JP2020043155A - Transformer - Google Patents

Abstract

To provide a transformer capable of reducing loss in a shield while suppressing manufacturing cost.SOLUTION: A transformer (1) includes: an iron core (10); a winding (20) wound around the iron core; a tank (30) for storing the iron core and the winding; and a shield (40) mounted along an internal surface of the tank and shielding a magnetic flux going toward the tank side. The shield is constituted by laminating high resistance silicon steel sheet (41) and low resistance silicon steel sheet (42) as a plurality of silicon steel sheets with relatively different specific resistance from each other. Use of high resistance silicon steel sheet reduces a current value of an eddy current to reduce loss at the shield and suppress the amount used of the high resistance silicon steel sheet circulated at a high cost, thereby achieving suppression of manufacturing cost.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transformer, and more particularly to a transformer that can shield a leakage magnetic flux generated from a winding from entering a tank or the like with a shield.

  A transformer is a device that converts the voltage of AC power using electromagnetic induction, and includes a core that constitutes a magnetic circuit and windings that constitute an electric circuit, which are housed in a tank. During operation of the transformer, magnetic flux leaks from the windings into the tank. An eddy current is generated on the tank wall where the leakage magnetic flux links, and eddy current loss such as local overheating on the tank wall occurs. In order to avoid or suppress the occurrence of eddy current loss in such a tank wall, as disclosed in Patent Document 1, a magnetic steel sheet having a predetermined thickness laminated between an inner surface of a tank wall and a winding is used. A shield is provided to induce magnetic flux leakage to the magnetic shield.

JP-A-6-69050

  In Patent Literature 1, although the amount of leakage magnetic flux incident on the tank wall is suppressed by the magnetic shield, the leakage magnetic flux also enters the magnetic shield, causing eddy current loss. In particular, the leakage flux is large in large capacity transformers and high impedance transformers, and when the distance between the winding and the tank wall is reduced, the leakage flux applied to the magnetic shield increases. A large eddy current is generated and the loss increases. Here, the present inventor studied to reduce the eddy current and suppress the eddy current loss by increasing the specific resistance of the entire magnetic shield, but in this case, the material cost is increased and the manufacturing cost is reduced. There is a problem of rising. Therefore, the present inventor has invented a configuration capable of suppressing an increase in manufacturing cost and reducing eddy current loss due to magnetic flux leakage in the shield.

  SUMMARY An advantage of some aspects of the invention is to provide a transformer that can reduce a loss in a shield while suppressing manufacturing costs.

  The transformer according to an aspect of the present invention includes an iron core, a winding wound around the iron core, a tank that houses the iron core and the winding, and a tank provided along an inner surface of the tank. And a shield for shielding magnetic flux toward the side, wherein the shield is formed by laminating a high-resistance silicon steel sheet and a low-resistance silicon steel sheet having relatively different specific resistances. .

  According to the present invention, since the shield is formed by laminating two types of silicon steel sheets, that is, a high-resistance silicon steel sheet and a low-resistance silicon steel sheet, the specific resistance of the entire shield can be reduced. Thereby, even if an eddy current is generated in the shield due to the application of the leakage magnetic flux, the current value can be reduced and the loss in the shield can be reduced. In addition, by using two types of silicon steel plates for the shield, the amount of high-resistance silicon steel plates that are distributed at a high price can be suppressed, and an increase in material costs can be suppressed.

It is a longitudinal section showing the schematic structure of the transformer concerning this embodiment. It is a perspective view which shows the shield of this Embodiment typically. It is a graph which shows the measurement result of an example and a comparative example.

  Hereinafter, a transformer according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following, a case where the present invention is applied to an oil-immersed transformer will be described. However, the application object of the present invention is not limited to the oil-immersed transformer, and can be appropriately changed. For example, it can be applied to a gas-insulated transformer.

  FIG. 1 is a longitudinal sectional view showing a schematic configuration of the transformer according to the present embodiment. As shown in FIGS. 1 and 2, the transformer 1 includes an iron core 10 that forms a magnetic circuit, a winding 20 that forms an electric circuit, and a tank 30 that houses the iron core 10 and the winding 20. It is configured.

  The iron core 10 can be exemplified by a configuration in which electromagnetic steel sheets are laminated and joined. The iron core 10 includes a plurality of legs 11 (only one is shown in FIG. 1), an upper yoke portion 12 joined to upper and lower positions of the legs 11, and a lower portion. And a yoke portion 13.

  The windings 20 are respectively wound around the legs 11 and arranged. The winding 20 has an outer winding 21 and an inner winding 22 arranged concentrically. The outer winding 21 and the inner winding 22 are formed by coating a conductor such as copper or aluminum with an insulator, and then winding a plurality of loops in a coil shape. Here, the axial direction of the winding 20 is a direction in which the central axis position of the cylindrical winding 20 extends, and is the vertical direction in FIG.

