Electrical machinery

Abstract

An electric machine (1) having a stator (2) and a rotor (3), the stator (2) and / or rotor having a steel lamination stack (13) made of identical steel laminations (8,9) of substantially the same shape having a plurality of openings (10), the laminations (8,9) forming a plurality of fluid cooling passages (7,18,19,20,22) extending axially through the stack when stacked one on top of another, the plurality of steel laminations (8,9) having different orientations in the stack (13) relative to other steel laminations (8,9) in the stack (13), whereby the fluid cooling passages (7,18,19,20,22) form serpentine cooling paths extending axially through the stack (13). A method of assembling an electric machine includes rotating or flipping a plurality of steel laminations (8,9) relative to one another before or during assembly of the stack (13).

Description

[Technical field]

[0001] The invention relates to an electric machine according to the preamble of independent claim 1 and to a method for assembling an electric machine according to independent claim 19.

[0002] Background technology The electric machine has a stator and / or rotor formed from a steel lamination stack. A known prior art stator is disclosed in US Patent Application Publication No. 2020 / 0373803. The stator has at least one stator winding with conductor bars, which are placed in slots of the stator lamination stack and fixed to the slots of the stator lamination stack by a fixing device. Direct cooling of the windings can be achieved by providing a space in the slot between the conductor bars and the lamination stack.

[0003] overview An advantage of the electric machine according to the invention as defined in claim 1 is that it allows for a more efficient transfer of heat from the laminate stack and at the same time simplifies the manufacture of the electric machine, and more particularly the laminate stack.

[0004] This is realised according to a first aspect of the invention by an electric machine having a stator and rotor, the stator and / or rotor having a steel lamination stack, the steel lamination stack consisting of substantially identically shaped steel laminations having a plurality of openings, the steel laminations forming a plurality of fluid cooling passages extending axially through the stack when stacked one on top of another, the plurality of steel laminations having different orientations in the stack relative to other steel laminations in the stack, whereby the fluid cooling passages form serpentine cooling passages extending axially through the stack.

[0005] Laminations having substantially the same shape mean that they can be formed using the same stamping die. The axial or longitudinal direction is understood to be parallel to the axis of rotation of the rotor of the electric machine, while the radial and circumferential directions are respectively oriented radially relative to and circumferentially around the axis of rotation.

[0006] As a result of using laminations of the same shape but with different orientations in the stack, serpentine cooling passages can be created in the cooling passages, which increases turbulence and improves cooling efficiency in the passages.

[0007] Each steel lamination may have a protrusion that extends into the fluid cooling passage, such that the protrusions in at least one pair of adjacent steel laminations are located on opposite sides of the fluid cooling passage. Thus, the steel laminations of at least one pair of adjacent steel laminations have different orientations, such that one protrusion in a passage is formed by one steel lamination and another protrusion in the opposite direction is formed by an adjacent lamination in the same passage. The use of protrusions into the cooling passage further increases turbulence in the cooling flow, improving cooling efficiency.

[0008] The protrusions may extend circumferentially or radially into the fluid-cooling passages.

[0009] Advantageously, the opening may have an elongated shape and the protrusion may extend into the fluid-cooling passage in the elongated direction of the opening, such that the cooling passage has a particularly winding serpentine cooling path, since the protrusion may extend over a majority of the elongated direction of the opening.

[0010] In one embodiment, the different orientations are achieved by the steel laminations being rotationally offset in the circumferential direction relative to another steel lamination. Thus, the same die can be used to cut the laminations, and then, when assembled, some of the laminations are rotated by a predetermined angle relative to another lamination, such that the openings in the adjacent laminations are aligned to form the cooling passages. Thus, two adjacent openings in each one of the steel laminations can have different shapes, and fluid cooling passages are formed in the stack by alternating between two adjacent openings of different shapes in each steel lamination, thereby forming a serpentine cooling passage extending axially through the stack.

[0011] The protrusions extend radially into the fluid-cooling passage from either the radially inner or radially outer side of the fluid-cooling passage, but only in embodiments where the different orientation is achieved by rotationally offsetting the circumference of the respective steel laminations. Radially extending protrusions allow the cooling passage to be stretched radially while still forming a serpentine cooling passage.

[0012] Alternatively, the different orientations can be achieved by arranging steel laminations in an inverted and non-inverted orientation in the stack, with openings in the same steel laminations formed asymmetrically, such that the fluid cooling passages form serpentine cooling paths extending axially through the stack.

