Rotary transformer for providing an excitation current for a rotor in an externally excited synchronous motor

Abstract

The invention relates to a rotary transformer (120) for providing an excitation current for a rotor (118) in an electric machine (102), in particular an externally excited synchronous motor, comprising a transformer stator and a transformer rotor, wherein the transformer stator and the transformer rotor are arranged in an interior (133, 134) of the rotor (118), wherein the transformer stator has a stator magnetic core, wherein the transformer rotor has a rotor magnetic core, wherein the stator magnetic core and / or the rotor magnetic core comprise multiple ring segments (136a-c) distributed in a circumferential direction, wherein elongated gaps (141, 143) are formed between neighbouring ring segments (136a-c), in which one or more coolant channels (142, 144) are arranged, with at least regions extending in an axial direction and for guiding a coolant. The invention also relates to a rotor (118), an electric machine (102) and an at least partially electrified vehicle (100).

Description

[0001] August 14, 2025

[0002] 1

[0003] Rotary transformer for providing an excitation current for a rotor in an externally excited synchronous motor

[0004] The present invention relates to a rotary transformer for providing an excitation current for a rotor in an externally excited synchronous motor. The present invention further relates to a rotor, an electric machine, and an at least partially electrified vehicle.

[0005] Fully electric vehicles and hybrid vehicles are well known from the state of the art. These electric vehicles are powered exclusively or partially by one or more electric motors as drive units.

[0006] Electric axle drives for purely electric vehicles and hybrid electric vehicles are well known in the art. Such drive systems generally comprise an electric motor with a stator and a rotor rotatably mounted in the stator. The stator has several stator windings, known as phase strands, each of which is supplied with a corresponding phase current during operation. The phase currents are phase-shifted from one another, such that the current flowing through the stator windings generates a rotating magnetic field. The rotor has a rotor shaft and a rotor core fixed to the rotor shaft, in which magnetically active components are mounted. The magnetic interaction between the rotor on the one hand and the rotating field on the stator side on the other generates a torque that sets the rotor in rotation.

[0007] The magnetic effect of the rotor can be provided by one or more permanent magnets. This is then called a permanent magnet synchronous motor. Alternatively, the rotor can use an electromagnet with a rotor coil, in which case it is an externally or electrically excited synchronous motor (EESM). In the case of an EESM, it is necessary to supply the rotor coil with a direct current (DC current). In the case of inductive transmission of the excitation current to the rotor, converter systems are used in the prior art to first convert a DC input voltage into a primary-side AC voltage.

[0008] 2. The latter is then converted into a secondary-side AC voltage according to the transformer principle and finally rectified into a DC output voltage adapted to the rotor. A DC excitation current is generated from the DC output voltage to energize the rotor coil and create the desired rotor magnetic field.

[0009] Specifically for voltage conversion according to the transformer principle, transformers known from the prior art are equipped with a transformer core, a primary winding, and a secondary winding, so that the primary-side AC voltage, after being fed into the primary winding, is converted into the secondary-side AC voltage, which is applied to the secondary winding, according to the winding ratio between the primary and secondary windings. A rectifier is also connected downstream of the secondary winding, which converts the secondary-side AC voltage into the desired DC output voltage.

[0010] However, existing transformer systems and devices have several disadvantages that impair the functionality of the electric drive. For example, due to their design and assembly, these systems require a comparatively large amount of installation space, making it impossible or only possible to manufacture the rotor or electric motor in a compact design to a limited extent. Furthermore, the heat generated during operation of the transformer systems due to the current flowing to integrated electronic components such as circuit breakers cannot be adequately dissipated, increasing the risk of these components overheating and impairing the functionality of the electric motor.

[0011] The object of the present invention is therefore to provide a transformer for supplying the excitation current for the rotor, with which the aforementioned disadvantages are at least partially overcome.

[0012] The aforementioned technical task is accomplished by a transformer designed as a rotary transformer, a rotor, an electric motor, and at least 14.08.2025

[0013] 3. Partially electrified vehicle according to the main claim and the dependent claims. Advantageous embodiments are the subject of the dependent claims. The advantages described in connection with the claims relating to the rotary transformer also apply to the rotor, the electric motor, and the vehicle according to the invention.

