CN212518805U

CN212518805U - Power transmission system for generating an electric current in an excitation winding of a rotor of an electric machine, electric machine and motor vehicle

Info

Publication number: CN212518805U
Application number: CN201890001116.9U
Authority: CN
Inventors: M·布拉托夫; W·哈克曼; H·克虏伯
Original assignee: Vitesco Technologies GmbH
Current assignee: Vitesco Technologies GmbH
Priority date: 2017-08-23
Filing date: 2018-08-07
Publication date: 2021-02-09
Anticipated expiration: 2028-08-07
Also published as: DE102017214766B4; DE102017214766A1; WO2019038080A1

Abstract

The invention relates to a power transmission system (21) for generating a current in an excitation winding (18) of a rotor (17) of an electric machine (12), wherein a secondary winding (23) is provided for arrangement on the rotor (17) and a rectifier circuit board (REC) is provided which is connected to the secondary winding (23) and is used for providing a direct voltage (U) generated between two connection contacts (47) of the excitation winding (18). The invention proposes that the winding circuit board (41) of the secondary winding (23) is provided with a plurality of parallel-connected spiral coils (A1, A2, A3, A4, A5) and that each of the spiral coils (A1, A2, A3, A4, A5) is formed by a plurality of spiral elements (50), and that the winding circuit board (41) is furthermore designed in a multi-layer manner, and that in each layer (L1, L2, L3, L4) of the winding circuit board (41) a plurality of the spiral elements (50) are arranged offset in relation to one another by an angular offset (51), respectively, and that for each of the spiral coils (A1, A2, A3, A4, A5) the respective spiral elements (50) of all layers (L1, L2, L3, L4) thereof are connected in series by means of the series-connected spiral elements (52) of the winding circuit board (A1, A2, A3, A4, L4).

Description

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

Technical Field

The invention relates to a power transmission system for generating an electric current in an excitation winding of a rotor of an electric machine. The power transfer system has a rotating transmitter, i.e., an inductive coupler. By means of the power transmission system, a direct voltage can be generated contactlessly in order to drive a current in the excitation winding of the rotor of the electrical machine. The invention also relates to an electric machine having such a power transmission system and to a motor vehicle having an electric machine according to the invention.

Background

A rotary transmitter of this type is known from DE 102014202719 a 1. Accordingly, a power transmission system for an electric machine has a primary winding of a rotary transmission for a spatially fixed arrangement in the electric machine and for generating an alternating magnetic field. In addition, the power transmission system has a secondary winding of the rotary transformer for arrangement at an end face of a rotor of the electric machine and for converting a temporally changing magnetic flux into an alternating voltage, and a rectifier circuit board with a rectifier circuit for rectifying the alternating 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 rotate together with the secondary winding, i.e. in the alternating magnetic field of the primary winding. The rectifier circuit board of the rectifier, which is connected to the secondary winding, is adapted to generate a direct voltage from the alternating voltage generated by the secondary winding and to supply this direct voltage to the connection contacts for the excitation winding. That is, when a direct voltage is generated at the two connection contacts, a current in the excitation winding always flows. As is known from the prior art, the secondary side winding can be formed on the basis of the conductor path of the circuit board. Such a circuit board with conductor paths for the windings is referred to below as a wound circuit board (windingsplatine). The term "winding" is understood here not to mean a wound wire, but rather the function of an electrical winding, that is to say an assembly with an electrical coil.

The described contactless transmission system, in which the exciter coil is supplied with a dc voltage using a rotationally symmetrical transformer or a rotary transformer, can be used instead of a slip-ring carbon brush system in externally excited synchronous machines. The use of a wound circuit board has the advantage over the use of a secondary side winding based on stranded or round wires that the secondary side winding can be designed to be more flat.

However, a conflict arises with regard to the necessary winding of the secondary winding in the case of the use of a wound circuit board with conductor paths. In order to be able to carry sufficiently large currents, the conductor paths must be correspondingly designed to be wide. However, this leads to the following disadvantages: eddy currents are induced within the conductor path in the alternating magnetic field, which in turn adversely affect the power of the rotating transmitter, i.e. reduce the electrical power available at the output.

The following principles are known from US 6664883B 2: the helical coils are distributed over multiple layers of a multilayer wound circuit board. The alternate winding of the primary and secondary coils of the transformer is achieved in a wound circuit board. The primary coil and the secondary coil are therefore not movable relative to each other and are not suitable for use as a rotary transmitter.

DE 202012002027U 1 discloses a rotor for an electric machine, in which a winding head cover is arranged on the end face in order to cover the winding head of the rotor. A sensor track of a rotary position encoder (drehlagebers) is disposed on the winding head covers.

DE 202012002024U 1 discloses a rotor with a winding head cover, in which a momentum ring (Wuchtring) is arranged to compensate for an imbalance of the rotor.

Disclosure of Invention

The object underlying the invention is to provide a power transmission system for contactless transmission of electrical power for an electrical machine in order to drive an excitation winding. The system comprises: for generating an electric current in an excitation winding of a rotor of an electric machine, wherein a primary side winding for arrangement at an engine housing or at an end shield of the electric machine and for generating an alternating magnetic field and a secondary side winding for arrangement at an end side of the rotor and for converting the alternating magnetic field into an alternating voltage are provided, and wherein a rectifier circuit board connected to the secondary side winding is provided, which rectifier circuit board has a rectifier circuit in order to provide a direct voltage, which direct voltage is generated from the alternating voltage between two connection contacts for the excitation winding, and wherein the secondary side winding is formed on the basis of a conductor path of a wound circuit board, which secondary side winding is provided with a plurality of spiral coils connected in parallel, and each of the spiral coils is constituted by a plurality of spiral elements, and in addition the winding circuit board is designed in a multi-layer manner, and in each layer of the winding circuit board, a plurality of spiral elements of the spiral elements are respectively arranged in an angle offset manner relative to each other, and correspondingly one of the spiral elements of each layer respectively belongs to one of the spiral coils, and for each of the spiral coils, the corresponding spiral elements of all layers are connected in series by means of the through contact part of the winding circuit board.

The invention proceeds from the initially described contactless power transmission system with a primary side winding, a secondary side winding and a rectifier circuit board with a rectifier circuit.

The invention also uses a wound circuit board for providing the secondary side winding in the form of a conductor path. In general, the winding circuit board must have the form of a ring which can be applied to the shaft of the rotor or can be arranged around the shaft of the rotor. Now, according to the invention, the secondary winding has a plurality of parallel-connected spiral coils, wherein each of these spiral coils is formed from a plurality of coil sections or coil elements. The helical coil is not necessarily referred to herein as a circular coil. The helical coils may have a circular or other geometry that is rotationally symmetrical or rotationally symmetrically arranged with an angular offset. The spiral coils generally form individual conductor strips or individual windings. To form the spiral coil, the wound circuit board is designed in multiple layers. I.e. to a so-called multilayer circuit board (multilayer PCB, PCB being a printed circuit board). Each Layer of the wound circuit board (Layer) can have a plurality of conductor paths in a known manner. A plurality of the spiral elements of the spiral coils are arranged in each layer of the wound circuit board, to be precise one spiral element before each spiral coil. The helical elements of each layer are preferably concentric and are respectively arranged offset with respect to one another by an angular offset. The concentric arrangement is derived with respect to the rotational axis of the rotor. I.e. the helical elements may be arranged in a circle or in a ring around the rotational axis of the rotor. Each helical element is offset by a predetermined angular offset relative to a respective adjacent helical element.

