WO2022225498A1

WO2022225498A1 - Three-phase transformer

Info

Publication number: WO2022225498A1
Application number: PCT/UA2021/000065
Authority: WO
Inventors: Леонид Адамович БИЛЫЙ
Original assignee: Леонид Адамович БИЛЫЙ
Priority date: 2021-04-19
Filing date: 2021-07-21
Publication date: 2022-10-27
Also published as: EP4102522A1; EP4102522A4; WO2022225498A8; UA128371C2

Abstract

The invention relates to the field of electrical engineering, and more particularly to transformer design, and can be used in all sectors involving activity related to the production, use and repair of transformers. A three-phase transformer comprises primary and secondary main windings (3), and a three-dimensional magnetic system made of plates of electrical steel and formed by six regular triangular prisms connected to one another by a common rib to form a hexagonal prism with a six-armed star in cross section. The adjacent sides of the star form legs (1) of a magnetic core, and the independent sides form a hexagonal yoke (2). The plates are vertically compacted by central fasteners (5) and lateral fasteners (6). Main windings and additional windings are provided, which are divided in half and arranged according to phases on the legs, the latter being spaced apart by an angle of 60°. The magnetic system is configured so that the ratio of the width of a leg to the width of the yoke is equal to two and the ratio of the height of a leg to the width of an arm is greater than five. The technical result of the invention is that of standardizing the structure of a three-dimensional magnetic system, reducing the weight and dimensions thereof, and combining within the transformer the functions of a higher harmonic filter, a balancing device and a voltage stabilizer.

Description

Three phase transformer

The invention relates to the field of electrical engineering, in particular to the design of transformers and can be used in all industries that need devices that can transform high-quality energy (without higher harmonics), independently eliminate voltage distortions in the event of an unbalanced load, independently regulate smoothly and over a wide range voltage when the load changes, devices with significantly higher reliability and service life.

Such properties of a transformer can only be provided by a spatial magnetic system that adequately reproduces or models the phenomenon of electromagnetism, the form and physics of which is to cover the current conductor with a magnetic circuit, while such metamorphoses as the need to replace the bulk field with a plane-parallel one, the scattering of this field into the surrounding space and etc., but the manufacture of a spatial magnetic circuit requires a larger amount of steel.

Given that the design of modern transformers is carried out with a long-term and unrelenting trend towards the highest possible use of active materials, simplification of manufacturability, weight reduction and size reduction, the question arose of creating a spatial magnetic system with costs comparable to the costs of manufacturing E-shaped flat transformers.

Three-phase spatial radial magnetic cores of increased compactness are known, the rods and yokes of which are formed from two groups of herringbone elements, which have different lengths, and part of the sections The yoke is made of parallelogram-shaped elements with angles of 60° and 120° (Patent of Ukraine for invention UA 100077С2, Patent of Ukraine for utility model UA 99327). Such magnetic circuits have a number of disadvantages, among which the main ones are: the impossibility of installing separately manufactured windings on the magnetic circuit rods, since the rods have a geometry “in the form of a chevron of various lengths”. Winding the winding on the finished magnetic circuit greatly complicates the technological process of manufacturing the transformer. The genesis of the structure of the magnetic circuits from a planar shape to a spatial one was carried out by the authors in one plane by concentric placement of phases, which only eliminated the magnetic asymmetry of the magnetic circuit, but did not affect the improvement of the conditions for the electromagnetic process, leaving the coverage of the magnetic field by current, which causes the presence of stray fields, power losses etc.

A spatially symmetrical magnetic circuit is known, having an upper and lower wound yokes interconnected by rods, while the geometry of the cross section of the rods and yokes at the junctions is made with a square cross section (RF Patent RU N "2380780 Cl). Such magnetic circuits with spatial arrangement of rods only eliminate the magnetic asymmetry of planar W-shaped cores, and the technical result in reducing losses in steel is achieved only through the use of amorphous steel, which can also be achieved in a W-shaped magnetic circuit. Due to the low mechanical strength of amorphous steel (brittle like glass), special requirements are imposed on the designs of such cores and the conditions for their production, since the magnetic circuit is a supporting structure that holds the entire active part. Amorphous steel does not allow excessive weight loading, which the inventors do not take into account. It is also known to design a magnetic core with an inner part (rods) made of a soft magnetic material, around which a screen is at least partially located, which has a laminated structure of at least one soft magnetic material, and between the inner part of the magnetic core and the screen there is a device for creating axial pressure on the inner part of the magnetic circuit, and the screen is divided into segments and its length in the axial direction is equal to or greater than the axial length of the coil frames located around the transformer magnetic circuit (Patent of Ukraine for the invention UA N ° 88942 C2).

