Rotor assembly for electrically excited synchronous motor (EESM)

Abstract

The invention relates to a rotor assembly (2) for an electrically excited synchronous motor (EESM), comprising a rotor shaft (3), a rotor core (4) with windings (5), first and second fluid-conducting elements (7, 8) arranged at the ends of the rotor core (4), the rotor shaft (3) comprising an axial bore (14) and a plurality of radial bores (15), the rotor core (4) comprises a plurality of inlet openings (19) fluidly connected to the radial bores (15) and axial channels (28, 30) extending axially to first and second outlet openings (29, 31) of the rotor core (4) wherein the first and second fluid guiding elements (7, 9) are fluidly connected to the outlet openings (29, 31) of the rotor core (4) and comprise a fluid structure (32) configured to receive a cooling fluid from the rotor core (4), the cooling fluid is guided to escape openings (33) which are arranged in the circumferential direction between two circumferentially adjacent winding ends (24) of the rotor.

Description

Technical Field

[0001] The present invention relates to a rotor assembly for an electrically excited synchronous motor (EESM) and an EESM having such a rotor assembly. Background Art

[0002] In an EESM, the rotation of the shaft is synchronized with the frequency of the supply current. The rotation period is specifically equal to an integer multiple of the alternating current (AC) cycle. Synchronous motors can use electromagnets as stators to generate a magnetic field that rotates in time with the oscillation of the current. The rotor can be provided with permanent magnets or electromagnets and rotates in unison with the stator magnetic field at the same rate. Thus, the rotor provides a synchronously rotating magnetic field.

[0003] An electric motor having a rotor and a stator is known from WO 2021 / 232835 A1. The rotor comprises a rotating shaft, a rotor core and a plurality of rotor coils. The rotor core is provided with a plurality of winding eyelets at intervals around the rotating shaft. A gap is formed between two adjacent rotor coils, and a first shaft eyelet is formed in the rotating shaft. The gap is configured as a first heat dissipation channel connected to the first shaft eyelet, and the first heat dissipation channel is used for cooling liquid flowing into the rotating shaft. In this way, the cooling liquid is introduced into the rotating shaft from the outside, and enters the first heat dissipation channel from the first shaft eyelet under the action of centrifugal force for heat dissipation of the rotor coil.

[0004] A wound rotor motor is known from US 11011960 B2, in which a rotating shaft is arranged in a vertical direction to immerse the lower coil portion of the stator and the rotor in cooling oil. The rotating shaft has a flow channel therein, through which the cooling oil moves upward from the area below the rotor and is ejected to the area above the rotor by the centrifugal force generated by the rotation of the rotor.

[0005] A wound-field motor including support and cooling members for coils is known from KR 10-1967731. The motor includes a rotor having a plurality of cores radially protruding from a center, a field coil wound around each core, and a plurality of cooling and supporting members having a cooling structure for discharging heat generated inside the rotor to the outside. The cooling and supporting members are included so that the coils wound around the rotor cores are firmly supported and forced convection of air is generated inside the rotor, thereby discharging heat generated in the rotor to the outside to maximize cooling performance.

[0006] A wound rotor is known from WO 2018095842 A1 (corresponding to FR 3059487), comprising a shaft having circumferentially alternating teeth and grooves, wherein each tooth receives a longitudinal winding intended to produce a rotor pole. Each winding defines a protruding coil head at each longitudinal end of the rotor. The rotor comprises at least one collar for mechanically holding the rotor winding, the collar being mounted at the longitudinal ends of the rotor to define a central opening toward the coil head. The collar has at least one escape duct to allow coolant to flow into the central opening so as to be provided to the coil head.

[0007] A cooling structure for an oil-cooled motor rotor is known from CN 114567102 A. The motor comprises a rotor having a shaft, a plurality of rotor core assemblies, a rotor end plate and an oil guide plate. The two axial ends of the rotor core are respectively covered with rotor end plates. A plurality of first heat dissipation oil paths connected outwardly in a radial direction are arranged on the end surface of the rotor end plate facing the rotor core. A plurality of first oil injection openings are annularly distributed in the outer circumference of the rotor end plate and are connected to the radial outer end of the first heat dissipation oil path.

