding element (4).

11. The conductor according to any one of claims 1 to 10, Features The conductor (2) is composed of a plurality of first and second winding elements (3, 4), which are connected to each other via a plurality of hollow connecting members (6), wherein the conductor forms a continuous cooling channel (7) having an inlet (22) and an outlet (23).

12. The conductor according to any one of claims 1 to 9, Features The first winding element (3) is connected to the straight intermediate element (11) via a hollow connecting member (6), wherein one side of the hollow connecting member (6) is axially inserted into the end section of the first winding element (3) and the other side of the hollow connecting member (6) is axially inserted into the straight intermediate element (11), as well as The straight intermediate element (11) is connected to the second winding element (4) via a second hollow connecting member (6').

13. An electric motor comprising a stator (26) and a rotor (27), The rotor (26) comprises a stator core (20) having a plurality of longitudinal slots (21) distributed on a circumference, wherein a plurality of conductors (2) are arranged in each longitudinal slot (21) of the stator core (20) for generating an electromagnetic field, Features At least two conductors of the plurality of conductors (2) are configured according to any one of claims 1 to 12.

14. The electric machine according to claim 11, Features The stator (26) comprises at least four conductor wires in each slot (21), wherein at least two conductor wires of the plurality of conductor wires are configured as solid conductors.

15. The electric machine according to claim 13 or 14, Features The hollow connection members (6) of the plurality of conductors (2) are arranged in a central plane, the central plane being arranged between a first end face (32) and an opposite second end face (33) of the stator core (20).

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