EP2239745B1 - Voltage transformer with amorphous coil - Google Patents

Description

The invention relates to a power transformer in dry construction and a method for producing a transformer in dry construction.

Transformers are used for power transmission in power supply by voltage adjustment from a first voltage level to a second one. Instead of previously widely used power transformers with oil filling, power transformers in dry construction, so-called dry-type transformers, are increasingly being used.

The structure of a power transformer in dry construction is very similar to that of the power transformer with oil filling, as well as power transformer in dry construction, the respective winding body are applied to cores made of ferromagnetic material, which are connected at both ends with yokes and form a magnetic circuit.

However, in the case of the dry-type transformers, the heat loss, which was absorbed by the oil in the case of power transformers filled with oil and discharged via suitable cooling surfaces or separate coolers, is removed by air convection. The lower specific heat capacity of the air compared to oil means a performance limitation for dry-type transformers.

Ohmic losses occur in the windings of a loaded transformer due to the winding currents and eddy currents in the conductor material. These ohmic losses are superimposed by no-load losses and possibly short-circuit losses and hysteresis losses.

The no-load losses are mainly determined by the induction and nature of the core and are approximately independent of the operating temperature of the transformer. The short-circuit losses are temperature-dependent and increase at constant load with the temperature or the resistivity of the conductor material. In order to keep the hysteresis losses as small as possible, preferably core materials with a very narrow hysteresis loop are used.

In order to reduce the resulting heat losses of a dry-type transformer and thus to improve its load capacity, amorphous core material is used in place of grain-oriented core material in recent times.

However, the use of amorphous materials requires new constructions and processing because the amorphous material is largely pressure-sensitive so that core losses can be enhanced.

Based on this prior art, it is an object of the invention to provide a power transformer of the type mentioned, the structural design is chosen so that the benefits of the amorphous core material fully come into play without the core losses are increased due to pressure load.

This object is achieved by the characterizing features of claim 1.

Accordingly, the invention provides that the core is kept suspended from amorphous material of the holding device, wherein the holding device for fixing the at least one primary winding and secondary winding is used and for this purpose acts on the at least one winding body respectively at its end faces.

It is envisaged that the amorphous core is made in each case as a winding tape core of strip material made of amorphous material.

Preferably, in this case, the metal coils prepared for use as cores are held in shape by means of tear-resistant tape, in that the tear-resistant tape is repeatedly looped around the sheet stack at a distance from one another so that the sheet metal coils are held together. The winding cores thus formed preferably have a rectangular plan, that is, they each occupy a rectangular area. However, embodiments with an oval or circular floor plan are also within the scope of the invention.

According to a preferred embodiment of the invention, the transformer according to the invention is designed as a three-phase transformer and has three juxtaposed cores, each of which is comprised of a winding or bobbin.

For this purpose, at least two winding cores are arranged side by side with their longitudinal legs and their mechanical connection by means of band material made of amorphous material in the winding plane are wrapped, all legs have the same winding cross-section, that is, the same thickness and width.

In other words, in an advantageous development, at least two, but preferably four, of the previously described winding cores are placed with their longitudinal limbs against one another. This arrangement thus formed is then wrapped by means of band material of amorphous material, so that result as a result of this wrapping a total of five legs with the same winding cross-section.

According to the present invention, the holding device is formed from at least two clamping elements, which are in operative connection with each other and are arranged on each end face of a winding body. It is provided that the support structure is designed so that mechanical stresses that arise during the fixation of the winding body, are initiated only in the support structure and in the winding body, so that the covered by the winding bodies cores in the support structure, although guided but not braced , so exposed to mechanical stresses are.

According to an alternative embodiment of the invention it can be provided that each core is cylindrical in shape of amorphous material in layer construction with at least two legs and a one-piece molded yoke.

Advantageously, the clamping elements of the support structure may consist of ferromagnetic material and at the same time serve as a yoke.