[0008] EESMs are becoming increasingly popular, especially to replace medium and high power permanent magnet synchronous motors (PMSMs) and thus avoid heavy rare earth (HRE) magnets. However, the performance of EESMs is limited by the rotor and stator winding temperatures. Conventional EESMs with indirect cooling systems (such as housing water jackets or direct air cooling systems) have limited heat evacuation capabilities. In order to cope with increasingly demanding performance requirements, more advanced and more efficient direct cooling systems are needed. Summary of the invention

[0009] The object of the present invention is to provide a rotor assembly, in particular a rotor assembly for an electrically excited synchronous motor (EESM), which has an efficient cooling structure. The object of the present invention is also to provide an EESM having such a rotor assembly and thus having good cooling properties and a long service life.

[0010] According to the present invention, a rotor assembly for an electrically excited synchronous motor (EESM) is proposed, the rotor assembly comprising: a rotor shaft; a rotor core, the rotor core being connected to the rotor shaft and comprising a plurality of circumferentially distributed magnetic pole portions, windings being received around the magnetic pole portions, respectively, wherein the windings have a first winding end protruding axially from a first end face of the rotor core, and a second winding end protruding axially from a second end face of the rotor core on an opposite side, a first fluid guiding element arranged at the first end face of the rotor core, a second fluid guiding element arranged at the second end face of the rotor core, wherein the rotor shaft comprises an axial hole and a plurality of radial holes extending from the axial hole and arranged in an axial center region of the rotor shaft, wherein the rotor core comprises a plurality of inlet openings and axial channels, the inlet openings being fluidly connected to the rotor shaft A radial hole, an axial channel axially extending from an inlet opening to a first outlet opening at a first end surface of the rotor core and a second outlet opening at a second end surface of the rotor core, wherein a first fluid guiding element is fluidly connected to the first outlet opening of the rotor core and comprises a fluid structure, which is configured to receive cooling fluid from the first opening of the rotor core and guide the cooling fluid to a first escape opening arranged between two circumferentially adjacent first winding ends in a circumferential direction, and wherein a second fluid guiding element is fluidly connected to the second outlet opening of the rotor core and comprises a fluid structure, which is configured to receive cooling fluid from the second opening of the rotor core and guide the cooling fluid to a second escape opening arranged between two circumferentially adjacent second winding ends in a circumferential direction.

[0011] One advantage of the proposed rotor assembly is that a direct oil cooling system is provided that uses the centrifugal force caused by the rotation of the rotor to push the cooling fluid through the rotor and to the end windings. Therefore, the cooling fluid can be input into the hollow shaft using very low pressure. Within the shaft cavity, the cooling fluid is centrifugally distributed and forms a flow along the inner wall of the shaft, and then leaves the shaft through a set of conduits or radial holes that connect the shaft cavity to a channel extending across the rotor core. Once the cooling fluid leaves the rotor channel, it is fluidly connected to a fluid guiding element that is in contact with the rotor core, in particular with the end face of the rotor core. The fluid guiding element guides and releases the cooling fluid outwardly toward the winding ends of the rotor. The cooling fluid can be any fluid suitable for cooling and / or lubricating the electric machine, such as oil.

[0012] In order to feed the cooling fluid into the rotor shaft, a feed element may be provided, in particular so as to extend into the axial bore of the rotor shaft. For example, the feed element may be configured in the form of a static lance, which may be connected to the housing or to a bracket portion of the housing. In contrast to a rotary lance, the oil flow in a static lance is not affected by the motor speed. There will be no centrifugal forces in a static lance, thereby allowing good control of the oil flow towards the shaft.

[0013] The plurality of radial holes is arranged in a central region of the rotor shaft. More particularly, at least some of the plurality of radial holes of the rotor shaft may be arranged in a plane axially located within a central portion of the rotor core, for example within a central third of the rotor core. An advantage of providing the radial holes in the central region is that a cooling fluid may flow from there to the first and second sides of the rotor core, thereby already absorbing heat from the rotor core.

[0014] The rotor core may optionally consist of a plurality of lamination stacks. The central group of rotor laminations may include radial holes. The rotor laminations arranged axially adjacent to the central group may have the same design as each other. The axial channel extends through all lamination stacks to the axial end of the rotor core, where the cooling fluid can therefore leave the rotor core. The number of radial holes and axial channels of the rotor core may correspond to the number of magnetic pole portions, respectively windings, of the rotor assembly. The axial channels may be arranged circumferentially, for example, in the region of the magnetic pole portions, respectively windings. However, different numbers of channels and windings are also possible. The axial channel may be arranged radially between the inner circumferential surface of the rotor core and the radial inner end of the magnetic pole portion for receiving the winding. In other words, the channel may be arranged radially within the magnetic pole portion of the rotor core, in particular overlapping with the magnetic pole portion in the circumferential direction. The magnetic pole portion extends radially outward from the ring portion and may also be referred to as a salient pole or web portion.

