CN112992491A

CN112992491A - Single-phase transformer

Info

Publication number: CN112992491A
Application number: CN201911272627.1A
Authority: CN
Inventors: 李龙波
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-12-12
Filing date: 2019-12-12
Publication date: 2021-06-18

Abstract

The invention provides a single-phase transformer which comprises a single-phase multi-column iron core, wherein the single-phase multi-column iron core comprises two side columns and at least two core columns connected in parallel between the two side columns, two adjacent core columns are connected through two yoke parts to form a middle frame, the core columns and the side columns adjacent to the core columns are connected through the two yoke parts to form the side frame, the single-phase transformer further comprises at least one voltage stabilizing winding, the voltage stabilizing winding comprises a first coil and a second coil, the same-name ends of the first coil and the second coil are connected, the first coil is wound on any one yoke part or the side column of the side frame, and the second coil is wound on any one yoke part of the middle frame adjacent to the side frame. The invention can make the magnetic fluxes in the side frame and the middle frame of the iron core the same, reduce higher harmonics and prevent the iron core from local overheating.

Description

Single-phase transformer

Technical Field

The invention relates to the technical field of transformers, in particular to a single-phase transformer.

Background

Some large special transformers such as ultrahigh-voltage and large-capacity single-phase power transformers, three-phase power transformer sets and converter transformers are limited by transportation size, and a transformer core usually adopts a single-phase multi-column parallel core. Fig. 1 and 2 are two different structures of a transformer including a single-phase four-limb core, respectively, and the transformers of fig. 1 and 2 are formed into a plurality of frame-shaped structures connected in parallel, including two side frames and a middle frame between the two side frames. In the transformer of both the configurations of fig. 1 and 2, the excitation magnetomotive force in the side frame circuit L1 is NI, and the excitation magnetomotive force in the middle frame circuit L2 is 2NI, where N is the number of turns of the primary winding 31 and I is the current flowing through the primary winding 31, according to ampere-loop law. And because of the magnetic resistance in the side frame loop L1 and the middle frame loop L2Close to each other, therefore, from magnetic path ohm's law Φ to F_m/R_mIt is understood that the magnetic flux flowing through the center loop L2 is much larger than the magnetic flux flowing through the side loop L1, but the cross sections of the two loops are the same, so that the side loop L1 is under-excited and the center loop L2 is over-excited.

The iron core silicon steel sheet used for the power transformer has nonlinear magnetization characteristics, and for such a nonlinear magnetic circuit system with a zero-sequence magnetic flux free path, a large amount of additional zero-sequence harmonic magnetic flux is generated in a magnetic circuit. Taking the frame structure as an example, as shown in fig. 3, a waveform v1 represents a flux induced voltage waveform of a side frame, and a waveform v2 represents a flux induced voltage waveform of a middle frame, and it can be found from the data of fig. 3 that: the middle frame fundamental wave magnetic flux is 1.88 times of the side frame fundamental wave magnetic flux, the third harmonic content reaches 31.4 percent, and the middle frame is easy to be locally overheated.

Disclosure of Invention

The invention aims to provide a single-phase transformer, which enables the magnetic flux distribution in each frame in a transformer core to be more uniform and reduces the over-magnetization phenomenon of a middle frame magnetic circuit.

In order to achieve the above object, the present invention provides a single-phase transformer, which includes a single-phase multi-limb core, the single-phase multi-limb core includes two side limbs and at least two limbs connected in parallel between the two side limbs, two adjacent limbs are connected by two yoke portions to form a middle frame, the limbs and the adjacent limbs are connected by two yoke portions to form a side frame, the single-phase transformer further includes at least one voltage stabilizing winding, the voltage stabilizing winding includes a first coil and a second coil, the same-name ends of the first coil and the second coil are connected, the first coil is wound on any one of the yoke portions or the side limbs of the side frame, and the second coil is wound on any one of the yoke portions of the middle frame adjacent to the side frame.

Preferably, the single-phase multi-limb iron core comprises two limb cores, and the single-phase transformer comprises one voltage stabilizing winding; in the sideframe, one of the yoke portions is connected between the top end of the stem and the top end of the sidepost, and the other yoke portion is connected between the bottom end of the stem and the bottom end of the sidepost; in the middle frame, one yoke part is connected between the top ends of the two mandrels, the other yoke part is connected between the bottom ends of the two mandrels, and the first coil and the second coil are wound on the yoke part connected with the top ends of the mandrels.

