Enameled round wire, method for producing same, and use thereof

Abstract

The invention relates to an enameled round wire, to a method for producing an enameled round wire, and to the use of enameled round wires. Until now, antifriction wire enamel, in particular those also comprising siloxane group-containing polymers, could not be impregnated because the uppermost "final" antifriction layer in the multi-layer structure of the wire enamel has non-polar properties due to the siloxane groups. According to the invention, the multi-layer structure can be used to at least break open the uppermost antifriction enamel layer using the intermediate step of energizing and / or Joule heating to 200 °C or more for a brief period, which is in any case often part of the process, so that a liquid impregnating resin can subsequently bind to the thermally instable layer located below the uppermost antifriction layer.

Description

[0001] Description

[0002] Enamel-insulated round wire, process for its manufacture and use therefor

[0003] The invention relates to a varnish-insulated round wire, a method for producing a varnish-insulated round wire and the use of varnish-insulated round wires.

[0004] A common example of a enamel-insulated round wire is a copper wire, also known as a so-called enameled copper wire. An enameled copper wire is an insulated conductor that has been coated with an electrically insulating layer of enamel during manufacture. The thickness and weight of this enamel insulation is very low compared to other insulating materials with the same effect. Enameled copper wire is therefore preferred for the construction of electrical coils, transformers, and machines. Other applications include solderable jumper wires and the production of high-frequency stranded wires.

[0005] The use of enameled copper wire advantageously reduces the mechanical size of electrical machines, resulting in space savings due to the concentration of electric and magnetic fields in a smaller space within the winding technology. Ultimately, this reduction in size also leads to energy savings with the same power output due to shorter cable runs.

[0006] Electrical insulating varnishes are used to coat the enamelled copper wires that are used as electrical conductors in electrical components such as coils, rotors and stators. To manufacture these electrical components, the coated and insulated round wire is wound using automated winding machines. The enamelled electrical wires should not be damaged at the edges of the electrical components and should fit easily into the grooves of the components so that a high packing density of the wire can be achieved in the electrical components. High packing densities are required to achieve optimum induction performance. A high packing density is also desirable because electrical machines such as electric motors that contain such electrical components are becoming more and more miniaturised due to the increased demand for ever smaller devices and components.

[0007] For example, low-voltage motors are usually manufactured using wound round enamelled wires which are drawn into the stator laminated core after the winding process. A limiting factor here is the copper filling in the slot, i.e. the number of wires which can be inserted into the slot fully automatically using this technology. The enamelled copper wires are first wound around a template using a so-called flyer winder and then pulled into the slot in bundles. The initially very orderly winding is not further fixed, which can lead to unfavourable patterns such as wire crossings. Such crossings additionally enlarge the effective cross-section of the wire bundles, which further increases the required pulling-in force and therefore the load on both the pulling-in machine and the winding.To minimize these forces and thus increase the maximum possible copper filling, state-of-the-art lubricious waxes, such as paraffins, are used as coatings. The use of siloxane copolymers in the top layer of wire enamel also significantly increases lubricity.

[0008] Good sliding properties enable the enamelled copper wire to be processed in modern high-speed automatic winding machines in which wire, braking and / or guide systems place great strain on the enamelled copper wire. For these reasons, the sliding properties of wires have developed into an important quality feature for the production and processing of insulated round wires. EP 3769403 A1 discloses an electrical insulation system EIS for an electric motor which comprises electrical conductors in the form of round enamelled wires with a round enamelled wire winding arranged in a slot in a laminated core of a stator. The cavities between the windings of the conductors are filled with impregnating resin. The impregnating resin content is determined by introducing a carrier containing impregnating resin into the conductor in order to adequately encapsulate the cavities in the conductor of the laminated core.The impregnating resin wets the surface of the round wire enamel before it hardens.

[0009] The wire enamel itself comprises a multitude of individual plastic layers, for example made of polyethylene, "PE", polyetherimide, "PEI", polyamideimide "PAI", polyimide "PI", whereby each layer is applied in a sliding manner to the layer below and / or above it in order to be flexible with respect to mechanical stress, e.g. stretching, bending, etc.

