JPH0622179B2 - Winding iron core for transformer with low iron loss - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to improvement of a wound core for a transformer having a low iron loss, which is used as an iron core of a pole transformer or the like.

As is well known, a transformer mainly uses a unidirectional electromagnetic steel plate for an iron core, but is roughly classified into a stacking transformer and a winding transformer depending on the structure of the iron core.

That is, a stacking transformer has an iron core formed by stacking steel sheets cut into a desired shape, whereas a winding transformer has an iron core formed by winding steel strips slit to a desired width. It was done.

In a laminated core that requires stacking steel sheets cut into desired shapes one by one, a large amount of labor is required to assemble the core,
In addition, since the magnetic flux flows in a direction other than the rolling direction at the joint portion of the iron core, the characteristics of the iron core tend to deteriorate as compared with the characteristics of the material. On the other hand, in the wound iron core, since the magnetic flux almost passes only in the rolling direction, the characteristics of the material are well utilized in the iron core.

Therefore, wound cores are mainly used in relatively small transformers such as pole transformers.

The wound core is made by rolling a steel strip slit to a specified width and length to a specified thickness, press-molding it, and then removing 700% to eliminate processing strain.
It is manufactured by strain relief annealing at ~ 900 ° C, and then inserting a coil into the iron core.

By the way, a unidirectional electrical steel sheet is mainly used as the material for the transformer core, but it is important that the energy loss when used as the core, that is, the iron loss is low.

Due to the recent deterioration of energy situation, the demand for magnetic steel sheets with a particularly low iron loss is increasing.

(Prior Art) By the way, in order to reduce iron loss, various attempts such as metallurgical means or artificial domain refinement have been made so far.
Among these methods, Japanese Patent Publication No. 57-2252 discloses a method of irradiating a grain-oriented electrical steel sheet, which has been finished and annealed, with a pulsed laser beam as a method which has been put to practical use and which has an extremely low iron loss.

By this method, in the case of a steel plate with a thickness of 0.30 mm, the W17 / 50 value is 1.0
It has become possible to manufacture low iron loss grain oriented electrical steel sheets of 0 W / kg or less. (W 17/50 value is magnetic flux density 1.7 T, frequency 50 H
It is the iron loss at z. However, this method has a problem that iron loss is deteriorated by strain relief annealing, and is not used as a material for wound cores.

On the other hand, the inventors of the present invention previously disclosed that in JP-A-59-197520, by introducing a linear groove in the steel sheet before the final finish annealing step, the iron loss is deteriorated even after strain relief annealing at high temperature. A method of manufacturing low iron loss unidirectional electrical steel sheet was proposed.

Further, Japanese Patent Laid-Open No. 61-117218 discloses a method of forming a groove in a finish-annealed steel sheet and then heat treating it at a temperature of 750 ° C. or higher.

These conventional techniques are different in the introduction timing of the groove and the principle of reducing the iron loss, but both of them are intended to reduce the iron loss by introducing the groove into the steel sheet.

When applying a steel sheet having a groove introduced to a wound core for a transformer, the inventors have found that the characteristics of the material are not sufficiently utilized in the core depending on the winding method, and disclosed in JP-A-61-15309 previously. did. That is, it is a winding core for a transformer in which a unidirectional electrical steel sheet having a linear flaw (groove) on one surface is wound so that the linear flaw (groove) is on the outer winding side.

(Problems to be solved by the invention) However, as a result of further investigation, it was found that it may be better to set the linear flaw (groove) on the inner winding side rather than on the outer winding side.

As a result of intensive experiments and investigations on what causes such a phenomenon, the inventors have found that when the bending diameter of the bent portion on the innermost side of the iron core is smaller than a certain value, a linear groove is formed. The inventors have newly found out that it is better to wind the so that it is on the inner winding side, and came to accomplish the present invention.

(Means for Solving Problems) The present invention provides a cotton-like groove on one surface with a groove width of 300 μm or less,
A wrapping iron core formed by winding unidirectional electrical steel sheets formed with a groove depth of 100 μm or less, a groove centerline spacing in the rolling direction of 1 mm or more, and an angle of 30 ° or more with the rolling direction,
A wound core for a transformer with low iron loss, wherein the linear groove faces the inner winding side and the innermost bent portion has a radius of curvature of 30 mm or less.

The present invention will be specifically described below.

