CN110729107A

CN110729107A - Transformer device

Info

Publication number: CN110729107A
Application number: CN201910427529.4A
Authority: CN
Inventors: 今川尊雄; 馆村诚; 佐藤孝平; 阿部将; 安东邦彦; 相马宪一
Original assignee: Hitachi Production Machine System
Current assignee: Hitachi Production Machine System; Hitachi Ltd
Priority date: 2018-07-17
Filing date: 2019-05-22
Publication date: 2020-01-24
Also published as: JP2020013840A

Abstract

The invention provides a transformer capable of reducing loss and noise. A transformer includes a wound core having an opening on a main surface, the opening having a shape in which a length in a direction of a magnetic path is longer than a length in a width direction of the wound core.

Description

Transformer device

Technical Field

The present invention relates to a transformer, and more particularly, to a transformer with reduced noise and loss.

Background

Conventionally, a magnetic material having high magnetic permeability and high magnetic flux density, such as a grain-oriented electrical steel sheet or an amorphous body, is used for an iron core used in a transformer. In particular, amorphous foils have extremely low coercive force, which is 1/10 to 1/100 times that of electromagnetic steel sheets, and have a foil resistivity 10 times that of grain-oriented electromagnetic steel sheets, and are also superior in eddy current loss.

However, the magnetostriction constants of the amorphous body and the grain-oriented electrical steel sheet are large as compared with those of soft magnetic materials such as C-grade permalloy, and as a result, there is a problem that the magnetostriction vibration accompanying the excitation of the magnetic body is large and the noise generated from the iron core is large.

The magnetostriction phenomenon is a phenomenon in which the length of a magnetic body changes due to saturation of the magnetic body in a demagnetized state. If the magnetostriction constant is positive, the ratio of the magnetostriction constant to the extension of the magnetic material is indicated. Further, since expansion and contraction do not depend on the saturation polarity direction, it is considered that expansion and contraction that is saturated in a certain magnetic pole direction expands and contracts and vibrates due to passing through a state where the excitation direction and the magnetization direction do not match in the process of saturation in the opposite magnetic pole direction in accordance with the magnetization reversal. The fine magnetic domains inside the dispersed magnetic body in the demagnetized state reflect the change of the structure that is uniform in one direction when magnetized.

In an electrical steel sheet, the smaller the domain width, the smaller the average moving distance of the domains, and this is called reduction in loss and noise. As a technique for reducing noise in an amorphous body, a technique has been studied from an electrical steel sheet in many cases. Patent document 1 discloses a soft magnetic amorphous alloy ribbon having low loss and low apparent power, in which shallow holes are regularly opened by a laser.

Documents of the prior art

Patent document

Patent document 1: WO2011/030907

Disclosure of Invention

Technical problem to be solved by the invention

Unlike electromagnetic steel sheets, it is known that a magnetic domain of an amorphous body becomes a wide magnetic domain. In addition, it is considered that magnetization reversal is difficult in the magnetic region of the amorphous body.

In the technique disclosed in patent document 1, the recess and the annular protrusion are formed by laser irradiation, and thus the iron loss is reduced, but the effect of reducing noise is not clear.

Therefore, the inventors considered that magnetization inversion can be facilitated by controlling the magnetization direction of the magnetic domains in a magnetic material such as an amorphous body, which is difficult to be magnetization-inverted, and that loss and noise can be reduced.

The invention aims to provide a transformer capable of reducing loss and noise.

Means for solving the problems

A preferred example of the present invention is a transformer having a wound core having an opening on a principal surface, the opening having a shape in which a length in a direction of a magnetic path is longer than a length in a width direction of the wound core.

Effects of the invention

According to the invention, the loss and noise of the transformer can be reduced.

Drawings

Fig. 1 is a view showing an amorphous foil in example 1.

FIG. 2 is a graph showing the relationship between the slit forming method and the magnetic properties in example 2.

Fig. 3 is a diagram illustrating embodiment 3.

Fig. 4 is a graph showing the relationship between the slit shape and the magnetic characteristics in example 4.

Fig. 5 is a diagram showing a transformer in example 5.

Fig. 6 is a diagram showing structural components of a transformer in example 5.

