Insulation system comprising a solid insulating material and an impregnating resin

Abstract

The present invention relates generally to the field of insulating electrical conductors against partial discharges in the medium and high voltage range. In particular, the present invention relates to an insulation system for electrical machines, in particular rotating electrical machines such as electric motors and / or generators. With the present invention, a replacement for mica conventionally used as a barrier system in insulation systems, for example in the main insulation of rotating electrical machines such as electric motors and / or generators, is provided for the first time. The replacement is based on a blend of a copolymer, in particular a polyetherimide-siloxane copolymer, with a high-temperature thermoplastic, which can be processed flat, for example by plane extrusion. A film is produced here, which is processed in the form of a film or as a laminate, as a flat insulation material or as a tape cut, can be used in insulation systems as a wrapping tape insulation and / or as a slot lining.

Description

[0001] This invention generally relates to the field of insulating electrical conductors to prevent partial discharge in medium and high voltage ranges. In particular, this invention relates to insulation systems for electric motors, especially rotating electric machines such as motors and / or generators.

[0002] Electric motors, such as engines and generators in the medium and high voltage range, have electrical conductors, a main insulator, and a stator laminated iron core. The purpose of the main insulator is to electrically insulate the conductors from each other, relative to the stator laminated iron core, and relative to the environment. During motor operation, so-called "tree-like" channels may form in the main insulator due to partial discharge (TE). Electrical breakdown through the main insulator can occur due to these "tree-like" channels. In the low-voltage range where wires and cables are used, discharge may not necessarily occur during operation, therefore, barriers against partial discharge are not required there.

[0003] Here, "medium and high voltage range" refers to electrical energy technologies operating at voltages exceeding 700V—up to 52kV. This also includes insulation systems, which are of interest to the automotive industry for its fast-charging drive systems.

[0004] To date, barriers against partial discharge have primarily been achieved in the form of flat insulating materials using mica, which has high resistance to partial discharge, in the main insulator. The mica is processed into mica paper in the form of flake-like mica particles with a conventional particle size of several hundred micrometers to several millimeters. This mica paper is then placed and bonded to a carrier, such as fiberglass fabric and / or an insulating film, so that these mica particles form a flat insulating material in the form of a mica broadband strip. Mica tape is cut from the mica broadband strip and wound around a conductor to produce the main insulator. Then, to manufacture the insulating system, the electrically insulating mica winding tape is impregnated with a liquid synthetic resin, which is then cured.

[0005] The insulation system is known—for example, by brand. Known systems in which bisphenol epoxy resin is used to impregnate a mica winding tape as the main insulator in a vacuum pressure impregnation method, comprising a flat insulating material.

[0006] It can also be found in EP2763142A1 and DE 102011083228A.

[0007] To improve the partial discharge resistance of the main insulator, nanoscale particles dispersed in a synthetic resin prior to impregnation are known to be used. However, the presence of these particles shortens the pot life of the synthetic resin, particularly during the progressive polymerization of the resin prior to impregnation.

[0008] The production of mica as a channel liner and / or as a flat insulating material in the form of mica broadband and / or mica tape is complex and expensive.

[0009] In particular, for traction engines, due to requirements, mica-containing laminates with carrier materials such as meta-aramids and polyimides have been used for tank linings to date. To maximize machine performance, it operates at the highest possible current density, but this also results in significant heat loss. Traction engines operate at relatively high temperatures, especially above 150°C.

[0010] DE 102020208760 discloses a flat insulating material made from a copolymer of polyetherimide and siloxane, but it exhibits a softening point at elevated temperatures, such as those present in traction engines. This is particularly because, in the polyetherimide-siloxane copolymer, the lower polarity of the siloxane side groups (which act as “impurities” compared to pure polyetherimide) leads to a lower glass transition temperature. Although polyetherimide-siloxane copolymers can be produced flat as films by suitable extrusion methods, and these films themselves are elastic enough to be used as winding tapes—in fully cut form—these winding tapes are not suitable for use in operating temperature ranges exceeding 150°C, and particularly exceeding 170°C.

[0011] Therefore, the object of the present invention is to provide a flat insulating material having a softening temperature and / or melting point of at least 150°C, preferably higher and / or having a temperature index of 180°C or—if possible—even higher.

