METHOD FOR MANUFACTURING AN ELECTRIC MOTOR WITH AN ELECTRICAL INSULATION SYSTEM

Description

[0001] The invention relates to an improved method for manufacturing an electric motor with an electrical insulation system, in particular an improved electrical insulation system (EIS) with regard to the insulation of the wire windings in the slots of the laminated core against the laminated core.

[0002] Laminated cores of electric motors are well-known; these cores contain slots with a wire winding, usually a copper wire winding, where the wire is electrically insulated by a wire enamel coating and the sheet insulation material forming the winding. Depending on the size and power rating, there are various methods for manufacturing electric motors.

[0003] DE 31 33 811 A1 describes single- or multi-layer windings or coils for electrical machines made of insulated round wires, to which thinner threads, rovings, or strips of flexible, non-conductive material are wound in parallel. These arrange themselves in the spaces between the wires, partially filling the cavities and increasing capillary action, so that the subsequently added impregnating resin remains better in the winding. Optionally, the threads can be coated, for example with accelerators that cause the impregnating resin to gel more quickly in order to prevent leakage.

[0004] In the range of shaft heights from 63 mm to 450 mm and power outputs from 150 W to 1.6 MW, the stator, i.e., the laminated core, is typically fitted with pre-wound conductors. These windings are mechanically pulled into the stator slots and then switched. Electrical insulation between the individual wires and from the laminated core, which is at ground potential, is provided by surface insulation materials such as wrapping paper and the enamel coating on the individual winding wires. Due to the geometric requirements of the slots, such as the core, which serves to create as closed a magnetic field line as possible, a maximum slot filling of 85% by volume with copper wire, including the enamel coating, is possible. Otherwise, the pulling forces would become too great, potentially damaging the surface insulation, i.e., the wrapping paper and / or the enamel coating, for example, through scratches, cracks, and / or stretching.As a result, at least 15% of the volume remains free in the slots of the lamination stack, some of it within the conductor and some between the conductor and the inside of the slot, for example in the corners where the conductor does not lie exactly against the inner edge of the slot. The portion of the free volume that lies within the conductor should ideally be filled as completely as possible by impregnation with impregnating resin.

[0005] Impregnation processes such as immersion methods are typically used, in which one or more stators are slowly immersed in a bath of liquid impregnating resin. This allows the liquid resin to flow into the cavities between the individual wires of the conductor and the lamination stack, filling these spaces. The impregnated stators are then cured over a period of time by exposure to heat and / or UV radiation. This process transforms the liquid and / or gelled impregnating resin, which fills the remaining cavities in the grooves within the conductor's hollow volume, into a finished potting compound, for example, a fully cured thermoset resin. The quality of the impregnation is ultimately defined by the highest possible degree of cavity filling and the lowest possible residual enthalpy of the impregnating resin.Ideally, firstly, the cavities of the conductor should be completely filled with impregnating resin, and secondly, the impregnating resin should be completely cross-linked.

[0006] A disadvantage of this is that, for impregnation of different stator types, the rheology and chemical reactivity of the impregnating resin must be adjusted to the respective stator type to ensure complete filling of the cavities, for example in the immersion bath.

[0007] Depending on the stator type, a higher or lower viscosity is required so that the impregnating resin completely fills the cavities and simultaneously gels quickly, which then prevents the impregnating resin from flowing out when the stator is removed from the immersion bath.

[0008] In order to enable the economical impregnation of different stator types in a common immersion bath, the rheology, viscosity and / or chemical composition of the immersion bath is adjusted to an average value without optimization with regard to any one stator type.

[0009] The object of the present invention is therefore to provide a means of targeted filling of the conductor, in particular the wire winding of a stator, with impregnating resin, without chemical alteration of the impregnating resin, in the immersion bath with regard to rheology, viscosity and / or gel times.

[0010] This problem is solved by the subject matter of the present invention as disclosed in the description and the claims.

[0011] Accordingly, the invention relates to a method for manufacturing an electric motor with an electrical insulation system comprising a laminated core with slots and, in these slots, electrically surface-insulated wire windings with individual wires in a potting compound, wherein between the wires of the wire winding and / or around the individual wires, but within the wire winding bounded by the surface insulation material, there is absorbent material suitable for receiving liquid impregnating resin, which, after hardening and completion of the electrical insulation system, forms the potting compound, comprising the following process steps: Winding a conductor from winding wire coated with wire enamel, wherein the finished wound conductor contains absorbent material, insertion of the conductor thus produced into the slots of a laminated core, immersion of the wound laminated core in an impregnating resin, curing of the impregnated laminated core, wherein at least fibers are used as absorbent material, wherein an intermediate step for heating the laminated core is interposed between drawing the conductor into the slots of the laminated core and immersing the laminated core in the impregnating resin, wherein fibers with a surface adhesive coating are used in the conductor, wherein the adhesive is selected at least in part such that it decomposes and / or evaporates during the intermediate heating step.

