EP3398246A1

EP3398246A1 - Electrical conductor for an electrical machine with an elevated power-to-weight ratio and electrical component for the electrical machine

Info

Publication number: EP3398246A1
Application number: EP17702798.4A
Authority: EP
Inventors: Mykhaylo Filipenko; Paul Beasley
Original assignee: Siemens AG
Current assignee: Rolls Royce Deutschland Ltd and Co KG
Priority date: 2016-02-11
Filing date: 2017-01-24
Publication date: 2018-11-07
Also published as: DE102016202071A1; CN108604842B; WO2017137250A1; US10749394B2; US20190027988A1; CN108604842A

Abstract

The invention relates to an electrical conductor which is made up substantially of one or even several metal conductors which are sheathed by a graphene layer. Particularly in the case of the electrical conductor transporting an alternating current, the current in the conductor is forced radially outwards and therefore flows in the graphene layer. Since graphene has a substantially better conductivity than the materials customary in this application, such as copper for example, relatively low losses are accordingly produced and substantially higher degrees of efficiency can be achieved. The electrical conductor constructed in this way is used in a stator and/or rotor winding of an electrical machine, so that it has a significantly elevated power-to-weight ratio.

Description

description

Electrical conductor for an electric machine with increased power-to-weight ratio and electrical component for the electric machine

The invention relates to an electrical conductor and its use, for example, for conducting the electrical current in the application of an electrical machine, for example. For a generator or for an electric motor. Furthermore, the invention relates to a component of the electrical machine, which is equipped with the electrical conductor, for example. A stator or a rotor whose respective winding is realized by means of the electrical conductor.

For the classification of an electrical machine, the so-called power to weight ratio can be used, inter alia, which constitutes erbringbare from the engine power into Ver ^¬ relation to their weight and / kg is given arrival usually in kW. While for many technical applications Leis ^¬ processing weights in sizes up to simple truck / kg are sufficient, one needs eg. For the electrification of aviation electrical machines with power weights of at least 20 kW / kg.

To increase the power density of electrical machines, for example, the current load in the stator of the machine or the current density in the stator windings can be increased. As a result, less conductor material is required in the windings with the same power, which reduces the weight of the machine while maintaining the same power.

In order to increase the current density from usual values, such as 2-10A / mm ^2, to the order of 25-100A / mm ² , in a first approach, the copper windings forming the stator windings can be cooled during operation. For this purpose, the copper windings can be brought into direct contact with a cooling medium or they are hollowed inside. staltet and the cooling medium is pumped directly through the so ^¬ th shaped cavity. In both cases, a relatively large contact area between the conductor and cooling medium ^¬ yields to and thus an increased cooling effect, so that a comparatively large amount of heat can be removed. This is reflected in the fact that the electrical lines can transport higher currents. In a second approach to increase the current density cryogenically cooled, possibly even supralei ^¬ tende electrical conductors are used, the electrical resistance decreases significantly with the ambient temperature. Since ^¬ by the losses in the conductor reduce, resulting in relatively high current densities.

In both approaches, which are ultimately based on cooling of the respective electrical conductor, however, has the disadvantage that an increased effort is necessary to cool the conductor. Furthermore, the electrical losses are comparatively high, and thus the efficiency is low, especially when in ^¬ nengekühlten waveguide.

It is therefore an object of the present invention to provide an alternative way to increase the power weight of an electric machine. This object is achieved by the electrical conductor described in claim 1 and its use and by the electrical component described in claim 7 for an electric machine. The subclaims describe advantageous embodiments.

The electrical conductor serves to conduct an electrical current in a current flow direction. In this case, the electrical conductor is formed by a multiplicity of metallic conductors which are at least partially surrounded, in particular sheathed, by a graphene layer.

The concept underlying the invention is to use ei ^¬ nen electrical conductor, the conventional metallic conductor is surrounded or encased by said graphene layer. This results in the advantage that in particular AC losses (AC losses) of such an electrical conductor compared to conventional conductors are reduced by factors of the order of 100. This results from the fact that the current flowing over the electrical conductor current is urged the graphene layer due to the radially outward current displacement. Since graphene has a significantly better conductivity than the materials commonly used in this application, such as copper, correspondingly lower losses result and significantly higher efficiencies can be achieved. Also characterized in that the metal ^¬ metallic conductor comprises a plurality of separate individual metallic conductors, results in a further reduction of the effect of the current displacement.

