Rotor arrangement for an electrically excited synchronous motor (EESM)

Abstract

Rotor arrangement (2) for an electrically excited synchronous motor (EESM), comprising: a rotor shaft (3), a rotor core (4) connected to the rotor shaft (3) with several pole sections (6, 6') distributed around the circumference, wherein windings (5, 5') are accommodated around each of the pole sections (6, 6'), wherein the windings (5, 5') have first winding ends (24) which extend axially from a first end surface (25) of the rotor core (4), and on the opposite side second winding ends (26) which extend axially from a second end surface (27) of the rotor core (4), a first fluid guidance element (7) which is arranged at a first end of the rotor core (4), a second fluid guidance element (8) which is arranged at a second end of the rotor core (4), wherein the rotor shaft (3) has an axial bore (14) and several radial bores (15) extending from it, which are arranged in an axially central region of the rotor shaft (3), wherein the rotor core (4) has several inlet openings (19) which are fluidically connected to the radial bores (15) of the rotor shaft (3) and axial channels (28, 30) which extend axially from the inlet openings (19) to first outlet openings (29) at the first end face (25) of the rotor core (4) and to second outlet openings (31) at the second end face (27) of the rotor core (4), wherein the first fluid guiding element (7) is fluidically connected to the first outlet openings (29) of the rotor core (4) and has a fluid structure (32) configured to receive cooling fluid from the first outlet openings (29) of the rotor core (4) and to direct the cooling fluid to first outlet openings (33) arranged circumferentially between two circumferentially adjacent first winding ends (24), and wherein the second fluid guiding element (8) is fluidically connected to the second outlet openings (31) of the rotor core (4) and has a fluid structure configured to receive cooling fluid from the second outlet openings (31) of the rotor core (4) and to direct the cooling fluid to second outlet openings arranged circumferentially between two circumferentially adjacent second winding ends (26), characterized by that the first fluid guidance element (7) has a first annular section (34) and several first winding support sections (35) projecting radially from the first annular section (34), wherein first head sections (36) form enlarged ends of the first winding support sections (35), wherein the first end windings (24) encompass the first winding support sections (35), and / or that the second fluid guidance element (8) has a second annular section (37) and several second winding support sections (38) projecting radially from the second annular section (37), wherein second head sections (39) form enlarged ends of the second winding support sections (38), wherein the second end windings (26) encompass the second winding support sections (38).

Description

[0001] The invention relates to a rotor arrangement for an electrically excited synchronous motor (EESM) and an EESM with such a rotor arrangement.

[0002] In an electro-electrical synchronous motor (EESM), the rotation of the shaft is synchronized with the frequency of the supply current. Specifically, the rotation period is equal to an integer number of alternating current (AC) cycles. Synchronous motors can use electromagnets as the stator to generate a magnetic field that rotates synchronously with the current frequency. The rotor can be equipped with permanent magnets or electromagnets and rotates synchronously with the stator field. This results in the rotor generating a synchronized rotating magnetic field.

[0003] From US patent 2016 / 0 211 712 A1, a rotor assembly with an end winding support element with integrated lubricant distribution is known. A segment body is provided for the end windings, which has an internal groove from which bores extend outwards. The cooling oil flows from the outer surface of the rotor shaft at the ends of the rotor in the overlap area with the segment bodies into the groove and from there into the bores to cool the windings of the rotor assembly.

[0004] From EP 3 501 085 B1, an electric machine with a cooling structure is known. The cooling structure is primarily intended to cool the rotor or rotor lamination stack. In addition, the winding ends of the stator lamination stack are also to be cooled by the cooling fluid flowing outwards from the cooling channel.

[0005] From DE 102021 111 321 A1 a rotor device for an electric machine is known, which has a rotor with rotor lamination stack and a cooling fluid line that extends parallel to the central axis of the rotor in the circumferential direction between adjacent pole legs.

