WO2019038080A1

WO2019038080A1 - Power transmission system for generating a current in a field winding of a rotor of an electric machine and electric machine and motor vehicle

Info

Publication number: WO2019038080A1
Application number: PCT/EP2018/071414
Authority: WO
Inventors: Michael Bulatow; Wilhelm Hackmann; Henrik Krupp
Original assignee: Continental Automotive Gmbh
Priority date: 2017-08-23
Filing date: 2018-08-07
Publication date: 2019-02-28
Also published as: DE102017214766A1; DE102017214766B4; CN212518805U

Abstract

The invention relates to a power transmission system (21) for generating a current in a field winding (18) of a rotor (17) of an electric machine (12), wherein a secondary-side winding (23) for arrangement on the rotor (17) and a rectifier circuit (REC) connected to the secondary-side winding (23) are provided to supply a DC voltage (U) generated between two connection contacts (47) for the field winding (18). According to the invention, a winding board (41) of the secondary-side winding (23) provides a plurality of parallel-connected spiral coils (A1, A2, A3, A4, A5) and each of the spiral coils (A1, A2, A3, A4, A5) is formed from a plurality of spiral elements (50) and for this purpose the winding board (41) is designed in a multilayer manner and a plurality of the spiral elements (50) are arranged in a manner offset from one another by a respective angular offset (51) in each layer (L1, L2, L3, L4) of the winding board (41) and, for each of the spiral coils (A1, A2, A3, A4, A5), the respective spiral elements (50) thereof are connected in series with all the layers (L1, L2, L3, L4) by means of vias (52) of the winding board (41).

Description

description

Power transmission system for generating a current in a field winding of a rotor of an electric machine and electric machine and motor vehicle

The invention relates to a power transmission system for generating a current in a field winding of a rotor of an electric machine. The power transmission system has a rotary transformer, that is an inductive coupler. By means of the power transmission system, a direct electrical voltage for driving the current in the field winding of the rotor of the electric machine can be generated without contact. The invention also includes an electric machine with the power transmission system and a motor vehicle with the electric machine according to the invention.

A rotary transformer of the type mentioned is known for example from DE 10 2014 202 719 AI. Accordingly, a power transmission system for an electric machine has a primary-side winding of a rotary transformer for spatially fixed An ^¬ arrange in the electrical machine and for generating an alternating magnetic field. Furthermore, the Leis ^¬ tung transmission system on a secondary side winding of the rotary transformer for positioning on one end face of the rotor of the electric machine as well as for converting the located time changing magnetic flux into an AC voltage and a rectifier circuit board having a rectifier circuit for rectifying the AC voltage. The rotary transformer is a rotationally symmetrical transformer with an air gap, wherein the secondary-side winding is rotatably mounted with respect to the primary-side winding. The rotor of the electric machine can thus rotate with the secondary-side winding in the alternating magnetic field of the primary-side winding. A load connected to the secondary-side winding DC ^¬ judge circuit board of the rectifier is adapted to generate, from the generated from the secondary side winding AC voltage a DC voltage and this to connection contacts for to provide the exciter winding. The current in the field winding thus always flows when a DC voltage is generated at the two terminal contacts. It is known from the prior art that the secondary-side winding can be formed on the basis of printed conductors of a printed circuit board. Such a printed circuit board with conductor tracks for a winding is referred to below as Windungsplatine. By "winding", therefore, no wound wire is meant here, but rather the function of an electrical winding is meant, ie an arrangement with an electrical coil.

The described contactless transmission system using a rotationally symmetrical transformer or Drehübertragers to supply the excitation winding with

DC voltage can be used in a separately excited synchronous machine

Replace Slip Ring Carbon Brush Systems. The use of a winding board has the advantage over the secondary winding on the basis of stranded wire or round wire that the secondary winding can be flattened compared to the use of a winding board.

However, there is also a conflict when using the winding circuit board with interconnects for the required turns of the secondary-side winding. In order to be able to carry enough electricity, the conductor tracks must be designed to be correspondingly wide. However, this leads to the disadvantage that are induced within the conductor tracks in the alternating magnetic field, eddy currents, in turn, the performance of the rotary transformer impressive ^¬ pregnant, that reduce the provisioned at the output electric power.

From US Pat. No. 6,664,883 B2, the principle is known of distributing a spiral coil over several layers of a multilayer winding circuit board. Windings of a primary coil and a secondary coil of a transformer are alternately realized in the winding circuit board. The primary coil and the secondary coil are thus not mutually movable and are not suitable as

Rotary transmission. From DE 20 2012 002 027 Ul a rotor for an electric machine is known in which a winding ^¬ head cover for covering the winding heads of the rotor is arranged on one end face. On the winding head cover a sensor track of a rotary encoder is arranged.

From DE 20 2012 002 024 Ul a rotor with winding head ^¬ cover is known in which a balancing ring is arranged to compensate for an imbalance of the rotor.

The invention has for its object to provide for an electrical machine, a power transmission system for the contactless transmission of electrical power to operate the field winding.

The problem is solved by the subject matters of the independent Pa ^¬ tentansprüche. Advantageous further developments of the invention are ^¬ described by the dependent claims, the following description and the figures.

The invention relates to the contactless power transmission system described above with primary-side winding, secondary-side winding and rectifier board with a rectifier circuit.

The invention also uses a winding board for providing the secondary-side winding in the form of printed conductors. Overall, the winding circuit board must have the form of a ring which can be applied to a shaft of the rotor or arranged around a shaft of the rotor. According to the invention now has the secondary-side winding on a plurality of parallel-connected Spi ^¬ ralspulen, each of said spiral coil is formed of multiple helical segments or spiral elements. With spiral coil this is not necessarily meant a round coil. The spiral coil can have a round or other geometry which can be arranged rotationally symmetrically or rotationally symmetrically about an angular offset. The spiral coil generally represents a Einzellei ^¬ terzug or a single winding represents. To form the spiral coils the Windungsplatine is designed multi-layered. It is therefore a so-called multi-layer circuit board (multilayer PCB, printed circuit board PCB). Each layer (English: Layer) of the Windungsplatine can have a plurality of interconnects in a known manner. In each position of the Windungsplatine more of the spiral elements of the spiral coils are arranged before each spiral coil, a spiral element. The spiral elements of each layer are preferably arranged concentrically and offset from each other by an angular offset. The concentric arrangement results with respect to the axis of rotation of the rotor. The spiral elements can therefore be arranged as a ring or annularly about the axis of rotation of the rotor. For each adjacent spiral element each spiral element is offset by a predetermined angular offset.

