Electrical machine and method for operating an electrical machine

Abstract

The invention relates to an electrical machine (1) with a stator (2) and a rotor (3) mounted so as to be rotatable about an axis of rotation (4) with respect to the stator (2), wherein the rotor (3) has a coolant channel (16) for the flow of a coolant and a rotor winding (8) for generating a rotor magnetic field, which is connected to an alternating current source via a rectifier device (9) arranged on the rotor (3). It is provided that the rectifier device (9) is arranged in a heat-transferring manner on a rotor body (12) of the rotor (3), which receives the coolant channel (16), so that the rectifier device (9) is thermally connected to the coolant channel (16) via the rotor body (12). The invention further relates to a method for operating an electrical machine (1).

Description

[0001] The invention relates to an electrical machine comprising a stator and a rotor mounted for rotation relative to the stator about a rotational axis. The rotor has a coolant channel for the flow of a coolant and a rotor winding for generating a rotor magnetic field, which is connected to an alternating current source via a rectifier device arranged on the rotor. The invention further relates to a method for operating an electrical machine.

[0002] For example, the prior art document DE 10 2021 200 12017 A1 is known. This relates to a rotor group for an inductively excited synchronous machine. The rotor group comprises a hollow shaft rotatable about a rotational axis, a rotor, and a secondary circuit of an energy exchanger. The secondary circuit comprises a rectifier with a circuit board and at least one electrical component, as well as a secondary coil. The rectifier is oriented transversely to the rotational axis and is arranged in a cavity of the hollow shaft in a rotationally fixed manner.

[0003] The object of the invention is to propose an electrical machine which has advantages over known electrical machines, in particular ensuring particularly effective cooling of the rectifier device while at the same time being easy to manufacture and having a high durability.

[0004] This is achieved according to the invention with an electrical machine having the features of claim 1. It is provided that the rectifier device is arranged in a heat-transferring manner on a rotor body of the rotor which accommodates the coolant channel, so that the rectifier device is thermally connected to the coolant channel via the rotor body.

[0005] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are feasible.

[0006] The electric machine is a separately excited electric machine and can be operated either as an electric motor or as a generator. The electric machine preferably serves as the traction machine of a motor vehicle, i.e., as the drive unit of a drive device of the motor vehicle. The electric machine generally comprises a stator and a rotor mounted relative to the stator about the rotational axis. The stator has a stator winding, which is at least temporarily supplied with electric current to operate the electric machine, thereby generating a stator magnetic field.

[0007] The rotor magnetic field serves as the opposing field of the stator magnetic field. This is generated using the rotor winding, which is supplied with a direct current for this purpose. The direct current is provided for the rotor winding using the rectifier device. Due to the application of the direct current to the rotor winding, heat is generated or builds up in the rotor, which must be dissipated for reliable operation of the electric machine. For this purpose, the rotor has the coolant channel, through which the coolant flows at least temporarily to cool the rotor. For example, the coolant channel is centered with respect to the axis of rotation or has a longitudinal central axis that is arranged parallel to the axis of rotation or coincides with the axis of rotation.

[0008] In conventional electrical machines, the rectifier device is either uncooled or requires significant design effort to cool the rectifier device. In the case of an uncooled rectifier device, the rectifier device can be oversized to make it less sensitive to temperature fluctuations, and / or the current supplied to the rotor winding must be limited. However, this reduces the excitation power of the electrical machine and thus its rated power.

[0009] If a permissible temperature of the rectifier device is exceeded, this can lead to failure or even damage to the electrical machine. It is also known to arrange the rectifier device in the coolant channel so that it is directly exposed to the coolant flow. However, this is complex because the seal of the coolant channel is compromised, and the rectifier device must also be designed to withstand the coolant.

[0010] For this reason, a different approach is taken for cooling the rectifier device in the proposed electric machine. It is arranged in a heat-transfer manner on the rotor body, which also contains the coolant channel. This means that the rectifier device is arranged away from the coolant channel on the rotor body, so that it is ultimately thermally connected to the coolant channel via the rotor body. Therefore, it is neither intended to arrange the rectifier device in the coolant channel nor to simply attach the rectifier device to the rotor body.