It proves to be advantageous in this case that each core is magnetically connected to the clamping elements of the holding device. For this purpose, it is provided that each core end is in each case encompassed on two opposite sides of the clamping elements without pressure, wherein to avoid a compressive load of the core due to a clamping of the core and the resulting mechanical stress, the clamping elements by means firmly connected to the clamping elements spacer exactly Distance to the respective core are kept.

The respective core is in this case introduced at the intended location with one end in the space between the clamping elements and held by a likewise firmly connected to the clamping elements support plate, so that, for example, in a three-phase transformer designed as a transformer according to the invention three cores columnar next to each other at the lower yoke serving lower holding device, wherein they optionally engage in the space defined by the two clamping elements gap while avoiding mechanical stresses.

However, according to an embodiment variant of the invention, it is also possible that the retaining construction consists of non-ferromagnetic material, in particular of fiber-reinforced plastics. Although the holding structure is not part of the magnetic field circuit in this case, the entire arrangement has a significantly reduced weight compared to a full-metal design.

According to a further improvement of the transformer according to the invention, each core is provided at its end faces with a pad of insulating material. This edition serves both as electrical insulation and on the other hand as a means of shock absorption for the relevant core. Preferably, this edition of an insulating material, such as plastic, in particular glass fiber reinforced plastic or silicone rubber.

According to a further advantageous embodiment of the transformer according to the invention carriers are provided at the front ends of each yoke, which interconnect the yokes, that is, the lower yoke with the upper yoke. These carriers are preferably guided along the outer longitudinal sides of the core or cores and encompassed by the relevant respective winding body, that is, the carriers are guided in the interior of the winding body parallel to the respective core and connected to the opposite yoke.

In addition, tie rods can be provided which press the yokes formed from the clamping elements against the winding body, wherein the cores are each unimpaired.

In summary, it can be stated that the invention provides, instead of a hitherto conventional core press construction, in which the attachment of the coil or winding body is effected by pressing against the core, to use a coil press construction. Here, the winding body are held by a support structure independent of the core. The core is only placed or suspended on designated plates of the support structure.

In addition to protecting the new design of a so-called hanging core transformer in a coil or winding press design, it is also an object of the present invention to provide a method of manufacturing this novel transformer, namely a transformer having a core composed of layered strips of amorphous material , which is sensitive to mechanical stresses, with at least one surrounding the core, at least one primary winding and a secondary winding formed winding body and specify at least one holding device.

Accordingly, the inventive method for producing such a transformer is defined by the features of claim 10.

Here, the short legs of the winding rings each form the magnetic yokes. Instead of the rectangular shape for the cross section of the individual winding rings and oval or circular cross-sections can be used.

Alternatively it can be provided that the transformer core is formed from a total of four coils with juxtaposed longitudinal limbs, which are mechanically connected to one another, so that in this way a 5-limb core is produced. Again, the mechanical connection, as previously indicated for the dreischkeligen core, preferably effected by the single cores are wrapped in its winding plane with tape material and so the composite of the individual cores is made into a 5-leg core.

According to an advantageous embodiment variant, it is expedient for mats of silicone rubber to be arranged on the end faces of each core for purposes of shock absorption and electrical insulation.

Further advantageous embodiment possibilities can be found in the further dependent claims.

These and other advantageous embodiments and improvements of the invention are the subject of the dependent claims.

Reference to an embodiment of the invention shown in the accompanying drawings, the invention, advantageous embodiments and improvements of the invention and particular advantages of the invention will be explained and described in detail.

Show it:

Fig. 1

a side view of a transformer according to the invention with complete electrical interconnection,

Fig. 2

a sectional view taken along the section line AA in Fig. 1 .

Fig. 3

a side view of a support assembly for fixing a winding body and

Fig. 4

a side view of a core support

In Fig. 1 is a side view of a transformer 10 according to the invention with complete external electrical interconnection shown, which has as a three-phase transformer each core 11 in three winding bodies 12, the upper electrical terminals 14, 16, 18 in the example shown with U, V, W and by means of connecting conductors 20 are conductively connected to each other.

