RS52864B - Delta magnetic core for three-phase transformer - Google Patents

Abstract

The Delta magnetic core of a three-phase transformer, the diameter of the described circle of core d, consists of three identical canoes K made by winding a packet of transformer strips connected to surfaces S, in which each canoe (K) is obtained by successive packet winding (P1, P2 , P3, P4 ... Pi ... Pn) with displaced beginnings relative to the previous ones for margins (m2, m3, m4 ... mi ... mn) on a square rounded pattern (A × B / R) of different a band of constant widths (w1, w2, w3, w4 ... wi… wn) in the heights of deposits (h1, h2, h3, h4 ... hi… hn) with a cross-section of half of a toothed circle of diameter (d) whose projecting lateral edges flat coiled packages (P1, P2, P3, P4 ... Pi ... Pn) on one side lie in a plane inclined with respect to the non-normal coiling axis by 30 ° and, in conjunction with the other canoe (K), form axial channels for cooling the core a on the other hand, they lie on the surface of the tube around a pattern (A × B / R) with a diameter (d) leaving slight edges on the outer surface of the pole for better arrangement of the electric field and also facilitated winding of the coils.

Description

Technical field to which the invention relates

This invention belongs to the field of electrical engineering, i.e. basic electrotechnical elements, and more precisely to the field of three-phase transformers.

According to the International Classification of Patents, the invention has the designation H 01F 30/12.

Technical problem

The technical problem solved by this invention is how to structurally solve the delta magnetic core of a three-phase transformer by winding it from standard strip widths of transformer sheet on standard machines with one controllable axis, with negligible deformations of the material, without technological waste of material and with a coefficient of fulfillment of the ideal circle greater than 90%.

State of the art

Three-phase transformers belong to the group of basic electrotechnical elements and basically consist of a magnetic core and three pairs of primary and secondary windings.

Magnetic cores of three-phase transformers are most often made of transformer sheet, i.e. steel with a high silicon content formed into very thin plates.

In the production of three-phase transformers, the most common type of magnetic core is the E-core, which is made by stacking a large number of specially cut parts from transformer sheet. The E-core has three pillars connected to four yokes where one pillar and two yokes belong to the end stages and only one pillar to the middle stage. The end columns are made of trapezoidal sheets with 45° angles, the middle column is made of double arrow-shaped sheets with 90° angles, and the two yokes together are made of trapezoidal sheets with a V-cut of 90° in the middle. The three phases of the transformer are in mutually different relations because they are spatially distributed in the direction and the magnetic fluxes of the end and middle phases cross different lengths of their paths. This feature of the three-phase transformer introduces asymmetry of electrical quantities into transmission lines and consumers of the energy system. The magnetic E-core of such a three-phase transformer has several thousand parts, the waste when cutting parts of the middle pole and yokes is over 5%,

Great accuracy is required when cutting and stacking, and special weights are required when forming the structure.

Three-phase magnetic delta cores have three poles arranged with their centers in the vertices of an equilateral triangle, and with four half yokes, each pole is connected to two half yokes of the other two poles of the magnetic core. This symmetrical relationship of each phase to the other two phases makes a completely symmetrical magnetic three-phase system. Today, delta magnetic cores are rarely used in practice due to the very complicated known manufacturing methods.

Today, the coiled magnetic cores of any electrical machines have many advantages compared to cut and stacked ones: a simpler way of manufacturing, lower magnetization currents, and production is not burdened with technological waste.

French patent FR 2 518 306 provides a solution for a delta magnetic core of a three-phase transformer of an extremely complicated construction with special rings for connecting and connecting the poles of the three phases.

American patent US 6,683,524 BI provides a solution for a three-phase wound magnetic delta core, which is the relevant prior art for the invention of the present application. The difference between these two inventions is in the choice of available strips, the degree of geometric filling of the pole circle and the large deformations of the material due to twisting when crossing the canisters of the transformer sheet strips. The basic form of this solution, in addition to 26 more demanding ones, is the shape of a column of a regular hexagon whose known ratio of the area to the area of the described circle is equal to 0.827699.

The patent application RS P-2008-0403 can be marked as the most relevant state of the art for the invention from the subject application. Winding transformer sheet tapes with shearing of each subsequent layer in relation to the previous one requires a winding machine with two controllable axes and a high tension of the wound tape, in order to ensure a thickened winding of the tape due to the shearing of the layers. Because of this, the wound material suffers stretching and twisting stress, which deteriorates its original characteristics, and it is necessary to anneal the magnetic cores in order to restore the characteristics of the transformer sheet. When the tapes are wound with a larger width, which is inevitable with larger and larger transformers, the occurrence of the mentioned deformations is all the more pronounced. By searching the patent documentation and reviewing the professional literature in this field, no similar solution to the technical problem was found.