[0015] According to one embodiment, the first and second guide elements may have the same design. Therefore, the features described for one guide element (first element) may also be applied to another guide element (second element). The fluid guiding element may include an annular channel fluidly connected to the outlet opening of the rotor core, and a plurality of fluid recesses fluidly connected to the annular channel and arranged at the inner circumferential surface of the guiding element. The escape opening is fluidly connected to a corresponding one of the fluid recesses. The annular channel of the fluid guiding element may be arranged to radially overlap relative to the side opening of the rotor core channel. Therefore, the cooling fluid leaving the axial channel gathers in the annular channel of the fluid guiding element, wherein the annular channel forms an annular pool of the cooling fluid. The annular pool is fluidly connected to the fluid recesses, and the fluid recesses respectively form axial reservoirs to centrifugally collect the cooling fluid before releasing the cooling fluid outward by overflow.

[0016] The escape opening of the fluid guiding element can have an axial extension of at least 0.25 times, in particular at least 0.5 times, in particular at least 0.75 times, the axial length of the end winding protruding from the end face of the rotor core. In this way, the opening has a slot-like design which, in combination with the reservoir design, promotes an axially wide oil cascade towards the rotor winding end. As a result, a particularly effective cooling of the end winding can be achieved.

[0017] In one embodiment, the fluid guiding element may include a first ring portion and a plurality of winding support portions radially protruding from the first ring portion. The winding support portion may include a head portion forming an enlarged end portion so that the end winding is prevented from sliding off the support portion. The end winding surrounds the winding support portion, i.e. surrounds and / or engages the corresponding winding support portion. In a cross-sectional view, the winding support portion may be formed corresponding to the magnetic pole portion of the rotor core, i.e., so as to form a lateral extension of the magnetic pole portion. The windings, which may also be referred to as coils, extend in a closed loop around the associated magnetic pole portion of the rotor core, the first winding support portion of the first fluid guiding element, and the second winding support portion around the second fluid guiding element at the opposite end. In an embodiment with a winding support portion, the fluid guiding element performs two functions, i.e., cooling and supporting the end windings. Therefore, the fluid guiding element may also be referred to as a cooling element and / or a support element.

[0018] The fluid guiding element may be made of a non-conductive material, in particular a material different from the rotor core material. For example, a plastic material may be used for the fluid guiding element. As mentioned above, some or all of the above configurations may apply to the first and / or second guiding element.

[0019] In one embodiment, the first end ring may be arranged at a first side of the rotor core, and the second end ring may be arranged at an opposite second side. The first and / or second end ring may be made of a metal material, such as, in particular, aluminum or an aluminum alloy, but not limited thereto. The end ring may be mechanically connected to the rotor core, more particularly to the rotor stack. In one embodiment, the first and second end rings may be axially clamped against each other by a plurality of clamping or tensioning elements. Each clamping element may be arranged between two windings in a circumferential direction. The first and / or second end ring may include a flange portion for supporting the tensioning element and a jacket portion that substantially surrounds the end winding. Thus, if viewed in a semi-longitudinal cross section, the end ring has an L-shape. In addition, the end ring may include a plurality of platform portions extending axially along the radial inner circumference of the jacket portion. The tensioning member may extend axially through the platform portion, and the platform portion may be arranged respectively between two circumferentially adjacent end windings.

[0020] In a preferred embodiment, the end rings may be formed to collect cooling fluid from the rotor winding ends to effectively redirect the fluid towards the winding ends of the stator through some specifically positioned holes through the outer part of the ring. These holes or openings allow cooling fluid flowing from the fluid guiding elements to the end windings to be temporarily captured within the end rings, from where the cooling fluid escapes radially outwards through the openings and can be flung towards the stator by centrifugal forces before returning to the cooling system. The openings of the end rings may be arranged circumferentially offset relative to the escape openings of the corresponding fluid guiding elements.

[0021] 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 portions. In each longitudinal recess, a wedge element can be arranged respectively between two windings adjacent in the circumferential direction. The wedge can be fixed in the longitudinal recess to prevent the rotor windings from being released from the winding slots by centrifugal force.

