Method for producing a rotor, rotor, and electric machine

Abstract

The invention relates to a method for producing a rotor (1) for an electric machine (2), said method having the steps of - providing a laminated core (3) composed of individual sheets and having slots (6), between which poles (7) with pole cores (8) and pole shoes (9) are provided, - providing rotor windings (10) on the pole cores (8), - providing slot closure wedges (11) with two flanks (12) and a web (13) connecting said flanks, a recess (15) being provided at the transition (14) between a flank (12) and the web (13), - inserting each slot closure wedge (11) into a respective slot (6) in such a way that the two flanks (12) of the slot closure wedge rest against an associated rotor winding (10) and the web (13) of the slot closure wedge rests inwardly against two adjacent pole shoes (9), and - introducing a viscous or liquid and coolable or curable casting compound (18) into the recesses (15), in particular under pressure, such that - the casting compound (18) cools or cures and, in the cooled or cured state, secures the slot closure wedge (11) and seals off the slot closure wedge (11) at least from the pole shoe (9).

Description

[0001] Method for manufacturing a rotor, rotor and electric machine

[0002] The present invention relates to a method for manufacturing a rotor for an electric machine. The invention also relates to a rotor manufactured according to this method and to an electric machine comprising such a rotor.

[0003] To avoid the drag losses caused by oil in an air gap that occur in so-called "wet rotors," "dry rotors" are sealed. This can be achieved by allowing the cooling medium to flow only through individual sealed channels in the rotor or a slotted sealing wedge. If the rotor's interior is to be flooded with cooling medium, for example, to directly circulate around the rotor windings, the entire rotor must be sealed to the outside. Furthermore, various fastening techniques are known for the slotted sealing wedge and the underlying rotor winding on the lamination stack, for example, using spring preload or hydrostatic pressure.

[0004] From DE 192 160 8 U1 a magnetic slot closure wedge is known which is made of a laminated material and contains a magnetically effective steel wool fleece provided between insulating layers, wherein the individual layers are baked together by synthetic resin.

[0005] From DE 20 60 361 A1, a slot closure wedge made of glass fiber reinforced plastic for electrical machines is known, wherein within the slot closure wedge, near the surface of the slot closure wedge facing a conductor bar or a rotor winding coil, a cavity is provided which runs approximately parallel to the lower surface in the longitudinal direction and extends approximately over the entire width of the slot closure wedge, and which is filled with a curable casting resin after insertion into the slot. This is intended, in particular, to prevent shrinkage of slot closure wedges, which can lead to a loose arrangement of the conductor bars in the associated slots.

[0006] From DE 27 42 521 A1, an arrangement for the radial clamping of rotor windings in rotors of electrical machines is known, wherein two adjacent rotor windings are each separated from each other by a slot into which a slot locking wedge and spring elements extending longitudinally through the slot are clamped. The spring elements are arranged at the bottom of the slot and have such a high spring preload that the conductors above them are pressed sufficiently firmly against the slot locking wedge in every operating state and every position. This is also intended to ensure a long-term reliable fixation of the slot locking wedge in the slot and of the rotor windings above it.

[0007] From EP 1 276205 B1 a rotor for an electric machine with at least one pair of poles is known, wherein each pole has a circumference with a depth in the axial direction and a width in the circumferential direction.

[0008] A disadvantage of previously known manufacturing methods for rotors is that fixing and sealing the slot closure wedges in the corresponding slots is comparatively complex and difficult.

[0009] The present invention therefore addresses the problem of providing a method for manufacturing a rotor by which the disadvantages known from the prior art can at least be reduced. This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject matter of the dependent claims.