I.e. each spiral coil has only one spiral element per layer of the wound circuit board. For each spiral coil, the respective spiral units of all layers of its wound circuit board are connected in series by means of through contacts of the wound circuit board. The spiral elements of adjacent layers are electrically coupled directly here. That is, a spiral coil is generated from the uppermost layer of the wound circuit board in the following manner: the spiral element of this layer is electrically connected to the spiral element of the layer below it and this spiral element is in turn electrically connected to the spiral element of the layer below it, and so on, until the last spiral element of the lowermost layer is reached. The ends of each spiral coil are then connected to the rectifier circuit board. With the described arrangement, the spiral coils are here arranged distributed over a plurality of layers of the wound circuit board and are intertwined or interlaced with one another. I.e. they do not have the flat or plate-like shape that is otherwise common.

The invention has the advantage that the current-carrying capacity of the parallel circuit formed by the spiral coils is higher than that of each individual spiral coil. Eddy currents are still not caused between the spiral coils due to the electrical separation of the individual spiral elements on each layer of the wound circuit board. That is, it is thus possible to balance the number of spiral coils connected in parallel with respect to the width of each conductor path of the individual spiral coils in order to achieve a maximum current carrying capacity of the total assembly (parallel circuit) without generating excessive total losses (which may set thermal limits). The narrower the conductor path, the less eddy current losses in each individual conductor path, but the current carrying capacity of each individual conductor path decreases. The more spiral coils connected in parallel, the greater the current carrying capacity of the overall assembly. The rectifier circuit board is also referred to below simply as rectifier for the sake of brevity.

The invention also comprises advantageous developments, by means of which further advantages are achieved.

Other adverse effects of power (output power) may result from heating the conductor path and the rectifier. In order to dissipate heat from the power transmission system, it is proposed that the rectifier circuit board is connected directly to a heat sink, and the secondary-side ferrite core of the power transmission system is in contact with the heat sink, and that the heat sink is adapted to conduct heat from the rectifier circuit board and the ferrite core to a coupling surface of the heat sink, by means of which coupling surface the heat sink can be fastened to the carrier component of the rotor. Such a carrier member may be, for example, the winding head cover of the excitation winding of the rotor mentioned at the outset. Such winding head covers are metallic, annular cover parts which can be placed over the winding head of the excitation winding. Suitable materials for the winding head cover are alloys, as are given in the documents DE 202012002024U 1 and DE 202012002027U 1 mentioned at the outset, the contents of which are considered here as an integral part of the invention in connection with the design of the alloy and the winding head cover.

What is important is the design of the thermal path. In particular, heat can be dissipated from the rectifier circuit board via the cooling body on the one hand and from the ferrite core via the cooling body on the other hand to its coupling surface, respectively, where it is transferred into the carrier component of the rotor, in particular into the winding head cover. In particular, a purely passive cooler, i.e. no active cooler, is provided in the power transmission system. Passive coolers refer to coolers based on heat conduction. The power transmission system of the present invention may be designed as a separate component for installation into the motor or integrated into the winding head cover.

Another important characteristic of power transmission systems is rotational speed stability. In a further development, the rectifier printed circuit board, the heat sink, the winding printed circuit board and the ferrite core are cast from an artificial resin or overmolded with plastic for rotational speed stability of more than 15000 rpm and/or for thermal conduction. The casting may be performed with epoxy or adhesive. The casting and overmolding provide stabilization and mechanical fixation, respectively, for rotational speeds up to and exceeding 15000 revolutions per minute. Otherwise the soldered connections in, for example, a rectifier circuit board will break after a long time. By casting and/or overmolding with plastic by means of an injection molding process, the power transfer system is stable to rotational speeds of greater than 15000 revolutions per minute.

Casting and overmolding, respectively, also provide the following advantages: a better thermal conductivity than with air can be achieved. Thermal conductivity of up to 1 to 2W/mK can be achieved by selecting synthetic resins or plastics. Thermal conductivity of 0.3W/mK can also be achieved with conventional epoxy resins. That is, the heat sink comprises in particular a heat path which connects the rectifier circuit board to the carrier component via the cooling body and the potting compound/plastic overmold, and a heat path which connects the ferrite core to the carrier component via the cooling body and the potting compound/plastic overmold. Heat can also be removed from the windings through the casting material/plastic overmold.

The primary heat source is the diodes, windings and secondary side ferrite cores of the rectifier. Less heat loss occurs due to the capacitor and the conductor path of the rectifier circuit board. By means of the potting/overmolding, it is possible to provide an additional heat transfer path for the heat to be transported away from the heat source. The heat can then be conducted into the carrier component, in particular the winding head cover, by the potting/overmolding and by the cooling body.

One refinement provides that the rectifier circuit board has a metal core for heat conduction and the heat sink is in direct contact with the metal core. Heat can thereby be removed from the individual electrical and/or electronic components of the rectifier and conducted via the metal core to the heat sink. The metal core may have copper and/or a copper alloy and/or aluminum and/or an aluminum alloy. Copper has a greater thermal conductivity than aluminum. In order to reach the metal core in the rectifier circuit board with the cooling body, the cover layer of the rectifier circuit board can be removed, for example, by milling. The core is milled out and the cooling body is then brought directly into contact with the core.

In order to ensure reliable heat transfer from the rectifier circuit board into the heat sink, the rectifier circuit board can be screwed to the heat sink. The bolts are preferably formed of metal, thereby additionally facilitating heat transfer. The heat sink can, for example, lie flat on a milled-out surface of the core of the rectifier circuit board.

Another possibility for reducing the heating up of the construction element is derived in the following way: on the rectifier circuit board, the circuit of the rectifier has a plurality of individual components (in particular diodes) of the same electronic type, which are arranged in parallel-connected circuit branches. In other words, the power losses occurring during the rectification of the alternating voltage are not converted directly in the individual components, but are distributed over a plurality of parallel-connected individual components, in particular over parallel-connected diodes. The generation of lost heat is therefore locally distributed, i.e. distributed over a plurality of individual construction elements. A separate structural element refers to a separate electronic component which can be soldered, for example, with connection contacts or pins to the rectifier circuit board.

In order to ensure that the individual construction elements are uniformly loaded with current, resistive construction elements can be connected upstream of at least some of the individual construction elements in each case in order to regulate the current distribution. That is to say that the resistive components are each connected in series with one of the individual components in the circuit branch. This makes it possible to achieve a uniform current distribution between the individual components connected in parallel. In particular, each circuit branch has only the individual component and the associated resistance element and the associated conductor path and welding point. The use of a resistor unit is advantageous in particular at the negative temperature coefficient of the diode.