[0010] Using siloxane copolymer technology – at least in the topmost wire enamel layer – it is possible to achieve very high copper fillings in a fully automated manner. However, subsequent impregnation – for example of the filled slot – using impregnating resin such as polyetherimide, polyether and / or epoxy resin is not possible because the chemical surface groups that provide lubricity repel the impregnating resin. In particular, no chemical bond can be created between the non-polar functional groups – for example siloxane or fluorine groups, i.e. the anti-friction enamel surface on the one hand, and the polar impregnating resin on the other. Impregnation of a round wire with high lubricity, produced by fluorine and / or siloxane groups on the surface, has therefore not been possible to date. However, impregnating resins are regularly used in the slots of low-voltage motors.Therefore, it is an object of the present invention to provide a round wire enamel which combines high lubricity with good impregnability with the conventional impregnating resins based on polyurethane, polyetherimide, polyether and / or epoxy resin.

[0011] This object is achieved by the subject matter of the present invention as disclosed in the description, the figures and the claims.

[0012] Accordingly, the subject of the present invention is an enamel-insulated round wire, comprising an electrical conductor insulated with wire enamel which surrounds the round wire in a sheathing manner, such that a layer of thermally unstable material is provided as the uppermost layer or as the penultimate layer of the wire enamel insulation directly adjacent to the surface.

[0013] The invention also relates to a method for producing a varnish-insulated round wire, comprising the following process steps:

[0014] - Application of polymerizable lacquer material layer by layer onto the round wire,

[0015] - Layer-by-layer curing and polymerization of the paint material to obtain a thin polymerized paint layer,

[0016] - Optionally repeat the first two process steps until a round wire with a varnish insulation in the multi-layer wire enamel structure is obtained,

[0017] - Applying a thermally unstable layer over it,

[0018] - Making the winding,

[0019] - Pulling the winding into the slot,

[0020] - Heating of the filled groove, which initiates decomposition of the thermally unstable layer, impregnation by immersion in liquid impregnating resin and subsequent

[0021] - Curing. Finally, the invention also relates to the use of a varnish-insulated round wire as described above and a layer of thermally unstable material thereon for the manufacture of low-voltage electric motors.

[0022] According to an advantageous embodiment of the invention, a layer of anti-friction varnish is applied over the thermally unstable layer, which layer at least becomes perforated when the thermally unstable layer decomposes and / or is partially or completely removed in some places by gas release from the decomposing lower thermally unstable layer. The layer of anti-friction varnish can be provided over the entire surface or in part, whereby in the case of partial coating with anti-friction varnish, the latter floats in certain areas like "ice floes" on the lower layer, especially when it melts on the lower layer. The anti-friction varnish can make up a proportion of the surface, for example, in the range of 40% to 100%, preferably 50% to 99%, in particular also in the range of 55% to 95% of the surface of the wire enamel insulation.

[0023] According to a further advantageous embodiment of the invention, a lubricating varnish is chemically designed in such a way that the base is thermally unstable, wherein lubricity is achieved superficially by incorporating, copolymerizing, mixing and / or blending the base polymer with lubricity components.

[0024] Such sliding components are, for example, paraffins, waxes, soaps, lubricants, solid lubricants, organic groups and compounds such as surfactants, organosilicon compounds, in particular siloxanes, polysiloxanes, silazanes, polysilazanes, boron nitride, fluorinated compounds such as perfluorooctanoic acid "PFOA", polytetrafluoroethylene "PTFE" or "Teflon®" and similar in the thermally unstable wire enamel insulating layers.

[0025] According to one embodiment of the invention, the uppermost wire enamel insulation layer is made of a thermally unstable material such as polyethylene, so that after introduction into the groove, this layer decomposes upon heating and exposes the underlying layers, which are, for example, part of a multi-layer wire enamel structure that is compatible with the impregnating resins.

[0026] The thermally unstable layer comprises, for example, a compound selected from the group consisting of: polyethylene, polyethylene glycol, polyolefin and / or polyolefin wax, alone or in any combination. The temperature stability can be influenced by varying the chain length of the polymer. Generally, the temperature stability shifts to higher temperatures with a longer chain length.