[0011] Rather, it is located outside the coolant channel but is thermally connected to the rotor body, so that any heat generated by it is dissipated via the rotor body toward the coolant channel and ultimately to the coolant. An oil with poor electrical conductivity or insulation, such as thermal oil, is used as the coolant. The rotor body is made of a material with good thermal conductivity, in particular metal. The rotor body is particularly preferably made of steel, aluminum, or copper, or at least comprises these materials. This enables extremely efficient cooling of the rectifier device using the coolant.

[0012] The thermal connection of the rectifier device to the rotor body is achieved, for example, by the rectifier device being in close contact with the rotor body or by means of an additional heat-conducting element arranged between the rectifier device and the rotor body. Due to the improved cooling of the rectifier device compared to conventional electrical machines, the rated power of the electrical machine can be significantly increased or the rectifier device can be designed smaller.

[0013] A further development of the invention provides that the rectifier device has a printed circuit board which rests against the rotor body via a heat-conducting element. The printed circuit board forms a base body of the rectifier arrangement and carries one or more electrical components, for example semiconductor components. The printed circuit board is thermally connected to the rotor body via the heat-conducting element. For this purpose, the heat-conducting element rests on the printed circuit board on the one hand and on the rotor body on the other, in particular in each case over a large area. Preferably, an area over which the heat-conducting element rests against the printed circuit board has a surface area that is similar to the surface area over which the heat-conducting element rests against the rotor body. For example, the surface areas differ by at most 20%, at most 10%, or at most 5%.

[0014] The heat-conducting element is made of a heat-conducting material, i.e., a material with high thermal conductivity. The heat-conducting element ensures a good thermal connection between the circuit board and the rotor body, allowing the heat generated on the circuit board to be efficiently dissipated to the rotor body and thus toward the coolant channel.

[0015] A further development of the invention provides that the heat-conducting element is a thermal paste, a thermal pad, a thermal adhesive, a phase-change element, or solder of a soldered connection. These elements are highly suitable for thermally connecting the rectifier device to the rotor body. In the case of the phase-change element, which serves as a latent heat storage device, intermediate storage of the heat generated by the rectifier device is also realized. Cooling of the rectifier device is therefore initially achieved, at least in part, by means of the phase-change element itself; only after a time delay is the heat transferred from the rectifier device via the phase-change element to the rotor body and consequently to the coolant.

[0016] It can also be provided that the rectifier device is integrally connected to the rotor body, in particular by soldering or welding. This is particularly the case if the rectifier device comprises a rectifier device configured as a metal-core circuit board. In this case, the soldered connection can achieve particularly effective heat transfer between the rectifier device and the rotor body. In any case, the aforementioned elements ensure reliable cooling of the rectifier device.

[0017] A further development of the invention provides that the printed circuit board is a metal-core printed circuit board and has at least one printed circuit board layer made of metal, preferably aluminum or copper, as well as a conductor track arrangement with at least one conductor track arranged on the printed circuit board layer via an insulation layer. Configuring the printed circuit board as a metal-core printed circuit board has the advantage that the heat is evenly distributed within the printed circuit board, thus achieving a uniform temperature distribution of the rectifier device.

[0018] The metal core circuit board has the metal circuit board layer and the conductor track arrangement. The conductor track arrangement has at least one conductor track, which is electrically connected to the at least one component of the rectifier device. The conductor track arrangement or its conductor track thus establishes electrical contact with the electrical component(s) of the rectifier device.

[0019] The conductor track arrangement, its conductor track, and the at least one electrical component of the rectifier device are electrically separated from the printed circuit board layer by means of the insulation layer. The insulation layer is a dielectric layer and prevents electrical contact between the aforementioned elements and the metal printed circuit board layer. The printed circuit board layer consists of a metal with good thermal conductivity, preferably aluminum or copper. The metal-core printed circuit board can also be referred to as an IMS printed circuit board (IMS: Insulated Metallic Substrate). The use of the metal-core printed circuit board as a printed circuit board has the advantage of even heat distribution within the printed circuit board and of effective heat dissipation toward the rotor body.