[0022] The object is also achieved by an electrically excited synchronous motor (EESM), comprising: a housing; a stator arranged in the housing and comprising a stator core and a winding; and a rotor rotatably supported in the housing about a rotation axis, the rotor being constructed according to any of the above-described embodiments. In this way, an EESM having very good cooling properties and thus a long service life is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The preferred embodiments are described below with reference to the accompanying drawings.

[0024] Figure 1A A rotor assembly for an electric machine is shown in longitudinal section;

[0025] Figure 1B The first cross-sectional view according to the section line 1B-1B shows Figure 1A A rotor assembly;

[0026] Figure 1C A second cross-sectional view according to section line 1C-1C shows Figure 1A A rotor assembly;

[0027] Figure 2 A three-dimensional exploded view shows Figure 1A A rotor assembly;

[0028] Figure 3A A partially cutaway view shows Figure 1A a rotor assembly into which a cooling fluid flow is drawn;

[0029] Figure 3B The modified embodiment is shown Figure 1A A rotor assembly;

[0030] Figure 4 A perspective view of one end portion of the assembly is shown with a partial cutaway view. Figure 1A Details of the rotor assembly;

[0031] Figure 5A A perspective view showing the side of the fluid guiding element facing the rotor core is shown. Figure 1A Details of the rotor assembly;

[0032] Figure 5B Shown as a partially cutaway detail Figure 1Aa fluid guiding element of a rotor assembly;

[0033] Figure 5C The cross-sectional view shows Figure 5A a portion of a fluid guiding element;

[0034] Figure 5D Shows Figure 5C an axial view of a fluid guiding element, into which a cooling fluid flow is sucked;

[0035] Fig. 6A A partially cutaway perspective view shows Figure 1A a first detail of the flow path F of the rotor assembly;

[0036] Figure 6B A partially cutaway perspective view shows Figure 1A a second detail of the flow path F of the rotor assembly;

[0037] Figure 6C A partially cutaway perspective view shows Figure 1A a third detail of the flow path F of the rotor assembly;

[0038] Fig.6D A partially cutaway perspective view shows Figure 1A a fourth detail of the flow path F of the rotor assembly;

[0039] Fig. 7A The electric motor according to the invention is shown in a longitudinal section, the electric motor comprising Figures 1A-6D The rotor assembly shown, and

[0040] Figure 7B A partially cutaway perspective view shows Fig. 7A Electric motor components. DETAILED DESCRIPTION

[0041] The following will be combined with the description Figures 1A to 6D A rotor assembly 2 according to the invention is shown for an electric machine 2 , in particular for an electrically excited synchronous motor (EESM).

[0042] The rotor assembly 2 comprises the following components: a rotor shaft 3, a rotor core 4 connected to the rotor shaft 3, a winding 5 received on a magnetic pole portion 6 of the rotor core 4, and a fluid guiding 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 is provided at an opposite second axial end 13 of the rotor core. The rotor shaft 3 comprises an axial hole 14 and a set of radial holes 15.

[0043] In the mounted state of the rotor assembly, a supply element (not shown) may be provided which may extend axially into the axial bore 14 of the rotor shaft 3. For example, the supply element may be configured in the form of a static spray gun which may be connected to the housing or a bracket portion of the housing. In contrast to a rotary spray gun, the oil flow in a static spray gun is not affected by the motor speed. There will be no centrifugal forces in a static spray gun, allowing good control of the oil flow towards and into the shaft.

[0044] The rotor shaft 3 may optionally have an annular recess 16 on the inner circumferential surface in the axial region of the radial hole 15. Therefore, the cooling fluid flowing along the inner wall of the axial hole 14 by centrifugal force very easily reaches the opening of the radial hole 15, which is arranged radially backward compared to the radius of the end portion of the inner shaft wall. Figure 1A and 1B As shown, the group of radial holes 15 is preferably arranged in a plane P, but is not limited thereto. The radial holes 15 are particularly arranged in the central region of the rotor shaft 3. More specifically, at least some of the radial holes 15 are arranged in a plane P, which is axially located in the middle section of the rotor core 4, particularly in the middle third of the rotor core, for example, exactly in the middle of the rotor core.