[0012] This objective is achieved through the subject matter of the invention as disclosed in the specification, drawings and claims.

[0013] Therefore, the subject of this invention is an insulation system comprising a solid insulating material in the form of a flat insulating material and a synthetic resin, wherein the flat insulating material exists as a film and is a blend of a copolymer of polyetherimide and siloxane with a high-temperature thermoplastic, such as polyimide, and the synthetic resin is a thermosetting plastic, which is used to impregnate the flat insulating material and then cure it.

[0014] The overall discovery of this invention is that a mixture of copolymers, particularly siloxane-polyetherimide copolymers, with high-temperature thermoplastics in the form of blends (e.g., also containing one of the copolymer's reaction partners as a blending partner) produces a stable mixture suitable for membrane production.

[0015] High-temperature thermoplastics, such as polyetheretherketone (PEEK), polyaryletherketone (PAEK), polyphenylene ether (PPE), polyoxymethylene (POM), perfluoroalkoxy polymer (PFA), polyvinylidene fluoride (PVDF), polyetherketone (PEK), polyetherketoneketone (PEKK), polytetrafluoroethylene (PTFE), polyphenylsulfone (PPSU), polyethersulfone (PES), polysulfone (PSU), poly(oxy-1,4-benzenesulfonyl-1,4-phenyl)PESU, polyamide-imide (PAI), polybenzimidazole (PBI), and / or polyetherimide (PEI), have proven particularly advantageous because they almost completely suppress blend separation during membrane production. Furthermore, the use of polysulfone as a blending partner for copolymers of polyetherimide and siloxanes has proven suitable because membrane production can also be achieved by extrusion without significant separation.

[0016] Other high-temperature thermoplastics are: other (one or more) polyimides, polyamide-imide-PAI-, polyetherketone-PEK-, polyetheretherketone-PEEK-, polyetherketone-ketone-PEKK-, polysulfone-PSU- and / or-PPSU-, polyphenylene sulfide-PPS-, polyethersulfone-PES-, poly(oxy-1,4-benzenesulfonyl-1,4-phenyl)-PESU-, and polyaryletherketone-PAEK-.

[0017] All the high-temperature thermoplastics mentioned can be used alone and / or in any combination and mixture.

[0018] High-temperature thermoplastics preferably contain an aromatic basic structure. These compounds are therefore primarily resistant to oxidation and secondarily resistant to free radical formation. Both of these are particularly important when resistance to partial discharge is required. Specifically, in the case of aromatic polymers, the chain stiffness is also greater, resulting in a higher glass transition temperature.

[0019] The high-temperature thermoplastics used as blending partners can be partially crystalline, crystalline, and / or amorphous—that is, they can also exist as mixtures of these variants. Partially crystalline or crystalline high-temperature thermoplastics are preferred as blending partners because they exhibit particular stability against oxidation, partial discharge, and / or free radical formation.

[0020] As copolymers, particularly polyetherimide-siloxane copolymers, have proven to have great potential as insulating materials in the medium and high voltage ranges in terms of resistance to thermal loads and partial discharges. The softening temperature of the copolymers as flat insulating materials is only slightly above 170°C, allowing them to be used as flat insulating materials in insulation systems at higher operating temperatures, particularly above 180°C.

[0021] By blending the blends according to the invention, i.e., the copolymers blended with, for example, 1 to 90% by weight of a high-temperature thermoplastic, a flat insulating material that can be processed as a film is produced because it does not exhibit separation problems and can be used within a certain temperature range—that is, for example, motor operating temperatures of 170°C to 250°C.

[0022] In particular, the drive engine and traction engine are rotating electric motors that operate at high temperatures, specifically above 155°C.

[0023] Polymers that form blends with high-temperature thermoplastics are known, but are typically blends of polymers that separate again during film production, i.e., during film stretching. Therefore, when adding blending partners, attention must be paid to the reactivity of the side groups, where it has been shown that the polar side groups of the copolymer combine advantageously with thermoplastics having similarly polar side groups, particularly in the production of flat insulating materials in film form. Therefore, polysulfones, such as polyphenylsulfone and polyethersulfone, are preferred as blending partners for copolymers of polyetherimide and siloxane.