Consequently, promises the use of such an electrical conductor in place of the typically incorporated releasing ^¬ th electrical conductors for example. Consist of a gate surrounded by a Isola- copper wire, for a component of an electric machine, a significantly increased Leistungsge ^¬ weight of this electrical component having electrical ^¬ machine. As an additional advantage results from the comparison with conventional materials also better thermal conductivity of graphene less expensive cooling.

The electrical conductor can be realized in one embodiment as a stranded conductor having a plurality of individual wires. Each of the individual wires of the Lit ^¬ zenleiters one of the metallic conductors which are surrounded by the graph forms. Accordingly, the individual wires are each at least partially surrounded or encased by a graphene layer. The combination of stranded conductor and Graphenummantelung the individual wires results in a further improved Leitfä ^¬ ability of the electrical conductor, especially for alternating ^¬ current. In another embodiment, the electrical conductor can be realized as a layer stack having a plurality of individual layers and thus forming a film conductor. The individual layers are stacked one above the other in a direction perpendicular to the current flow direction and the plurality of individual layers comprises at least one metalli ^¬ cal layer which forms the metallic conductor, and not only the at least one, but at least two

Graphene sheets. These individual layers are arranged one above the other such that the metallic layer lies between the two graphene layers and thus the graphene layers at least partially surround the metallic conductor. The particular advantage of such a foil conductor is the simpler and cheaper manufacture since graphs can be produced großflä ^¬ chig already. A coating of such a graphene sheet with copper, which then forms the metallic conductor, can be done, for example, with a so-called CVD method. In particular, very thin copper layers could be realized much better than in the normal conductor, which leads to a strong reduction of the proximity losses.

In particular, the plurality of individual layers may comprise a plurality of metallic layers as well as a plurality of graphene layers, wherein the electrical conductor is formed not only by one but by a plurality of metallic conductors. Each me ^¬-metallic layer forms a metallic conductor. The metallic layers and the graphene layers are arranged alternately one above the other, so that in each case a metallic layer lies between two graphene layers and thus these graphene layers at least partially surround the respective metallic conductor. In addition to the above-mentioned advantages of the foil conductor, a further improvement in the conductivity results here from the fact that the electrical conductor has not just one but a plurality of metallic individual conductors. In the case of the foil conductor, two graphene layers of the layer stack and the metallic layer lying between these two graphene layers can form an electrical conductor element in a further development of the embodiment. The plurality of individual layers additionally includes heat dissipating layers, in particular ceramic layers, which are arranged in the layer stack, that a respective electrical conductor element is located between each two of the leading wärmeab ^¬ layers. The heat dissipating layers, which may be formed in particular as ceramic layers, on the one hand allow a better removal of any resulting heat and cause on the other hand, an improved stability of the electrical conductor. In this case, at least the uppermost and the lowermost layer of the layer stack may be heat-dissipating layers.

An electrical component for the electric machine has a carrying at least in the operating state of the electric machine by electric power in a current flow direction electrical conductor, the electrical conductor by at least one, at least partly surrounded by a graphene layer, in particular coated, metalli ^¬ rule conductor is formed. Due to the improved conductivity of such a particular electrical conductor, the use of this electrical conductor in or for an electric machine promises a significant increase in the power weight. The electrical component may be a stator for the electrical ^¬ specific machine, wherein the electrical conductor used to implement a particular arranged on the stator the stator winding. The electrical component may further be a rotor for the electric machine, wherein the electrical conductor is in ^¬ particular for the realization of a rotor arranged on the winding. The electrical conductor may advantageously be an electrical ^¬ shear ladder with a plurality of metal strands, as already described above.

Further advantages and embodiments will become apparent from the drawings and the corresponding description.

The invention and exemplary embodiments will be explained in greater detail below with reference to drawings. There, the same components in different figures are identified by the same reference numerals. demonstrate :

1 shows an electrical machine, a cross section of an electrical conductor in a first embodiment, a cross section of the electrical conductor in a first variant of a second embodiment,

4 shows a cross section of the electrical conductor in a second variant of the second embodiment,

5 shows a cross section of the electrical conductor in a third variant of the second embodiment, FIG. 6 shows a cross section of the electrical conductor in a third embodiment.

The 1 shows exemplary and simplified designed as a ^¬ genera tor electric machine 100. It should be noted that the electric machine 100 can be operated in a similar construction fundamentally ^¬ additionally as an electric motor. It is also noted that the structure of the hereinafter beschrie ^¬ surrounded machine is purely exemplary. It can be known as are out set so that depending on the design of the electrical machine, etc. the various components of the machine may be arranged differently as a generator or as an electric motor and / or as eg. radial or axial flow machine having formed as an inner ^¬ or also as an external rotor rotor. However, all embodiments have in common that electrical conductors are required for current transport. These electrical conductors and their application in an electric machine represent the actual focus of the invention, while the concrete construction of the machine is not of particular importance. For this reason, details of the electric machine are not discussed.

