CN219123087U - Single-phase core transformer of power transmission system - Google Patents

Abstract

The utility model provides a single-phase core transformer for a power transmission system. The transformer comprises an iron core, a main winding and an auxiliary winding. The iron core includes main stem, first side post and second side post. The main stem is located between the first and second side stems, and is spaced apart from the first and second side stems by a predetermined distance. The main winding is wound on the main stem, and the main winding has a circular cross section perpendicular to the axial direction of the main stem, the auxiliary winding is wound on the first leg, and the first leg has an elliptical cross section perpendicular to the axial direction of the first leg, and the auxiliary winding has an oblong cross section in the direction perpendicular to the axial direction of the first leg. The single-phase core type transformer adopts the auxiliary winding with the oblong section to be matched with the first side column with the oval section, so that the manufacturing cost and the material cost of the transformer can be obviously reduced.

Description

Single-phase core transformer of power transmission system

Technical Field

Embodiments disclosed herein relate to transformers, and more particularly, to a single-phase core transformer for a power transmission system.

Background

Power transmission (i.e., power transmission and transformation, generally abbreviated as "power transformation") is the movement of electrical energy in large quantities from a power station, such as a power plant, to a substation. Power transmission systems differ from local wiring between a substation and a customer, such as a residential building or supermarket, which is commonly referred to as power distribution (i.e., power distribution for general short). Efficient long-distance transmission of power requires a high transmission voltage, which can reduce losses due to large currents. Therefore, the power transmission system transmits power mainly at high voltage. The high voltage applied to the transmission system is changed by a transformer provided at a substation or a power plant, for example.

Transformers used in power transmission systems are widely known to those skilled in the art as "power transformers", typically high voltage or extra high voltage transformers, e.g. rated at 35kV or above, to reduce power losses. The power transformer is, for example, a hydraulic (e.g., oil-immersed) transformer rated at 380kV or 500kV (in contrast, the rated voltage level of the distribution transformer is typically 10kV or less). The high voltage transformer may include a case called a case, an iron core, and a coil (i.e., winding) wound around the iron core layer by layer.

The core of a transformer is typically a laminated core carrying magnetic flux coupled to the windings. The laminated core may be composed of a high permeability material, typically made of a thin silicon steel laminate. These thin laminations are assembled together to provide the desired magnetic circuit with minimal magnetic losses. The core typically includes two or more parallel limbs and a yoke connecting the limbs to form the magnetic circuit of the transformer. The core determines the shape of the transformer winding. Core (or core) transformers and shell (or shell) transformers are widely used in the field of power transmission. In a shell (shell-type) transformer, the primary and secondary windings pass inside a magnetic circuit that forms a housing over the windings that encases the windings. However, in the core transformer, the main winding and the auxiliary winding are wound on the core limb. The manufacturing cost of the core transformer is lower than that of the shell type transformer.

It is desirable to optimize single-phase core transformers for lower manufacturing costs and more compact size.

Disclosure of Invention

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of some embodiments. However, it will be understood by those of ordinary skill in the art that some embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, units and/or circuits have not been described in detail so as not to obscure the discussion.

References to "one embodiment," "an embodiment," "one or more embodiments," "various embodiments," etc., indicate that the embodiment(s) so described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Furthermore, repeated use of the phrase "in one embodiment" does not necessarily refer to the same embodiment, although it may.

As used herein, unless otherwise indicated, the use of ordinal adjectives "first," "second," "third," etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Some embodiments may be used in conjunction with various devices and systems, such as power grids and similar systems, etc.

Fig. 1 is a schematic plan view of an exemplary single-phase core transformer for use in a power transmission system. The single-phase core transformer comprises a main limb 12 and two limbs, a first limb 14 and a second limb 16, which are spaced apart in opposite/opposite directions relative to the main limb 12. The main winding 20 is wound around the main leg 12 and the auxiliary winding 30 may be wound around either of the first and second legs 14, 16 (in the exemplary transformer shown in fig. 1, the auxiliary winding 30 is wound around the first leg 14). As shown in fig. 1, the main limb 12 is cylindrical, i.e. has a circular cross-section, as is the main winding 20. In this way the shape of the main limb 12 and the main winding 20 is very adapted such that the first gap 18 between the main limb 12 and the main winding 20 filled with insulating material is narrow. Meanwhile, the first leg 14 and the second leg 16 have an elliptical cross-section as shown in fig. 1, which makes the elliptical cross-sectional areas of the first leg 14 and the second leg 16 half of the circular cross-sectional area of the main leg 12, so that when a power voltage (such as an AC voltage generated by an AC power source) is applied to the main winding 20, half of the magnetic flux generated by the main leg 12 and the main winding 20 is applied to the auxiliary winding 30 wound around the first leg 14 as shown in fig. 1. The elliptical cross-sectional area of the first leg 14 is half the circular cross-sectional area of the main leg 12 such that the first leg 14 with the auxiliary winding 30 receives half of the magnetic flux generated in the main leg 12 with the main winding 20. Unlike the auxiliary winding having an elliptical cross section, the auxiliary winding 30 has a circular cross section so as to fit the first leg 14 and reduce the length of the auxiliary winding 30.