Each spiral coil thus has only one spiral element per layer of the winding plate. For each spiral coil their respective spiral elements of all layers of the winding circuit board are connected in series by means of through-connections of the winding circuit board. Spiral elements of adjacent layers are directly electrically coupled. Starting from an uppermost layer of the winding plate thus results in a spiral coil, by the spiral element of this layer is electrically connected to a spiral element of the underlying befind ^¬ position and this spiral element is in turn electrically connected to the spiral element of the underlying layer and this goes on until the last spiral ^¬ element of the lowest layer is reached. The ends of each spiral coil are then connected to the rectifier board. By the described arrangement, the spiral coils are distributed over several layers of the winding circuit board and interlocked or intertwined. So they do not have the usual flat or flat shape.

The invention provides the advantage that the current carrying capacity of the parallel circuit of spiral coils is greater than that of each individual spiral coil. Nevertheless, due to the electrical separation of the individual spiral elements on each layer of the winding plate, it can not cause eddy currents come between the spiral coils. Thus, the number of spiral coils connected in parallel with respect to the width of each conductor track of the individual spiral coils can thus be adjusted in order to achieve a maximum current carrying capacity of the overall arrangement (parallel circuit), without obtaining too great overall losses, which would set thermal limits. The narrower the printed conductors, the smaller the eddy current losses within each individual printed conductor, but also the current carrying capacity of each individual printed conductor decreases. The more spiral coils are connected in parallel, the greater the current carrying capacity of the overall arrangement. For the sake of brevity, the rectifier board is simply as below

Rectifier designated. The invention also includes advantageous developments, the characteristics of which provide additional advantages.

A further deterioration of the performance (output power from ^¬) may result from heating of the conductor paths and of the rectifier. A further development provides that for a cooling of the power transmission system, the DC ^¬ judge circuit board is connected directly to a heat sink and a secondary-side ferrite core of the power transmission system is in contact with the heat sink and the cooling body is adapted to heat from the rectifier plate and the ferrite core towards a Coupling surface of the heat sink, via which the heat sink can be fastened to a support member of the rotor to guide. Such a carrier component can be, for example, the winding head cover mentioned at the beginning of the field winding of the rotor. Such a winding cover is a metal ^¬ metallic, annular cover, which can be slipped over the winding heads of the field winding. A suitable material for the end winding cover is an alloy, as indicated in the aforementioned publications DE 20 2012 002 024 Ul and DE 20 2012 002 027 Ul, the content here in connection with the alloy and the design of the winding overhang as part of this invention to be considered. _r

Important is the design of the heat paths. In particular, heat can be dissipated from the rectifier board via the heat sink on the one hand and from the ferrite core via the heat sink on the other hand in each case to its coupling surface, where they in a Trä- gerbauteil the rotor, in particular a winding head cover, transgress. It is therefore provided in the power transmission system in particular a purely passive, so no active cooling. By passive cooling is meant a heat conduction based cooling. The power transmission system according to the invention may be configured as a separate component for installation in an electric machine or integrated into a Wickelkopfab ^¬ cover.

Another important characteristic of a power transmission system is the speed stability. A further development provides that for a rotational speed of more than 15,000 revolutions per minute and / or for heat conduction, the rectifier plate, the heat sink, the winding plate and the ferrite core are potted with a synthetic resin or encapsulated with a plastic. The potting can be done with an epoxy resin or adhesive. The encapsulation and encapsulation each provide stabilization and mechanical fixation for speeds up to more than 15,000 revolutions per minute. Otherwise, for example, solder joints in the rectifier board would break permanently. By encapsulating and / or overmolding with plastic by means of an injection molding process, the power transmission system is speed-proof for a speed greater than 15,000 revolutions per minute. The encapsulation and encapsulation also each have the advantage that a better thermal conductivity can be achieved than with air. By choosing the synthetic resin or plastic, a thermal conductivity of up to 1 to 2 W / mK can be achieved. Even with conventional epoxy resin, a thermal conductivity of 0, 3 W / mK is possible. The heat dissipation thus in particular includes a heat path connecting the rectifier circuit board via the heat sink and the molding material / plastic sheathing with a Trä ^¬ gerbauteil, and a thermal path which the FER ritkern on the heat sink and the potting material /

Plastic extrusion connects with the carrier component. Also from the winding heat can be dissipated through the potting / art ^¬ stoffumspritzung.

Main heat sources are diodes of the rectifier, the winding and the ferrite core of the secondary side. Less heat loss results from capacitors and the tracks of the

Rectifier board. By means of the encapsulation / encapsulation can be achieved that an additional heat transport path for the removal of heat from the heat sources is provided. Heat particular the Wi ^¬ ckelkopfabdeckung can be routed through the potting / encapsulation and the heat sink then in the carrier component.

A further development provides that the rectifier board has a metal core for heat conduction and the heat sink is in direct contact with the metal core. Thereby, the heat can be removed from the individual electrical and / or electronic components of the rectifier and passed over the Me ^¬ tallkern to the heat sink. The metal core may comprise copper and / or a copper alloy and / or aluminum and / or an aluminum alloy. Copper has the greater thermal conductivity compared to aluminum. In order to achieve the metal core in the rectifier board with the heat sink, a cover layer of the rectifier board can be removed, for example, by milling. The core is milled free, the heat sink is then directly in contact with the core. To ensure reliable heat transfer from the rectifier board into the heat sink, the rectifier board can be bolted to the heat sink. The

Screws are preferably made of metal, which additionally contribute to heat transfer. The heat sink can rest for example on a free-milled surface of the core of the rectifier board. Another way to reduce the heating of components is given by a rectifier circuit on the rectifier circuit a plurality of similar, arranged in parallel circuit branches electronic individual components, in particular diodes having. The Ver ^¬ loss performance that results in rectifying the AC voltage is thus not implemented in a single component, but distributed to several, parallel-connected Einzelbau ^¬ elements, in particular parallel-connected diodes distributed. Thus, therefore, the formation of heat loss is distributed locally, namely on several individual components. By individual components, a single electronic component is meant, which may be soldered, for example, with connection contacts or pins on the rectifier board.

