Electrical rotating transformers for inductive energy transmission

Abstract

The present invention relates to an electric rotary transformer (1) for inductive energy transmission. The rotary transformer (1) comprises a rotary transformer-stator (3) with a primary coil (2) and is configured to be rotatable about a rotation axis (D) extending along an axial direction (A) relative to the rotary transformer-stator (3), and comprises a rotary transformer-rotor (6) with a secondary coil (5), which is inductively connectable or connected to the primary coil (2). The rotary transformer (1) further comprises a transformer core (4) made of a magnetic material, which is stationary relative to the primary coil (2) and at least partially surrounds the primary coil (2) and the secondary coil (5). The primary coil (2) has a primary coil winding (7) which can be energized, and the secondary coil (5) has a secondary coil winding (8) which can be energized. Furthermore, the primary coil winding (7) and the secondary coil winding (8) are arranged side by side along the axial direction (A) or side by side perpendicular to the axial direction (A), and each includes one conductive Litz wire (9, 10) or at least one conductive winding wire.

Description

[Technical field]

[0001] The present invention relates to an electrical rotary transformer for inductive energy transmission.

[0002] So-called externally excited electric synchronous machines require a direct current in their rotor to generate a rotor magnetic field. This process is called "rotor excitation". In conventional synchronous machines, the electric rotor current is transferred as an electric direct voltage to the rotating rotor by means of so-called carbon brush slip ring contacts. A disadvantage of this is that, precisely at high rotational speeds, the carbon brushes are ground down due to wear, which generates undesirable conductive carbon dust.

[0003] As an alternative to such electrical direct current transmission using slip rings, it is also known to realize the current transmission to the rotating rotor inductively, i.e. wirelessly, such a construction is part of an externally excited synchronous machine and is also called a "rotary transformer".

[0004] The functional principle of the above-mentioned inductive voltage or energy transfer is based on an electric transformer, whose primary winding or coil is arranged stationary and whose secondary winding or coil is arranged on a rotating rotor. During inductive energy transfer, an electric alternating voltage is always first generated in the secondary coil, which must then be converted into a voltage directed in the same direction.

[0005] The object of the present invention is to show a new approach in the development of rotary transformers. In particular, an improved embodiment should be provided for a rotary transformer which is distinguished by its simple construction and yet allows the rotation of the rotary transformer rotor at high rotational speeds (this property is also known to those skilled in the art under the name "high rotational speed resistance").

[0006] The above-mentioned problem is solved by the subject matter of the independent claims. Preferred embodiments are set forth in the respective dependent patent claims.

[0007] The basic idea of ​​the invention is therefore to provide both the primary coil on the stator side of the rotary transformer and the secondary coil on the rotor side, which is rotatable relative to the primary coil about its axis of rotation, with coil windings made of electrically conductive Litz wire or electrically conductive winding wire. Such coil windings are capable of carrying high currents and thus allowing a high power transmission from the stator to the rotor, which rotates relative to the stator about its axis of rotation. Furthermore, by forming the primary coil as well as the secondary coil as coil windings, respectively, it is possible to arrange these two coils directly adjacent to each other in the axial direction, in the direction of the axis of rotation, or in the radial direction, i.e. perpendicular to the axis of rotation. As a result, a particularly good magnetic and therefore inductive coupling of these two coils is achieved, which has an advantageous effect on the efficiency of the power transmission. The magnetic coupling between the primary coil and the secondary coil is furthermore induced according to the invention by a transformer core which is arranged stationary relative to the primary coil and which at least partially surrounds both the primary coil and the secondary coil.

[0008] In particular, the electric rotary transformer according to the invention comprises a rotary transformer stator with a primary coil. The rotary transformer further comprises a rotary transformer rotor with a secondary coil, which is configured to be rotatable relative to the rotary transformer stator about an axis of rotation extending along an axial direction. The secondary coil is inductively coupleable or coupled to the primary coil for energy transfer from the primary coil to the secondary coil. The primary coil comprises a primary coil winding which can be energized. The secondary coil comprises a secondary coil winding which can be energized. The secondary coil is inductively coupleable or coupled to the primary coil. This means that when an alternating current is applied to the primary coil, an alternating voltage is induced in the secondary coil. The primary coil winding and the secondary coil winding are arranged side by side along the axial direction or arranged side by side perpendicular to the axial direction in the rotary transformer according to the invention. In a second alternative, the secondary coil is preferably arranged radially inwardly and the primary coil is therefore arranged radially outwardly relative to the axis of rotation. This facilitates a non-rotatable attachment of the secondary coil to the rotary transformer rotor shaft, which is rotatable about the axis of rotation. The primary coil winding and the secondary coil winding in the rotary transformer according to the invention each have an electrically conductive Litz wire or each comprise an electrically conductive winding wire. In particular, the primary coil winding or the secondary coil winding may be formed by varnished wire, twisted wire and the like. Finally, the rotary transformer includes a transformer core made of a magnetic material, which is arranged in a fixed position relative to the primary coil and at least partially surrounds the primary coil and the secondary coil. Preferably, the transformer core is arranged coaxially relative to the axis of rotation.