As already mentioned, the spiral coils are electrically insulated from one another in the region of the winding of the circuit board, in order to thus suppress eddy currents between the conductor paths of the different spiral coils. The parallel connection of the spiral coils is preferably carried out outside the winding circuit board, i.e. in particular on the rectifier circuit board. Thereby minimizing the influence of the alternating magnetic field on the generation of the eddy currents.

In order to effectively electrically insulate the conductor paths of the spiral coil from one another, it is ensured in particular that in each layer of the wound circuit board the potentials of the spiral elements of the respective layer are identical. For example, the start of the coil at the first outer layer is connected to the potential of the first input of the rectifier circuit and can be connected to the windingThe coil terminals opposite the first outer layer of the circuit board are connected to the potential of the second input of the rectifier circuit. The sections of the spiral element having the same radial distance each have such a small potential difference between each of the layers of the wound circuit board lying therebetween that a breakdown is prevented

By the equivalent potential, voltage breakdown between the spiral elements is prevented. The potential within each layer is naturally not constant.

In terms of the shape of the individual spiral element of each spiral coil, its shape can be obtained by the following calculation. Each of these spiral coils may have U turns or spiral loops. The wound circuit board may provide N layers. Each helical element then has U/N turns. That is, in the case where the wound circuit board has 4 layers and the helical coil has U ═ 5 turns, each helical element is a helix having a helical center turn number of 1.25. If the starting and end points of each spiral coil wound around the circuit board are connected to the rectifier circuit board with through pins, it is advantageous to increase/decrease the number of turns of each spiral element (for example from 1.25 to 1.3) such that an angular offset is created between the starting and end points and therefore the connection points of the spiral coils do not exactly overlap one another. A number of turns U that is not an integer is thus produced (i.e. U1.3 x 4 5.2 in this example). By connecting the spiral elements of the individual spiral coils in series on a plurality of layers, a common current flows through the spiral elements, which common current alternately flows spiraling inward in one spiral element and spiraling outward in the next spiral element.

The spiral elements of the secondary winding are preferably arranged rotationally symmetrically on the winding circuit board with a corresponding angular offset. That is, the arrangement of the helical elements on each layer is a rotationally symmetrical configuration in which rotational symmetry is always produced at an angular offset (at which adjacent helical elements are offset, respectively) upon rotation. Thereby using the available construction space.

In order to be able to produce the power transmission system particularly cost-effectively, the through-contacts are designed as simple through-contacts, i.e. are guided completely through all layers of the wound circuit board. Such a complete through contact or VIA (vertical interconnect access) can be manufactured in a single, per se known through contact process.

Another aspect relates to electrically connecting the excitation winding of the rotor with the connection contact of the rectifier circuit board. Each connection contact is preferably designed as a hook, to which the wire of the excitation winding can be brought into contact. Each of these hooks is directly electrically and mechanically connected to the rectifier circuit board. Each wire of the excitation winding is electrically and mechanically connected to one of the hooks.

The primary winding can likewise have a wound circuit board of the type described. The power transmission system is thus of a more flat design than a primary winding based on windings formed from conventional metal wires.

The invention further proposes to provide an electric machine which is designed as an externally excited synchronous machine and has an embodiment of the inventive power transmission system. The power transmission system of the invention makes the motor more robust against the effects caused by dirt (e.g. oil or dust) and does not produce wear as in the case of slip rings.

The invention also relates to a motor vehicle having an embodiment of the inventive electric machine. The electric machine is designed as a traction drive for a motor vehicle and is connected to an inverter which is adapted to a rotational speed of the electric machine of more than 15,000 revolutions per minute. By using the power transmission system of the invention, which is efficient and stable at high rotational speeds, a motor is produced which is insensitive to environmental influences.

The motor vehicle of the invention may be, for example, a car or a truck or a forklift.

Drawings

Fig. 1 shows a schematic view of a longitudinal section of an externally excited rotor with a brushless power transmission device;

FIG. 2 is a schematic view in longitudinal section of a secondary side of the power transfer system of the rotor of FIG. 2;

fig. 3 is a schematic diagram of the layers of the wound circuit board of the secondary side of the power transfer system of fig. 2, in which only a single helical element of the plurality of helical elements is shown, respectively;

fig. 4 is a schematic top view of a wound circuit board of the secondary side of the power transfer system;

fig. 5 is a schematic circuit diagram of a 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;

FIG. 8 is a schematic diagram showing the thermal distribution of diodes of a rectifier circuit of a power transfer system; and is

Fig. 9 shows a schematic view of an embodiment of the motor vehicle of the invention.

Detailed Description

This example relates to a preferred embodiment of the invention. In this exemplary embodiment, the described components of the exemplary embodiment each form separate inventive features which are to be regarded as independent of one another, which further form the invention independently of one another and can therefore also be regarded as a constituent part of the invention in combinations different from the combinations shown. The described embodiments can additionally be supplemented by further features of the invention already described.

In the figures, elements having the same function are provided with the same reference numerals, respectively.

As an overview, reference is first made to fig. 9. Fig. 9 shows a motor vehicle 10, which may be in particular a motor vehicle, for example a car. The motor vehicle 10 may have an electric traction drive 11, which may be formed on the basis of an electric machine 12. An inverter 13 and a traction battery 14 are additionally shown. The traction battery 14 can be, for example, a high-voltage battery, which can provide a voltage of more than 60V, in particular more than 100V. The inverter 13 can generate phase currents for the stator windings 15 of the stator 16 of the electric machine 12 from the direct voltage of the traction battery 14 in a manner known per se. The phase current through the inverter 13 can generate a rotating magnetic field inside the stator 16 by means of the stator winding 15.

A rotor 17 may be rotatably mounted inside the stator 16. The electric machine 12 may be an externally energized synchronous machine. For this purpose, a field winding 18 is provided in the rotor 17, through which direct current can flow. However, the rotor 17 generates magnetic poles at its outer periphery, which exchange with the rotating magnetic field of the rotor 16, thereby generating a rotational motion of the rotor 17. The rotor then rotates about the axis of rotation 19 and in the process rotates the shaft 20, by means of which the drive torque can be transmitted to the wheels of the motor vehicle 10.

To generate current in the excitation winding 18, the electric machine 12 may have a power transmission system 21. Electrical energy can be transferred from the stationary primary side PRIM to the rotating secondary side SEC in a contactless manner on the basis of inductive transfer by means of the power transfer system 21. In addition, the power transmission system 21 can have a rotary transmission with a primary side winding 22 at the engine housing or end shield and a secondary side winding 23 at the rotor 17.

Fig. 1 shows a power transmission system 21 in longitudinal section. Fig. 1 is mirror-symmetrical with respect to the axis of rotation 19, so that reference numerals are given on only one side of the axis of rotation 19 in each case. These reference numerals also apply mirror-symmetrically to the opposite side.