[0045] The rotor core 4 is firmly connected to the rotor shaft 3. The axial connection can be provided by the rotor core 4 being axially supported at one end against a flange portion 17 of the rotor shaft 3 and axially clamped by a sleeve 18 threaded onto the rotor shaft 3 at the opposite end. The rotationally fixed connection can be provided by a force-locking engagement (such as an intermediate fit) and / or a form-locking engagement (such as a spline connection) between the rotor shaft 3 and the rotor core 4. The rotor core 4 includes a plurality of axially extending recesses 41 at a radially outer section of the rotor core, and the pole portions 6, 6' are respectively formed between two circumferentially adjacent recesses 41. The recesses 41 may also be referred to as slots.

[0046] Each pole part 6, 6' carries a winding 5, 5' which surrounds the corresponding pole in a closed loop, in particular as Figure 2 Therefore, the pole section can also be called the winding bracket or salient pole. In the cross-sectional view, as shown in Figure 1B and 1CAs shown, the winding carrier can have a T-shape with a radial portion 22 and a head portion 23 that widens in the circumferential direction relative to the radial portion. The T-shape also contributes to the reliable positioning of the windings 5, 5' even at high rotational speeds and prevents the windings from escaping from the winding carrier due to centrifugal forces. The windings 5, 5' (also referred to as coils) each include a first winding end 24 that extends axially beyond a first end face 25 of the rotor core, and a second winding end 26 that protrudes axially beyond a second end face 27 of the rotor core 4 on the opposite side. The winding ends 24, 25 form a U-shaped return portion of the winding. The windings 5, 5' carried by the rotor core 4 generate a constant magnetic field. Therefore, in an activated condition, the rotor core 4 rotates around the axis of rotation A to drive the rotor shaft 3 and the transmission system rotatably connected thereto.

[0047] At the radial inner circumferential surface 20, the rotor core 4 comprises a plurality of inlet openings 19, which are fluidically connected to the radial holes 15 of the rotor shaft 3. To this end, the inlet openings 19 of the rotor core 4 are preferably arranged in line with the radial outlet openings of the rotor shaft 3. The inlet openings 19 can extend radially up to the axial channels connected thereto. More particularly, a first axial channel 28 extends axially from the inlet openings 19 to a first outlet opening 29 at the first end face 25 of the rotor core 4, and a second axial channel 30 extends to a second outlet opening 31 at the second end face 27 of the rotor core.

[0048] The rotor core 4 may be composed of a plurality of stacked laminations. Figure 1A and 1B As can be seen in FIG. 1 , a set of central rotor laminations includes an inlet opening 19. Figure 1C As shown, the rotor laminations arranged axially adjacent to the center lamination preferably have the same configuration as each other. The lamination stacks form axially extending channels 28, 30. The axial channels 28, 30 extend through all lamination stacks to the axial ends 25, 27 of the rotor core 4. From the middle section of the rotor core 4, part of the cooling fluid flows in a first axial direction to the first side 10, and part of the cooling fluid flows in an opposite second axial direction to the second side 13, thereby absorbing heat from the rotor core 4.

[0049] Especially from Figure 1B and 1C As can be seen in the figure, the number of radial holes 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', respectively the windings 5, 5'. Furthermore, the axial channels 28, 30 are arranged radially between the inner circumferential surface 20 of the rotor core and the radial inner end 21 and / or the shoulder of the pole section 6, 6', where the windings 5, 5' are received. However, it is to be understood that the number and arrangement of the radial and axial channels may also differ from the example shown here.

[0050] The first fluid guiding element 7 and the second fluid guiding element 8 are in particular arranged to axially contact the end faces 25, 27 of the rotor core. The fluid guiding elements 7, 8 are preferably connected to the rotor core 4 via a first end ring 9 and a second end ring 12 which are clamped to the rotor core 4. In the present embodiment, the first and second fluid guiding elements 7, 8 have the same design, so that the features described for one element also apply to the other element. The first fluid guiding element 7 is fluidically connected to the first outlet opening 29 of the rotor core 4 and comprises a fluid structure 32 which is configured to receive the cooling fluid and guide the cooling fluid to a first escape opening 33 which is arranged in the circumferential direction between two circumferentially adjacent end windings 5, 5'.

