Secondary device for an inductive excitation apparatus

Abstract

The invention relates to a secondary device (3) for an inductive excitation apparatus (1) for an externally excited electric machine, in particular for a motor vehicle, wherein the secondary device (3) comprises a control device (5), in particular a rectifier device, which is designed to rectify an electrical signal transmitted to the secondary device (3), and a cooling device (6) associated with the control device (5), wherein the cooling device (6) comprises a heat sink (7) which provides a receiving surface (8) for the control device (5), in particular for a circuit board (9) of the control device (5), wherein the receiving surface (8), in particular a surface normal (10) of the receiving surface (8), is directed towards the rotational axis (11) of the secondary device (3), and the receiving surface (8) extends along the rotational axis (11) of the secondary device (3).

Description

[0001] Secondary device for an inductive exciter device

[0002] The invention relates to a secondary device for an inductive excitation device for a separately excited electric machine, in particular for a motor vehicle, wherein the secondary device comprises a control device designed for rectifying an electrical signal transmitted to the secondary device, in particular a rectifier device, and a cooling device associated with the control device.

[0003] Secondary devices designed for inductive transmission in inductive excitation devices for separately excited electrical machines, particularly in applications as drive units for motor vehicles, are generally known from the prior art. Such secondary devices are known to include a control device configured to rectify the electrical signal transmitted to the secondary device via the inductive excitation device, i.e., from the primary to the secondary side, in order to subsequently supply it to the rotor windings of the electrical machine.

[0004] In the operation of such secondary equipment, it is further known that heat is generated, for example, due to electrical losses in the control unit. This generated heat must be dissipated from the electronic components of the secondary equipment to ensure continuous operation at a defined power output. In addition to cooling via convection, it is known, for example, that the control unit can be arranged on a cooling unit in such a way that the cooling unit can conduct heat into the rotor shaft in a defined manner. For example, a circuit board of the cooling unit is circular and arranged perpendicular to the axis of rotation of the secondary equipment or the rotor shaft, within the rotor shaft.

[0005] Depending on the available installation space, for example the diameter of the rotor shaft, and depending on which electronic components of the control device are to be provided, for example depending on the number of rectifier diodes, the design of a protection circuit and the like, such an arrangement is not possible or only possible with difficulty, since the diameter of the cooling device is limited, so that the diameter of the rotor shaft cannot be arbitrarily set below a minimum dimension or not arbitrary rectifier devices can be used in the control device.

[0006] The invention is based on the objective of providing an improved secondary device for an inductive excitation device for a separately excited electrical machine, in which the cooling device is improved.

[0007] The problem is solved by a secondary device having the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0008] As described, the invention relates to a secondary device for an inductive excitation device for a separately excited electric machine. Specifically, the secondary device is used or implemented as a component of an inductive excitation device of a separately excited electric machine of a motor vehicle, i.e., such a motor vehicle has a separately excited electric machine with an inductive excitation device, of which the secondary device described herein is a component.

[0009] The secondary device includes a control unit designed to rectify an electrical signal, specifically an electric current, transmitted from the primary side of the inductive exciter to the secondary side and thus to the secondary device of the inductive exciter. Specifically, the control unit therefore includes a rectifier. In addition to the rectifier, the control unit may include other electronic components or circuits, such as a protective circuit. A cooling system is assigned to the control unit to cool it and dissipate heat.Therefore, at least one electronic component of the control device, in particular all components of the rectifier device, are in thermal contact with the cooling device so that heat generated by the control device can be dissipated via the cooling device.

[0010] The invention is based on the finding that the cooling device has a heat sink which provides a receiving plane for the control device, in particular a circuit board of the control device, wherein the receiving plane, in particular a surface normal of the receiving plane, faces the axis of rotation of the secondary device and extends along the axis of rotation of the secondary device. The invention thus proposes that, in contrast to the arrangement of the circular cooling device or the circular circuit board of the control device described in relation to the prior art, an axially "lying" arrangement of the control device is realized here. In other words, the heat sink of the cooling device spans a receiving plane that extends in the axial direction. The receiving plane lies within the rotor shaft, which is designed as a hollow shaft.within the installation space, which is limited by the inner wall of the rotor shaft.