[0006] From DE 10 2021 213 812 A1, which can be considered a generic prior art, a rotor for an electric machine is known, comprising a rotor shaft and a laminated core arranged on the rotor shaft with a plurality of stacked electrical steel sheets. The rotor further has a first end plate arranged on one axial side of the laminated core with radial projections arranged along its circumference and a second end plate arranged on the opposite axial side of the laminated core with radial projections arranged along its circumference. In addition, the rotor has several rotor windings as well as a central cooling channel running in the rotor shaft for supplying a coolant and a radial cooling channel.

[0007] From WO 2021 / 232835 A1, an electric motor with a rotor and a stator is known. The rotor comprises a rotating shaft, a rotor core, and a plurality of rotor windings. The rotor core is provided with a plurality of winding gaps spaced at intervals around the rotating shaft. A gap is formed between two adjacent rotor windings, and a first shaft bore is formed in the rotating shaft. The gap is configured to form a first heat dissipation channel, which is connected to the first shaft bore. The first heat dissipation channel is used for a coolant flowing into the rotating shaft. In this way, the coolant is introduced into the rotating shaft from the outside and enters the first heat dissipation channel from the first shaft bore under centrifugal force to dissipate heat from the rotor windings.

[0008] US Patent 11,011,960 B2 discloses a wound rotor motor in which a rotating shaft is arranged vertically to immerse the lower winding sections of a stator and a rotor in cooling oil. A flow channel is located in the rotating shaft through which cooling oil rises from the area below the rotor and is sprayed into the area above the rotor by the centrifugal force generated by the rotor's rotation.

[0009] From KR 10 1 967 731 B1, a wound excitation motor is known which includes a support and cooling element for a coil. The motor comprises: a rotor with a plurality of cores projecting radially from a center, field coils wound around each of the cores, and a plurality of cooling and support elements with a cooling structure for dissipating heat generated inside the rotor to the outside. The cooling and support elements are arranged such that the coil wound around the core of the rotor is firmly supported, and forced convection of air inside the rotor is generated, thereby dissipating the heat generated in the rotor to the outside in order to maximize cooling performance.

[0010] From WO 2018 095842 A1, corresponding to FR 3 059 487 A1, a wound rotor is known which has a shaft with circumferentially alternating teeth and slots, each tooth receiving a longitudinal winding that is intended to form a rotor pole. Each winding defines a projecting coil head at each longitudinal end of the rotor. The rotor includes at least one collar for the mechanical retention of the rotor windings, the collar being attached to one longitudinal end of the rotor to define a central opening towards the coil heads. The collar has at least one drain channel so that coolant flowing into the central opening can be directed onto the coil heads.

[0011] An oil-cooled motor cooling structure is known from CN 114567102 A. The motor comprises a rotor with a shaft, a plurality of rotor core assemblies, a rotor end plate, and an oil guide plate. The two axial ends of the rotor iron core are each covered by rotor end plates. The end face of the rotor end plate facing the rotor iron core is provided with a plurality of first heat dissipation oil channels extending radially outward. Several first oil spray openings are distributed annularly around the outer circumference of the rotor end plate and are connected to the radially outer ends of the first heat dissipation oil channels.

[0012] Electrically excited synchronous motors (EESMs) are becoming increasingly popular, particularly to replace medium- to high-power permanent magnet synchronous motors (PMSMs) and thus avoid the use of heavy rare earth (HRE) magnets. However, the performance of an EESM is limited by the temperature in the rotor and stator windings. Conventional EESMs with indirect cooling systems, such as water jackets or even direct air cooling, have limited heat dissipation capabilities. To meet ever-increasing power demands, more advanced and effective direct cooling systems are needed.

[0013] It is an object of the present invention to propose a rotor arrangement, in particular for an electrically excited synchronous motor (EESM), with an efficient cooling structure. Furthermore, an EESM with such a rotor arrangement is to be proposed which exhibits good cooling properties and a long service life.

