Abstract
A core for a transformer includes a multiplicity of bent metal sheets that are all connected to form a structure which surrounds a core opening and forms the core. The sheet ends of each of the metal sheet do not touch one another within the core. The metal sheets together with the core form at least one air gap at the respective sheet ends within the core or at a periphery of the core. The core is impregnated or coated, at least at the sheet ends of the metal sheets, with a lacquer or coating that contains magnetic particles. The impregnation or coating fills at least the air gaps at the sheet ends of the metal sheets. A method for producing a transformer having a core is also provided.
Claims
1-12. (canceled)
13. A core for a transformer, the core comprising: a multiplicity of bent metal sheets being bonded together to form a structure surrounding a core opening and forming the core; said metal sheets each having sheet ends not touching one another within the core, causing the core with said metal sheets to form at least one air gap at said respective sheet ends within the core or at a periphery of the core; and a lacquer containing magnetic particles, said lacquer impregnating or coating the core at least at said sheet ends of said metal sheets and said impregnated or coated lacquer filling at least said air gaps at said sheet ends of said metal sheets.
14. The core according to claim 13, wherein said lacquer containing said magnetic particles entirely impregnates or coats the core.
15. The core according to claim 13, wherein said magnetic particles are superparamagnetic iron oxide nanoparticles.
16. The core according to claim 13, wherein said lacquer is a polyurethane lacquer.
17. The core according to claim 13, wherein said lacquer is a water-based lacquer.
18. The core according to claim 13, wherein: said metal sheets are U-shaped and have legs and segments interconnecting said legs; and said U-shaped metal sheets are pushed into one another with said legs of each of said U-shaped metal sheets being at least partially in contact with a leg of another respective one of said U-shaped metal sheets and with said segments positioned opposite one another.
19. The core according to claim 13, wherein: said metal sheets are each bent around said core opening; said metal sheets are each interrupted at one respective location by a respective one of said air gaps; and said sheet ends are aligned opposite one another at said respective air gap.
20. The core according to claim 13, wherein the core is a wound core.
21. The core according to claim 13, wherein the core is a stacked core.
22. A transformer, comprising a core according to claim 13.
23. A method for manufacturing a transformer including a multiplicity of bent metal sheets being bonded together to form a structure surrounding a core opening and forming the core, each of the metal sheets having sheet ends not touching one another within the bonded core, causing the core with the metal sheets to form at least one air gap at the respective sheet ends within the core or at a periphery of the core, the method comprising: passing individual metal sheets through at least one transformer winding of the transformer; bonding the individual metal sheets to create the bonded core within the transformer; and impregnating or coating the sheet ends of the metal sheets with a lacquer containing magnetic particles until filling the air gaps at the sheet ends of the metal sheets with the lacquer.
24. The method according to claim 23, which further comprises spraying the lacquer on to the sheet ends.
Description
[0022] Various transformer cores are shown by way of example in the figures. The filling of the air gaps is illustrated schematically, here:
[0023] FIG. 1 shows a wound core of the Unicore single type;
[0024] FIG. 2 shows a wound core of the Unicore duo type;
[0025] FIG. 3 shows a stacked core;
[0026] FIG. 4 shows an Evans-core wound core combination of Unicore cores;
[0027] FIG. 5 shows single and multi-phase transformers with wound cores;
[0028] FIG. 6 shows a schematic illustration of the filling of the air gap and the insulation.
[0029] FIG. 1 shows a perspective view of an opened, not completely assembled core 3 according to the invention of the Unicore single type 7. The metal sheets 1 form the core 3 that is wound around a core opening 4 for a transformer winding. In the assembled state of the core 3, the two sheet ends 2 of a metal sheet 1 butt against one another with a small air gap 5. A filling of the air gap 5 with magnetic particles reduces the magnetic resistance in the respective sheet winding. The sheets 1 of the core 3 are thus each bent around the core opening 4, wherein the sheets 1 are each interrupted at one location by an air gap 5, in such a way that at this air gap 5 the sheet ends 2 are arranged aligned lying opposite one another. Expressed in other words, the sheets 1 are C-shaped in this exemplary embodiment. Described yet again in other words, the sheets 1 each have the shape of a loop interrupted at one location.
