Filling a groove with a two-component duromer system in an electric machine

Abstract

A groove closure (12) of a winding groove (1) of an electric machine is to be efficiently produced. For this purpose, a first component of a two-component duromer system is provided, magnetizable particles being added to the first component, and a second component of the two-component duromer system is provided, magnetizable particles being likewise added to the second component. The two components are mixed and are introduced into the groove (1) of the electric machine, where the components are cured.

Description

[0001] Description

[0002] Groove filling using a two-component duromer system for electrical machines

[0003] The present invention relates to a method for filling a slot of an electrical machine. Furthermore, the present invention relates to a corresponding device for filling such a slot.

[0004] Low-voltage motors are typically manufactured with a round wire winding, which is wound into coils in advance using a flyer / stencil winder and then drawn fully automatically into the laminated core with the respective slots. The critical point here is always the slot gap, which is defined by the two adjacent slot teeth. This is significantly smaller than the slot itself, which ideally closes the magnetic circuits more effectively, but the entire copper winding has to be drawn through this cross-sectional taper. In order to generate ideal magnetic field properties in the laminated core, the slot gap would have to be chosen to be so narrow that the slot gap width is smaller than the diameter of a single wire in the winding. However, this would lead to major problems in production, as typical winding drawing-in processes can no longer be used.Current sheet geometries represent a compromise that accommodates both requirements. The slot gap has approximately the inside width of two to four individual wires (diameter), whereby a suitable lamination guide partially compresses the copper bundle to this width during insertion, while the disadvantage regarding the magnetic circuit dimensioning remains acceptable.

[0005] Particularly in larger machines (medium-voltage or high-voltage motors) with higher requirements, the existing slot gap is subsequently closed using a magnetic slot seal. This consists of magnetic iron particles of various types, which are usually combined with a plastic compound. This compound (filler particles = iron, matrix = plastic) is often prefabricated and used as slot wedges, which are mechanically inserted. This has the disadvantage that the slot seal can become loose and come off during operation of the machine due to vibrations and forces occurring, thus blocking the rotor and leading to machine failure.

[0006] On the other hand, prefabricated slot gaps are not an economical solution for a product portfolio with a wide variety of variants, as is often the case in the area of ​​low-voltage motors.

[0007] Another application for medium- and high-voltage machines involves the use of an uncrosslinked, highly filled paste consisting of iron filler particles and a chemically reactive resin (mixing ratio of approximately 90% by weight iron filler to 10% by weight polymer matrix). The compound must be kneaded for several hours under active cooling to ensure homogenization of the particles in the matrix. It must then be stored and transported in a cooled environment, as it is a single-component, reactive compound. The matrix component, for example, is an anhydrite-cured epoxy resin, which cures when exposed to elevated temperatures (150°C for several hours) to form a molded material with sufficient mechanical strength and a glass transition temperature of over 140°C, thus meeting the requirements of medium- and high-voltage machines for the insulation system and peripherals.Due to the choice of matrix and iron filler composition, as well as the high mechanical demands on the final molding material and during application, additional additives such as talc (as a lubricant) and polymer fibers (as reinforcement of the mass and thixotropy during processing) are necessary in single-digit weight percentages. The material is applied at room temperature either manually ("spackled in") or by a (semi-)automated bead application followed by pressing in using a special squeegee. Thermal curing is subsequently achieved using a hot-air oven or by applying current to the windings.

[0008] The object of the present invention is to propose an economical and low-energy possibility for slot filling, particularly in low-voltage machines.

[0009] According to the invention, this object is achieved by a method and a device according to the independent claims. Advantageous developments of the invention emerge from the subclaims.

[0010] The invention is based on the finding that low-voltage motors with high efficiency have only very low power losses, which manifest themselves in heating of the rotor and stator, whereby a temperature of over 100 ° C is almost impossible, particularly in the area of ​​a possible slot closure. This allows a new perspective on the thermal stability of the insulation system and its periphery. In particular, the periphery (e.g. the cover slide) can be well below the thermal class F / H (155 ° / 180 ° C, 20,000 h) otherwise required for the primary insulation system, without negatively affecting the service life or performance of the machine.