In order to ensure a uniform load of the individual components with electricity, at least some of the individual components can each be preceded by an electrical resistance component for setting a current distribution. Thus, the electrical resistance elements are disposed in the said scarf ^¬ processing branch in series with one of the individual components ge ^¬ on. As a result, a homogenization of the current distribution between the parallel-connected individual components can be achieved. In particular, each circuit branch has only the individual component and the associated resistance element and the associated conductor tracks and solder joints. The use of resistive elements is particularly advantageous for negative temperature coefficients of the diodes. As already stated, the spiral coils are electrically insulated from one another in the area of the winding plate, in order thereby to suppress an eddy current between the conductor tracks of the different spiral coils. Preferably, the parallel circuits of the spiral coil is outside the interturn circuit board, namely in particular the Gleichrichterpla ^¬ tine instead. This minimizes the influence of an alternating magnetic field on the development of eddy currents. In order to electrically isolate the conductor tracks of the spiral coils effectively against each other, ensures in particular that for each position of the Windungsplatine an electrical Po ^¬ potential of the scroll members is adjusted to the respective position. A coil start, eg at a first outer layer, is connected to the potential of the first input of the rectifier circuit and a coil end which may face the first outer layer on the winding board is connected to the potential of the second input of the rectifier circuit. Thus, sections of the spiral elements with the same radial spacing in each intermediate layer of the winding plate each have such a small potential difference that a flashover is prevented. The adjusted potential prevents flashovers between the spiral elements. Of course, the potential is not constant within each location.

With respect to the shape of the individual elements of each spiral spiral coil it can be calculated by the following defi ^¬ statement is made. Each of the spiral coils can have U curves or spiral bindings. The winding board can provide N layers. Each spiral element then has U / N orbits. For a coil with 4 layers and spiral coils with U = 5 orbits, each spiral element is a spiral element with 1.25 orbits of the spiral center. If the start and end point of each spiral coil of the winding circuit board with continuous pins to the rectifier board ^¬ shot, it is advantageous to increase the number of orbits per spiral element / decrease (eg from 1.25 to 1.3), which is An angular offset between the start and end point results and thus the connection points of the spiral coil are not exactly on top of each other. This results in a number U of orbits, which is not an integer (in the example U = 1.3 x 4 = 5.2). Through the series connection of the spiral elements of a single spiral coil over the multiple layers away flows through the spiral elements, a common current, the spiral-inward and spiral-inward in a spiral element alternately flows in the next spiral ^¬ element spiral-abroad. The spiral elements of the secondary-side winding are preferably arranged rotationally symmetrically on the winding plate about the respective angular offset. The arrangement of the spiral elements on each layer is thus a rotationally symmetrical structure, wherein the rotational symmetry always results in a rotation about the angular offset by which the adjacent spiral elements are offset, respectively. As a result, the available space is used. In order to be able to produce the power transmission system in a particularly cost-effective manner, the plated-through holes are configured as simple plated-through holes, that is to say completely guided through all the layers of the winding plate. Such complete

Through-holes or VIAs (Vertical Interconnect Access) can be produced in a single, known per se contacting process.

Another aspect relates to the electrical connection of the excitation winding of the rotor with the terminal contacts of the rectifier board. Each connection contact is preferably designed in each case as a hook, to each of which a wire of the exciter winding can be contacted. Each of the hooks is electrically and me ^¬ mechanically connected directly to the rectifier board. Each wire of the field winding is electrically and mechanically connected to one of the hooks.

The primary-side winding can also have a win ^¬ tion board of the type mentioned. As a result, a design of the power transmission system is flatter Ver ^¬ equal to a primary-side winding, which is formed on the basis of windings of common wire.

The invention also provides for the provision of an electrical machine which is designed as a separately excited synchronous machine and has an embodiment of the power transmission system according to the invention. The invention

Power transmission system makes the electric machine robust against pollution, such as oil or dust, and there is no abrasion as with slip rings. The invention also relates to a motor vehicle having an ^{embodiment of} the electric machine according to the invention. The electric machine is configured as a traction drive for the motor vehicle and is connected to an inverter which is set up for a rotational speed of the electric machine of more than 15,000 revolutions per minute. The use of the power transmission system according to the invention, which is powerful and high-speed resistant, results in an electrical machine which is insensitive to environmental influences.

The motor vehicle according to the invention can be, for example, a passenger car or a truck or an industrial truck.

In the following an embodiment of the invention is described. This shows:

Figure 1 is a schematic representation of a longitudinal section of a third-rotor with brushless power transmission.

FIG. 2 shows a schematic illustration of a longitudinal section of a secondary side of a power transmission system of the rotor of FIG. 2; FIG.

3 shows a schematic illustration of layers of a winding circuit board of the secondary side of the power transmission system of FIG. 2, wherein in each case only a single one of a plurality of spiral elements is shown;

Fig. 4 is a schematic representation of a plan view of the

Winding board of the secondary side of the power transmission system;

5 shows a schematic circuit diagram of the power transmission system; Fig. 6 is a schematic circuit diagram of an alternative principle of the power transmission system;

Fig. 7 is a schematic circuit diagram of another alternative principle of the power transmission system;

8 is a diagram illustrating a heat spread for diodes of the rectifier circuit of the power transmission system; and

Fig. 9 is a schematic representation of an embodiment of the motor vehicle according to the invention.

The embodiment is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual features of the invention that are to be considered independently of one another, which also each independently further develop the invention and thus also individually or in a different combination than the one shown as part of the invention. Furthermore, the described embodiment can also be supplemented by further features of the invention already described.

In the figures, functionally identical elements are each provided with the same reference numerals.

For an overview, reference is first made to FIG. 9. FIG. 9 shows a motor vehicle 10, which may in particular be a motor vehicle, such as a passenger car. The motor vehicle 10 may have an electric traction drive 11, which may be formed on the basis of an electric machine 12. In addition, an inverter 13 and a traction battery 14 are shown. The traction battery 14 may for example be a high-voltage battery, which can provide an electrical voltage greater than 60 V, in particular greater than 100 V. The inverter 13 can from the DC voltage of the traction battery 14 phase currents for a Stator winding 15 of a stator 16 of the electric machine 12 generate in a conventional manner. By the phase currents of the inverter 13, a magnetic rotating field can be generated in an interior of the stator 16 by means of the stator winding 15.