Fig. 7 is a diagram showing an external appearance of the transformer.

Detailed Description

Hereinafter, embodiments will be described with reference to the drawings.

Example 1

First, the definition of the shape of the slits 10 provided in the amorphous foil will be described. Fig. 1 is a plan view showing an amorphous foil of example 1. The slit 10 can be realized by adding a cut on the amorphous foil. The slits 10 serving as openings linearly reduce the thickness of the amorphous foil from one side of the amorphous foil surface to the opposite side, thereby having an effect of changing the ease of magnetization parallel to and perpendicular to the slits 10 and reducing the applied magnetic field Hm in the direction parallel to the slits 10. In addition, the value of the magnetization saturation magnetic field in the direction perpendicular to the slit 10 indicates the magnetic anisotropy. Reference numeral 13 in fig. 1 denotes a magnetic path, and reference numeral 14 denotes a width direction of the amorphous foil. Reference numeral 12 denotes a slit interval. The applied magnetic field Hm represents an applied magnetic field when the maximum magnetic flux density Bm is measured.

In particular, by making the slits 10 so deep as to penetrate the amorphous foil, an appropriate magnetic anisotropy is imparted in the amorphous foil surface, and the magnetization is stabilized. The slits 10 are longer along the amorphous foil surface, the applied magnetic field Hm is reduced, but need not be so long as to cut the amorphous foil. When the slits 10 do not reach the end face of the amorphous foil, the strength of the amorphous foil can be maintained high.

The slit 10 is formed after setting the slit 10 to a predetermined length (slit length), and the same effect as that of the long slit 10 is obtained. Since the shorter the length between the slits 10 (the slit pitch 11), the easier the amorphous foil is cut, the ratio of the slit length to the slit pitch 11 can be maintained at 1: 1-10: 1. By forming the slit shape, the transformer core can be shaped without breaking the amorphous foil.

By providing the amorphous foil with magnetic anisotropy of an appropriate magnitude and forming a magnetic domain structure in which the magnetic domain directions are made uniform, magnetization reversal can be easily achieved. As a result, the loss and the magnetostrictive vibration can be reduced. The shape anisotropy is most effectively used as a method of imparting magnetic anisotropy to a magnetic body. In this way, when the magnetic material is made into an anisotropic shape, for example, a rod shape, magnetization in the longitudinal direction of the rod is easily performed. This means that the rod exhibits the same effect whether it exists in a space alone or as a space inside a uniform magnetic body. Example 1 is an example in which magnetic anisotropy is imparted to an amorphous foil by adding a notch to the amorphous foil.

Example 2

The slit of fig. 1 is formed by a method such as shearing, diamond blade machining, laser machining, or the like. In example 2, an amorphous foil having one side of a square of 50mm was used. Fig. 2 (a) is a plan view of an amorphous foil in example 2. Fig. 2 (b) shows table 1 showing the slit formation method and the magnetic characteristics of example 2.

As shown in fig. 2 (a), the magnetic characteristics of the different forming methods were compared by forming slits at a slit interval of 30mm from the end of the amorphous foil to 45 mm.

In the formation of the slits, the slits cut by the pulsed laser and the shear were compared. The laser beam was pulsed at picosecond excitation, and the slit was created by repeatedly scanning the slit while keeping the output constant at 38W and changing the scanning speed and the number of repetitions.

After the slits were formed in the sample, the working distortion was removed by heat treatment. For comparison, a sample (sample) was prepared by heat treatment. The magnetic characteristics are W10/50, which is a loss when the amorphous foil is excited to 1T at 50Hz, and an applied magnetic field Hm. As shown in fig. 2 (a), the measurement range 21 is measured between 36mm in the direction of the slit.

The measured values are shown in Table 1. In the case where the comparative sample was cut 13 times at a scanning speed of 2m/s, the loss of W10/50 increased by 40%, and the amorphous foil was broken by thermal stress.

In the case of increasing the scanning speed to 4m/s, the loss of W10/50 increased by 60% at 25 times of scanning, although the amorphous foil was not destroyed.

On the other hand, when the scanning speed was increased to 8m/s and the number of scans was 50, the loss of W10/50 was about the same as that of the sample. In contrast, the loss of W10/50 was reduced by 20% when shear was used.