[0027] When impregnating electric motors, the so-called current UV process is frequently used. This involves preheating the stators by applying current to the individual phases before immersing them in the liquid impregnating resin. The temperatures in the copper windings, which are heated directly by the Joule effect, briefly reach 200°C to 300°C before the heat is distributed relatively evenly throughout the stator. Clamping the stators and heating them is therefore common practice, also to reduce the viscosity of the impregnating resin and to specifically induce chemical gelation.

[0028] Conventional wire enamels comprise several layers, for example, in the range of 3 to 30, of different or identical polymers, e.g., polyetherimide, polyetherimine, and / or polyamideimide, as well as any combinations or mixtures thereof. This is generally referred to as a multilayer wire enamel structure.

[0029] In particular, impregnating resins based on polyurethane, saturated and particularly preferably unsaturated polyesterimide, polyamideimide, polyester and / or epoxy resin, as well as any combinations, mixtures, copolymers and / or blends thereof, are used for the multilayer wire enamel structure. The number of layers varies; for example, it is between 3 and 25 layers, preferably 7 to 20 layers, or 10 to 20 layers, particularly preferably, for example, 15 layers.

[0030] Preferably, the layers are hardened separately from one another so that sliding interfaces are created between them and no chemical bond occurs between the layers.

[0031] For example, the thermally unstable layer can also be applied as a top layer, which is somewhat thicker than the other wire enamel layers.

[0032] The layers of the multilayer wire enamel structure for the wire enamel insulation of round wires are in terms of layer thickness in the range from 0.2 pm to 200 pm, in particular from 0.3 pm to 50 pm and particularly advantageously in the range between 0.5 and 20 pm.

[0033] The thermally unstable layer is also applied, for example, as a prepreg based on polyethylene and / or polyethylene glycol.

[0034] In the following, the invention is explained in more detail with reference to three figures which show the prior art and exemplary embodiments of the invention:

[0035] Figure 1 shows an overview of the state of the art of how enamel-insulated round wires are usually constructed and are present as an impregnated composite in a groove, for example of a low-voltage electric motor such as a traction motor.

[0036] A composite 7 of round wires 1 insulated with wire enamel 2 and impregnated with impregnating resin 3 can be seen.

[0037] To the right of the composite, a conical detail section 4 is shown enlarged, again showing the round wire 1 and wire enamel 2. The individual layers 4 of the wire enamel 2 are visible in the enlarged view.

[0038] Below the detailed view is a further enlargement of the conical section shown above, showing another prior art example. Above the usual wire enamel layers 2, e.g., with a layer structure 4 as shown above, there is a lubricating enamel layer 5. This lubricating enamel layer 5 comprises, e.g., a siloxane copolymer, which gives the lubricating enamel layer 5 a lubricious surface 8, but unfortunately, the impregnating resin 3 beads up off it.

[0039] Directly adjacent to the area between round wire 1 and conventional wire enamel 2 there is this layer of anti-friction varnish 5 with a lubricant additive, for example with a siloxane copolymer, and following this there is a red dashed boundary surface 8 on the surface of the anti-friction varnish layer 5, which illustrates the at least poor or even completely missing chemical bonding of the impregnating agent 3 to the uppermost anti-friction varnish layer 5 enriched with lubricant on the surface in Figure 1. The problem of the present invention arises because of this layer 8, which would form according to the SdT if the round wires with anti-friction varnish layer 5 were impregnated with impregnating resin 3. The technology using anti-friction varnish wires is generally only used without subsequent impregnation because impregnation is of no technical use as long as the impregnating resin 3 beads up on the anti-friction varnish 5.

[0040] Figure 2 shows - based on this prior art - the solution according to the present invention using an exemplary embodiment.