[0051] More specifically, the fluid guiding element 7, 8 comprises a ring portion 34 and a plurality of winding support portions 35 radially protruding from the ring portion. Figures 5A to 5C As can be seen in FIG. 1 , the ring portion 34 comprises an annular channel 48 and a plurality of fluid pockets 49 at the axial ends contacting the adjacent end faces 25, 27 of the rotor core 4, the fluid pockets 49 being fluidically connected to the annular channel and arranged at the inner circumferential surface 50 of the fluid guiding elements 7, 8. The annular channel 48 is configured to receive cooling fluid from the adjacent outlet openings 29 of the rotor core. To this end, the annular channels 48 of the fluid guiding elements 7, 8 are preferably arranged radially overlapping with respect to the side openings 29 of the rotor core channels. Thus, the cooling fluid leaving the axial channels 28, 30 is collected in the annular channels 48 of the respective fluid guiding elements 7, 8, wherein an annular pool of cooling fluid is formed by the annular channels 48. The annular pool is fluidically connected to the fluid pockets 49, which respectively form axial reservoirs to centrifugally collect the cooling fluid before overflowing to release the cooling fluid outwards through radial holes 51, which extend through the ring portion 34 of the fluid guiding elements 7, 8. The radial holes 51 fluidically connect the radially inner fluid pocket 49 with the radially outer escape opening 33. The radial holes 51 and / or the escape opening 33 have an axial extension which is in particular at least 0.5 times, more in particular at least 0.75 times, the axial length of the end windings 24, 26 protruding from the end face of the rotor core. Figure 5D As shown, the slot-like design thus formed in combination with the reservoir design facilitates an axially wide oil flow of the cooling fluid towards the winding ends 24 , 26 of the rotor.

[0052] The winding support part 35 comprises a head part 36 forming an enlarged end, so that the end windings 24, 26 are prevented from sliding off the support part 35 due to centrifugal forces. The end windings 24, 26 surround the winding support part 35, 38 in a U-shape in a radial view. In a cross-sectional view, the winding support part 35, 38 is preferably formed to correspond to the pole part 6, 6' of the rotor core 4, i.e., so as to form a lateral extension of the pole part 6, 6' at the axial end of the rotor core. The windings 5, 5' extend in a closed loop around the associated pole part 6, 6' of the rotor core, the first winding support part 35 of the first fluid guiding element 7 and the second winding support part 38 around the second fluid guiding element 8 at the opposite end, respectively. The fluid guiding elements contribute to good cooling and support of the end windings 24, 26. The fluid guiding elements 7, 8 can be made of a non-conductive material, in particular a plastic material.

[0053] The first end ring 9 is arranged at a first side 10 of the rotor core and the second end ring 12 is arranged at an opposite second side 13. The end rings 9, 12 can be made of a metallic material, in particular aluminium or an aluminium alloy. The end rings 9, 12 are mechanically connected to the rotor core 4, in particular by being axially clamped towards each other by a plurality of clamping elements 40 distributed over the circumference. In particular Figure 1B and 1C It can be seen in FIG. 4 that the clamping element 40 is arranged circumferentially in the region between two adjacent windings 5 ​​, 5 ′.

[0054] The first and second end rings 9, 12 preferably have the same design, so that the features described for one ring can also apply to the other ring. The end rings 9, 12 may include a flange portion 42, against which the tensioning element 40 is axially supported, and a jacket portion 43 which substantially surrounds the respective end winding 24, 26. In particular, Figure 2 As can be seen in Figure 4, the end rings 9, 12 comprise a plurality of ribs 44, respectively platform portions extending axially along the radially inner circumference of the jacket portion 43. The platform portions bear axially against wedge elements 45 arranged in the slots 41 of the rotor core 6. The tensioning members 40 extend axially through the ribs 44 of the opposing end rings 9, 12 and the wedge elements 45 arranged axially therebetween. The groove wedges support the windings 5, 5' in the circumferential direction and help to keep them in place even under high centrifugal forces.

[0055] The L-shape of the end ring 9, 12 with the flange portion and the jacket portion helps to temporarily collect the cooling fluid thrown off the winding ends 24, 26. The end ring 9, 12 may include a plurality of eyelets 46 distributed over the circumference. The eyelets 46 may be arranged at the edge 11 between the flange portion and the jacket portion. In the circumferential direction, the eyelets may be arranged between the openings 47 for the clamping members 40. By means of the eyelets 46, the cooling fluid from the winding ends 24, 26 of the rotor assembly 2 may be directed towards the winding ends of the stator of the electric machine.

[0056] The flow path F of the cooling fluid from entering the rotor shaft 3 to leaving the end rings 9, 12 is Figures 6A to 6D is shown in more detail in .