The power transfer system 21 has the following advantageous characteristics:

the power transmission system is a cost-effective contactless power transmission system for a traction drive:

1) instead of windings formed from round or flat wires, multilayer circuit boards ("wound circuit boards", "multilayer PCBs") with special structures are used for the rotating side of the rotary transformer in order to avoid current suppression effects

The copper layers are structured on the layers of the circuit board in such a way that they produce windings;

2) the stationary side of the rotary conveyor can also optionally be realized with a multilayer wound circuit board in order to avoid current suppression effects, or with windings formed from round wires, flat wires or HF strands in a conventional construction;

3) special heat sinks for the primary-side and secondary-side rotary transformers are provided;

4) in order to optimize the heat dissipation of the rectifier, its circuit is composed of a plurality of individual elements of the same type, for example in the manner shown in fig. 8;

5) high stability to rotation speed (over 15000 min-1);

6) by using a special configuration of the rotary transmitter it is possible to use a large air gap in the radial direction (radius greater than or equal to 0.7mm) as well as in the axial direction (greater than or equal to 2 mm);

7) the simplest embodiment of a through contact for the circuit board winding can be used;

8) the symmetrical arrangement of the conductor paths (also referred to herein as "strands") wound around the circuit board achieves a high packing density.

In order to ensure the rotational speed stability of the rotating part of the rotary transmission (secondary side of the rotary transmission and rectifier and smoothing capacitor), it is completely cast or overmolded with a casting material (e.g. epoxy or plastic).

The alternating current should be rectified and smoothed in a rectifier circuit board on the secondary side. For example, the rectifier circuit board is formed as a circular part having, for example, 25 capacitors and 36 diodes. Alternatively, instead of diodes, actively rectifying components can also be used. Such as a controlled MOSFET.

A contactless power transmission system based on a rotary transmitter may have a rectifier constructed from a connection of a plurality of (preferably the same type of) individual components. These individual components, preferably consisting of diodes with a positive temperature coefficient, for example schottky diodes based on silicon carbide, are connected in parallel-connected branches.

In order to better dissipate heat from the electronic components of the rectifier circuit board, it is proposed that the rectifier circuit board is directly connected to the heat sink.

In order to better extract heat from all components of the transfer process, special epoxy resins with higher thermal conductivity are used.

The circuit board winding (wound circuit board) has parallel-connected spiral coils formed from individual conductor strips (strands) which are used to achieve a high current-carrying capacity of the wound circuit board. The parallel connection of the plurality of conductor strips only achieves a minimization of the increase in eddy current losses caused by the alternating magnetic field entering in the winding window of the rotating transmitter.

The special geometry of the individual parts of the transfer process enables them to be produced cost-effectively and still perform their function.

Fig. 1 shows the floating bearing side (non-drive side) of the motor 12 in detail. An end shield or engine housing 24 and a spring element 25 are shown. Such an assembly may alternatively also be provided on the fixed bearing side.

The shaft 20 of the rotor 17 is rotatably mounted at an end shield or engine housing 24 via a bearing 26. The securing ring 27 can fix the bearing 26, for example, in the axial direction 28 along the axis of rotation 19 in a slip-proof manner. Furthermore, the plate pack 29, the winding head 30 of the excitation winding 18, the cover 31 of the winding head 30 with the potting compound 32 arranged therein, and the wires 33 of the excitation winding 18 are shown in the rotor 17. The wire 33 may be electrically and mechanically engaged to the power transfer system 21.

The power transmission system has a stationary or primary side PRIM and a secondary side SEC fastened at the rotor. The primary side PRIM and the secondary side SEC are respectively formed as rings, which are arranged around the shaft 20. The secondary side SEC may be arranged at an end side of the rotor 17.

In the power transmission system 21, the primary winding 22 on the primary PRIM, the heat sink 34, the connection board 35 for supplying the supply voltage (electrical lines not shown on the way), the metal pins 36 for the winding board 37 facing the primary winding 22, which are in through contact with the connection board 35, and the primary ferrite core 38 are shown.

The ferrite core 38 of the primary side PRIM forms a complete magnetic loop together with the ferrite core 39 of the secondary side SEC. A radial air gap 40 is produced in the magnetic loop, via which the alternating magnetic field generated by the primary winding 22 can be transferred into the ferrite core 39 of the secondary side SEC. Because of the radial air gap 40 involved, its air gap dimension is not changed in the axial direction 28 as the shaft 20 moves axially. By the axial movement the axial air gap 40' is changed. The

ferrite cores

38, 39 each have an L-shaped profile. Axial tolerances can thereby be compensated. The larger the gap size of the radial air gap, the less power can be transmitted. Naturally, other profiles, such as E-shaped profiles, can also be used.

In the secondary side SEC are additionally shown: a winding circuit board 41 of the secondary side winding 23, a cooling body 42, a rectifier circuit board 43 having a rectifier circuit (including a capacitor 44 and a diode 45), metal pins 46 by which the winding circuit board 41 is electrically connected to the rectifier circuit board 43, and hooks 47 at which the wires 33 of the excitation winding 18 are placed. The hook 47 is also called a winding hook. These hooks form the connection contacts of the rectifier circuit, respectively. The rectifier printed circuit 43 can be fastened directly to the heat sink 42 by means of metal screws 48. The heat sink 42 bears with a coupling surface 42' against the covering part 31. May involve a press fit. The covering member may be made of a specific metal or a specific metal alloy. Examples of suitable covering materials can be found in the documents DE 202012002027U 1 and DE 202012002024U 1.

Fig. 2 shows an enlarged view of an upper part of the secondary side SEC as shown in fig. 1. It is shown how the intermediate space is filled or filled with a casting compound formed from epoxy resin or by means of overmolding by means of plastic. Such a casting or such an overmold 32' improves the stability of the secondary side SEC with respect to high rotational speeds. The power transfer system 21 is thus speed stable for rotational speeds greater than 15000 revolutions per minute. Furthermore, the potting or overmolding 32' provides a solid-based heat transfer from the rectifier circuit board 43 to the heat sink 42. The cooling body 42 can then transfer heat into the covering member 31.

Fig. 3 shows the construction of the wound circuit board 41 and optionally also the wound circuit board 37. Each of the wound circuit boards 37, 41, but in particular the wound circuit board 41 of the secondary side SEC, can be constructed in a multilayer manner. In the example shown, the wound circuit board has N-4 layers L1, L2, L3, L4, respectively, which are shown next to one another in fig. 3. Shown is the conductor path 49 of a single spiral coil a 1. Each conductor path 49 of each layer L1, L2, L3, L4 has the form of a spiral element 50. The spiral coil a1 has a total of 5 turns U, which are distributed over 4 layers L1, L2, L3, L4. Thus, each helical element 50 effectively has U/N turns, i.e., 1.25 turns in the illustrated case.

Fig. 4 shows how, for a plurality of spiral coils a1, a2, A3, a4, a5 on one single layer (here, for example, the outer layer L1), the conductor paths 49 of the spiral elements 50 of a plurality of spiral coils a1, a2, A3, a4, a5 can be arranged concentrically around the axis of rotation 19 and offset with respect to the adjacent spiral elements 50 by angular offsets 51, respectively. The angular offset 51 is derived from the number of spiral coils a1, a2, A3, a4, a 5: 360 deg./number of spiral coils. Furthermore, through-contacts 52 are shown, by means of which the helical elements 50 of each coil can be connected in series.

