TRANSFORMER

Description

[0001] The present disclosure relates to atransformer, in particular to a transformer for application in power grid systems, for example it relates to high voltage transformers.

[0002] Transformers are used in power systems for voltage level control. In particular, a transformer is used to step up and step down voltage in electric power systems in order to transmit and utilize electrical power.

[0003] US 10 658 106 B2 relates to a safe stationary induction electrical apparatus that prevents a fragment coming off a magnetic shield, wound around an iron core leg portion of the stationary induction electrical apparatus, due to vibrations from being released in a tank accommodating the stationary induction electrical apparatus and thus prevents a trouble such as dielectric breakdown.

[0004] US 2018 / 358160 A1 relates to a stationary induction apparatus that includes: an iron core; a winding wound outside of the iron core; a plurality of iron core clamps that sandwich the winding from a longitudinal direction of the iron core; a magnetic material ring configured with a silicon steel plate wound outside of the iron core; a laminated magnetic material composite ring that includes an insulator provided on an outer circumference of the magnetic material ring that includes an electrical conductor provided on an outer circumference of the insulator, and that is disposed between the winding and each of the iron core clamps; and a holding- and-cooling structure disposed between the winding and the laminated magnetic material composite ring.

[0005] US 2011 / 316662 A1 relates to winding arrangement for a transformer or for a reactor. The winding arrangement includes an annular winding cover part disposed on the front face of a winding, wherein a side surface of the winding cover part overlaps a front surface of the winding, wherein the annular winding cover part is designed to be magnetically conductive at least in a partial area and comprises a convex side surface facing away from the winding.

[0006] WO 2017 / 134040 A1 relates to a shielding ring used for windings of transformers for reducing the electrical load at the edges of the conductors. Such a shielding ring comprises an electrically conductive layer. According to the invention, a combination of a polymer matrix and fillers as the electrically conductive layer are proposed, by means of which combination the resistance of the electrically conductive layer of a shielding ring can be set exactly as needed and thus the correct resistance of the electrically conductive layer can be realized according to the application.

[0007] It is desirable to provide a transformer that can be operated reliably.

[0008] Embodiments of the disclosure relate to a transformer. The transformer comprises a core. The transformer comprises a winding. The winding is wound around a winding axis extending along the core. The transformer comprises an eddy losses reducer. The eddy losses reducer is arranged at an axial end of the winding. The eddy losses reducer, in the following also called "reducer", comprises a non-ferromagnetic main body. The reducer comprises a ferro-magnetic layer surrounding the main body.

[0009] During operation, radial flux generate axial forces. For example, these forces cause vibration and resulting noises. In addition, radial flux leads to losses and hotspots. The eddy losses reducer is arranged to reduce losses, hotspots and thus also forces. Due to the eddy losses reducer, the magnetic flux generated by the winding generates less eddy losses in conductors of the winding and thus less axial forces as well. The eddy losses reducer is arranged at the axial end, where radial flux is higher and tends to go out from the winding and reach the core or the tank. This is reduced by the eddy losses reducer. Thus, losses and hotspots generated by the radial flux at the end of the winding are reduced.

[0010] The eddy losses reducer, which can also be called "magnetic flux collector", is used to reduce the eddy radial losses in the winding and / or the exposed area of the core. In particular, the eddy losses reducer can an integral part of an equipotential ring which is arranged at the axial end of the winding. The equipotential ring is extended by an eddy losses reducing functionality. Therefore, the ferromagnetic layer is provided which surrounds the non-ferromagnetic main body. For example, the ferromagnetic layer comprises iron or another ferromagnetic metal or material.

[0011] The eddy losses reducer comprises a ring segment shape. The eddy losses reducer comprises an opening where two ends of the eddy losses reducer are arranged opposite each other and are arranged at a distance from each other. The eddy losses reducer is interrupted at the opening. For example, ring flows along the eddy losses reducer are avoided. The ring segment shape may be circular or elliptic.

[0012] According to embodiments, the ferromagnetic layer comprises a thickness between 50 µm and 9 cm. Other thicknesses are possible, in particular between 25 µm and a few centimeters. The thickness, for example, is measured along the winding axis or transverse to it.