The three winding bodies 12 are arranged in close proximity to each other in line and held between a lower yoke 22 and an upper yoke 24.

Each yoke 22, 24 is composed of two clamping elements 25 each formed as a C-profile, that is, of a web portion 26 with on its longitudinal sides to the same side facing right-angled flanges 28. The clamping elements 24 are arranged parallel to each other, such that the flanges 28 are directed outwards while their flangeless backs face each other.

In the example shown, the flanges have a different width and in such a way that the flanges 28 located on the side of the winding body 12 are narrower than those on the side facing away from the winding bodies 12, which are about twice as wide. In particular, for the clamping elements 25 of the lower yoke 22, this design proves to be advantageous because with the wider flanges 28 a correspondingly larger footprint and thus a higher stability is ensured.

Each of the winding bodies 12 facing flanges 28 of the clamping elements 25 are used to attach the winding body 12 and thus to force during clamping of the yokes 22, 24. In addition, at the lower flange 28 of the lower yoke 20 trusses 30 are attached to the outer ends rollers 32nd are fixed, on which the entire transformer 10 is movable, as well as from the view in Fig. 2 can be seen.

To support the winding body 12 on the lower yoke 20 serve cross member 34, which consist of electrically non-conductive material and preferably as glass fiber reinforced plates 36 and strips 38 are used. These cross members 34 are connected on the one hand with the upper flange 28 of the lower yoke 20 and on the other hand with the respectively set thereon winding bodies 12th

In a similar manner, this fastening manner is repeated at the top of the transformer 10. Again, for the purpose of anchoring the winding body 12 of plates 36 and strips 38, both consisting of electrically non-conductive material, formed cross member 34 is arranged accordingly, which for the rigid connection of the winding body 12 are provided with the lower flange 28 of the upper yoke 22.

In the Fig. 2 which is a cross section through the transformer 10 according to FIG Fig. 1 is reproduced along the section line AA drawn there, the transformer 10 according to the invention is shown with a view of a winding body 12 from the side.

In particular, this view differs from the one in Fig. 1 shown by the view held in the lower yoke 22 and upper yoke or suspended core 11 made of amorphous material.

As already stated elsewhere, in the case of amorphous materials intended for the manufacture of transformer cores, care must be taken to ensure that the core material is not subjected to any mechanical stress, for example by pressure, as this causes an increase in core losses.

For this reason, the lower flanges 28 of the lower yoke 22 forming clamping elements 25 are provided with a support plate 40 on which the respective core 11 rests. In addition, each tie rod 42 are provided, which the clamping elements 25 of the lower yoke 22 and the upper yoke 24 and penetrate the core 11 and so ensure a positive retention of the core 11.

On an upper flange 28 of a clamping element 25, in the example shown the right clamping element 25, the upper yoke 24, an insulator is mounted, which serves to hold the connecting line 20. On the opposite, in the example shown left side of the upper yoke 24 connecting conductors are also shown, which are connected to at least one of the winding body 12.

In Fig. 3 is a side view of a support member formed by a cross member 34 for fixing a winding body 12 is shown, depending on whether it is located outside or inside according to Fig. 1 , narrow as strip 38 or wide as plate 36 is made of glass fiber reinforced plastic.

In the in Fig. 3 the example shown is a cross member 34 which is provided outside to support a winding body 12. Its structure is as follows. At each end of the cross member 34 forming bar 38, a threaded rod 46 is inserted, which passes through the bar 38 and a plate located underneath plate 48 and is anchored in a further perpendicular to the bar 38 arranged bar 54 made of fiberglass reinforced plastic.

Below this, on both sides of the transformer 10 extending strips 38 each have a plate 50 made of silicone, to which a further strip 52 made of glass fiber reinforced plastic connects.

