Filling a groove with duromer in an electric machine

Abstract

A groove closure of a winding groove of an electric machine is to be efficiently produced. For this purpose, a viscous duromer emulsion is provided, the duromer matrix of which is mixed with solid particles as a curing agent and magnetizable particles. The viscous duromer emulsion is introduced into the groove (1) of the electric machine in the form of a bead (10) for example. The viscous duromer emulsion is then heated so that the solid particles melt and react with the duromer matrix. Finally, the heated duromer emulsion is cured.

Description

[0001] Description

[0002] Groove filling using duromer in 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 inserted mechanically. 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 placed on the final molding material and its application, additional additives such as talc (as a lubricant) and polymer fibers (for reinforcement of the mass and thixotropy during processing) are required in single-digit weight percentages. The material is applied at room temperature either manually ("spat 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. The electrical machine can be, for example, a motor, a generator, a transformer, and the like.

[0013] The process involves providing a viscous duromer emulsion into whose duromer matrix solid particles as hardeners and magnetizable particles are mixed. The duromer emulsion is provided as a precursor for a duromer, i.e. a plastic which can no longer be deformed after hardening through heating or other measures. The emulsion is viscous, i.e. thick and runny. The matrix of the duromer emulsion can be referred to as a plastic matrix or duromer matrix. A hardener (second component) is mixed into this duromer matrix (first component). To prevent the two components from reacting with one another right from the start, the hardener is in the form of solid particles. These solid particles are not dissolved in the duromer emulsion and do not yet react with the duromer matrix.

[0014] In addition, magnetizable particles are mixed into the duromer emulsion. These magnetizable particles can be iron powder, for example. However, powders of other ferromagnetic metals or alloys are also conceivable.

[0015] In a further step, the viscous duromer emulsion is introduced into the slot of the electrical machine. The respective winding or coil is usually already in the slot so that the duromer emulsion is applied to the respective wire bundle or the cover slide. The amount of duromer emulsion introduced into the slot should be such that it can ultimately form a suitable slot closure after curing. In a further process step, the viscous duromer emulsion is heated so that the solid particles melt and react with the duromer matrix. The viscous duromer emulsion is therefore preferably heated once to a so-called trigger temperature so that the solid particles not only melt but can also react with the duromer matrix. The heating therefore provides the energy for melting and, if necessary, for reacting.The hardener dissolves in the duromer matrix. The hardener's solid particles should be distributed as homogeneously as possible within the duromer matrix so that the reaction can take place evenly. The reaction results in the hardening of the heated duromer emulsion. The hardened duromer ultimately serves as a groove seal.

[0016] Advantageously, a single, brief heating can trigger a reaction between the two components of the thermoset emulsion (matrix and hardener). Furthermore, the thermoset emulsion can be economically introduced into the respective groove using a conventional dispenser. This results in a highly efficient manufacturing process for the electric machine.

[0017] In one embodiment, the thermoset emulsion comprises a natural resin, an epoxy resin, or an adhesive as the thermoset matrix. In addition to the natural resin, an epoxy resin can also be used as a synthetic resin for the thermoset or the groove 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.

[0018] 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.

[0019] In a further embodiment, 75 to 90 percent by weight of magnetizable particles, particularly iron powder, are mixed into the duromer emulsion. Such high-percentage fillings may require active cooling during kneading to prevent the trigger temperature from being reached. The high weight fraction of the magnetizable particles results in a highly efficient slot closure.

[0020] In a further advantageous embodiment of the process according to the invention, the viscous duromer emulsion is heated just far enough to enable the solid particles to melt and the hardener to react with the duromer matrix. During this heating, an attempt is made to avoid unnecessary heat input. Heating above the trigger temperature should be avoided for reasons of environmental friendliness. If the trigger temperature is 70 °C, for example, the duromer emulsion should be heated to just 70 °C, but not, or only slightly, above it. The amount of energy supplied should therefore only be sufficient to allow the hardener to melt and react with the duromer matrix to occur.