In the interior of the stator 16, a rotor 17 may be rotatably supported. The electric machine 12 may be a separately excited synchronous machine. To this end, an excitation ^¬ winding 18 is provided in the rotor 17, which can be flowed throughput with a direct current. Then, the rotor 17 generates on its outer circumference magnetic poles, interact with the magnetic rotating field of the stator 16, whereby a rotational movement of the rotor 17 results. The rotor then rotates about a rotation axis 19 and thereby rotates a shaft 20, via which a drive torque can be transmitted to wheels of the motor vehicle 10.

To generate the current in the field winding 18, the electric machine 12 may include a power transmission system 21. By means of the power transmission system 21, electrical energy can be transmitted from a stationary primary side PRIM to a rotating secondary side SEC without contact, on the basis of an inductive transmission. For this purpose, the power transmission system 21 may have a rotary transformer with a primary-side winding 22 on a motor housing or a bearing plate and with a secondary-side winding 23 on the rotor 17.

Fig. 1 illustrates a power transmission system 21 in a longitudinal section. FIG. 1 is mirror-symmetrical with respect to the axis of rotation 19, so that the reference numerals are only indicated on one side of the axis of rotation 19. They are also mirror-symmetric for the opposite side.

The power transmission system 21 has the following advantageous characteristics:

It is a cost-producible_kontaktlosen power transmission system for a traction drive: 1) instead of windings of round or flat wire, a multilayer printed circuit board ("winding board", "multilayer PCB") is used with special structuring to avoid the current displacement effect on the layers of the Kup ^¬ ferschichten are structured so for the rotating side of the rotary transfer in that they give a winding;

2) the stationary side of the Drehübertragers can optionally also be realized with a multi-layer Windungsplatine to avoid the current displacement effect or with a winding of round, flat or HF stranded wire in conventional design;

3) a special heat dissipation of the rotary transformer for the primary and secondary side is provided;

4) to optimize the cooling of the rectifier whose circuit is composed of several similar individual elements, e.g. in the manner shown in Fig. 8);

5) high speed resistance (over 15,000 min-1);

6) through the use of the special construction of the rotary transformer can be used both radially (greater than or equal to 0.7 mm in radius) and axially (greater than or equal to 2 mm) larger air gaps;

7) a simplest embodiment of the printed circuit board vias can be used;

8) a symmetrical arrangement of the tracks of the winding board (also referred to herein as "strands") achieves a high packing density.

In order to ensure the rotational speed of the rotating part of the rotary ^{¬ transformer} (secondary side of the rotary transformer and rectified ^¬ judge and smoothing capacitors), this is completely encapsulated or encapsulated with potting material (eg epoxy resin or plastic).

The alternating current to be rectified in a rectifier circuit board of the se ^¬ ondary side and smoothed. In ^¬ example, the rectifier board is as a round part with For example, 25 capacitors and 36 diodes shown. Alternatively, actively rectifying components can be used instead of the diodes. For example, controlled MOSFETs.

The contactless power transmission system based on the rotary transformer can have a rectifier, which is constructed from the interconnection of several (preferably similar) individual components. These individual components (preferably consisting of positive temperature coefficient diodes, for example silicon carbide Schottky diodes) are connected in parallel-connected branches.

For better heat dissipation from the electronic components of the rectifier board is proposed to connect the rectifier ^¬ board directly to a heat sink.

For better heat dissipation of all components of the transfer a special epoxy resin with higher thermal conductivity is used.

PCB winding (Windungsplatine) has parallel only ^¬ switched spiral coils made of individual conductor strips (strands), which serve for realization of high current carrying capacities of the winding board. The parallel connection of several conductor tracks leads only to a minimal increase of the eddy current losses caused by the incident alternating magnetic field in the winding window of the rotary transformer. Due to the special geometry of the individual parts of the transformer this can be produced inexpensively and still fulfills the function.

Fig. 1 shows in detail a non-locating bearing side

(Non-drive side) of the electric machine 12. There is a bearing plate or motor housing 24 and a spring element 25 is shown. The arrangement may alternatively be provided on a fixed bearing side. The shaft 20 of the rotor 17 is mounted rotatably via a bearing 26 on the bearing plate or motor housing 24. Circlips 27, for example, the bearing 26 fix in the axial direction 28 along the rotation axis 19 against slipping. Furthermore, a laminated core 29, winding heads 30 of the exciter winding 18, a cover 31 of the winding heads 30 with a potting compound 32 arranged therein and wires 33 of the field winding 18 are illustrated by the rotor 17. The wires 33 may be electrically and mechanically bonded to the power transmission system 21.

The power transmission system has a fixed side or primary side PRIM and a rotor-mounted secondary side SEC. The primary side PRIM and the secondary side SEC are each formed as rings, which are arranged around the shaft 20. The secondary side SEC may be ^¬ arranged on an end face of the rotor 17 at.

Of the power transmission system 21, the primary-side winding 22, a heat sink 34, a connection board 35 for providing a supply voltage (leading electrical lines are not shown) on a primary side PRIM, metal pins 36 for Durchkontaktieren the An ^¬ circuit board 35 toward a Windungsplatine 37th the primary-side winding 22 and a primary-side ferrite core 38 are shown.

The ferrite core 38 of the primary side PRIM complements with a ferrite core 39 of the secondary side SEC to a magnetic circuit. In the magnetic circuit results in a radial

Air gap 40 through which a generated by the primary winding 22 alternating magnetic field in the ferrite core 39 of the secondary side SEC can change over. Since it is a radial air gap 40, the gap does not change in an axial movement of the shaft 20 in the axial direction 28. With the axial

Movement changes an axial air gap 40 ^λ . The ferrite cores 38, 39 each have an L-profile. As a result, axial tolerances can be compensated. The larger the gap of the radial air gap, the less power can be transmitted. Of course, another profile, such as an E-profile can be used. From the secondary side SEC are further shown: a winding circuit board 41 of the secondary-side winding 23, a heat sink 42, a rectifier board 43 with a

Rectifier circuit comprising capacitors 44 and diodes 45, metal pins 46, via which the winding board 41 is electrically connected to the rectifier board 43, and hooks 47, to which the wires 33 of the field winding 18 are attached. The hooks 47 are also referred to as wrap hooks. They each represent a terminal contact of the rectifier circuit. The rectifier board 43 can be held directly on the heat sink 42 by means of metal screws 48. The heat sink 42 is located with a mating surface on the cover 42 ^λ at the 31st It can be a press fit. The cover may be made of a special metal or a special metal alloy. Examples of a suitable material of the cover can be taken from the cited references DE 20 2012 002 027 Ul and DE 20 2012 002 024 Ul.