[0009] In a preferred embodiment of the rotary transformer according to the invention, the primary and secondary coil windings each make a turn, preferably multiple turns, about the axis of rotation.

[0010] Reasonably, the material of the transformer core may be ferrite. Such soft magnetic materials have been found to be particularly suitable for influencing the magnetic field that occurs between the two coils during the operation of the rotary transformer. Since the transformer core is arranged stationary relative to the primary coil, i.e. does not follow the rotary movement of the secondary coil, there is also no risk of damage to the mechanically fragile ferrite due to the centrifugal forces acting during the rotary movement.

[0011] In a preferred embodiment, the primary and / or secondary coil windings are arranged on an annular primary or secondary coil winding support that rotates around the axis of rotation. Particularly preferably, the transformer core also has an annular geometry and has a central longitudinal axis that extends coaxially with the axis of rotation. In particular, the primary or secondary coil winding support may be arranged as an annular support plate and may preferably include a support plate that is arranged concentrically with the axis of rotation. The use of an annular geometry prevents undesirable imbalances during the rotational movement of the rotary transformer rotor with the secondary coil. Alternatively, the primary or secondary coil windings may be arranged on a hollow cylindrical or cylindrical primary or secondary coil winding support that extends axially and rotates around the axis of rotation in the circumferential direction. This alternative configuration facilitates assembly.

[0012] According to an advantageous development of the rotary transformer according to the invention, the transformer core, as viewed in a longitudinal section along the axial direction, has two core elements positioned axially opposite one another as well as a radially inner core element and a radially outer core element, which together at least partially surround the core inner chamber.

[0013] Particularly preferably, the primary coil and the secondary coil are arranged opposite each other in the axial or radial direction in the core chamber. The two variants ensure an effective magnetic coupling between the two coils, i.e. the primary coil and the secondary coil, which increases the efficiency of the electrical energy transmission from the primary coil to the secondary coil. Furthermore, the first variant requires particularly little construction space in the radial direction, whereas the second variant requires particularly little construction space in the axial direction. Thus, the optimum variant can be selected with respect to the available construction space, without this resulting in losses in the magnetic coupling between the two coils.

[0014] According to another advantageous development, a through hole is formed in the core element radially inside the transformer core, and the secondary coil, in particular the mounting section of the coil body, passes through this through hole radially inwardly towards the axis of rotation for mounting the secondary coil on the rotor shaft of the synchronous machine. In this development, the secondary coil can be easily and non-rotatably mounted on the rotatable rotor shaft arranged outside the transformer core, without losses occurring when the transformer core acts on the magnetic field generated by the coil.

[0015] In another preferred embodiment, the rotary transformer rotor, in particular the secondary coil, may be formed without a transformer core, in particular ferrite-free. In this way, it is possible to operate the rotary transformer even at high speeds of the rotary transformer rotor of the rotary transformer without risking damage to the rotating transformer core. Furthermore, experimental investigations have shown that by omitting the transformer core acting as a heat storage body in the rotary transformer rotor, the waste heat generated during operation can be better removed from the rotary transformer rotor.

[0016] According to an advantageous development, the rotary transformer has a rotary transformer rotor shaft which is arranged coaxially with respect to the axis of rotation and which is rotatable with respect to the transformer core and the primary coil, which is connected to the secondary coil in a non-rotatable manner. In this way, the rotary transformer can be easily attached to an electric synchronous machine, in particular by connecting the rotary transformer rotor shaft to the rotor shaft of the synchronous machine in a non-rotatable manner. Particularly preferably, the rotor shaft of the synchronous machine can also be used as the rotary transformer rotor shaft.

[0017] According to another advantageous further development, the secondary coil is electrically connected to an electrical rectifier circuit of the rotary transformer rotor, which is arranged on a printed circuit board, and which comprises at least one rectifier element, preferably two or four rectifier elements, for rectifying an alternating voltage electrically induced in the secondary coil. This measure assists in the electrical rectification of the alternating voltage induced in the secondary coil, so that this alternating voltage is a rectified voltage suitable for generating a rotor magnetic field as required in the rotary transformer rotor of an externally excited electrical synchronous machine. Rectifier diodes or rectifier transistors, in particular MOSFETs, can be used as rectifier elements. The printed circuit board can be connected to the rotary transformer rotor shaft of the rotary transformer in a non-rotatable manner. Furthermore, the printed circuit board can be arranged axially adjacent to the secondary coil or to a winding support of the secondary coil.

