WO2012155967A1

WO2012155967A1 - Low-noise transformer

Info

Publication number: WO2012155967A1
Application number: PCT/EP2011/058027
Authority: WO
Inventors: Peter Hamberger; Marion LACKNER; Martin Mairinger
Original assignee: Siemens Aktiengesellschaft
Priority date: 2011-05-18
Filing date: 2011-05-18
Publication date: 2012-11-22

Abstract

The invention relates to a low-noise transformer having yoke parts (2) and limb parts (3), each being formed from stacked laminations of a grain-oriented magnetically soft material having a preferred magnetic orientation (8), wherein the yoke parts (2) contain laminations (20) on which a permeability barrier (5) extending in the preferred orientation (8) is formed such that the permeability to a magnetic flux varying from the preferred orientation (8) is reduced.

Description

description

Low-noise transformer

Technical area

The present invention relates to a low-noise

Transformer or a low-noise choke, with yoke parts and leg parts, each made of layered

Laminations of a magnetic preferred direction

having grain-oriented soft magnetic material are formed. Furthermore, the invention relates to a method for producing a magnetic core.

State of the art

In electrical transformers or inductors, as they are commonly used in energy distribution networks, thigh and yoke parts consist of a stack of

Sheet metal lamellae, the usual way of an electric sheet of a grain-oriented soft magnetic material having a magnetic preferred direction. Such grain oriented materials are also referred to as Grain Orientated Electrical

Steel, also known as GOES for short. Depending on the degree of

Orientation, that is the deviation of the edge length of the crystallites from the rolling direction, distinguishes so-called conventional grain-oriented electrical steel

(Conventional Grain Oriented CGO) of electrical steel with high

Permeability (High Permeability Grain Oriented HGO), in which the deviation from the rolling direction is small and has a very high permeability in the rolling direction. The permeability is a substance-dependent factor, which is the magnetic flux density (induction) with the magnetic

Field strength (excitation) linked. A high permeability or permeability thus means a high flux density with respect to a certain field strength. The so-called B800 value of a material indicates the value of the magnetic flux density at an excitation of 800 A per meter. At a

highly oriented electrical steel sheet (HGO), the B800 value is at least 1.88 Tesla. Due to the greater expense of manufacturing, the high-grade grades of HGO materials are more expensive compared to CGO materials.

A grain-oriented electrical sheet is therefore anisotropic, that is, the permeability is directional, in

magnetic preferred direction (rolling direction), it is a multiple higher than in the transverse direction.

In the leg or yoke of an electrical transformer or a choke, the magnetic flux also runs in the

Essentially in the direction of the thigh or

Yoke axis, so that this electrical steel is used, the rolling direction points in the direction of the axis. But there are also different areas, for example, in the mouth area of a three-arm transformer, that is in the impact area between the middle leg and yoke, where one of the

Leg axis deviating ("rotating") flow component occurs. This one of the magnetic preferential direction

deviating flux portion causes a significant amount of operating noise, since the magnetostriction of a

soft magnetic material transverse to the preferred direction is many times higher than in the rolling direction.

From practical experience of transformer construction is known that it is favorable for the construction of low-noise transformers, if for the core of higher quality material, ie a

Material with a high B800 value is chosen. Particularly favorable is a highly oriented silicon steel sheet (HGO) with an induction of more than 1.88 Tesla at one

magnetic excitation of 800 A per meter. You know, the better the grain orientation, that is, the higher the

Anisotropy of the magnetic material, the lower the tendency of the noise emission. The material costs of a But transformer cores made of a HGO material are in the

Compared to a CGO higher.

In order to achieve the lowest possible noise emission, it has already been proposed in DE 1 488 357 to use an electrical steel strip in the yoke part of a transformer which has a cube texture with two magnetic preferred directions perpendicular to one another. Such a

But transformer core is expensive because of the high material costs in the production.

When a transformer or choke coil is to be installed near a living area, the emission of operating noise becomes increasingly important. The problem of noise emission from transformers or chokes is still not solved satisfactorily.

Presentation of the invention

It is an object of the invention to provide a low noise

Specify transformer in which the effort in the

Production is as low as possible. This task is done by a transformer with the

Features of claim 1 and with a method for

Production of a transformer core solved with the features of claim 11. On advantageous embodiments of

Invention refer to the respective dependent claims.