Exposition of the essence of the invention

The delta magnetic core according to this invention consists of three identical rectangular coils connected to each other by contact on the analog sides that form the poles of the three-phase transformer, and the remaining two coils are at an angle of 60° with the analog sides of the second coil and form the yokes of the three-phase transformer, it is characterized by the fact that each coil consists of several packages of coils with a rectangular cross-section made by winding strips of transformer sheet of uniform width, and each package except the first and the outer edge of the second one is moved in relation to the outer edge of the previous one so that the outer edges of all packages lie in a plane inclined at 30° to the normal of the winding axis and the opposite outer edges of the packages touch the described circle of the delta core column. When two kanuras are connected along inclined planes, a column of one phase, two half-columns of other phases and two pairs of half yokes at angles of 60° are obtained, and by adding a third kanura, the assembly is closed and three columns connected with six yokes are obtained. The cross-sections of the columns are approximately circular in cross-section with rhomboid cavities along the connection plane and with the diameter of the described circle of the delta core of the designed transformer.

The advantage of this construction of the delta core compared to the cores known in the state of the art is in the increased filling of the desired ideal circular shape of the column through the optimal selection of the widths of the standard strips and the thickness of the package. This construction is performed on the simplest machines with only one controllable axis, with minimal tension during winding and without stress on the twisting of the tapes, because they are wound straight over each other, and the need for subsequent annealing of the core is lost. Rhomboid channels along the connection plane in the core pole always contribute to the cooling of the core, and thus, with larger transformer power units, additional insertion of channels is avoided, which in previous constructions reduce the coefficient of the achieved filling of the ideal surface of the described circle of the pole. The outer edges of the toothed circle are slightly sharp, so they contribute to an easier winding of the phase windings compared to the known solution with very sharp outer edges of the core.

Brief description of the draft images

The invention is described in detail on the example of execution shown in the drawing in which: Figure 1. - shows two projections with the indicated section of the delta magnetic core according to this invention,

Figure 2 shows a three-dimensional view of a delta magnetic core according to the present invention with a cross section of one pole shown

Figure 3. - shows a detailed cross-section of a canoe with transformer sheet winding packages.

Detailed description of the invention

In order to fully understand the proposed invention, it is necessary to give the meanings of the call signs, and according to Figure 1 they read:

K - canoe

A - the larger dimension of the square rounded template on which the coiling of the kanura is performed B - the smaller dimension of the square rounded template on which the coiling of the kanura is performed R - the radius of rounding of the square template on which the coiling of the kanura is performed

S - plane of joining two canoes,

according to figure 2:

K - canoe

C - cross section of the core column

S - plane of connection of two canoes i

according to figure 3:

x,y-axes of the Cartesian rectangular coordinate system

d - diameter of the described circle of the pole of the delta magnetic core

S - a line connecting two canoes

Pl, P2, P-., P4... Pl... Pn- Consecutive packages wound from strips of transformer sheet of different widthwl,w,,w3, w4... wr.. w„- width of strip of transformer sheet corresponding to the package^, h2, h3, h4... hr.. hn- height of the coiled tape stack corresponding to the package2, m3, m4... mr.. mn- distances of the beginnings of the corresponding packages in relation to the previous ones - margins

By successive winding of packages PI, P2, P,, P4... PI... P„ { Figure 3) with offset beginnings compared to the previous ones by the margin2, m-. <m4... mr.. mnna square rounded pattern AxB/R ( Figure 1) of different widths of tapes\. w2, w:.,\ v4... wr.. wl, in stack thicknesses^ h2, h- i, h4... hr.. hn (Figure 3) a square canoe K (Figure 1) is obtained with a cross-section of half of a toothed circle of diameter d, marked in Figure 3, whose protruding side edges of the package Pf, P2, P:i, P4... Pr. 3), and by joining three of identical canures K on the surfaces (picture I), a delta magnetic core is obtained, shown in picture 2, according to this invention.