[0011] Based on this development, the invention presents an alternative polymer solution for the slot filling, which is an economical and at the same time CCt-friendly solution (with regard to application and process), especially for low-voltage motors.

[0012] According to the invention, a method is provided for filling a slot of an electrical machine. The slot is, in particular, a winding slot into which a winding or coil can be drawn. The slot typically results in a laminated core of a magnetically active part of the electrical machine, e.g., a stator or rotor of a dynamoelectric machine. The electrical machine can be, for example, a motor, a generator, a transformer, and the like.

[0013] The process involves providing a first component of a two-component duromer system, magnetizable particles being mixed into the first component. For example, the two-component duromer system is an epoxy resin-hardener system which, after curing, produces a corresponding duromer. The first component on its own (e.g. epoxy resin) is not reactive, so that its monomers alone do not crosslink. The first component is generally more or less viscous. Magnetizable particles are mixed into the first component. The magnetizable particles can be ferromagnetic particles. The magnetizable particles should be mixed into the first component as homogeneously as possible.

[0014] In a further step of the process according to the invention, a second component of the two-component duromer system is provided, magnetizable particles also being mixed into the second component. The second component is, for example, the hardener of the above-mentioned epoxy resin hardener system. The second component is also not reactive in itself with regard to polymerization. As mentioned, magnetizable particles are also mixed into the second component. Mixing the magnetizable particles into both the first component and the second component has the advantage that the two components, including the magnetizable particles, can be mixed more reliably and easily than three individual components (two pure duromer components and the magnetizable particles as the third component).The magnetizable particles can be of the same type in both components ( e . g . iron powder ) .

[0015] In a further step of the process according to the invention, the first component is mixed with the second component. The two individually non-reactive components are mixed, whereby they react with each other and cause polymerization. For example, the second component, acting as a hardener or catalyst, causes the crosslinking of the first component.

[0016] In a further process step, the mixed components are introduced into the slot of the electrical machine. The two components can be mixed simultaneously with their introduction into the slot or immediately before. The mixed components typically represent a viscous mass that can be introduced into the slot as a strand or bead.

[0017] Finally, in a final step of the process, the mixed components are allowed to cure in the groove to form a thermoset containing the magnetizable particles. Typically, it is sufficient for the two components to react with each other in the groove, causing them to cure to form the desired thermoset. The magnetizable particles are embedded in the thermoset matrix.

[0018] Through the advantageous use of two components, into each of which the magnetizable particles are mixed in advance, the mixing process immediately before application into the groove can be simplified and nevertheless a duromer can be achieved in whose matrix the magnetizable particles are distributed very homogeneously.

[0019] In one embodiment, the first component of the two-component thermoset system is a natural resin, an epoxy resin, or a component of a two-component adhesive. In addition to the natural resin, an epoxy resin can also be used as a synthetic resin for the thermoset or the slot seal. Alternatively, other adhesives that are not based on resins can also be used for the thermoset matrix. Thus, a broad spectrum of thermosets is available for the invention.

[0020] In an alternative embodiment, the first component of the two-component thermoset system is based on isocyanates. Isocyanates are the essential components of polyurethanes (PU products) such as PU paints, PU coatings, PU foams, and PU adhesives.

[0021] In a particularly preferred embodiment, the hardener comprises an amine. Amines are organic compounds that are derivatives of ammonia and in which one, two, or all three hydrogen atoms of the ammonia are replaced by alkyl groups or aryl groups or have combined to form more or less different heterocyclic ring systems. Amine can be used particularly advantageously as a hardener for epoxy resins. Such epoxy-amine systems can, if desired, cure at room temperature.