The generator 100 has a stator 110 and a rotor 120 formed as a domestic nenläufer, the rotor 120 is disposed inside the stator 110, and rotates about an axis of rotation Betriebszu ^¬ stand of the electrical machine 100th For this purpose, the rotor 120 can be driven via a shaft 130 and placed in ro tation by means of a motor not represent ^¬ provided. Pole shoes 121 of the rotor 120 represent magnetic poles, and the stator 110 has a plurality

Stator windings 111-1, 111-4, which are respectively arranged on pole pieces 119-1, 119-4 of the stator 110 and wound around this. Each of the windings 111-1, 111-4 is formed by an electrical conductor 112, which flows through in the operating state of the electric machine 100 of a elekt ^¬ step current. The pole shoes 121 of the rotor 120 may be formed, for example, as permanent magnets or as excited Wick ^¬ lungs. The following example assumes that they are permanent magnets.

Upon rotation of the rotor 120, a voltage is induced in the stator windings 111-1, 111-4 of the stator 110 in a known manner, which voltage is supplied via electrical lines 141, 142 to electrical terminals 143, 144 of the generator 100. This induced voltage can be tapped at the terminals 143, 144 and finally made available to an electrical load 200. For operating the electric machine 100 as an electric motor instead of the electric load 200 ^¬ a clamping voltage source 300 is connected to the terminals 143, 144th This is likewise symbolized in FIG. The voltage source 300 provides ^¬ eg., An AC voltage is available, that causes the stator windings 111-1, 111-4 DEM generate respective magnetic fields which interact with the magnetic fields of the permanent magnets ^¬ 121 of the rotor 120 in exchange effect. As is known, this results in that with a suitable arrangement of said components relative to one another the rotor 120 and with it the shaft 130 are set in rotation. The shaft 130 is connected to an object 500 to be driven, for example with a propeller, which is also set in rotation by the rotation of the rotor 120 and the shaft 130.

2 shows a first embodiment of the erfindungsge ^¬ MAESSEN electrical conductor 112 in a cross-sectional view. An electric current would thus run in the view of FIG 2 in the paper plane or out of this. An electrical conductor 112, from which the respective

Stator windings 111-1, 111-4 are formed, consists of a metallic conductor 113, for example. Of a copper conductor, which is at least partially passed from one graphene layer 114 to ^¬ or encased. Here, the supplement "at least partially surrounded" express that the copper conductor, for example. At the beginning and end is not necessarily of the

Graphene layer 114 is covered, so that the conductor 113 can be electrically connected to other components, for example. With the electrical lines 141, 142 and possibly directly to the electrical terminals 143, 144, respectively. For example. the graphene layer 114 may extend substantially completely along the length of the metallic conductor 113, data on but the ends of the metallic conductor 113 as far as non-blank ^¬ revealed that these can be electrically connected to the other components. In the first embodiment, the electrical conductor 112 is similar to a conventional electrical conductor, which typically includes a metallic conductor, such as a copper conductor, of substantially circular cross-section and an insulating sheath. In contrast thereto, the herein ver ^¬ applied metallic conductor 113 of the electrical conductor 112 is surrounded with the graphene layer 114 and jacketed. In this case, a sheath is characterized in that it extends completely in a circumferential direction around the sheathed conductor completely and also at least as far as possible completely along the longitudinal extent in the current flow direction. A flowing over the copper conductor 113 current is due to the radially outward current displacement in the

Graphene casing 114 pushed. Since graphene has a significantly better conductivity than the materials commonly used in this application, such as copper, correspondingly lower losses result and significantly higher efficiencies can be achieved. FIG. 3 shows a cross-sectional view of a second ^{embodiment of} the electrical conductor 112. An electric current would thus also run into or out of the plane of the paper in this view. In the second embodiment, the electrical conductor 112 is formed as a foil conductor. In this case, the electrical conductor 112 is a layer stack comprising a plurality of individual layers, wherein the individual layers are stacked one above another in a direction x perpendicular to the current flow direction z of the electrical current in the electrical conductor 112. For the section of the electrical conductor 112 shown in FIG. 3, the current flow direction corresponds to the z-direction. In the first, simplest variant of the second embodiment, the plurality of individual layers has a metallic one

Layer 113-1, which forms the metallic conductor 113, as well as two graphene layers 114-1, 114-2. The individual layers 113-1, 114-1, 114-2 are alternately arranged above one another ^¬ so that the metallic layer 113-1 between the two graphene layers 114-1, 114-2 and is the Graphene layers 114-1, 114-2 thus at least partially surround the metallic conductor 113-1. In this second embodiment, therefore, the metallic conductor 113-1 is not encased by the graphene layer, but it is one each

Graphene layer 114-1, 114-2 disposed on an upper and a lower side of the metallic conductor 113-1.