[0014] The present invention relates, in a first aspect, to a rotary transformer for providing an excitation current for a rotor in an electric motor, which is an externally excited synchronous motor. The rotor (main rotor) comprises a rotor coil which is supplied with the DC excitation current to generate a constant rotor magnetic field. The rotary transformer comprises a transformer stator and a transformer rotor. The transformer stator is preferably associated with the primary side of the rotary transformer, with the transformer rotor being associated with the secondary side of the rotary transformer. To provide the excitation current, the rotary transformer is configured to convert a primary-side AC voltage into a DC output voltage that is adapted to the desired DC excitation current. Accordingly, the primary side of the rotary transformer has a primary winding and the secondary side of the rotary transformer has a secondary winding.Based on the winding ratio between the primary and secondary windings, the primary-side AC voltage applied to the primary winding is first converted into a secondary-side AC voltage. The primary-side AC voltage is generated, for example, by an inverter comprising several semiconductor-based power switches connected in a bridge configuration and preferably located on the primary side, from a DC input voltage. The secondary-side AC voltage is then fed to a rectifier connected downstream of the secondary winding. This rectifier preferably comprises several diodes also connected in a bridge configuration and generates the DC output voltage by switching the diodes based on the secondary-side AC voltage.

[0015] The transformer stator is fixed in a stationary position relative to the stator (main stator) of the electric motor, with the transformer rotor being rotationally fixed relative to the rotor. 14.08.2025

[0016] 4. Both the transformer stator and the transformer rotor are arranged within an interior space of the rotor. Preferably, both the transformer stator and the transformer rotor are mounted inside a rotor shaft of the rotor. The transformer stator has a stator magnetic core, and the transformer rotor has a rotor magnetic core. The respective magnetic core preferably comprises an iron core (in particular a ferrite core) and a coil to provide the primary winding or the secondary winding, respectively. According to the invention, the stator magnetic core and / or the rotor magnetic core comprise several ring segments distributed in a circumferential direction defined with respect to an axis of rotation of the electric motor. This means that the stator magnetic core or the rotor magnetic core can comprise several circumferentially distributed ring segments. Alternatively, both the stator magnetic core and the rotor magnetic core can comprise several ring segments.Axially elongated gaps are formed between adjacent ring segments. These elongated gaps are used to define or accommodate at least one, and preferably several, coolant channels. The coolant channel(s) extend at least partially in an axial direction along the elongated gaps and serve to guide a coolant to cool the rotary transformer. The coolant channels are preferably arranged between adjacent ring segments of the rotor magnet core. Additionally, at least one coolant channel can run between adjacent ring segments of the stator magnet core and / or between a ring segment of the rotor magnet core and a ring segment of the stator magnet core.

[0017] In this way, a space-saving rotary transformer is realized, which, due to its preferred placement inside the rotor, especially the rotor shaft, does not require any installation space outside the rotor. This applies to both the axial and radial directions, allowing the electric motor to be manufactured in a compact form overall. Furthermore, the cooling capacity is evenly distributed along the axial extent of the coolant channels, thus improving the thermal coupling of the energized windings of the primary and / or secondary side of the rotary transformer to the coolant. Thanks to the segmentation of the stator magnet core and / or the rotor magnet core, the rotary transformer can be manufactured using the [document / design] described in [date] 14.08.2025.

[0018] 5

[0019] The coolant channels allow for particularly effective cooling of the coolant transported within the motor. Overheating of the rotary transformer or impairment of the electric motor's functionality can therefore be avoided with greater certainty.

[0020] According to one embodiment, the coolant channels are defined by a potting compound surrounding the transformer stator and / or the transformer rotor. For example, the potting compound can be applied to the ring segments using an injection molding process, with the compound defining groove-shaped spaces in the elongated gaps to form the coolant channels. This measure makes it particularly easy to implement the coolant channels, even with complex or irregular geometric shapes of the ring segments.

[0021] According to another embodiment, the coolant channels are defined by pipes inserted into the interior of the rotor. The pipes are preferably prefabricated and inserted into the interior of the rotor, particularly the rotor shaft, during the rotor manufacturing process. This measure allows the coolant channels to be implemented in a cost-effective and predefined manner.