[0011] This means, in particular, that the receiving plane extends in the axial direction. The surface normal of the receiving plane, which is known to be perpendicular to the surface of the receiving plane, is specifically oriented towards the axis of rotation of the secondary device, i.e., that it runs radially. Both the heat sink and the receiving plane can therefore be designed asymmetrically, i.e., that they are not symmetrically positioned on the axis of rotation, but rather arranged off-center with respect to the axis of rotation.

[0012] The "horizontal" arrangement of the mounting plane, or the shape of the heat sink that provides such a mounting plane for the control device, allows for better utilization of the available installation space within the rotor shaft. This increases the design freedom for the rotor shaft, as it no longer requires a specific minimum diameter. The installation space already available within the rotor shaft, which is designed as a hollow shaft for housing the inductive excitation device, can therefore be utilized more effectively, resulting in a comparatively larger surface area on the heat sink that can be in thermal contact with the rotor shaft. The heat sink can preferably be made of a metal, particularly one with suitable thermal conductivity.For example, the heat sink can be made of aluminum, a material containing aluminum, in particular an aluminum alloy.

[0013] As described, the heat sink is intended to enable controlled heat dissipation from the control unit, which is located on the mounting plane. For example, a circuit board of the control unit, specifically a rectifier board, can be arranged on the mounting plane. Heat generated by the electronic components of the control unit can thus be dissipated into the heat sink via the contact surface. In one embodiment, the heat sink can have a contact section for contacting the inner wall of a rotor shaft, with the contact section being designed to conduct heat into the rotor shaft. In the assembled state, where the secondary device is located in the rotor shaft of the separately excited electric machine, the contact section is therefore in mechanical and thermal contact with the inner wall of the rotor shaft.Heat introduced into the heat sink by the control unit can therefore be transferred to the rotor shaft via the contact section. This contact section provides a large-area contact surface. The comparatively large contact area between the rotor shaft and the heat sink allows for improved heat transfer.

[0014] In a further embodiment of the secondary device, the heat sink can be configured to form a circular segment in a cross-sectional area, with an edge of the receiving plane forming the chord of the circular segment or being arranged parallel to the chord of the circular segment. The circular segment, in particular, represents a portion of the cross-section of a circular cylinder. The circular segment is defined by a circular arc with a chord. This means, in particular, that the heat sink is flat in the area of ​​the receiving plane. Viewed in cross-section, or in at least one cross-sectional area, the area of ​​the receiving plane forms a circular segment, with the receiving plane forming the chord. Consequently, the control device, for example, the circuit board of the control device, is arranged on the flat side surface of the circular segment-shaped heat sink.The side surface, defined by the circular arc, specifically follows the inner contour of the rotor shaft and forms the contact section.

[0015] This means that the heat sink has a surface area that rests against the inner wall of the rotor shaft, thus providing a comparatively large area for heat exchange between the heat sink and the rotor shaft. In this section, or rather by forming the heat sink in the shape of a circular segment, the heat sink follows the inner contour of the rotor shaft. The circular segment cross-sectional area extends over the entire axial extent of the mounting plane. The heat sink and the rotor shaft can be stepped, so that different subsections have different radii. The different subsections can be adjacent in the axial direction. In addition to the circular segment shape, further sections or extensions can be provided on the heat sink, which will be discussed later.

[0016] In addition to the basic shape of the heat sink described above, further sections or extensions can be provided on the heat sink, as described, which can be formed in addition to or attached to the circular segment-shaped cross-section. In one embodiment of the secondary device, the heat sink can have at least one circular arc-shaped cooling extension, in particular two cooling extensions, for contacting the inner wall of the rotor shaft and / or for supporting the heat sink within the rotor shaft.

[0017] The arc-shaped cooling extension can, in particular, connect to the circular segment-shaped base of the heat sink when viewed in cross-section. The cooling extension(s) thereby establish additional mechanical contact with the inner wall of the rotor shaft. This additional mechanical contact can be used, firstly, to further improve heat conduction into the rotor shaft. Secondly, or alternatively, the heat sink can be mechanically fastened or supported within the rotor shaft by such an extension. At least two cooling extensions can be provided at different axial positions, for example, axially in front of the control unit and axially behind the control unit. It is also possible for only one cooling extension to be provided at only one axial position, for example, on the axial end of the heat sink facing the secondary ferrite core.