[0013] According to embodiments, the ferromagnetic layer comprises a metal strip. For example, the metal strip is rolled around the main body. For example, the metal strip comprises one iron sheet or more iron sheets. For example, the metal strip consists of an iron sheet or a plurality of iron sheets. For example, the iron sheets are rolled around the non-ferromagnetic main body. For example, the metal strip comprises a thickness between 50 µm and 9 cm in a vertical direction of the metal strip, whereby the vertical direction is thinner than the two transverse directions, which are aligned perpendicular to the vertical direction. For example, the iron sheet is made of ferromagnetic material. For example, the iron sheet compriese electrical steel like the one used to produce transformer cores and including amorphous ones.

[0014] According to embodiments, the transformer can comprise an adhesive connection to fix the metal strip. For example, the adhesive connection fixes the metal strip to the main body. The adhesive connection can be useful to restrict themovement of the metal strip during operation. The adhesive connection is configured to reduce vibrations of the metal strip, if needed. The metal strip, which is rolled around the main body, is glued to reduce vibrations.

[0015] According to embodiments, the main body comprises an electrically insulating material. The main body is, for example, made of a non-ferromagnetic electrically insulating material to not, or only insignificantly, influence the magnetic field generated by the winding. For example, the main body comprises at least one of wood and plastic. For example, the main body consists of at least one of wood and plastic. For example, the main body is made of laminated wood or transformer board.

[0016] According to embodiments, the eddy losses reducer comprises a covering layer. The covering layer surrounds the ferromagnetic layer. For example, the ferromagnetic layer is arranged between the covering layer and the main body. The covering layer protects the ferromagnetic layer and / or forms an electrical insulation. Alternatively or in addition, the covering layer is used to smooth the surface.

[0017] For example, the covering layer comprises at least one of paper, textile, and plastic. For example, the covering layer comprises crepe paper.

[0018] According to embodiments, the covering layer comprises a carbon layer and / or a further metallic layer. For example, the carbon layer and / or the further metallic layer is formed as a coating of the covering layer. The carbon layer and / or further metallic layer faces the ferromagnetic layer. For example, the covering layer comprises several layers. For example, the covering layer comprises a paper layer, a carbon and / or metallic layer, and a further paper layer. For example, the carbon layer and / or the further metallic layer is used to keep the voltage of the eddy losses reducer at a defined voltage during operation.

[0019] According to embodiments, the winding is arranged directly adjacent to and at a distance to the core. Thus, the eddy losses reducer is arranged at the winding which is arranged nearest to the core. For example, the eddy losses reducer is arranged at the winding with the smallest diameter.

[0020] According to embodiments, the transformer comprises a further eddy losses reducer. The further eddy losses reducer is designed correspondingly to the eddy losses reducer, for example. The further eddy losses reducer is arranged at a further axial end of the winding. The further axial end is arranged axially opposite the axial end. At both axial ends of the winding, a respective eddy losses reducer is arranged to reduce eddy losses and / or collect the magnetic flux at both axial ends.

[0021] According to an embodiment, the transformer comprises a plurality of windings around the core. For example, respective eddy losses reducers are arranged on each of the windings. According to a further embodiment, respective eddy losses reducers are arranged only on a part of the windings. In particular, the respective eddy losses reducer is arranged on the windings, which are arranged facing the core. For example, windings that are arranged facing away from the core do not have an eddy losses reducer. For example, the eddy losses reducers are arranged on the windings with the smallest radii and not on windings with a larger radius which are arranged further away from the core.

[0022] According to an embodiment, the eddy losses reducers are arranged coaxially to the core. For example, the eddy losses reducers of the plurality of eddy losses reducers comprises a common center in a ready-to-operate condition. For example, the center corresponds to the winding axis.

