Corona Protection Tape for Electrical High-Voltage Machine

Abstract

The invention provides a corona shielding tape for use to form wound insulation by means of VPI impregnation with a pthalic anhydride-free impregnating epoxy resin. The shielding tape may comprise (1) a carrier tape comprised of a polymeric matrix comprising at least one polyvinyl alcohol derivative compound and having an electrically conductive or semi-conductive filler embedded therein, and (1) an adduct of one or more 1H-imidazole derivatives and one or more acrylates, or (2) a complex compound comprising (a) a metal salt selected from the group consisting of zinc, copper, iron, aluminum, and mixtures thereof, and (b) imidazole and/or pyrazole ligands.

Claims

1. A corona shielding tape for further processing to form wound insulation by means of VPI impregnation with an anhydride-free, impregnating resin, the shielding tape comprising: a carrier tape comprised of a polymeric matrix having an electrically conductive and/or semiconductive filler embedded therein, and at least one tape accelerator incorporated into the impregnating resin, wherein in that the polymeric matrix comprises at least one polyvinyl alcohol and the tape accelerator is selected from the group consisting of the compounds I to IV and VI, where R.sub.2 on IV is identical or nonidentical and R.sub.2═H, V: ##STR00006## (I) is an adduct of TMPTA and one or more 1H-imidazole derivatives, R is identical or nonidentical and is selected from the group consisting of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl and/or mono-, di-, tri-, tetra-, pentasubstituted phenyl, where the substituents on the phenyl radical R.sub.phenyl are identical or nonidentical and may be selected from the group consisting of alkyl (linear and branched), alkoxy, fluorine, chlorine, bromine, iodine, aldehyde, ketone, acid ester, acid amide, phosphonic acid derivative, sulfonic acid derivative and mixtures thereof; ##STR00007## (II) is an adduct of trimethylolpropane propoxylate triacrylate and 1H-imidazole derivatives, R is identical or nonidentical and is selected from the group consisting of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl and/or mono-, di-, tri-, tetra-, pentasubstituted phenyl, where the substituents R.sub.phenyl of the phenyl radical are identical or nonidentical and may be selected from the group consisting of alkyl (linear and branched), alkoxy, —F, —Cl, —Br, —I, aldehyde, ketone, acid ester, acid amide, phosphonic acid derivative, sulfonic acid derivative, and mixtures thereof; ##STR00008## ; (III) is an adduct of pentaerythritol tetraacrylate (PETA) and one or more 1H-imidazole derivatives, R is identical or nonidentical and is selected from the group consisting of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl and/or mono-, di, tri-, tetra-, pentasubstituted phenyl, where the substituents of the phenyl radical R.sub.phenyl are identical or nonidentical and selected from the group consisting of alkyl (linear and/or branched), alkoxy, fluorine, chlorine, bromine, iodine, aldehyde, ketone, acid ester, acid amide, phosphonic acid derivative, sulfonic acid derivative, and mixtures thereof; ##STR00009## where R.sub.2═H, V of the structure (IV) may be a hydrogen atom or the functional group (V) shown here; (IV) is an adduct of dipentaerythritol penta/hexaacrylate (DPHA) and one or more 1H-imidazole derivatives, R is identical or nonidentical and is selected from the group consisting of H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl and/or mono-, di-, tri-, tetra-, pentasubstituted phenyl, where the substituents on the phenyl radical R.sub.phenyl are identical or nonidentical and may be selected from the group consisting of alkyl (linear and branched), alkoxy, fluorine, chlorine, bromine, iodine, aldehyde, ketone, acid ester, acid amide, phosphonic acid derivative, sulfonic acid derivative, and mixtures thereof, and R2═H; and (VI) is a complex compound comprising a metal salt selected from the group consisting of zinc, copper, iron aluminum, and mixtures thereof, and imidazole and/or pyrazole ligands, derived from the structures VIa and VIb ##STR00010## where R1 is identical or nonidentical and R1 is selected from the group consisting of H-, alkyl-, aryl-, acyl-, cyanoalkyl-, hydroxyalkyl-, cyanoaryl-, hydroxyaryl, and mixtures thereof.

2. The corona shielding tape as claimed in claim 1, incorporating multiple tape accelerators.

3. The corona shielding tape as claimed in claim 2, wherein the accelerators are incorporated in the polymeric matrix and/or the carrier tape.