[0022] According to a further embodiment, a cover element is arranged on an end face of the rotor, in particular the rotor shaft, wherein several openings, in particular through-openings, are formed in the cover element, which connect at least partially to the elongated gaps, preferably the coolant channels. The cover element is preferably designed as a support for the rectifier for the rotary transformer. The openings or through-openings preferably function as coolant inlets or outlets for the coolant channel system. In this way, a simplified supply and / or discharge of the coolant is provided at the end face of the rotor.

[0023] According to a further embodiment, the coolant channels have at least two different cross-sectional sizes. The cross-sectional size is characteristic of the amount of coolant that can be conveyed through the associated coolant channel. (14.08.2025)

[0024] 6

[0025] Providing several different cross-sectional sizes increases the adaptability of the entire coolant channel system to the characteristics of the rotary transformer and rotor, and the associated distribution of the heat to be dissipated, thus enabling an optimized distribution of cooling capacity. For example, the cross-sectional size of the coolant channels can scale with, and in particular increase with, the width of the elongated gap.

[0026] According to a further embodiment, at least two of the coolant channels define two different, in particular opposite, coolant flow directions. This measure can also serve to compensate for possible inconsistencies in the heat distribution in the rotor, so that the cooling capacity can be distributed flexibly.

[0027] According to a further embodiment, at least one outer ring segment of the ring segments is fixed inside a rotor core surrounding the rotor shaft, with at least one of the coolant channels running between the outer ring segment and another ring segment. In this embodiment, the ring segments are not spatially restricted within the rotor shaft. In this way, the cavity inside the rotor core can be used to accommodate the rotary transformer, which facilitates a compact rotor design.

[0028] According to a further embodiment, the coolant comprises a cooling fluid, in particular water or oil. The cooling fluid can be conveyed from a reservoir into the coolant channel system by means of a fluid pump. The fluid pump can also be used by the cooler for the electric motor and / or the gearbox. Furthermore, the electric motor and / or the gearbox can be cooled by the cooling fluid circulating in the coolant channel system of the rotary transformer.

[0029] According to another embodiment, the transformer stator is at least partially surrounded by the ring segments of the transformer rotor. Preferably, a stationary central support is provided for attaching or securing the 14.08.2025

[0030] 7

[0031] The transformer stator winding is provided, with the support, in particular designed as a dome, arranged inside the rotor or rotor shaft. The support or central dome for the transformer stator winding is stationary relative to the stator of the electric motor (or the main stator), whereas the transformer rotor is mounted so as to be rotationally fixed to the rotor or rotor shaft and thus rotates relative to the main stator.

[0032] Within the scope of the present invention, a rotor for an externally excited synchronous motor is also proposed, comprising a rotary transformer according to any of the embodiments described herein. The rotor core of the rotor can be designed as laminated sheet metal parts (sheet metal stack) made of steel.

[0033] Within the scope of the present invention, an electric machine for an at least partially electrified vehicle is further proposed, comprising a rotor according to any of the embodiments disclosed herein and a stator. The electric machine is, in particular, an externally or electrically excited synchronous motor (EESM), especially an inductively electrically excited synchronous motor (IEESM). The electric machine can function as the sole drive unit or, alternatively, as one of several drive units, for example, in the case of a hybrid electric vehicle (HEV) with a combination of an electric drive unit and an internal combustion engine. The electric machine can have a substantially cylindrical outer contour or a conical outer contour, e.g., for a brake motor.

[0034] Within the scope of the present invention, an at least partially electrified vehicle comprising the electric machine according to the invention is proposed. The at least partially electrified vehicle can be, for example, a purely electric vehicle (EV), such as a battery electric vehicle (BEV), or a hybrid electric vehicle (HEV).