Fig. 5 shows a possible circuit diagram of the power transfer system 21. An alternating voltage for the primary winding 22 can be generated from the supply voltage by means of an H-bridge 53 on the primary side PRIM. The control logic of the H-bridge 53 is not shown in fig. 5. By means of the capacitance 53 ', the resonant behavior of the winding 22 can be adjusted in combination with the capacitance 53'. The capacitor 53' is optional.

An alternating voltage U' is generated on the secondary side SEC at the secondary winding 23. The alternating voltage U' can be rectified on the secondary side SEC by means of the diode 45 of the rectifier circuit REC. The diode 45 and the capacitor 44 are shown here as simple components. They may also each be composed of a plurality of elements of the same type connected in parallel, as will also be explained in connection with fig. 8. That is, a plurality of individual diodes connected in parallel may be provided at the diode 45, and a plurality of individual capacitors connected in parallel may be provided at the capacitor 44. The generated dc voltage U can be transmitted to the wire 33 of the excitation winding 18 via the hook 47.

Fig. 6 shows an alternative circuit diagram of the power transfer system 21. Only two transistors are required on the primary side PRIM instead of the four transistors of the H-bridge. Instead of this, a bridge circuit formed of two transistors and two freewheeling diodes 53 "is provided. A rectifier circuit with fewer diodes 45 than the circuit diagram according to fig. 5 can thus also be realized on the secondary side SEC.

Fig. 7 shows an alternative circuit diagram of the power transmission system 21, in which an H-bridge 53 with a capacitance 53' is again arranged on the primary side PRIM. An intermediate tapping point 54 is provided at the winding 23 on the secondary side SEC, which makes it possible to provide a rectifier circuit REC with fewer diodes 45 than the circuit diagram according to fig. 5. The capacitor 53' is optional.

Fig. 8 shows a circuit diagram by means of which it is explained how individual diodes 45 can be formed from a plurality of individual construction elements 45 b. The individual building elements 45b are arranged in a parallel circuit formed by the circuit branches 45a, wherein a resistive element 45c can be connected in series in order to homogenize the current distribution of each individual building element 45b in the circuit branch 45 a. Overall, the parallel circuit branch 45a of its parallel circuit thus overall produces the function of the individual diode 45.

The contactless power transfer system may be selectively mounted on the fixed bearing side or the floating bearing side of the rotor. In addition, only the placement on the floating bearing side (not the drive side) is described, since this is advantageous for the traction machine. Instead of conventional windings, specially constructed, multi-layered conductor plates (referred to herein as "wound circuit boards") are used in the power transfer systems described herein. The copper layers of the individual layers of the wound circuit board are structured in such a way that they can replace windings formed from round wires, flat wires or HF strands (HF-high frequency) when used in power transmission systems. In the described system, at least the secondary side of the power transfer system is constructed with a wound circuit board (instead of a conventional winding formed of round wire, flat wire or HF twisted wire). The primary side can also optionally be formed with a wound circuit board or a conventional winding formed from round wire, flat wire or HF twisted wire. If a particularly flat design is to be realized, it is advantageous to use a wound circuit board also in the primary side. The wound circuit board is suitable for use in the same manner as a rotary transmitter of magnetically active material (38, 39) of iron plate, ferrite or iron powder composite.

In order to achieve high transmission power, the winding circuit board needs to be heat-dissipated. This can ideally be done by gluing the winding printed circuit board to the associated magnetically active material (see fig. 1). This additionally leads to an increase in the mechanical stability of the power transmission system. The wound circuit board is preferably electrically insulated from the core halves or the ferrite core by a material such as a polyimide foil (so-called "Capton" foil (R)) or an insulating paint. The wound circuit board (with optional insulating layer) can be manufactured in a conventional circuit board mass production process.

The wound circuit board may be manufactured from any commercially available circuit board base material, such as FR4 or its high temperature variants. Commercially available circuit board base materials have high mechanical strength and are therefore ideally suited for use in power transmission systems. Due to the possibility of the wound circuit board being able to be produced cost-effectively in a large-scale process, and the high mechanical and thermal stability of commercially available standard circuit board base materials, these requirements can ideally be associated with a high strength of the resolver for contactless power transmission while at the same time being able to be produced cost-effectively.

In systems of known design, the diodes of the rectifier (see fig. 5) are either embodied as individual components (for example diodes, each having its own housing) or as combined (integrated) components (all four diodes of the rectifier being located in a housing) or in a mixed form (for example two diodes each being located in a housing). Both variants (in particular integrated design) lead to a high local temperature rise of the diode. Thus, the power of the total assembly is generally limited at high ambient temperatures. In the type of construction described herein, the diodes of the rectifier REC, called individual diodes (see fig. 5 to 8), are combined from a plurality of individual low-power diodes (and appropriate resistors). This principle is illustrated in fig. 8. In order to achieve a uniform current distribution over the circuit branches (fig. 8, circuit branch 45a), these circuit branches can either consist of only one diode 45b with a power which is less than the required total power or can consist of a series circuit of a diode 45b and a resistor 45 c. If a diode with a negative temperature coefficient (the conduction voltage of the diode decreases with increasing temperature) is selected as a component for 45b, 45c is necessary in order to prevent one of the diodes 45b from being overloaded during uneven heating of the individual branches. If, on the other hand, a diode with a positive temperature coefficient (the on-voltage of the diode increases with increasing temperature, for example a silicon carbide schottky diode) is used for 45b, 45c can be omitted. The principle shown in fig. 8 for the bridge rectifier REC can also be applied in the same way (fig. 6 and 7).

The current-carrying capacity of the windings is increased by the parallel connection of the conductor strips or conductor paths. A substantial improvement over the prior art is achieved by a special construction which allows a plurality of conductor strips to be connected in parallel in order to achieve a high current carrying capacity, while being insensitive to current suppression effects caused by alternating magnetic fields entering the conductor surface perpendicularly, i.e. in the axial direction 28 in fig. 1. This is a substantial difference with respect to the prior art of known transformers; the extension of the parallel connection of the conductor paths and/or the entire winding layer proposed in the prior art only increases the current-carrying capacity of the transformer to a limited extent. The reason for this is that the expansion of the conductor path constituting the winding results in an increase in eddy current losses due to the alternating magnetic field entering perpendicularly (that is to say in the axial direction 28 in fig. 1) into the conductor path. The parallel arrangement of the layers in contrast increases the eddy current losses caused by the alternating magnetic field entering the conductor path horizontally (that is to say in the radial direction in fig. 1). In order to counteract these two effects, assemblies have been developed which distribute the individual conductor strips on the layers of the circuit board in such a way that the conductor strips

1. By the radial and axial symmetrical distribution, the current suppression effect is counteracted when the parallel connection is carried out,

2. can be arranged rotationally symmetrically about the axis of rotation 19 in order to achieve a high area utilization.