The invention is based on the idea of constructively increasing the anisotropy of yoke laminations by suitable measures, so that their magnetic permeability to a deviation of the magnetic flux from the

Preferred direction is reduced. This reduces the magnetic flux component transversely to the rolling direction. It reduces the magnetostriction of the core during operation and thus the noise emission. According to the invention therefore include the Yoke parts yoke laminations with one in magnetic

Preferred direction extending permeability barrier. This permeability barrier extends in the rolling direction of the yoke plate, ie in the direction of the yoke axis. The barrier may be formed, for example, in its length continuously between the two ends of a yoke metal sheet or shorter. It is only important that a barrier is set against a flow crossing across the rolling direction of the electrical steel. The permeability barrier thus has the effect that the formation of so-called "rotating flux fractions", that is from the

Preferred direction deviating flow components, suppressed or at least made more difficult. As stated, this has the consequence that the magnetostriction and thus the noise emission are lower. Although because of the design

forced flux guidance to increase the magnetic losses slightly outweighs the beneficial effect of less noise, especially if the

Transformer should be installed near a residential area and the acceptance threshold opposite

Noise emission is always lower.

There are now several options

Technically realize permeability barrier,

the only important thing is that where

Flow components occur transversely to the preferred direction, the magnetic permeability is reduced.

It can be structurally favorable if the permeability barrier is formed at least in the region of the junction between a middle leg part and an upper or a lower yoke part of a transformer. In the area of the impact, in the case of a three-arm-core transformer, so-called "rotating" flux components occur there, the formation of which is thereby made more difficult.

It has been found that it may be beneficial if the axial length of the permeability barrier is greater than that Width of the laminations of the middle leg portion of

Transformers.

In a particularly preferred embodiment

be provided that the permeability barrier in the form of one or more extending in the preferred magnetic direction slot or an air gap is made. Such slots can be produced, for example, by punching already in the manufacture of the electrical steel, or on the finished cut yoke laminations. An air gap, for example, in a position of the yoke stack of sheet metal by juxtaposed

Sheet metal strips are realized. In order to facilitate the handling of the yoke laminations, it may be advantageous if the permeability barrier is formed by one or more arranged in the manner of a perforation line in the yoke plate assembly of slots. The

Slits can in a known manner by punching or

Cutting be generated.

In a variant of the invention is provided, the

Permeability barrier to realize that the yoke laminations are cut from a coil, which consists of strip-shaped portions, with portions of high and low permeability in the direction of

magnetic preferred direction lying side by side. Again, the low permeable field boundaries across the sheet thickness cause less permeability to magnetic flux components whose direction is transverse to the preferred magnetic direction. These low permeable field boundaries can be generated, for example, by laser irradiation, by etching or by other technologies. An advantage here is that the desired barrier function is already present in the semi-finished product (coil).

In another variant, the permeability barrier can be realized by using yoke laminations which are cut from an electric sheet, that is coil, which is already in magnetic

Having preferred direction extending groove-shaped recesses. These recesses can be produced, for example, in the manufacture of the electric sheet, so cold rolling, by appropriately shaped work rolls. It is also conceivable that the recesses may be otherwise

be prepared for example by a chemical pretreatment.

In a particularly favorable embodiment, it is provided that a yoke member is composed exclusively of yoke laminations, each of which with a

Permeability barrier is equipped.

The invention also relates to a method for producing a magnetic core, in particular a transformer core or a choke core, consisting of leg parts and yoke parts each stacked from laminations

grain-oriented soft magnetic material with a preferred magnetic direction. The method according to the invention is characterized in that, in the production of a yoke part, laminations are used, on each of which at least one permeability barrier is formed. This permeability barrier is designed such that during operation of the transformer or the throttle, the formation of a deviating from the preferred direction magnetic flux

counteracted. In this way, a low-noise transformer or a throttle can be produced inexpensively.

BRIEF DESCRIPTION OF THE DRAWINGS For further explanation of the invention, reference is made in the following part of the description to the drawings, from which further advantageous embodiments, details and Developments of the invention can be seen by way of non-limiting embodiments.

Show it:

Figure 1 shows an embodiment of the invention, which shows in a schematic representation of upper and lower yoke laminations, on each of which a permeability barrier is formed in the form of an air gap;

Figure 2 shows a possible formation of a permeability barrier on a yoke lamination with groove-shaped recesses in an enlarged

Cross-sectional view ·

FIG. 3 shows another embodiment of the invention,

which shows a yoke lamination, on which the permeability barrier is formed by slots or recesses of different length and shape;

Figure 4 shows a portion of a GOES electrical steel strip with a view of the strip surface, which is subdivided into subfields and a plurality of extending in the preferred direction of the sheet metal strip field boundaries (permeability barrier) with different permeability.