However, the combination of the oval first leg 14 and the circular secondary winding 30 results in the formation of a second gap 19 of a larger size as shown in fig. 1. Also, as shown in fig. 1, the dimension of the second gap 19 in the short axis direction of the first side column 14 is much larger than the dimension of the second gap 19 in the long axis direction. Therefore, a large amount of insulating material is required to fill the second gap 19, particularly in the space along the short axis, which results in a significant increase in the size and cost of the transformer.

Based on the above-described transformer shown in fig. 1, one or more embodiments of the present disclosure disclose a single-phase core transformer having low cost and compact size configured for use in a power transmission system.

In accordance with one or more embodiments of the present disclosure, a single-phase core transformer for a power transmission system includes a core, a main winding, and an auxiliary winding. The iron core includes main stem, first side post and second side post. The main stem is located between the first and second side stems, and is spaced apart from the first and second side stems by a predetermined distance. The main winding is wound on the main stem, and the main winding has a circular cross section perpendicular to the axial direction of the main stem, the auxiliary winding is wound on the first leg, and the first leg has an elliptical cross section perpendicular to the axial direction of the first leg, and the auxiliary winding has an oblong cross section in the direction perpendicular to the axial direction of the first leg.

In accordance with one or more embodiments of the present disclosure, the oblong cross-section of the secondary winding includes: a rectangular portion having two first sides parallel to the minor axis of the first side column elliptical cross-section and two second sides parallel to the major axis of the first side column elliptical cross-section; the two semicircular end portions are joined to the rectangular portion at two first sides of the rectangular portion.

According to one or more embodiments of the present disclosure, the length L of the rectangular portion second side is:

L＝A+2Ca-2R，

wherein A is the length of the major axis of the elliptical cross section of the first side column, ca is the first distance between the outer edge of the first side column and the inner edge of the auxiliary winding along the major axis of the elliptical cross section of the first side column, and R is the radius of the semicircular end part; and a first distance Ca along the major axis of the elliptical cross-section of the first leg between the outer edge of the first leg and the inner edge of the auxiliary winding is equal to a second distance along the minor axis of the elliptical cross-section of the first leg between the outer edge of the first leg and the inner edge of the auxiliary winding.

According to one or more embodiments of the present disclosure, the length B of the minor axis of the first side column elliptical cross-section is:

wherein D is the diameter of the circular cross section of the main stem.

According to one or more embodiments of the present disclosure, a first distance between the main stem and the first side stem in a direction perpendicular to the main stem axis is greater than a second distance between the main stem and the second side stem in a direction perpendicular to the main stem axis; and a first distance between the outer edge of the first side post and the inner edge of the auxiliary winding along the major axis of the elliptical cross-section of the first side post is equal to a second distance between the outer edge of the first side post and the inner edge of the auxiliary winding along the minor axis of the elliptical cross-section of the first side post.

According to one or more embodiments of the present disclosure, a gap for filling an insulating material is provided between an outer edge of the first bypass pillar and an inner edge of the auxiliary winding, a first distance between the outer edge of the first bypass pillar and the inner edge of the auxiliary winding along a major axis of an elliptical cross section of the first bypass pillar is greater than or equal to a first predetermined threshold, and a second distance between the outer edge of the first bypass pillar and the inner edge of the auxiliary winding along a minor axis of the elliptical cross section of the first bypass pillar is greater than or equal to a second predetermined threshold, such that the first bypass pillar and the auxiliary winding are electrically insulated by the insulating material.

According to one or more embodiments of the present disclosure, the first distance along the major axis of the elliptical cross-section of the first leg between the outer edge of the first leg and the inner edge of the secondary winding is equal to the second distance between the outer edge of the first leg and the inner edge of the secondary winding.

According to one or more embodiments of the present disclosure, the auxiliary winding includes a voltage regulating winding section and an exciting winding section, the voltage regulating winding section is adjacent to the first leg, the exciting winding section is located outside the voltage regulating winding section, and both the voltage regulating winding section and the exciting winding section have an oblong cross section perpendicular to an axial direction of the first leg.

According to one or more embodiments of the present disclosure, the single-phase core transformer is a single-phase core transformer having a rated capacity of 500kV or more.