Fig. 2 shows in enlargement the upper section of the secondary side SEC, as shown in Fig. 1. It is shown how gaps are filled or filled with a potting compound of an epoxy resin or by means of an encapsulation by plastic. This encapsulation or encapsulation 32 ^λ improves the stability of the secondary side SEC for a high speed. As a result, the power transmission system 21 is speed-proof for rotation numbers greater than 15,000 revolutions per minute. Furthermore, the encapsulation or encapsulation 32 ^λ provides solid-body-based heat transfer from the rectifier board 43 to the heat sink 42. The heat can then pass into the cover 31 from the heat sink 42.

3 illustrates a construction of the winding boards 41 and optionally also the winding board 37. Each of the winding boards 37, 41, but in particular the winding board 41 of the second därseite SEC, can be multi-layered. In the illustrated example, the veran ^¬ Windungsplatinen each have N = 4 layers LI, L2, L3, L4, which are shown in Fig. 3 next to each other. Shown are conductor tracks 49 of a single spiral coil AI. Each conductor 49 of each layer LI, L2, L3, L4 has the shape of a spiral element 50. The spiral coil AI has a total of U = 5 orbits, which are distributed over the N = 4 layers LI, L2, L3, L4. Thus, each spiral element 50 effectively has U / N orbits, that is, 1.25 orbits in the case shown.

Fig. 4 illustrates, as for a plurality of spiral coils AI, A2, A3, A4, A5 on a single layer, here, for example, the outer layer LI, each conductor tracks 49 of spiral elements 50 a plurality of spiral coils AI, A2, A3, A4, A5 concentrically around the Rotation axis 19 and each offset by an angular offset 51 against the adjacent scroll member 50 may be arranged. The angular offset 51 results from the number of spiral coils AI, A2, A3, A4, A5 to: 360 ° / number of spiral coils. Furthermore, plated-through holes 52 are shown, by means of which the spiral elements 50 of each of the coils can be connected in a series connection.

FIG. 5 shows a possible circuit diagram for the power transmission system 21. On the primary side PRIM, an AC voltage for the primary-side winding 22 can be generated from a supply voltage by means of a four-quadrant controller 53. A control logic for the four-quadrant actuator 53 is not shown in Fig. 5. By means of a capacitance 53 ^λ , a resonance behavior of the winding 22 combined with the capacitance 53 ^λ can be set. The capacity 53 ^λ is optional.

On the secondary side SEC results in the secondary-side winding 23, an AC voltage U ^x . On the secondary side SEC, a rectification of the AC voltage U ^x by means of diodes 45 of a rectifier circuit REC done. The diodes 45 and the capacitor 44 are shown here as simple components. They can each also be formed from a plurality of similar elements connected in parallel, which is still related is explained with Fig. 8. In the case of a diode 45, therefore, a plurality of parallel-connected individual diodes and, in the case of the capacitor 44, a plurality of parallel-connected individual capacitors can be provided. About the hook 47, the generated DC voltage U in the wires 33 of the field winding 18 is transferable.

Fig. 6 illustrates an alternative circuit diagram for the power transmission system 21. On the primary side PRIM, only two transistors are needed instead of the four transistors of a four quadrant controller. Instead, a bridge ^¬ circuit of two transistors and two freewheeling diodes 53 ^{λ λ is} provided. On the secondary side SEC as well, the rectifier circuit can be realized with fewer diodes 45 compared to the circuit diagram according to FIG. 5.

Fig. 7 illustrates an alternative circuit diagram for the power transmission system 21, wherein on the primary side PRIM again a four-quadrant 53 is provided with a capacity 53 ^λ . On the secondary side SEC, a center tap 54 is provided on the winding 23, which makes it possible to provide the rectifier circuit REC with fewer diodes 45 as compared to the circuit diagram of FIG. The capacity 53 ^λ is optional. Fig. 8 illustrates a circuit diagram is illustrated by such as a single diode 45 may be formed from a plurality of A ^¬ zelbauelementen 45b. The individual components 45b are arranged in a circuit formed from branches 45a parallel circuit, for equalizing a current sharing each individual components 45b in the scarf ^¬ processing branch 45a, a resistor element may be connected in series 45c. Overall, therefore, provide parallel processing scarf ^¬ branches 45a whose parallel overall function of a single diode 45 is obtained.

Contactless power transmission systems can be mounted either on the fixed or floating side of the rotor. In addition, only the accommodation on the lottery stock side (no drive side) described, because this is advantageous for traction machines. In the power transmission system described here, instead of conventional windings, specially structured, multi-layer printed circuit boards (referred to herein as "winding boards") are used. In the system described, at least the secondary side of the power transmission system is constructed with a winding board instead of a conventional winding of round, flat or HF stranded wire If a particularly flat design is to be achieved, the use of a winding circuit board is also advantageous in the primary side the iron powder composite material as magnetically active material (38, 39) in the same way.

