Electric Insulation Material and/or Impregnation Resin for a Wrapping Tape Insulation for a Medium- and/or High-Voltage Machine

Abstract

Various embodiments include an insulation material and/or impregnation resin for a wrapping tape insulation, comprising: a base resin curing to a thermoset; and a curing agent. The base resin comprises a siloxane-containing compound forming a —SiR.sub.2—O— backbone in the thermoset.

Claims

1. An insulation material and/or impregnation resin for a wrapping tape insulation, comprising: a base resin curing to a thermoset; and a curing agent; wherein the base resin comprises a siloxane-containing compound forming a —SiR.sub.2—O— backbone in the thermoset.

2. The insulation material and/or impregnation resin as claimed in claim 1, wherein the siloxane-containing compounds is present in monomeric form.

3. The insulation material and/or impregnation resin as claimed in claim 1, wherein the siloxane-containing compound is present in oligomeric form.

4. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises a compound that forms a —SiR.sub.2—O— backbone at least to an extent of 10 mol %.

5. The insulation material and/or impregnation resin as claimed in claim 1, wherein the curing agent comprises a siloxane-containing component forming a —SiR.sub.2—O— backbone bearing corresponding functionalities suitable for curing of the base resin.

6. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises compounds forming a —SiR.sub.2—O— backbone and compounds forming a —CR.sub.2— backbone in a stoichiometric ratio of 1:4 to 1:8.

7. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises compounds forming a —CR.sub.2— backbone in a greater molar percentage than compounds that form a —SiR.sub.2—O— backbone.

8. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises a glycidyl- and/or glycidoxy-functionalized compound forming a —SiR.sub.2—O— backbone.

9. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises at least one of a glycidyl ether compound or a novolak derivative.

10. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises a cycloaliphatic epoxy resin.

11. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises an epoxy-terminated aryl- and/or alkylsiloxane forming a —SiR.sub.2—O— backbone.

12. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises 1,3-bis(3-glycidyloxyalkyltetramethyldisiloxane) forming a —SiR.sub.2—O— backbone.

13. The insulation material and/or impregnation resin as claimed in claim 1, wherein the base resin comprises 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane forming a —SiR.sub.2—O— backbone.

14. An insulation system, especially for a medium- and/or high-voltage machine, comprising: a base resin cured to a thermoset; and a curing agent used to cure the base resin; wherein the thermoset comprises a —SiR.sub.2—O— backbone formed by a siloxane-containing compound in the base resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows the comparison of the erosion volumes after electrical exposure at 10 kV.

[0028] FIG. 2 shows a substitution of the bisphenol A diglycidyl ether (BADGE) for a SiR.sub.2—O-containing product “Silres®” and/or Silikoftal with an at least difunctionalized, glycidoxy-terminated phenyldimethylsiloxane monomer.

[0029] FIG. 3 shows the storage moduli and derived glass transition temperatures as a function of the degree of substitution of epoxy resin component for a compound that forms a —SiR.sub.2—O— backbone, such as “Silres®”.

DETAILED DESCRIPTION

[0030] The present disclosure describes insulation materials and/or impregnation resins for a wrapping tape insulation, comprising at least a base resin, a curing agent and optionally additives, characterized in that at least some of the base resin that cures to give a thermoset for the insulation system is a siloxane-containing compound that forms a —SiR.sub.2—O— backbone in the thermoset. Various embodiments may include insulation systems, for example an insulation system for a rotating electrical machine, especially a medium- or high-voltage machine, producible using the insulation material described herein.

[0031] “R” here represents all kinds of organic radicals suitable for curing and/or crosslinking to give an insulant usable for an insulation system. More particularly, R represents -aryl, -alkyl, -heterocycles, nitrogen-, oxygen- and/or sulfur-substituted aryls and/or alkyls.

[0032] More particularly, R may be the same or different and may represent the following groups: [0033] alkyl, for example -methyl, -propyl, -isopropyl, -butyl, -isobutyl, -tert-butyl, -pentyl, -isopentyl, -cyclopentyl and all other analogs up to dodecyl, i.e. the homolog having 12 carbon atoms; [0034] aryl, for example: benzyl-, benzoyl-, biphenyl-, tolyl-, xylenes etc., especially, for example, all aryl radicals whose structure meets Huckel's definition of aromaticity, [0035] heterocycles: especially sulfur-containing heterocycles such as thiophene, tetrahydrothiophene, 1,4-thioxane and homologs and/or derivatives thereof, [0036] oxygen-containing heterocycles, for example dioxanes [0037] nitrogen-containing heterocycles, for example —CN, —CNO, —CNS, —N3 (azide) etc. [0038] sulfur-substituted aryls and/or alkyls: e.g. thiophene, but also thiols.