Above, the reason for the appearance of the so-called stray fields, that is, magnetic fields, the lines of force of which are linked to only one winding, was indicated, and this reason lies in inadequate modeling of the phenomenon of electromagnetism.

Instead of the spatial coverage of the current by the magnetic field in the transformer, the coils (current) cover the magnetic circuit (field). Violation of the laws and phenomena of nature gave rise to a number of negative consequences, including stray fields. Their physics is quite complex and there are still no unified methods for their calculation and ways to eliminate them. The screen proposed by the author closes on itself some part of the stray field and changes the location of the transformer power losses, but does not eliminate them. In addition, stray fields determine the inductive resistances of the windings they cover, and additional losses in copper, in addition to ohmic ones. The screen cannot close this part of the scattering flows onto itself. And it is impossible to predict “that the orientation of the laminated screen structure is directed parallel to the possible (?) direction of the scattering flux,” since it is impossible to predict the configuration of the scattering phenomenon itself. Can there be an alternative to the fight against the consequences of stray fields, other than converting them into a working magnetic field by surrounding the windings with a volume-spatial magnetic system? Apparently it doesn't exist.

There is also known a spatial magnetic circuit for filter transformers with rods with yokes placed in a circle, which form a multi-beam star in plan and which, in order to reduce magnetic asymmetry, is made of two identical parts joined in rods (SU Ns 1714697 A1).

Firstly, magnetic asymmetry disappears not from the joining of “two identical parts joined in rods”, but due to their spatial arrangement; secondly, large funds are spent on the manufacture of filter transformers designed to eliminate higher harmonics in voltage and current curves. Costs and harmonics disappear in transformers with a spatial magnetic system, which almost completely covers the windings. Such transformers transmit only the first harmonic at any saturation of the magnetic circuit, while filters have a narrow efficiency range.

The closest to the proposed set of features and technical results is the device-prototype three-phase transformer Patent of Ukraine for the invention UA Ns 84746.

A three-phase transformer, which contains low and high voltage windings in each phase and a folded magnetic system, characterized in that the magnetic system consists of a yoke and six rods arranged in the form of a six-beam star with spatial angles of 60 degrees between them and outside covered by the yoke , on three rods through one there are phase windings as part of the primary and secondary windings of one phase, the other three rods are free from windings and are shunt, on each of the six sections of the yoke there is an additional bias winding, two for each phase, which are located in different side of the respective phase winding, the magnetic system is made with a ratio of its width and the width of the rods greater than one.

Three-phase transformer according to claim 1, characterized in that the magnetic system is made in the form of a cylinder, the cross section of which is a six-beam star of rods, covered by an annular yoke.

Three-phase transformer according to claim 1, characterized in that the magnetic system is made in the form of a hexagonal prism, the cross section of which is a six-beam star of the rods, covered by a hexagonal yoke.

Signs of the prototype, which coincide with the design, according to the invention is that the magnetic system consists of a six-beam star rods with spatial angles of 60°, covered by a six-sided yoke.

The prototype has a number of disadvantages, the main of which are:

1. As is well known, cold-rolled electrical steel is characterized by anisotropy, that is, different magnetic properties along and across rolling. For economical use of steel and obtaining minimal losses in it, it is necessary to match the direction of rolling and the main magnetic flux. Such coincidence when stamping plates according to FIG. 6 - fig. 11 or FIG. 17 - fig. 22 takes place only in one or two rods, and in four or five rods the magnetic losses increase significantly.

2. Inefficient use of expensive electrical steel. The areas of the triangles surrounded by rods and yokes are much larger than the latter, therefore, in the process of stamping plates, most of the steel goes to scrap.