4. The corona shielding tape as claimed in claim 1, wherein the ligands for the complex salts in accordance with the structure VI are selected from the group of ligands consisting of 1,2-dimethylimidazole (CAS 1739-84-0), 1-decyl-2-methylimidazole, 1-butyl-2-methylimidazole, 1-butyl-2-phenylimidazole, 1H-2-methylimidazole (CAS No. 693-98-1), 1H-imidazole (CAS No. 288-32-4), 1H-2-ethylimidazole (CAS No. 1072-62-4), 1H-2-propylimidazole (CAS No. 50995-94-4), 1H-2-isopropylimidazole (CAS No. 36947-68-9), 1H-2-butylimidazole (CAS No. 50790-93-7), 1H-2-isobutylimidazole (CAS No. 61491-92-7), 1H-2-tert-butylimidazole (CAS No. 36947-69-0), 1H-4-tert-butylimidazole (CAS No. 21149-98-4), 1H-4(5)-methylimidazole (CAS No. 822-36-6), 1H-2-ethyl-4-methylimidazole (CAS No. 931-36-2), 1H-4-methyl-2-phenylimidazole (CAS No. 827-43-0), 1H-4-phenylimidazole (CAS No. 670-95-1), 1H-5-methyl-2-phenylimidazole-4-methanol (CAS No. 13682-32-1), 1H-2,4-dimethylimidazole (CAS No. 930-62-1), 4(5)-(hydroxymethyl)imidazole (CAS No. 822-55-9), 1H-3-phenylpyrazole (CAS No. 2458-26-6), 1H-5-methylpyrazole (no CAS No.), 1H-3,4-dimethylpyrazole (CAS No. 2820-37-3), 1H-3-tert-butylpyrazole (CAS No. 15802-80-9), 1H-4-ethylpyrazole (CAS No. 17072-38-7), 1H-pyrazole (CAS No. 288-3-1),and 1H-3,5-dimethylpyrazole (CAS No. 67-51-6).

5. The corona shielding tape as claimed in claim 1, wherein the accelerator is incorporated into the matrix in an amount in the range from 0.1 g/m.sup.2 to 15 g/m.sup.2.

6. The corona shielding tape as claimed in claim 1, wherein the filler embedded in the polymeric matrix comprises globular, planar, tubular filler particles and/or filler mixtures.

7. The corona shielding tape as claimed in claim 1, wherein the polymeric matrix comprises more than one polyvinyl alcohol.

8. The corona shielding tape as claimed in claim 1, wherein the polymeric matrix comprises at least one polyvinyl alcohol having crosslinked fractions.

9. The corona shielding tape as claimed in claim 1, further comprising priming.

10. The corona shielding tape as claimed in claim 1 comprising a weight of less than 150 g/m.sup.2.

11. The corona shielding tape as claimed in claim 1 wherein the carrier tape comprises a coating in an amount in the range from 20 g/m.sup.2 to 100 g/m.sup.2.

12. The corona shielding tape as claimed in claim 1, further comprising filler particles wherein the filler particles are present in the form of hollow bodies, solid particles, coated particles, core-shell particles, and mixtures thereof.

13. The corona shielding tape as claimed in claim 1, further comprising electrically conductive filler particles composed of particles selected from the group consisting of carbon black particles, graphite particles, carbon nanotube particles, silicon carbide particles, metal oxide particles and mixtures thereof.

14-15. (canceled)

16. A corona shielding tape for use to form wound insulation by means of VPI impregnation with a pthalic anhydride-free impregnating epoxy resin, the shielding tape comprising a carrier tape comprised of a polymeric matrix comprising at least one polyvinyl alcohol derivative compound having an electrically conductive or semi-conductive filler embedded therein, and at least one tape accelerator incorporated into the pthalic anhydride-free impregnating epoxy resin, the tape accelerator comprising an adduct of one or more 1H-imidazole derivatives and one or more acrylates selected from the group consisting of trimethylolpropane triacrylate, trimethylolpropane propoxylate triacrylate, pentaerythritol tetraacrylate and dipentaerythritol penta/hexaacrylate.