[0041] The multi-layer wire enamel structure 2 or 4 is used again on the round wire 1 . A thin anti-friction coating layer 5 is applied as the top "final" layer. There are many anti-friction coatings 5 ​​that are suitable for the area of ​​application relevant here. For example, natural waxes, montan waxes, polyethylene waxes, and copolymers with propylene polymers made from higher α-olefins, polypropylene oxides, esters from more functional polyols and longer-chain fatty acids are suitable. But polytetrafluoroethylene dispersions, as known from WO 2007 / 045575, are also suitable as anti-friction coating for the anti-friction coating layer 5 . Finally, there are anti-friction coating layers 5 with siloxane copolymer that are suitable as anti-friction coating layer 5 . In a further approach to improving the lubricity of electrical insulating varnishes, the polymers contained in the varnish are functionalized with components, e.g. the modification of polyamideimides with terminal longer-chain alkyl groups.

[0042] Beneath the last uppermost anti-friction coating layer 5 and directly adjacent to it, there is a thermally unstable layer 10, for example made of polyethylene glycol, as the "penultimate" layer. The thermally unstable layer 10 can also be made of another suitable polymer which decomposes at higher temperatures, such as those which occur during the manufacture of low-voltage motors with already filled stator slots, and - for example through the evolution of gas such as CO2 - at least partially blows off the upper layer, as shown by the arrow 11 in Figure 2.

[0043] The core of the invention is to use the multi-layer structure of a wire enamel in order to use the top layer of lubricating enamel effectively for the drawing-in process of the enamel-insulated round wires into the stator slot of the motor and then - after filling the slot - to destroy the lubricating layer by "bursting" an underlying layer through the introduction of temperature to such an extent that a surface that can be chemically bonded to the impregnating resin is exposed.

[0044] This is shown in Figure 2 :

[0045] On the far left in Figure 2 you can see a thermally unstable layer 10 as the "second to last" thin layer on the multi-layer wire enamel structure 2 - 4. Above this is the last layer of anti-friction varnish 5, which cannot be chemically bonded to the impregnating resin. Arrow 11: By heating, e.g. by applying current, the winding already in the slot during manufacture of the motor, a temperature is introduced into the thermally unstable layer 10 and it decomposes. This decomposition usually releases CO2 gas and causes the overlying anti-friction varnish layer 5 to burst in many places, so that the material of the second to last layer 10 comes to rest on the surface of the enamel insulation. See central illustration in Figure 2.

[0046] Arrow 12: Impregnation of the winding with impregnating resin 3 now encounters a surface that consists at least partially of a thermally unstable layer 10, whereby a good chemical bond between the impregnating agent 3 and the thermally unstable layer 10 is possible at these points. On the other hand, the multilayer wire enamel structure 2, or 4, is exposed below the decomposed thermally unstable layer 10, via which a good chemical bond to the impregnating resin 3 is also possible.

[0047] On the left in Figure 2, the good chemical bonding of the impregnating resin 3 to the surface of the enamel-insulated round wire 1 according to the invention is shown, because in many places the material of the thermally unstable layer 10 or the multi-layer wire enamel 4 forms the surface of the wire insulation.

[0048] Figure 3 shows a further advantageous embodiment of the invention. By introducing siloxane groups into the thermally unstable layer after the round wires coated with lubricating varnish have been drawn into the groove, the lubricating varnish layer is at least partially decomposed during the subsequent heating, thereby exposing the underlying multilayer wire enamel structure 4, which can form a good chemical bond on the surface with an impregnating resin.

[0049] In detail, the structure of a round wire 1 drawn into the groove by means of surface-mounted lubricating varnish 9 is shown again on the left. The lubricating varnish 9 is designed in such a way that, in addition to the sliding properties achieved by the siloxane groups it contains, it has a thermally unstable material, such as polyethylene and / or polyethylene glycol, as its base material.

[0050] Thus, upon exposure to temperature – indicated by arrow 11 – which occurs during engine manufacture, the anti-friction coating 9, based on a thermally unstable material, dissolves. Beneath the anti-friction coating 9, the multi-layer wire enamel structure 4 is exposed, which – see arrow 12 – has a surface that bonds well to the impregnating resin 3 when impregnated with the impregnating resin 3.

[0051] This means that both the advantages of the lubricating coating technology and those of impregnation can be used.