  The tank 30 includes a top wall 31 and a bottom wall 32 located above and below the iron core 10 and the winding 20, and a plurality of side walls 33 extending vertically between outer peripheries of the top wall 31 and the bottom wall 32. It is formed in the shape of a box made of metal such as iron. The transformer 1 of the present embodiment is an oil-filled transformer in which the tank 30 is filled with an insulating oil (not shown), and the core 10 and the windings 20 are impregnated with the insulating oil in the tank 30. I have.

  In the transformer 1, leakage magnetic flux is generated from the winding 20 during operation and flows in a direction in which the leakage magnetic flux enters the tank 30. Eddy current loss generated in the tank 30 due to the incidence of the leakage magnetic flux is reduced. It must be avoided or suppressed. Therefore, the transformer 1 is configured to include the shield 40 between the side wall 33 of the tank 30 and the winding 20. The shield 40 is arranged along the inner surface of the side wall 33. The shield 40 is also impregnated with insulating oil in the tank 30.

  In the transformer, the shield 40 guides the leakage magnetic flux generated from the winding 20 to the shield 40 itself to shield the leakage magnetic flux toward the tank 30. Therefore, a leakage magnetic flux is also applied to the shield 40, and there is a demand for avoiding or suppressing an eddy current loss generated in the shield 40 due to the leakage magnetic flux. Therefore, in the present embodiment, the shield 40 has a configuration as shown in FIG. Hereinafter, the configuration of the shield 40 will be described.

  FIG. 2 is a perspective view schematically illustrating the shield according to the present embodiment. As shown in FIG. 2, the shield 40 is configured by stacking a high-resistance silicon steel sheet 41 and a low-resistance silicon steel sheet 42 having relatively different specific resistances. In other words, the high-resistance silicon steel sheet 41 is configured to have a higher specific resistance than the low-resistance silicon steel sheet 42, and the shield 40 is formed by laminating them. The high-resistance silicon steel sheet 41 and the low-resistance silicon steel sheet 42 each have a higher specific resistance than the metal forming the tank 30.

  The shield 40 is formed by laminating a plurality of high-resistance silicon steel sheets 41 and low-resistance silicon steel sheets 42, respectively. The high-resistance silicon steel sheet 41 and the low-resistance silicon steel sheet 42 are non-oriented silicon steel sheets having a magnetic permeability in the range of thousands to tens of thousands.

  In the shield 40, the high resistance silicon steel sheet 41 is disposed closer to the winding 20 than the low resistance silicon steel sheet 42, and the low resistance silicon steel sheet 42 is disposed closer to the tank 30. The high-resistance silicon steel sheet 41 is formed to have a smaller thickness in the lamination direction than the low-resistance silicon steel sheet 42, and is preferably set to a thickness of half or less of the entire shield 40, more preferably 1/4 or less. .

  Through holes 43 are formed in the planes of the high-resistance silicon steel sheet 41 and the low-resistance silicon steel sheet 42, and fasteners such as bolts (not shown) are formed in the through holes 43 so as not to electrically short-circuit with the silicon steel sheets 41 and 42. (Illustration) is inserted, and the respective silicon steel plates 41 and 42 are integrated. If a resin (not shown) is sandwiched between the laminations of the high-resistance silicon steel sheet 41 and the low-resistance silicon steel sheet 42, the mechanical strength is further improved, and a plate-shaped member may be sandwiched in addition to the resin.

  In the shield 40, since the axial direction of the winding 20 is the vertical direction, after the leakage magnetic flux generated from the winding 20 is incident from the upper end side and passes toward the lower end, the magnetic flux leaks from the lower end to the lower end of the winding 20. It becomes incident. Therefore, the direction in which the leakage magnetic flux flows in each of the silicon steel plates 41 and 42 is the vertical direction, and the silicon steel plates 41 and 42 are formed to have the same length in this direction. The leakage magnetic flux from the winding 20 is incident not only from the upper end of the shield 40 but also in a region below the upper end, and the integrated amount of the leakage magnetic flux in the shield 40 becomes maximum at the middle part in the vertical direction. From the part toward the upper and lower ends. The low-resistance silicon steel sheet 42 may be formed to be shorter in the vertical direction than the high-resistance silicon steel sheet 41 in order to reduce the amount of materials used in accordance with the change in the integrated amount.

  Here, in order to confirm the effect of the shield 40, simulations were performed in Examples and Comparative Examples under different conditions. In the transformer of the embodiment, a non-oriented silicon steel sheet having a specific resistance of 0.59 μΩm (for example, JIS standard C2552, type code 50A230) was used as the high-resistance silicon steel sheet 41 in the shield 40. A non-oriented silicon steel sheet having a specific resistance of 0.24 μΩm (for example, JIS standard C2552, type code 50A800) was used as the low-resistance silicon steel sheet 42. Assuming that the entire thickness of the shield 40 in the stacking direction is 100%, the thickness of the high-resistance silicon steel sheet 41 is about 16%, and the thickness of the low-resistance silicon steel sheet 42 is about 84%.