[0018] The cooling extensions can extend continuously around the circumference of the heat sink's base body and touch each other in the circumferential direction opposite the base body. Alternatively, a gap can be provided between the cooling extensions. It is also possible to form a circular arc around the circumference of the cooling extension from one end of the base body to the other.

[0019] In a further development of the secondary device, it may be provided that the heat sink has at least one support device, in particular one connected to the heat sink, which is designed to support the heat sink at its free end within the rotor shaft. The "free end" of the heat sink is understood to be, in particular, the end of the heat sink with which the heat sink is inserted axially into the rotor shaft. The free end of the heat sink is thus opposite the secondary ferrite core, for example, with respect to the control device. The support device of the secondary device supports the heat sink at this free end within the rotor shaft.

[0020] This improves the structure of the heat sink, especially at higher speeds. Specifically, it prevents the heat sink from deforming or detaching from the inner wall of the rotor shaft. The support structure can be L-shaped in section or longitudinal section, or T-shaped in cross-section. The support structure can be detachably or permanently connected to the heat sink, for example, by bolting, welding, or being integrally manufactured with the heat sink. The support structure can also contribute to heat conduction, for example, if it is made of a suitable material, particularly a metal. Alternatively, the support structure can be solely for the mechanical support of the heat sink. In this case, the support structure can also be made of a plastic, for example.

[0021] In a further embodiment of the secondary device, the heat sink can be provided with at least one fluid guidance structure, in particular an oil groove, on an outer surface, especially the surface facing the inner wall of the rotor shaft. As described, the heat sink can specifically follow the inner contour of the rotor shaft. This means that the heat sink provides a surface, particularly in a circular segment-shaped configuration. The heat sink therefore forms part of a cylindrical base shape that is not circular but circular segment-shaped. By providing the at least one fluid guidance structure, a fluid, for example oil, can be guided along the heat sink in a defined manner. For example, the heat sink can have several oil grooves through which oil can be guided along the outer surface of the heat sink.Specifically, the heat sink can have the fluid guidance structure on its outer surface. This allows the fluid guidance structure to be formed between the outer surface of the heat sink and the inner wall of the rotor shaft, so that, particularly in the axial direction, oil can be guided in a defined manner between the heat sink and the rotor shaft.

[0022] The secondary device can further comprise an intermediate element in the axial direction between a secondary ferrite core and the heat sink, which is designed to seal an interior space of the rotor shaft from an exterior space. Essentially, the intermediate element is an element in the axial direction between the secondary ferrite core and the described heat sink. In particular, the intermediate element can mechanically couple the secondary ferrite core to the heat sink. Besides the mechanical arrangement of the intermediate element between the secondary ferrite core and the heat sink, the intermediate element can have further functions, which can be implemented alternatively or additionally to one another. These are described below and can be combined as desired. As already mentioned, the intermediate element optionally provides a sealing effect.The intermediate element seals the interior of the rotor shaft, preventing fluid from escaping, particularly towards the primary unit of the inductive exciter, or towards the intermediate element itself. Specifically, the intermediate element seals an oil chamber within the rotor shaft, allowing oil to be circulated within it, for example, to cool the rotor shaft and / or the heat sink. This oil cannot escape towards the primary unit because the intermediate element seals the interior.

[0023] Furthermore, the secondary device can include an intermediate element in the axial direction between the secondary ferrite core and the cooling element, configured to guide fluid, particularly oil, along at least one fluid guide in or on the intermediate element. In this embodiment, an intermediate element, or the intermediate element described above, can be combined with a fluid guide function. This allows the fluid to be guided in a controlled manner along the intermediate element, for example, on its outer surface, or through the intermediate element, for example, by means of a fluid guide within the intermediate element. For example, such a fluid guide can be provided as an alternative or supplement to a fluid guide device in the rotor shaft, on an inner circumference, or in a wall of the rotor shaft.

[0024] According to a further embodiment, the secondary device can have an intermediate element in the axial direction between a secondary ferrite core and the heat sink. An intermediate plate is arranged on this intermediate plate, and at least one contact section for contacting a terminal element of a rotor winding is arranged on the intermediate plate. In this embodiment, the previously described intermediate element, or an intermediate element, is used to support an intermediate plate. The intermediate plate provides at least one contact section, in particular two contact sections, through which the connection to the rotor winding can be established. In other words, when the secondary device is inserted into the rotor shaft, the contact section is connected to the terminal element, in particular by blind contact.This allows, in particular, the secondary device to be installed in the rotor shaft only after the rotor shaft has been otherwise completely manufactured, especially after the lamination stack has been applied and the rotor windings have been potted. This prevents the secondary device from being exposed to thermal effects that occur during the manufacturing of the rotor shaft.