[0057] Fig. 7A and 7B An electric machine 52 according to the present invention is shown, which has a Figures 1A to 6D The motor 52 is constructed in the form of an electrically excited synchronous motor (EESM). It includes a housing 53, a stator 54 connected to the housing 53, and a rotor assembly 2 according to the present invention as described above. The rotor assembly 2 is coaxially arranged with the stator 54 and is rotatably supported in the housing 53 around the axis of rotation by corresponding bearings 55, 55'. The stator 54 includes a stator core 56 and a winding 57. The winding can be connected to an AC power supply to generate a rotating magnetic field.

[0058] 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 winding 57, with an axial overlap. In this way, the cooling fluid flowing from the winding ends 24, 26 to the end rings 9, 12 of the rotor assembly 2 can flow through the holes 46 on the radial outside to cool the winding ends 58, 58' of the stator 54. This helps to improve the overall efficiency of the electric machine.

[0059] Reference numerals

[0060] 2 Rotor assembly

[0061] 3 Rotor shaft

[0062] 4 Rotor core

[0063] 5 Winding

[0064] 6 Magnetic pole part

[0065] 7 First fluid guiding element

[0066] 8 Second fluid guiding element

[0067] 9 First end ring

[0068] 10 First axial end

[0069] 11 Edge

[0070] 12 Second end ring

[0071] 13 Second axial end

[0072] 14 Axial hole

[0073] 15 Radial holes

[0074] 16 Annular concave part

[0075] 17 Flange

[0076] 18 Threaded sleeve

[0077] 19 Entrance opening

[0078] 20 Circumference

[0079] 21 Radial inner end

[0080] 22 Radial section

[0081] 23 Head

[0082] 24 First winding end

[0083] 25 First end face

[0084] 26 Second winding end

[0085] 27 Second end face

[0086] 28 First axial channel

[0087] 29 First exit opening

[0088] 30 Second axial channel

[0089] 31 Second exit opening

[0090] 32 Fluid Structure

[0091] 33 Escape Opening

[0092] 34 First Ring Section

[0093] 35 First winding support part

[0094] 36 First head part

[0095] 37 Second Ring Section

[0096] 38 Second winding support part

[0097] 39 Second head part

[0098] 40 Clamping member

[0099] 41 Winding groove

[0100] 42 flange part

[0101] 43 Sheath part

[0102] 44 ribs

[0103] 45 Wedge element

[0104] 46 Exit opening

[0105] 47 Opening

[0106] 48 Ring Channel

[0107] 49 fluid pockets

[0108] 50 Inner circumference

[0109] 51 holes

[0110] 52 Motor

[0111] 53 Shell

[0112] 54 Stator

[0113] 55,55' bearings

[0114] 56 stator core

[0115] 57 Winding

[0116] 58,58' Winding end

[0117] A axis

[0118] F Flow

[0119] P-Plane

Claims

1. A rotor assembly (2) for an electrically excited synchronous motor (EESM), comprising: The rotor shaft (3), A rotor core (4) connected to the rotor shaft (3) and comprising a plurality of circumferentially distributed pole sections (6, 6'), wherein windings (5, 5') are received around the pole sections (6, 6'), respectively, wherein the windings (5, 5') have a first winding end (24) protruding axially from a first end face (25) of the rotor core (4) and, on the opposite side, have a second winding end (26) protruding axially from a second end face (27) of the rotor core (4), a first fluid guiding element (7) arranged at a first end of the rotor core (4), a second fluid guiding element (8) arranged at a second end of the rotor core (4), The rotor shaft (3) comprises an axial hole (14) and a plurality of radial holes (15), wherein the radial holes extend from the axial hole and are arranged in an axial center region of the rotor shaft (3). The rotor core (4) comprises a plurality of inlet openings (19) fluidically connected to radial holes (15) of the rotor shaft (3) and axial channels (28, 30), wherein the axial channels (28, 30) extend axially from the inlet openings (19) to a first outlet opening (29) at a first end face (25) of the rotor core (4) and a second outlet opening (31) at a second end face (27) of the rotor core (4), wherein the first fluid guiding element (7) is fluidically connected to a first outlet opening (29) of the rotor core (4) and comprises a fluid structure (32) which is configured to receive cooling fluid from the first outlet opening (29) of the rotor core (4) and to guide the cooling fluid to a first escape opening (33) arranged in a circumferential direction between two circumferentially adjacent first winding ends (24), and The second fluid guiding element (8) is fluidically connected to a second outlet opening (31) of the rotor core (4) and comprises a fluid structure, which is configured to receive cooling fluid from the second outlet opening (31) of the rotor core (4) and guide the cooling fluid to a second escape opening arranged in the circumferential direction between two circumferentially adjacent second winding ends (26).