The combination of the first leg having an elliptical cross section and the auxiliary winding having an oblong cross section significantly narrows the gap formed between the outer edge of the first leg and the inner edge of the auxiliary winding, as compared to the transformer shown in fig. 1. In addition, the auxiliary winding having an oblong cross section makes it possible to shape the auxiliary winding using a bobbin (also referred to as a "shaping die") having an oblong cross section. Because the oblong bobbin is easier to mechanically adjust than the oval bobbin, one oblong coil bobbin can be adapted to manufacture a variety of auxiliary windings of different sizes that can be used with transformers having different rated capacities or other parameters, such as various current densities.

The single-phase core type transformer adopts an auxiliary winding with an oblong section to be matched with a first side column with an elliptical section. This helps to narrow the gap between the first leg and the auxiliary winding, particularly in the short axis direction of the elliptical cross section of the first leg. This can shorten the length or amount of wire (e.g., copper wire) required to form the auxiliary winding, and can also reduce the amount of insulating material required to fill the gap between the first leg and the auxiliary winding. Accordingly, one or more embodiments of the present disclosure can reduce the size of the auxiliary winding and reduce the amount of insulating material, thereby enabling significant reductions in manufacturing costs and material costs of the transformer.

Furthermore, an auxiliary winding having an oblong cross section requires that the bobbin used for shaping or otherwise winding the auxiliary winding (or precisely the coil turns) also have an oblong cross section. The dimensions of such oblong bobbins may be conveniently adjusted (e.g., by a mechanical tool) compared to bobbins having an elliptical cross-section for forming auxiliary windings having various dimensions. In this way, one oblong bobbin can be adapted to manufacture a plurality of differently sized auxiliary windings for transformers having various rated capacities or other operating parameters, such as various current densities, because it is much easier to mechanically adjust an oblong bobbin than to mechanically adjust an oblong bobbin. This is advantageous in particular in view of the high precision with which the precise shape of the bobbin needs to be maintained after the mechanical adjustment of the bobbin increases or decreases its size when winding to form secondary windings of different sizes. The manufacturing costs of providing a high voltage, ultra high voltage transformer (e.g., a single phase core transformer rated at 500kV or 1000 kV) with oblong auxiliary windings, particularly an automotive transformer, will be significantly reduced because the bobbin costs for shaping large auxiliary windings of high voltage and ultra high voltage transformers are very high (e.g., a bobbin for shaping auxiliary windings of high voltage or ultra high voltage transformers may require $ 10,000 to $ 100,000 for manufacturing in china), but an auxiliary winding with oblong cross section allows the size of the bobbin to be adjusted, so a bobbin of one size or specification size can be reused for shaping/winding multiple sizes of auxiliary windings for single phase core transformers for high voltage and ultra high voltage. So that the cost of manufacturing each transformer can be reduced.

Reference numerals illustrate:

10: an iron core;

12: a main stem;

20: a main winding;

14: a first side column;

16: a second side column;

18: a first gap;

19: a second gap;

30: an auxiliary winding;

31: a third gap;

32: a voltage regulating winding section;

33: a fourth gap;

34: exciting winding section;

l: the length of the second side of the rectangular part;

a: the length of the oval cross section along the major axis of the first side column;

ca: a first distance between the outer edge of the first leg and the inner edge of the voltage regulating winding section along the major axis of the elliptical cross section of the first leg;

cb: a second distance between the outer edge of the first side post and the inner edge of the voltage regulating winding section along the minor axis of the elliptical cross section of the first side post;

r: radius of the semicircular end portion;

w: maximum width of the innermost coil of the auxiliary winding;

b: the length of the minor axis of the elliptical cross section of the first side column;

d: the diameter of the circular section of the main stem; and

s, P, T: the main winding first, second and third winding segments.

Drawings

Fig. 1 is a schematic plan view of an exemplary single-phase core transformer configured for use in a power transmission system.

Fig. 2 is a schematic perspective view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure.

Fig. 3 is a schematic plan view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure.

Fig. 4 is a schematic cross-sectional view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure.

Fig. 5 is a schematic cross-sectional view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure.

Fig. 6 is a schematic cross-sectional view of a first leg and auxiliary winding combination of an exemplary single-phase core transformer in accordance with one or more embodiments of the present disclosure.

Detailed Description

Reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration embodiments in which embodiments may be practiced. Like reference numerals refer to like parts throughout the several views. The elements shown in the drawings and their reference numerals are listed below:

fig. 2 is a schematic perspective view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure. The single-phase core transformer includes an iron core, a main winding 20, and an auxiliary winding 30. The core has a main leg 12, a first leg 14 and a second leg 16. As shown in fig. 2, the first leg 14, the main leg 12 and the second leg 16 extend in the same direction and are spaced apart from each other with the main leg 1 between the first leg 14 and the second leg 16. The main winding 20 and the auxiliary winding 30 are wound on the main leg 12 and the first leg 14, respectively. The first leg 14 has an oval cross section perpendicular to the axial direction of the first leg 14, and the main winding 20 has an oblong cross section perpendicular to the axial direction of the first leg 14.