This makes it possible to connect conductor strips in parallel (preferably outside the winding circuit board of the rotary transducer of the power transmission system, that is to say on the rectifier-rectifier circuit board 43 in fig. 1) without causing additional eddy current losses (as is the case in the methods known from the prior art) caused by the radially incoming alternating magnetic field. The design of the rotating transmitter allows the width of the conductor path to be selected such that the axially incoming alternating magnetic field generates only a small eddy current loss and the current-carrying capacity of the winding to be increased to any desired value in the following manner: any number of conductor strips wound around the circuit board (preferably on the outside, for example on the rectifier circuit board in fig. 1) can be connected in parallel without increasing the eddy current losses by entering the alternating magnetic field radially. This configuration can be realized with through contacts in the simplest embodiment (only through contact processes are completed; hidden ("Blind-Vias") and Buried ("Buried-Vias") through contacts are not necessary) and thus production time and costs are significantly reduced. By controlling the primary side PRIM of the power transfer system by means of the inverter (fig. 5 to 7), a voltage U' is induced in the secondary side SEC of the power transfer system. This voltage is rectified by a rectifier REC and smoothed by means of a capacitor 44 (fig. 5 to 7). The energization of the windings can also be performed without the capacitor 44.

The excitation winding 18 is the load to be fed by it. The conductor plate winding for high current loads can be realized in the following manner: on each copper layer of the multilayer conductor plate, individual spiral elements 50 are realized, which are connected to other spiral elements 50 of the same type on other layers by through-contacts (so-called "Vias" (Vias)). The spiral elements connected in series by vias constitute individual conductor strips (so-called "strands") which themselves have formed simple windings or spiral coils, but have only a limited current-carrying capacity. If the spiral elements are arranged in a suitable manner, a number of (mutually unconnected) spiral elements 50 (fig. 4) can be arranged on each copper layer. The spiral elements run alternately from the inside to the outside on different layers; if the spiral section extends from the outside inwards, for example on layer L1, it extends from the inside outwards on layer L2. The spiral elements located on the same layer have the same direction of extension. To reduce the current suppression effect (due to the axially entering alternating magnetic field), it is necessary that there is no electrical connection between the spiral elements on the individual layers of the wound circuit board; the electrical connection of the strands or spiral coils into a winding with high current-carrying capacity can be carried out first at the start and/or end of the strands, preferably outside the winding circuit board. The construction of the windings is illustrated in one example: on a circular wound circuit board with four copper layers, a winding with five (middle leg or coil center or axis of rotation) turns consisting of five strands or spiral coils is realized. The strands are of identical construction and are arranged only angularly offset about the z-axis (corresponding to the axial direction of the paper in fig. 3 and 4). To achieve five turns on four layers, a spiral element must include 5/4 ═ 1.25 turns on one layer. Fig. 3 shows a single (first) spiral element on the uppermost L1 of the winding circuit board (comprising 1.25 turns), furthermore shows an identically formed, angularly offset (second) spiral element on the first inner L2 of the winding circuit board, furthermore shows a (identically formed, angularly offset) third spiral element on the second inner L3 of the winding circuit board, and furthermore shows a (identically formed, angularly offset) fourth spiral element on the lowermost L4 of the winding circuit board. Advantageously, each spiral section can start/end with a tab of length P1/P2 when a through-contact with the next layer has to be realized with a wider diameter than the conductor path of the spiral section (e.g. in order to realize a sufficient current carrying capacity of the through-contact). Point a (fig. 3) is fixed as the starting point of the strand, and point H (fig. 3) is fixed as the ending point. If the points B & C, D & E and F & G, respectively, are now electrically connected to each other during the through-contact process, the strand/conductor strip is completely electrical. The points a and H have to be connected externally to the rectifier REC. The individual strands have limited current carrying capacity. In order to set the predetermined current-carrying capacity, a plurality of strands is now arranged angularly offset about the z-axis or axis of rotation (plane of the paper in fig. 4), which is illustrated in fig. 4 for the uppermost layer L1 of the wound circuit board. Points a 1-a 5 are the starting points of strands a 1-a 5. The terminal points of the strands a 1-a 5 are located (similar to that in fig. 4) on the lowermost layer L4 of the wound circuit board. All the starting and end points of the strands, respectively, are preferably connected to one another at the commutator. This results in a parallel connection of a plurality of (preferably a plurality of) wire strands which is required for increasing the current carrying capacity of the winding. If the starting and end points of the wound circuit board are connected to the commutator with through pins (e.g. pins 46 in fig. 1), it is advantageous to increase/decrease the number of turns per spiral section (e.g. from 1.25 to 1.3) such that an angular offset is created between the starting and end points and therefore points a and H (fig. 3) do not exactly overlap each other in the paper plane. When winding the layout of the circuit board, the width Q of the spiral section can be selected (fig. 4) such that as high a current-carrying capacity as possible is produced with acceptable eddy current losses (caused by axially entering alternating magnetic fields). The width Q can be determined by analytical calculations using methods known from the specialist literature or by FEM simulations (FEM-finite element method).

Due to the symmetrical arrangement of the starting and end points, only a minimal voltage difference is generally generated between the spiral sections of one layer, so that the minimum achievable value in the circuit-fabric manufacturing process is generally sufficient for the (insulating) distance between the strands (fig. 4), for example in order to meet the DIN standard with respect to the basis of the electrical gap and the creepage distance. In other cases, the value of M specified in the standard must be used. The length of the webs P1& P2 is to be selected such that the insulation distances O1& O2 between the spiral sections and between the through-contacts correspond to the basic standards (e.g. standards relating to electrical clearance and creepage distances). It is to be noted here that the voltage difference between the through contact and the wire strand can become significantly higher than in the same plane of the circuit board in the wire strand section. The use of tabs (P1 or P2) enables the manufacture of a wound circuit board with only a single through-contact process. Thereby significantly reducing costs.

In order to ensure the rotational speed stability of the rotating part of the power transmission system (secondary winding of the rotary transformer and rectifier and smoothing capacitor), it is completely cast with a casting material (e.g. epoxy resin) or overmolded with plastic. The alternating current can be rectified and smoothed in a secondary-side rectifier circuit board. For example, the rectifier circuit board is formed as a circular part having, for example, 25 capacitors and 36 diodes. Alternatively, instead of diodes, actively rectifying components can also be used. Such as a controlled MOSFET. The electronic components required for the function can be formed by connecting a plurality of individual components (preferably of the same type). As separate components, the

elements

45a and 45c indicated in fig. 8 are combined in a branch 45a (preferably consisting of a diode with a positive temperature coefficient, for example a schottky diode based on silicon carbide) to form a diode element 45.

In order to better dissipate heat from the electronic components of the rectifier circuit board, it is proposed that the rectifier circuit board is directly connected to the heat sink. A circuit board winding for achieving a high current-carrying capacity of the wound circuit board, which consists of individual conductor strips or spiral coils connected in parallel, is characterized in that the parallel connection of a plurality of conductor strips only achieves a minimization of the increase in eddy current losses caused by the alternating magnetic field entering radially in the winding window of the rotating transmitter.

In operation, all components, in particular the secondary side, electronic components of the power transmission system, have very high thermal requirements due to the current flow. Heat dissipation of electrical components is often a problem in closed (cast) systems, as shown in fig. 1 and 2. Special heat dissipation of the component is suggested by the following "heat path": the components are then conveyed via the cooling body of the power transmission system and a special highly thermally conductive epoxy resin or a special highly thermally conductive plastic onto the cover of the winding head and then into the engine compartment of the electric machine, in which the rotor rotates 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' and transfers heat from the electronic components to the cover. On the primary side, the heat path extends from the wound circuit board via the ferrite core and the cooling body into the motor housing or end shield.