[0023] According to an embodiment, the transformer comprises a second core. The transformer comprises a second winding wound around a second winding axis extending along the second core. The transformer comprises a second eddy losses reducer. The second eddy losses reducer, for example, is designed correspondingly to the first eddy losses reducer. The second eddy losses reducer is arranged at an axial end of the second winding. It is possible that one eddy losses reducer surrounds the first core and a second eddy losses reducer surrounds the second core. It is possible that a plurality of eddy losses reducers surrounds the first core and a further plurality of eddy losses reducers surrounds the second core.

[0024] It is possible that respective eddy losses reducers are arranged on both axial ends of the windings around the first core, or at just one single axial end. Alternatively or in addition, it is possible that respective second eddy losses reducers are arranged at both axial ends of the second windings around the second core, or at just one single axial end of the second windings.

[0025] All of the features and advantages as described herein relating to the eddy losses reducer are applicable to further eddy losses reducers. For example, the winding is a primary winding or a secondary winding. For example, the transformer comprises a tertial winding, which is arranged without an eddy losses reducer.

[0026] For example, the voltage ratings of one or more of the windings of the transformer are above 1 kV such that the voltage ratings of all of the windings of the transformer are above 1 kV.

[0027] Hereinafter, the transformer will be explained in more detail with reference to the drawings on the basis of exemplary embodiments. The accompanying figures are included to provide a further understanding. In the figures, elements of the same structure and / or functionality may be referred by the same reference signs. It is to be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. Insofar as elements or components correspond to one another in terms of their function in different figures, the description thereof is not necessarily repeated for each of the following figures.

[0028] Figure 1 shows a schematic cross-section of a transformer according to an embodiment.

[0029] Figures 2 to 4 show different views of an eddy losses reducer according to an embodiment.

[0030] Figure 1 schematically shows parts of a transformer 100. The transformer 100 is enclosed in a tank (not explicitly shown) which, for example, is filled with a dielectric fluid. The transformer 100 comprises a first core 101 and a second core 121. Windings 102, 103, 104 are arranged around the first core 101. Further windings 122, 123, 124 are arranged around the second core 121. In particular, the first core 101 and the windings 102, 103, 104 are symmetric around a winding axis 105. Correspondingly, the second core 121 and the windings 122, 123, 124 are symmetric around a second winding axis 125.

[0031] The winding 102 extends along the winding axis 105 and terminates in an axial end 106 and an opposite axial end 107. The winding 103 ends in an axial end 108 and an opposite axial end 109. The windings 122 and 123 correspondingly terminate in respective axial ends 126, 127, 128, 129.

[0032] The winding 102 has a smaller diameter than the remaining windings 103, 104, which are arranged around the first core 101. The coil 102 is located closest to the first core 101. The winding 102 is arranged at a distance 150 from the first core 101.

[0033] The windings 122 has a smaller diameter than the remaining windings 123, 124, which are arranged around the second core 121. The coil 122 is located closest to the second core 121.

[0034] The transformer 100 comprises an eddy losses reducer 200 which is arranged at the axial end 106 of the winding 102. Further eddy losses reducers 200 are arranged at the axial ends 107, 108, 109 around the first core 101. Around the second core 121 eddy losses reducers 200 are arranged at the axial ends 126, 127, 128 and 129.

[0035] For example, no eddy losses reducers 200 are arranged at the winding 104 and the winding 124. Thus, the winding 104 around the first core 101 has no associated eddy losses reducer 200. Thus, the winding 124 around the second core 121 has no associated eddy losses reducer 200.

[0036] Eddy losses reducers 200 are arranged at the windings 102, 103 that are arranged radially between the first core 101 and the winding 104.

[0037] Eddy losses reducers 200 are arranged at the windings 122, 123 that are arranged radially between the second core 121 and the winding 124.

[0038] The number of eddy losses reducers 200 is purely exemplary and may deviate from the number shown in Figure 1. For example, less than the shown eddy losses reducers 200 may be provided or more. For example, just one single eddy losses reducer 200 is provided around each core 101, 121.