The auxiliary winding 30 having an oblong cross section cooperates with the first leg 14 having an oval cross section and narrows the gap between the first leg 14 and the auxiliary winding 30, in particular in the direction of the minor axis of the oval cross section of the first leg 14. This can reduce the size of the auxiliary winding 30. The reduced secondary winding 30 enables the overall size of the transformer to be reduced. Accordingly, since the length of the wire required for manufacturing the auxiliary winding 30 is shortened and the material required for filling the gap between the first leg 14 and the auxiliary winding 30 is also reduced, the material cost of the transformer can be significantly reduced. Furthermore, the auxiliary winding 30 having an oblong cross section makes it possible to adjust the size of the oblong bobbin used to shape the auxiliary winding 30, so that one oblong bobbin can be adapted to manufacture a plurality of auxiliary windings of different sizes for preparing transformers having various rated capacities or other performance parameters. This is because the oblong wire frame is easier to mechanically adjust than an oval wire frame (an oval wire frame is a clear choice for a person skilled in the art to adapt the first side post 14 with an oval cross section) and the adjusted dimensions are easier to control accurately. An oblong wire frame is particularly advantageous in view of the need to maintain the accuracy of the shape and dimensions of the wire frame after adjusting the wire frame to increase/decrease its dimensions. Therefore, the above-described transformer having the auxiliary winding 30 of an oblong cross section is low in manufacturing cost.

According to some embodiments, the above-described transformer may be used as a transformer for use in a power transmission system. The transformer may regulate a frequently or instantaneously fluctuating input voltage (such as an AC supply voltage generated at a power plant) to deliver a substantially constant target output voltage regardless of fluctuations in the input voltage.

Transformers used in power transmission systems generally require higher voltages than power distribution systems in order to reduce energy losses. For example, the transformer in some embodiments has a rated voltage of 220kV or more. The wire frame for shaping the auxiliary winding 30 of a high voltage or ultra high voltage transformer used in a power transmission system is expensive and high. The transformer having the auxiliary winding 30 of an oblong cross-section, which cooperates with the first leg 14 of an oval cross-section, enables the size of the bobbin for shaping the auxiliary winding 30 to be easily adjusted, the bobbin of the auxiliary winding 30 also having an oblong cross-section corresponding to the shape of the auxiliary winding 30. Thus, the size of one oblong bobbin can be adjusted to produce various auxiliary windings of different sizes for transformers of different rated capacities or other operating parameters.

Fig. 3 is a schematic plan view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments. Note that the upper yoke and the lower yoke are not shown in this figure. Fig. 4 is a schematic cross-sectional view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure. Fig. 5 is a schematic cross-sectional view of an exemplary single-phase core transformer configured for use in a power transmission system in accordance with one or more embodiments of the present disclosure. Note that only half of the main winding 20 and the auxiliary winding 30 are shown in fig. 4. The second side post 16 is not shown in fig. 4. The main stem 12 has a circular cross section perpendicular to its axial direction. Accordingly, the main winding 20 has a circular cross section perpendicular to the axial direction of the main limb 12. In some embodiments, the coils of the primary winding 20 and the secondary winding 30 are symmetrically distributed about the primary leg 12 and the first leg 14, respectively.

Referring now to fig. 3-5, in accordance with one or more embodiments, the main winding 20 includes a plurality of segments, e.g., two, three, five, or more segments, spaced apart from one another. For example, the main winding 20 includes first, second and third winding segments S, P and T, which are concentrically wound on the main limb 12 from the outside to the inside with respect to the main limb 12. The first, second and third winding segments S, P and T can be, for example, a series winding segment, a common winding segment and a tertiary winding segment, respectively, that are spaced apart from each other and insulated from each other. In other embodiments, the first, second and third winding segments S, P and T, i.e., the series winding segment, the common winding segment and the tertiary winding segment, may be arranged in a different order or position relative to the main stem 12 than shown in the figures. For example, the series winding segments may be disposed in a proximal position relative to the main limb 12, the common winding segment may be disposed in the middle, and the tertiary winding segment may be disposed on the outside relative to the main limb 12.