[0018] Preferably, the rectifier circuit is arranged radially inside on the printed circuit board. This can also apply to other electric / electronic components of the rotor electronics connected downstream of the rectifier circuit. In this way, the moment of inertia caused by the rectifier elements or the rotor electronics during rotation of the rotary transformer rotor shaft and thus the printed circuit board is kept small, which further improves the speed tolerance of the rotary transformer. The term "radially inside" in this context means that the rectifier elements or the rotor electronics, respectively, are arranged at least closer to the inner periphery of the printed circuit board than to the outer periphery of the printed circuit board, as viewed in the axial plan view of the printed circuit board. Reasonably, all or part of the electronic components, in particular all or part of the rotor electronics, can be arranged in the rotary transformer rotor shaft or, alternatively, can be transferred to an additional separate rotor printed circuit board.

[0019] Advantageously, at least one rectifier element is arranged on the top side and / or on the bottom side opposite the top side of the printed circuit board. This particularly advantageously applies to all rectifier elements that are provided. Such measures facilitate the assembly of the rotating transformer rotor.

[0020] According to an advantageous development, the printed circuit board is arranged on a support structure which can be attached to the rotary transformer rotor shaft. Particularly preferably, the support structure can be configured as a support plate. Such a support structure allows a stable and non-rotatable attachment of the printed circuit board to the rotary transformer rotor shaft and at the same time facilitates the assembly of the rotary transformer rotor shaft and the printed circuit board to the rotary transformer rotor of the rotary transformer in a suitable configuration.

[0021] The invention also relates to an externally excited electric synchronous machine, in particular a traction motor for a vehicle. The synchronous machine according to the invention comprises an energizable synchronous machine stator for generating a stator magnetic field. Furthermore, the rotary transformer comprises an energizable synchronous machine rotor for generating a rotor magnetic field, which has a synchronous machine rotor shaft and is rotatable relative to the synchronous machine stator. Furthermore, the synchronous machine according to the invention comprises an electric rotary transformer according to the invention, which is coupled to the synchronous machine rotor shaft in such a way that it cannot rotate relative to it. The above-mentioned advantages of the rotary transformer according to the invention are therefore transferred to the synchronous machine according to the invention.

[0022] The synchronous machine according to the invention can be used in particular in a motor vehicle, which may comprise a battery as an energy source. In this case, the synchronous machine is in particular used for driving the motor vehicle, i.e. is in particular configured as a traction motor. Preferably, the traction motor according to the invention has a power or drive output of at least 3 kW, preferably at least 30 kW. Particularly preferably, the traction motor according to the invention has a power or drive output of 30 kW to 500 kW, most preferably 100 kW to 300 kW. In the traction motor according to the invention, the waste heat, which is generated in the traction motor according to the invention to a much higher extent than in the case of electric motors with lower power, can be particularly effectively removed via the transformer core provided in the rotary transformer stator.

[0023] Further important features and advantages of the invention emerge from the dependent claims, the drawings and the corresponding description based on the drawings.

[0024] It will be understood that each of the features described above and below can be used not only in the combinations presented, but also in other combinations or alone, without departing from the scope of the invention.

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention are illustrated in the drawings and will be described in detail in the following description, where like reference numbers refer to the same or similar or functionally identical elements. [Brief description of the drawings]

[0026] [Figure 1] FIG. 2 is a schematic diagram showing an example of a rotary transformer according to the present invention, in which the primary and secondary coils of the transformer are arranged side-by-side in the axial direction. [Diagram 2] 2 is a schematic diagram showing a variation of the example of FIG. 1 in which the primary and secondary coils are arranged radially side by side. [Diagram 3] 2 is a schematic diagram showing a variation of the example of FIG. 1 in which the primary coil / winding support or the secondary coil / winding support has a hollow cylindrical geometry. [Figure 4] 3 is a schematic diagram showing a variation of the example of FIG. 2 in which the primary coil / winding support or the secondary coil / winding support has a hollow cylindrical geometry.

[0027] 1 shows an example of a rotary transformer 1 according to the present invention in a longitudinal cross section. The rotary transformer 1 includes a rotary transformer-stator 3 having a primary coil 2. The rotary transformer 1 further includes a rotary transformer-rotor 6 having a secondary coil 5, which is formed to be rotatable about a rotation axis D extending along an axial direction A relative to the rotary transformer-stator 3.

