JPS6394608A - Wound core for low iron-loss transformer - Google Patents

Abstract

PURPOSE:To obtain the low iron loss unidirectional electromagnetic steel plate having low iron loss even after performance of distortion-removing annealing at a high temperature by a method wherein, when the bending diameter of the worked part on the innermost side of iron core is smaller than a certain fixed value, a linear groove is lap-wound in such a manner that the groove will be positioned on the side of the inner winding. CONSTITUTION:In the iron core consisting of the lap-wound unidirectional electromagnetic steel plate on which a linear groove is formed on its one surface and also in the transformer iron core having a part on the innermost side of the iron core subjected to a bending work of a curvature radius of 30 mm or smaller, a unidirectional electromagnetic steel plate having a linear groove on one surface is lap-wound in such a manner that the linear groove will be positioned on the side of the inner winding. As a result, the wound iron core for transformer having low iron loss can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the improvement of a wound core for a transformer with low iron loss, which is used as the core of a pole-mounted transformer.

As is well known, transformers mainly use unidirectional electrical steel sheets for their cores, and are broadly classified into stacked transformers and wound transformers depending on the configuration of the core.

In other words, a stacked transformer has an iron core formed by laminating steel plates cut into a desired shape, whereas a wound transformer has an iron core formed by stacking copper strips slit to the desired width. It is what was done.

Stacked cores require a lot of effort to assemble the core, which requires cutting steel plates into the desired shape and stacking them one by one.
Furthermore, since magnetic flux flows in a direction other than the rolling direction at the joints of the iron core, the characteristics of the iron core tend to deteriorate more than the characteristics of the material. On the other hand, in a wound core, almost all magnetic flux passes only in the rolling direction, so the characteristics of the material can be effectively utilized in the core.

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

The wound core is made by rolling copper strips slit to a specified width and length to a specified thickness, then press-forming them to remove processing distortion (to remove 70%
It is manufactured by stress relief annealing at 0 to 900°C, and then inserting a coil into the iron core.

Incidentally, unidirectional electrical steel sheets are mainly used as materials for transformer cores, but it is important that energy loss, that is, iron loss, be low when used as the core.

Due to the deterioration of the energy situation in recent years, the demand for electrical steel sheets with particularly low iron loss is increasing further.

(Prior Art) Various attempts have been made to reduce iron loss, including metallurgical means and artificial domain subdivision.

Among these methods, Japanese Patent Publication No. Sho 57-2252 discloses a method of irradiating a finish-sintered grain-oriented electrical steel sheet with pulsed laser light, which is currently in practical use and provides extremely low iron loss. .

Using this method, in the case of a steel plate with a thickness of 0.3 On+, W 1?
150 value is 1. It has become possible to manufacture grain-oriented electrical steel sheets with low core loss of OOW/kg or less. (Here, the W 1 - 150 value is the iron loss at a magnetic flux density of 1.7 T and a frequency of 50 Hz.) However, this method has the problem that iron loss deteriorates due to strain relief annealing, and the material for the wound core is It is not used as such.

In contrast, the inventors previously proposed
In Publication No. 0, we proposed a method for producing a low core loss unidirectional electrical steel sheet that does not deteriorate in core loss even after strain relief annealing at high temperatures by introducing linear grooves into the steel sheet before the final finish annealing process. .

Furthermore, JP-A-61-117218 discloses a method in which grooves are formed in a finish-hardened pure steel sheet and then heat treated at a temperature of 750 DEG C. or higher.

Although these conventional techniques differ in the timing of groove introduction and the principle of reducing iron loss, they all aim to reduce iron loss by introducing grooves into a steel plate.

When applying a steel plate with grooves to a wound core for a transformer, the inventors found that depending on the winding method, the characteristics of the material could not be fully utilized in the core.
This was disclosed in Publication No. 9. That is, it is a wound core for a transformer, which is made by winding unidirectional electrical steel sheets with linear flaws (grooves) on one surface so that the linear flaws (grooves) are on the outer winding side.

(Problem to be solved by the invention) However, further investigation revealed that there are cases in which it is better to place the linear flaws (grooves) on the inward side rather than on the outward side. .

The inventors conducted extensive experiments and studies to find out what causes this phenomenon, and found that if the bending diameter of the innermost bending part of the core is smaller than a certain value, a linear groove is formed. He discovered that it is better to wind the winding so that it is on the inner playing side, which led him to create this invention.