[0024] It is feasible to produce films from blends of thermoplastics and copolymers, such as copolymers formed from polyetherimide and siloxane, and to use such films as flat insulating materials to replace mica-containing materials, because, among other advantageous properties, the great potential of such flat insulating materials in terms of resistance to heat loads has been recognized and proven.

[0025] Partial discharge resistance was assessed using a surface profilometer by determining the specific erosion volume after electrical aging. This was performed according to IEC 60343. The experimental setup and test conditions can be found in the following publication: n. Müller; S. Lang; R. Moos: "Influence of ambient conditions on electrical partial discharge resistance of epoxy anhydride based polymers using IEC 60343 method". Transactions on Dielectrics and Elektrical Insulation 2019.

[0026] According to an advantageous embodiment, the polyetherimide-siloxane copolymer is a block copolymer.

[0027] The proportion of siloxane in the copolymer is from 0.1% to 90% by weight, particularly from 10% to 60% by weight, particularly from 20% to 40% by weight, based on the total weight of the copolymer.

[0028] According to an advantageous embodiment, the atomic percentage of silicon atoms in the copolymer is 0% to 30%, particularly 0% to 25%, and especially 0% to 15%.

[0029] According to an advantageous embodiment of the invention, the polyetherimide-siloxane copolymer is a block copolymer of general formula (I).

[0030]

[0031] in

[0032] -R 1-6 Same or different and selected from:

[0033] о Substituted or unsubstituted saturated, unsaturated, or aromatic monocyclic rings having 5 to 30 carbon atoms

[0034] о Substituted or unsubstituted saturated, unsaturated, or aromatic polycyclic aromatic hydrocarbons having 5 to 30 carbon atoms

[0035] о Substituted or unsubstituted saturated hydrocarbons having 1 to 30 carbon atoms,

[0036] о Substituted or unsubstituted unsaturated hydrocarbons having 2 to 30 carbon atoms;

[0037] -V represents a tetravalent linker selected from the following groups.

[0038] о Substituted or unsubstituted saturated, unsaturated, or aromatic monocyclic and polycyclic rings having 5 to 50 carbon atoms

[0039] о Substituted or unsubstituted saturated hydrocarbons having 1 to 30 carbon atoms,

[0040] unsaturated hydrocarbons, whether substituted or unsubstituted, having 2 to 30 carbon atoms.

[0041] о and a linking group comprising any combination of at least one of the aforementioned groups;

[0042] -g ranges from 1 to 30, and

[0043] -d ranges from 2 to 20.

[0044] According to another advantageous embodiment of the invention, the copolymer may contain one or more additives. These may be, for example, one or more metal oxides, such as TiO2 and / or those having one of the following molecular formulas: Na8Al6Si6O 24 S4 and / or Na6Al6Si6O 2452. Other additives may be Fe2C3 and / or MnFe2O4 and / or non-conductive carbon-based fillers, such as industrial carbon black. If desired, the additive particles may be partially or completely, entirely or partially coated with SiO2.

[0045] In particular, these additives also inhibit oxidation, which allows for further improvement in the heat resistance or temperature index of the flat insulation materials produced from them.

[0046] For example, additives are incorporated into the production of blends.

[0047] Other additives, leveling agents, coloring pigments, quartz particles, etc., can be mixed into the blend and / or impregnating agent to produce an insulation system.

[0048] Here, "siloxane" basically refers to a compound having at least one -Si-O-Si unit, especially those forming a Si-O-Si backbone in polymers, as is common in silicones. For example, polydialkylsiloxanes, such as polydimethylsiloxane, or polydiarylsiloxanes, such as polydiphenylsiloxane, are simple forms of siloxanes.

[0049] Of course, there are also mixed forms of siloxanes, such as polyarylalkylsiloxanes.

[0050] Polyetherimide, or "PEI," refers to a known thermoplastic available in a variety of ways because of its high temperature resistance and classification as flame retardant. This is especially true because it exhibits very little smoke production even when burning. PEI possesses high strength, high electrical breakdown strength, low weight, and resistance to ultraviolet and gamma rays. In particular, PEI is used as... Commercially available.