[0028] Here, the axis of rotation D extends along the axial direction A. The radial directions R extend perpendicular to the axial direction A and away from the axis of rotation D. In FIG. 1, a longitudinal cross-section of a rotary transformer 1 along the axial direction A is shown. The circumferential direction U is perpendicular to both the axial direction A and the radial direction R and orbits around the axis of rotation D.

[0029] The secondary coil 5 can be or is inductively coupled to the primary coil 2 for energy transfer from the primary coil 2 to the secondary coil 5. The primary coil 2 includes a current-carrying primary coil winding 7. The secondary coil 5 includes a current-carrying secondary coil winding 8. The primary coil winding 7 and the secondary coil winding 8 are arranged side by side along an axial direction A. The primary coil winding 7 and the secondary coil winding 8 are each formed by an electrically conductive Litz wire 9, 10. Alternatively to each Litz wire 9, 10, an electrically conductive winding wire can also be provided.

[0030] Furthermore, the rotary transformer 1 comprises a transformer core 4 made of a magnetic material that at least partially surrounds the primary coil 2 and the secondary coil 5. The material of the transformer core 4 may be ferrite. The primary coil winding 7 is arranged on an annular primary coil winding support 20 that rotates in a circumferential direction U around the axis of rotation D. Correspondingly, the secondary coil winding 8 is arranged on an annular secondary coil winding support 17 that rotates in a circumferential direction U around the axis of rotation D. The transformer core 4 also has an annular geometry in this exemplary scenario and has a longitudinal center axis M that is arranged coaxially with respect to the axis of rotation D. The primary coil winding support 20 or the secondary coil winding support 17 may be formed as an annular support plate that is arranged concentrically with respect to the axis of rotation.

[0031] 1, the rotary transformer 1 also has a rotary transformer rotor shaft 18 arranged coaxially with respect to the axis of rotation D and rotatable with respect to the transformer core 4 and the primary coil 2, which is non-rotatably connected to the secondary coil 5. In the illustrated longitudinal section, the transformer core 4 has two core elements 12a, 12b located axially opposite one another along the axis A, as well as a radially inner core element 13a and a radially outer core element 13b. Together, the core elements 13a, 13b at least partially surround the core chamber 14.

[0032] As can be seen from Fig. 1, the primary coil 2 and the secondary coil 5 are located axially opposite each other in the core inner chamber 14. A through hole 15 is formed in the radially inner core element 13a of the transformer core 4, through which a mounting section 16 of a secondary coil winding support 17 of the secondary coil 5 passes radially inwardly towards the axis of rotation D in order to mount the secondary coil non-rotatably on the synchronous machine rotor shaft.

[0033] The secondary coil 5 may be electrically connected to an electrical rectifier circuit 19 (also only roughly illustrated in FIG. 1) arranged on the printed circuit board 11 (illustrated diagrammatically in FIG. 1) and which comprises a number of rectifier elements (not shown) for rectification of the alternating voltage electrically induced in the secondary coil 5. The electrical connections required for this between the rectifier circuit 19 and the secondary coil 5 have been omitted in FIG. 1 for the sake of clarity.

[0034] The printed circuit board 11 may be arranged axially adjacent to the secondary coil 5 or to a secondary coil winding support 17 of the secondary coil 5, as shown in Figure 1. The printed circuit board 11 is coupled to or attached to a rotary transformer rotor shaft 18 of the rotary transformer in a non-rotatable manner relative thereto.

[0035] Figure 2 shows a variant of the example of Figure 1. The rotary transformer 1 according to Figure 2 differs from the rotary transformer 1 of Figure 1 in that in the latter the primary coil 2 and the secondary coil 5 are located radially (i.e. not axially as in the example of Figure 1) opposite each other in the core inner space 14. In both the examples of Figures 1 and 2, the secondary coil 5 of the rotary transformer rotor 6 is designed without a transformer core, i.e. without magnetic material and thus in particular free of ferrite.

[0036] 3 and 4 are diagrams corresponding to those of 1 and 2. In contrast to the example of fig. 3, the primary coil / winding support 20 or the secondary coil / winding support 17 here does not extend radially, as in the examples of fig. 1 and 2, so as to form in particular annular support plates, but extends both along the circumferential direction U and along the axial direction A. That is to say, the primary coil / winding support 20 or the secondary coil / winding support 17 in the examples of fig. 3 and 4 at least partially has a hollow cylindrical or cylindrical geometry. The through-hole 15 formed in the transformer core 4 extends along the axial direction A, as does the mounting section 16 of the secondary coil / winding support 17, which penetrates through the through-hole 15.