[0035] The aspects mentioned above serve illustrative purposes and are not intended to limit the scope of the invention. Numerous variations of the above 14.08.2025

[0036] The eight described aspects are possible. The various aspects discussed in this disclosure can be combined in any way to produce additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

[0037] The invention is explained below with reference to examples using the embodiments shown in the figures. The figures show:

[0038] Fig. 1 shows a schematic representation of a vehicle comprising an electric axle drive with an electric motor;

[0039] Fig. 2 shows a schematic representation of a rotary transformer for providing a DC excitation current for a rotor of the electric motor, wherein the rotary transformer comprises a primary side and a secondary side;

[0040] Fig. 3 shows a schematic representation of the rotor according to one embodiment in an axial side view;

[0041] Fig. 4 shows a schematic representation of the rotor according to a further

[0042] embodiment in an axial side view;

[0043] Fig. 5 shows a schematic representation of the rotor according to a further

[0044] embodiment in an axial side view;

[0045] Fig. 6 shows a schematic representation of the rotor according to a further

[0046] embodiment in an axial side view;

[0047] Fig. 7 shows a schematic representation of the rotor according to a further

[0048] embodiment in an axial side view;

[0049] Fig. 8 shows a schematic representation of the rotor according to a further

[0050] Design shown in an axial side view; 14.08.2025

[0051] 9

[0052] Fig. 9 shows a schematic representation of the rotor according to a further

[0053] embodiment in an axial side view;

[0054] Fig. 10 shows a schematic representation of the rotor according to a further

[0055] embodiment in an axial side view;

[0056] Fig. 11 shows a schematic representation of the rotor in a perspective view according to a further embodiment.

[0057] The same objects, functional units, and comparable components are designated with the same reference numbers in the figures. These objects, functional units, and comparable components are identical with respect to their technical characteristics unless the description explicitly or implicitly discloses otherwise.

[0058] Fig. 1 shows a schematic representation of a vehicle 100 that is at least partially electrified. The vehicle 100 can be a purely electric vehicle or a hybrid vehicle. The vehicle 100 is equipped with an electric axle drive comprising an electric motor 102, a DC / AC inverter 106, and a gearbox 112. The electric motor 102 is designed here as an externally excited synchronous motor (EESM), in particular as an inductively externally excited synchronous motor (IEESM). The electric motor 102 comprises a stator (not shown in detail here, hereinafter referred to as the "main stator") with several phase strands arranged as stator windings and a rotor 118 (see, for example, Fig. 3, hereinafter referred to as the "main rotor") comprising one or more electrically conductive rotor coils (not shown in detail here).The inverter 106 is connected between the drive battery 106 and the electric motor 102 for the purpose of converting a DC input voltage provided by a traction battery 104 into an AC output voltage. For this purpose, the inverter 106 has a plurality of power switches (not shown here) forming a bridge circuit with several half-bridges and controlled by control signals generated by a control unit 108. The control signals are preferably configured to control the power switches of the inverter 106 according to a 14.08.2025.

[0059] 10

[0060] Pulse width modulation (PWM) is used for switching. In particular, several preferably sinusoidal, phase-shifted phase currents are generated for the phase strands of the main stator of the electric motor 102 by closing and opening the power switches. The phase currents, each fed into one of the several phase strands of the main stator, create a rotating magnetic field inside the main stator. The main rotor 118, or the rotor coil, is supplied with a DC excitation current, resulting in a stationary magnetic field on the main rotor 118. Based on the interaction between the rotating stator magnetic field and the stationary rotor magnetic field, a torque is generated, which is transmitted by means of the gearbox 112, which preferably has a reduced gear ratio, to an axle 110, here by way of example the rear axle of the vehicle 100, and finally to wheels 114, here by way of example rear wheels.

[0061] To generate the DC excitation current, the main rotor 118 uses a rotary transformer 120, the circuit diagram of which is shown schematically and purely by way of example in Fig. 2. The rotary transformer 120 comprises a voltage input 119, a primary side 124, and a secondary side 126. The voltage input 119, to which a capacitor Cin is connected, serves to connect a DC power supply, e.g., from the vehicle's electrical system. The primary side 124 preferably has a first converter stage 121 designed as an inverter with transistors T1-4 and gate units GU1-2, as well as a primary winding Lp coupled to the first converter stage 121. The secondary side 126 has a second converter stage 129 designed as a rectifier with diodes D1-4 and a secondary winding 131 Ls coupled to the second converter stage 129.The primary winding Lp and the secondary winding Ls form a transformer unit 128 and are galvanically isolated from each other, in particular by means of galvanic isolation, where the galvanic isolation 125 is indicated by a dashed line. As further illustrated in Fig. 2, a DC input voltage is first converted into a primary-side AC voltage by means of the first converter stage 121. The latter is then converted into a secondary-side AC voltage by means of the transformer unit 128 according to the transformer principle and finally into a secondary-side AC voltage by means of the second converter stage 129.