Embodiment of the invention

FIG. 1 shows in a simplified representation a

Embodiment of the invention. The magnetic core of a three-limb core transformer 1, whose legs 3 are designated by the letters R, S and T, can be seen. Each leg 3 carries in a conventional manner a winding arrangement, which is not shown in the drawing for simplicity. In the production of the yoke laminated core of the

Three-limb core transformer 1 were in the yoke part 2 yoke Laminations 20 with a permeability barrier 5

used; As indicated in the drawing, the subscribed upper and lower yoke Blechendlamelle 20 is composed of juxtaposed part plates together. The lying on a plane of the yoke sheet pile

Partial sheets are arranged at a distance from each other.

This creates a divided by the air gap 18

Jochteil 2. The air gap 18 acts for that portion of the magnetic flux, transverse to the preferred direction eighth

is directed, like a barrier or as a barrier. The anisotropy is increased structurally by this sheet metal design. This ensures that in the case of a

Excitation state of the transformer, in which the legs R and S are excited, the formation of a "rotating"

magnetic flux, which originated in the area of

The shock has 10 and extends in the yoke in the direction of the unexcited leg T, not over the

Middle leg, but over the outer, not excited leg T closes. Since the magnetic flux is quasi forced by the design in the yoke 2 in the preferred direction 8 of

Material continues to flow, reduces the unwanted transverse component of the magnetic flux. A smaller one

Cross component of the magnetic flux is favorable for low noise. On the other hand, the structurally enforced flow control has over the outer, not excited

Due to the law of flooding, leg T results in a circulating flux component closing around the right-hand transformer window (in FIG. 2), which slightly increases the magnetic losses of the transformer core 1. This increase in magnetic losses is but in purchasing

taken because the beneficial effect of noise minimization outweighs.

At the corners, yoke laminations 20 and laminations of the legs 3 abut one another at an angle and, as usual, are mitered and overlapped. In the illustrated embodiment, the air gap 18 extends from a left end 14 continuously to a right end 15 and extends to the respective Miter cut 11, 12th As explained in more detail below, the length of the air gap 18 but also be shorter; The air gap 18 does not necessarily have to be continuous, but may also be designed in the manner of a perforation.

FIG. 2 shows in cross-section a sheet-metal lamella 20 on which recesses 7 are formed on one side or on both sides. Here, as the permeability barrier does not go beyond the entire sheet thickness. Such a recess 7 may have different shape in cross section, as long as only an effective limit or barrier function with respect

Forming a magnetic flux across the rolling direction is achieved. You can, for example, by rolling or

Milling be made. The electrical steel can

for example, during cold rolling so shaped.

Figure 3 shows a detailed representation in the joint area 10 between a yoke sheet metal plate 2 and a

Center leg plate 3 with roof-shaped

Miter cut 13. The joint area 10 is marked in FIG. 3 with hatching. The permeability barrier 5 here consists of three adjacent arrangements of slots 17. These slots 17 extend in the preferred direction 8, but are designed differently. The upper over a length 9 extending slot arrangement consists of

Slits 17 and connecting webs 21 (perforation line). The ratio between the length of a slot 17 and the length of a web 21 is selected so that the

magnetic permeability for the magnetic flux across the rolling direction 8 of the electric sheet 20 is reduced. The middle barrier is a continuous straight line in

Preferred direction 8 extending slot 17; The underlying barrier consists of two slots 17 on both sides of the roof-shaped miter cut 13. As in FIG. 3

shown, the length 9 of these permeability barriers 5 may be different, for example, shorter than the width 16 or longer, to the mitres 11 at the ends 14, 15 of the yoke plate 20 lamination. Figure 4 shows an eruption of an electrical steel 19 in a plan view of the belt surface. The electrical steel 19 consists of a grain-oriented soft magnetic material and is composed of strip-shaped portions or subfields 6: The reference numeral 8 is again the

Preferred direction, that is, the rolling direction of the electrical steel 19 characterized. In the electrical steel strip 17, several low-permeability layers running parallel to one another in the rolling direction 8 are present

Field boundaries 4 formed. These low permeable

For example, field boundaries 4 may be used in the rolling process of the electrical steel 17, e.g. as already shown above are produced in the form of cross-sectional reductions. A