(Means for Solving the Problems) This invention provides a wound core made by winding unidirectional electrical steel sheets with linear grooves formed on one surface, so that the linear grooves face the inner side. and the radius of curvature of the innermost bent part is 30
This is a wound core for transformers with a low iron loss.

This invention will be explained in detail below.

The radius of curvature of the innermost bending part of the core is determined by winding a grain-oriented electrical steel sheet with a thickness of 0.23 mm manufactured using a conventional manufacturing method around formworks having various radii of curvature (R) as shown in Figure 1. A wound core (A) with different values was created.

Also, a plate rg-O which has the same composition as (A) and has a linear hook on one surface in a direction substantially perpendicular to the rolling direction, having a width of 100 μm and a depth of 15 μm, and an interval of 7 dragons in the rolling direction.

An iron core (B) is made by winding a 231 mm grain-oriented electrical steel sheet in a formwork similar to (A) so that the linear grooves are on the outer side, and an iron core (B) is wound so that the linear grooves are on the inner side. c) was created.

The winding thickness of both cores was 40 m. In addition, the material properties of the steel plate without linear grooves are 81° value 1.92T, W
1?150 value is 0.90W/kg, and the steel plate with cotton grooves has a B111 value of 1.91T and a W1?150 value of 0.
81 W/kg, and the steel plate with linear grooves shows a lower iron loss value even if the composition is the same.

Here B. The value is the magnetic flux density at a magnetizing force of 1000 A/n+, and the W17150 value has already been described.

Next, the above iron core was heated to 800°C x 2hrs to remove processing distortion.
% Nz, and then winding was performed and the magnetic properties were measured.

Figure 2 shows the relationship between the radius of curvature of the innermost bent portion of the core and the core loss of the wound core.

From Figure 2, iron core using a steel plate with linear grooves (B)
(C) are iron cores made of ordinary steel plates without grooves (A
), and the iron loss improvement effect of the material by introducing linear grooves is well reflected in the iron core.

On the other hand, when comparing between (B) and (C), if the radius of curvature of the bent part is larger than 301 mm, the core (B) wound so that the linear grooves are wound on the outside is better. Although the iron loss is lower than that of the iron core (C) wound as a winding, when the radius of curvature of the bent portion is 3Q mm or less, the inner winding (C) has a lower iron loss.

Therefore, in a wound core for a transformer in which the innermost bending part of the core is bent with a radius of curvature of 30 m or less, a unidirectional electrical steel sheet having a linear groove on one surface is used, and the linear groove is on the inner winding side. By winding the core in such a way, it became possible to manufacture a wound core for transformers with the lowest iron loss ever.

(Function) When the radius of curvature of the bent part is small, it is better to wrap the linear groove inwardly to reduce core loss, and when the radius of curvature of the bent part is large, it is better to wrap the linear groove outwardly. The reason why the iron loss is lower when stacked is assumed to be as follows.

If the radius of curvature of the bending part is large and the groove is internal, the magnetic flux will pass to the adjacent steel plate around the groove, so magnetic flux will occur in the plate thickness direction and the iron loss will deteriorate. However, in the case of outer groove winding, the groove widens at the bent portion, so the rate of magnetic flux generated in the plate thickness direction is smaller than in the case of inner winding.

On the other hand, when the radius of curvature of the bent portion is small, the groove becomes narrower when the groove is wound internally, so that the flow of magnetic flux is considered to be approximately the same for both the internal and external windings.

However, in the bending part of a 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 relaxed, and therefore the stress is lower than in the case of outer groove winding. It is presumed that this will result in iron loss.

In Figure 2, the reason why the iron loss is lower when the radius of curvature of the bent part is small is that when the radius of curvature of the bent part is large, the proportion of the part that is subjected to strain due to bending is large, and this deteriorates the iron loss. This is thought to be due to the cause.

Next, regarding the shape of the linear groove that should be provided in the material used in the wound core for a transformer of the present invention, please refer to Japanese Patent Application Laid-Open No. 59-197520.
As shown in the publication, width 300μm or less, depth 100μm
It is preferable that the distance between the groove center lines in the rolling direction be 1 xvr or more, and be in a direction substantially perpendicular to the rolling direction.If the distance is outside of each range, the effect of reducing iron loss of the material will not be sufficiently obtained. In particular, 30 to 150 μm inside the linear groove.
, depth 10 to 30 μm, spacing in the rolling direction 3 to 20 mm,
When the angle with the rolling direction is 30° or more, there is a large iron loss reduction effect of 0.05 W/kg or more in W17150 value.