[0051] According to an advantageous embodiment of the invention, polyetherimide is particularly used first to form copolymers with siloxanes, i.e., the monomers of polyetherimide and siloxane are cured together to form a polymer.

[0052] Secondly, regardless of the copolymer used, polyetherimide is used as a high-temperature thermoplastic material to mix the copolymer to form a blend according to one embodiment of the invention.

[0053] Blends (or polymer blends) are formed by simply mixing two components: a copolymer on one side and a high-temperature thermoplastic on the other. The properties of this blend, particularly its temperature resistance, do not conform to those of either the copolymer or the high-temperature thermoplastic. Blends in this sense are purely physical mixtures, with no new chemical bonds formed between the macromolecules.

[0054] Thermosetting plastics are used as impregnating resins to form synthetic resins for impregnating wound tape insulators and / or slots made of flat insulating materials according to the invention. Polyesters, formaldehyde, epoxides, phenolic varnishes, silicones, polyesterimides, polyurethanes, and any mixtures, blends, and copolymers of the above compounds can be used, for example. Impregnating resins for slot linings and / or wound tape insulators are generally known, especially from the aforementioned patent documents. Solid insulating materials are impregnated with these impregnating resins, and then the resin is cured to complete the insulation system.

[0055] Fillers can be added to impregnating resins or to blends of copolymers with high-temperature thermoplastics. In particular, silica nanoparticles have proven advantageous for increasing the silicon content and further improving the partial discharge resistance of insulation systems.

[0056] Polyetherimide-siloxane copolymer is marketed under the trade name "Siltem". TM "It can be seen that it has been successfully blended with thermoplastics to form blends, which were then used and tested. Siltem is an amorphous thermoplastic polyetherimide-siloxane copolymer that combines the temperature resistance of PEI with the flexibility of silicone elastomers. As a blend with high-temperature thermoplastics, especially with partially crystalline high-temperature thermoplastics, it exhibits good processability in film formation, for example, through conventional extrusion methods."

[0057] Figure 1 and 2 The surfaces of two specimens containing insulation systems are shown, each comprising a solid flat insulating material impregnated with a synthetic resin, which then cures after impregnation. Both figures show the specimens after electrical aging. Under the same conditions, Figure 1 The corrosion of the insulation system produced using pure polyetherimide is shown. Figure 2 The erosion of an insulation system produced using a blend of polyetherimide-siloxane copolymer and thermoplastic as a solid flat insulating material, according to one embodiment of the invention, is shown.

[0058] The standard test conditions for electrical aging as defined in IEC 60343 are as follows:

[0059] Voltage: 10kV

[0060] Atmosphere: 50% RH

[0061] Temperature: Room temperature approximately 23℃

[0062] Test duration: 100 hours

[0063] Flow rate: 1000 l * h -1

[0064] Figure 1 Below is a diagram, which shows that in Figure 1 In the following conditions, an insulation system containing pure PEI forms a circle around a centrally arranged conductor, wherein the erosion depth caused by partial discharge reaches up to 80 μm. Under the same conditions, an insulation system of the same manufacture (containing the polymer of the present invention as a solid insulating material, which in the test case was a commercial product) was tested, except for the solid insulating material. and / or STM 1600 (as a PEI-siloxane copolymer) Figure 2 The samples also showed perfectly circular aging, but with an erosion depth of only -1 μm to -8 μm.

[0065] Based on these tests, the present invention represents a quantum leap in insulation technology, as it eliminates for the first time the need for complex and expensive mica-containing insulation materials that require extensive manufacturing processes.

[0066] It has been shown that blends of copolymers with high-temperature thermoplastics result in significantly improved, and even almost complete, resistance to partial discharge compared to pure polyetherimide.

[0067] Due to its detected resistance to partial discharge and its properties suitable for use as a blend in film processing, this copolymer-thermoplastic blend, proposed for the first time as a mica alternative, is suitable as a flat insulating material, both for wound tape insulators and for flat materials such as slotted liners, particularly in engine applications, including traction machines, drive engines, and generators such as wind turbines. Its excellent tensile properties expand the design range—for example—of traction engines.