In one or more embodiments, the auxiliary winding 30 may include a voltage regulating winding section 32 and a field winding section 34. The voltage regulating winding section 32 and the field winding section 34 may be concentrically wound around the first leg 14. As shown in fig. 3 and 5, in one or more embodiments, the field winding section 34 may be disposed adjacent to the first leg 14 and the voltage regulating winding section 32 may be disposed outside of the field winding section 34. A third gap 31 may be formed between the field winding section 34 and the first leg 14 to electrically insulate the field winding section 34 from the first leg 14. I.e. the third gap 31 is located between the outer edge of the first leg 14 and the inner edge of the secondary winding 30, the third gap 3 may be filled with an insulating material. The larger the maximum voltage between the first leg 14 and the auxiliary winding 30, the larger the size of the gap, so that electrical insulation between the auxiliary winding 30 and the first leg is ensured. The voltage regulating winding section 32 may be disposed outside the field winding section 34, and a fourth gap 33 electrically insulating the voltage regulating winding section 32 and the field winding section 34 may be formed between the voltage regulating winding section 32 and the field winding section 34. This arrangement can simplify the insulation of the first leg 14. In other embodiments, the voltage regulating winding section 32 may be disposed adjacent the first leg 14, and the field winding section 34 may be disposed outside of the voltage regulating winding section 32. In addition, the auxiliary winding 30 may include more winding segments than the voltage regulating winding segment 32 and the field winding segment 34.

The main winding 20 and the auxiliary winding 30 may be connected together. For example, in accordance with one or more embodiments, the voltage regulating winding section 32 may be connected in series with the first and second winding sections S, P of the main winding 20. The field winding section 34 may be connected in parallel with the third winding section T. In this way, the voltage on the third winding T is applied to the field winding section 34, which induces a fixed magnetic flux in the first leg 14 as a field voltage and is coupled to the voltage regulating winding section 32. The voltage regulating winding section 32 in turn generates a tapped voltage that can increase or decrease the primary side voltage of the first and second winding sections S, P of the main winding 20, whether it increases or decreases depending on how the voltage regulating winding section 32 is connected to the first and second winding sections S, P.

The voltage regulating winding section 32 and the field winding section 34 each have an oblong cross-section perpendicular to the axial direction of the first leg 14. In this way, the voltage regulating winding section 32 and the field winding section 34 can be well matched to each other as shown in fig. 3. The field winding section 34 also cooperates with the first leg 14 having an oval cross-section as shown in fig. 3 and 4. A third gap 31 and a fourth gap 33 are formed between the outer edge of the first leg 14 and the inner edge of the field winding section 34 and between the outer edge of the field winding section 34 and the inner edge of the voltage regulating winding section 32, respectively. The third gap 31 and the fourth gap 33 are filled with an insulating material. Details regarding the insulating material will be discussed below.

In particular, the core of the transformer may be made of a low loss ferromagnetic amorphous metal. Laminated ferromagnetic silicon steel sheets may be used. The iron core includes an upper yoke, a lower yoke, and three legs connecting the upper and lower yokes, thereby forming a magnetic circuit. The three legs, i.e. the main leg 12, the first leg 14 and the second leg 16 as shown in fig. 3, are spaced apart from each other with the main leg 12 in the middle.

According to one or more embodiments as shown in fig. 3, the main stem 12 may be cylindrical, i.e. have a circular cross-section perpendicular to the axial direction of the main stem 12. The main winding 20 may have a circular cross-section that mates with the main limb 12. A relatively narrow first gap 18 is formed between the main winding 20 and the main limb 12. The size of the first gap 18 may be determined based on the maximum voltage between the first leg 14 and the main winding 20. The larger the maximum voltage between the first leg 14 and the main winding 20, the larger the size of the first gap.

In some embodiments, the voltage regulating winding section 32 may be connected in series with the first and second winding sections S, P, as shown in fig. 4, the first and second winding sections S, P may be a series winding section and a common winding section. The voltage regulating winding section 32 may have multiple taps and tap switches so that different taps may be selected to deliver different target output voltages. A primary side voltage may be output between the upper end of the first winding section S and the lower end of the second winding section P. For example, one output terminal of the first winding segment S (e.g., an upper end of the first winding segment S shown in a black dot at an upper side in fig. 4) and one output terminal of the second winding segment P (e.g., a lower end of the second winding segment P shown in a black dot at a lower side in fig. 4) may be connected to a load such as a power transmission line for applying a primary side voltage on the power transmission line. Similarly, the secondary side voltage may be delivered between a selected tap (not shown in fig. 4) of the voltage regulating winding section 32 and the terminal of the second winding section P. It should be noted that the output terminals of the first winding segment S and the second winding segment P shown in fig. 4 are merely exemplary. The first winding section S and the second winding section P may have an output terminal in the middle and an input terminal at the ends of the first winding section S and the second winding section P.

The number of coil turns included in the magnetic circuit at one of the plurality of taps may be different from the number of coil turns at the other tap. The turns ratio at the different taps is thus different so that different grading heads can deliver different output voltages. A tap switch (not shown) may be connected to the tap to open and close the tap.