Here, when the slit is formed by the laser beam, a tapered cross section having a V-shape is formed from the main surface of the amorphous foil on the laser beam irradiation side toward the main surface on the opposite side. When the slits are formed by shearing, the processed surfaces of the slits have a substantially perpendicular cross-sectional shape with respect to the main surface of the amorphous foil, and the magnetic anisotropy is high during shearing, thereby increasing the noise reduction effect. On the other hand, machining is easy when using a laser.

In addition, the applied magnetic field Hm was increased relative to the sample at a scanning speed of 2 m/s. When the scanning speed was 4m/s or 8m/s, or when shearing was used, the applied magnetic field Hm was lower than that of the sample. It is found that the slit formation under more appropriate conditions has an effect of reducing the applied magnetic field.

The applied magnetic field required to be able to reduce the constant magnetization corresponds to being able to easily reverse the magnetization. This is equivalent to a reduction in the excitation capacity in the transformer. That is, according to embodiment 2, magnetization reversal can be facilitated, and therefore, noise can be reduced in the case where an amorphous foil is used for the core.

Example 3

As a method of continuously forming slits in an amorphous foil, there is a method of continuously punching and conveying a foil to form slits by matching a blade length with a slit length if shearing is performed with a small loss.

On the other hand, when a laser is used, the processing width can be freely changed by programming, and the processing is simple. Therefore, in order to grasp the influence of the slit on the magnetic properties, slit processing was performed under the laser processing conditions of the scanning speed of 8m/s at which the loss and applied magnetic field were small, which were obtained in example 2.

Fig. 3 (a) is a plan view of an amorphous foil in example 3. The slit length was set to 12mm, and the slit pitch was set to 3mm, and the slits were formed in 3 places. Further, 2 additional portions were formed at a slit interval of 30mm, and slits were formed at 6 total portions. Fig. 3 (a) shows the amorphous foil with the slit formed and the magnetic measurement site. Further, the sample was subjected to heat treatment. As the measurement site, a portion shown by a slit having a width of 36mm shown in FIG. 3 (a) and a portion shown by no slit were measured and compared.

The reason for this comparison is that the amorphous foil increases the applied magnetic field particularly at a magnetic flux density near saturation. Therefore, the comparison of the applied magnetic field in the vicinity of saturation requires that the thicknesses of the amorphous foils be precisely matched, and the effect of the presence or absence of the slit is determined by processing half of the same foil and comparing the magnetic characteristics of the processed portion having the slit and the non-processed portion having no slit.

Fig. 3 (b) shows the measurement results of the loss (W/kg) at W10/50 on the vertical axis and the magnetic flux density b (t) on the horizontal axis. As shown in fig. 3 (b), when there are slits indicated by black circles, the loss in the vicinity of 1.5 to 1.6T is smaller than when there are slits indicated by unnecessary white circles, and the effect of providing slits is obtained.

Fig. 3 (c) shows the measurement results of the applied magnetic field Hm (a/m) on the vertical axis and the magnetic flux density b (t) on the horizontal axis. As shown in fig. 3 (c), when there is a slit, the applied magnetic field Hm decreases in the vicinity of 1.6T. This means that the formation of the slits leads to a reduction in the applied magnetic field, and as a result, a reduction in the excitation current in the transformer is achieved. The possibility of excitation at a low current means that the formation of the slits to the amorphous body is effective in reducing noise.

Example 4

Fig. 4 (a) is a plan view of an amorphous foil of example 4. In example 4, the slit interval was changed by setting the slit interval to 30mm and the slit pitch to 20 mm. In the present example, an amorphous foil having a maximum width L of 213mm was examined, as to whether it is effective to form slits with a width of 142mm to 213 mm. The width 213mm of the amorphous foil was measured by a measuring instrument having a measuring length of 150mm, and the measurement was performed by applying a magnetic field in the slit direction. Further, the sample was subjected to heat treatment. The slit formation is expressed as how the amorphous foil surface is divided. The division of the amorphous foil was made vertically symmetrical, and the division up to the division number of 20 was examined. For example, when the resin composition is divided into 2 parts, the width D is 106 mm. Here, the decimal point or less is rounded off.