Further, the groove must be linear, and the linear shape may be a straight line, a curved line, a wavy line, a broken line, or a dotted line.

Furthermore, the steel plate may be provided with or without a phosphate-based top coating.

(Example) Next, embodiments of the invention will be described.

1. Linear grooves with a width of 100 μm and a depth of 12 μm were introduced at 8 mm intervals in a direction perpendicular to the rolling direction into seven types of cold-rolled silicon-containing steel plates rolled to a thickness of 0.2:3++ m, and the remaining half The product was made into a product using the normal manufacturing process. At this time, the magnetic properties of the grooved steel plate are B1° value 1.91T, W
1?150 value is 0.78W/kg and the steel plate without groove is 1
3to value 1.92T, W17150 value 0.89W/k
It was g.

Next, this steel plate was divided into two, one with linear grooves and one without, and each was slit into a 10-inch wide copper strip.
This was rolled up to a thickness of 40 mm and then press-molded. At this time, adjust the radius of curvature of the innermost bending part of the core to be the various diameters shown in Table 1. Also, for steel plates with linear grooves, the core winding method is such that the linear grooves are inwardly wound. In this case, there were two cases: externally wound.

Furthermore, these cores were heated to 820°C to remove processing strain.
Strain relief annealing was performed in N for 2 hrs.

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

Table 1 As shown in Table 1, the wound core using a steel plate with linear grooves exhibits lower core loss than the wound core using a steel plate without grooves at any bending radius of curvature. For wound cores in which the innermost bending part has a radius of curvature of 30 mm or less, by wrapping the core so that the linear grooves are on the inward winding side, the significant iron loss reduction effect of the material is fully reflected in the core, resulting in even lower core losses. It became possible to manufacture wound cores with low iron loss.

2. Linear grooves of 120 μm in diameter and 15 μm in depth were introduced into a 0.30 mm thick finish-hardened unidirectional magnetic steel sheet coil in the direction perpendicular to the rolling direction, and then this coil was 2 with and without grooves
Divided. At this time, the magnetic properties of the steel plate with grooves introduced are B1
° value, 1.91T, W17150 value 0.92W/kg
The steel plate without grooves has B10 value, 1.92T, W1
7150 value was 1.03 W/kg.

Next, each split coil was slit into a 100*m wide copper strip, which was wound up to a thickness of 401 layers and then press-molded. At this time, adjust the radius of curvature of the innermost bending part of the core to the various diameters shown in Table 2. Also, for steel plates with cotton-like grooves, the method of winding the core is such that the linear grooves are wound inward. In the case of , there were two cases: external winding.

Furthermore, these cores were heated at 850°CX to remove processing distortion.
Strain relief annealing was performed in N for 2 hrs.

Table 2 shows the iron loss characteristics of the core in this case in comparison with the case where a steel plate without linear grooves was used. The radius of curvature of the bent portion indicates the radius of curvature of the innermost bent portion of the core.

Table 2 As shown in Table 2, the wound core using a steel plate with linear grooves showed lower core loss than the wound core using a steel plate without grooves at any bending radius of curvature. By winding the core so that the linear groove is on the inward winding side in a wound core where the innermost bent part has a radius of curvature of 30 dragons or less, the remarkable iron loss reduction effect of the material is fully reflected in the core. It has become possible to manufacture wound cores with lower iron content.

(Effects of the Invention) This invention makes it possible to manufacture a wound core for a transformer with significantly low iron loss, contributing to energy saving.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the formwork for making the core, and Figure 2 is the radius of curvature of the innermost bent part of the core and the iron loss W of the core.
It is a comparative diagram showing the relationship between 1 and 150 (W/kg).

Claims (1)

[Claims] 1. The core is made by winding unidirectional electromagnetic steel sheets with linear grooves formed on one surface, and the linear grooves face the inward winding side, and the radius of curvature of the innermost bent part A wound core for a transformer with low core loss, characterized in that the core is 30 mm or less.