DRY-TYPE TRANSFORMER CORE

Abstract

A dry-type transformer core has an iron core with a number of limbs designed to be wrapped with a winding and interconnected by a number of magnetic yokes. The object is to produce a transformer of this type in a simple manner, which is especially well protected against corrosion. For that purpose, the dry-type transformer core includes a casing that is formed onto the iron core. The casing surrounds the iron core in a substantially flush manner.

Claims

1-15. (canceled)

16. A dry-type transformer core, comprising: an iron core having a plurality of limbs that are configured to be provided with a winding and a plurality of yokes connecting said limbs to one another; a housing integrally formed on said iron core and surrounding said iron core in a substantially flush manner.

17. The dry-type transformer core according to claim 16, wherein said housing is non-magnetic.

18. The dry-type transformer core according to claim 16, wherein said housing has a mean relative permeability between −1.01 and 1.01.

19. The dry-type transformer core according to claim 18, wherein said housing has a mean relative permeability between −1.001 and 1.001.

20. The dry-type transformer core according to claim 16, wherein said housing has a wall with a wall thickness of less than 1 cm.

21. The dry-type transformer core according to claim 16, wherein said housing is predominantly made of a plastic material.

22. The dry-type transformer core according to claim 16, wherein said housing is predominantly made of steel.

23. The dry-type transformer core according to claim 16, wherein said housing is grounded.

24. The dry-type transformer core according to claim 16, wherein said housing is constructed from a plurality of parts, and wherein one of said parts substantially surrounds one of said yokes.

25. The dry-type transformer core according to claim 16, wherein said housing has a number of fastening devices on an outside thereof.

26. The dry-type transformer core according to claim 16, wherein said iron core consists of amorphous foils.

27. The dry-type transformer core according to claim 16, wherein said iron core and said housing are disposed to have a clearance therebetween and said clearance between said iron core and said housing is filled.

28. The dry-type transformer core according to claim 16, wherein said housing comprises an insulating part that is configured not to enable a closed conductor loop to be formed around said iron core.

29. A dry-type transformer, comprising: a dry-type transformer core according to claim 16; and a plurality of coils wound around said limbs and surrounded by said housing.

30. The dry-type transformer according to claim 29, configured for a nominal voltage of greater than 1 kV.

31. The dry-type transformer according to claim 29, configured for a nominal power of greater than 50 kVA.

32. The dry-type transformer according to claim 29, configured for a nominal voltage of greater than 1 kV and a nominal power of greater than 50 kVA.

33. The dry-type transformer according to claim 29, being a cast resin transformer.

Description

[0024] Exemplary embodiments of the invention are explained in more detail with reference to a drawing, which shows:

[0025] FIG. 1 a dry-type transformer core having a rounded housing which surrounds the iron core;

[0026] FIG. 2 a dry-type transformer core having a rounded housing which surrounds the iron core and which has a plurality of fastening devices; and

[0027] FIG. 3 a dry-type transformer core having a housing which is rectangular in terms of the limb cross-section, and which surrounds the iron core and which has a plurality of fastening devices.

[0028] The same parts are provided with the same reference numerals in all of the figures.

[0029] All of the figures described below show dry-type transformer cores 1 which are configured for cast resin transformers having a nominal voltage of greater than 1 kV and/or a nominal power of greater than 50 kVA and therefore have a corresponding size. They are particularly suitable as power transformers in electrical energy grids. The common features of the three figures are firstly described below.

[0030] The dry-type transformer cores 1 shown have an iron core 2 comprising electric sheets in laminated form. In other exemplary embodiments, the core is composed of amorphous films. It is illustrated by dashed lines in all of the figures since it is located inside the housing 4. The dimensions of the electric sheets diminish in height and width with respect to the edge of the iron core 2 so that, when the electric sheets are stacked above one another, steps 6 are produced as a result of the diminishing dimensions in each lamination. A somewhat rounded shape of the iron core 2 is achieved in this way. In other embodiments (not shown), it can also be economical to have a rectangular core cross-section without the edges being rounded, e.g. in the case of amorphous sheets.