The electronic components of the rectifier circuit board on the secondary side of the power transmission system have the highest thermal requirements. A rectifier circuit board 43 with an aluminum or copper core is preferably provided in order to cool the electronic components, which core is particularly efficiently thermally connected to the covering of the winding head.

As illustrated in fig. 1 and 2, heat is transferred from the rectifier circuit board to the heat sink via a direct connection. As illustrated in fig. 1 and 2, for example, a plurality of metal bolts may be used to bolt the rectifier circuit board and the cooling body. By milling, for example, at the edge of the rectifier circuit board, a direct thermally conductive contact of the rectifier circuit board to the heat sink is established. Generally, such circuit boards have a core made of aluminum or copper and a double-sided coating for the copper paths, on which the electronic parts are soldered.

There is an insulating layer between the copper core and the double-sided coating for the copper path. For the direct contact between the cooling body of the power transmission system and the aluminum core or copper core of the rectifier circuit board, the insulation layer and the copper coating for the copper path are exposed by milling, for example by a milling process. Other joining techniques (e.g., caulking or riveting) may be employed. Of course, the copper or aluminum core of the rectifier circuit board may be manufactured from other materials that conduct heat well. If the rectifier circuit board has no thermally high requirements and does not allow a copper or aluminum core, circuit board standard procedures can be used in this case. For example using a rectifier circuit board formed of standard FR4 material.

The cooling body of the power transmission system is made of, for example, aluminum or copper, in order to achieve a better heat dissipation. Other materials that conduct heat well may also be used for manufacturing the cooling body of the power transfer system. In order to be able to mechanically connect all parts of the power transmission system, it is proposed to use an epoxy or plastic with a high thermal conductivity value for the casting process or the overmolding process.

By using a special cooling body and special epoxy or plastic of the power transfer system, a special heat dissipation system of the secondary side SEC of the power transfer system is created, which heat dissipation system can reliably carry heat away from the power transfer system. If the power transmission system is embodied as a separate component, it is proposed that the power transmission system be cast or overmolded without a rotor with a special epoxy or plastic with a high thermal conductivity value. As illustrated in fig. 1 and 3, all cavities of the power transfer system are filled. The potting compound or the overmold formed by injection molding not only imparts the required rotational speed stability to the power transmission system, but also ensures reliable heat dissipation from the electronic components of the power transmission system via the cooling body to the cover of the winding head. The rotor is mechanically stabilized together with the power transmission system using a cast part of epoxy resin or using an overmoulded part of plastic in order to achieve the necessary rotational speed stability.

In general, a fixed mounting in the end shield or in the housing part of the primary-side PRIM of the power transmission system does not require high forces during operation. In contrast, all electronic components of the secondary side SEC of the power transfer system must be fixed, for example, against high centrifugal forces. In order to be able to ensure rotational speed stability, all rotor parts in externally excited synchronous machines are generally cast with epoxy resin or plastic. The design shown in fig. 1 enables all rotor parts and all components of the power transmission system to be cast in one casting or injection molding process with epoxy resin or over-molded with plastic.

In addition, based on the drawings of the above embodiments, a preferred embodiment is as follows:

a contactless power transmission system 21 for generating an electric current in an excitation winding of a rotor of an electric machine, for generating an electric current in an excitation winding 18 of a rotor 17 of an electric machine 12, wherein a primary side winding 22 is provided for arrangement at an engine housing or at an end shield 24 of the electric machine 12 and for generating an alternating magnetic field, and a secondary side winding 23 is provided for arrangement at an end side of the rotor 17 and for converting the alternating magnetic field into an alternating voltage U ', and wherein a rectifier circuit board 43 is provided which is connected to the secondary side winding 23, which rectifier circuit board has a rectifier circuit REC for providing a direct voltage U which is generated from an alternating voltage U' between two connection contacts 47 for the excitation winding 18, and wherein the secondary side winding 23 is formed on the basis of a conductor path 49 of a wound circuit board 41, the secondary winding 23 includes a plurality of parallel-connected spiral coils a1, a2, A3, a4, a5, and each of these spiral coils a1, a2, A3, a4, a5 is constituted by a plurality of spiral elements 50, and further the wound circuit board 41 is designed in a multi-layered manner, and a plurality of the spiral elements 50 are arranged offset by an angular offset 51 with respect to each other in each of the layers L1, L2, L3, L4 of the wound circuit board 41, and correspondingly one of the spiral elements 50 of each layer L1, L2, L3, L4 belongs to one of the spiral coils a1, a2, A3, a4, a5, and for each of these spiral coils a1, a2, A3, a4, a5, the respective spiral elements 50 of all its layers L1, L2, L3, L4 are connected in series by means of the through-contacts 52 of the wound circuit board 41. Preferably, wherein for dissipating heat of the power transmission system 21, the rectifier circuit board 43 is directly connected with a cooling body 42, and the secondary side ferrite core 39 of the power transmission system 21 is in contact with the cooling body 42, and the cooling body 42 is adapted to conduct heat from the rectifier circuit board 43 and the ferrite core 39 to a coupling face 42' of the cooling body 42, by means of which coupling face the cooling body 42 can be fixed at the carrier member 31 of the rotor 17. Preferably, the rectifier circuit board 43, the heat sink 42, the winding circuit board 41 and the ferrite core 39 are cast with an artificial resin 32' or overmolded with a plastic for rotational speed stability of more than 15000 revolutions per minute and/or for thermal conduction. Preferably, the rectifier circuit board 43 has a metal core for heat conduction and the heat sink is in direct contact with the metal core. Preferably, the rectifier circuit REC has a plurality of individual components 45b of the same electronic type on the rectifier circuit board 43, which are connected in parallel in a circuit branch 45 a. Preferably, resistive components 45c are connected in each case in the respective circuit branch 45a upstream of at least some of these individual components 45b in order to set the current distribution. Preferably, the spiral coils a1, a2, A3, a4, a5 in the region of the winding circuit board 41 are electrically insulated relative to one another, and the parallel circuit of the spiral coils a1, a2, A3, a4, a5 is arranged outside the winding circuit board 41, in particular on the rectifier circuit board 43. Preferably, wherein in each layer L1, L2, L3, L4 the potentials of the spiral elements 50 of the respective layer L1, L2, L3, L4 are identical, and further the spiral coils a1, a2, A3, a4, a5 are connected at the respective coil start to a common first input of the rectifier circuit REC and at the respective coil end to a common second input of the rectifier circuit REC. Preferably, wherein each of the spiral coils a1, a2, A3, a4, a5 provides U turns and the winding circuit board 41 provides N layers, and each spiral element 50 has U/N turns. Preferably, wherein each of the connection contacts 47 is designed as a hook, the wires 33 of the excitation winding 18 can be wound on the hook, wherein each hook is fastened directly at the rectifier circuit board 43. Preferably, the spiral elements 50 of the secondary side winding 23 are arranged on the winding circuit board 41 in a rotationally symmetrical manner with a respective angular offset 51. Preferably, wherein the through-contacts 52 pass completely through all layers L1, L2, L3, L4 of the wound circuit board 41. Preferably, the primary winding 22 also has a winding circuit board 37 of the type described. In addition, an electric machine 12 is shown, which is designed as an externally excited synchronous machine and contains the previously described power transmission system 21. In addition, a motor vehicle 10 is shown, which comprises said electric machine 12, wherein the electric machine 12 is designed as a traction drive 11 for the motor vehicle 10 and is connected with an inverter 13, which is adapted to a rotational speed of the electric machine 12 of more than 15000 revolutions per minute.