[0039] Respective eddy losses reducers 200 can be arranged at each opposite end or only at one end and the other end is free of an eddy losses reducer. The number of eddy losses reducers 200 around core 101 can be different from the number of eddy losses reducers 200 around the second core 121. It is possible that the transformer 100 comprises more than two cores 101, 121, for example three cores with respective windings or more. For example, the transformer 100 comprises three cores with respective windings and 12 eddy losses reducers 200, four eddy losses reducers 200 per core, two windings with two eddy losses reducers 200 each per core.

[0040] As shown in Figure 2, the eddy losses reducer 200 comprises a ring-like shape 203. The eddy losses reducer 200 comprises a center 213. For example, the center 213 of the shape 203 of the eddy losses reducer 200 lies on the winding axis 105 or the winding axis 125 respectively. The eddy losses reducer 200 extends in the ring-like shape or ring segment shape 203 around the respective core 101, 121. For example, the eddy losses reducer comprises a radius around the center 213 with a value between 30 cm and 3 meters, depending on the transformer type of the transformer 100.

[0041] The eddy losses reducer 200 for example is not formed as a closed ring but with the ring segment shape 203. The eddy losses reducer 200 comprises an opening 204. At the opening 204 two ends 205, 206 of the eddy losses reducer 200 are arranged facing each other and opposite each other. the two ends 205, 206 are arranged at a distance 207. For example, the distance 207 comprises values from 0.5 mm to 25 cm. Other ranges and values for the distance 207 are possible.

[0042] Figure 3 shows a cross-section of the eddy losses reducer 200 along the line A of Figure 2. The eddy losses reducer 200 comprises a main body 201. The main body 201 comprises the ring segment shape 203. The main body 201 comprises or consists of a non-ferromagnetic material. For example, the main body is made out of wood and / or plastic. In particular, the main body 201 is made out of laminated wood and / or transformer board. The main body 201 is configured as a stable body which supports the eddy losses reducer 200.

[0043] A first layer 202 surrounds the main body 201. The first layer 202 comprises or consists of a ferromagnetic material. In particular, the first layer 202 comprises or consists of a metal, for example a metal strip 209 (Figure 4). For example, the first layer 202 comprises iron or consists of iron. For example, the first layer 202 is an iron sheet and can just be made of ferromagnetic material. For example, the first layer 202 comprises electrical steel like the one used to produce transformer cores and including amorphous ones.

[0044] An optional further layer 212 surrounds the first layer 202. The further layer 212 comprises or consists of a carbon layer and / or a further metallic layer. In particular, the further layer 212 comprises an electrically conductive material.

[0045] A covering layer 211 surrounds the further layer 212 and the first layer 202. For example, the covering layer comprises or consists of paper, textile or plastic. For example, the further layer 212 covers the covering layer 211 at a surface which faces the first layer 202. For example, the covering layer 211 comprises carbonized paper such that the further layer 212 is a carbon layer on the paper.

[0046] Figure 4 shows an example of the eddy losses reducer 200 in which the ferromagnetic layer 202 is made out of the metal strip 209. The metal strip 209 is wound around the main body 201, such that the metal strip 209 covers the main body 201. For example, a plurality of metal strips 209 is wound around the main body 201 to achieve a desired thickness 208 (Figure 3) of the ferromagnetic layer 202. Alternatively or in addition, the metal strip 209 is wound around the main body 201 several times to achieve the desired thickness 208. For example, the thickness 208 comprises a value between 50 µm and 9 cm, for example between 1 mm and 10 mm.

[0047] For example, the metal strip 209 comprises a thickness between 0.01 mm and 0.6 mm . In particular, if the metal strip 209 comprises amorphous materials, the thickness of the metal strip comprises a value between 10 and 15 µm. For example, the metal strip 209 is a rolled iron sheet.

[0048] According to an example, the metal strip 209 is fixed by an adhesive connection 210.

[0049] According to another example, the adhesive connection 210 is omitted.

[0050] The adhesive connection 210 can glue the metal strip layer 209 to itself and / or to the main body 201. An adhesive fixes the metal strip layer 209. Thus, a vibration of the metal strip 209 can be reduced, if needed depending on the design. This reduces noise emissions.