[0068] Therefore, the achievable objective is to produce channel liners containing meta-aramids and insulating tapes containing polyimide using flat insulating materials made from polyetherimide-siloxane copolymers according to the invention, without sacrificing the power density of the engine or generator. In particular, mica paper and / or mica tapes, which are particularly processable by planar extrusion, can be used in both insulation systems instead of mica paper and / or mica tapes, each comprising at least a carrier, such as mica on glass fabric, and a strip adhesive for connecting the mica sheets.

[0069] According to one embodiment of the invention, a film, for example, produced by planar extrusion, insulates coils and / or wires of, for example, the windings of an electric motor. These coils are then inserted into slots in a laminated iron core and impregnated with an impregnation resin, such as polyesterimide and / or silicone.

[0070] An insulation system according to one embodiment of the invention comprises, for example, a laminate having one or more films made of a polyetherimide-siloxane copolymer, and is further processed to bond with a carrier and / or a protective film—for example, with a meta-aramid or polyimide as the carrier material.

[0071] Here, "membrane" is understood to refer to a flat layer of material. A membrane is a layer, not a stack of layers. The wall thickness of a membrane is typically from 1 μm to 0.7 mm, for example, from 2 μm to 0.5 mm.

[0072] Conversely, a "laminate" is typically a stack of layers comprising one or more films or papers. Here, these layers may be stacked completely (i.e., all film layers) or partially (i.e., at least one layer having a fiber and / or network structure, such as a grid and / or statistical distribution). To form a laminate, it may also be sufficient to bond the film to a fabric or layup, such as a fiberglass layup.

[0073] Here, "laminate" is understood to mean a stack and / or composite of at least two layers or films, namely, at least one carrier and / or protective film and / or paper (which is made of, for example, meta-aramid or polyimide) and at least one film made of a thermoplastic-polymer blend.

[0074] Especially in the case of duct liners, such as those in electric motors, wind turbines, etc., a simple film made of copolymer-thermoplastic blends as a flat insulating material may tear. Therefore, it is better to use a laminate with a relatively tear-resistant film or paper (in which a blend of thermoplastic and copolymer is used) as the insulator.

[0075] According to another embodiment, the laminate is cut into strips and used in the insulation system, for example.

[0076] Therefore, the insulator for the slot of an electric motor can be protected along its entire length and / or additionally by a flat insulating material made of a polyetherimide-siloxane copolymer-high-temperature thermoplastic blend over a large film thickness and / or in the form of a laminate, for example, in combination with a slot liner, such as an aramid paper and / or a polyimide film.

[0077] The thickness of the flat insulating material made of the film present as a strip is, for example, 1 μm to 250 μm, particularly 20 μm to 220 μm, and very preferably 25 μm to 200 μm.

[0078] The thickness of the flat insulating material made from the membrane present as a groove liner is, for example, 70 μm to 500 μm, particularly 90 μm to 300 μm, and very preferably 100 μm to 450 μm.

[0079] In order to produce an insulation system, a winding made of a film (which may optionally be in the form of a laminate) is inserted into a slot, and the entire winding is impregnated with an impregnation resin made of a thermosetting plastic that is filled or unfilled, electrically insulating or conductive (as may be present when producing a corona protection system, such as an external corona protection device).

[0080] A particular advantage of using high-temperature thermoplastic copolymer blends in film form as flat insulating materials is, for example:

[0081] - The production of the entire insulation system can be significantly cheaper than that of mica-based flat insulation materials.

[0082] - Flat insulation materials can withstand heat loads up to approximately 170°C to 250°C—depending on the blending with high-temperature thermoplastics.

[0083] -Due to the proportion of siloxanes in the copolymer, the blend is also flexible and can therefore be used as a winding tape.

[0084] As tested, the blend withstands the required electric field strength persistently because discharges occurring at electric field strengths up to a maximum of 15 kV / mm (!) form a glassy protective layer upon impact with the siloxane or SiO2 nanoparticles, significantly increasing the lifespan of rotating electrical machines insulated with it. This glassy layer can be easily detected using REM analysis, and further elemental analysis can be performed using EDX to detect, for example, silicon in the copolymer, and...