[0020] A further development of the invention provides that the rectifier device is arranged on a rotor wall of the rotor body, and the rotor winding is arranged on a side of the rotor wall facing away from the rectifier device. The rotor wall thus separates the rectifier device from the rotor winding, particularly in the axial direction. For example, the rectifier device rests on the rotor wall on one side, and the rotor winding rests on the rotor wall on the other. The rotor wall can also be referred to as a rotor balancing disc. It is a component of the rotor body, which is preferably designed as a single piece to achieve good thermal conductivity.

[0021] The arrangement of the rectifier device on the rotor wall has the advantage that it is already intended and designed to dissipate heat from the rotor winding toward the coolant channel or the coolant present therein. The heat generated at the rectifier device can thus be dissipated together with the heat from the rotor winding. Furthermore, the arrangement of the rectifier device on the rotor body, in particular on the rotor wall, provides a comparatively large installation space, allowing the rectifier device to be designed for high electrical power outputs. This makes it readily possible to realize an electrical machine with a high rated power.

[0022] A further development of the invention provides that a projection extends from the rotor wall, on which a secondary winding of the rotor is arranged, which cooperates with a primary winding of the stator for inductive energy transmission, and the rectifier device is electrically connected to the secondary winding. The primary winding and the secondary winding form an energy transmission device for transmitting electrical energy from the stator to the rotor or vice versa. The primary winding is fixedly connected to the stator, and the secondary winding is fixedly connected to the rotor, so that the secondary winding, together with the rotor, is mounted so as to be rotatable about the axis of rotation relative to the primary winding and the stator.

[0023] The rectifier device is electrically connected to the secondary winding. This means that it is connected to the alternating current source via the energy transfer device, i.e., the secondary winding and the primary winding. An inverter, for example, serves as an alternating current source, which converts direct current provided by a direct current source into alternating current.

[0024] The secondary winding is arranged on the projection extending from the rotor wall. The projection preferably extends axially from the rotor wall, thus projecting beyond it in the axial direction. The projection and the rotor wall are preferably configured as a single piece and made of the same material. In any case, they jointly form the rotor body, in which the coolant channel is located. The coolant channel is preferably configured both in the rotor wall and in the projection, so that both the rectifier device and the energy transmission device can be cooled by the coolant. The previously explained advantages are achieved with the aid of the described configuration of the electric machine.

[0025] A further development of the invention provides that the rectifier device has at least one active semiconductor component. The active semiconductor component is an active electronic component configured as a semiconductor. For example, the active semiconductor component is in the form of an electronic switch, in particular a transistor, preferably a field-effect transistor, particularly preferably in the form of a metal-oxide-semiconductor field-effect transistor. For example, the rectifier device has several such active semiconductor components, which together form a rectifier, for example, a bridge rectifier or a center-point rectifier.The use of the active semiconductor component has the advantage that electrical current can be conducted not only from the AC source to the rotor winding, but also in the opposite direction, i.e., from the rotor winding to the AC source. This allows for extremely rapid reduction of the rotor magnetic field. Furthermore, the efficiency of the rectifier device can be significantly increased.

[0026] A further development of the invention provides that a main extension plane of the printed circuit board is angled relative to the rotation axis. The main extension plane of the printed circuit board is understood to be an imaginary plane extending in two directions perpendicular to each other, and in which the printed circuit board has its largest dimensions. The main extension plane is thus in the form of a longitudinal center plane of the printed circuit board, which runs centrally within the printed circuit board with respect to the material thickness of the printed circuit board.

[0027] The main extension plane is angled relative to the axis of rotation, thus forming an angle with it that is greater than 0° and less than 180°. Preferably, the angle is at least 45° and at most 135°, at least 60° and at most 120°, at least 75° and at most 105°, or approximately or exactly 90°. In particular, with the vertical arrangement of the main extension plane relative to the axis of rotation, a particularly advantageous thermal connection of the rectifier device to the rotor body, more precisely to the rotor wall, can be implemented, resulting in efficient use of installation space.