To achieve a high transmission power, the heating of the winding boards is required. This can ideally be done by bonding the winding boards with the associated magnetically active material (see Fig. 1). This additionally leads to an increase in the mechanical stability of the power transmission system. In this case, the winding circuit board is preferably insulated electrically from the core halves or ferrite cores by a thin layer of, for example, polyimide film (so-called "Capton" film (R)) or insulation varnish. The Windungsplatine (with the optional Isolati ^¬ onsschicht) can be manufactured in a conventional large-scale production process for printed circuit boards. The winding circuit board can be manufactured from any market-standard circuit board base material (eg FR4 or high-temperature variants thereof). Common printed circuit board base material has a high mechanical strength, making it suitable for Ideally suited for use in power transmission systems. The ability to inexpensively manufacture coiled circuit boards in a large-scale process, as well as the high mechanical and thermal stability of commercially available standard circuit board base material, can ideally meet the requirements of high-strength coils for rotary transformers for contactless power transformers while maintaining cost-effective production. In prior art systems, the diodes are the rectifiers (see FIG. 5), either as individual components (eg, diodes, each diode has its own housing) or as integrated (integrated) components (all four diodes of the rectifier are housed in a housing). or as a mixed form (eg two diodes each are in a housing) executed. Both variants (in particular the integrated designs) lead to a high local heating of the diodes. As a result, the performance of the overall arrangement is often limited at high ambient temperatures. In the design described here, the diodes of the rectifier REC (see FIGS. 5 to 8) drawn as individual diodes are composed of a plurality of individual diodes (and, if appropriate, resistors) of low power. This principle is shown in FIG. 8. In order to achieve a uniform current distribution to the circuit branches (FIG. 8, circuit branches 45a), these can either consist only of a diode 45b with a power smaller than the total power required or of the series connection of a diode 45b and a resistor 45c. If a diode with a negative temperature coefficient (the conduction voltage of the diode decreases with increasing temperature) is selected as the component for 45b, 45c is required in order to prevent one of the diodes 45b from being overloaded when the individual branches are heated unevenly. If, however, a diode 45b for positive Tempe ^¬ raturkoeffizienten (the control voltage of the diode increases with increasing temperature) used (eg Siliziumkar- bid Schottky diodes), it can be dispensed 45c. The principle shown in Fig. 8 for the bridge rectifier REC can be applied in the same way also in (Fig. 6 and Fig. 7). The increase in the current carrying capacity of windings is achieved by parallel connection of conductor tracks or printed conductors. A substantial improvement to the prior art is achieved by a special structure which allows to connect a plurality of conductor lines parallel to reach a high current carrying capacity to he ^¬, while insensitivity to current crowding caused by vertical (ie axial direction 28 in FIG 1) in the conductor surface incident alternating magnetic fields. This is the essential difference to the transformers known in the prior art; the broadening of the interconnects proposed there and / or the parallel connection of entire winding layers increases the current carrying capacity of the transformer only limited. The reason for this is that the widening of the conductor tracks (which form the windings) lead to an increase of the eddy current losses, caused by the magnetic alternating field perpendicularly penetrating the conductor tracks (ie axial direction 28 in FIG. 1). A parallel connection of several layers, however, increases the eddy current losses caused by the magnetic alternating field penetrating the interconnects horizontally (ie radial direction in FIG. 1). To counteract both effects, an arrangement was developed, which distributes the individual conductor tracks on the layers of the circuit board, that the conductor tracks 1. By radial and axially symmetrical distribution of the

Counteract current displacement effect in parallel connection,

2. Rotationally symmetrical about the axis of rotation 19 can be arranged in order to achieve a high surface utilization.

Hereby is achieved that the conductor lines (preferably outside the Windungsplatine of the rotary transformer of the performance-transmission system, ie on the rectifying ^¬ ter rectifier board 43 in Fig. 1) can be connected in parallel without the magnetic additional eddy current losses caused by the radially incident Wech ^¬ selfeld comes, as is the case for example in the known from the prior art method. The design of the revolving Tragers allows to choose the width of the conductor tracks such that axially incident alternating magnetic fields generate only small We ^¬ belstromverluste and to increase the current carrying capacity of the coil to an arbitrary value by an arbitrary number of conductor lines (preferably outside, for example on the rectifier board in Fig. 1) of the Windungsplatine can be connected in parallel without the We ^¬ belstromverluste increase by radially incident magnetic Wech ^¬ self-detector. The design comes with the simplest through-hole (just one through-feed cycle, with blind vias and buried vias not required), significantly reducing production time and costs. By driving the primary side PRIM of the power transmission system by means of an inverter (FIGS. 5 to 7), a voltage U ^{x is} induced in the secondary side SEC of the power transmission system. This is rectified by the rectifier REC and smoothed by means of a capacitor 44 (FIGS. 5 to 7). The energization of the winding is possible even without the capacity 44.

The exciter winding 18 is the load to be fed therefrom.

Printed circuit board coils for high current loads can be as follows realize: ply on each copper layer of a multi-circuit board, individual scroll members 50 rea ^¬ lisiert, by vias with other, similar spiral elements 50 are connected to other layers (so-called "vias".). The spiral elements connected in series by vias form single-wire trains (so-called "strands"), which in themselves already represent a simple winding or spiral coil, but have only a limited current-carrying capacity. If the spiral elements are arranged in a suitable manner, many (non-connected) spiral elements 50 can be arranged on each copper layer (FIG. 4). The spiral elements run on the different layers alternately from the inside to the outside; For example, if a spiral segment extends from outside to inside on layer LI, it must extend to the inside of layer L2. The spiral elements, which are in the same position have the same direction. To reduce the current displacement effect (by axially incident mag ^¬ genetic alternating fields), it is necessary that there is no electrical connection between the spiral elements on the individual layers of the winding circuit board; the electrical connection of the strands or spiral coils to a winding with high current carrying capacity may only take place at the beginning and / or at the end of a strand (preferably outside the winding circuit board). The structure of the winding has been explained in an example: On a round winding board with four copper layers, a winding with five orbits (the center leg or the winding center or the rotation axis) consisting of five strands or spiral coils is realized. The strands are constructed identically, and only about the z-axis (axial direction corresponds speaks paper plane in Fig. 3 and Fig. 4) angularly offset of ^¬ sorted. In order to realize five orbits on four plies, a spiral element on a ply must comprise 5/4 = 1.25 orbits. Fig. 3 shows a single (first) spiral element on the uppermost layer LI of the winding board (which comprises 1.25 circles), next to it is shown the identically shaped, angularly offset (second) spiral element on the first inner layer L2 of the winding board; third (identically shaped, angularly offset) spiral element on the second inner layer L3 of the Windungsplatine, next to it is the fourth (identically shaped, angularly offset) Spi ^¬ ralelement on the lowermost layer L4 of the Windungsplatine. It is advantageous to start / end each spiral segment with a web of length P1 / P2, if the via has to be realized to the next layer with a diameter (eg in order to achieve a sufficient current carrying capacity of the via) which is wider than the interconnect of the spiral segment. Point A (Fig. 3) is set as the beginning point H (Fig. 3) as the end of the beach. If the points B & C, D & E as well as F & G are electrically connected with each other in the through-connection process, the beach / conductor train is electrically complete. Points A and H must be externally connected to a rectifier REC. A single beach has a limited ampacity. To a predetermined To adjust current carrying capacity, several beach angle offset to the z-axis or rotation axis (paper plane in Fig. 4) are now arranged, this is shown in FIG. 4 for the top layer LI of the winding circuit board. The points AI to A5 are the starting points of the strands AI to A5. The ends of the strands AI to A5 are located (analogous to FIG. 4) on the lowest layer L4 of the winding circuit board. All start and end points of the strands are (preferably) connected to each other at the rectifier. This results in the parallel connection of several (as many as desired) strands necessary for increasing the current carrying capacity of the winding. If starting and end points of the winding circuit board are to be shot at the rectifier with continuous pins (eg, as in FIG. 1, pins 46), it is advantageous to increase / decrease the number of orbits per spiral segment (eg from 1.25 to 1 , 3), which is a

Angular offset between the start and end point results and the points A and H (Fig. 3) in the paper plane thus do not lie exactly above each other. In interpreting the Windungsplatine the width Q is to choose the coil segments so (Fig. 4), (caused by the axially incident alternating magnetic field) a very high current carrying capacity at a reasonable We ^¬ belstromverlusten that results. The width Q can be determined by ana ^¬ lytic calculation using methods known from the literature or by FEM simulation (FEM - finite element method).