The film conductor can be defined, for example, by defining the extensions of its individual layers in the respective cross section, i. in the two in the current flow direction z by the single layer perpendicular directions x, y, strongly different from each other, for example. By an order of magnitude or typically even more. Thus, while the extent of each individual layer in the current flow direction z is typically substantially greater than the extensions in the cross-sectional directions x, y, one of the extensions in the cross-sectional directions x, y, for example, the extension in the y-direction, is substantially larger than that Extension in the other cross-sectional direction, in this example, the x-direction.

Terms such as "above", "below", "above each other" etc. be ^¬ taking place in this context, and especially in connection with the second embodiment to that spatial direction in which the individual layers of the layer stack have the least extent. In a first Proximity can be assumed as described above that the individual layers extend substantially in two spatial directions, namely in the current flow direction, for example. The z-direction, and in a direction perpendicular thereto, for example. In the y-direction, while in the third spatial direction, in this case thus in the x-direction, have a comparatively small extent, that is to say are quasi-two-dimensional, that the terms "above,""below,""above one another," etc. refer to the x-direction in the example given. Direction . The particular advantage of such a film conductor is the simpler and cheaper production, since graphene can already be produced over a large area, so that, for example, a copper layer or film can be coated with a graphene layer. Alternatively, it is also conceivable, a

Graphene foil to coat with copper, which then forms the me ^¬ tallischen conductor. This can be done, for example, with a so-called CVD method ("chemical vapor deposition" or "chemical vapor deposition"). In particular, very thin copper layers would be much better realized than a normal conductor, resulting in a strong reduction of Proximityverluste.

In a second variant of the second embodiment of the electrical conductor 112, which is shown in FIG 4, the layer stack is not only one but several me ^¬-metallic layers, whereby here each of the metalli ^¬ rule layers 113-1, 113- 2 forms a metallic conductor of the electrical conductor 112. In addition to the metallic layers 113-1, 113-2, the layer stack has a plurality of graphene layers 114-1, 114-2, 114-3. The metallic layers 113-1, 113-2, 113-3 and the

Graphene layers 114-1, 114-2, 114-3 are again arranged alternately one above the other, so that in each case a metallic layer lies between two graphene layers and these

Graphene layers 114-1, 114-2, 114-3 thus at least partially surround the respective metallic conductors 113-1, 113-2, namely above and below the respective metallic conductor 113-1, 113-2 are arranged.

For the sake of clarity, the embodiment of the electrical conductor 112 shown in FIG. 4 has only A = 2 metallic layers 113-1, 113-2. Of course, however, the second variant can also be realized with more than two metallic layers (A> 2) and a correspondingly higher number B of graphene layers 114-1, 114-B, wherein in this second variant it will apply in general, but not necessarily B = A +. 1 In a third variant of the second embodiment, which is shown in FIG. 5 and which corresponds to a development of the second variant, two each form

Graphene layers 114-1, ... of the layer stack, and between these two graphene layers 114-1, ... lying metallic layer 113-1, ... an electric conductor element of the electrical conductor ^¬ rule 112. In addition to in connection with the introduced variant second layers are in the third variant heat dissipating layers 115-1, ... vorgese ^¬ hen. The heat dissipating layers 115-1, ... are arranged in the layer stack such that a respective electrical conductor element lies between in each case two of the heat dissipating layers 115-1,. The various individual layers are arranged such that the individual layers lying in the layer stack at the wide ^¬ th outside, ie in superposed layers, the uppermost and lowermost single ^¬ layer of the layer stack are heat-dissipating layers. The heat dissipating layers, in particular as

Ceramic layers may be formed that allow on the one hand a better removal of possibly emerging heat and be ^¬ act on the other hand an improved stability of the electrical ^¬ rule manager 112. In the specific, exemplary embodiment in FIG 5, the layer stack A = 2 metallic layers 113-1, 113-2, and B = 4 graphene layers 114-1, 114-B and, accordingly, C = 3 heat dissipating layers 115-1, 115-C. In a third embodiment of the electrical conductor 112, this is designed as a stranded conductor, which has a plurality of ^¬ number of metallic individual wires 113-1, 113-7. A first variant of the third embodiment is shown in FIG. In this first variant, at least one of the individual wires, but ideally each individual one of the individual wires, is surrounded or encased in each case by a graphene layer 114-1, 114-7. Ideally, the electrical lines 141, 142, which extend between the respective stator winding 111 and the terminals 143, 144 of the electric machine 100, constructed in an analogous manner, ie the electrical lines 141, 142 consist of one or more metallic conductors 113, for example. of copper conductors, which at least in part, by a ^¬ graphene layer 114 are surrounded.