[0022] In a further embodiment, the magnetizable particles are mixed into both the first and second components at a weight ratio of at least 50 percent, in particular 75 to 90 percent. To achieve a high-quality slot seal, at least 50 percent by weight of magnetizable particles should be mixed into the duromer matrix. However, it is particularly advantageous if the fill level of the magnetizable particles in the duromer matrix is ​​75 to 90 percent by weight.

[0023] In a specific example, the magnetizable particles come from an iron powder, i.e., each magnetizable particle is an iron grain. However, other ferromagnetic materials are also suitable as magnetizable particles.

[0024] In a further embodiment, the first and second components are mixed in a ratio range of 1.2:1 to 1:0.8, and in particular in a ratio of 1:1. Mixing the two components in almost identical ratios has the advantage that the two components can be mixed more easily and evenly. In particular, the fill level of the magnetizable particles in both components should be the same. Overall, this allows for a very homogeneous mix.

[0025] In a further embodiment, the mixed components are introduced into the groove of the electrical machine using a paste dosing system. A conventional paste dosing system can be used for this introduction, thereby increasing the cost-effectiveness of the entire process. The paste dosing system can be a dispenser designed for high-viscosity pastes.

[0026] In another embodiment, the curing of the thermoset emulsion occurs (mostly) at room temperature. In this case, no heating or additional energy is required for curing, which in turn provides efficiency benefits for the process. Any heat of reaction is not considered here.

[0027] In one embodiment, it can be provided that, after curing, a thermosetting molding material with a glass transition temperature of over 60°C is created. Preferably, a glass transition temperature between 60°C and 100°C is achieved. This means that the thermosetting molding material or the duromer also remains hard up to 60°C and can thus reliably fulfill the slot closure function. Only at higher temperatures, which are never reached in very efficient low-voltage motors, would the slot closure become plastic.

[0028] In a further embodiment of the method according to the invention, when the viscous component mixture is introduced into the groove of the electrical machine, a viscous strand from the mixture mass is applied to a wire bundle in the groove. The viscous strand is a so-called pasty "bead". In the applied state, such a bead generally has a cross-section shaped like a segment of a circle and extends elongatedly in the direction of application. It can be advantageously applied using a nozzle. The bead is usually applied to a cover slide, which typically closes off a wire bundle in the groove at the top. Thus, the bead is generally not applied directly to the wire bundle, but indirectly.

[0029] In another embodiment, the wire bundle is pressed toward the groove base immediately before applying the viscous strand. The winding inserted into the groove, i.e., the wire bundle there, can generally be compressed. In doing so, the cover slide or the uppermost wire layer is pressed downward toward the groove base. This creates more space for applying the viscous duromer strand.

[0030] In a further development, the wire bundle can relax in the slot after the viscous strand / bead has been applied, with part of the strand / bead being pressed behind a groove projection on the slot to form a positive fit. This is particularly the case when the viscous strand is wider than the clear opening of the slot. In this case, the parts of the strand projecting beyond the slot opening are pressed against the groove projection when the wire bundle relaxes, creating an undercut in the slot gap. This undercut ensures advantageous fixing of the duromer in the slot gap by means of a positive fit. Furthermore, it can be provided that the viscous strand is pulled off flush with the surface after it has been introduced into the slot. This pulling off can ensure that the surface of the magnetically active element of the electrical machine remains flat and the duromer does not protrude beyond the slot gap.This allows, for example, the air gap between the rotor and stator to be kept very small. The excess material from the viscous strand can be removed, for example, using the nozzle of a dispenser and / or a separate tool.

[0031] The above object is also achieved according to the invention by a device for filling a groove of an electrical machine, the device comprising:

[0032] - a mixing device for mixing a first component of a two-component thermoset system, wherein magnetizable particles are mixed into the first component, and a second component of the two-component thermoset system, wherein magnetizable particles are mixed into the second component, and

[0033] - an application device for introducing the mixed components into the groove of the electrical machine.