[0025] The intermediate element can have the intermediate circuit board, in particular on a mounting surface arranged perpendicular to the axis of rotation. This means that the intermediate circuit board, with its surface, is also oriented perpendicular to the axis of rotation. Furthermore, a guide for connecting cables can be provided on the intermediate element or the intermediate circuit board. For example, such a connecting cable can be routed from a secondary coil through the intermediate element and to the control unit, which is arranged on the heat sink. The connecting cables can, in particular, be routed directly from the secondary coil to the control unit without an intermediate connection, i.e., they can be made directly on the circuit board of the control unit on the heat sink.

[0026] In addition to the secondary device, the invention relates to an inductive excitation device comprising a previously described secondary device. Furthermore, the invention relates to an electric machine comprising such an inductive excitation device and / or a previously described secondary device. Finally, the invention relates to a motor vehicle comprising a previously described electric machine and / or an inductive excitation device and / or a previously described secondary device.

[0027] All the advantages, details and features described in relation to the secondary device are fully transferable to the inductive excitation device, the electric machine and the motor vehicle.

[0028] The invention is explained below with reference to exemplary embodiments and the figures. The figures are schematic representations and show: Fig. 1 a schematic representation of an inductive excitation device for a separately excited electrical machine in sectional view;

[0029] Fig. 2 shows a perspective view of a separately excited electrical machine;

[0030] Fig. 3 shows a detail of an inductive excitation device;

[0031] Fig. 4 shows a detail of a secondary device of an inductive excitation device;

[0032] Fig. 5 shows a section of a secondary device of an inductive excitation device in axial view; and

[0033] Fig. 6 shows a detail of a secondary device of an inductive excitation device.

[0034] Fig. 1 schematically shows an inductive excitation device 1 for a separately excited electric machine (not shown in detail), in particular a drive unit of a motor vehicle. The inductive excitation device 1 has a primary device 2 and a secondary device 3. The secondary device 3 is inserted into a rotor shaft 4 of the electric machine, as shown, for example, in Fig. 2.

[0035] The secondary device 3 includes a control device 5 configured to rectify electrical signals received by or transmitted to the secondary device 3 from the primary device 2. In particular, an electric current can be inductively transmitted from the primary device 2, specifically a primary coil of the primary device 2, to the secondary device 3, specifically a secondary coil of the secondary device 3. The electric current is then rectified by means of the control device 5, specifically a rectifier device.

[0036] Heat generated during the operation of the control unit 5, for example by the operation of rectifier diodes, is dissipated by means of a cooling device 6 of the secondary unit 3 or the inductive excitation device 1, in particular into the rotor shaft 4. The cooling device 6 has a heat sink 7 for this purpose, which provides a mounting surface 8 for the control unit 5. In particular, a circuit board 9 of the control unit 5 can be arranged on the mounting surface 8 and thus on the heat sink 7.

[0037] The recording plane 8, specifically a surface normal 10 of the recording plane 8, faces the axis of rotation 11 of the secondary device 3, with the recording plane 8 extending along the axis of rotation 11 of the secondary device 3. This means that the recording plane 8, and thus the circuit board 9 of the control device 5, is not perpendicular to the axis of rotation 11, but is arranged "lying" within the rotor shaft 4, extending axially. As a result, the available installation space within the hollow rotor shaft 4 can be utilized more effectively, and, particularly compared to circuit boards perpendicular to the axis of rotation 11, the diameter or inner diameter of the rotor shaft 4 is not, or not a strongly limiting factor, for the area available for the electronic components of the control device 5.

[0038] As shown, for example, in Fig. 2, 5, the heat sink 7 has a contact section 12 which, in the assembled state of the secondary device 3 shown in Fig. 2, is in mechanical and thermal contact with an inner wall.