Fig. 4 (b) shows table 2 showing the relationship between the slit shape and the magnetic characteristics in example 4. Table 2 shows the W10/50 loss and the applied magnetic field Hm of the excitation under the conditions of 50Hz and 1T for the number of divisions and the value of each width D. In the case of no division, the loss in the case of division from 4 parts to 8 parts is reduced as compared with the loss in the case of a width of 213 mm. In addition, the applied magnetic field Hm was reduced from 2 parts to 14 parts. From the results, it is understood that formation of an appropriate slit is effective for reducing the loss and reducing the applied magnetic field.

Example 5

Fig. 5 shows an internal structure of a 3-phase 3-limb transformer in example 5. Fig. 7 is a diagram showing an external appearance of the transformer. Reference numeral 71 denotes a primary side terminal provided on the upper portion of the can 74, and is a terminal to which a high-voltage power supply transmitted from a power plant or the like is connected. Reference numeral 72 denotes a secondary terminal provided at an upper portion of the tank-shaped container 74, and is a terminal connected to transmit a voltage boosted or dropped by a transformer to a load side. The heat sink 73 is provided on the periphery of the can-like container 74 to cool heat generated from the coil, the core, and the like.

The transformer tank 74 includes an outer core 50,

inner cores

51a and 51b,

primary windings

53a, 53b, and 53c for u-phase, v-phase, and w-phase, and

secondary windings

54a, 54b, and 54 c. In the slit-processed core of the present embodiment, the present embodiment is applied to all of the outer core 50 and the

inner cores

51a and 51b, or to any one of the outer core 50 and the

inner cores

51a and 51 b.

Fig. 6 (a) is a perspective view of the inner core 51 a. Although the core is an inner core, the primary winding and the secondary winding may be wound around the single core to operate as a single-layer transformer. The core is a wound core, and amorphous foils cut into short pieces are laminated and combined with a part of the wound core to form an overlapping portion, and the core is formed in a rectangular shape. As shown in fig. 6 (b), slits 10 are formed in the main surface 52 of the wound core.

Fig. 6 (b) is a view showing an amorphous foil constituting the core. On the main surface of the amorphous foil or the wound core, a magnetic path is formed along the longitudinal direction, and a slit 10 is formed.

The slit 10 as an example of the opening portion has an opening that is longer in a direction closer to the direction 13 of the magnetic circuit than the width direction 14 of the wound core. The shape of the opening may be a shape having a long side and a short side or a long axis and a short axis. The opening may be provided in a portion different from the end face of the wound core, or the long side of the opening may be in contact with the end face of the wound core. By forming such a shape, appropriate magnetic anisotropy is provided, magnetization inversion is facilitated, and loss and noise can be reduced.

When the opening is provided at a portion different from the end face of the wound core, the strength of the wound core is maintained high. When the long side of the opening is brought into contact with the end face of the wound core, the length of the opening can be easily selected, and magnetic anisotropy can be easily imparted.

Further, the strength of the wound core can be maintained by making the depth of the opening smaller than the thickness of the main surface of the wound core. When the opening portion penetrates the main surface of the wound core, magnetic anisotropy is easily imparted. Further, in a part of the laminated amorphous foils, an amorphous foil which is a portion different from the opening portion and is not provided with the slit is disposed in a connected manner, and the depth of the opening portion is shortened to be smaller than the thickness of the wound core, so that the strength of the wound core can be maintained.

In this example, the amorphous foil is continuously cut into a predetermined length by a pulse laser or shearing to form a slit. Here, a pulse laser of the width of the amorphous foil is used. Using an amorphous foil having a width of 170mm, 3 rows of slits 10 were formed on the amorphous foil. In fig. 6 (b), reference numeral 13 denotes a direction of a magnetic path of the wound core, and reference numeral 14 denotes a width direction of the wound core.

In this case, the slit width was 28 mm. The slit length and the slit pitch were 30mm and 10mm, respectively, and the processing start/end position was determined so that the slit 10 did not act on the cut portion. The amorphous foils are stacked to form a core.

The width of the opening of the wound core was set to 60mm, the height was set to 140mm, and the thickness of the wound core was set to 30 mm. Then, the iron core is heat-treated in a magnetic field. Then, an insulating paper was wound around the wound core, and in the test, 30 turns were wound on the primary side and 20 turns were wound on the secondary side, and the magnetic characteristics were measured by exciting the primary side and measuring the winding output on the secondary side.