[0051] According to an embodiment, the eddy losses reducer 200 also serves as an equipotential ring to reduce electrical stress at the axial ends 106 to 109, 126 to 129 of the respective windings 102, 103, 104, 122, 123, 124. Thus, no additional element in addition to an equipotential ring is necessary to achieve the reduction of the eddy radial losses with the eddy losses reducer 200. The eddy losses reducer 200 acts as the equipotential ring and as a magnetic shunt. Transformer eddy losses can be easily reduced. By reducing the eddy losses, the efficiency of the transformer 100 is improved. Due to the reduced eddy losses, material savings can be achieved.

[0052] The iron used for the metal strip 209 for example comprises an amorphous iron. For example, the iron used for the metal strip 209 is of the same type of iron as used for the core 101, 102.

[0053] The eddy losses reducer 200 is simple to implement and achieves lower losses and / or lower forces in the transformer. The material requirements for the eddy losses reducer 200 are reduced compared to other solutions. Efficiency and reliability of the transformer 100 can be increased without any need for a substantive design change of the transformer 100.Reference Signs

[0054] 100 transformer 101 core 102, 103, 104 winding 105 winding axis 106, 107, 108, 109 axial end 121 core 122, 123, 124 winding 125 winding axis 126, 127, 128, 129 axial end 150 distance 200 eddy losses reducer 201 main body 202 ferro-magnetic layer 203 ring segment shape 204 opening 205, 206 end 207 distance 208 thickness 209 metal strip 210 adhesive connection 211 covering layer 212 carbon layer and / or further metallic layer 213 center

Claims

1. A transformer, comprising: - a core (101), - a winding (102, 103) wound around a winding axis (105) extending along the core (101), - an eddy losses reducer (200), wherein the eddy losses reducer (100) is arranged at an axial end (106) of the winding (102, 103) and comprises a ring segment shape (203) and an opening (204) where two ends (205, 206) of the eddy losses reducer (200) are arranged opposite each other and are arranged at a distance (207) from each other, characterized in that the eddy losses reducer (100) comprises a non-ferromagnetic main body (201) and a ferro-magnetic layer (202) surrounding the main body (201).

2. Transformer according to any one of the preceding claims, wherein the ferro-magnetic layer (202) comprises a thickness (208) between 50 µm and 9 cm.

3. Transformer according to any one of the preceding claims, wherein the ferro-magnetic layer (202) comprises a metal strip (209) which is rolled around the main body (201).

4. Transformer according to claim 3, wherein eddy losses reducer (200) comprises an adhesive connection (210) to fix the metal strip (210).

5. Transformer according to any one of the preceding claims, wherein the main body (201) comprises an electrically insulating material.

6. Transformer according to any one of the preceding claims, wherein the main body (201) comprises at least one of wood, and plastic.

7. Transformer according to any one of the preceding claims, eddy losses reducer (200) comprises a covering layer (211) which surrounds the ferro-magnetic layer (202).

8. Transformer according to claim 7, wherein the covering layer (211) comprises at least one of paper, textile, and plastic.

9. Transformer according to claim 7 or 8, wherein the covering layer (211) comprises a carbon layer (212) and / or a further metallic layer (212).

10. Transformer according to any one of the preceding claims, wherein the winding (102) is arranged directly adjacent to and at a distance (150) to the core.

11. Transformer according to any one of the preceding claims, comprising a further eddy losses reducer (200), wherein the further eddy losses (200) reducer is arranged at a further axial end (107) of the winding (102), wherein the further axial end (107) is arranged axially opposite the axial end (106).

12. Transformer according to any one of the preceding claims, comprising a plurality of windings (102, 103, 104) around the core (101), wherein a respective eddy losses reducer (200) is arranged on each of at least the windings (102, 103) of a part of the windings (102, 103, 104) which is arranged facing the core (101).

13. Transformer according to claim 12, wherein the eddy losses reducers (200) are arranged coaxially to the core.

14. Transformer according to any one of the preceding claims, comprising a second core (121), a second winding (122) wound around a second winding axis (125) extending along the second core (121), and a second eddy losses reducer (200), the second eddy losses reducer (200) being arranged at an axial end (126) of the second winding (122).