[0039] The Hückel rule for aromatic compounds relates to the correlation that planar, cyclically through-conjugated molecules comprising a number of Π electrons that can be represented in the form of 4n+2 possess exceptional stability which is also referred to as aromaticity.

[0040] In some embodiments, the resin comprises, as well as the component in monomeric and/or oligomeric form which has been functionalized for polymerization and has a —SiR.sub.2—O— backbone, also at least one monomeric or oligomeric resin component that has been functionalized for polymerization and has a backbone comprising hydrocarbon units, i.e. (—CR.sub.2—). Suitable examples for this purpose are epoxy-functionalized components such as bisphenol F diglycidyl ether (BFDGE) or bisphenol A diglycidyl ether (BADGE), polyurethane and mixtures thereof. Some embodiments include epoxy resins based on bisphenol F diglycidyl ether (BFDGE), bisphenol A diglycidyl ether (BADGE) or mixtures thereof.

[0041] In some embodiments, the monomeric or oligomeric component that has been functionalized for polymerization and has a —SiR.sub.2—O— backbone is combined with one or more compounds selected from the group of the following compounds to give the base resin: undistilled and/or distilled, optionally reactively diluted bisphenol A diglycidyl ether, undistilled and/or distilled, optionally reactively diluted bisphenol F diglycidyl ether, hydrogenated bisphenol A diglycidyl ether and/or hydrogenated bisphenol F diglycidyl ether, pure and/or solvent-diluted epoxy novolak and/or epoxyphenol novolak, cycloaliphatic epoxy resins such as 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexyl-carboxylate, e.g. CY179, ERL-4221; Celloxide 2021P, bis(3,4-epoxycyclohexylmethyl) adipate, e.g. ERL-4299; Celloxide 2081, vinylcyclohexene diepoxide, e.g. ERL-4206; Celloxide 2000, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanemeta-dioxane, e.g. ERL-4234; diglycidyl hexahydrophthalate, e.g. CY184, EPalloy 5200; tetrahydrophthalic acid diglycidyl ether, e.g. CY192; glycidated amino resins (N,N-diglycidyl-para-glycidyloxyaniline, e.g. MY0500, MY0510), N,N-diglycidyl-meta-glycidyloxyaniline, e.g. MY0600, MY0610, N,N,N′,N′-tetraglycidyl-4,4′-methylenedianiline, e.g. MY720, MY721, MY725, and any mixtures of the aforementioned compounds.

[0042] In some embodiments, monomeric or oligomeric components have been functionalized for polymerization and have a —SiR.sub.2—O— backbone are glycidyl-based and/or epoxy-terminated aryl- and/or alkylsiloxanes, for example glycidoxy-functionalized, especially glycidoxy-terminated, siloxanes. In some embodiments, there is a siloxane such as 1,3-bis(3-glycidyloxypropyl)tetramethyl-disiloxane, DGTMS or glycidoxy-terminated phenyldimethyl-siloxane in monomeric and/or oligomeric form, and in any desired mixtures and/or in the form of derivatives. It has been found that at least difunctionalized siloxane monomers usable for production of thermosets are suitable here.

[0043] In some embodiments, curing agents include cationic and anionic curing catalysts, for example organic salts, such as organic ammonium, sulfonium, iodonium, phosphonium and/or imidazolium salts, and amines such as tertiary amines, pyrazoles and/or imidazole compounds. Examples here include 4,5-dihydroxymethyl-2-phenyl-imidazole and/or 2-phenyl-4-methyl-5-hydroxymethylimidazole. It is alternatively possible to use compounds containing oxirane groups, for example glycidyl ethers, as curing agent.

[0044] Acid anhydrides are also conventionally used successfully as curing agent in the insulation materials. However, their toxicology has now become a matter of some controversy. In some embodiments, the carbon-based curing agent may be replaced even entirely or partly by siloxane-based curing agents having the same functionalities.

[0045] In some embodiments, the insulation material and/or impregnation resin for a wrapping tape insulation also includes additives such as sintering aids, reactive accelerators and/or fillers that may be present either as nanoparticles or as filler particles in the micrometer range. In some embodiments, in the insulant comprising the cured base resin, a ratio of —SiR.sub.2—O— backbone to (—CR.sub.2—) backbone such as 1:8 to 1:4 may be used, meaning that, in the insulation material in question, the hydrocarbon-based compounds are present in 4 to 8 times the quantity of the siloxane-based compounds. The proportions are based here on the stoichiometry, i.e. are molar percentages.