By winding a grain-oriented electrical steel sheet with a thickness of 0.23 mm, which is manufactured by a normal manufacturing method, around a formwork with various curvature radii (R) as shown in Fig. 1, the radius of curvature of the innermost bent portion of the iron core is Different winding cores (A) were created.

In addition, it has the same composition as (A) and has a width of 100 μm and a depth of 15 μm on one surface in a direction substantially perpendicular to the rolling direction, and a line thickness of 0.23 mm with a linear groove at an interval of 7 mm in the rolling direction. Core (C) with a magnetic electrical steel sheet wound in a form similar to that of (A) so that the linear grooves are wound on the outside, and the core (c) is wound so that the linear grooves are wound inside. Created.

The winding thickness of each iron core was 40 mm. As for material characteristics, the steel plate without linear grooves has a B ₁₀ value of 1.92T and a W 17/50 value of 0.
90 W / kg, steel sheet with linear grooves has a B ₁₀ value of 1.91
The value of T, W17 / 50 is 0.81 W / kg, and the steel sheet with linear grooves shows a low iron loss value even if the composition is the same.

Here, the B ₁₀ value is the magnetic flux density at a magnetizing force of 1000 A / m, and the W 17/50 value has already been described.

Next, in order to remove the processing strain of the above iron core, 800 ℃ × 2hrs, N ₂
After performing the strain relief annealing in the inside, winding was performed and the magnetic characteristics were measured.

Fig. 2 shows the relationship between the radius of curvature of the innermost bent portion of the iron core and the core loss of the bent iron core.

Fig. 2 shows that iron cores (B) and (C) using steel plates with linear grooves have lower iron loss than iron cores (A) using normal steel plates without grooves, and The iron loss improving effect of the material is well reflected in the iron core.

On the other hand, comparing between (B) and (C), the radius of curvature of the bent part is
If it is larger than 30 mm, the core wound so that the linear groove is wound outside is the core wound so that it is wound inside.
Lower iron loss than (C), but the bending radius of bending is 30mm
In the following cases, the inner winding (C) has lower iron loss.

Therefore, in a transformer winding core in which the innermost bent part is bent with a radius of curvature of 30 mm or less, a unidirectional electrical steel sheet with a linear groove on one surface is used for the linear groove. By winding so as to achieve the following, it has become possible to manufacture wound cores for transformers with lower iron loss than ever before.

(Working) When the radius of curvature of the bent part is small, the iron loss is lower when the linear groove is wound on the inner winding, and when the radius of curvature of the bent part is large, the linear groove is wound on the outer winding. The reason why the lower iron loss is obtained by stacking the layers is presumed as follows.

When the radius of curvature of the bent portion is large and the groove is wound in the groove, the magnetic flux spreads to the adjacent steel plates around the groove, so that magnetic flux in the plate thickness direction occurs and iron loss deteriorates. However, in the case of the outside winding of the groove, the groove widens in the bent portion, so that the ratio of the magnetic flux in the plate thickness direction is smaller than that in the case of the inside winding.

On the other hand, when the radius of curvature of the bent portion is small, it is considered that when the groove is wound inwardly, the groove becomes narrow and the flow of magnetic flux is almost the same in both inner winding and outer winding.

However, in the bent part of the wound core, tensile stress is usually applied to the outer surface and compressive stress is applied to the inner surface, but if there is a groove on the inner surface, the compressive stress is relieved, and therefore lower than in the case of groove outer winding. It is estimated that iron loss will occur.

In FIG. 2, the iron loss is lower when the radius of curvature of the bent portion is smaller, and when the radius of curvature of the bent portion is large, the ratio of the portion to which the strain due to the bending is applied is large, which deteriorates the iron loss. It is thought to be due to the cause.

Next, regarding the shape of the linear groove which the material used for the winding core for a transformer of the present invention should have, as shown in JP-A-59-197520, the width is 300 μm or less, the depth is 100 μm or less, and the rolling is performed. It is preferable that the distance between the groove center lines in the direction is 1 mm or more, and the direction is substantially perpendicular to the rolling direction. When deviating from each range, the effect of reducing the iron loss of the material cannot be sufficiently obtained. Especially, when the width of linear groove is 30 to 150 μm, the depth is 10 to 30 μm, the distance between rolling directions is 3 to 20 mm, and the angle with the rolling direction is 30 ° or more, the W17 / 50 value is 0.05 W / kg or more. It has the effect of reducing iron loss.

The groove needs to be linear, and the linear shape may be a straight line, a curved line, a wavy line, a broken line, or a dotted line.