[0013] By asymmetrically positioning the openings in the laminations, the openings in adjacent inverted and non-inverted laminations are fluidly connected but are not precisely aligned, thus creating a serpentine path as opposed to a straight path as known in the prior art. The serpentine path increases turbulence in the cooling passages and improves heat transfer to the cooling fluid. The asymmetry of the openings can be achieved by forming asymmetric shapes for the openings or by asymmetrically positioning the openings on or about radial lines that are aligned in both the inverted and non-inverted laminations in the lamination stack.

[0014] The steel lamination stack can be formed from a plurality of packages, whereby in each package the steel laminations have the same orientation and, when assembled into the stack, alternating packages each have a first orientation and a second, different orientation.

[0015] Each package may advantageously have at least 10 steel laminations, which aids in assembly, but it is also possible for each lamination in the stack and adjacent laminations to be arranged in a different orientation.

[0016] In another embodiment, the number of laminations in each package varies along the axial length of the stack. In this way, the cooling performance can be varied along the axial length of the stack, for example to improve cooling on the package side where the preheated cooling medium exits the cooling passage. Thus, the number of laminations in one package can be less than the number of laminations in the adjacent package that forms the upstream portion of the cooling passage.

[0017] In one embodiment, the stator and / or rotor is provided with a plurality of circumferentially spaced axially and radially extending slots that house the windings extending axially therethrough, and each slot also houses at least one of a plurality of fluid cooling passages. The provision of serpentine cooling passages in the region of the slots is particularly advantageous, since the cooling fluid flowing through the passages can efficiently transfer heat generated in the windings.

[0018] The windings may be in the form of conductor bars or hairpins, with at least one protrusion arranged to radially separate two adjacent conductor bars or hairpins. In this case, a cooling passage is formed between the two adjacent conductor bars or hairpins. The protrusion thus forms part of the serpentine passage and also serves to radially separate the two adjacent conductor bars or hairpins.

[0019] Protrusions may also be used to separate windings of different phases, where the thin primary insulation of the winding bars does not provide sufficient insulation alone.

[0020] Additionally or alternatively, a protrusion in the cooling passage can be positioned to support at least one of the conductor bar or the hairpin.

[0021] In the case of a stator, the protrusions can alternatively or additionally be arranged between the radially innermost conductor bar or hairpin and the adjacent conductor bar or hairpin, as it has been found that in this position the greatest heat is generated in the winding and therefore the cooling passages formed at this position can more efficiently transfer heat away from the winding.

[0022] In another embodiment, one of the plurality of fluid-cooling passages is disposed in a stator slot radially inward of the winding, the stator slot preferably being closed radially inward toward the rotor such that the stator slot containing the winding and at least one of the plurality of fluid-cooling passages is not in direct fluid communication with the rotor.

[0023] Thus, any cooling fluid flow entering the fluid-cooling passages in the slots at one end of the lamination stack generally snakes axially through the protrusions to the other end of the lamination stack.

[0024] Additionally or alternatively, multiple fluid cooling passages can be located in the steel lamination stack spaced from the respective rotor or stator slots that house the windings In this manner, heat can be more uniformly transferred from the lamination stack, thereby reducing thermal stresses in the lamination stack.

[0025] Additionally or alternatively, a plurality of fluid cooling passages are disposed on the outer surface of the lamination stack, which may further aid in uniform heat transfer from the lamination stack to relieve thermal stresses, where the fluid cooling passages are closed radially outwardly by a sleeve or housing.

[0026] The cooling fluid is preferably oil or other insulating fluid to prevent electrical currents between the laminations.

[0027] In a second aspect of the invention, there is provided a method of assembling an electric machine having a stator and rotor, the stator and / or rotor being assembled into a steel lamination stack, the steel lamination stack being comprised of substantially identically shaped steel laminations having a plurality of openings, the steel laminations forming a plurality of fluid cooling passages extending axially through the stack when stacked one on top of another, the plurality of steel laminations having different orientations in the stack relative to other steel laminations in the stack, whereby the fluid cooling passages form serpentine cooling passages extending axially through the stack, and assembling the stack comprising rotating or flipping the plurality of steel laminations relative to the other steel laminations prior to or during assembling the stack.