[0052] Until now, it has not been possible to impregnate lubricious wire enamels, particularly polymers containing siloxane groups, since the top "final" sliding layer in the multi-layer structure of the wire enamel has non-polar properties due to the siloxane groups. The invention shows that the multi-layer structure can be used to at least break up the top layer of sliding enamel by briefly heating to 200 °C or more without the often necessary intermediate step of applying current and / or Joule heating, so that a subsequent impregnation with liquid impregnating resin can bond to the thermally unstable layer located beneath the top layer of sliding enamel.

[0053] Reference symbol list

[0054] 1 round wire

[0055] 2 Wire enamel

[0056] 3 Impregnating resin

[0057] 4 multi-layer wire enamel structure

[0058] 5 State-of-the-art lubricating coating

[0059] 6 Detail section

[0060] 7 Composite of enamel-insulated round wires and impregnating resin

[0061] 8 Interface that does not chemically bond to impregnating resin

[0062] 9 Thermally unstable anti-friction coating

[0063] 10 Thermally unstable penultimate layer

[0064] 11 Arrow

Claims

Patent claims 1 . Enamel-insulated round wire, an electrical conductor which is insulated with wire enamel which surrounds the round wire, comprising, in such a way that a layer of thermally unstable material with a lubricity component is provided as the uppermost layer and / or a thermally unstable layer is provided as the penultimate layer of the wire enamel insulation directly adjacent to the surface.

2. Round wire according to claim 1, wherein the wire enamel is realized in a multi-layer wire enamel structure with 2 to 40 layers.

3. Round wire according to one of claims 1 or 2, in which a multi-layer wire enamel structure with 10 to 20 layers is present. 4 . Round wire according to one of the preceding claims, in which the individual layers of the wire enamel have a layer thickness in the range of 0.2 to 200 pm.

5. Round wire according to one of the preceding claims, in which the individual layers of the multi-layer wire enamel structure are made of polymeric material.

6. Round wire according to claim 4, wherein the individual layers of the multi-layer wire enamel structure comprise an impregnating resin selected from the group of the following compounds: epoxy, polyetherimide, polyurethane and / or polyamideimide, as well as any combinations and / or mixtures thereof. 7 . Round wire according to one of the preceding claims, in which after each wire enamel layer of the multi-layer wire enamel structure, the layer is cured before the application of the next layer and thus there are sliding surfaces between the layers.

8. Round wire according to one of the preceding claims, wherein the thermally unstable layer comprises one or more lubricity components.

9. Round wire according to one of the preceding claims, wherein the thermally unstable layer comprises siloxane, silazane and / or fluorine groups which impart a lubricious surface to the thermally unstable layer.

10. Round wire according to one of the preceding claims, wherein the thermally unstable layer comprises a material selected from the group of the following compounds: polyethylene, polyethylene glycol, polyolefin and / or polyethylene wax alone or in any combinations, blends and / or copolymers.

11. Round wire according to one of the preceding claims, wherein the thermally unstable layer is thicker than the other layers of the multi-layer wire enamel structure.

12. Round wire according to one of the preceding claims, wherein the multi-layer wire enamel structure of the round wire has a thermally unstable layer as the penultimate layer and, lying thereon, comprises a lubricating enamel layer as the last and uppermost layer. 13 . A process for producing a varnish-insulated round wire, comprising the following process steps: - Application of polymerizable lacquer material layer by layer onto the round wire, - Layer-by-layer curing and polymerization of the paint material to obtain a thin polymerized paint layer, - Repeat the first two process steps several times until a round wire with a varnish insulation in a multi-layer wire enamel structure is obtained - Applying a thermally unstable layer over it, - Making the winding - Pulling the winding into the slot - Heating of the filled groove, which initiates decomposition of the thermally unstable layer, impregnation by immersion in liquid impregnating resin and subsequent - Curing .

14. A method according to claim 13, wherein the heating step is carried out at least in part by applying current.

15. Use of a lacquer-insulated material according to one of claims 1 to 12 for the production of low-voltage electric motors.

Images