[0062] 11. Here, for example, a rotor resistance R r and a rotor inductance L r The main rotor 118 is rectified to a suitable DC output voltage. This DC output voltage is used to generate the desired DC excitation current for energizing the rotor coil(s) in order to provide the appropriate rotor magnetic field.

[0063] The rotary transformer 118 comprises a transformer stator and a transformer rotor. Preferably, the primary side 124 forms the transformer stator, with the secondary side 126 forming the transformer rotor. This means that the secondary side 126 is fixedly arranged with the main rotor 102 so that it rotates together with the main rotor 118 during operation of the electric motor 102, thus constituting a rotating / rotatable secondary side 126. In contrast, the primary side 124 is stationary relative to the main stator, thus constituting a stationary primary side 124. The rotary transformer 120 is preferably modular in design so that it can be axially mounted as a separate component within the electric motor 102.

[0064] As shown schematically and purely by way of example in a side view in Fig. 3, the main rotor 118 has a rotor shaft 130 defining the axis of rotation of the electric motor 102 and a rotor core 132 surrounding it. According to the invention, both the transformer stator and the transformer rotor are arranged in an interior space 134 of the main rotor 118, in particular of the rotor shaft 130, as shown in Fig. 3. This facilitates a compact design of the main rotor 118 and, consequently, of the entire electric motor 102. Furthermore, the transformer rotor has a rotor magnet core, which is designed as an arrangement of several first ring segments 136a, 136b, 136c distributed in a circumferential direction, as shown purely schematically in the side view of Fig. 3. The ring segments 136a, 136b, 136c each extend in an axial direction, with elongated gaps 141, 143 forming between adjacent ring segments 136a, 136b, 136c.According to the invention, these elongated gaps 141, 143 are used to define several coolant channels 142, 144 that extend at least partially, preferably substantially, axially. The coolant channels 142, 144 are designed to carry a coolant, in particular a cooling liquid such as water or oil, and to facilitate heat exchange between the coolant and the current-driven windings as well as the ring segments 136a, 14.08.2025.

[0065] 12

[0066] 136b, 136c to cool these during operation. In Fig. 3, the coolant channels 142, 144 are shown as dashed lines, with arrows also included to indicate a coolant flow direction. In the embodiment shown in Fig. 3, the coolant channels 142, 144 define, purely by way of example, the same coolant flow direction axially between a first end face 138 and a second end face 140 of the main rotor 118 opposite the first end face 138. Alternatively, the coolant channels 142, 144 can define two opposite coolant flow directions between the first end face 138 and the second end face 140, as shown schematically and purely by way of example in Fig. 4. Similarly, several coolant channels 142, 144 can define opposite coolant flow directions, with a connecting channel 146 provided between the coolant channels 142, 144, as shown in Fig.Figure 5 shows a further embodiment. The connecting channel 146, which in Figure 5 extends by way of example in a transverse direction perpendicular to the axial direction, represents a bend in the coolant channels 142, 144. In this way, a U-shaped coolant line with the three sections, namely the coolant channels 142, 144 and the connecting channel 146, is realized for the circulation of the coolant inside the rotor shaft 130.

[0067] In the embodiments shown in Figures 3-5 above, the coolant channels 142, 144 are shown by way of example with the same cross-sectional size or width. However, this is not limiting for the present invention. Figure 6 shows a schematic and purely exemplary representation of the main rotor 118 according to a further embodiment in a side view, in which the coolant channels 142, 144 differ in their cross-sectional size / width. In particular, the cross-sectional size / width of the coolant channels 142, 144 is adapted to the width of the elongated gaps 141, 143 defining the respective coolant channels 142, 144. Thus, the coolant channel 142 in a narrower elongated gap 141 has a smaller cross-sectional size / width compared to the coolant channel 144 in a wider elongated gap 143.