[0028] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0029] [Figure 1] 1 is a schematic cross-sectional view of an electric machine; [Diagram 2] FIG. 2 is a cross-sectional view of a stator according to one embodiment of the present invention. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of a portion of the stator in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view of a cooling passage of the stator of FIG. 2. [Figure 5a] 1 is a schematic cross-sectional view of a portion of a steel laminate according to one embodiment of the present invention. [Figure 5b] 1 is a schematic cross-sectional view of a portion of an electric machine according to one embodiment of the present invention.

[0030] Detailed Description FIG. 1 shows one embodiment of an electric machine 1 having a rotor 3 rotating about a central longitudinal axis 4 and a stator 2 surrounding the rotor 3. The stator 2 has windings 5 ​​in the form of wires, bars or hairpins which, when electrically excited, generate a magnetic field which interacts with a magnetic field generated in the rotor 3 to exert a rotational force on the rotor 3. Although the rotor 3 is shown radially inside the stator 2, it is possible to instead be located radially outside the stator 2 and surround it. As can be seen in FIG. 1, the stator 2 is comprised of at least one steel lamination stack 8. The rotor 3 may also be comprised of at least one steel lamination stack 9. According to the invention, the stator 2 and / or the rotor 3 have cooling passages 7 extending in the longitudinal direction 6 through the steel lamination stacks 8, 9. A cooling fluid is arranged to flow through cooling passages 7 in the longitudinal direction 6 through the stator 2 and / or rotor 3 to transfer heat from the stator 2 or from the rotor 3 .

[0031] 2 and 3 show diagrams of one embodiment of the present invention in which cooling passages are formed in stator laminations 8. The stator laminations 8 are formed to have substantially the same shape. That is, the stator laminations 8 have the same pattern of slots or openings 10 and can therefore be made using one stamping die. The stator laminations 8 are arranged in packages 11, 12. Each package contains a number of steel laminations 8, with the laminations 8 in the packages 11, 12 all oriented in the same direction. However, alternative packages are arranged such that the laminations 8 in adjacent packages 11, 12 are oriented in a flipped and non-flipped direction, respectively. Each package may have at least ten laminations. When a stator lamination 8 is stacked on top of another stator lamination 8, the slots or openings 10 in the stator laminations align to form the cooling passages 7. The openings 10 are arranged asymmetrically in the laminations 8. This means that if the laminations are flipped, the openings 10 will not align correctly. The asymmetry of the openings 10 is designed such that the flow path through the lamination stack has a serpentine shape, with the lamination packages 11 having an inverted orientation and the lamination packages 12 having a non-inverted orientation, as can be seen in Figure 4. Although Figures 2 and 3 relate to a stator, the basic approach applies equally to a rotor 3 consisting of a stack 13 of laminations 9. The cooling passages 7 are defined by the openings 10 in the laminations 8, so that the cooling fluid is in direct contact with the laminations 8. Therefore, the cooling fluid should be an insulating fluid, e.g. oil, to prevent current flow between the laminations.

[0032] In the embodiment shown in FIG. 3, the stator 2 has a number of stator slots 14 extending in the longitudinal direction 6 through the stator 2. The windings 5 ​​in the form of bars or hairpins are arranged in the slots 14. The slots 14 are closed on the radially inner side, so that the cooling fluid flowing through the slots 14 does not enter the rotor gap, i.e. the space between the rotor 3 and the stator 2. The slots 14 are arranged circumferentially spaced apart in the stator 2. The slots 14 are formed by asymmetrically formed openings 10 in each of the laminations 8. In this embodiment, the asymmetry of each opening 10 is formed by at least one protrusion 15, 16 extending circumferentially to one side of the opening 10. Thus, as shown in FIGS. 3 and 4, the opening 7 can be provided with a protrusion 16 at its radially inner end. When such laminations are arranged in a package with alternating inverted and non-inverted orientations of the laminations, internal cooling passages 7, 18 having a serpentine shape can be realized, as shown in FIG. 4a). The radially outer side of the inner cooling passage 18 may be defined by the winding 5. The serpentine shape of the cooling passage 7 increases the turbulence in the cooling passage 7 and therefore the rate of heat transfer to the cooling fluid. Alternatively or additionally, the protrusion 17 can be arranged to protrude between two radially adjacent winding bars or hairpins 5 (as shown). By separating two adjacent winding bars or hairpins 5 to form a cooling passage 7, 19 between them, the cooling passage 7, 19 thus has a serpentine shape as shown in FIG. 4b). The protrusion 17 and thus the cooling passage 19 are preferably arranged between the radially inner winding 5 and the radially adjacent winding 5, which has been found to be the most efficient way to transfer heat from the stator winding. However, it may additionally or alternatively be advantageous to provide a protrusion 17 between two radially adjacent windings 5 ​​of different phases in order to improve the insulation between the conductors of different phases.