[0039] 13 of the rotor shaft 4. In other words, the contact section 12 enables direct heat conduction from the heat sink 7 to the rotor shaft 4. The heat sink 7 forms at least one cross-sectional section in which, as shown in Fig. 5, the heat sink 7 forms a circular segment. The circular segment thus forms a fraction of a circular cylindrical body. The circular segment is defined by a circular arc 14 and a circular chord 15. The circular arc is clearly defined by

[0040] 14 the section of the heat sink 7 formed by the contact section 12 and thus bearing against the inner wall 13. In other words, the heat sink 7 follows the inner contour of the rotor shaft 4. The circular chord 15 is formed by the receiving plane 8, or rather, an edge of the circuit board 9 of the control device 5 extends parallel to the circular chord 15. As shown, the heat sink 7 and the rotor shaft 4 can be stepped, i.e., they can have different diameters in at least two different axial regions.

[0041] As can be seen in Fig. 5, the heat sink 7 in the illustrated embodiment has two cooling extensions 16, 17, which are arranged on the circular segment of the heat sink 7, for example, attached to the mounting surface 8. The cooling extensions 16, 17 form, so to speak, fingers or circular arcs that also bear against the inner wall 13 of the rotor shaft 4. This further improves heat conduction. Furthermore, the cooling extensions 16, 17 support and position the heat sink 7 circumferentially within the rotor shaft 4. An optional interruption 18 is shown by way of example, through which the heat sink 7 is interrupted circumferentially, i.e., the cooling extensions 16, 17 are spaced apart from each other circumferentially by the interruption 18.

[0042] The cooling extensions 16, 17 are further shown in the section in Fig. 6. By way of example, these extend along an axial position of the cooling element 7, which faces a secondary ferrite core 25 of the secondary device 3. By positioning the cooling extensions 16, 17 on the inner circumference of the rotor shaft 4, the stability of the cooling element 7 is improved, or rather, it is positioned over a large circumferential area within the rotor shaft 4.

[0043] Figures 1, 2, and 4 further show a support device 19, which is arranged at a free end 20 of the heat sink 7. The free end 20 is understood to be, in particular, the end of the heat sink 7 in the axial direction that engages furthest into the rotor shaft 4 or that faces away from the secondary ferrite core 25 or the primary device 2. The support device 19 supports the heat sink 7 at a free end 20 relative to the rotor shaft 4, so that no deformation of the heat sink 7 occurs even under rotational speed.

[0044] The support device 19 can be formed as a single unit with the cooling element 7 or constitute a separate component that is connected to the cooling element 7, for example by screws, welding, or the like. In this case, the support device 19 can provide an additional heat path from the cooling element 7 to the rotor shaft 4. Alternatively, the support device 19 can serve solely to support the cooling element 7 and, for example, be made of plastic. The support device 19 can be L-shaped in longitudinal section, as shown, for example, in Figures 1 and 4, and T-shaped in perspective, as shown in Figure 2.This allows, in particular, the support device 19 to free up areas when the secondary device 3 is inserted into the rotor shaft 4, where the secondary device 3 can be guided past connection elements 21 that establish contact with the rotor winding.

[0045] These connection elements 21 engage with contact sections 22 of the secondary device 3. The contact sections 22 are mounted on an intermediate plate 23, which is arranged on an intermediate element 24 that is axially positioned between the secondary ferrite core 25 and the heat sink 7. Ultimately, this allows the secondary device 3 to be inserted axially into the already completed rotor shaft 4. In other words, the laminated core and the rotor winding are already fully manufactured before the secondary device 3 can be inserted into the rotor shaft 4. The contact sections 22 enable, in particular, a blind connection with the connection elements 21, which engage as "contact blades" in the interior of the rotor shaft 4.

[0046] Figures 2 and 5 further show a fluid guidance structure 26 that the cooling element 7 has. For example, the fluid guidance structure 26 is designed as a plurality of oil grooves. The fluid guidance structure 26 is formed in an outer surface of the cooling element 7 that faces the inner wall 13 of the rotor shaft 4. In other words, the fluid guidance structure 26 is formed as a plurality of oil grooves in the outer surface of the cooling element 7, which has a circular segment in cross-section.

[0047] Furthermore, the previously described intermediate element 24 can also be configured for fluid guidance. Firstly, the intermediate element 24 can seal the interior of the rotor shaft 4, for example by means of a sealing device 27. Secondly, the intermediate element 24 can guide fluid, in particular oil, in the axial direction between the rotor shaft 4 and the intermediate element 14. It is also possible that the intermediate element 24 has at least one fluid guide within itself, with which the fluid, for example oil, can be guided in the radial direction.