[0010] The present invention is based on the general concept of pre-tensioning, fixing, and sealing a slot closure wedge in a corresponding slot in a laminated core of a rotor by means of a subsequently injected (under pressure) plastic or potting compound, wherein the sealing effect occurs after the plastic or potting compound has cooled and hardened. In the inventive method for manufacturing a rotor for an electric machine, a laminated core composed of individual laminations with circumferentially separated and axially extending slots is first provided, with poles with pole cores and pole shoes arranged between the slots. The pole cores of the poles extend essentially radially, while the pole shoes are arranged at the outer free end of the pole cores and serve to fix rotor windings wound around the pole cores.The pole shoes secure the rotor windings, particularly against the centrifugal forces that occur during operation. Rotor windings are then applied to the pole cores of the laminated core, and a magnetic field is generated via these windings during operation. To seal and, in particular, to fix the rotor windings to their respective pole cores, slot-locking wedges are inserted into the corresponding slots. These wedges each have two flanks and a connecting web. For example, an axially extending recess may be provided at the transition from a flank to a web. This recess may also be limited only by the pole shoe and the slot-locking wedge. The slot-locking wedges are thus elongated and have a wedge-shaped cross-section, with the two flanks forming two side surfaces that meet at an acute angle.At an end opposite the acute angle, the two flanks are connected by the bridge or arc. The slot-locking wedge is inserted into the corresponding groove in such a way that each flank of the wedge rests against a corresponding rotor winding, biasing it against a corresponding pole core. Simultaneously, the wedge's inner rib rests against two adjacent pole shoes, so that the wedge is held in place by the pole shoes during rotor operation, i.e., by the centrifugal forces that occur. After the wedge is inserted into the corresponding groove, the recess in the wedge is enclosed, i.e., bounded, by the wedge itself, in particular by a corresponding rotor winding, and a corresponding pole shoe. Subsequently, a material that is initially liquid or viscous and later solidifies is injected into this and all other recesses.A hardening potting compound, especially when injected under pressure, seals the slot locking wedge against the pole shoe and secures it in place once cooled or hardened. By injecting the potting compound, which is still liquid or viscous in its injected state, into the corresponding recesses, the slot locking wedge can be pre-tensioned radially inwards and, due to the wedge action, also circumferentially against the two adjacent rotor windings. Any gap that may occur radially outwards towards the pole shoe of the laminated core is sealed against the core by the hardening potting compound present in the recess.This makes it possible to reliably fix the slot locking wedges in their respective slots by pressing in the potting compound (plastic compound), and, above all, to achieve a reliable seal. This prevents, for example, the cooling medium present in the rotor winding area during internal rotor cooling from escaping into an air gap between the rotor and an external stator, thus preventing drag losses. This not only significantly simplifies rotor manufacturing but also allows the entire rotor to be sealed externally, enabling the use of a dry-running rotor, for example, in a separately excited synchronous machine, which is typically operated with wet-rotor rotors.

[0011] In a further development of the method according to the invention, the laminated core is mounted on a shaft in a rotationally fixed manner. This rotationally fixed mounting can be achieved, for example, by soldering, welding, or bonding, with a positive-locking connection between the shaft and the laminated core being conceivable additionally or alternatively. Such a positive-locking connection can be achieved, for example, by a contour arranged accordingly on the surface of the shaft and a corresponding, complementary counter contour arranged on an inner circumference of the laminated core. With such a contour, and thus also with the counter contour in the axial direction on the shaft, a rotationally fixed mounting of the laminated core on the shaft can be achieved by simply sliding the laminated core onto the shaft in the axial direction.

[0012] In a particularly preferred embodiment of the method according to the invention, a thermosetting molding compound is used as the casting material. Compared to thermoplastic materials, thermosetting molding compounds exhibit significantly better flow properties, thus enabling the filling of smaller cavities over large lengths. Furthermore, they generally exhibit higher thermal and mechanical strengths, which can also be advantageous with regard to subsequent applications.

[0013] The present invention is further based on the general idea of ​​providing a rotor for an electric machine that is manufactured using the method described in the preceding paragraphs. This allows the advantages already described with respect to the method to also be transferred to the rotor manufactured according to this inventive method. Specifically, these advantages lie in a simple and cost-effective manufacturing process in which the slot locking wedges are not fixed, as is customary, by means of, for example, separate spring elements, but rather by means of a casting compound injected under pressure, which cools, hardens, or solidifies, thereby not only fixing the slot locking wedges in their respective slots but also sealing them.By positioning the respective recesses on the slot closure wedge at the transition area between a flank and the web, or solely on the web, the injection of the potting compound can also achieve radial inward clamping of the slot closure wedges, causing their flanks to press against the rotor windings. If this process causes the web to lift away from the inner side of the associated pole shoes, resulting in a gap, the potting compound, injected under pressure, can penetrate this gap and reliably seal it. After hardening, and in particular curing, the slot closure wedge is thus not only sealed but also pre-tensioned and fixed, especially in internally cooled rotors where the rotor windings are directly wetted with the cooling medium.This can prevent, in particular, the escape of cooling medium into a gap between the rotor and a stator, thereby reducing drag losses and increasing efficiency.

[0014] In an advantageous embodiment of the rotor according to the invention, the slot closure wedges are made of an electrically non-conductive material, in particular plastic. It is conceivable that the plastic (encapsulating compound) used for the slot closure wedges is the same plastic as that which is pressed into the recesses and subsequently hardens in the manufacturing process according to the invention. Using identical plastics, differences in thermal expansion or shrinkage tendencies can be avoided. It is also conceivable, of course, that the plastic used for the slot closure wedges is fiber-reinforced in order to withstand the high loads occurring during rotor operation.

[0015] In a further advantageous embodiment of the rotor according to the invention, a cooling channel through which a cooling fluid flows for cooling the rotor windings is arranged in at least one slot locking wedge. This makes it possible to use the slot locking wedge not only for pre-tensioning and fixing the rotor windings, but also as a channel for a cooling medium, thereby increasing the functionality of the slot locking wedge. By providing a cooling channel in the respective slot locking wedges, effective rotor cooling can be achieved, thereby increasing the performance of an electric machine equipped with such a rotor.