  On the other hand, in the transformer of the comparative example, a high-resistance silicon steel sheet 41 is not formed on the shield 40, that is, a non-directional silicon steel sheet having the same specific resistance of 0.24 μΩm as the low-resistance silicon steel sheet 42 in all the shields. Formed. Except for the shield, the example and the comparative example had the same configuration. The transformers of the example and the comparative example were operated under the same conditions and under the same conditions, and a simulation for measuring the loss generated by the leakage magnetic flux in the tank and the shield was performed. The results are shown in the graph of FIG. In the measurement results of FIG. 3, the measurement result of the entire transformer of the comparative example is set to “100%”, and the measurement result of the example is shown as a ratio to the comparative example. In the graph of FIG. 3, a portion represented by a halftone dot represents a loss in the tank, and a portion represented by hatching represents a loss in the shield.

  In comparison between the example and the comparative example, the loss of the entire transformer is about 75% of that of the comparative example, and the eddy current and the eddy current loss in the shield 40 are reduced by providing the high-resistance silicon steel sheet 41. It can be understood that it is suppressed. This is because the eddy current can be reduced by increasing the specific resistance, and the loss in the shield 40 becomes the product of the resistance and the square of the current. Therefore, the loss can be effectively suppressed by reducing the current. Things. In addition, it can be understood that the loss in the tank is substantially the same in the example and the comparative example, and that even when the high-resistance silicon steel plate 41 is provided as in the example, the leakage magnetic flux shielding performance for the tank is maintained.

  By forming the shield 40 from the high-resistance silicon steel sheet 41 and the low-resistance silicon steel sheet 42 in this manner, eddy current loss in the shield 40 can be reduced. Further, although the high-resistance silicon steel sheet 41, which is more expensive than the low-resistance silicon steel sheet 42, is used, the amount of the high-resistance silicon steel sheet 41 can be reduced to reduce the material cost and reduce the manufacturing cost. That is, in the present embodiment, it is possible to simultaneously suppress the loss in the shield 40 and reduce the manufacturing cost.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications. In the above-described embodiment, the size, shape, orientation, and the like illustrated in the accompanying drawings are not limited thereto, and can be appropriately changed without departing from the effects of the present invention. In addition, the present invention can be appropriately modified and implemented without departing from the scope of the object of the present invention.

  In the above embodiment, the configuration in which the present invention is applied to the transformer has been described. However, as long as the above operation and effect can be obtained, the present invention can be applied to other power stationary devices and power conversion devices.

  In addition, the contents illustrated in the above-described embodiment are schematically shown for explanation, and if the above-described effects can be achieved, the shapes of the iron core 10, the winding 20, the tank 30, and the like may be changed. Good.

  Further, in the above-described embodiment, two types of silicon steel sheets having a relatively different specific resistance, that is, a high-resistance silicon steel sheet 41 and a low-resistance silicon steel sheet 42, are laminated as the shield 40. Steel plates may be laminated. In this case, as the position is closer to the winding 20, the specific resistance may be increased, the length in the direction in which the leakage magnetic flux flows, or the thickness in the stacking direction may be reduced.

  The direction of the shield 40 in the thickness direction may be changed such that the low-resistance silicon steel plate 42 is on the winding 20 side and the high-resistance silicon steel plate 41 is on the tank 30 side.

DESCRIPTION OF SYMBOLS 1 Transformer 10 Iron core 20 Winding 30 Tank 40 Shield 41 High resistance silicon steel sheet 42 Low resistance silicon steel sheet

Claims (5)

An iron core, a winding wound around the iron core, a tank accommodating the iron core and the winding, and a shield provided along an inner surface of the tank and shielding magnetic flux toward the tank. A transformer with
A transformer, wherein the shield is formed by stacking a plurality of silicon steel plates having relatively different specific resistances.   2. The transformer according to claim 1, wherein the shield includes a high-resistance silicon steel sheet and a low-resistance silicon steel sheet, and the high-resistance silicon steel sheet is disposed closer to the winding than the low-resistance silicon steel sheet. 3. vessel.   3. The transformer according to claim 1, wherein the high-resistance silicon steel sheet and the low-resistance silicon steel sheet each have a higher specific resistance than the tank. 4.   4. The transformer according to claim 1, wherein the low-resistance silicon steel sheet is formed to have a shorter length in a direction in which a magnetic flux flows than the high-resistance silicon steel sheet. 5.   The transformer according to any one of claims 1 to 4, wherein the high-resistance silicon steel sheet is formed to have a smaller thickness in the stacking direction than the low-resistance silicon steel sheet.

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