[0046] In some embodiments, the siloxane-containing component is thus present in an amount of 10 to 50 mol % in the base resin of the insulation material. In some embodiments, the amount of siloxane-containing component in the base resin is not more than 20 mol %, not more than 18 mol % and/or not more than 15 mol %. The partial discharge resistance of the insulant is increased quite sharply by the presence of a certain amount of monomers or oligomers that form SiR.sub.2—O— in the base resin.

[0047] FIG. 1 shows the comparison of the erosion volumes after electrical exposure at 10 kV. Plotted on the x axis is the proportion of SiR.sub.2—O-forming compound in the base resin; the baseline here is at 100% base resin that forms (—CR.sub.2—) backbone. It is apparent that, between 0 and 10 mol % of “exchanged —CR.sub.2— compound”, the erosion volume plotted on the y axis drops abruptly from about 37 to 6. This means that the erosion volume here declines virtually by a factor of 9. In the case of 20 mol % of SiR.sub.2—O-forming compound with 80 mol % of —CR.sub.2— compound in the base resin, a minimum arises, which persists up to about 30 mol % of SiR.sub.2—O-forming compound.

[0048] In the embodiment shown, the conventional resin component was exchanged for a —SiR.sub.2—O-containing monomer by using 1,3-bis(3-glycidyloxypropyl)tetramethyldisiloxane. For the measurement, the cured insulant was exposed to electrical discharges in a controlled and defined manner. After a particular period of time, the volumes eroded were scanned by a laser and the eroded volume—or the erosion depth—was thus evaluated. The exposure parameters were as follows: temperature: room temperature; atmosphere: air, 50% RH; duration: 100 h; voltage: 10 kV.

[0049] In some embodiments, even in the case of low substitution of the conventional epoxy resin, such as of the bisphenol A diglycidyl ether (BADGE) for a —SiR.sub.2—O-containing monomer, on completion of curing, a distinct increase in partial discharge resistance can be achieved, which results in a distinct reduction in volume eroded.

[0050] The same phenomenon was observed in the case of substitution of the bisphenol A diglycidyl ether (BADGE) for a SiR.sub.2—O-containing product “Silres®” and/or Silikoftal with an at least difunctionalized, glycidoxy-terminated phenyldimethylsiloxane monomer, as shown in FIG. 2.

[0051] In both figures, an optimum in the reduced erosion volume is apparent in the case of substitution of the compound that forms —CR.sub.2— backbone of 20 mol % to 30 mol % for the compound that forms —SiR.sub.2—O-containing backbone. However, the effect of the substitution of the compound that forms —CR.sub.2— backbone in the cured insulant is a deterioration in the mechanical properties, and so there should be as little substitution as possible and as much as necessary.

[0052] In some embodiments, therefore, up to 10 mol %, up to 15 mol % and/or up to 20 mol % of the compound(s) in the base resin that form a —CR.sub.2— backbone are substituted for correspondingly functionalized compounds that form a —SiR.sub.2—O— backbone. Within this range, the mechanical properties of the cured insulant are indeed of comparable quality to those of the insulant without compounds that form a —SiR.sub.2—O— backbone. More particularly, the resulting glass transition temperatures and the storage moduli of the substituted insulant are almost identical to those of the conventional insulant without substitutions.

[0053] FIG. 3 shows the storage moduli and derived glass transition temperatures as a function of the degree of substitution of epoxy resin component for a compound that forms a —SiR.sub.2—O— backbone, such as “Silres®”. It is apparent that the highest glass transition temperature is measured in the case of 25% substitution.

[0054] In some embodiments, an insulation material and/or impregnation resin for a wrapping tape insulation, by virtue of presence of compounds in the cured resin that form a —SiR.sub.2—O— backbone, shows a distinct increase in partial discharge resistance. As a result, it is possible to drastically reduce the thickness of the insulation system, i.e., for example, by up to 20%. This results in various advantageous options for product development. It is firstly possible, in the case of conductors of the same thickness, to reduce the extent, weight and costs of the insulated conductors. Secondly, it is possible to fill the space saved with increased conductor thickness and hence increase the power per unit mass of the electrical machine.

[0055] At present, conventional insulation systems for high-voltage machines are designed to withstand sustained operating field strengths of 3.5 kV/mm for at least 20 years. With the insulation materials presented here, it would be possible to significantly increase these operating field strengths to up to 4.5 kV/mm for similarly long lifetimes.