[0014] According to the invention, a rotor arrangement for an electrically excited synchronous motor (EESM) is proposed, wherein the rotor arrangement comprises: a rotor shaft, a rotor core connected to the rotor shaft and having several pole sections distributed around the circumference, with windings being accommodated around each of the pole sections, the windings having first winding ends projecting axially from a first end face of the rotor core, and on the opposite side, second winding ends projecting axially from a second end face of the rotor core; a first fluid guide element arranged on the first end face of the rotor core, a second fluid guide element arranged on the second end face of the rotor core, wherein the rotor shaft has an axial bore and several radial bores extending from it, arranged in an axially central region of the rotor shaft, and wherein the rotor core has several inlet openings.which are fluidically connected to the radial bores of the rotor shaft, and axial channels extending axially from the inlet openings to first outlet openings at the first end face of the rotor core and to second outlet openings at the second end face of the rotor core, wherein the first fluid guiding element is fluidically connected to the first outlet openings of the rotor core and has a fluid structure configured to receive cooling fluid from the first openings of the rotor core and to guide the cooling fluid to first outlet openings arranged circumferentially between two circumferentially adjacent first winding ends, and wherein the second fluid guiding element is fluidically connected to the second outlet openings of the rotor core and has a fluid structure configured to receive cooling fluid from the second openings of the rotor core and to guide the cooling fluid to second outlet openings,which are arranged circumferentially between two circumferentially adjacent second winding ends, wherein the first fluid guiding element has a first annular section and several first winding support sections projecting radially from the first annular section, wherein first head sections form enlarged ends of the first winding support sections, wherein the first end windings encompass the first winding support sections, and / or that the second fluid guiding element has a second annular section and several second winding support sections projecting radially from the second annular section, wherein second head sections form enlarged ends of the second winding support sections, wherein the second end windings encompass the second winding support sections.

[0015] One advantage of the proposed rotor arrangement is the inclusion of a direct oil cooling system. This system utilizes the centrifugal force generated by the rotor's rotation to drive cooling fluid through the rotor and to the end windings. This allows the cooling fluid to be introduced into the hollow shaft at a very low pressure. Inside the shaft chamber, the cooling fluid is centrifugally distributed, creating a flow along the shaft's inner wall. The cooling fluid then exits the shaft through a series of passages or radial bores connecting the shaft chamber to channels extending through the rotor core. As the cooling fluid exits the rotor channels, it comes into contact with the fluid guide elements, which are in contact with the rotor core, particularly its end faces. These fluid guide elements direct the cooling fluid to the rotor winding ends, where it is discharged.The cooling fluid can be any fluid suitable for cooling and / or lubricating the electric machine, e.g., an oil.

[0016] A supply element can be provided to deliver coolant to the rotor shaft, extending in particular into the axial bore of the rotor shaft. This supply element can, for example, be in the form of a static lance, which may be connected to a housing or an associated support structure. Compared to a rotating lance, the oil flow within the static lance is not affected by the rotational speed of the electric machine. No centrifugal force is present in the static lance, which allows for precise control of the oil flow to the shaft.

[0017] The majority of radial bores are arranged in the central region of the rotor shaft. In particular, at least some of the majority of radial bores of the rotor shaft can be arranged in a plane that lies axially within a central region of the rotor core, for example, within a central third of the rotor core. Arranging the radial bores in a central region has the advantage that coolant can flow from there to the first and second sides of the rotor core, thereby absorbing heat from the rotor core.

[0018] The rotor core can optionally be composed of multiple lamination stacks. A central group of rotor laminations can include the radial bores. The rotor laminations arranged axially adjacent to the central group can have an identical structure. The axial channels extend through all lamination stacks to the axial ends of the rotor core, allowing coolant to exit. The number of radial bores and axial channels in the rotor core can correspond to the number of pole sections or windings in the rotor assembly. The axial channels can, for example, be arranged circumferentially in the region of the pole sections or windings. However, other numbers of channels and windings are also possible. The axial channels can be arranged radially between an inner circumferential surface of the rotor core and a radially inner end of the pole sections to accommodate the windings.In other words, the channels can be arranged radially within the pole sections of the rotor core, particularly with circumferential overlap with the pole sections. The pole sections extend radially outwards from an annular section and can also be referred to as projecting poles or web sections.