Fig. 4 Finally, a side view of a support for a core 11 of amorphous material. This Auflagerung consists of an upper plate 56 made of silicone, which is supported by the support plate 42 made of glass fiber reinforced plastic. The support plate 42 made of glass fiber reinforced plastic is in turn penetrated by tie rods 42, which cooperate with the clamping elements 25, not shown here, of the upper yoke 22 and are supported thereon.

LIST OF REFERENCE NUMBERS

10

transformer

12

winding body

14

electrical connection U

16

electrical connection V

18

electrical connection W

20

connecting conductors

22

lower yoke

24

upper yoke

25

clamping element

26

web

28

flange

30

traverse

32

role

34

crossbeam

36

Plate made of fiberglass

38

Strip made of fiberglass

40

support plate

42

tie rods

44

insulator

46

threaded rod

48

Plate made of fiberglass

50

Plate made of silicone

52

Plate made of fiberglass

54

Plate made of fiberglass

56

Plate made of silicone

Claims (11)

1. Dry-type transformer (10) with a core in the form of a winding ribbon core composed of amorphous ribbon material, which core is sensitive to mechanical loads, having at least one winding body (12) which surrounds the core and is formed from in each case at least one primary winding and one secondary winding, and having at least one holding apparatus,
   characterized in that
   the holding apparatus is used to fix the in each case at least one primary winding and one secondary winding and is formed from at least two clamping elements (25) which are operatively connected to one another and act on each of the end faces of the at least one winding body, and in that the core composed of amorphous material is held suspended by the holding apparatus, the at least one winding body being held independently of the core.
2. Transformer according to Claim 1, characterized in that the transformer is a polyphase transformer and has three winding bodies with a core.
3. Transformer according to one of the preceding claims, characterized in that the core is in an annular shape with a rectangular, oval or round outline.
4. Transformer according to Claim 3, characterized in that the longitudinal limbs of at least two such winding ribbon cores are arranged alongside one another and have ribbon material composed of amorphous material wound around them on the winding plane for their mechanical connection, with all the limbs having the same winding cross section.
5. Transformer according to one of the preceding claims, characterized in that the clamping elements are composed of ferromagnetic material and are at the same time used as a yoke, with each core being magnetically permeably connected to the clamping elements of the holding apparatus.
6. Transformer according to one of the preceding claims, characterized in that each core is provided with a coating of insulating material on its end faces.
7. Transformer according to one of the preceding claims, characterized in that mounts are provided on the ends of each yoke and connect the yokes to one another.
8. Transformer according to Claim 7, characterized in that the mounts are passed along the core or the cores on the external longitudinal faces, and are surrounded by the relevant winding body.
9. Method for producing a dry-type transformer (10) with a winding ribbon core composed of amorphous material which is sensitive to mechanical loads, having at least one winding body (12) which surrounds the core and is formed from in each case at least one primary winding and one secondary winding, having at least one holding apparatus for fixing the formed winding body, with the holding apparatus being formed from at least two clamping elements (25) which are operatively connected to one another and act on each of the end faces of the at least one winding body, with the core composed of amorphous material being held suspended by the holding apparatus, the at least one winding body being held independently of the core, comprising the following steps:

   a) ribbon material composed of amorphous material is provided;

   b) two annular individual cores each having the same, preferably rectangular, cross section in each case are produced from the amorphous ribbon material by winding;

   c) the two individual cores are placed with their longitudinal limbs against one another and the ribbon material is wound around them on the winding plane of the individual cores, such that the core has three longitudinal limbs with the same cross section;

   d) bracing of the at least one winding body to the holding apparatus;

   e) the outer limbs of the transformer core produced in this way are each provided with the electrical primary winding or the electrical secondary winding;

   f) the electrical windings are then connected.
10. Method according to Claim 9, characterized in that mats composed of silicone rubber are arranged at least on the lower end face of each core, for the purposes of shock absorption and electrical insulation.
11. Method according to Claim 9, characterized in that mats composed of silicone rubber are arranged on both end faces of each core for the purposes of shock absorption and electrical insulation.

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