17. A corona shielding tape for use to form wound insulation by means of VPI impregnation with a pthalic anhydride-free impregnating epoxy resin, the shielding tape comprising a carrier tape comprised of a polymeric matrix comprising at least one polyvinyl alcohol derivative compound having an electrically conductive or semi-conductive filler embedded therein, and at least one tape accelerator incorporated into the pthalic anhydride-free impregnating epoxy resin, the tape accelerator comprising a complex compound comprising (i) a metal salt selected from the group consisting of zinc, copper, iron, aluminum salts, and mixtures thereof, and (ii) imidazole and/or pyrazole ligands.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0069] According to one advantageous embodiment of the invention, the carrier tape and/or the polymeric matrix incorporates at least one tape accelerator of the kind which is subject matter of the patent applications DE 102015214872, DE 102016223656.3 and/or DE 102016223662.8.

[0070] The at least one tape accelerator may be incorporated in the varnish, in other words in the polymeric matrix with filler and/or in pores in the carrier tape, and so may be available to the VPI impregnating resin.

[0071] The accelerator in the carrier tape is present, for example, in an amount in the range from 0.1 g/m.sup.2 to 15 g/m.sup.2, more particularly from 0.5 g/m.sup.2 to 10 g/m.sup.2, preferably in an amount of 2 g/m.sup.2 to 7 g/m.sup.2.

[0072] The incorporated tape accelerators here may be identical or nonidentical.

[0073] According to one advantageous embodiment of the invention, the VPI impregnating resin of the electrical machine is an acid anhydride-free, more particularly phthalic anhydride-free, epoxy-based resin, preferably at least one epoxy resin based on bisphenol A and/or bisphenol F diglycidyl ether and/or epoxy novalac. For example, at least one impregnating resin is present that is based on bisphenol A and/or bisphenol F diglycidyl ether and/or epoxy novolac.

[0074] The tape used to produce the insulating winding comprises at least one binder, generally polymeric matrix material, and planar fillers in at least one fraction according to material, shape, size, optionally comprising a coating.

[0075] According to one advantageous embodiment of the invention, the polymeric matrix comprises plural polyvinyl alcohol(s).

[0076] Polyvinyl alcohol with the CAS number 9002-89-5 and the empirical formula (—C.sub.2H.sub.4O—).sub.n for the repeating unit is a thermoplastic and takes the commercial form of a crystalline, white to yellowish polymer which is soluble in water.

[0077] In contrast to the majority of vinyl polymers, polyvinyl alcohol cannot be prepared by simple polymerization of the corresponding monomer. The ethenol monomer necessary for that purpose exists only in its tautomeric form as acetaldehyde. Polyvinyl alcohols are obtained by transesterification and/or by alkaline hydrolysis of polyvinyl acetate. The hydrolysis is readily controllable. It provides polyvinyl alcohol copolymers and various derivatives in which some of the hydroxyl groups have been replaced by groups of similar chemical reactivity such as siloxanes.

[0078] The degree of branching in polyvinyl alcohols is generally low, owing to chain transfers during the synthesis of polyvinyl acetate. The degree of polymerization is about 500 to 2500. Partially hydrolyzed grades of polyvinyl alcohol—called PVAL for short—with around 13% of polyvinyl acetate—PVAC for short—are readily water-soluble, the water-solubility decreasing as the degree of hydrolysis goes up.

[0079] According to one advantageous embodiment of the invention, the polymeric matrix in the tape comprises polyvinyl alcohol with crosslinked fractions.

[0080] According to one advantageous embodiment, the polymeric matrix in the tape comprises one or more polyvinyl alcohols crosslinked with an aldehyde-modified melamine.

[0081] According to one advantageous embodiment of the invention, the polymeric matrix comprises at least one polymeric binder which is a polyvinyl alcohol having a degree of hydrolysis of at least 80 mol %, more particularly at least 85 mol %, and preferably of at least 87 or more mol %.

[0082] According to a further advantageous embodiment of the invention, the polymeric matrix comprises at least one polyvinyl alcohol in which the hydroxyl groups of the polyvinyl alcohol are substituted at least partly by siloxane groups.

[0083] According to one advantageous embodiment of the invention, the electrically conductive filler primarily comprises components such as, for example, a carbon modification—preferably in the form of carbon black, graphite and/or carbon nanotubes.

[0084] According to a further advantageous embodiment of the invention, the electrically conductive filler comprises a silicon carbide, more particularly a doped silicon carbide. According to a further advantageous embodiment of the invention, the electrically conductive filler comprises particles which are at least partly composed of metal oxide, more particularly of a mixed oxide.