[0068] In the embodiments shown in Figs. 3-6 above, the ring segments 136a, 136b, 136c are associated with the rotor magnet core of the transformer rotor. As shown in the schematic diagram dated 14.08.2025

[0069] As shown in Figure 13 and in the purely exemplary illustration in Figure 7 in a side view, it is also conceivable to arrange at least one coolant channel, preferably several coolant channels 142, 144, in an elongated gap 141, 143 between a first ring segment 136a, 136c of the rotor magnet core and a second ring segment 137 of the stator magnet core. Although only a single second ring segment 137 of the stator magnet core is shown here, it is possible to provide several second ring segments 137, with an elongated gap formed between adjacent second ring segments 137 to define or accommodate a coolant channel. This means that the coolant channels 142, 144 can be realized between adjacent ring segments 136a-c of the rotor magnet core, between adjacent ring segments 137 of the stator magnet core or in a mixed form between a ring segment 136a-c of the rotor magnet core and a ring segment 137 of the stator magnet core.

[0070] Figures 8-9 each show a schematic and purely exemplary representation of the main rotor 118 according to a further embodiment in a side view. In each figure, a first cover element 148, which is preferably designed here as a disk-shaped, axially symmetrical support, is attached to the first end face 138 of the main rotor 118, in particular the rotor shaft 130. The end-face first cover element 148 or support is further preferably designed to accommodate the components of the second converter stage 129 (see Figure 2), which is configured as a rectifier. As can be seen purely by way of example in Figure 8, two openings 150, 152, which are preferably designed here as through-openings, are provided in the first cover element 148, each connecting to the coolant channels 142, 144. The openings or through-openings 150, 152 can serve as coolant inlet or outlet. In the representation shown in Figure 8, the first cover element 148 is designed as a disc-shaped, axially symmetrical support.In the exemplary embodiment shown in Fig. 9, a second cover element 154 is additionally shown, which is attached to the second end face 140 of the main rotor 118 or the rotor shaft 130. Openings or through-openings 156, 158 can also be formed there, as can be seen in Fig. 9, which serve as coolant inlet or outlet. In this way, the coolant can be supplied to the coolant channel system at one of the two end faces 138, 140 of the main rotor 118 and, after heat exchange with the components, in particular the current-carrying ring segments 136a-c of the rotary transformer 14.08.2025.

[0071] 14

[0072] 120, on the other end face 138, 140 of the main rotor 118 are discharged back into the environment.

[0073] Fig. 10 shows a schematic and purely exemplary representation of the main rotor 118 according to a further embodiment in a side view. In this embodiment, analogous to the embodiment shown in Fig. 9, two cover elements 148, 154 are attached to the end faces 138, 140, each having several axially oriented openings or through-openings 150, 151, 152, 153, 156, 157, 158, 159, wherein the openings or through-openings 150, 151, 152, 153, 156, 157, 158, 159 connect to the coolant channels 142, 144. Additional coolant channels 146, 148' are also provided, each located in an elongated gap.

[0074] The coolant channels 146, 148' are formed between one of the ring segments 136a, 136c arranged in the interior 134 of the rotor shaft 130 and an outer ring segment 136d, 136e arranged in the interior 133 of the rotor core 132. As Fig. 10 shows by way of example, the coolant channels 146, 148' are preferably arranged in the interior 133 of the rotor core 132. The provision of such outer coolant channels 146, 148' and / or outer ring segments 136d, 136e is not limited to the embodiment shown in Fig. 10, but is generally applicable to all conceivable embodiments. Furthermore, it is also conceivable not to provide an opening or through-opening in the second cover element 154.

[0075] The coolant channels 142, 144 shown in the embodiments shown in Fig. 3-10 above,

[0076] Figures 146 and 148' are shown as straight lines for the sake of simplicity. However, this is by no means a limitation of the present invention. At least one of the coolant channels 142, 144, 146, 148' can have at least a partial curvature, bend, and / or branch, wherein the coolant channels 142, 144, 146, 148' each run substantially axially, but at least include an axial channel component along one of the elongated gaps 141, 143, 145, 147.