[0012] The general insight of the invention is that by introducing absorbent material, for example in the form of a foam, fibers, and / or fiber fragments such as polymeric fibers, between and / or around the wires of a wound conductor, this material acts like a sponge upon contact with liquid impregnating resin and, under certain circumstances, even expands in volume to absorb and / or retain the liquid impregnating resin, for example, within the wire winding with or without gelation. This ensures that the filling of the cavities in the wire winding is equally effective across a wide viscosity range, for example, with regard to the impregnating resin in the immersion bath.The adjustment of specific gelling properties of the impregnating resin - for example in an immersion bath - becomes unnecessary, since the liquid and ungelled impregnating resin is held in position by the capillary forces of the absorbent material even without early surface gelation.

[0013] The invention provides an absorbent material in the form of fibers. These fibers can be long fibers and / or continuous fibers. The fibers can then be wound, just like the conductor wires, and together with the conductor wires form a wound conductor.

[0014] In this context, a "conductor" is defined as a winding of wires wound together in a sheet insulating material, such as paper, forming a bundle of winding wires that is inserted into a groove of a laminated core. If a conductor is cut open in cross-section, one can ideally discern circles representing the diameters of the wires that form the "densest" packing within the conductor, analogous to the densest packing of spheres in a crystal. Analogous to the volume filling of the densest packing, which is 74%, it is assumed here that the remaining 26% of the conductor's volume can be filled with absorbent material. According to the invention, the aim is to fill as much of this void space as possible, which cannot be utilized by the wires anyway due to dimensional constraints, with absorbent material.

[0015] It is particularly advantageous if the fibers are wound simultaneously with the bundling of the winding wires, especially the copper wires, and are thus present between the copper wires in the conductor with these in the winding and in the finished electric motor.

[0016] According to a preferred embodiment of the invention, the number of fiber windings in relation to the copper wire windings is selected in such a way that no space in the groove and / or in the conductor, which could be filled with copper wire, is thereby occupied.

[0017] The number of fiber turns is selected accordingly within the tension field between high enough to ensure the most complete possible impregnation of the stator core after hardening and as low as possible so that the volume fill level in the wire winding with conductor material, in particular with conductive winding wire, preferably copper wire, is not negatively affected.

[0018] During the winding process, the fibers primarily settle into the spaces between the wires, thus reducing the volume fill factor only minimally or not at all. The tensile forces during the winding process further stretch the individual fibers, thereby reducing their diameter.

[0019] For example, long and / or continuous fibers are present in the conductor at a ratio of one fiber to 10 wires. Specifically, the fiber-to-wire ratio in the conductor ranges from 1:10, as described above, to 2:1, meaning more fibers than wires in the conductor. The respective proportions depend, for example, on the fiber's absorbency, its diameter, etc.

[0020] According to a further embodiment of the invention, the fibers are additionally or alternatively laid, drawn and / or spun around the winding wires in addition to bundling.

[0021] According to a further embodiment of the invention, the fibers are introduced into the winding wire in addition to or as an alternative to the winding by spraying and / or other insertion in the form of, for example, a foam and / or short and / or ultra-short fibers.

[0022] In the invention, the fibers themselves are surface-treated. For example, the surface treatment makes it easier to wind the fibers with the winding wires, which have a wire enamel coating on their surface. The surface treatment of the fibers preferably allows the fibers to slide more easily on the wire enamel coating of the winding wires. This makes it easier and more efficient to wind the fibers together with the winding wires.

[0023] The winding wires are superficially treated with an adhesive, so that a slight adhesion of the fiber to the wire enamel is achieved, which allows the fibers to adhere better in the winding bundle until the winding, i.e. the wire-fiber bundle, is fixed or laid down in the groove by the insertion process.

[0024] For example, the adhesive is selected from adhesives of the following group: spray adhesive, Uhu, Tesa, 3M, as well as any adhesive mixtures of the aforementioned and / or additional adhesive types.

[0025] When selecting a suitable adhesive, key considerations include compatibility with the impregnating resin, complete cross-linking of the adhesive, adhesive strength, and whether the bonded fiber can be repositioned and / or reattached. The chemical composition of the adhesives under consideration also includes, in particular, acrylic adhesives.

[0026] The adhesive content is chosen to be just high enough to ensure that the yarn remains bound together during the winding process and does not separate. This leaves a large proportion of the individual fibers exposed, creating a very large surface area in the otherwise empty space between the winding wires, especially the copper wires.