[0031] Transformers are essentially differentiated by the terms “shell type” and “core type”. In both types, the windings encompass a common iron core 2. If the winding and the iron core 2 are surrounded by outer iron paths, or the majority of the conductive windings, which can consist for example of copper or aluminum, are surrounded by iron, this refers to shell transformers. However, the dry-type transformer cores 1 shown in the figures are configured for core transformers.

[0032] The limbs 8 (also main limbs) to be provided with windings are connected to one another here at their ends by yokes 10. The type of transformer core is indicated in a code consisting of two numbers. The first number describes the number of limbs 8 provided with windings, the second describes the number of return limbs (this refers to outer limbs in the case of a shell transformer which are not provided with windings).

[0033] All of the figures each show a 3/0 dry-type transformer core 1, i.e. a three-limb dry-type transformer core 1 without a return limb, the three limbs 8 of which are to be provided with a winding. However, the exemplary embodiments are only referred to by way of example; the housing illustrated here with all the properties described may also be manufactured for any other configurations.

[0034] The housing 4 is made of a non-magnetic material in all of the figures, i.e. a material having a relative permeability in the range between −1.01 and 1.01. A plastic material can be used for this in some exemplary embodiments, or chrome-nickel steel can also be used for this in other exemplary embodiments.

[0035] In the figures, the housing 4 is integrally formed on the iron core 2 in a flush manner in each case, i.e. it is designed so that it holds the iron sheets of the iron core 2 together with form fit. It surrounds the iron core 2 completely, i.e. it encapsulates it. The housing 4 here has a wall thickness in each case of less than 1 cm, i.e. a few mm. An empty space remaining between the iron core 2 and the housing 4 is filled with a suitable material. The housing 4 is constructed from a plurality of parts in each case: firstly a first part 12 is provided, which surrounds the upper yoke 10, and a second part 14 is provided which surrounds the limbs 8 and the lower yoke 10.

[0036] Both parts 12, 14 are in turn composed in two parts as half shells so that, in the manufacturing process, the iron core 2 can be inserted into the first half shell and the second half shell can then be connected to the first half shell for stabilization purposes.

[0037] The differences between the exemplary embodiments in the different figures are explained in more detail below.

[0038] FIG. 1 shows a dry-type transformer core 1 having a housing 4 with a circular cross-section over the yokes 10 and limbs 8. It follows the outer contour of the iron core 2.

[0039] FIG. 2 shows a dry-type transformer core 1 having a housing 4 with a likewise circular cross-section over the yokes 10 and limbs 8, which is shaped like the housing in FIG. 4. However, it additionally has fastening devices 16, 18 in the manner of eyes fastened externally to the housing 4. Fastening devices 16 are provided for fixing the dry-type transformer core 1 in position during the installation of the transformer, e.g. on brackets 20. Further fastening devices 18 serve to fix the windings (not illustrated) in position.

[0040] In contrast to FIG. 1 and FIG. 3, the housing 4 in FIG. 2 is made of an electrically conductive material, e.g. the chrome-nickel steel mentioned above. The housing 4 is firstly grounded here. It furthermore comprises two insulating parts 22 (illustrated in FIG. 2), which are designed so that no closed conductor loops can occur around the iron core 2. In the exemplary embodiment of FIG. 2, the sides of the insulating parts 22 each form a rectangle, whereof the sides extend parallel to the axis of the respective limb 8 or yoke 10 on the inside, i.e. the face of the wall 4 which faces the adjacent limb 8 or yoke 10, and form a closed line here. The insulating parts 22 interrupt the otherwise conductive body of the housing 4 here. A flow of current in the wall 4 around the limbs 10 and yoke 8 is prevented here by the sides of the insulating parts 22.

[0041] FIG. 3 shows a dry-type transformer core 1, whereof the housing 4 has the same fastening devices 16, 18 as those in FIG. 2. However, the cross-section of the housing 4 over the yokes 10 and limbs 8 is rectangular.