[0085] -As per this instruction manual Figure 2 As shown, the blend is resistant to partial discharge, which leads to a significant increase in the electrical life of the insulation system.

[0086] This invention provides, for the first time, an alternative to mica, a barrier material conventionally used in insulation systems, such as the primary insulators of rotating electrical machines like engines and / or generators. This alternative is based on copolymers, particularly polyetherimide-siloxane copolymers, blends with high-temperature thermoplastics, which can be flattened, for example, by planar extrusion. Films are produced here, which are processed in film form or as laminates, as flat insulating materials or as tape cutters, and can be used in insulation systems as wound tape insulators and / or as channel liners.

Claims

1. An insulation system comprising a solid insulating material in the form of a flat insulating material and a synthetic resin, wherein the flat insulating material is in the form of a film, and wherein the flat insulating material is a blend of at least one copolymer of polyetherimide and siloxane with at least one high-temperature thermoplastic, and the synthetic resin is a thermosetting plastic, wherein the entire winding made of the film is impregnated therein and then cured.

2. The insulation system according to claim 1, wherein the copolymer of polyetherimide and siloxane is a block copolymer.

3. The insulation system according to any one of claims 1 or 2, wherein the copolymer has a siloxane ratio of 0.1% to 90% by weight, based on the total weight of the copolymer.

4. The insulation system according to any one of claims 1 or 2, wherein the copolymer contains an atomic proportion of 1% to 25% silicon atoms, based on all atoms in the copolymer.

5. The insulation system according to any one of claims 1 or 2, wherein the copolymer is formulated according to formula (I). in - R 1-6 Same or different and selected from: 〇 Substituted or unsubstituted saturated, unsaturated, or aromatic monocyclic rings having 5 to 30 carbon atoms 〇 Saturated, unsaturated, or aromatic polycyclic aromatic hydrocarbons with 5 to 30 carbon atoms, whether substituted or unsubstituted. 〇 Saturated hydrocarbons with 1 to 30 carbon atoms, whether substituted or unsubstituted. 〇 Unsaturated hydrocarbons with 2 to 30 carbon atoms, whether substituted or unsubstituted; - V represents a tetravalent linker selected from the following groups. 〇 Substituted or unsubstituted saturated, unsaturated, or aromatic monocyclic and polycyclic rings having 5 to 50 carbon atoms 〇 Saturated hydrocarbons with 1 to 30 carbon atoms, whether substituted or unsubstituted. 〇 Unsaturated hydrocarbons with 2 to 30 carbon atoms, whether substituted or unsubstituted. 〇 and a linking group comprising at least one of the aforementioned groups in any combination; - g is 1 to 30, and - d is 2 to 20.

6. The insulation system according to any one of claims 1 or 2, wherein at least one high-temperature thermoplastic is present in the blend in a partially crystalline form.

7. The insulation system according to any one of claims 1 or 2, wherein at least one high-temperature thermoplastic is selected from the following thermoplastics: polyamide-imide-PAI-, polysulfone-PSU-, poly(oxy-1,4-benzenesulfonyl-1,4-phenyl)-PESU-, polyphenylene sulfide-PPS-, polyaryletherketone-PAEK-, polyetheretherketone-PEEK-, polyphenylene ether-PPE-, polyoxymethylene-POM-, perfluoroalkoxy polymer-PFA-, polyvinylidene fluoride-PVDF-, polyetherketone-PEK-, polyetherketoneketone-PEKK-, polytetrafluoroethylene-PTFE-, polybenzimidazole-PBI- and / or polyetherimide-PEI-.

8. The insulation system of claim 7, wherein the polysulfone-PSU is polyphenylsulfone-PPSU or polyethersulfone-PES.

9. The insulation system according to any one of claims 1 or 2, wherein one or more oxidation-inhibiting additives are provided in the flat insulating material.

10. The insulation system according to any one of claims 1 or 2, wherein the product is traded under the name Siltem TM The available product is the copolymer.

11. The insulation system according to any one of claims 1 or 2, wherein the membrane is in the form of a laminate or in the form of a tape and / or a tape cut from a laminate.

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