[0077] The coolant channels 142, 144, 146, 148' shown in the above embodiments from Fig. 3-10 are preferably connected by a transformer stator and / or the 14.08.2025

[0078] 15

[0079] The potting compound surrounding the transformer rotor is defined. For example, the potting compound can be applied to the ring segments 136a-e, 137 using an injection molding process, whereby in the areas of the elongated gaps 141, 143, 145, 147, the potting compound defines tubular spaces for forming the coolant channels 142, 144, 146, 148'. Alternatively or additionally, the coolant channels 142, 144, 146, 148' are defined by tubes inserted into the interior 134 of the main rotor 118 or the rotor shaft 130. The tubes are, for example, prefabricated and inserted into the interior of the main rotor 118, in particular into the rotor shaft 130, during the manufacturing process. With the help of these measures, the coolant channels 142, 144, 146, 148' can be created in a cost-effective and flexible manner.

[0080] Alternatively or additionally, the transformer stator is at least partially surrounded by the ring segments 136a-e of the transformer rotor. Preferably, a stationary central support (not shown here) is provided for attaching or securing the winding of the transformer stator, wherein the support, which may in particular be designed as a mandrel, is arranged inside the main rotor 118 or the rotor shaft 130. The support or the central mandrel for the winding of the transformer stator is arranged in a stationary position relative to the main stator of the electric motor 102, whereas the transformer rotor is mounted so as to be rotationally fixed to the main rotor 118 or the rotor shaft 130 and thus rotates relative to the main stator.

[0081] Fig. 11 shows a schematic and purely exemplary embodiment of the rotor shaft 230 according to a further embodiment in a perspective view. Several first ring segments 236 of the rotor magnet core of the transformer rotor are arranged circumferentially distributed inside the rotor shaft 230. In addition, several second ring segments 237 of the stator magnet core of the transformer stator are axially surrounded by the first ring segments 236. An elongated gap is formed between adjacent first ring segments 236, in which an associated coolant channel 242, 244, designed as a tube, runs in the axial direction. Alternatively, the coolant channels 242, 244 can also extend radially inwards through the grooves between adjacent ring segments of the rotor magnet core of the transformer rotor and radially outwards through an inner surface of the rotor shaft (130) that defines the interior (134). 14.08.2025

[0082] 16 are defined. In an arrangement in which an outer circumferential surface of the rotor magnet core rests against an inner circumferential surface of the hollow rotor shaft, radially outwardly open grooves in conjunction with the inner wall of the rotor shaft can also form the coolant channels.

[0083] A first cover element 248, designed as a carrier for the electronic components of the rectifier, is mounted on the end face of the rotor shaft 230. This cover element has several axially aligned through-openings 250, 252 for connecting to the coolant channels 242, 244. A second cover element 254 is mounted axially opposite the first cover element 248 on the end face of the rotor shaft 230. A transformer input 260 for applying the DC input voltage and a transformer output 262 for outputting the DC output voltage generated by the rotary transformer 120 to provide the DC excitation current for the main rotor 118 are also attached to the second cover element 254. These components are electrically connected to the transformer stator and the transformer rotor, respectively, via leads extending from the interior of the rotor shaft 230 over the second cover element 254.In this way, a simple and space-saving contacting of the rotary transformer 120 is achieved.

[0084] A cover element 148, 154, 248, 254 offers the possibility of establishing not only electrical but also fluidic connections between two or more coolant channels (142, 144, 242, 244) within the cover element. Circumferential distribution or collector channels can be formed by channels extending essentially circumferentially. Likewise, a connection between two preferably adjacent coolant channels (142, 144, 242, 244) can also serve as a deflection without an inlet or outlet to allow coolant to flow in opposite directions through several coolant channels. 8.2025

[0085] 17

[0086] Reference symbol list: at least partially electrified vehicle, electric motor (externally excited synchronous motor), traction battery

[0087] DC / AC inverter

[0088] Control unit

[0089] rear axle

[0090] transmission

[0091] rear wheels

[0092] Rotor (main rotor)

[0093] voltage input

[0094] Rotary transformer first converter stage (inverter)