[0016] The present invention is based on the general concept of equipping an electric machine with a rotor described in the preceding paragraphs, thereby transferring the advantages described with respect to the rotor, specifically simple and compact manufacturing, to the electric machine. The electric machine can, for example, be designed as a separately excited synchronous machine, which offers the significant advantage that wet-rotor rotors typically used in separately excited synchronous machines can now, for the first time, be easily designed as dry-rotor rotors. This allows, in particular, the drag losses typical of wet-rotor rotors to be avoided, thus increasing their efficiency. Further important features and advantages of the invention will become apparent from the dependent claims, the drawings, and the accompanying description of the figures.

[0017] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0018] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0019] They show, each schematically

[0020] Figure 1 shows different process steps of a method according to the invention for manufacturing a rotor for an electric machine.

[0021] Figure 2 shows a view of a rotor according to the invention,

[0022] Figure 3 shows a detailed view of a rotor according to the invention in the area of ​​the recesses on the slot locking wedge,

[0023] Figure 4 shows a cross-sectional view through the rotor before the potting compound is applied; Figure 5 shows a view similar to Figure 4, but during the application of the potting compound.

[0024] Figure 6 shows a representation as in Figure 5, but without the tooling. According to Figure 1, a method according to the invention for manufacturing a rotor 1 for an electric machine 2 (compare Figures 2 and 3) comprises several process steps A to F. A laminated core 3 composed of individual laminations has grooves 6 separated from one another in the circumferential direction 4 and extending in the axial direction 5. Such a laminated core 3 composed of individual laminations is provided in a process step A.

[0025] Between the slots 6, a pole 7 with a pole core 8 and an externally arranged pole shoe 9 is arranged in the circumferential direction 4. In process step B, a rotor winding 10 is applied to each of the pole cores 8 of the laminated core 3. Insulation can, of course, be applied between the pole 7 and the rotor winding 10 beforehand. Subsequently, in process step C, slot closure wedges 11, each with two flanks 12 and a web 13 connecting the two flanks 12, are provided. The web 13 can, of course, also be curved. The web 13 is thus to be understood merely as an external connection between the two flanks 12. At a transition 14 from a flank 12 to the web 13, the slot closure wedges 11 each have a recess 15 extending in the axial direction 5.

[0026] It is clear that such a recess 15 does not necessarily have to be located at the transition 14, but can also be located in such a way that it is only limited by the slot locking wedge 11 and the pole shoe 9, as is shown for the rotor 1 in Figures 4 to 6. In this case, the recess 15 is located on the web 13.

[0027] In a subsequent process step D, a corresponding slot locking wedge 11 is inserted into each slot 6 such that its two flanks 12 bear against a corresponding rotor winding 10 and bias it against the corresponding pole core 8. Simultaneously, the slot locking wedge 11, with its web 13, rests against two adjacent pole shoes 9 on the inside. The slot locking wedge 11 is inserted into the corresponding slot 6 such that the recess 15 is bounded by the slot locking wedge 11, a corresponding rotor winding 10, and a corresponding pole shoe 9, thereby forming a longitudinal channel that runs perpendicular to the plane of the image, as shown in Figure 3.Alternatively, the groove locking wedge 11 can also be inserted into the associated groove 6 in such a way that the recess 15 is limited by the groove locking wedge 11 and an associated pole shoe 9, thereby forming a longitudinal channel which runs perpendicular to the plane of the image according to Figures 4 to 6.

[0028] In the subsequent process step E (see Figure 5), a viscous or liquid, curable or hardening potting compound 18, particularly under pressure, is injected into the recesses 15. In the final process step F, the potting compound cools or hardens, and in its cooled or hardened state, it seals the slot closure wedge 11, primarily against the pole shoe 9 of the respective poles 7, and may also be fixed in place. During the injection of the potting compound 18, the recess 15 is delimited on its outer diameter by a tool 19 (see Figure 5) and on its inner diameter by contact between the slot closure wedge 11 and the pole shoe 9 or the rotor winding 10. After removal of the tool 19, the rotor 1 has an at least approximately circular geometry at its outer diameter (see Figure 6).

[0029] The potting compound 18 can enclose the pole shoes 9 on at least one end face of the rotor 1 and compensate for a length difference between the slot closure wedge 11 and the lamination stack 3, provided that: (Lxeii > Lßiechpaket ). In particular, this allows a manufacturing-related difference in the axial length of the lamination stacks 3 with respect to the length of the slot closure wedges 11 to be compensated for by a potting compound 18 sprayed onto both end faces of the lamination stacks 3. The length always refers to the axial direction of the rotor 1. This creates a sealing surface that is flat on the end face and circumferentially, i.e., stepless, which not only simplifies the sealing of cooling channels running in or on the slot closure wedges 11, but also allows a rotor previously designed as a wet rotor to be designed as a dry rotor, thus avoiding the significant drag losses associated with wet rotors.