Further, the steel sheet may or may not have a phosphate-based topcoat coating.

(Example) Next, the Example of this invention is described.

1. 7 kinds of cold-rolled sheet of silicon steel containing 0.23mm thickness with 100μm wide and 12μm deep linear grooves introduced at 8mm intervals in the direction perpendicular to the rolling direction, and the other half is manufactured normally. Made into a product by the process. At this time, the magnetic properties of the steel sheet with grooves were B ₁₀ value of 1.91 T and W 17/50 value of 0.78 W / kg, and the steel sheet without grooves had B ₁₀ value of 1.92 T and W 17/50 value of 0.89 W / kg.

Next, this steel plate was divided into two parts, one with or without the introduction of linear grooves, each of which was slit into a steel strip having a width of 100 mm, which was wound up to a winding thickness of 40 mm and then press-formed. At this time, the radius of curvature of the innermost bent portion of the iron core is adjusted so as to have various diameters shown in Table 1.For steel plates with linear grooves, the core winding method is In the case of outer winding, there are two types.

In addition, these cores are 820 ℃ × 2hr to remove processing strain.
Strain relief annealing was performed in s. N ₂ .

The iron loss characteristics of the iron core at this time are shown in Table 1 in comparison with the case of using a steel sheet without linear grooves. The radius of curvature of the bent portion indicates the radius of curvature of the innermost bent portion of the iron core.

As shown in Table 1, a wound core using a steel sheet having linear grooves exhibits lower iron loss than a wound core using a steel sheet having no groove at any bending radius of curvature, but In the wound core with a radius of curvature of 30 mm or less in the inner bent part, by winding so that the linear groove is on the inner winding side, the remarkable iron loss reduction effect of the material is sufficiently reflected in the iron core,
It has become possible to manufacture wound cores with lower iron loss.

2. A 0.30 mm thick finish annealed unidirectional electrical steel sheet coil was introduced with linear grooves with a width of 120 μm and a depth of 15 μm at intervals of 5 mm in the direction perpendicular to the rolling direction. Was divided into those with and without. At this time, the magnetic properties of the steel sheet with grooves introduced are B ₁₀ value, 1.91T,
W17 / a 50 value 0.92 W / kg, no groove steel plate B ₁₀ value, 1.
The 92T, W17 / 50 value was 1.03 W / kg.

Next, each split coil was slit into a steel strip having a width of 100 mm, which was wound up to a winding thickness of 40 mm and then press-formed. At this time, the radius of curvature of the bent portion at the innermost side of the iron core is adjusted so as to have various diameters shown in Table 2, and for a steel plate having a linear groove, the winding method of the iron core is that the linear groove is internally wound. In the case of No. 2, there were two types of cases of outer winding.

In addition, these cores are 850 ℃ x 2hr to remove processing strain.
s, Strain relief annealing was performed in N ₂ .

The iron loss characteristics of the iron core at this time are shown in Table 2 in comparison with the case of using a steel sheet without linear grooves. The radius of curvature of the bent portion indicates the radius of curvature of the innermost bent portion of the iron core.

As shown in Table 2, the wound core using the steel sheet having the linear groove introduced exhibited a lower core loss than the wound core using the steel sheet having no groove at any bending radius of the bending portion. In the wound core with a radius of curvature of 30 mm or less in the innermost bent part, the linear groove is wound inward so that the remarkable iron loss reduction effect of the material is sufficiently reflected in the iron core and lower iron It became possible to manufacture a loss winding core.

(Effects of the Invention) According to the present invention, it is possible to manufacture a wound core for a transformer having a significantly low iron loss, which can contribute to energy saving.

[Brief description of drawings]

Fig. 1 is an explanatory view showing a form making a wound core, and Fig. 2 is a comparison showing the relationship between the radius of curvature of the innermost bent portion of the wound core and the iron loss W17 / 50 (W / kg) of the wound core. It is a figure.

Claims (1)

[Claims] 1. A linear groove on one surface of which a groove width of 300 μm or less,
A wrapping iron core formed by winding unidirectional electrical steel sheets formed with a groove depth of 100 μm or less, a groove centerline spacing in the rolling direction of 1 mm or more, and an angle of 30 ° or more with the rolling direction,
A wound core for a transformer with low iron loss, wherein the linear groove faces the inner winding side, and the radius of curvature of the innermost bent portion is 30 mm or less.