[0027] According to an advantageous embodiment of the invention, the fiber is, for example, initially compacted by the adhesive, so that the effective volume of the fiber is smaller during winding. It is particularly advantageous if an adhesive is selected that can be at least partially removed during the preheating phase of the stator—especially advantageously before the actual impregnation of the stator—i.e., that evaporates, vaporizes, and / or decomposes into gaseous products.

[0028] The fiber, now free of adhesive, can then fan out and / or swell again, exhibiting virtually an optimum in absorbency and capillary forces for the uptake of impregnating resin.

[0029] The liquid impregnating resin, which comes into contact with the fiber and the wire winding - for example by immersing the stator in a dipping bath - is thus drawn into the spaces between the wires of the wire winding by the capillary forces of the fiber and / or by swelling of the fiber and held there.

[0030] This eliminates the need for extensive thixotropy and simplifies the chemical formula, as a precise gelation process for mechanically fixing the liquid impregnating resin within the conductor is no longer required. The overall viscosity can be lower because capillary action from the fibers between the wire windings at least partially prevents the resin from flowing back.

[0031] This also accelerates and improves the flow of the impregnating resin on the outer surfaces, because the gelling properties of the impregnating resin are no longer set at their highest possible level. This means that the impregnating resin does not gel as quickly and can therefore flow off more easily.

[0032] Additional advantages can arise from impregnating the winding head, as the existing spaces between the wire strands are filled with resin in a defined manner due to the fibers. Particularly during operation with a frequency converter, the additional impregnating resin introduced via the fibers and the resulting additional potting compound result in a longer service life under high voltage peaks triggered by the converter.

[0033] An almost complete impregnation of a wire-fiber winding, such as a stator winding, according to the present invention, i.e., filling air inclusions with impregnating resin, enables significantly better heat dissipation in the winding.

[0034] The invention uses cost-effective materials and minor modifications to the manufacturing process, such as the addition of a fiber to the conventional winding process, to condition unimpregnated stators so that they can be impregnated more efficiently and cost-effectively. The major advantage lies particularly in the resulting manufacturing flexibility of a single impregnation layer.

[0035] By introducing the fibers into the cavities of the winding, capillary effects are created, which preferentially retain the liquid impregnating resin in the spaces between the wires. This fiber insertion can easily be integrated into the preceding winding process without significantly altering it.

[0036] The impregnation process can be optimized in terms of time, since the process duration mainly depended on the gelling time, which no longer needs to be fully waited for due to the capillary effects mentioned above.

[0037] The impregnating resin can be obtained more cost-effectively, as the technical requirements such as gelling time, thixotropy and / or a precisely defined reaction process are significantly lower.

[0038] Manufacturing variance increases because the points mentioned above are no longer decisive, and thus stators of different shaft heights can be operated in the same system / process.

[0039] Because less pre-reacted and potentially contaminated resin drips from the stator back into the resin tank, less cleaning and / or regulation effort is required. Furthermore, scrap rates can be reduced.

[0040] The invention demonstrates for the first time a way to achieve cost-effective and complete impregnation of a wire winding of an electric motor by introducing fibers.

Claims

1. Method for producing an electric motor having an electrical insulation system comprising a laminated core having slots and wire windings, electrically surface insulated in these slots, with individual wires in a potting compound, wherein there is absorbent material between the wires of the wire winding and / or around the individual wires but within the wire winding bounded by surface insulation material, said absorbent material being suitable for taking up liquid impregnation resin that forms the potting compound after it has cured and the electrical insulation system has been completed, said method comprising the following method steps: - winding a conductor from winding wire that is surrounded by wire enamel, wherein absorbent material is contained in the fully wound conductor, - introducing the conductor produced in this way into the slots of a laminated core, - dipping the wound laminated core in an impregnation resin, - curing the impregnated laminated core, wherein at least also fibres are used as absorbent material, wherein between the pulling of the conductor into the slots of the laminated core and the dipping of the laminated core in the impregnating resin, there is interposed an intermediate step of heating the laminated core, wherein fibres having a surface adhesive coating are used in the conductor, wherein the adhesive is at least partially selected such that it breaks down and / or evaporates during the intermediate step of heating.

2. Method according to Claim 1, wherein the absorbent material at least partially comprises a foam.

3. Method according to either of the preceding claims, wherein the absorbent material at least partially comprises endless fibres.

4. Method according to one of the preceding claims, wherein the absorbent material at least partially comprises long fibres.

5. Method according to one of the preceding claims, wherein absorbent material in the form of fibres is wound simultaneously with the winding wires to form a conductor.

6. Method according to one of the preceding claims, wherein the proportion of absorbent material in the conductor is in the range of up to 26% by volume of the total volume in the conductor.