3. The magnetic flux of the rod is closed by two yokes, that is, at the junction of the rod with the yokes, the flux is bifurcated in half due to equality of magnetic conductivities of both yokes. Therefore, the flow of the yokes is half the flow of the rod, and therefore the cross-sectional areas of the yokes and the rod must be appropriate. With serial production, the savings in steel due to a halving of the cross-sectional area of the yokes will be noticeable.

4. In the description of the prototype device, it is explained that "the voltage regulation of the proposed transformer when operating under load is carried out with the help of additional windings placed on the yoke." It is further stated that "smooth adjustment of voltage balancing in the case of complex asymmetric operating modes is carried out by using additional windings placed on the outer yoke of the magnetic system." Thus, two physical processes due to different reasons are functionally connected and their control is entrusted to the same mechanism - additional windings. If we take into account that fluctuations of secondary voltages and their distortion occur, as a rule, simultaneously, it is almost impossible to carry out their simultaneous regulation. In addition, it is also impossible to automate the regulation of such a process, and therefore external intervention in the operation of the transformer is necessary.

The objective of the invention is to improve the production technology and reduce the weight and size characteristics of a spatial magnetic circuit in comparison with the prototype, the combination in the transformer of the functions of a higher harmonic filter, a balancing device and a voltage stabilizer.

The problem is solved due to the fact that a three-phase transformer contains the main primary and secondary windings, a spatial magnetic system composed of electrical steel plates, the magnetic system is formed by six regular trihedral prisms connected to each other by a common edge, thus forming a hexagonal prism with a six-beam star in cross section, the adjacent faces of the star are the cores of the magnetic circuit, and the autonomous faces are the hexagonal yoke, the vertical density of the magnetic circuit plates is provided by the central and side fastening, the main windings are divided in half and additional windings placed phase by phase on the rods with a spatial angle of 60°, the magnetic system is made with the ratio of the width of the rod and the yoke equal to two and the height of the prism to the width of the beam greater than five.

Three-phase transformer according to claim 1, characterized in that the main and additional windings are placed together on rods with a spatial angle of 120°.

Three-phase transformer according to claim 1, characterized in that the spatial magnetic circuit is made of amorphous electrical steel with a thickness of 10 to 30 microns.

The listed set of essential features is sufficient to make the drawings of the claimed design of a spatial magnetic system with windings placed on it according to the usual initial data for design in accordance with the claimed scope of legal protection, that is, the unification of the design of the transformer with minimization of waste when cutting sheets of electrical steel, with the possibility of reducing the weight and size characteristics of the magnetic circuit, the creation of a transformer with new properties.

The essence of the invention and the principle of operation is illustrated by drawings.

In FIG. 1 shows a general view of the transformer.

In FIG. 2 shows the geometry of a plate of a unified magnetic circuit. In FIG. 3 and 4 shows the stacking of magnetic circuit plates in two successive layers. m In FIG. 5 shows a regular trihedral prism.

In FIG. 6 shows the marking of a sheet of electrical steel for laser cutting of magnetic circuit plates.

In FIG. 7 shows a cross section of a magnetic circuit composed of six trihedral prisms.

In FIG. 8 shows the side mounting of the magnetic circuit.

In FIG. 9 shows the central fastening of the magnetic core.

In FIG. 10 shows a winding coil covered by a spatial magnetic circuit (the yoke is removed).

In FIG. 11 shows a winding coil that covers the core of the magnetic core.

In FIG. 12 shows a diagram of the relationship of the magnetic fluxes of the phases of the transformer.

In FIG. 14 shows the electrical connection diagram of the main and additional windings of a three-phase transformer.

In FIG. 13 shows the electrical connection diagram of the main and additional windings of one phase of the transformer.

The following designations are adopted on the figures of the drawings: 1 - rod, 2 - yoke, 3 - main windings, 4 - additional windings, 5 - central mount, 6 - side mount, 7 - stud.