[0019] According to one embodiment, the first and second guide elements can have the same construction. Thus, the features described for one guide element (the first element) can also apply to the other guide element (the second element). A fluid guide element can have an annular channel fluidically connected to the outlet openings of the rotor core and a plurality of fluid pockets fluidically connected to the annular channel and arranged on an inner circumferential surface of the guide element. The outlet openings are each fluidically connected to one of the fluid pockets. The annular channel of the fluid guide element can be arranged with a radial overlap to the side openings of the rotor core channels. This causes the cooling fluid exiting the axial channels to collect in the annular channel of the fluid guide element, forming an annular cooling fluid pool within the annular channel.The annular pool is fluidically connected to the fluid pockets, each forming an axial reservoir to collect cooling fluid centrifugally before it is discharged to the outside via overflow.

[0020] The outlet openings of the fluid guide element can have an axial extent of at least 0.25 times, in particular at least 0.5 times, and especially at least 0.75 times, the axial length of the end windings projecting beyond the end face of the rotor core. In this way, the openings are slot-shaped, which, in conjunction with the reservoir design, contributes to an axially wide oil cascade towards the winding ends of the rotor. This allows for particularly effective cooling of the winding ends.

[0021] In one embodiment, a fluid guide element can have a first annular section and a plurality of winding support sections projecting radially from the first annular section. The winding support sections can have head sections that form enlarged ends, thus preventing the end windings from slipping off the support sections. The end windings enclose the winding support sections, i.e., they enclose and / or engage with a respective winding support section. The winding support sections can have a cross-sectional shape corresponding to the pole sections of the rotor core, i.e., they can form a lateral extension of the pole sections.The windings, which can also be called coils, each run in a closed loop around a corresponding pole section of the rotor core, the first winding support section of the first fluid guide element, and at the opposite end around the second winding support section of the second fluid guide element. In an embodiment with winding support sections, the fluid guide element fulfills two functions: cooling and supporting the end windings. Therefore, the fluid guide element can also be referred to as a cooling element and / or support element.

[0022] A fluid guide element can be made of a non-conductive material, particularly a material different from that of the rotor core. For example, a plastic material can be used for a fluid guide element. As mentioned earlier, some or all of the configurations described above can apply to the first and / or second guide element.

[0023] In one embodiment, a first end ring can be provided on the first side of the rotor core and a second end ring on the opposite second side. The first and / or second end ring can be made of a metallic material, in particular aluminum or an aluminum alloy, but this is not limited to this. The end rings can be mechanically connected to the rotor core, in particular to the rotor stacks. In one embodiment, the first and second end rings can be axially clamped against each other by a plurality of clamping or clamping elements. The clamping elements can each be arranged circumferentially between two windings. The first and / or second end ring can have a flanged section for receiving the clamping elements and a shell section that substantially encloses the end windings. Thus, the end ring has an L-shaped form when viewed in a semi-longitudinal section.Furthermore, the end ring can have a plurality of web sections extending axially along a radial inner circumference of the shell section. The clamping elements can extend axially through the web sections, each of which can be arranged between two circumferentially adjacent end coils.

[0024] In a preferred embodiment, the end ring can be shaped to collect coolant flowing from the rotor winding ends and effectively redirect the fluid to the stator winding ends through several strategically placed holes in the outer part of the ring. These holes or openings allow coolant flowing from the fluid guide elements to the winding ends to be temporarily collected in the end ring, from where it escapes radially outward through the openings and is flung against the stator by centrifugal forces before flowing back into the cooling system. The openings of the end ring can be arranged circumferentially offset from the outlet openings of the respective fluid guide element.