[0034] The mixing device can have a first screw extruder for conveying the first component, a second screw extruder for conveying the second component, and a mixer for mixing the first component from the first screw extruder with the second component from the second screw extruder. Optionally, a third screw extruder, which can also be part of the application device, is provided at the outlet of the mixer. Alternatively, the mixing device has, at least instead of the first and second screw extruders, a static mixing tube for mixing both components.

[0035] The mixer can be located upstream of the application device. In this case, mixing occurs immediately before the mixed component is introduced or applied into the groove. Alternatively, the mixer can be integrated into the application device, so that mixing occurs during the introduction into the groove.

[0036] The advantages and variants described above in connection with the method according to the invention also apply mutatis mutandis to the device according to the invention. The individual method features can be viewed as functional features of the device.

[0037] For use cases or application situations that may arise during the method and which are not explicitly described here, it may be provided that, in accordance with the method, an error message and / or a request to enter user feedback is issued and / or a standard setting and / or a predetermined initial state is set.

[0038] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

[0039] The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

[0040] FIG 1 a slot of an electrical machine filled with a wire bundle;

[0041] FIG 2 the groove of FIG 1 with pressed-in wire bundle;

[0042] FIG 3 the groove with applied groove sealing compound;

[0043] FIG 4 the groove with closed groove slot;

[0044] FIG 5 the application of the slot sealing compound in the longitudinal direction of the slot; and

[0045] FIG 6 shows another example of how to apply the slot sealing compound.

[0046] The exemplary embodiments described below represent preferred embodiments of the present invention. The fact that low-voltage motors, in particular, can be operated very efficiently and the slot seal rarely reaches temperatures above 100°C is exploited to produce the slot seal using a duromer emulsion, into which, in addition to the magnetizable particles, the hardener is mixed or kneaded in the form of solid particles into the duromer matrix.

[0047] In a specific embodiment, the polymer matrix is ​​replaced with a material that deviates from the state of the art, regardless of the composition and, if necessary, optimization of the particle size distribution of the iron filler. Due to the significantly smaller groove gap (approximately 2 to 5 mm compared to larger machines with approximately 2 cm), the addition of polymer fibers to the reinforcement is not necessary. Regardless of other features, at least one embodiment should therefore be based on the fact that the thermoset emulsion (mixture of viscous thermoset components) does not contain any polymer fibers.

[0048] The application of the thermoset emulsion can thus be carried out via a conventional paste dosing system, since no "high-shear / high-viscosity" component is added to the paste (ie, thermoset emulsion), which has traditionally made fully automated conveying and application very difficult.

[0049] According to the invention, a two-component duromer system (e.g. epoxy resin system) is used to fill a (winding) slot of an electrical machine, which in this specific case can consist of an epoxy (A) component and an amine (B) component. Alternatively, a PU (isocyanate) system could also be used if necessary. These systems are known to be able to cure completely at room temperature and thus form a molding material that cures without the addition of thermal energy. A stoichiometry of 1:1 (or close to this ratio, e.g. 1:0.8) is advantageous in order to ensure suitable miscibility of the components. Both components are each highly filled separately with the appropriate (iron) filler. A fill level of 50 percent or 75 percent by weight, or even better, 85 - 90 percent by weight, is desirable.

[0050] The two components, each highly filled with iron filler, are typically present as two non-reactive pastes. The conveying and mixing of highly filled pastes can be achieved during application using a static mixing tube at a suitable mixing ratio (1:1 or similar).

[0051] The application can therefore be carried out by placing a bead

[0052] (= compound paste ) into the slot of the electrical machine. As explained below with reference to FIGS. 1 to 4, the bead can be used to achieve a positive slot closure, which, for example, lies on a cover slide and, if necessary, terminates radially inward with the inner radius of the laminated core (in the case of an external stator).

[0053] Furthermore, the slot closure 12 forms a magnetic path of comparatively low reluctance across the slot gap 4, which reduces losses and thus improves the efficiency of the dynamoelectric machine. In addition, noise generation is reduced and torque ripple is suppressed.