A three-phase transformer (figure 1) contains primary and secondary (main) windings 3 and additional windings 4, the transformation ratio of which is greater than the main ones, a folded magnetic system (figure 1 pos. 1,2). The spatial magnetic system is formed by six regular trihedral prisms (Fig. 5), made by stacking plates (Fig. 2) into successive layers (Fig. 3, fig. 4) and connected by a common edge. The adjacent faces of the prisms serve as rods 1, and the autonomous faces serve as yokes 2.

The magnetic circuit is made of plates of electrical steel, Fig. 2 with a thickness of 0.27 mm, 0.35 mm or from amorphous steel strips with a thickness of 10-30 microns.

The vertical density of the plates of the magnetic core is carried out by the central 5 and side 6 fasteners, the horizontal parts of which are pulled together by studs 7.

There is a causal relationship between the set of distinctive features and the achieved technical result.

The sign regarding the geometric ratio of the width of the rod and the width of the yoke equal to two is significant, because it directly affects a number of technical results.

Firstly, the design of the transformer, the magnetic circuit of which consists only of plates having the geometric shape of an equilateral trapezoid (figure 2), is a unified design.

Secondly, this ratio significantly affects the weight and size characteristics of the transformer, the weight of the yokes of which is half the weight of the rods.

Thirdly, a significant influence of this ratio is the optimization of laser cutting of electrical steel sheets into plates (Fig. 6) and minimization of waste (up to 5%) into scrap metal of expensive material.

The fourth technical result of this essential feature is the one hundred percent orientation of the cutting directions of the plates with the direction of rolling of cold-rolled steel, which significantly affects the reduction of losses and the improvement of the characteristics of the transformer.

The invention provides for the presence in the claimed design of the transformer of a number of essential features that will lead to the emergence of new functions. The first such essential feature is the ratio of the height of the prism and the width of the beam of a six-pointed star to more than five. This ratio provides maximum coverage of the phase windings by the spatial magnetic system. Let us turn to Fig. 11 and FIG. 10, which compares the pictures of the magnetic fields of the coil covered by the spatial magnetic system (Fig. 10) and the coil that covers the rod of a flat W-shaped magnetic circuit (Fig. 11). In the first case (Fig. 10), the geometry of the magnetic circuit evenly distributes the magnetic field over its entire height, which is adequate to the constant electric field strength, i.e. ⁼ const. The second case (Fig. 11) illustrates the uneven distribution of the field along the turn, which is the result of a distortion of the phenomenon of electromagnetism - here the current covers the field. Therefore, the density of the magnetic field of the rod is not uniform, it is intense between adjacent rods and its intensity drops to zero outside the magnetic circuit, that is, the electric field strength is variable

Let's break the coils of figure 10 and fig. 11 into a series of identical segments ^ and calculate the work that the electromagnetic field performs when transferring a charge along a given trajectory, that is, along the length of the coil, etc. From theoretical electrical engineering it is known that such work is called voltage and is determined by the formula ^zit

.

Based on this formula, we determine the voltages of both turns. To do this, we replace the integral by the sum for ⁷¹ segments of the coil, and the derivative by the increment. Get

The sum of the increments of the segments of the coil in both cases is equal to the length of the coils

Let us now find the sum of tensions

For FIG. 10, this sum is equal to the sum of the identical tensions of the segments, which is equivalent to the product of ⁿ by one tension, that is

^{Physically, the product p} _E _± means the presence of only one intensity component of the same amplitude and frequency.

Thus, the turn voltage of FIG. 10 ^ um ^{= n} E1 _{t1G IM has} only the first harmonic and there are no higher harmonics in it.

For FIG. 11 the total tension consists of the terms of the intensities of the segments of the coil, different in amplitude and frequency, that is

S _i E \u003d E _{g 4-} E ₂ _ CH E _p , and E _g E ₂ ··· E _{p> pt0 is} physically equivalent to the presence of higher harmonics in the coil voltage:

Accordingly, the feature regarding the ratio of the height of the prism and the width of the beam of a six-pointed star is more than five is significant, since it fundamentally affects the technical result, which consists in the absence of higher harmonics in the voltages of the transformer, regardless of the degree of steel saturation. Thus, the technical result is to identify a new property of the transformer - to perform the functions of a filter of higher harmonics while simultaneously transmitting power.

