An assembly and a method for manufacturing an insulation layer of an electrical conductor are presented. The electrical conductor is enclosed in a cavity of a mold. Spacers embedded into holes of the mold are movable into the cavity for holding the electrical conductor in the cavity to maintain a gap between the electrical conductor and surface of the cavity. Distance of the gap is defined by thickness of the insulation layer. Spacers are movable into the holes of the mold from the cavity to maintain even surface of the cavity. Insulation compound fills entire gap and is cured to form the insulation layer having homogenous thickness.

A prepreg mica tape includes: a backing material (3); a boron nitride-containing layer (1) that is provided on or above one surface of the backing material (3) and that includes a boron nitride particle (5) and a first resin (4); and a mica-containing layer (2) that is provided on or above the surface of the backing material (3) on which the boron nitride-containing layer (1) is provided and that includes mica (6) and a second resin (4).

A prepreg mica tape includes: a backing material (3); a boron nitride-containing layer (1) that is provided on or above one surface of the backing material (3) and that includes a boron nitride particle (5) and a first resin (4); and a mica-containing layer (2) that is provided on or above the surface of the backing material (3) on which the boron nitride-containing layer (1) is provided and that includes mica (6) and a second resin (4).

Disclosed is an anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises: (A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises a complex of boron trihalogenide with an amine of the formula

BX.sub.3.Math.NR.sup.1R.sup.2R.sup.3 or R.sup.1R.sup.2NANR.sup.1R.sup.2, wherein X denotes halogen, R.sup.1, R.sup.2 and R.sup.3 are each independently of the others hydrogen, C.sub.1-C.sub.12alkyl, C.sub.5-C.sub.30aryl, C.sub.6-C.sub.36aralkyl or C.sub.6-C.sub.14cycloalkyl, which can be unsubstituted or substituted by one or more C.sub.1-C.sub.12alkyl groups, A is a bivalent aliphatic aromatic or cycloaliphatic radical; (B) a thermally curable bath formulation for the vacuum pressure impregnation comprising bisphenol A diglycidyl ether and optionally bisphenol F diglycidyl ether, which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

Disclosed is an anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises: (A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises a complex of boron trihalogenide with an amine of the formula

BX.sub.3.Math.NR.sup.1R.sup.2R.sup.3 or R.sup.1R.sup.2NANR.sup.1R.sup.2, wherein X denotes halogen, R.sup.1, R.sup.2 and R.sup.3 are each independently of the others hydrogen, C.sub.1-C.sub.12alkyl, C.sub.5-C.sub.30aryl, C.sub.6-C.sub.36aralkyl or C.sub.6-C.sub.14cycloalkyl, which can be unsubstituted or substituted by one or more C.sub.1-C.sub.12alkyl groups, A is a bivalent aliphatic aromatic or cycloaliphatic radical; (B) a thermally curable bath formulation for the vacuum pressure impregnation comprising bisphenol A diglycidyl ether and optionally bisphenol F diglycidyl ether, which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

An electric wire includes a metal conductor, a heat stable tape, wherein the tape is in direct contact with the conductor, wherein the tape can withstand temperatures of at least about 1850 F., a high temperature fiberglass layer, wherein the fiberglass layer is in direct contact with the tape, and an insulating sheath around the fiberglass layer, wherein the wire has no conduit protection.

Disclosed is an anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises:

(A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises one or more thermally activatable sulfonium salt initiators for the homopolymerisation of the epoxy resins present in said said thermally curable epoxy resin formulation or a mixture thereof in an amount sufficient to homopolymerize the epoxy resin taken up by the mica paper or mica tape and the construction part of the engine during the vacuum pressure impregnation step;
(B) a thermally curable bath formulation for the vacuum pressure impregnation comprising (i) a polyglycidyl ether or a mixture thereof, and (ii) a cycloaliphatic epoxy resin comprising at least two epoxy groups, which are fused to a cycloaliphatic ring, or a mixture thereof,
which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

Disclosed is an anhydride-free insulation system for current-carrying construction parts of an electric engine which comprises:

(A) a mica paper or mica tape for wrapping parts of said electric engine that are potentially current-carrying during operation of the engine, which mica paper or mica tape is impregnable via vacuum pressure impregnation with a thermally curable epoxy resin formulation and comprises one or more thermally activatable sulfonium salt initiators for the homopolymerisation of the epoxy resins present in said said thermally curable epoxy resin formulation or a mixture thereof in an amount sufficient to homopolymerize the epoxy resin taken up by the mica paper or mica tape and the construction part of the engine during the vacuum pressure impregnation step;
(B) a thermally curable bath formulation for the vacuum pressure impregnation comprising (i) a polyglycidyl ether or a mixture thereof, and (ii) a cycloaliphatic epoxy resin comprising at least two epoxy groups, which are fused to a cycloaliphatic ring, or a mixture thereof,
which formulation is substantially or, preferably, entirely free of thermally activatable curing initiators for the epoxy resin formulation.

A coil for a rotating electrical machine, the coil comprising a coil conductor and an insulating layer that is disposed around an outer periphery of the coil conductor, the insulating layer comprising a mica tape, the mica tape comprising a mica layer including mica and a backing layer including a backing material, the mica comprising mica pieces having a particle size of 2.8 mm or more, as measured by a JIS standard sieve, at a proportion of less than 45% by mass of a total of the mica pieces that are obtained from the mica layer being separated from the backing layer.

A coil for a rotating electrical machine, the coil comprising a coil conductor and an insulating layer that is disposed around an outer periphery of the coil conductor, the insulating layer comprising a mica tape, the mica tape comprising a mica layer including mica and a backing layer including a backing material, the mica comprising mica pieces having a particle size of 2.8 mm or more, as measured by a JIS standard sieve, at a proportion of less than 45% by mass of a total of the mica pieces that are obtained from the mica layer being separated from the backing layer.