[0054] 1 to 4 show a slot 1 which is formed in a laminated core 2. The slot 1 has a slot base 3 which, for example, is formed radially on the outside in the case of an external stator. Opposite the slot base 3 there is a slot gap 4 (radially on the inside in the case of an external stator). The slot gap 4 is located in the circumferential direction between one or two slot projections 5. In the case of a dynamoelectric machine with an external stator and an internal rotor, the slot gap 4 faces the latter. The stator and rotor are separated from one another by an air gap, via which they interact electromagnetically when the dynamoelectric machine is in operation. A wire bundle 6 of a winding of the electrical machine is located in the slot 1. The wire bundle 6 was inserted into the slot 1 through the slot gap 4. A cover slide 7 , which extends in the longitudinal direction of the groove and forms a positive connection with the groove projections 5 , prevents the wire bundle 6 from escaping from the groove 1 .In the state of FIG 1, the cover slide 7 rests against the groove projections 5 through the wire bundle 6.

[0055] FIG. 5 shows the groove 1 in longitudinal section. A point in the cross-section of FIG. 1 before application of the bead / thermosetting emulsion is designated I in FIG. 5.

[0056] FIG 2 shows a cross section through the groove 1 at the point

[0057] II of FIG. 5. Specifically, at this point, the cover slide 7 and the underlying wire bundle 6 are pressed toward the groove base by a pressure roller 8 or another suitable tool, thereby compressing them. It can also be seen from FIG. 5 that at cross-sectional point II, the cover slide 7 is pressed deeper into the groove 1.

[0058] Immediately following the pressure roller 8, the duromer emulsion mixed from the components filled with magnetizable particles is applied as a strand or bead 10 onto the wire bundle 6 or the cover slide 7 using an application device 9, which FIG. 3 shows at the cross-sectional point

[0059] III shows . At this cross-sectional point III, the wire bundle 6 or the cover slide 7 is still in the compressed state by the pressure roller 8, which also shows the low position of the cover slide 7 at the cross-sectional point III of FIG 5 .

[0060] The bead 10 can have a circular segment-shaped cross-section. Preferably, it is somewhat wider than the slot gap 4. This has the advantage that undercuts 11 can be formed by parts of the bead 10, i.e., the slot closure compound, which protrude behind the slot projections 5 when the wire bundle 6 relaxes again as shown in FIG. 4 and presses the cover slide 7 toward the slot gap 4. The plastic bead 10 thereby fills the slot gap 4, resulting in the slot closure 12 shown in FIG. 4, which has a T-shaped cross-section with the undercuts 11.

[0061] An enlarged section of the groove closure 12 is also shown in FIG. 4. It shows how, in particular, the undercut 11 of the groove closure 12 protrudes below the groove projection 5, thus forming a positive connection. If necessary, the bead 10 is removed from the upper side 13 of the groove 1 so that the groove closure 12 is flush with the upper side 12. The application device 9 or a separate tool can be used for removal.

[0062] FIG. 6 shows an alternative embodiment to the application of FIG. 5. Essentially, reference can be made to the description of FIG. 5. Here, too, an epoxy resin is used as the matrix or first component, and a hardener (e.g., amine) is used as the second component.

[0063] The application device 9 here comprises a first extruder 14, a second extruder 15, a third extruder 16, and a mixer 17. One or more of these extruders can be screw extruders. In particular, they should be screw extruders for high-viscosity pastes.

[0064] The first extruder 14 feeds the first component (e.g., epoxy resin mixed with iron powder) into the mixer 17. The second extruder 15 feeds the second component (e.g., hardener mixed with iron powder) into the mixer 17. The mixer 17 mixes both components. At the outlet of the mixer 17 is the third extruder 16, which feeds the mixed components to the groove 1, where it is extruded as a bead 10.

[0065] The mixer 17 can be a kneader, which should be particularly suitable for high-viscosity pastes. The extruders 14, 15, and 16 should be designed so that no separation of liquid and solid components occurs, or such separation is largely avoided.