[0025] The rotor core comprises a plurality of longitudinally extending recesses or slots for receiving the windings, each recess being formed between two circumferentially adjacent pole sections. A wedge element can be arranged in each longitudinal recess between any two circumferentially adjacent windings. The wedges can be secured in the longitudinal recesses to prevent the rotor winding from being dislodged from the winding slot by centrifugal forces.

[0026] The problem is further solved by an electrically excited synchronous motor (EESM) comprising: a housing, a stator arranged in the housing which includes a stator core and a winding, and a rotor rotatably mounted in the housing about an axis of rotation, the rotor being designed according to one of the embodiments above. In this way, an EESM is provided which has very good cooling properties and thus a long service life.

[0027] Preferred embodiments are described below with reference to the drawings. These show Fig. 1A a rotor arrangement for an electric machine in longitudinal section; Fig. 1B the rotor arrangement from Fig. 1A in a first cross-sectional view according to the section line 1B-1B; Fig. 1C the rotor arrangement from Fig. 1A in a second cross-sectional view according to the section line 1C-1C; Fig. 2 the rotor arrangement Fig. 1A in a three-dimensional exploded view; Fig. 3A the rotor arrangement of Fig. 1A in a partially cutaway view with a coolant flow shown; Fig. 3B the rotor arrangement of Fig. 1A in a modified embodiment; Fig. 4 a detail of the rotor arrangement of Fig. 1A in a perspective view of an end section of the arrangement, partially cut away; Fig. 5A a detail of the rotor arrangement from Fig. 1A in a perspective view of a side of the fluid guidance element facing the rotor core; Fig. 5B a fluid guidance element of the rotor assembly of Fig. 1A as a detail, partially cut out; Fig. 5C a cross-section through the fluid guidance element made of Fig. 5A; Fig. 5D an axial view of the fluid guidance element Fig. 5C with a marked cooling fluid flow; Fig. 6A a first detail of a flow path F of the rotor arrangement of Fig. 1A in a perspective view, partially cropped; Fig. 6B a second detail of a flow path F of the rotor arrangement of Fig. 1A in a perspective view, partially cropped; Fig. 6C a third detail of a flow path F of the rotor arrangement of Fig. 1A in a perspective view, partially cropped; Fig. 6D a fourth detail of a flow path F of the rotor arrangement of Fig. 1A in a perspective view, partially cropped; Fig. 7A an electric motor according to the invention with a in the Fig. 1A-6D shows the rotor arrangement in a longitudinal section, and Fig. 7B shows the electric motor arrangement of Fig. 7A in a partially cropped perspective view.

[0028] The Fig. Figures 1A to 6D, which are described together below, show a rotor arrangement 2 according to the invention for an electric machine 2, in particular for an electrically excited synchronous motor (EESM).

[0029] The rotor assembly 2 comprises the following components: a rotor shaft 3, a rotor core 4 connected to the rotor shaft 3, windings 5 ​​mounted on pole sections 6 of the rotor core 4, and a fluid guide element 7, 8 at each axial end of the rotor core 4. A first end ring 9 may be provided at a first axial end 10 of the rotor core, and a second end ring 12 at the opposite second axial end 13 of the rotor core. The rotor shaft 3 comprises an axial bore 14 and a group of radial bores 15.

[0030] In the installed state of the rotor assembly, a supply element (not shown) can be provided, which can extend axially into the axial bore 14 of the rotor shaft 3. The supply element can, for example, be in the form of a static lance, which can be connected to a housing or a support part of the housing. Compared to a rotating lance, the oil flow in the static lance is not affected by the rotational speed of the electric machine. No centrifugal forces occur inside the static lance, so the oil flow to and into the shaft is easily controllable.