[0030] By injecting the initially liquid or viscous potting compound 18 into the recesses 15, the slot locking wedge 11 is pressed radially inwards, thus pressing its flanks 12 against the rotor windings 10. Any gap that may arise between the web 13 of the slot locking wedge 11 and the pole shoe 9 is filled and sealed by the injected potting compound 18. This allows for the relatively simple creation of an internally cooled rotor 1, reliably preventing unwanted leakage of cooling medium to the outside, particularly into an air gap between the rotor 1 and a stator (not shown). This reliably prevents drag losses that occur when cooling medium leaks into the air gap between the rotor 1 and the stator, thereby increasing the efficiency of the electric machine 2.

[0031] For example, a thermoplastic or thermosetting plastic can be used as the potting compound 18, which offers the significant advantage that its properties, such as hardness, temperature resistance, etc., can be defined within relatively wide limits. This allows such a plastic to be optimally adapted to individual requirements.

[0032] The slot locking wedges 11 are made of an electrically non-conductive material, for example plastic, and may also have a cooling channel 16 through which a cooling medium can flow to cool the rotor windings 10. The plastic used for the slot locking wedges 11 can, of course, also be fiber-reinforced.

[0033] The slot locking wedge 11 can also have a channel-shaped recess 17 which, together with the rotor winding 10, defines a cooling channel for a coolant, thus enabling direct contact of the coolant with the rotor winding 10. This allows for particularly effective rotor cooling.

[0034] With the inventive method and the inventive rotor 1 produced according to the method, a comparatively simple and, in particular, reliable fixing and sealing of the rotor 1 in the area of ​​its groove locking wedges 11 can be achieved, in which both the pre-tensioning and the fixing and sealing take place after the curing of the plastic pressed into the recesses 15.

Claims

Claims 1. Method for manufacturing a rotor (1 ) for an electric machine (2), wherein - a laminated core (3) composed of individual sheets with grooves (6) extending in the axial direction (5) is provided, wherein pole teeth (7) with pole cores (8) and pole shoes (9) are arranged between the grooves (6), - rotor windings (10) are applied to the pole cores (8) of the laminated core (3), - Groove locking wedges (11) with two flanks (12) and a web (13) connecting the two flanks (12) are provided, wherein a recess (15) extending in the axial direction (5) is provided, - into each groove (6) a corresponding slot locking wedge (11) is inserted such that its two flanks (12) bear against a corresponding rotor winding (10) and bias this against the corresponding pole core (8), and its web (13) bears against two adjacent pole shoes (9) on the inside, wherein at least one recess (15) is bounded at least by the corresponding slot locking wedge (11) and a corresponding pole shoe (9), - a viscous or liquid and coolable or curable casting compound (18) is introduced into the recesses (15), in particular under pressure, - that the potting compound (18) cools or hardens and, in the cooled or hardened state, fixes the groove locking wedge (11) and seals the groove locking wedge (11) at least against the pole shoe (9).

2. Method according to claim 1, characterized in that the sheet metal stack (3) is mounted on a shaft in a rotationally fixed manner.

3. Method according to claim 1 or 2, characterized in that, - that a thermosetting plastic, in particular an epoxy molding compound, is used as the potting compound (18), or - that a thermoplastic material is used as the potting compound (18).

4. Rotor (1 ) for an electric machine (2), manufactured according to the method of one of the preceding claims.

5. Rotor (1 ) according to claim 4, characterized in that the slot locking wedges (11 ) are made of an electrically non-conductive material, in particular plastic.

6. Rotor (1 ) according to claim 4 or 5, characterized in that a cooling channel (16) through which a cooling liquid can flow for cooling the rotor windings (10) is arranged in at least one slot locking wedge (11 ).

7. Rotor (1 ) according to one of claims 4 to 6, characterized in that the recess (15) is arranged at a transition (14) from a flank (12) to the web (13).

8. Electric machine (2) with a rotor (1) according to one of claims 4 to 10.

7.

9. Electric machine (2) according to claim 8, characterized in that the electric machine (2) is designed as a separately excited synchronous machine.

10. Electric machine (2) according to claim 8 or 9, characterized in that the slot locking wedge (11 ) has a trough-shaped recess (17) which together with the rotor winding (10) defines a cooling channel for a coolant, so that direct contact of the coolant with the rotor winding (10) is possible.

11. Electric machine (2) according to one of claims 8 to 10, characterized in that the potting compound (18) surrounds the pole shoes 9 on at least one end face of the rotor (1 ) and compensates for a length difference of the slot closure wedge (11 ) to the laminated core (3).

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