[0021] In a further embodiment, the viscous duromer emulsion is introduced into the groove of the electrical machine using a paste dosing system. Since the hardener and matrix are essentially a one-component emulsion, a conventional paste dosing system can be used for introduction, which can increase the cost-effectiveness of the entire process. The paste dosing system can be a dispenser designed for highly viscous pastes. In a further embodiment, the duromer emulsion cures largely at room temperature. It is therefore preferably sufficient for the duromer emulsion to be briefly raised to the trigger temperature and then cooled essentially to room temperature, whereupon it cures. If necessary, the largest part of the curing takes place at room temperature.In this case, no additional energy is required for curing, which in turn brings efficiency benefits to the process.

[0022] 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, the glass transition temperature is between 60 °C and 100 °C. 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 not even reached in highly efficient low-voltage motors, would the slot closure become plastic.

[0023] In addition, one embodiment can provide for the heating of the viscous duromer emulsion to take place immediately before and / or immediately after the viscous duromer emulsion is introduced into the groove of the electrical machine. For example, the heating can take place directly in the dispenser. In this case, the dispenser has a heating function and triggers the melting and reaction of the hardener before the duromer emulsion is introduced into the groove. Alternatively or additionally, the duromer emulsion can also be heated immediately after it has been introduced into the groove, for example by means of an infrared lamp or by energizing the respective winding. This variant has the advantage that an inexpensive dispenser without a heating function can be used. In contrast, the first variant with the heatable dispenser has the advantage that essentially only the duromer emulsion is heated and not any surrounding parts of the electrical machine.In a further embodiment of the method according to the invention, when the viscous duromer emulsion is introduced into the groove of the electrical machine, a viscous strand of the duromer emulsion 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.

[0024] 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.

[0025] In a further development, the wire bundle can relax in the groove after the application of the viscous strand / bead, with part of the strand / bead being pressed behind a groove projection to form a positive fit. This is particularly the case when the viscous strand is wider than the clear opening of the groove. In this case, the parts of the strand protruding beyond the slot opening are pressed against the groove projection when the wire bundle relaxes, creating an undercut in the groove gap. This undercut ensures advantageous fixation of the duromer in the groove gap through positive locking.

[0026] Furthermore, it can be provided that the viscous strand is removed flush with the surface after being introduced into the slot. This removal ensures that the surface of the magnetically active element of the electrical machine remains flat and that 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 of the viscous strand can be removed, for example, using the nozzle of a dispenser and / or with a separate tool.

[0027] The above object is also achieved according to the invention by a device for filling a slot (winding slot) of an electrical machine, comprising a dispenser for providing a viscous duromer emulsion, in the duromer matrix of which solid particles are mixed as hardeners (not yet reacting) and magnetizable particles (e.g. iron powder), a nozzle on the dispenser for introducing the viscous duromer emulsion into the slot of the electrical machine (as a slot closure), a heating device for heating the viscous duromer emulsion (optionally for a limited space and time) so that the solid particles melt and react with the duromer matrix, whereby the duromer emulsion hardens.

[0028] In particular, the heating device can, if necessary, ensure a localized and / or temporally limited heating of the viscous thermoset emulsion. This can occur, for example, if the thermoset bead is only locally heated at a limited location during the application movement. Due to the movement of the bead or strand, this also results in a temporary heating of the respective part of the bead or strand.

[0029] 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.

[0030] 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.

[0031] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

[0032] The present invention will now be explained in more detail with reference to the accompanying drawings, in which:

[0033] FIG 1 a slot of an electrical machine filled with a wire bundle;

[0034] FIG 2 the groove of FIG 1 with pressed-in wire bundle;

[0035] FIG 3 the groove with applied groove sealing compound;

[0036] FIG 4 the groove with closed groove slot;

[0037] FIG 5 the application of the slot sealing compound in the longitudinal direction of the slot; and

[0038] FIG 6 shows another example of how to apply the slot sealing compound.

[0039] The exemplary embodiments described below represent preferred embodiments of the present invention.

[0040] The fact that low-voltage motors in particular can be operated very efficiently and the slot seal hardly reaches a temperature above 100 ° C is used to produce the slot seal using a duromer emulsion in which, in addition to the magnetizable particles, the hardener is mixed or kneaded into the duromer matrix in the form of solid particles.