[0031] In the axial regions of the radial bores 15, the rotor shaft 3 can optionally have an annular recess 16 on its inner circumferential surface. The coolant flowing along the inner wall of the axial bore 14 by centrifugal forces thus easily reaches the openings of the radial bores 15, which are radially offset from the radius of the end sections of the inner shaft wall. The group of radial bores 15 is preferably arranged in a plane P, as shown in the Fig. 1A and Fig. Figure 1B shows, but is not limited to, the radial bores 15 are arranged in particular in the central region of the rotor shaft 3. More specifically, at least some of the radial bores 15 are arranged in a plane P that lies axially within a central section of the rotor core 4, in particular a central third of the rotor core, for example, exactly in the center of the rotor core.

[0032] The rotor core 4 is rigidly connected to the rotor shaft 3. An axial connection can be established by axially supporting the rotor core 4 at one end against a flange section 17 of the rotor shaft 3 and axially clamping it at the opposite end by a sleeve 18 screwed onto the rotor shaft 3. A rotationally fixed connection can be established by a frictional engagement, such as an interference fit, between the rotor shaft 3 and the rotor core 4 and / or a positive engagement, such as a splined connection. The rotor core 4 comprises a plurality of axially extending recesses 41 on a radially outer region of the rotor core, with pole sections 6, 6' each formed between two circumferentially adjacent recesses 41. The recesses 41 can also be referred to as longitudinal grooves.

[0033] Each of the pole sections 6, 6' carries a winding 5, 5' which surrounds the respective pole with a closed loop, as shown in particular in Fig. 2 can be seen. Therefore, the pole sections can also be referred to as winding carriers or protruding poles. In a cross-sectional view, as shown in the Fig. 1 B and Fig. As shown in Figure 1C, the winding support can have a T-shape, with a radial section 22 and a head section 23 that is widened circumferentially relative to it. The T-shape contributes to the secure positioning of the windings 5, 5' even at high speeds and prevents the windings from detaching from the winding support due to centrifugal forces. The windings 5, 5', which can also be referred to as coils, each have a first winding end 24 that projects axially beyond the first end face 25 of the rotor core and, on the opposite side, a second winding end 26 that projects axially beyond the second end face 27 of the rotor core 4. The winding ends 24, 25 form U-shaped inverted sections of the windings. The windings 5, 5' supported by the rotor core 4 generate a constant magnetic field. In an activated state, the rotor core 4 is rotated around the axis of rotation A to drive the rotor shaft 3 and a drive train connected thereto.

[0034] The rotor core 4 has a plurality of inlet openings 19 on a radially inner circumferential surface 20, which are fluidically connected to the radial bores 15 of the rotor shaft 3. The inlet openings 19 of the rotor core 4 are preferably aligned with the radial outlet openings of the rotor shaft 3. The inlet openings 19 can extend radially to the axial channels connected to them. In particular, first axial channels 28 extend axially from the inlet openings 19 to first outlet openings 29 at the first end face 25 of the rotor core 4, and second axial channels 30 extend to second outlet openings 31 at the second end face 27 of the rotor core.

[0035] The rotor core 4 can be composed of a multitude of lamination stacks. A central set of rotor laminations includes the inlet openings 19, as shown in the Fig. 1A and Fig. 1B can be seen. The rotor laminations, which are arranged axially next to the central laminations, preferably have the same configuration as shown in Fig. Figure 1C shows the lamination stacks forming the axially extending channels 28, 30. The axial channels 28, 30 extend through all the lamination stacks to the axial ends 25, 27 of the rotor core 4. From the central section of the rotor core 4, part of the coolant flows in the first axial direction to the first side 10 and part of the coolant flows in the opposite second axial direction to the second side 13, thereby absorbing heat from the rotor core 4.

[0036] As especially in the Fig. 1 B and Fig. As can be seen in Figure 1C, the number of radial bores 19 and axial channels 28, 30 of the rotor core 4 corresponds to the number of windings 5, 5' of the rotor assembly 2. In the present embodiment, the axial channels 28, 30 are arranged circumferentially in the region of the pole sections 6, 6' and windings 5, 5', respectively. Furthermore, the axial channels 28, 30 are arranged radially between the inner circumferential surface 20 of the rotor core and a radial inner end 21 and / or a shoulder of the pole sections 6, 6', where the windings 5, 5' are located. It is understood, however, that the number and arrangement of the radial and axial channels may also differ from the example shown here.