Preferably, the single-phase multi-limb iron core comprises three core limbs, and the single-phase multi-limb transformer comprises two voltage stabilizing windings; two first coils in the two voltage stabilizing windings are arranged on different side frames, and two second coils in the two voltage stabilizing windings are arranged on different middle frames.

Preferably, the number of turns of the first coil and the second coil is the same.

Preferably, the wire of the first coil and the wire of the second coil have equal cross-sectional areas.

Preferably, each of the stems is provided with an oil passage to divide the stem into two parts.

Preferably, the cross-sectional area of each of the legs is equal, the cross-sectional areas of the two side legs are equal, and the cross-sectional area of the side leg is 0.5 times the cross-sectional area of the leg.

Preferably, the core leg adjacent to one of the side legs is wound with a primary winding, and the core leg adjacent to the other side leg is wound with a secondary winding.

Preferably, the single-phase multi-column core is a laminated core.

In the invention, the single-phase multi-column iron core is provided with the voltage stabilizing winding, the voltage stabilizing winding comprises the first coil and the second coil which are connected in parallel, and the induced voltages on the first coil and the second coil are the same, so that the balance effect on the magnetic flux of the side frame and the magnetic flux of the middle frame can be realized, and the over-excitation and under-excitation of the middle frame can be prevented. And through the arrangement of the voltage stabilizing winding, higher harmonics in the side frame and the middle frame are reduced, so that the condition that the iron core is locally overheated due to the higher harmonics is reduced, and no-load loss and no-load current are reduced.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

fig. 1 is a first structural diagram of a transformer using a single-phase four-limb core in the prior art;

fig. 2 is a schematic diagram of a second structure of a transformer using a single-phase four-limb core in the prior art;

FIG. 3 is a waveform diagram of the induced voltages at the middle and side frames of the transformer shown in FIG. 2;

fig. 4 is a first structural schematic diagram of a single-phase multi-limb core provided with a voltage stabilizing winding according to the present invention;

fig. 5 is a schematic diagram of a second structure of a single-phase multi-limb core provided with a voltage stabilizing winding according to the present invention;

fig. 6 is a third structural schematic diagram of a single-phase multi-limb iron core provided with a voltage stabilizing winding according to the invention;

fig. 7 is a fourth structural schematic diagram of a single-phase multi-limb core provided with a voltage stabilizing winding according to the invention.

Wherein the reference numerals are:

11. a side column; 12. a stem; 13. a yoke portion; 14. an oil passage; 20. a voltage stabilizing winding; 21. a first coil; 22. a second coil; 31. a primary winding.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The invention provides a single-phase transformer, as shown in fig. 4 to 7, comprising a single-phase multi-limb iron core, wherein the single-phase multi-limb iron core comprises two side limbs 11, at least two core limbs 12 are connected between the two side limbs 11 in parallel, two adjacent core limbs 12 are connected through two yoke parts 13 to form a middle frame, and the core limbs 12 and the side limbs 11 adjacent to the core limbs are connected through the two yoke parts 13 to form the side frame. And the single-phase transformer also comprises at least one voltage stabilizing winding 20, the voltage stabilizing winding 20 comprises a first coil 21 and a second coil 22, the same-name ends of the first coil 21 and the second coil 22 are connected, the first coil 21 is wound on any one yoke part of the side frame or the side column 11, and the second coil 22 is wound on any one yoke part 13 of the middle frame adjacent to the side frame.

Under the condition that a voltage stabilizing winding is not arranged in the prior art, the magnetomotive force generated in the middle frame is 2 times of the magnetomotive force generated in the side frame, so that the flowing magnetic flux is much larger than that flowing through the side frame, the middle frame is over-excited, and the middle frame contains more third harmonic waves, so that the iron core is locally overheated. In the present invention, since the core is provided with the voltage stabilizing winding 20, and the first coil 21 and the second coil 22 in the voltage stabilizing winding 20 are connected in parallel, the induced voltages of the first coil 21 and the second coil 22 are equal, that is, when the excitation voltage is U, the voltage across the first coil 21 is U1, and the voltage across the second coil 22 is U2, U1+ U2, and U1 is U2 is U/2. And the voltage is equal to the derivative of the magnetic flux with respect to time, so that the magnetic flux phi 1 flowing through the side frame and the magnetic flux phi 2 flowing through the middle frame are also equal under the limit that the voltages on the two coils are equal, thereby preventing the middle frame from being over-excited and the side frame from being under-excited.