A suitable method for producing the graphene layers is, for example, the technique for coating copper with graphene, which is known as "microwave plasma chemical vapor deposition." Alternatively, a technique known as "chemical vapor deposition" or "chemical vapor deposition" is known whose help graphene can be applied to copper.

Possibly. For example, in the various embodiments and variants, the graphene layer 114 may be surrounded by an insulating varnish (not illustrated here) in order to prevent breakdowns between adjacent conductors at high voltages. Since the conductivity of the graph is dependent ^¬ tung so rich that a current only within the quasi-two-dimensional graphene sheet, but is not directed perpendicular thereto, can be dispensed with under certain circumstances to such insulating lacquer layer. This would have the advantage that the degree of filling of the winding can be increased over conventional approaches with a dedicated insulating layer.

Claims

claims

An electrical conductor (112) for conducting an electrical current in a current flow direction (z), said electrical conductor (112) being defined by a plurality of metallic conductors (113, 113-1, 113, respectively) at least partially surrounded by a graphene layer (114) -2, ...) is formed.

2. Electrical conductor (112) according to claim 1, characterized in that the electrical conductor (112) is a stranded conductor having a plurality of individual wires, each of the individual wires being one of the metallic conductors (113-1, 113-2,. ..) forms.

3. Electrical conductor (112) according to claim 1, characterized in that the electrical conductor (112) is a plurality of individual layers having Schichtstapel, wherein

the individual layers are stacked one above the other in a direction (x) perpendicular to the current flow direction (z),

the plurality of individual layers comprises at least one metallic layer (113-1) which forms the metallic conductor (113) and at least two graphene layers (114-1, 114-2),

- The individual layers are arranged one above the other so that the metallic layer (113-1) between the two graphene layers (114-1, 114-2) is located.

4. Electrical conductor (112) according to claim 3, characterized in that the number of individual layers of multiple me ^¬-metallic layers (113-1, 113-2, ...) as well as several

Graphene layers (114-1, 114-2, ...) comprises and the electrical conductor (112) through a plurality of metallic conductors (113) ge ^¬ forms, wherein

- each metallic layer (113-1, 113-2, ...) constitutes one of the metal ^¬ metallic conductor,

- The metallic layers (113-1, 113-2, ...) and the

Graphene layers (114-1, 114-2, ...) are arranged alternately one above the other, so that in each case a metallic layer (113-1, 113-2, ...) lies between two graphene layers (114-1, 114-2, ...).

5. Electrical conductor (112) according to claim 3 or 4, characterized in that in each case two graphene layers (114-1,

114-2, ...) of the layer stack and the metallic layer lying between these two graphene layers (114-1, 114-2, ...)

Layer (113-1, 113-2, ...) bil ^¬ an electrical conductor element, wherein the plurality of individual layers additionally heat-dissipating layers (115-1, 115-2, ...), in particular

Ceramic layers, which are arranged ^¬ such in the layer stack, that a respective electrical conductor element between each two of the heat dissipating layers (115-1,

115-2, ...).

6. Electrical conductor (112) according to claim 5, characterized in that the uppermost (115-1) and the lowermost layer (115-3) of the layer stack are heat dissipating layers.

7. The electrical component (110, 120) for an electrical Ma ^¬ machine (100), wherein the component a at least in the loading ^¬ operating state of the electric machine (100) traversed by electrical ^¬ schem current in a current flow direction (z) electrical conductors (112 ), wherein the electrical conductor (112) is formed by at least one metallic conductor (113) at least partially surrounded by a graphene layer (114).

8. Electrical component (110, 120) according to claim 7, characterized in that the electrical component is a stator (110) for the electric machine (100), wherein the electrical conductor (112) has a stator (110) arranged on the stator winding (110). 111-1, 111-2, ...).

9. electrical component (110, 120) according to claim 7, characterized in that the electrical component is a rotor (120) for the electric machine (100), wherein the electrical conductor (112) is a winding arranged on the rotor (120).

10. Electrical component (110, 120) according to any one of claims 7 to 9, characterized in that the electrical

Conductor (112) is an electrical conductor according to one of claims 1 to 6.