Claims

1. An electric rotary transformer (1) for inductive energy transmission, comprising: a rotary transformer stator (3) having a primary coil (2); a rotary transformer rotor (6) configured to be rotatable about a rotation axis (D) extending along an axial direction (A) relative to the rotary transformer stator (3), the rotary transformer rotor (6) having a secondary coil (5), the secondary coil (5) being inductively connectable or connected to the primary coil (2); a transformer core (4) made of a magnetic material and fixedly disposed relative to the primary coil (2), the transformer core (4) at least partially surrounding the primary coil (2) and the secondary coil (5); The primary coil (2) has a current-carrying primary coil winding (7), the secondary coil (5) has a current-carrying secondary coil winding (8), and Equipped with The primary coil winding (7) and the secondary coil winding (8) are arranged side by side along the axial direction (A) or side by side perpendicular to the axial direction (A), and each comprises one conductive Litz wire (9, 10) or at least one conductive winding wire. An electric rotary transformer (1) for inductive energy transmission.

2. 2. A rotary transformer according to claim 1, wherein the primary coil winding (7) and the secondary coil winding (8) each make a turn around the axis of rotation (D), preferably multiple times.

3. 3. A rotary transformer according to claim 1 or 2, wherein the material of the transformer core (4) is ferrite.

4. the primary coil winding (7) and / or the secondary coil winding (8) are arranged in the circumferential direction (U) on a preferably annular primary coil / winding support (20) or secondary coil / winding support (17) that circumferentially surrounds the axis of rotation (D), or 3. The rotary transformer according to claim 1, wherein the primary coil winding (7) and / or the secondary coil winding (8) are arranged on a hollow cylindrical primary coil / winding support (20) or secondary coil / winding support (17), which extends in the axial direction (A) and wraps around the rotation axis (D) in the circumferential direction (U).

5. 3. A rotary transformer according to claim 1, wherein the transformer core (4) has a circular geometry and a longitudinal center axis (M) arranged coaxially with respect to the axis of rotation (D).

6. 3. The rotary transformer according to claim 1, wherein the transformer core (4) has, when viewed in a longitudinal cross section along the axial direction (A), two core elements (12a, 12b) positioned axially opposite each other, as well as a radially inner core element and a radially outer core element (13a, 13b), which together at least partially surround a core inner chamber (14).

7. 7. A rotary transformer according to claim 6, wherein the primary coil (2) and the secondary coil (5) are positioned opposite each other in the axial or radial direction within the core inner chamber (14).

8. 3. The rotary transformer according to claim 1, wherein a through hole (15) is formed in a radially inner core element (13a) of the transformer core (4), and a mounting section (16) of the secondary coil (5) passes through the through hole (15) radially inward toward the rotation axis (D) for mounting the secondary coil on a synchronous machine rotor shaft.

9. 3. A rotary transformer according to claim 1 or 2, wherein the rotary transformer rotor (6), in particular the secondary coil (5), is formed without a transformer core, in particular ferrite-free.

10. 3. The rotary transformer according to claim 1, wherein the rotary transformer (1) has a rotary transformer rotor shaft (18) arranged coaxially with respect to the rotation axis (D) and rotatable relative to the transformer core (4) and the primary coil (2), and the rotary transformer rotor shaft (18) is connected to the secondary coil (5) so as not to rotate relative to the secondary coil (5).

11. 3. A rotary transformer according to claim 1 or 2, wherein the secondary coil (5) is electrically connected to an electrical rectifier circuit (19) arranged on a printed circuit board (11) of the rotary transformer rotor (6), the rectifier circuit (19) comprising at least one rectifier element, preferably two or four rectifier elements, for rectifying an alternating voltage electrically induced in the secondary coil (5).

12. An externally excited electric synchronous machine, in particular a traction motor for a vehicle, comprising: an energizable synchronous machine stator that generates a stator magnetic field; a synchronous machine rotor having a synchronous machine rotor shaft, the synchronous machine rotor being energizable and rotatable relative to the synchronous machine stator for generating a rotor magnetic field; 3. An electric rotary transformer (1) according to claim 1 or 2, wherein the electric rotary transformer (1) is connected to the synchronous machine rotor shaft in a non-rotatable manner relative to the rotor shaft; An externally excited electric synchronous machine comprising:

13. 13. The synchronous machine according to claim 12, wherein the synchronous machine or the traction motor has a power or drive output of at least 3 kW, preferably at least 30 kW, particularly preferably 30 kW to 500 kW, most preferably 100 kW to 300 kW.

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