In addition, in the case where the voltage stabilizing winding is not provided, although the excitation voltage U does not include a harmonic, since the single-phase transformer itself is a nonlinear device, one of the induced voltage of the side frame and the induced voltage of the middle frame generates a harmonic in the positive direction, and the other generates a harmonic in the negative direction so that the sum of the two is equal to the excitation voltage including no harmonic. In the invention, due to the arrangement of the voltage stabilizing winding, the voltage U1 at the two ends of the first coil 21 is equal to the voltage U2 at the two ends of the second coil 22, and the excitation voltage U does not contain higher harmonics, so that the induced voltages of the side frame and the middle frame do not contain plus-minus higher harmonics, thereby reducing the local overheating condition of the iron core caused by the higher harmonics and simultaneously reducing no-load loss and no-load current. In the single-phase transformer, a primary winding is wound on a core 12 adjacent to one of the side legs 11, and a secondary winding is wound on a core 12 adjacent to the other side leg 11. After voltage is loaded at two ends of the primary winding, magnetic fluxes flow through the side frame and the middle frame to form a magnetic flux loop.

Specifically, in the side frame in which one yoke 13 is connected between the top ends of the stems 12 and the top ends of the side stems 11, and the other yoke 13 is connected between the bottom ends of the stems 12 and the side stems 11, one yoke 13 is connected between the top ends of the two stems 12, and the other yoke 13 is connected between the bottom ends of the two stems 12. Preferably, as shown in fig. 4 to 7, the first coil 21 is wound around the yoke portion 13 connected to the top end of the stem 12; the second coil 22 is wound around the yoke portion 13 connected to the top end of the stem 12. To facilitate the mounting of the first coil 21 and the second coil 22.

The voltage stabilizing winding can be arranged on both the single-phase four-column iron core and the single-phase five-column iron core. As an embodiment of the present invention, as shown in fig. 4 and 5, the single-phase multi-limb core includes two side limbs 11 and two limbs 12 between the two side limbs 11, and in this case, the single-phase transformer includes one stabilizing winding 20. Meanwhile, in order to facilitate the arrangement of the voltage stabilizing winding 20, the first coil 21 in the voltage stabilizing winding 20 can be positioned on the yoke part 13 which is connected with the top end of the stem 12 in the left side frame, and also can be positioned on the yoke part 13 which is connected with the top end of the stem 12 in the right side frame; the second coil 22 may be located at the yoke portion 13 of the center frame that is attached to the top end of the stem 12.

When the magnetic flux flowing through the left side frame is phi 1, the magnetic flux flowing through the middle frame is phi 2, and the magnetic flux flowing through the right side frame is phi 3, phi 1+ phi 2 is phi 2+ phi 3; since the voltage U1 across the first coil 21 is equal to the voltage across the second coil 22, the magnetic flux Φ 1 flowing in the left side frame, the magnetic flux Φ 2 flowing in the middle frame, and the magnetic flux Φ 3 flowing in the right side frame are equal.

As another embodiment of the present invention, the single-phase multi-limb core is a single-phase five-limb core, as shown in fig. 6 and 7, the single-phase multi-limb core includes two side limbs 11 and three limbs 12 located between the two side limbs 11, the single-phase multi-limb transformer includes two voltage stabilizing windings 20, two first coils 21 of the two voltage stabilizing windings 20 are disposed on different side frames, and two second coils 22 of the two voltage stabilizing windings 20 are disposed on different middle frames.

In the single-phase five-limb core, only one voltage stabilizing winding 20 may be provided, for example, the first coil 21 of the voltage stabilizing winding 20 may be wound around the side limb 11 or the yoke portion 13 of the left side frame, and the second coil 22 may be wound around the yoke portion 13 of the middle frame adjacent to the left side frame.

When the magnetic flux flowing through the left side frame is phi 1, the magnetic flux flowing through the left side middle frame is phi 2, the magnetic flux flowing through the right side middle frame is phi 3, and the magnetic flux flowing through the right side frame is phi 4, phi 1+ phi 2 is phi 2+ phi 3 is phi 3+ phi 4; in the case where one stabilizing winding 20 is provided and two stabilizing windings 20 are provided, the magnetic flux Φ 1 flowing through the left side frame, the magnetic flux Φ 2 flowing through the left side frame, the magnetic flux Φ 3 flowing through the right side frame, and the magnetic flux Φ 4 flowing through the right side frame can be made equal.

Specifically, the number of turns of the first coil 21 and the second coil 22 is the same, and the cross-sectional area of the wire of the first coil 21 and the second coil 22 is the same, so when the two are connected in parallel, the current flowing through the first coil 21 and the second coil 22 is the same, and the magnetomotive force generated by the first coil 21 and the second coil 22 is also the same.