[0033] The stator 2 in the embodiment of FIG. 3 additionally has a number of openings 10 in the laminations 8, which are spaced apart from the stator slots 14 that house the windings 5. Although the openings 10 are shown to be radially located near the slot ends, the openings 10 may be radially located anywhere in the stator laminations, for example near the stator outer surface. There may be such openings 10 located at several different radial locations in the stator 2 and spaced apart from the stator slots 14. In this way, heat can be transferred more uniformly from the lamination stack 13, which relieves thermal stresses in the lamination stack 13. These openings 10, together with openings 10 in adjacent laminations 8 of the stack, form cooling passages 20 that extend in the longitudinal direction 6. When the laminations 8 with these openings 10 are arranged in a package with alternating flipped and non-flipped orientations of the laminations 8, a cooling passage 20 having a serpentine shape can be realized as shown in FIG. 4c). In this case, the asymmetry of the openings 10 is constituted by the asymmetric position of the openings 10 with respect to a radial line 21 which is in the same position in each of the laminations 8, which are aligned in both the inverted and non-inverted laminations in the lamination stack 13, and the serpentine cooling passages 20 are preferably positioned circumferentially between the slots 14.

[0034] The stator 3 in the embodiment of Figure 3 additionally has openings 10 in the laminations 8 at the outer periphery of the laminations 8 which in turn together with the openings 10 of adjacent laminations 8 form cooling passages 22 extending in the longitudinal direction 6. The openings 10 are again formed asymmetrically about a radial line 23 at the same position in each of the laminations 8, with the openings 10 being aligned in both the inverted and non-inverted laminations in the lamination stack 13. The cooling passages 22 may be closed radially outwardly by a sleeve or housing portion 24.

[0035] Although the cooling passages 10 have been described above with respect to the stator 2, it is also possible to provide a rotor with such cooling passages 7.

[0036] In all of the embodiments of Figures 2 and 3, the cooling passage 7 with a serpentine path is formed by alternating packages 11, 12 of stacks of substantially the same shape, with the orientation of these stacks in adjacent packages being inverted and non-inverted.

[0037] Alternatively, the serpentine cooling passage 7 is defined by alternating packages 11, 12 of laminations of substantially the same shape, with the orientation of the laminations in adjacent packages being rotationally offset.

[0038] In FIG. 5b, an embodiment is shown in which several steel laminations 8,9 are rotationally offset in the circumferential direction relative to the other steel laminations 8,9. In this case, two adjacent openings 10a,10b in each of the steel laminations 8,9 have different shapes, which can be seen more clearly in FIG. 5a, where only one of the laminations 8 is shown. If one of the laminations 8 is then rotated, in this case by 20 degrees, relative to the adjacent lamination 9, the two openings 10a,10b align to form a part of one cooling passage 7. It can be seen in the illustrated embodiment that the protrusions 15a and 15b extend into the same cooling passage 7 on different sides of the cooling passage 7 in pairs of adjacent laminations 8,9. When the alternate orientations of the laminations 8,9 are assembled into the stack 13, a serpentine cooling passage is formed. The protrusions can be radial or circumferential as shown in FIG. 5.

[0039] In another embodiment (not shown), the thickness or number of laminations 8 in each package may differ along the longitudinal direction 6 of the lamination stack 13. Thus, the cooling performance can be varied along the axial length of the stack, for example improving cooling on the side of the lamination where the preheated cooling medium exits the cooling passage. In this case, the number of laminations in a package 11, 12 is less than the number of laminations in the adjacent package 11, 12 forming the upstream part of the cooling passage 7. [Explanation of symbols]

[0040] 1 Electrical machinery 2 Stator 3 Rotor 4 Center axis 5 Windings 6 Longitudinal 7 Cooling passage 8 Stator Laminations 9 Rotor Laminations 10 Opening 11 Packages 12 Inverted Package 13 Laminate Stack 14 Slots 15 Protrusion 16 Protrusion 17 Protrusion 18 Internal cooling passage 19 Cooling passage 20 Cooling passage 21 Radial line 22 Cooling passage 23 Radial line 24 Sleeve

Claims

1. 1. An electric machine (1) having a stator (2) and a rotor (3), wherein the stator (2) and / or the rotor has a steel lamination stack (13) made of substantially identical steel laminations (8, 9) having a plurality of openings (10), the steel laminations (8, 9) defining a plurality of fluid cooling passages (7, 18, 19, 20, 22) extending axially through the stack when stacked one on top of another, the steel laminations (8, 9) having different orientations in the stack (13) relative to other steel laminations (8, 9) in the stack (13), whereby the fluid cooling passages (7, 18, 19, 20, 22) define serpentine cooling paths extending axially through the stack (13).