[0030] FIG. 2 shows a perspective view of a disassembled core 3 according to the invention of the Unicore duo type 8. The sheets 1 form the halves of the core 3 that are pushed together around the core opening 4 for a transformer winding. In the assembled state of the core 3, each of the sheet ends 2 of a metal sheet 1 from one half butt with a small air gap 5 against the sheet ends 2 of metal sheets 1 from the other half lying opposite (the regions marked in FIG. 2 as air gap 5 identify those regions of the core halves in which the air gaps 5 result after the core halves have been brought together). With this core type, two gaps 5 are thus present at each sheet winding when in the assembled state. A filling of the air gap 5 with magnetic particles reduces the magnetic resistance in the respective sheet winding. Expressed in other words, the core 3 in this exemplary embodiment is composed of essentially U-shaped metal sheets 1 which, when the core is in its fully assembled state, are pushed in between one another in such a way that the legs of a U-shaped metal sheet 1 are each at least partially in contact with a leg of another U-shaped sheet 1, wherein the segments that bond the legs of these two metal sheets 1 are positioned lying opposite one another.
[0031] A stacked core 9 according to the invention is illustrated schematically in FIG. 3. The core 3, consisting of two halves, forms a core opening 4 for a transformer winding. The core 3 has a plurality of metal sheets 1 stacked on top of one another, whose sheet ends 2 each meet the sheet ends 2 of the other part of the core 3. Thus, when the core 3 is assembled, two air gaps 5 again form, which can be filled with magnetic particles (the regions marked in FIG. 5 as air gap 5 identify those regions of the core halves in which the air gaps 5 result after the core halves have been brought together). With this type of core again, the magnetic resistance of the transformer is reduced and the efficiency increased through the impregnation or coating described.
[0032] FIG. 4 shows a perspective view of an assembled wound core combination that is identified as an Evans core, i.e. as the Evans core 10. The Evans core comprises a plurality of Unicore cores. The two inner wound cores have the core openings 4 for transformer windings. The outer wound core 11 is looped around the two inner wound cores 12. All the wound cores in this core combination consist of one of the core types referred to above, whose efficiency is increased through the impregnation with magnetic particles.
[0033] Various combinations of core 3 are shown in FIG. 5. In the first illustration, a transformer winding 13 is located on the core 3. In the second illustration, the transformer winding 13 is looped around two cores 3. In the third illustration, a three-phase transformer with four cores 3 is shown, wherein each transformer winding 13 is looped around two cores 3. In all combinations, the cores 3 can be impregnated in accordance with the embodiment described here, and the field of application of the respective transformer thereby extended.
[0034] FIG. 6 shows a schematic cross-sectional illustration through the core 3 according to the invention shown in FIG. 1. The filling of the air gap of this core 3 is shown in particular in FIG. 6. The metal sheets 1 butt with their sheet ends 2 against one another, whereby an air gap 5 forms in each case. These air gaps 5 are filled with the lacquer 6 that contains the magnetic particles. The filled air gaps 5 thus have a lower magnetic resistance, and the no-load losses are thus also reduced. The outer side of the core 3 is, furthermore, impregnated with the lacquer 6 (not shown in FIG. 6) and thereby protects the core 3 against the influence of weather. Such a core 3 is thus in particular advantageously usable with dry transformer products.
[0035] Although the invention has been illustrated and described in detail more closely through preferred exemplary embodiments, the invention is not restricted by the disclosed examples, and other variations can be derived from this by the expert without leaving the protective scope of the invention.
LIST OF REFERENCE SIGNS
[0036] 1 Metal sheet
[0037] 2 Sheet end
[0038] 3 Core
[0039] 4 Core opening
[0040] 5 Air gap
[0041] 6 Lacquer
[0042] 7 Unicore single
[0043] 8 Unicore duo
[0044] 9 Stacked core
[0045] 10 Evans core
[0046] 11 Outer wound core
[0047] 12 Inner wound core
[0048] 13 Transformer winding