In practice, the number of turns of the first coil 21 and the second coil 22 and the cross-sectional area of the wire may be determined according to the magnetomotive force required. Also, for the single-phase five-limb core, when two stabilizing windings 20 are provided, the current flowing through each coil is small, and at this time, the cross section of the wire of the first coil 21 and the second coil 22 may be set small; when one stabilizing winding 20 is provided, the current flowing through each coil is large, and at this time, the cross-sectional area of the wires of the first coil 21 and the second coil 22 can be set large.

The present invention is not particularly limited in its construction to the stem 12, and as shown in fig. 4 and 6, the stem 12 may be of unitary construction; alternatively, as shown in fig. 5 and 7, each stem is provided with an oil passage 14, the oil passage 14 dividing the stem 12 into two parts.

Further, the cross-sectional area of each of the legs 12 is equal, the cross-sectional areas of the two side legs 11 are also equal, and the cross-sectional area of the side leg 11 is 0.5 times the cross-sectional area of the leg 12. When the stem 12 is divided into two parts, the left half of the stem forms a magnetic circuit with the side stem/half of the stem and two yoke parts on the left side thereof, and the right half of the stem forms a magnetic circuit with the side stem/half of the stem and two yoke parts on the right side thereof. Because an air gap is arranged between the left half stem and the right half stem, the magnetic fluxes in the left half stem and the right half stem cannot intersect, and when the cross section area of the side stem 11 is 0.5 times of that of the stem 12, the magnetic density of the side stem can be ensured to be the same as that of the stem.

In the implementation process, a primary winding and a secondary winding are respectively wound on two core posts, a first coil and a second coil are wound on corresponding yoke parts, and then the yoke parts, the side posts and the core posts are installed.

The single-phase transformer provided by the invention comprises the voltage stabilizing winding arranged on the iron core, wherein the voltage stabilizing winding comprises the first coil and the second coil which are connected in parallel, and the induced voltages on the first coil and the second coil are the same, so that the balance effect on the magnetic flux of the side frame and the magnetic flux of the middle frame can be realized, and the over-excitation and under-excitation of the side frame can be prevented. And through the arrangement of the voltage stabilizing winding, higher harmonics in the side frame and the middle frame are reduced, so that the condition that the iron core is locally overheated due to the higher harmonics is reduced, and no-load loss and no-load current are reduced.

It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.

Claims

1. A single-phase transformer comprising a single-phase multi-limb core comprising two side limbs and at least two limbs connected in parallel between the two side limbs, two adjacent limbs being connected by two yoke portions to form a central frame, the limbs and their adjacent limbs being connected by two yoke portions to form a side frame,

the single-phase transformer further comprises at least one voltage stabilizing winding, the voltage stabilizing winding comprises a first coil and a second coil, the first coil is connected with the same-name end of the second coil, the first coil is wound on any yoke part of the side frame or the side column, and the second coil is wound on any yoke part of the middle frame adjacent to the side frame.

2. The single-phase transformer of claim 1, wherein the single-phase multi-limb core comprises two of the limbs, the single-phase transformer comprising one of the regulated windings;

in the sideframe, one of the yoke portions is connected between the top end of the stem and the top end of the sidepost, and the other yoke portion is connected between the bottom end of the stem and the bottom end of the sidepost; in the middle frame, one yoke part is connected between the top ends of the two mandrels, the other yoke part is connected between the bottom ends of the two mandrels, and the first coil and the second coil are wound on the yoke part connected with the top ends of the mandrels.

3. The single-phase transformer of claim 1, wherein the single-phase multi-limb core comprises three of the limbs, the single-phase multi-limb transformer comprising two of the regulated windings; two first coils in the two voltage stabilizing windings are arranged on different side frames, and two second coils in the two voltage stabilizing windings are arranged on different middle frames.

4. The single-phase transformer of any one of claims 1 to 3, wherein the first coil and the second coil have the same number of turns.

5. The single-phase transformer of claim 4, wherein the wires of the first coil and the second coil have equal cross-sectional areas.

6. The single-phase transformer according to any one of claims 1 to 3, wherein each of the limbs is provided with an oil passage to divide the limb into two parts.

7. The single-phase transformer of claim 6, wherein each of the legs has an equal cross-sectional area, and wherein the two side legs have an equal cross-sectional area, the side legs having a cross-sectional area that is 0.5 times the cross-sectional area of the legs.

8. The single-phase transformer according to any one of claims 1 to 3, wherein a primary winding is wound around a leg adjacent to one of the legs, and a secondary winding is wound around a leg adjacent to the other leg.

The single-phase transformer of any one of claims 1 to 3, wherein the single-phase multi-limb core is a laminated core.