As a winding core for comparison, a winding core without the slits 10 was prepared, and a loss value and an excitation current were measured in a state where a winding of the same configuration was wound. As a result, it was found that the loss at 50Hz and an average magnetic flux density of 1.5T close to the saturation of the core can be reduced by 5% in the case of the slits as compared with the case of no slits. In addition, the current value required for excitation can be reduced by 10%, and improvement in efficiency can be confirmed. As a result of the reduction in the excitation current, it was found that the noise generated from the wound core was also reduced by 5dB, and the slit formation was also effective for noise reduction.

When the amorphous foil is provided with the slits by the laser beam, the size of the openings on the main surface on the opposite side is smaller than the openings on the irradiation side. For example, the short side or the short axis of the opening is shorter on the lower surface side than on the upper surface side of the amorphous foil constituting the wound core, and the cross section is V-shaped. When a laser is used, the slit can be easily formed as compared with the case of using a cut slit.

When the slits are formed in the amorphous foil by cutting, the amorphous foil has a shape having a substantially perpendicular cross section to the main surface of the amorphous foil constituting the wound core, and magnetic anisotropy is easily imparted thereto.

Example 6

The formation of the inner core 51a by the slits 10 shown in embodiment 5 can be realized by the next scheme. First, a wound core in which the slits 10 are not formed is manufactured. At this time, an opening portion having a width wider than the shape of the slit 10 is formed in advance in the inner mold for forming the iron core. Next, the slits 10 are formed in the inner periphery of the core by laser light from the opening. At this time, the slit length was set to 30mm, the pitch was set to 10mm, and the slit interval was set to 25 mm. The depth of processing under the laser was 10 mm. Then, the iron core is formed by performing heat treatment.

As a result of the same measurement as in example 5, it was found that the excitation current value was reduced by 5% and the noise was reduced by 3dB, although no change in the loss was observed during the machining. In this case, since the laser-processed cross section has a V-shape, the volume inside the core is reduced, and the magnetic flux density in this portion is increased, so that it is considered that the loss is not changed without processing.

In the case of this slit forming method, the iron core can be machined by a diamond cutter. In this case, the tool diameter is set to the slit length, whereby machining of about 1/3 degrees in the tool diameter can be performed. However, cooling with pure water or using lubricating oil or the like requires a message to prevent oxidation of the core.

Description of the reference numerals

10: slit

11: slit spacing

12: slit spacing

50: outer iron core

51a, 51 b: an inner core.

Claims

1. A transformer having a wound core, characterized by:

the wound core has an opening portion on a main surface, and the opening portion has a shape in which a length in a direction of a magnetic path is longer than a length in a width direction of the wound core.

2. The transformer of claim 1, wherein:

the wound core has the opening portion having a depth different from the thickness of the main surface.

3. The transformer of claim 1, wherein:

the opening has long sides and short sides or long axes and short axes.

4. The transformer of claim 1, wherein:

the opening is provided at a portion different from an end surface of the wound core.

5. The transformer of claim 3, wherein:

the long side of the opening portion is in contact with the end face of the wound core.

6. The transformer of claim 2, wherein:

the opening has a depth shorter than the thickness of the member of the wound core.

7. The transformer of claim 1, wherein:

the opening is a hole penetrating through an upper surface and a lower surface of the one-piece metal member of the wound core.

8. The transformer of claim 3, wherein:

the short side or short axis of the opening on the lower surface side of the metal member of the wound core is shorter than the short side or short axis of the opening on the upper surface side.

9. The transformer of claim 7, wherein:

the wound core has a piece of metal member connected to a portion other than the opening portion.

10. The transformer of claim 1, wherein:

the opening is a slit provided in the metal member of the wound core.

11. The transformer of claim 1, wherein:

the wound core is an amorphous metal member.

12. The transformer of claim 3, wherein:

the opening has a cross section substantially perpendicular to a main surface of a metal member constituting the wound core.

13. The transformer of claim 10, wherein:

the slit length of the slit is greater than the length of the slit pitch.