2. 2. The electric machine of claim 1, wherein the steel laminations (8, 9) each have a protrusion (15, 16, 17) that extends into the fluid cooling passage (7, 18, 19, 20, 22), and the protrusions (15, 16, 17) of at least one pair of adjacent steel laminations (8, 9) are positioned on opposite sides of the fluid cooling passage (7, 18, 19, 20, 22).

3. 3. An electric machine according to claim 2, wherein the protrusions (15, 16, 17) extend circumferentially into the fluid cooling passages (7, 18, 19).

4. 3. An electric machine according to claim 2, wherein the protrusions (15, 16, 17) extend radially into the fluid cooling passages (7, 18, 19) from either a radially inner side or a radially outer side of the fluid cooling passages (7, 18, 19).

5. 3. An electric machine according to claim 1 or 2, wherein the different orientations are configured such that some of the steel laminations (8, 9) are rotationally offset in the circumferential direction relative to other steel laminations (8, 9).

6. 3. An electric machine according to claim 1, wherein two adjacent openings (10a, 10b) in each of the steel laminations (8, 9) have different shapes, and wherein fluid cooling passages (7, 18, 19, 20, 22) are formed in the stack (13) by alternately using both of the two adjacent openings (10) of different shapes in each steel lamination (8, 9), thereby forming a serpentine cooling passage extending axially through the stack (13).

7. 3. The electric machine of claim 1, wherein the different orientations are achieved by arranging the steel laminations (8, 9) in the stack (13) in the inverted and non-inverted orientations, and the openings in the same steel laminations (8, 9) are formed asymmetrically, whereby the fluid cooling passages (7, 18, 19, 20, 22) form serpentine cooling paths extending axially through the stack (13).

8. 8. The electric machine of claim 7, wherein the steel lamination stack (13) is formed from a plurality of packages (11, 12), in each of which the steel laminations (8, 9) have the same orientation, and when assembled into the stack (13), alternate packages (11, 12) have a first orientation and a second different orientation, respectively.

9. 9. An electric machine according to claim 8, wherein each package (11, 12) comprises at least 10 steel laminations.

10. 9. An electric machine according to claim 8, wherein the number of laminations (8, 9) in each package (11, 12) varies along the axial length of the stack.

11. 11. The electric machine of claim 10, wherein the number of laminations (8, 9) in one package (11, 12) is less than the number of laminations in an adjacent package forming an upstream portion of the cooling passage (7, 18, 19, 20, 22).

12. 3. An electric machine according to claim 1, wherein the stator and / or the rotor are provided with a plurality of circumferentially spaced slots extending in the axial and radial directions, each slot housing a winding extending axially therethrough, and each slot also housing at least one of the plurality of fluid cooling passages.

13. 13. The electric machine of claim 12, wherein the windings (5) are in the form of conductor bars or hairpins, and at least one protrusion is arranged to radially separate two adjacent conductor bars or hairpins.

14. 13. An electric machine according to claim 12, wherein the protrusion (17) is arranged between the radially innermost conductor bar or hairpin (5) and an adjacent conductor bar or hairpin (5).

15. The electric machine of claim 12, wherein one of the plurality of fluid cooling passages (18) is disposed in a stator slot (14) radially inward of the windings (5).

16. 13. The electric machine of claim 12, wherein the stator slots (14) are closed radially inward in the direction of the rotor (3).

17. 3. An electric machine according to claim 1, wherein one of the plurality of fluid cooling passages (7, 20) is arranged in the steel lamination stack (13) spaced apart from a respective rotor or stator slot that houses a winding (5) and spaced apart from a radially outer surface of the steel lamination stack (13).

18. The electric machine of claim 1 or 2, wherein one of the plurality of fluid cooling passages (22) is disposed on an outer surface of the lamination stack (13).

19. 2. A method of assembling an electric machine according to claim 1, the method comprising the step of rotating or inverting a plurality of the steel laminations (8, 9) relative to one another before or during assembly of the stack (13).

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