[0095] Primary page

[0096] Potential separation

[0097] Secondary page

[0098] Transformer unit, second converter stage (rectifier), 230 rotor shaft

[0099] Rotor core, 134 interior ac, 236 first ring segments de outer ring segments, 237 second ring segment first end face A first partial longitudinal slot B second partial longitudinal slot second end face, 143, 145, 147 elongated gap, 144, 146, 148', 242, 244 coolant channels, 248 first cover element (carrier) 8.2025

[0100] 18, 151, 152, 153, 156, 157, 158, 159, 250, 252 Openings (through openings), 254 Second cover element Transformer input Transformer output

Claims

August 14, 2025 19 Patent claims 1. Rotary transformer (120) for providing an excitation current for a rotor (118) in an electric machine (102), in particular an externally excited synchronous motor, comprising a transformer stator and a transformer rotor, wherein the transformer stator has a stator magnet core and the transformer rotor has a rotor magnet core, wherein the stator magnet core and / or the rotor magnet core comprise several ring segments (136a-c) distributed in a circumferential direction, wherein elongated gaps (141, 143) are formed between adjacent ring segments (136a-c) in which one or more coolant channels (142, 144) extending at least partially in an axial direction are arranged for guiding a coolant.

2. Rotary transformer (120) according to claim 1, wherein the transformer stator and the transformer rotor are arranged in an interior space (134) of a rotor shaft (130) of the rotor (118).

3. Rotary transformer (120) according to claim 1 or 2, wherein the coolant channels (142, 144) are defined by a potting compound surrounding the transformer stator and / or the transformer rotor.

4. Rotary transformer (120) according to claim 1 or 2, wherein the coolant channels (142, 144) are defined by tubes which are inserted into the interior (134) of the rotor (118).

5. Rotary transformer (120) according to claim 2, wherein the coolant channels (242, 244) are defined radially inside by grooves between adjacent ring segments (236) of the rotor magnet core of the transformer rotor and radially outside by an inner surface of the rotor shaft (130) limiting the interior (134). August 14, 2025 20 6. Rotary transformer (120) according to one of the preceding claims, wherein a cover element (148, 154) is arranged on an end face of the rotor (118), in particular the rotor shaft (130), wherein several openings (150, 151, 152, 153), in particular through-openings, are formed in the cover element (148, 154), which connect at least partially to the elongated gaps (141, 143), preferably the coolant channels (142, 144).

7. Rotary transformer (120) according to claim 6, wherein two or more cooling channels (142, 144, 242, 244) are fluidically connected to each other within the cover element (148, 154, 248, 254).

8. Rotary transformer (120) according to one of the preceding claims, wherein the coolant channels (142, 144) have at least two different cross-sectional sizes.

9. Rotary transformer (120) according to claim 8, wherein the cross-sectional size of the coolant channels (142, 144) scales with, in particular increases with, the width of the elongated gaps (141, 143).

10. Rotary transformer (120) according to one of the preceding claims, wherein at least two of the coolant channels (142, 144) define two different, in particular opposite, coolant flow directions.

11. Rotary transformer (120) according to one of the preceding claims, wherein at least one outer ring segment (136d,e) of the ring segments (136a-e) is fixed inside a rotor core (132) surrounding a rotor shaft (130), wherein at least one of the coolant channels (146, 148') runs between the at least one outer ring segment (136d,e) and another of the ring segments (136a-e).

12. Rotary transformer (120) according to one of the preceding claims, wherein the coolant comprises a cooling liquid, in particular water or oil. August 14, 2025 21 13. Rotary transformer (120) according to one of the preceding claims, wherein the transformer stator is at least partially surrounded by the ring segments (136a-c) of the transformer rotor.

14. Rotor (118) for an electric machine (102), in particular an externally excited synchronous motor, comprising a rotary transformer (120) according to any one of claims 1 to 13.

15. Electric machine (102), in particular an externally excited synchronous motor, for an at least partially electrified vehicle (100), comprising a rotary transformer (120) according to one of claims 1 to 12 or the rotor (118) according to claim 14.

16. At least partially electrified vehicle (100) comprising an electric machine (102), in particular an externally excited synchronous motor, according to claim 15.

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