[0037] The first fluid guidance element 7 and the second fluid guidance element 8 are arranged, in particular, in axial contact with the end faces 25, 27 of the rotor core. The fluid guidance elements 7, 8 are preferably connected to the rotor core 4 via the first and second end rings 9, 12, the end rings being clamped to the rotor core 4. In the present embodiment, the first and the second fluid guidance elements 7, 8 have the same construction, so that the features described for one element also apply to the other. The first fluid guidance element 7 is fluidically connected to the first outlet openings 29 of the rotor core 4 and comprises a fluid structure 32 designed to receive cooling fluid and direct it to first outlet openings 33, which are arranged circumferentially between two circumferentially adjacent end windings 5, 5'.

[0038] In particular, the fluid guiding element 7, 8 comprises a ring section 34 and several winding support sections 35 that project radially from the ring section. As shown in particular in the Fig. As shown in Figures 5A to 5C, the annular section 34 comprises, at an axial end that is in contact with the adjacent end surface 25, 27 of the rotor core 4, an annular channel 48 and a plurality of fluid pockets 49, which are fluidically connected to the annular channel and arranged in an inner circumferential surface 50 of the fluid guide element 7, 8. The annular channel 48 is designed to receive coolant from the adjacent outlet openings 29 of the rotor core. For this purpose, the annular channel 48 of the fluid guide element 7, 8 is preferably arranged with a radial overlap to the lateral openings 29 of the rotor core channels. Thus, the coolant exiting the axial channels 28, 30 collects in the annular channel 48 of the respective fluid guide element 7, 8, forming an annular pool of coolant through the annular channel 48.The annular pool is fluidically connected to the fluid pockets 49, each forming an axial reservoir to collect the coolant centrifugally before it is discharged to the outside by overflowing through radial bores 51 extending through the annular section 34 of the fluid guide element 7, 8. The radial bores 51 fluidically connect the radially inner fluid pockets 49 to the radially outer outlet openings 33. The radial bores 51 and / or the outlet openings 33 have an axial extent that is, in particular, at least 0.5 times, and in particular at least 0.75 times, the axial length of the end windings 24, 26 projecting beyond the end face of the rotor core. The slot-shaped configuration thus formed, in conjunction with the reservoir configuration, contributes to an axially wide oil cascade of coolant flowing towards the winding ends 24, 26 of the rotor, as shown in [reference]. Fig. Illustrated in 5D.

[0039] The winding support sections 35 comprise head sections 36 that form enlarged ends, thus preventing the end windings 24, 26 from slipping off the support sections 35 due to centrifugal forces. In radial view, the end windings 24, 26 surround the winding support sections 35, 38 in a U-shape. In cross-sectional view, the winding support sections 35, 38 are preferably configured to correspond to the pole sections 6, 6' of the rotor core 4, i.e., to form a lateral extension of the pole sections 6, 6' at the axial ends of the rotor core. The windings 5, 5' each extend in a closed loop around the associated pole sections 6, 6' of the rotor core, the first winding support section 35 of the first fluid guidance element 7 and at the opposite end around the second winding support section 38 of the second fluid guidance element 8.The fluid guide elements contribute to good cooling and support of the end windings 24, 26. The fluid guide elements 7, 8 can be made of a non-conductive material, in particular plastic.

[0040] The first end ring 9 is attached to the first side 10 of the rotor core, the second end ring 12 to the opposite second side 13. The end rings 9, 12 can be made of a metallic material, in particular aluminum or an aluminum alloy. The end rings 9, 12 are mechanically connected to the rotor core 4, in particular by being axially clamped against each other by a plurality of clamping elements 40 distributed around the circumference. As shown in particular in the Fig. 1 B and Fig. As can be seen in 1C, the clamping elements 40 are arranged circumferentially in an area between two adjacent windings 5, 5'.