[0041] In one specific embodiment, the polymer matrix is ​​replaced by a material deviating from the state of the art, regardless of the composition and, if applicable, optimization of the particle size distribution of the iron filler. Due to the significantly smaller groove gaps (approx. 2 to 5 mm compared to larger machines with approx. 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 duromer emulsion does not contain any polymer fibers. The duromer emulsion can thus be applied using a conventional paste dosing system, since no "high-shear / high-viscosity" component is added to the paste (i.e., duromer emulsion), which has traditionally made fully automated conveying and introduction very difficult.

[0042] According to the invention, a quasi "one-component" resin system is used to fill a (winding) slot of an electrical machine. This resin system has the special property that the second component required for curing is finely dispersed and stabilized as solid particles (e.g. several micrometers in diameter) within the first component. This is possible, for example, with an epoxy-amine system, wherein the amine hardener is non-reactively dispersed as solid particles in the epoxy resin. In this case, only an increase in temperature to 70 ° C leads to melting of the hardener particles, whereby they dissolve with the resin component and form a reactive mixture. The previously very homogeneous dispersion ensures a homogeneous solution.

[0043] The epoxy-amine system or another similar system (e.g. PU-isocyanate system) can be made so reactive by supplying energy or increasing the temperature that it can then cure at room temperature (similar to a mixed 2K system). The product Elan-Glue® EP 5350, for example, can be used as the basis for the duromer emulsion. The special epoxy-amine system can be provided with the necessary filling of magnetizable particles (e.g. iron powder). The magnetizable particles preferably reach a proportion of 75 to 90 percent by weight. If necessary, active cooling must be used when introducing the filler (e.g. kneading) due to friction in order to prevent the trigger temperature from being reached or the hardener component from melting and thus the formation of a reactive mixture.

[0044] When applying the duromer emulsion or paste into the groove of the electrical machine, a conventional single-component delivery device can be used, such as a dispenser for high-viscosity pastes, e.g., from Viskotec. It is advantageous if the dispenser is designed to be heatable, so that the paste is heated above the trigger temperature during application and is then applied as a bead with reduced viscosity.

[0045] Advantageously, further heating of the applied bead is not necessary for curing. Rather, complete curing can be achieved, as described above, after a single heating and melting step, as well as a dissolution of the hardener component, at room temperature, resulting in a thermosetting molding material with a glass transition temperature of, for example, 60 to 100 °C.

[0046] The application can therefore be carried out by placing a bead

[0047] (= 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).

[0048] FIGS. 1 to 4 show a groove 1 formed in a laminated core 2. The groove 1 has a groove base 3, which, for example, is formed radially outward in an external stator. Opposite the groove base 3 (radially inward in the external stator) is a groove gap 4. The groove gap 4 is located in the circumferential direction between one or two groove projections 5.

[0049] 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 slot and forms a positive connection with the slot projections 5, prevents the wire bundle 6 from escaping from the slot 1. In the state shown in FIG. 1, the cover slide 7 rests against the slot projections 5 through the wire bundle 6.

[0050] FIG. 5 shows the groove 1 in longitudinal section. A point in the cross-section of FIG. 1 before application of the bead / duromer emulsion is designated I in FIG. 5.

[0051] FIG. 2 shows a cross-section through the groove 1 at point 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. FIG. 5 also shows that at cross-sectional point II, the cover slide 7 is pressed deeper into the groove 1.

[0052] Immediately adjacent to the pressing roller 8, the duromer emulsion (including plastic or duromer matrix, hardener, and magnetizable particles) is applied as a strand or bead 10 to the wire bundle 6 or the cover slide 7 using a dispenser nozzle 9, as shown in FIG. 3 at cross-sectional point III. At this cross-sectional point III, the wire bundle 6 or the cover slide 7 is still compressed by the pressing roller 8, which also shows the deep position of the cover slide 7 at cross-sectional point III of FIG. 5.

[0053] The bead 10 can have a cross-section in the shape of a circular segment. It is preferably 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 towards 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.