Due to the symmetrical arrangement of the start and end points, only minimal differences in tension occur between the spiral segments of a layer. Therefore, the minimum achievable value in the printed circuit board manufacturing process is sufficient for the (insulation) distance M between the strands (FIG ), for example the underlying DIN standard for air and fuel

Creepage distances to fulfill. Otherwise, the value for M specified in the standard must be used. The lengths of the webs PI & P2 are to be selected so that the insulation distances Ol & 02 between the spiral segments and the vias correspond to the underlying standard (eg standard for clearances and creepage distances). It should be noted that the voltage Difference between the via and the beach can be significantly higher than the beach segments located in the same plane of the circuit board. The use of webs (PI or P2) makes it possible to manufacture the blanking board with a single through-hole process. This reduces the costs considerably.

In order to ensure the speed resistance of the rotating parts of the power transmission system (secondary winding of the rotary transformer as well as rectifiers and smoothing capacitors), it is cast completely with potting material (eg epoxy resin) or overmoulded with plastic. The alternating current can be rectified and smoothed in a rectifier board of the secondary side. For example, the rectifier board is shown as a round part with ^¬ example 25 capacitors and 36 diodes. Al ^¬ ternative, instead of the diodes also actively rectifying components are used. For example, controlled MOSFETs. Functions required electronic components can be constructed from the interconnection of several (preferably similar) individual building elements. As individual components, the drawn in Fig. 8 elements 45a in the branches (preferably diodes with a positive Tempe ^¬ raturkoeffizienten, including Schottky diodes based on silicon umkarbid consisting) assembled to the diode element 45 45a and 45c.

For better heat dissipation from the electronic components of the rectifier board is proposed to connect the rectifier board with a heat sink directly. Printed circuit board winding consisting of parallel ^¬ single conductor trains or spiral coils for implementing high current carrying capacity of the winding circuit board are characterized in that the parallel connection of several conductor leads only to a minimal increase in eddy current losses caused by the radially incident magnetic alternating field in the winding window of the rotary transformer. In operation, all components, in particular electronic components of the secondary side of the power ^{transmission ¬} system due to the flowing electrical currents thermally very high stress. The cooling of the electrical components is often a problem with closed (potted) systems, as shown in Fig. 1 and Fig. 2. It is proposed a special cooling of the components via the following "heat path": from the components on the heat sink of the power transmission system and special highly thermally conductive epoxy resin or special highly thermally conductive plastic then on the cover of the winding head and then in the engine compartment of the electric machine, in which the rotor with the power transmission system As shown in Fig. 1, the secondary side of the power transmission system is provided with a heat sink, which is in direct contact with the cover of the winding head made of non-magnetizable steel at the coupling surface 42 ^λ and the heat from On the primary side, the heat path from the winding board passes through the ferrite core and heat sink into the motor housing or end shield.

The electronic parts of a rectifier board of the se ^¬ secondary side of the power transmission system are subjected to the most thermal. Preferably, the rectifier ^¬ board 43 is provided with an aluminum or copper core for cooling the electronic parts, which is particularly efficient thermally connected to the cover of the winding head. As shown in FIGS. 1 and 2, the heat is transferred from the rectifier board to the heat sink via direct contact. As shown in Fig. 1 and Fig. 2, for example, a plurality of metal screws for screwing the rectifier board and heat sink can be used. For example, a milled recess on the edge of the rectifier board, a direct heat-conducting contact of the rectifier board is created to the heat sink. In general, such Lei ^¬ terplatten have a core of aluminum or copper and double-sided Coating for the copper tracks, whereupon the electronic parts are soldered.

Between the copper core and the double-sided coating for the copper tracks there is an insulation layer. For direct contact between the heat sink of the power transmission system and the aluminum or copper core of the rectifier board, the insulation layer and the copper coating for the copper tracks are milled free, for example by the milling process. Other joining techniques may be used (for example caulking or riveting). Of course, copper or aluminum core of the rectifier board can be made of another good heat conducting material. If the rectifier board is not subject to high thermal stress and does not require a copper or aluminum core, a board standard process can be used in this case. For example, a rectifier board made of a standard FR4 material is used. The heat sink of the power transmission system is produced at ^¬ example of aluminum or copper for better heat dissipation. It can also be used other highly thermally conductive materials for the production of the heat sink of the Leistungsübertra ^¬ supply system. In order to connect all parts of the power transmission system mechanically, it is proposed to use an epoxy resin or plastic with high thermal conductivity value for the casting or overmolding process. Through the use of the special heat sink of the power transmission system and special epoxy resin or plastic creates a special cooling system of the secondary side SEC of the power transmission system, the heat from the

Power transmission system can safely transport away. If the power transmission system is designed as a separate component, it is proposed to the power transmission system without the rotor with a special epoxy resin or plastic with a high thermal conductivity value spill or overmold. As shown in FIGS. 1 and 3, all the cavities of the power ^transmission system are filled. The encapsulation or encapsulation by means of injection molding not only give the power transmission system the necessary speed stability, but also ensure reliable heat dissipation from the electronic components of the power transmission system via the heat sink on the cover of the winding overhang. Casting with epoxy resin or overmoulding with a plastic mechanically stabilizes the rotor with the power transmission system in order to achieve the necessary speed stability

The permanently installed in the end shield or in the housing part of the primary side PRIM of the power transmission system is not stressed during operation with high forces. In contrast, all electronic components of the secondary side SEC of the power transmission system must be secured in ^¬ example against high centrifugal forces. In order to ensure the speed stability, usually all rotor components are cast in an externally excited synchronous machine with an epoxy resin or a plastic. The design shown in FIG. 1 permits casting with an epoxy resin or molding with plastic all rotor components and at the same time all components of the power transmission system in a casting or injection process.