[0041] The first and second end rings 9, 12 are preferably of identical construction, so that the features described for one ring can also apply to the other. The end rings 9, 12 can have a flange section 42, on which the clamping elements 40 are axially supported, and a shell section 43, which substantially encloses the respective end windings 24, 26. As shown in particular in Fig. As can be seen in Figure 2, the end rings 9, 12 have a plurality of ribs 44 or web sections that extend axially along a radial inner circumference of the shell section 43. The web sections are axially supported against wedge elements 45, which are arranged in the slots 41 of the rotor core 6. The clamping elements 40 extend axially through the ribs 44 of the opposing end rings 9, 12 and the wedge elements 45 arranged axially between them. The slot wedges support the windings 5, 5' in the circumferential direction and help to hold them in position even under high centrifugal forces.

[0042] The L-shaped form of the end rings 9, 12, with flanged and shell sections, helps to temporarily collect the coolant flowing from the winding ends 24, 26. The end rings 9, 12 can have a plurality of holes 46 distributed around their circumference. The holes 46 can be located at the edge 11 between the flanged and shell sections. Circumferentially, the holes can be arranged between the openings 47 for the clamping elements 40. The holes 46 allow coolant flowing from the winding ends 24, 26 of the rotor assembly 2 to the winding ends of a stator of the electric machine.

[0043] The flow path F of the coolant from the inlet to the rotor shaft 3 to the outlet from the end rings 9, 12 is shown in the Fig. 6A to 6D are shown in more detail.

[0044] The Fig. 7A and Fig. Figures 7B show an electric machine 52 according to the invention with a rotor arrangement as shown in the Fig. Figures 1A to 6D show the electric machine 52 in the form of an electrically excited synchronous motor (EESM). It comprises a housing 53, a stator 54 connected to the housing 53, and a rotor assembly 2 according to the invention, as described above. The rotor assembly 2 is arranged coaxially with the stator 54 and is rotatably mounted about the axis of rotation in the housing 53 via corresponding bearings 55, 55'. The stator 54 comprises a stator core 56 and windings 57. The windings can be connected to an AC power supply to generate a rotating magnetic field.

[0045] It can be seen that the holes 46 of the end rings 9, 12 are arranged radially inside the winding ends 58, 58' of the stator windings 57, with axial overlap. In this way, coolant flowing from the winding ends 24, 26 to the end rings 9, 12 of the rotor assembly 2 can flow radially outwards through the holes 46 to cool the winding ends 58, 58' of the stator 54. This contributes to an overall efficient electrical machine. Reference symbol list 2 Rotor arrangement 3 Rotor shaft 4 rotor core 5 windings 6 Polar section 7 first fluid guidance element 8 second fluid guidance element 9 first end ring 10 first axial end 11 edge 12 second end ring 13 second axial end 14 axial bore 15 radial bore 16 ring-shaped recesses 17 Flange section 18 threaded sleeve 19 Entrance opening 20 Circumferential area 21 radial inner end 22 radial section 23 Head section 24 first winding end 25 first end surface 26 second winding end 27 second end surface 28 first axial channels 29 first outlet openings 30 second axial channels 31 second outlet openings 32 Fluid structure 33 outlet openings 34 first ring section 35 first winding carrier section 36 first head section 37 second ring section 38 second winding carrier section 39 second head section 40 clamping elements 41 Winding slot 42 Flange section 43 Mantle section 44 ribs 45 wedge elements 46 Outlet opening 47 Opening 48 Ring channel 49 Fluid bag 50 inner circumferential area 51 bore 52 electric machine 53 cases 54 Stator 55, 55' Lager 56 Stator core 57 windings 58, 58' winding ends Axis F River P level

Images