[0054] An enlarged section of the groove closure 12 is also shown in FIG. 4. It shows, in particular, how the undercut 11 of the groove closure 12 projects 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 dispenser nozzle 9 or a separate tool can be used for removal.

[0055] Since the thermoset emulsion, for example, has been heated above the trigger temperature in the dispenser or dispenser nozzle 9, the hardener reacts with the matrix, causing the groove seal 12 to harden and cool. With a suitable matrix-hardener system, no additional energy input is required for curing, so that curing can continue even at room temperature after the bead has cooled.

[0056] 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, for example, is used as the matrix, and a hardener (e.g., amine) is dispersed therein in undissolved form. The encapsulated hardener catalyst is also intended to react with the plastic matrix by briefly increasing the temperature. Instead of the heatable dispenser nozzle 9, a simple, non-heatable dispenser nozzle 9' can be used here, which applies the viscous bead 10 into the groove 1. An additional heating device 14 heats the bead 10 in the already applied state. The heating device 14 can, for example, have an infrared lamp. Alternatively, the heating device 14 can also comprise a winding in the slot 1, which is supplied with current. Under certain circumstances, the dispenser nozzle 9' is also additionally heated.The only important thing is that bead 10 is brought above the trigger temperature so that the hardener melts and can react with the matrix.

[0057] Due to the high filling of the paste, e.g., iron powder, it initially remains dimensionally stable in the grooves and hardens. Curing occurs primarily at room temperature, forming 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).

[0058] As the above examples show, a fully automated application of the slot closure and a CCp-efficient, time and energy-uncritical hardening is possible.

[0059] Advantageously, a high filler content of, for example, 75 to 90 percent by weight can be achieved using a preformed thermoset emulsion. A particularly advantageous solution is the quasi-one-component reactive resin system with an encapsulated hardener (e.g., an epoxy-amine system), which only needs to be heated to approximately 70 °C to melt and dissolve the hardener component and reach its trigger temperature. This allows for application with a brief temperature increase, e.g., through dispenser heating and / or an IR lamp, followed by curing at room temperature.

[0060] Another advantage is that no fiber reinforcement is required in the compound or thermoset 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 groove (1) of an electrical machine characterized by - Providing a viscous thermoset emulsion in whose thermoset matrix solid particles as hardeners and magnetizable particles are mixed, - introducing the viscous duromer emulsion into the groove (1) of the electrical machine, - Heating the viscous thermoset emulsion so that the solid particles melt and react with the thermoset matrix, and - Curing of the heated duromer emulsion.

2. The method of claim 1, wherein the thermoset emulsion comprises a natural resin, an epoxy resin, or an adhesive as the thermoset matrix.

3. The method according to claim 1 or 2, wherein the hardener comprises an amine.

4. Process according to one of the preceding claims, wherein 75 to 90 percent by weight of magnetizable particles, in particular iron powder, are mixed into the duromer emulsion.

5. A method according to any one of the preceding claims, wherein the heating of the viscous thermoset emulsion is carried out just to the extent that the melting of the solid particles and the reaction of the hardener with the thermoset matrix is enabled.

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

7. A process according to any one of the preceding claims, wherein the curing of the thermoset emulsion takes place largely at room temperature.

8. Process according to one of the preceding claims, wherein after curing a thermosetting molding material with a glass transition temperature of above 60°C and in particular below 100°C is produced.

9. Method according to one of the preceding claims, wherein the heating of the viscous duromer emulsion takes place immediately before and / or immediately after the introduction of the viscous duromer emulsion into the groove (1) of the electrical machine.

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 duromer emulsion 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 a part of the strand is pressed behind a groove projection (5) 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 groove (1) of an electrical machine characterized by - a dispenser for providing a viscous duromer emulsion, in whose duromer matrix solid particles as hardener and magnetizable particles are mixed, - a nozzle (9, 9') on the dispenser for introducing the viscous duromer emulsion into the groove of the electrical machine, - a heating device (14) for heating the viscous thermoset emulsion so that the solid particles melt and react with the thermoset matrix, whereby the thermoset emulsion hardens.

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