Unlike the main stem 12 having a circular cross section, the first and second side stems 14, 16 have an elliptical cross section as shown in fig. 3. The minor axis length B of the elliptical cross-section of the first leg 14 is about half the diameter D of the circular cross-section of the main leg 12. In other words, the length B of the minor axis of the elliptical cross-section of the first leg 14 and the diameter D of the circular cross-section of the main leg 12 satisfy the following formula:

referring to fig. 2 and 3, this relationship between the minor axis length B of the elliptical cross-section of the first leg 14 and the diameter DD of the circular cross-section of the main leg 12 may be implemented by: the main stem (12) and the first side stem 14 are formed with the same number of silicon steel sheets (for example, laminated ferromagnetic silicon steel sheets) while making the first length of the portion of each silicon steel sheet at the position of the first side stem 14 half the second length of the portion at the position of the main stem 12. The first length and the second length of the silicon steel sheet refer to the dimensions of the silicon steel sheet along the minor axis of the elliptical cross section of the first side column 14.

The arrangement is such that the elliptical cross-sectional area of the first leg 14 is half the circular cross-sectional area of the main leg 12, such that when a mains voltage (such as AC mains) is applied to the main winding 20, the first leg 14 receives half of the magnetic flux generated by the main leg 12. Having the same number of silicon steel sheets for the main stem 12 and the first side stem 14 facilitates the stem to be connected piece by piece. Therefore, it is economical to manufacture the core having the main leg 12 and the first leg 14 of the above-mentioned relative sizes.

Similarly, the second leg 16 may also have the same number of silicon steel sheets as the main leg 12, and the length of the minor axis of the elliptical cross-section of the second leg 16 may also be equal to the length B of the minor axis of the elliptical cross-section of the first leg 14.

Since the elliptical cross-sectional area of the first leg 14, the second leg 16 is half the circular cross-sectional area of the main stem 12, the size and cost of the first leg 14, the second leg 16 can be reduced. The first side leg 14 and the second side leg 16 having smaller dimensions allow the transformer to have smaller dimensions. This is particularly advantageous in view of the fact that the price of silicon steel sheets has been increasing in recent years.

As shown in fig. 3, the second leg 16 has no windings disposed thereon in accordance with one or more embodiments of the present disclosure. That is, only a single auxiliary winding is arranged on the transformer for adjusting the output voltage of the transformer. The two auxiliary windings greatly increase the manufacturing cost of the transformer, complicate the voltage regulating operation of the transformer and increase the safety risk of the transformer. In contrast, a transformer with a single auxiliary winding can reduce the manufacturing cost of the transformer, simplify the adjustment of the transformer, and reduce the safety risk of the transformer.

The main stem 12 and the first leg 14 are spatially separated so that they are magnetically isolated from each other. The distance between the main leg 12 and the first leg 14 may be determined in consideration of the magnitude of the rated voltage of the transformer. Similarly, the second leg 16 is also spatially separated from the main stem 12. As shown in fig. 2 and 3, considering that no auxiliary winding is arranged on the second leg 16, the distance between the main leg 12 and the first leg 14 in the direction perpendicular to the axial direction of the main leg 12 is greater than the distance between the main leg 12 and the second leg 16 in the direction perpendicular to the axial direction of the main leg 12. I.e. the distance between the main leg 12 and the second leg 16 can be shorter to achieve magnetic insulation between the main leg 12 and the second leg 16. This may further reduce the size and cost of the transformer.

The single-phase core transformer described above may be used as a transformer for use in an electric power transmission system, since the short-circuit forces of this type of transformer may be better managed with a cylindrical main limb and main windings. Furthermore, unlike conventional transformers in which the primary and secondary voltage sides are magnetically coupled by a common core but are electrically isolated from each other, the voltage regulating winding section 32 of the transformer is herein connected in series with the main winding 20. In other words, the primary and secondary voltage sides of the transformer are both magnetically and electrically connected. As a result, the transformer adjusts an input voltage, such as a frequently fluctuating AC supply voltage generated at the power plant. Voltage regulation of the transformer ensures a stable output voltage, which is typically required for power transmission in high voltage power networks, for example. The delivered output voltage is no greater than or less than 10% of the rated output voltage of the transformer (which may be the ideal or theoretical voltage of the transformer that can be obtained based on faraday's law of electromagnetic induction).