[0028] The invention further relates to a method for operating an electrical machine, in particular an electrical machine according to the embodiments in the context of this description, wherein the electrical machine has a stator and a rotor mounted rotatably about a rotational axis with respect to the stator, wherein the rotor has a coolant channel through which coolant flows at least temporarily, and a rotor winding for generating a rotor magnetic field, which is connected to an alternating current source via a rectifier device arranged on the rotor. It is provided that the rectifier device is arranged in a heat-transferring manner on a rotor body of the rotor which accommodates the coolant channel, such that the rectifier device is thermally connected to the coolant channel via the rotor body and is cooled at least temporarily by means of the coolant.

[0029] The advantages of such a procedure or such a design of the electrical machine have already been pointed out. Both the electrical machine and the method for its operation can be further developed according to the explanations in this description, so reference is made to these in this regard.

[0030] A further development of the invention provides that, by means of the rectifier device, electrical current is temporarily transferred from the alternating current source to the rotor winding and temporarily from the rotor winding to the alternating current source. By transferring the electrical current from the alternating current source to the rotor winding, the rotor magnetic field is built up and, when transferred from the rotor winding to the alternating current source, is reduced. This enables a particularly rapid adjustment of the rotor magnetic field, so that a specific operating point of the electrical machine is reached more quickly than with known electrical machines.

[0031] The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and / or shown in the figures, can be used not only in the respective combination specified, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also considered to be encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which follow from or can be derived from the explained embodiments.

[0032] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. Fig. 1 a schematic longitudinal section through an area of an electrical machine.

[0033] The Fig. Figure 1 shows a schematic longitudinal section of an electrical machine 1 having a stator 2 and a rotor 3. The rotor 3 is mounted rotatably about a rotational axis 4 relative to the stator 2. The electrical machine 1 has a power transmission device 5 with a primary winding 6 and a secondary winding 7, wherein the primary winding 6 is fixedly connected to the stator 2 and the secondary winding 7 is fixedly connected to the rotor 3. An alternating current source (not shown here) is electrically connected to a rotor winding 8 of the rotor 3 via the power transmission device 5, namely via a rectifier device 9.

[0034] The rectifier device 9 serves to convert the alternating current provided by the alternating current source into a direct current, which is applied to the rotor winding 8 at least temporarily. The rectifier device 9 has a printed circuit board 10, which is preferably designed as a metal-core printed circuit board. One or more electrical components 11 are arranged on the printed circuit board 10, which are indicated and labeled here only by way of example. The components 11 are preferably active semiconductor components and serve to convert the alternating current of the alternating current source into the direct current for the rotor winding 8.

[0035] The heat generated in the rectifier device 9 is dissipated via the rotor 3 of the electric machine, more precisely via a rotor body 12 of the electric machine. For this purpose, the printed circuit board 10 is connected to the rotor body 12 via a heat-conducting element 13 in a heat-transfer manner. The heat-conducting element 13 is present, for example, as a thermal paste, thermal pad, or the like. It can be seen that the rectifier device 9 is arranged on a rotor wall 14, on which the rotor winding 8 is also located. In particular, the rotor wall 14 is arranged between the rectifier device 9 and the rotor winding 8; thus, the aforementioned elements are located on opposite sides of the rotor wall 14.

[0036] A projection 15 extends from the rotor wall 14 in the axial direction relative to the axis of rotation 4, on which projection 15 the energy transmission device 5, in particular the secondary winding 7, is arranged. The rectifier device 9 and the energy transmission device 5 are thereby offset in the axial direction, in particular spaced from one another. A coolant channel 16 is formed in the rotor 3, through which coolant flows at least temporarily according to the arrows 17. This serves, on the one hand, to cool the rotor winding 8, and, on the other hand, the heat generated in the rectifier device 9 is also dissipated in the direction of the coolant channel 16 and, accordingly, the coolant. This is indicated by the arrows 18, which are only partially marked.