Overall, the example shows how can be provided by the invention, a non-contact power transmission for externally excited Synchronma ^¬ machines for traction drives with high engine speed. Reference sign list

10 motor vehicle

11 traction drive

12 electric machine

13 inverters

14 traction battery

15 stator winding

16 stator

17 rotor

18 excitation winding

19 rotation axis

20 wave

21 rotary joints

22 Primary coil arrangement

23 Secondary coil arrangement

24 Motor housing or end shield

25 spring element

26 bearings

27 circlip

28 Axial direction

29 laminated core

30 winding head (the exciter winding 18)

31 Winding head cover

32 potting

32 ^λ casting

33 wire

33 ^λ casting or encapsulation

34 heat sink

35 connection board

36 metal pin

37 Primary winding of winding plate

38 ferrite core

39 ferrite core

40 Radial air gap

40 ^λ Axial air gap

41 Secondary winding of winding plate

42 heat sink 43 rectifier board

44 capacitor

45 diode

45a branch branch

45b single diode

45c resistance element

46 metal pin

47 hooks

48 screw

49 trace

50 spiral element

51 offset angle

52 vias

53 four-quadrant station

53 ^λ capacity

53 "freewheeling diode

54 center tap

PRIM primary page

REC rectifier circuit SEC secondary side

Claims

claims

A contactless power transmission system (21) for generating a current in a field winding (18) of a rotor (17) of an electric machine (12), wherein a primary-side

Winding (22) for arranging on a motor housing or bearing plate (24) of the electric machine (12) and for generating an alternating magnetic field and a secondary-side winding (23) for arranging on an end face of the rotor (17) and for converting the alternating magnetic field in an AC voltage (U ^x ) are provided, and wherein a rectifier circuit (43) connected to the secondary-side winding (23) is provided with a rectifier circuit (REC) for providing one of the AC voltage (U ^x ) between two connection contacts (47) for the exciter winding (18 ) and wherein the secondary-side winding (23) is formed on the basis of conductor tracks (49) of a winding plate (41), characterized in that the secondary-side winding (23) comprises a plurality of parallel spiral coils (AI, A2 , A3, A4, A5) and each of the spiral coils (AI, A2, A3, A4, A5) is formed of a plurality of spiral elements (50) and for this purpose the winding plate (41) is configured in several layers and in each layer (LI, L2, L3, L4) of the winding plate (41) several of the spiral elements (50) are offset from one another by an angular offset (51) and in each case one of the spiral elements (50) each layer (LI, L2, L3, L4) belongs to one of the spiral coils (AI, A2, A3, A4, A5) and for each of the spiral coils (AI, A2, A3, A4, A5) their respective spiral elements (50) of all layers (LI, L2, L3, L4) are connected in series by means of plated-through holes (52) of the winding plate (41).

2. Power transmission system (21) according to claim 1, wherein for a heat dissipation of the power transmission system (21), the rectifier board (43) is directly connected to a heat sink (42) and a secondary-side ferrite core (39) of the power transmission system (21) with the heat sink (42 ) and the heat sink (42) is arranged to Heat from the rectifier board (43) and the ferrite core (39) towards a coupling surface (42 ^λ ) of the heat sink (42), via which the heat sink (42) on a support member (31) of the rotor (17) can be fastened ,

3. power transmission system (21) according to claim 2, wherein for a rotational speed of more than 15,000 revolutions per minute and / or for heat conduction, the rectifier board (43), the heat sink (42), the Windungsplatine (41) and the ferrite core (39) with a synthetic resin (32 ^λ ) potted or with a

Plastic are injected.

4. power transmission system (21) according to any one of claims 2 or 3, wherein the rectifier board (43) has a metal core for heat conduction and the heat sink is directly in contact with the metal core.

5. power transmission system (21) according to any one of the preceding claims, wherein on the rectifier board (43), the rectifier circuit (REC) comprises a plurality of similar, in scarf ^¬ processing branch (45a) connected in parallel electronic A ^¬ zelbauelemente (45b).

6. power transmission system (21) according to claim 5, wherein at least some of the individual components (45b) for adjusting a current distribution in each case an electrical resistance ^¬ component (45c) in the respective circuit branch (45a) is connected upstream.

7. power transmission system (21) according to any one of the preceding claims, wherein the spiral coils (AI, A2, A3, A4, A5) in the region of the winding plate (41) are electrically insulated from each other and the parallel connection of the spiral coils (AI, A2, A3, A4 , A5) is provided outside the winding circuit board (41), in particular on the rectifier board (43).

8. power transmission system (21) according to any one of the preceding claims, wherein at each layer (LI, L2, L3, L4) a electrical potential of the spiral elements (50) of the respective layer (LI, L2, L3, L4) is aligned and for this purpose the spiral coils (AI, A2, A3, A4, A5) at a respective coil start with a common first input of the rectifier circuit (REC) and are electrically connected at a respective coil end to a common second input of the rectifier circuit (REC).

9. power transmission system (21) according to one of vorherge- Henden claims, wherein each of said spiral coils (AI, A2, A3, A4, A5) U orbits and the Windungsplatine N layers be ^¬ riding trips (41), and each helical element (50) U / N has orbits on ^¬.

10. Power transmission system (21) according to any one of the preceding claims, wherein each of the terminal contacts (47) is configured in each case as a hook, on each of which a wire (33) of the excitation winding (18) can be wound, each hook directly to the rectifier board ( 43) is attached.

11, power transmission system (21) according to any one of the preceding claims, wherein the spiral elements (50) of the second därseitigen winding (23) on the winding plate (41) about the respective angular offset (51) are rotationally symmetrical.

12. Power transmission system (21) according to one of the preceding claims, wherein the plated-through holes (52) extend completely through all the layers (LI, L2, L3, L4) of the winding plate (41).

13. Power transmission system (21) according to any one of the preceding claims, wherein the primary-side winding (22) also has a winding plate (37) of the type mentioned.

Electrical machine having 14 (12), which is designed as a separately excited Syn ^¬ chronmaschine and a Leistungsübertra ^¬ supply system (21) according to any one of the preceding claims.

15. motor vehicle (10) having an electric machine (12) according to claim 14, wherein the electrical machine (12) as a traction drive (11) for the motor vehicle (10) is configured and connected to an inverter (13), which is for a speed of the electric machine (12) of more than 15,000 revolutions per minute is established.