The shape and size of the above-described transformer will now be described in detail. Fig. 6 is a schematic cross-sectional view of a first leg 14 and auxiliary winding 30 combination of an exemplary single-phase core transformer in accordance with one or more embodiments of the present disclosure. The oblong cross section of the auxiliary winding 30 comprises a rectangular portion and two semicircular end portions. The rectangular portion has a first side parallel to the minor axis of the elliptical cross-section of the first side column 14 and a second side parallel to the major axis of the elliptical cross-section of the first side column 14. The two semicircular end portions are joined to the rectangular portion at two first sides of the rectangular portion. In one or more embodiments shown in fig. 6, the first side of the rectangular portion is the long side of the rectangular portion shown in fig. 6 (i.e., two transverse imaginary line segments shown in fig. 6). I.e. two semicircular end portions are connected to the rectangular portion at two long sides of the rectangular portion. The second side of the rectangular portion is the short side of the rectangular portion shown in fig. 6. It will be appreciated that the positions at which the two semicircular end portions are connected to the rectangular portion may be two short sides of the rectangular portion, that is, the rectangular portion shown in fig. 6 may have a long lateral side or a long vertical side, depending on the number of turns of the coil included in the auxiliary winding 30, or the like. The length L of the second side of the rectangular portion, the length a of the major axis of the elliptical cross-section, the first distance Ca along the major axis between the outer edge of the first leg 14 and the inner edge of the secondary winding 30, and the radius R of the two semicircular end portions satisfy the following equation:

L＝A+2Ca-2R (2)

referring to fig. 6, the maximum width W of the innermost coil of the auxiliary winding 30, the length B of the minor axis of the elliptical cross-section of the first leg 14, and the second distance Cb along the minor axis formed between the outer edge of the first leg 14 and the inner edge of the auxiliary winding 30 satisfy the following formula:

W＝B+2Cb (3)

the first gap 18 between the main limb 12 and the main winding 20, the third gap 31 between the first limb 14 and the auxiliary winding 30, and the fourth gap 33 between the tuning winding 32 and the excitation winding when the auxiliary winding 30 is divided into the tuning winding 32 and the excitation winding section 34 may be filled with an insulating material to electrically insulate the main limb 12 from the main winding 20, the tuning winding 32 being electrically insulated from the excitation winding section 34. The insulating material may be an insulating polymer layer, such as insulating polymer paper (e.g., nomex paper with a thickness of 0.05 mm) or an insulating polymer sheet.

Referring to fig. 6, a first distance Ca along the major axis of the elliptical cross-section of the first leg 14, i.e., an insulation distance, between the outer edge of the first leg 14 and the inner edge of the auxiliary winding 30 may be greater than or equal to a predetermined threshold. A second distance Cb along the minor axis of the elliptical cross-section of the first leg 14 between the outer edge of the first leg 14 and the inner edge of the voltage regulating winding section 32 may be greater than or equal to a second predetermined threshold such that the first leg 14 and the auxiliary winding 30, as well as the voltage regulating winding section 32 and the field winding section 34, are electrically insulated by an insulating material. The first and second predetermined thresholds may be determined based on maximum operating voltages between the first leg 14 and the auxiliary winding 30 along the major and minor axes, respectively, to ensure reliability and safety performance of the transformer.

According to one or more embodiments, the first distance Ca is equal to the second distance Cb. Such an arrangement provides a minimum size of the auxiliary winding 30, including both the maximum width W of the innermost coil of the auxiliary winding and the length L of the second side of the rectangular portion. Therefore, the cost of the transformer can be further reduced. For example, for a transformer having the configuration shown in fig. 4 and an excitation winding section 34 having a rated voltage of 35kV (i.e., since the excitation winding section 34 is connected in parallel with the third winding section T, the rated voltage of the third winding section T is 35 kV). The first distance Ca and the second distance Cb may be 22mm. In addition, such a configuration also facilitates calculation of the impedance and leakage flux of the transformer, which are performance parameters often required by a user of the transformer. In some embodiments, the transformer is a single-phase core transformer for a power transmission system. Such a transformer may have a rated voltage of 220kV or more.

The cost of production and manufacturing of unidirectional core transformers disclosed with one or more embodiments of the present utility model will be greatly reduced, considering that the bobbin for forming the auxiliary winding of the unidirectional core transformer is expensive, but the auxiliary winding of oblong cross section in the present utility model allows the bobbin for forming the auxiliary winding to be adjustable for forming auxiliary windings of different sizes, which enables transformers of different rated voltages and capacities to be manufactured at lower cost. The transformer may be a single-phase core transformer having a rated voltage of 500kV or more. The market demand for such transformers is not great, whereas the bobbins used to shape the secondary windings of such transformers are expensive due to the large size of the bobbins. The manufacturing cost of the single-phase core type transformer with the rated voltage of 500kV or more can be remarkably reduced by adopting the transformer. Further, since the third gap between the auxiliary winding and the first leg is narrowed, less insulating material is required between the auxiliary winding and the first leg, and the third gap 31 is narrowed so that the overall length of the wire for forming the auxiliary winding 30 is also reduced. This can further reduce the manufacturing cost of the single-phase core transformer.

The foregoing description of the preferred embodiments of the present application is not intended to limit the same, but to provide for the purpose of illustration, description, and illustration, of any modifications, equivalents, improvements, etc. that fall within the spirit and principles of the present application. .