[0048] The advantages, details, and features shown in the individual embodiments can be combined, interchanged, and transferred to one another as desired. As described, the secondary device 3 shown can be a component of an electric machine, as illustrated, for example, in Fig. 2. The electric machine, in turn, can be a component of a motor vehicle or a drive system for a motor vehicle.

[0049] Reference sign inductive excitation device

[0050] Primary facility

[0051] Secondary facility

[0052] Rotor shaft

[0053] Control unit

[0054] Cooling device

[0055] heat sink

[0056] Recording level

[0057] circuit board

[0058] Surface normal

[0059] axis of rotation

[0060] Contact section

[0061] Interior wall

[0062] circular arc

[0063] Circular chord, 17 Cooling process

[0064] Interruption

[0065] Support device free end

[0066] Connection element

[0067] Contact section

[0068] Intermediate board

[0069] Intermediate element

[0070] Secondary ferrite core

[0071] Fluid guidance structure

[0072] Sealing device

Claims

Patent claims 1. Secondary device (3) for an inductive excitation device (1) for a separately excited electrical machine, in particular for a motor vehicle, wherein the secondary device (3) comprises a control device (5) designed for rectifying an electrical signal transmitted to the secondary device (3), in particular a rectifier device, and a cooling device (6) associated with the control device (5), characterized in that the cooling device (6) comprises a heat sink (7) which provides a receiving plane (8) for the control device (5), in particular a circuit board (9) of the control device (5), wherein the receiving plane (8), in particular a surface normal (10) of the receiving plane (8), is directed towards the axis of rotation (11) of the secondary device (3) and the receiving plane (8) extends along the axis of rotation (11) of the secondary device (3).

2. Secondary device (3) according to claim 1 , characterized in that the heat sink (7) has a contact section (12) for contacting an inner wall (13) of a rotor shaft (4), wherein the contact section (12) is designed for heat conduction into the rotor shaft (4).

3. Secondary device (3) according to claim 1 or 2, characterized in that the heat sink (7) forms a circular segment in a cross-sectional section, wherein an edge of the receiving plane (8) forms the chord (15) of the circular segment or is arranged parallel to the chord (15) of the circular segment.

4. Secondary device (3) according to one of the preceding claims, characterized in that the cooling element (7) has at least one, in particular two, arc-shaped cooling extensions (16, 17) for contacting the inner wall of the rotor shaft (4) and / or for supporting the cooling element (7) within the rotor shaft (4).

5. Secondary device (3) according to one of the preceding claims, characterized in that the heat sink (7) has at least one, in particular with has a support device (19) connected to the cooling element (7), which is designed to support the cooling element (7) at its free end (20) in the rotor shaft (4).

6. Secondary device (3) according to one of the preceding claims, characterized in that the cooling element (7) has at least one fluid guidance structure (26), in particular an oil groove, on an outer surface, in particular the outer surface facing the inner wall (13) of the rotor shaft (4).

7. Secondary device (3) according to one of the preceding claims, characterized in that the secondary device (3) has an intermediate element (24) in the axial direction between a secondary ferrite core (25) and the cooling sink (7), which is designed to seal an interior of the rotor shaft (4) against an exterior space.

8. Secondary device (3) according to one of the preceding claims, characterized in that the secondary device (3) has an intermediate element (24) in the axial direction between a secondary ferrite core (25) and the cooling element (7), which is designed to guide fluid, in particular oil, along at least one fluid guide in or on the intermediate element (24).

9. Secondary device (3) according to one of the preceding claims, characterized in that the secondary device (3) has an intermediate element (24) in the axial direction between a secondary ferrite core (25) and the heat sink (7), on which an intermediate board (23) is arranged, on which at least one contact section (22) provided for contacting a terminal element (21) of a rotor winding is arranged.

10. Inductive excitation device (1) comprising a secondary device (3) according to any of the preceding claims.

11. Electrical machine comprising an inductive excitation device (1) according to the preceding claim and / or a secondary device (3) according to any one of claims 1 to 9.

12. Motor vehicle comprising an electric machine according to the preceding claim and / or an inductive excitation device (1) according to claim 10 and / or a secondary device (3) according to any one of claims 1 to 9.

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