Permeability barrier 5 can also in a the

Rolling process following processing step are prepared, as already shown above by a cutting ^¬ or slit process, which may also be partially interrupted (perforation) or by another mechanical or chemical action on the band-shaped soft magnetic material, for example by a laser treatment. It is conceivable that influence is exerted on the material property itself, so that a barrier effect that occurs over the sheet thickness comes about. A significant advantage of the invention can thus be seen in the fact that the introduction of permeability barriers 5 can constructively reduce the noise emission without requiring expensive, highly permeable grain-oriented

Material must be used. The core production is cheaper. As a result, transformers can be manufactured cost-effectively, which cause less operating noise. Even if with the inventive measure a

small increase in magnetic losses must be accepted, the advantage of lesser outweighs

Noise and cost advantage in the production of a

low-noise transformer, because it can be dispensed with higher quality material. Although the invention has been further illustrated and described in detail by the preferred embodiments set forth above, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention

To leave the scope of the invention. Of course, the principle explained with the aid of a 3-legged core transformer can equally well be applied to transformers with more than three legs on the magnetic core of electric reactors and other electrical machines.

Compilation of the reference numbers used

I core of an electrical transformer

2 yoke part

3 leg part

4 field boundary, low permeability

5 permeability barrier

6 subarea

7 deepening

8 magnetic preferred direction

9 length

10 impact area, junction area between 2 and 3

II miter cut upper yoke part

12 miter cut lower yoke section

13 Miter cut in the joint area

14 end of a yoke sheet metal lamella

15 end of a yoke plate lamella

16 width

17 slot

18 air gap

19 electrical tape

20 yoke plate lamella

21 footbridge

Claims

claims

1. Low-noise transformer, with yoke parts (2) and

Leg parts (3), each layered

Sheet metal laminations of a magnetic preferred direction (8) having grain-oriented soft magnetic

Material are formed, wherein the yoke parts (2)

Lamination (20) containing an in

Preferred direction (8) extending permeability barrier

(5) is designed so that for one of the

Preferred direction (8) deviating magnetic flux is the permeability decreases.

2. Transformer according to claim 1, characterized in that the permeability barrier (5) at least in

Area of the shock (10) between a yoke part (2) and a middle leg portion (3) is formed.

3. Transformer according to claim 2, characterized in that the permeability barrier (5) has a length (9) which is greater than a width (6) of the central leg portion (3).

4. Transformer according to one of claims 1 to 3, characterized in that the permeability barrier (5) by at least one in the preferred direction (8) of a

Laminated plate (20) formed slot (17) is made.

5. Transformer according to one of claims 1 to 3, characterized in that the permeability barrier (5) by at least one extending in the manner of a perforation arrangement slot-shaped recesses of a sheet metal plate (20) is formed.

6. Transformer according to one of claims 1 to 3, characterized in that the permeability barrier (5) are formed by low permeable field boundaries (4), the strip-shaped portion (17) of the sheet metal plate (20) separate from each other.

7. Transformer according to claim 6, characterized in that the lower permeability of the field boundaries (4) by a laser treatment of the sheet metal plate (20) forming soft magnetic material is produced.

8. Transformer according to one of claims 1 to 3, characterized in that the permeability barrier (5) by at least one of the sheet metal plate (20)

formed, in the preferred direction (8) extending groove-shaped recess (7) is formed.

9. Transformer according to claim 8, characterized in that the at least one recess (7) by a

Rolling process or by a chemical pretreatment in the production of the electrical steel sheet from which the sheet metal plate (20) is made formed.

10. Transformer according to one of claims 1 to 9,

characterized in that a yoke part (2)

is composed exclusively of laminations (20) having a permeability barrier (5)

is trained.

11. A method for producing a magnetic core (1), in particular a transformer core or a choke core, each consisting of laminations leg portions (3) and yoke parts (2) of a grain-oriented soft magnetic material having a magnetic preferred direction (8), characterized in that in the manufacture of a yoke part (2) sheet metal laminations (20) are used, the one

Permeability barrier (5), which is designed so that a deviation of the magnetic Flow of the preferred direction (8) is counteracted.

12. The method according to claim 11, characterized in that the permeability barrier (5) by at least one of the sheet metal plate (20) formed in the preferred direction (8) extending groove-shaped recess (7) is formed.

13. The method according to claim 12, characterized in that the at least one recess (7) by a rolling process or by a chemical pretreatment in the production of the electrical steel sheet from which the sheet metal plate (20) is made, is formed.

14. The method according to any one of claims 11 to 13,

characterized in that in the production of a yoke part (2) only laminations (20) are used with a permeability barrier (5).