EP0077487B1 - Iron core for transformers - Google Patents

Abstract

1. An iron core for transformers consisting of very thin sheets of an amorphous material and having very low hysteresis losses, in which the core limb (3) and yokes (2) respectively consist of a plurality of juxtaposed sheet stacks (1) and the sheet stacks (1) interlock in the manner of brick-work at the junctions between the core flanks (3) and the yokes (2), characterised in that a plurality of sheets are securely joined to form column-shaped self-supporting sheet stacks (1) of constant shape ; that the sheets are stuck to one another within a sheet stack (1) ; that all the sheet stacks (1) have the same rectangular cross-section and only represent different parallelepipeds in respect of their length, so that all butt joints (4) at the junctions between the sheet stacks (1) are either at right angles or parallel to the axes of the core limbs.

Description

The invention relates to iron cores for transformers made of very thin sheet metal lamellae made of amorphous material, with very low magnetic loss losses, core legs and yokes each being composed of a plurality of sheet metal packs lying one against the other and the sheet metal packs interlocking at the nodes between the core legs and the yokes in the manner of a brick masonry.

The iron cores for transformers are usually constructed from cold-rolled, grain-oriented core sheets. As stated in the book «Küchler's Transformers in the 2nd edition on pages 13 and 14, the core plates are mortised so that the joints are offset in layers. The magnetic directional sensitivity of the cold-rolled core sheets necessitates careful individual sheet nesting in order to keep the magnetic losses, especially at the core corners and nodes, small. In order to facilitate the shift work, the sheets are often also stacked on top of one another in pairs, with a relatively small increase in the magnetic reversal losses. Depending on the size of the permissible magnetic reversal losses, the stress points are designed with 90 ° spigot or with 45 ° spigot.

For a long time, such cores made from mortised laminated single sheets have been preferred, which are superior to the butt-jointed core both because of their better magnetic closure and in terms of the omission of special tensioning structures.

When mortising, the individual core sheets are stacked on top of one another, as explained above, in such a way that the joints are offset from one another in layers. The sheets are often placed in pairs to facilitate shift work. (FR-A-514079 and US-A-1 365 569).

From DE-A-2151960 it is also known to connect all of the individual sheets of a transformer core with one another to reduce noise by means of an elastic adhesive. In such an arrangement, the transformer core forms a single indivisible component and, for manufacturing reasons, can therefore only be used for smaller transformers.

From DE-A-2914123, on the other hand, it is known to build iron cores for transformers made of amorphous metal alloys with very low magnetic loss losses. Core sheets made of these amorphous metal alloys are, however, even thinner than the previously customary transformer sheet and are therefore difficult to handle in the case of layers of cores and also increase the effort required for layering cores due to the greater number of individual sheets required as a result of their lower thickness.

The invention has for its object to provide a core structure for the use of core sheets with very low sheet thickness and with extremely low magnetic reversal losses, which allows technically satisfactory and economical production even very large transformer cores.

According to the invention, this object is achieved by

that a large number of sheet metal lamellas are firmly joined to form columnar, self-supporting, dimensionally stable sheet metal packages,

that the sheet metal fins are glued together within a sheet stack,

that all laminated cores have the same rectangular cross-section and only represent different cuboids with regard to their length, so that all butt joints between the laminated cores at the nodes are either perpendicular or parallel to the core leg axes.

According to a development of the invention, it is provided that the laminated cores, each forming a core leg, stacked in the correct position serve as a winding core for an associated winding, and that this winding holds the laminated cores together as a bandage. The laminated cores of the two yokes are only inserted into the corresponding cutouts in the cored limbs after all the windings have been applied to the cores, and the laminated cores are held together in the nodes by gluing or other mechanical devices.

The core structure according to the invention from column-shaped laminated cores allows, in a very advantageous manner, prefabrication of these very robust and relatively insensitive assemblies also from very thin sheet metal, which is relatively sensitive in itself, so that large transformer cores, for example from amorphous metal sheets developed recently, can be economically constructed Material with very low magnetic loss is made possible.

• Figur 1 zeigt die Verzapfung eines Joches mit einem Endschenkel und
• Figur 2 die Verzapfung eines Mittelschenkels mit Jochen.

An embodiment of the invention is explained in more detail with reference to a drawing.

• Figure 1 shows the tapping of a yoke with an end leg and
• Figure 2 shows the mortise of a middle leg with yokes.

Sheet packs 1 are assembled in a manner not shown from a plurality of very thin sheet metal lamellae of the same size and have the shape of cuboids. The laminations are made of amorphous, ferromagnetic material and are considerably thinner than laminations made of grain-oriented transformer sheet.

All laminated core 1 of core legs 3 and Yokes 2 of the same iron core preferably have the same cross section, in the illustrated embodiment an elongated rectangle. The core legs 3 and the yokes 2 are composed of laminated cores 1 of different lengths and / or offset in the longitudinal direction. Accordingly, a laminated core 1 alternately forms a pin at the nodes of the iron core and the next laminated core 1 with its end face forms the base of a groove. By appropriate layering of the laminated cores 1, the core legs 3 are mortised at the junctions with the yokes 2, all butt joints between adjacent laminated cores 1 being either parallel or at right angles to the core leg axes. To compensate for manufacturing tolerances, a small air gap is provided between the end faces of a sheet metal compact 1, each of which represents the base of a groove, and the peg engaging in this groove.

The laminations in the individual laminated cores 1 are glued to one another or are held together by bolts made of preferably non-magnetic material and thereby form building blocks for the iron cores of transformers which can be produced efficiently in a prefabrication. The mechanical cohesion of the laminated cores 1 in the core legs 3 and the yokes 2 takes place in a conventional manner in a press frame, inter alia with the aid of press iron and bandages.

The pressing force for holding the laminated cores 1 together in the individual core legs 3 can advantageously be taken over by transformer windings applied directly to the core legs. In the latter embodiment, both the laminated cores 1 of the lower and of the upper yoke are then mortised with the ends of the core legs 3 after the windings have been applied.

Claims (4)

1. An iron core for transformers consisting of very thin sheets of an amorphous material and having very low hysteresis losses, in which the core limb (3) and yokes (2) respectively consist of a plurality of juxtaposed sheet stacks (1) and the sheet stacks (1) interlock in the manner of brickwork at the junctions between the core flanks (3) and the yokes (2), characterised in

that a plurality of sheets are securely joined to form column-shaped self-supporting sheet stacks (1) of constant shape ;

that the sheets are stuck to one another within a sheet stack (1) ;

that all the sheet stacks (1) have the same rectangular cross-section and only represent different parallelepipeds in respect of their length, so that all butt joints (4) at the junctions between the sheet stacks (1) are either at right angles or parallel to the axes of the core limbs.

2. An iron core as claimed in Claim 1, characterised in that the sheet stacks (1) which in each case form a core limb (3) serve as a winding core for an associated winding when placed upon one another so as to be correctly positioned ; and that the winding acts as a bandage to hold the sheet stacks (1) together.

3. An iron core as claimed in Claim 1 and Claim 2, characterised in that the sheet stacks (1) of both yokes (2) are only inserted into the corresponding recesses of the core limbs (3) after all the windings have been applied to the core limbs.

4. An iron core as claimed in Claim 1, characterised in that the sheet stacks (1) are connected to one another at the junctions by adhesion.

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