Overall, this example shows how a contactless current transmission for externally excited synchronous machines of a traction drive with high engine speed can be provided by the invention.

List of reference numerals

10 Motor vehicle

11 traction drive

12 electric machine

13 inverter

14 traction battery

15 stator winding

16 stator

17 rotor

18 excitation winding

19 axis of rotation

20 shaft

21 rotation transmitter

22 primary side coil assembly

23 secondary side coil assembly

24 engine housing or end shield

25 spring element

26 bearing

27 safety ring

28 axial direction

29 plate group

30 (of the excitation winding 18) winding heads

31 winding head covering member

32-pour part

32' casting

33 wire

33' casting or overmolding

34 cooling body

35 connecting circuit board

36 metal pin

37 winding the primary side winding of the circuit board

38 ferrite core

39 ferrite core

40 radial air gap

40' axial air gap

41 secondary side winding of winding circuit board

42 cooling body

43 rectifier circuit board

44 capacitor

45 diode

45a circuit branch

45b individual diode

45c resistance element

46 metal pin

47 hook

48 bolt

49 conductor path

50 helical element

51 offset angle

52 penetration contact part

53H bridge

53' capacitor

53' freewheel diode

54 intermediate tapping point

PRIM Primary side

REC rectifier circuit

SEC Secondary side

Claims

1. A power transmission system (21) for generating an electric current in an excitation winding of a rotor of an electric machine, for generating an electric current in an excitation winding (18) of a rotor (17) of an electric machine (12), wherein a primary side winding (22) is provided for arrangement at an engine housing or at an end shield (24) of the electric machine (12) and for generating an alternating magnetic field, and a secondary side winding (23) is provided for arrangement at an end side of the rotor (17) and for converting the alternating magnetic field into an alternating voltage (U '), and wherein a rectifier circuit board (43) connected to the secondary side winding (23) is provided, which rectifier circuit board has a rectifier circuit (REC) for providing a direct voltage (U) which is generated from the alternating voltage (U') between two connection contacts (47) for the excitation winding (18), and wherein the secondary-side winding (23) is formed on the basis of a conductor path (49) of a wound circuit board (41), characterized in that the secondary-side winding (23) is provided with a plurality of parallel-connected spiral coils (A1, A2, A3, A4, A5), and each of the spiral coils (A1, A2, A3, A4, A5) is composed of a plurality of spiral elements (50), and in addition the wound circuit board (41) is designed in a multilayer manner, and in each layer (L1, L2, L3, L4) of the wound circuit board (41) the plurality of spiral elements (50) are arranged offset angularly (51) with respect to one another, respectively, and correspondingly one of the spiral elements (50) of each layer (L1, L2, L3, L4) belongs to one of the spiral coils (A1, A2, A6862, A3, A828653, and for one of the spiral coils (A1, A828653), a2, A3, a4, a5), the respective spiral elements (50) of all its layers (L1, L2, L3, L4) are connected in series by means of a through contact (52) of the wound circuit board (41).

2. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the rectifier circuit board (43) is directly connected to a cooling body (42) for dissipating heat of the power transmission system (21), and a secondary-side ferrite core (39) of the power transmission system (21) is in contact with the cooling body (42), and the cooling body (42) is adapted to conduct heat from the rectifier circuit board (43) and the ferrite core (39) to a coupling face (42') of the cooling body (42), by means of which coupling face the cooling body (42) can be fixed at a carrier member (31) of the rotor (17).

3. A power transfer system (21) for generating electric current in excitation windings of a rotor of an electric machine according to claim 2, characterized by: wherein the rectifier circuit board (43), the cooling body (42), the winding circuit board (41) and the ferrite core (39) are cast with an artificial resin (32') or overmolded with a plastic for rotational speed stability of more than 15000 revolutions per minute and/or for heat conduction.

4. A power transmission system (21) for generating electric current in the excitation winding of the rotor of an electric machine according to one of claims 2 or 3, characterized in that: wherein the rectifier circuit board (43) has a metal core for heat conduction and the heat sink is in direct contact with the metal core.

5. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the rectifier circuit (REC) has a plurality of electronic individual components (45b) of the same type on the rectifier circuit board (43), which are connected in parallel in a circuit branch (45 a).

6. Power transmission system (21) for generating an electric current in an excitation winding of a rotor of an electric machine according to claim 5, characterized in that: wherein resistive construction elements (45c) are connected in each case in the respective circuit branch (45a) upstream of at least some of the individual construction elements (45b) in order to regulate the current distribution.

7. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the spiral coils (A1, A2, A3, A4, A5) in the region of the winding circuit board (41) are electrically insulated relative to one another, and the parallel circuit of the spiral coils (A1, A2, A3, A4, A5) is arranged outside the winding circuit board (41), in particular on the rectifier circuit board (43).

8. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein in each layer (L1, L2, L3, L4) the potentials of the spiral elements (50) of the respective layer (L1, L2, L3, L4) are identical, and further the spiral coils (a1, a2, A3, a4, a5) are connected at the respective coil start to a common first input of the rectifier circuit (REC) and at the respective coil end to a common second input of the rectifier circuit (REC).

9. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein each of the spiral coils (a1, a2, A3, a4, a5) provides U turns and the winding circuit board (41) provides N layers, and each spiral element (50) has U/N turns.

10. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein each of the connection contacts (47) is designed as a hook, on which the wire (33) of the excitation winding (18) can be wound, wherein each hook is fastened directly to the rectifier circuit board (43).

11. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the spiral elements (50) of the secondary-side winding (23) are arranged rotationally symmetrically with a respective angular offset (51) on the winding circuit board (41).

12. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the through-contacts (52) pass completely through all layers (L1, L2, L3, L4) of the winding circuit board (41).

13. A power transfer system (21) for generating electric current in an excitation winding of a rotor of an electric machine according to claim 1, characterized by: wherein the primary winding (22) also has a winding circuit board (37) of the type described.

14. An electric machine (12) characterized by: the electrical machine is designed as an externally excited synchronous machine and has a power transmission system (21) according to one of the preceding claims for generating an electrical current in the excitation winding of the rotor of the electrical machine.

15. A motor vehicle (10) characterized by: having an electric machine (12) according to claim 14, wherein the electric machine (12) is designed as a traction drive (11) for the motor vehicle (10) and is connected with an inverter (13) which is adapted to a rotational speed of the electric machine (12) of more than 15000 revolutions per minute.