[0066] To avoid cleaning the mixer 17 and the extruders 14, 16, a static mixing tube can be used as an alternative application device. Care must be taken to ensure a suitable stoichiometry of the individual components.

[0067] Due to the high filling of the paste, e.g., with iron powder, it initially remains dimensionally stable in the grooves and hardens. Hardening occurs automatically, essentially at room temperature, to form a molding material with a glass transition temperature of, e.g., 60 to 100 °C (the insulating resin used can be in the same range).

[0068] As the above examples show, a fully automated application of the slot closure and a CCp-efficient, time and energy-uncritical hardening is possible.

[0069] Advantageously, a high overall fill level of the groove seal, for example, 75 to 90 percent by weight, can be achieved by separately filling the individual components. A two-component reactive resin system that can be applied and cured at room temperature has proven particularly advantageous.

[0070] Another advantage is that no fiber reinforcement is required in the duromer emulsion, allowing for fully automated application. The potentially low glass transition temperature is perfectly acceptable for highly efficient low-voltage motors.

Claims

Patent claims 1 . Method for filling a slot ( 1 ) of a stator of an electrical machine provided with a wire bundle ( 6 ), characterized by - Providing a first component of a two-component thermoset system, wherein magnetizable particles are mixed into the first component, - Providing a second component of the two-component thermoset system, wherein magnetizable particles are mixed into the second component, - Mixing the first component with the second component, - Inserting the mixed components into the groove ( 1 ) of the electrical machine and - Allowing the mixed components to harden in the groove ( 1 ) to form a duromer provided with the magnetizable particles.

2. The method according to claim 1, wherein the first component of the two-component thermoset system is a natural resin, an epoxy resin or a component of a two-component adhesive.

3. The method according to claim 1, wherein the first component of the two-component thermoset system is formed on an isocyanate basis.

4. The process according to claim 1 or 2, wherein the second component comprises an amine.

5. A method according to any one of the preceding claims, wherein the magnetizable particles are mixed into both the first and the second component in an amount of at least 50 percent by weight, in particular 75 to 90 percent by weight.

6. A method according to any one of the preceding claims, wherein the magnetizable particles originate from an iron powder.

7. A method according to any one of the preceding claims, wherein the first and second components are mixed in a ratio range of 1.2:1 to 1:0.8 and in particular in the ratio 1:

1.

8. Method according to one of the preceding claims, wherein the introduction of the mixed components into the groove (1) of the electrical machine is carried out with the aid of a paste dosing system.

9. A method according to any one of the preceding claims, wherein the curing of the mixed components takes place largely at room temperature.

10. Method according to one of the preceding claims, wherein during the introduction of the viscous duromer emulsion into the groove (1) of the electrical machine, a viscous strand (10) of the mixed components is applied to a wire bundle (6) in the groove (1).

11. The method according to claim 10, wherein the wire bundle (6) is pressed in the direction of the groove base (3) immediately before the application of the viscous strand (10).

12. The method according to claim 11, wherein after the application of the viscous strand (10) the wire bundle (6) relaxes in the groove (1) and in the process a part of the strand (10) is pressed behind a groove projection (5) on the groove (1) to form a positive connection.

13. Method according to one of the preceding claims, wherein the viscous strand (10) is drawn off flush with the surface after being introduced into the groove (1).

14. Device for filling a slot (1) of a stator of an electrical machine provided with a wire bundle (6), characterized by - a mixing device for mixing a first component of a two-component thermoset system, wherein magnetizable particles are mixed into the first component, and a second component of the two-component thermoset system, wherein magnetizable particles are mixed into the second component, and - an application device for introducing the mixed components into the groove ( 1 ) of the electrical machine. 15 . Device according to claim 14 , wherein the mixing device either - a first screw extruder ( 14 ) for conveying the first component, - a second screw extruder ( 15 ) for conveying the second component and - a mixer ( 17 ) for mixing the first component from the first screw extruder ( 14 ) with the second component from the second screw extruder ( 15 ) , or - has a static mixing tube for mixing both components.

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