Multiple parallel conductor for electrical machines and devices

Details Multiple parallel conductor for electrical machines and devices Multiple parallel conductor for electrical machines and devices

2000-08-11

2003-05-13

Donovan, Lincoln (Department: 2832)

Inductor devices

Coil formed of parallel connected conductors

C336S061000, C336S180000, C174S12000C

Reexamination Certificate

active

06563413

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a multiple parallel conductor for an electrical machine, especially for a transformer, comprising of a plurality of adjacent, preferably mutually insulated subconductors which are combined to form a bundle, and a method for producing such a multiple parallel conductor. Furthermore, the present invention relates to a winding for an electrical machine, especially a transformer comprising a higher-voltage and a lower-voltage winding, comprising of at least one multiple parallel conductor of the abovementioned type, wherein successive windings of the multiple parallel conductor or parallel-wound multiple parallel conductors are arranged axially and/or radially adjacently.
2. Discussion of Background Information
To improve the cooling of electrical conductors, multiple parallel conductors comprising a mesh-shaped wrapping are known. For example, a multiple parallel conductor consisting of a plurality of subconductors or transposed conductors which is taped with a wide-meshed woven ribbon or meshed ribbon of polyester or a glass-filament/polyester mixture having a mesh-size of at least 2 mm is described in International Publication WO95/30991 of the applicant. If necessary, the multiple parallel conductor and/or the woven or meshed ribbon is also impregnated with a partially crosslinked epoxy resin. Such a woven ribbon can be used for producing a solid compact conductor in which the subconductors are in direct contact with the cooling medium. Due to these greatly improved cooling characteristics, a more compact and cost-effective construction of electrical machines and devices becomes possible. If a multiple parallel conductor of this type is processed in such a manner that individual windings or parallel-wound multiple parallel conductors lie directly against one another, there is a risk that the enamel insulation of the subconductors becomes damaged due to friction and that this impairs the electrical characteristics of the winding. For this reason, a multiple parallel conductor of this type is processed in practice in such a manner that spacers are arranged between two adjacent multiple parallel conductors.
Furthermore, from U.S. Pat. No. 3,098,113, an electrical conductor is known which is surrounded completely by a major insulation which can be impregnated with oil and a partial insulation which is impermeable to liquid, to enable impregnation with oil but at least partially to prevent penetration by water. The partial insulation impermeable to liquid, in turn, is provided with a sheathing which can be impregnated with oil. Having regard to a compact and solid conductor, this type of design is disadvantageous since it requires double and triple insulating layers at least in sections. Furthermore, this conductor is characterized by comparatively poor cooling characteristics.
SUMMARY OF THE INVENTION
It is an aspect of the present invention to find a possibility, by further development of multiple parallel conductors of the type mentioned above, of creating windings having an even higher space factor, in which impairment of the electrical characteristics can be avoided and, nevertheless, good cooling characteristics are achieved. Furthermore, it is an aspect of the invention to specify a method for producing such a multiple parallel conductor and to create a possibility for producing windings comprising of at least one such multiple parallel conductor.
On the basis of the abovementioned multiple parallel conductor, this aspect is achieved, according to the invention, in that above the outer surfaces of the subconductor bundle, a flat protective insulation is provided which covers at least one surface section of the subconductor bundle and does not cover at least one further surface section of the subconductor bundle, the surface sections being arranged next to one another referred to the longitudinal direction of the multiple parallel conductor, and that thereabove a mesh-shaped sheathing, e.g. a meshed ribbon, a filament braiding or the like, is provided at least in sections. In a method of the type according to the invention, it is accordingly provided that a flat protective insulation covering at least one side surface but not the entire circumference of the subconductor bundle is placed onto the subconductor bundle and that the subconductor bundle together with the protective insulation is provided with a mesh-shaped sheathing. According to the invention, a winding comprising of at least one multiple parallel conductor according to the invention, in which successive windings of the multiple parallel conductor or parallel-wound multiple parallel conductors are arranged axially and/or radially adjacently, is characterized by the fact that at least one side face of the side faces, facing one another, of adjacent winding sections of the multiple parallel conductor is provided with flat protective insulation. In an embodiment of the winding according to the invention having a particularly high space factor, the side faces provided with a flat protective insulation are in direct contact with one another.
Due to the combination of a protective insulation with a mesh-shaped sheathing, both increased mechanical strength and higher dielectric strength are achieved, so that the individual multiple parallel conductors of a winding can be arranged directly above one another or next to one another without interposition of spacers, and without impairing the electrical characteristics. Due to the free accessibility of the surfaces, which are not in contact with one another, of the multiple parallel conductor to the cooling medium and the good cooling characteristics of a multiple parallel conductor provided with a mesh-shaped sheathing, adequate cooling of the conductor or, respectively, of the winding is ensured. The space factor and, consequently, the production costs for a winding can thus be further reduced, and the operational reliability further increased, by this solution according to the invention.
In a preferred embodiment of the multiple parallel conductor according to the invention, the protective insulation comprises one or more side faces and the edge areas, facing this side face or these side faces, respectively, of the adjacent side faces not provided with protective insulation and, if necessary, the edge areas between adjacent side faces provided with protective insulation. This provides for increased protection of the conductor in the area of the edges so that the dielectric strength can be further increased.
In a winding in which adjacent multiple parallel conductors are in contact with one another over two side faces, e.g. in a group of four, the protective insulation preferably covers at least two adjacent side faces of the multiple parallel conductor in order to provide for all-round protection of the multiple parallel conductor.
The flat protective insulation is preferably paper insulation which, due to its good insulation characteristics and the small space requirement, is excellently suitable for the purposes of the present invention.
A multiple parallel conductor for an electrical machine includes a plurality of adjacent subconductors combined to form a subconductor bundle having an outer surface with a plurality of contiguous surface sections arranged in a longitudinal direction, and a flat protective insulation covering at least one of the plurality of surface sections. At least one of the plurality of surface sections remains uncovered by the flat protective insulation covering. A mesh sheathing further covers the plurality of surface sections.
According to a feature of the invention, the electrical machine can be a transformer. Further, the subconductors may each be mutually insulated. The plurality of contiguous surface sections may have flat surfaces. Further, the mesh sheathing may include meshed ribbon or filament braiding. Moreover, the protective insulation covers a plurality of adjacent surface sections of the plurality of surface sections.
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