[0037] The described electric machine 1 is characterized by an excellent thermal connection of the rectifier device 9 to the rotor 3. This makes it possible to increase the rated power of the electric machine 1 and eliminate the need for a redundant design of the rectifier device 9. In particular, the described arrangement of the rectifier device 9 on the rotor wall 14 optimally utilizes the available installation space. This enables a further increase in the rated power of the electric machine 1. LIST OF REFERENCE SYMBOLS: 1 electric machine 2 Stator 3 Rotor 4 axis of rotation 5 Energy transmission device 6 Primary winding 7 Secondary winding 8 rotor winding 9 Rectifier device 10 circuit board 11 Component 12 rotor bodies 13 Heat conducting element 14 Rotor wall 15 lead 16 coolant channel 17 Arrow 18 Arrow QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 200 12017 A1

[0002]

Claims

[1] Electrical machine (1) with a stator (2) and a rotor (3) mounted so as to be rotatable about an axis of rotation (4) with respect to the stator (2), wherein the rotor (3) has a coolant channel (16) for the flow of a coolant and a rotor winding (8) for generating a rotor magnetic field, which is connected to an alternating current source via a rectifier device (9) arranged on the rotor (3), characterized by that the rectifier device (9) is arranged in a heat-transferring manner on a rotor body (12) of the rotor (3) which receives the coolant channel (16), so that the rectifier device (9) is thermally connected to the coolant channel (16) via the rotor body (12). [2] Electrical machine according to claim 1, characterized by that the rectifier device (9) has a printed circuit board (10) which rests on the rotor body (12) via a heat-conducting element (13). [3] Electrical machine according to one of the preceding claims, characterized by that the thermally conductive element (13) is a thermally conductive paste, a thermally conductive pad, a thermally conductive adhesive, a phase change element or solder of a soldered connection. [4] Electrical machine according to one of the preceding claims, characterized by that the printed circuit board (10) is a metal core printed circuit board and has at least one printed circuit board layer made of metal and a conductor track arrangement with at least one conductor track which is arranged on the printed circuit board layer via an insulation layer. [5] Electrical machine according to one of the preceding claims, characterized by that the rectifier device (9) is arranged on a rotor wall (14) of the rotor body (12) and the rotor winding (8) is arranged on a side of the rotor wall (14) facing away from the rectifier device (9). [6] Electrical machine according to one of the preceding claims, characterized bythat a projection (15) extends from the rotor wall (14), on which projection a secondary winding (7) of the rotor (3) is arranged, which cooperates with a primary winding (6) of the stator (2) for inductive energy transmission, and the rectifier device (9) is electrically connected to the secondary winding (7). [7] Electrical machine according to one of the preceding claims, characterized by that the rectifier device (9) has at least one active semiconductor component (11). [8] Electrical machine according to one of the preceding claims, characterized by that a main extension plane of the printed circuit board (10) is angled relative to the axis of rotation (4). [9] Method for operating an electrical machine (1), in particular an electrical machine (1) according to one or more of the preceding claims, wherein the electrical machine (1) has a stator (2) and a rotor (3) mounted rotatably about an axis of rotation (4) with respect to the stator (2), wherein the rotor (3) has a coolant channel (16) through which coolant flows at least temporarily, and a rotor winding (8) for generating a rotor magnetic field, which is connected to an alternating current source via a rectifier device (9) arranged on the rotor (3), characterized by that the rectifier device (8) is arranged in a heat-transferring manner on a rotor body (12) of the rotor (3) which receives the coolant channel (16), so that the rectifier device (9) is thermally connected to the coolant channel (16) via the rotor body (12) and is cooled at least temporarily by means of the coolant. [10] Method according to claim 9, characterized by that by means of the rectifier device (9) electric current is temporarily transmitted from the alternating current source to the rotor winding (8) and temporarily from the rotor winding (8) to the alternating current source.

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