[0085] A metal oxide refers presently to a compound formed between a metal and oxygen, the formal—that is, simplified—charge of the oxygen in the compound being negative 2. Fundamentally, the oxygen in the compound is the electronegative partner—hence the designation “oxide”.

[0086] A mixed oxide—MOX for short—refers, correspondingly, to a substance in which there is more than one metal cation in an oxidic compound—in other words, for example, titanium aluminum oxide or iron nickel oxide or the like.

[0087] According to one advantageous embodiment of the invention, a filler is used which has a coating composed of a doped tin oxide and/or a doped titanium oxide and/or which consists of a doped tin oxide and/or titanium oxide.

[0088] The filler particles may take the form of hollow bodies, solid particles, coated particles, and/or core-shell particles.

[0089] According to one advantageous embodiment of the invention, the electrically conductive filler makes up at least 45% by weight of the parts by mass of filler/binder which form the carrier tape.

[0090] The carrier tape is used in order to produce the wound insulation. The carrier tape comprises at least one fraction of platelet-shaped particles, which are held together by a binder and thus form the tape. To adjust the electrical resistance, it may be advantageous here to add spherical, i.e., globular, filler particles to the fraction of platelet-shaped filler particles.

[0091] According to one advantageous embodiment of the invention, the carrier tape has a basis weight of <100 g/m.sup.2.

[0092] According to one advantageous embodiment, the carrier tape comprises reinforcing fibers, in the form, for example, of a woven fabric and/or of a fiber assembly, into which the polymeric matrix with the electrically conductive filler is incorporated and/or with which it is bonded by the binder.

[0093] These reinforcing fibers are, for example, glass fibers and/or polyethylene terephthalate—PET—fibers.

[0094] According to one advantageous embodiment, the carrier tape is coated with priming. In that case it is especially advantageous if the carrier tape is coated with priming of up to 5 g/m2.

[0095] It has proven in particular to be advantageous if the priming of the carrier tape comprises polyvinyl alcohol, epoxy functionalities and/or amine functionalities.

[0096] Priming refers presently to a priming coating which improves the reinforcing fibers and/or the carrier tape/woven fabric in its cut resistance and prepares them for wetting with the polymeric matrix.

[0097] According to one advantageous embodiment of the invention, the amount of the coating of the carrier tape with the polymeric matrix that comprises the at least one fraction of electrically conductive filler and/or else, optionally, the at least one tape accelerator is in the range from 20 g/m.sup.2 to 100 g/m.sup.2, more particularly in the range from 20 g/m.sup.2, to 60 g/m.sup.2, very preferably in the range from 30 g/m.sup.2 to 45 g/m.sup.2.

[0098] According to one advantageous embodiment of the invention, the corona shielding tape is used for producing an external corona shielding system and/or an internal potential control system and/or a terminal corona shielding system.

[0099] It is advantageous here if the square resistance and/or sheet resistance of an external corona shielding system and/or of an internal potential control system, produced by means of a corona shielding tape according to the present invention, is in the range from 0.01 kohm to 100 kohm, as measured at a field strength of 1 V/mm.

[0100] In particular, the square and/or sheet resistance values of an internal potential control of this kind are preferably in the range from 0.01 kohm to 10 kohm, preferably in the range from 0.05 to 7 kohm and more preferably in the range from 2.5 to 5 kohm, and/or the square resistance values of an external corona shield of this kind are in the range from 0.1 to 100 kohm, more particularly from 0.1 kohm to 90 kohm and very preferably in the range from 5 kohm to 50 kohm, in each case as measured at a field strength of 1 V/mm.

[0101] In the case of the production of a terminal corona shield by means of a corona shielding tape according to the present invention, it is advantageous if the sheet resistance is in the range from 1×10.sup.8 to 1×10.sup.12, more particularly in the range from 1×10.sup.8 to 1×10.sup.13 ohms at a field strength of 1 V/mm.

[0102] The invention relates to a corona shielding tape for an electrical high-voltage machine, with phthalic anhydride-free epoxy resins. The corona shielding tape presented here for the first time is tailored with its components, especially with the connecting polymeric matrix and the incorporated tape accelerator, to the new phthalic anhydride-free, epoxy resin-based VPI impregnating resins. In the polymeric matrix there is also at least a fraction of polyvinyl alcohol.