While specific embodiments are described above, it will be understood that it is not intended to limit the application to these specific embodiments. On the contrary, the present application includes alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims. Numerous specific details are set forth in order to provide a thorough understanding of the subject matter presented herein. It will be apparent, however, to one skilled in the art that the subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

Claims (9)

1. Single-phase core transformer for an electric power transmission system, characterized by comprising an iron core (10), a main winding (20) and an auxiliary winding (30), the iron core (10) comprising a main limb (12), a first limb (14) and a second limb (16), the main limb (12) being located between the first limb (14) and the second limb (16), the main limb (12) being spaced apart from the first limb (14) and from the main limb (12) to the second limb (16) by a predetermined distance, the main winding (20) being wound on the main limb (12) and the main winding (20) having a circular cross section perpendicular to the axial direction of the main limb (12), the auxiliary winding (30) being wound on the first limb (14) and the first limb (14) having an oval cross section perpendicular to the axial direction of the first limb (14), the auxiliary winding (30) having an oblong cross section perpendicular to the axial direction of the first limb (14).

2. Single-phase core transformer for an electric power transmission system according to claim 1, characterized in that the oblong cross section of the auxiliary winding (30) comprises: a rectangular portion having two first sides parallel to the minor axis of the elliptical cross-section of the first side post (14) and two second sides parallel to the major axis of the elliptical cross-section of the first side post (14), and two semicircular ends joined to the rectangular portion at the two first sides of the rectangular portion.

3. The single-phase core transformer for an electric power transmission system according to claim 2, wherein the length L of the rectangular portion second side is:

L＝A+2Ca-2R，

wherein A is the length of the major axis of the elliptical cross section of the first side column (14), ca is the first distance between the outer edge of the first side column (14) and the inner edge of the auxiliary winding (30) along the major axis of the elliptical cross section of the first side column (14), and R is the radius of the semicircular end part; and, a first distance Ca along a major axis of the elliptical cross section of the first leg (14) between an outer edge of the first leg (14) and an inner edge of the auxiliary winding (30) is equal to a second distance along a minor axis of the elliptical cross section of the first leg (14) between an outer edge of the first leg (14) and an inner edge of the auxiliary winding (30).

4. Single-phase core transformer for electric power transmission systems according to claim 1, characterized in that the length B of the minor axis of the elliptical section of the first leg (14) is:

wherein D is the diameter of the circular cross-section of the main stem (12).

5. Single-phase core transformer for an electric power transmission system according to claim 1, characterized in that a first distance between the main limb (12) and a first side limb (14) in a direction perpendicular to the main limb (12) axis is greater than a second distance between the main limb (12) and a second side limb (16) in a direction perpendicular to the main limb (12) axis; and, a first distance Ca along a major axis of the elliptical cross section of the first leg (14) between an outer edge of the first leg (14) and an inner edge of the auxiliary winding (30) is equal to a second distance along a minor axis of the elliptical cross section of the first leg (14) between an outer edge of the first leg (14) and an inner edge of the auxiliary winding (30).

6. Single-phase core transformer for an electric power transmission system according to claim 1, characterized in that a gap for filling insulating material is provided between the outer edge of the first leg (14) and the inner edge of the auxiliary winding (30), a first distance between the outer edge of the first leg (14) and the inner edge of the auxiliary winding (30) along the major axis of the elliptical cross section of the first leg (14) being greater than or equal to a first predetermined threshold value, and a second distance between the outer edge of the first leg (14) and the inner edge of the auxiliary winding (30) along the minor axis of the elliptical cross section of the first leg (14) being greater than or equal to a second predetermined threshold value, such that the first leg (14) and the auxiliary winding (30) are electrically insulated by the insulating material.

7. The single-phase core transformer for an electric power transmission system according to claim 6, characterized in that a first distance along a major axis of an elliptical cross-section of the first side leg (14) between an outer edge of the first side leg (14) and an inner edge of the auxiliary winding (30) is equal to a second distance between an outer edge of the first side leg (14) and an inner edge of the auxiliary winding (30).

8. The single-phase core transformer for an electric power transmission system according to any one of claims 1-7, characterized in that the auxiliary winding (30) comprises a voltage regulating winding section (32) and an excitation winding section (34), the voltage regulating winding section (32) being adjacent to the first side leg (14), and the excitation winding section (34) being located outside the voltage regulating winding section (32), and that both the voltage regulating winding section (32) and the excitation winding section (34) have an oblong cross section perpendicular to the axial direction of the first side leg (14).

9. The single-phase core transformer for an electric power transmission system according to any one of claims 1 to 7, wherein the single-phase core transformer is a single-phase core transformer having a rated capacity of 500kV or more.

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