2. The rotor assembly according to claim 1, Features A supply element is provided for introducing a cooling fluid into the axial bore (14) of the rotor shaft (3).

3. The rotor assembly according to claim 1 or 2, Features At least some of the plurality of radial holes (15) of the rotor shaft (3) are arranged in a plane (P) axially located in a central portion of the rotor core (4).

4. A rotor assembly according to any one of claims 1 to 3, Features The number of radial holes (15) and axial channels (28, 30) of the rotor core (4) corresponds to the number of magnetic pole sections (6, 6').

5. The rotor assembly according to any one of claims 1 to 4, Features The axial channel (28, 30) is arranged radially inside a pole portion (6, 6') receiving the winding (5, 5').

6. A rotor assembly according to any one of claims 1 to 5, Features The first fluid guiding element (7) comprises a first annular channel (48) fluidically connected to a first outlet opening (29) of the rotor core (4), and a plurality of first fluid recesses (49) fluidically connected to the first annular channel (48) at an inner circumferential surface (50), wherein the first escape openings (33) are fluidically connected to the first fluid recesses (49), respectively, and / or the second fluid guiding element (8) comprises a second annular channel fluidically connected to a second outlet opening of the rotor core (4), and a plurality of second fluid recesses fluidly connected to the second annular channel at an inner circumferential surface, wherein the second escape openings are fluidically connected to the second fluid recesses, respectively.

7. The rotor assembly according to claim 6, Features The first escape opening (33) of the first fluid guiding element (7) has an axial extension which is at least 0.25 times the axial length of the first end winding (24) protruding from the first end face (25) of the rotor core (4), and / or The second escape opening of the second fluid guiding element has an axial extension which is at least 0.25 times the axial length of the second end winding (26) protruding from the second end face (27) of the rotor core (4).

8. A rotor assembly according to any one of claims 1 to 7, Features The first fluid guiding element (7) comprises a first ring portion (34) and a plurality of first winding support portions (35) radially protruding from the first ring portion (34), wherein a first head portion (36) forms an enlarged end of the first winding support portion (35), wherein the first end winding (24) surrounds the first winding support portion (35), and / or The second fluid guiding element (8) comprises a second ring portion (37) and a plurality of second winding support portions (38) protruding radially from the second ring portion (37), wherein a second head portion (39) forms an enlarged end of the second winding support portion (38), wherein the second end winding (26) surrounds the second winding support portion (38).

9. A rotor assembly according to any one of claims 1 to 8, Features At least one of the first fluid guiding element (7) and the second fluid guiding element (8) is made of a non-conductive material different from the material of the rotor core (4).

10. A rotor assembly according to any one of claims 1 to 9, Features A first end ring (9) is arranged at a first side of the rotor core (4) and a second end ring (12) is arranged at an opposite second side, wherein the first end ring (9) and the second end ring (12) are axially clamped against each other by a plurality of clamping elements (40) extending respectively between two circumferentially adjacent windings (5, 5'), At least one of the first end ring (9) and the second end ring (12) comprises a flange portion (42) for supporting the clamping element (40) and a jacket portion (43) surrounding the end winding (5, 5'), wherein the end ring comprises a plurality of outlet openings (46).

11. A rotor assembly according to any one of claims 1 to 10, Features The outlet openings (46) of the end rings (9, 12) are arranged circumferentially offset relative to the outlet openings (33) of the respective fluid guiding elements (7, 8).

12. A rotor assembly according to any one of claims 1 to 11, Features The end ring (9, 12) comprises a plurality of ribs (44) extending axially between two circumferentially adjacent end windings (5, 5').

13. A rotor assembly according to any one of claims 10 to 12, Features The end ring (9) is made of a non-ferromagnetic material, in particular aluminum.

14. A rotor assembly according to any one of claims 1 to 13, Features Winding slots (41) are formed in the rotor core (4) between two magnetic pole parts (6, 6') adjacent to each other in the circumferential direction, wherein: The wedge elements (45) are respectively arranged between two windings (5, 5') adjacent to each other in the circumferential direction.

15. An electrically excited synchronous motor (EESM) comprising: a housing (53), a stator (54) arranged in the housing (53) and comprising a stator core (56) and a winding (57), and a rotor assembly (2) rotatably supported in the housing (53) about a rotation axis (A), Characterized in that the rotor assembly (2) is constructed according to any one of claims 1 to 14.

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