It can be noticed that the section C-C from Figure 1 consists of three canutes K connected by the surface S, which means that the entire magnetic delta core is composed of three identical canutes K. Canute K is made by winding a package of transformer sheet strips, figure 3. First package P; (Figure 3) is wound from a strip of width w, to the thickness of the layer /?, or in the number of turns it amounts to hs /thickness of the strip of transformer sheet. It should be noted that the number of threads, that is, this quotient does not necessarily have to be adopted as the nearest whole number, but as many integer threads are wound and for the rest of the decimal number, the corresponding part of the circle is wound and the wound strip is cut straight. The width of this strip w] is chosen as the most favorable of the available strips of width less than d/2. The thickness of the layer hx of the package Pfs is determined by placing, according to Figure 3, a chord of length ve on the circle d such that the x axis is bisectoral and thus the lowest value of the abscissa x is defined, which is the position of the left edge of the package P], and the right edge of the package i° must be located at the abscissa value = - d<*>cos30°. The absolute difference of the abscissas of the left and right edges of the package Px is /z, = the thickness of the package stack Pt.; The second package P2 is obtained by continuing to roll a new strip of width w2 and of the stack thickness h2 by choosing the first of the available strips smaller than d/2 for the width of the strip and, according to Figure 3, it is placed along the length w2 along the right edge of the package P| while touching the circle of diameter d with its upper point. By drawing a horizontal line from the lower point of the length w2 to the intersection with the S axis (picture 3), the value of the abscissa for the end of the second or the beginning of the third package is obtained. By dragging the right edge of package P2 as a vertical longer length w2, a rectangle is obtained represented as package P2 (picture 3). The absolute difference of the ordinate y between the lower sides of package P2 and package Pi represents the value of the margin m2 (picture 3). packages. So, the rule is to construct a rectangle whose left longer side is equal to the width of the selected strip W| and is placed along the right edge of the previous package, the upper left theme touches the circle of diameter d/2 (Figure 3) and the lower right theme is obtained by drawing the horizontal from the lower left vertex to the intersection with the line S, Figure 3, which passes through the center of the circle of diameter d and stands at an angle of 30° to the x axis.

When the right edge of the package gets so close that it is impossible to construct a rectangle in the previous way, then strips of width less than d/2 are chosen, the right edge of the package is determined by placing the available width of the strip Wjkao along the y axis so that the upper point touches the circle of diameter d and the lower point touches the line S, Figure 3. Also, as in the previous cases, the thickness of the package deposit Pjse is obtained as the difference between the abscissa of the right edge of the i-th channel and the right edge of the i-1 kanura. Absolute difference of ordinate y; between the bottom pages of the package Pji package Pm represents the value of the margin mjFigure 3.

This procedure of tape selection continues until the narrowest available tape, which is wound in the thickness of the layer, its beginning, ie. margin mnse is determined in the same way as already described here in figure 3.

The rounding of the square canister, size R, Figure 1, can be chosen arbitrarily, but it is in principle proportional to the highest connected voltage of the transformer and can be taken as a guideline as R=lmm/kV, which means that for the highest voltage transformer lOkV R=l Omm and for the highest voltage transformer 11 OkV R= 11 Omm.

By connecting three such canuras along the line S, Figure 3, that is, along the planes S, Figure 1, and wrapping them with a polyglass tape, a compact delta magnetic core with a pole diameter d of a cross-section in the shape of a jagged circle with a filling coefficient of an ideal circle d, Figure 3, over 90% with three windows A x B /R, s\ and 1. enough to accommodate the coils according to the calculation is obtained.

Of course, while maintaining the same principle of the invention, the details of construction, technological preparations and forms of execution can be changed within wider limits compared to those described and shown, without deviating from the scope of the presented invention.

Claims (1)

1. The delta magnetic core of a three-phase transformer, with the diameter of the described circle of the core d, consists of three identical coils K made by winding a package of transformer sheet strips, connected on the surfaces S, indicated by the fact that each coil (K) is obtained by successively winding the package (Pi, P2, P:s, PA... Pi... Pii) with offset beginnings compared to the previous ones for the margins (m2, m:t, m4... mr.. mn) on a square rounded pattern (AxB/R) of different strips of constant widths ( w], w2, w:i, w4... wi... wii ) in stack heights ( h^ h2, h,, h4... hl... hn) with a cross-section of half a serrated circle of diameter (d) whose protruding side edges of flat-wound packages ( Pi, P2, P. 3, PA... Pl... PH) on one side lie in a plane inclined in relation to the normal of the winding axis by 30° and in connection with the second tube (K) they create axial channels for cooling the core and on the other side they lie on the surface of the tube around the template (A*B/R) of diameter (d) leaving slight edges on the outer surface of the column for a better distribution of the electric field and easier winding of the coil.