The following causal relationship between the feature of the invention and the expected technical result is explained in Fig.12, where the feature is a symmetrical six-ray star of the rods with halves of the main and additional windings placed on them and surrounded by a hexagonal yoke. The consequence of this feature is a physical phenomenon expressed by the electromagnetic interconnection of each phase with two neighboring ones: phase A is magnetically connected to phases B and C, phase B - to phases A and C, phase C - to phases A and B.

With an asymmetric load of the transformer, currents of various sizes flow in the windings of its phases, which cause corresponding voltage drops. Secondary voltages will have different values, this phenomenon is called "voltage distortion" and it is harmful to consumers.

In turn, different winding currents induce different flows, which, due to the presence of magnetic relationships between the phases, are aligned, that is

According to Maxwell's law, the _voltage or ^EMF ^is ^determined by the change in the flow over time

⁼ ^s.

The technical result of this cause-and-effect relationship is the identification of a new property of the claimed transformer, which consists in independent balancing of secondary voltages in the event of its unbalanced load, in other words, the transformer has assumed the functions of a balancing device.

The presence in each phase of the transformer, in addition to the main 3, additional windings 4 allows for smooth and in a wide range of self-regulation of secondary voltages when the load changes by connecting the main and additional windings in series according to the diagrams shown in Fig. 13 for one phase and in FIG. 14 for three phases.

The essence of voltage self-regulation is as follows: a change in the load current causes a change in the magnetomotive force (MMF) of the additional or control winding connected in series with the main winding.

A change in the MMF will entail a change in the flux, which is adequate to a change in the EMF of the additional winding. With an increase in load, its EMF increases, with a decrease, it decreases. When the windings are connected in series, the EMF of the main and additional windings are added, that is, there is an increase output voltage. In the case of a decrease in load, the EMF of the additional winding decreases, which will lead to a decrease in the output voltage.

Common with RF patent Ns 2422935 is the possibility of changing the voltage by a given transformation ratio of additional windings.

The difference from the claimed patent lies in the elimination of the dependence of the design of the control transformer on the nature of the load, in the complete rejection of a separate control transformer, as well as from the devices for connecting the main and control transformer.

The presence of additional windings in each phase of the transformer is an essential feature because it determines the technical result, which consists in identifying a new function that the transformer can perform - the possibility of independent self-regulation of secondary voltages when the load changes without any external intervention. Such a function is adequate to the function of a voltage stabilizer. The transformers claimed by the patent are produced in a dry version, that is, they do not need a forced cooling system (tank, oil, radiators, pumps, pipelines, etc.), due, firstly, to the good thermal conductivity of steel and heat removal by a hexagonal yoke and, secondly, due to the elimination by the transformer itself of the “voltage imbalance”, and, consequently, the overload of the windings with currents.

The obtained technical and economic indicators indicate the creation of a transformer with improved production technology, improved weight and size characteristics compared to the prototype, which combines the functions of a transformer with the functions of a higher harmonic filter, balancing device and voltage stabilizer. The principle of operation of the transformer is known from literary sources, for example, Ivanov-Smolensky A.V. Electrical machines, in 2 volumes Textbook for universities. - M Ed. MPEI. - 2004.

Claims

Formula

1. A three-phase transformer contains in its composition the main primary and secondary windings, a spatial magnetic system composed of plates of electrical steel, characterized in that the magnetic system is formed by six regular trihedral prisms connected to each other by a common edge, thus forming a hexagonal prism with a six-beam star in section, adjacent faces of the star are cores of the magnetic circuit, and autonomous ones are a hexagonal yoke, the vertical density of the plates of the magnetic circuit is provided by central and lateral fastening, the main windings are divided in half and additional windings are placed in phase on the rods with a spatial angle of 60 °, the magnetic system is made with the ratio of the width of the rod and the yoke equal to two and the height of the prism to the width of the beam greater than five.

2. Three-phase transformer according to claim 1, characterized in that the main and additional windings are placed together on rods with a spatial angle of 120 °.

3. Three-phase transformer according to claim 1, characterized in that the spatial magnetic circuit is made of amorphous electrical steel with a thickness of 10 to 30 microns.