JPS6113608A - Transformer core - Google Patents

Abstract

PURPOSE:To obtain the core having improved magnetic characteristics such as iron loss, an excitation current, noises and the like by a method wherein the core of a core type transformer, having the cross-sectional form of almost D- shape, is formed in such a manner that the core has an integrated structure at the center part in the direction of lamination and the surface part is constituted by assembling a plurality of yokes which are divided in longitudinal direction. CONSTITUTION:The core which constitutes a transformer is composed of a leg 1 and a yoke 2, while a slanting surface of 45 deg. or a protruded part is provided at the end part of said leg and yoke, and they are connected each other at these parts. According to this constitution, the center parts of the leg 1 and the yoke 2 are formed in integral core structure A, and a plurality of yoke structures B divided into longitudinal direction are adhered to the surface of the center part of the structure A. As a result, the length of magnetic path of the surface part of the core becomes short, and iron loss, excitation current, noises and the like are reduced, thereby enabling to obtain an excellent core.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a transformer core, and more particularly to a core for a core-type transformer having a yoke portion having an oval cross-sectional shape.

[Background of the invention]

The core of a transformer is constructed by laminating thin silicon steel plates. For example, in the core of a three-phase tripod internal transformer, the ends of the silicon steel plates are bent at an angle of 45° to 90°, as shown in Figure 4. The structure is such that the steel plates cut into pieces are stacked together while butting them together. This iron core consists of a leg iron 1 around which a winding is wound, and a yoke 2 that connects the leg irons to form a closed magnetic circuit.The cross section of the leg iron 1 is normally shown in Figure 5(a). As shown in the figure, it is structured in a step-like manner inscribed in a circle. This is because since the winding wound around the leg iron 1 is cylindrical, this iron core structure can accommodate the largest amount of iron plates in the winding, making it possible to reduce the size and weight.

On the other hand, the cross-sectional shape of the yoke 2 is not only circular like the leg iron 1, but also has a square structure, but the circular structure causes non-uniformity of magnetic flux because the width of the iron plates of the leg iron and the yoke are equal. To <<,
Although the iron core properties are good, the iron core has the disadvantage of increasing in size and weight.

In addition, in a yoke structure with a rectangular cross section, the width of the steel plate between the leg iron and the yoke is different, resulting in non-uniform magnetic flux in the stacking direction.
Although there is a problem of lowering iron loss characteristics, there is an advantage that the height of the iron core is lower and the weight of the iron core is lighter.

Therefore, in order to take advantage of the advantages of both of these as much as possible, the structure of the nine yoke was designed so that the cross-sectional shape of the yoke resembled the letter D, as shown in Figure 5 (b). There is iron. In this structure, the iron plate width of the leg iron and the yoke are the same, so the iron loss characteristics are good, and the narrow iron plate located on the surface of the yoke moves toward the iron core window, so the leg that is connected to it has good iron loss characteristics. Since the iron is shorter, the weight of the iron core can be lighter than that of a yoke with a circular cross section.

However, in a core with a D-shaped cross-section yoke, as shown in Figure 6, the center line Y-Y of the steel plate width in the surface layer of the yoke moves toward the core window side compared to the center line XX in the inner part. Because we are
The magnetic path length in the surface layer of the iron core is relatively short, and the magnetic flux density is high in this area, which has the disadvantage of increasing iron loss and core vibration. Therefore, as a method to eliminate the above-mentioned drawbacks of an iron core provided with a yoke with a D-shaped cross section, Japanese Patent Application Laid-Open No. 57-5318 discloses a method for improving the surface layer of the iron core so that the magnetic resistance of the surface layer of the iron core and the internal magnetic resistance are almost equal. A configuration using an iron plate with a lower magnetic permeability than other iron plates or a configuration using a thick iron plate has been disclosed, but although both configurations can equalize the magnetic resistance of the iron core, There is a problem in that the iron loss characteristics are lower than when the iron core is made entirely of iron plates. In other words, using an iron plate with low magnetic permeability only in the surface layer of the iron core is equivalent to using an iron plate with poor orientation compared to ordinary silicon steel plates, which causes an increase in iron loss. Furthermore, using a steel plate that is thicker than other plates in the surface layer of the core can be a factor in increasing eddy current loss, so it is expected that cores with a yoke with a D-shaped cross section will improve iron loss characteristics. Can not.

[Purpose of the invention]

An object of the present invention is to provide a transformer core with improved magnetic properties such as iron loss, exciting current, and noise.

[Summary of the invention]

The key point of the present invention is that in a transformer core having a yoke with a D-shaped cross section that is convex to the outside of the core window, the yoke part that is joined to the leg iron at an angle of approximately 45° is not divided inside the core in the lamination direction. In contrast to the integrated structure, the surface layer part is divided in the longitudinal direction.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to a cross-sectional view of a leg iron and a yoke of a transformer core in FIG. 1 and a plan view of a three-phase tripod core in FIG. 2.

Fig. 1 (a) is a cross-sectional view of the leg iron, and ) in Fig. 1 is a cross-sectional view of the yoke.
FIG. 2(a) shows a method of joining inside a core with wide steel plates, and FIG. 2(a) shows a method of joining at a surface layer of the core.

As shown in Figure 2(a), the planar joint structure inside the core, indicated by section 0 in Figure 1, has a one-piece yoke 2a with a V-shaped notch, and is joined to the leg iron 1 at approximately 45 degrees. In contrast, in the surface layer of the horse in Figure 1, the yoke is divided into two parts 2b and 2C at an angle of approximately 45°, as shown in Figure 2), and the surface layer of the iron core is relatively The area where the steel plates butt at the same time increases.

In this configuration, so that the joint between the leg iron 1 and the yoke 2 can take full advantage of the orientation of the iron core in all parts of the iron core, the
The yoke is divided at the surface layer of the core where the magnetic path length is relatively short, and the range of butt of the iron plates is increased, so the magnetic resistance at the surface layer of the core increases. increases, and the conventional problem of shortening the magnetic path length and increasing magnetic flux density in the surface layer of the iron core can be solved.

Moreover, in order to alleviate the concentration of magnetic flux density in the surface layer of the conventional iron core, it is not necessary to use materials with poor iron loss characteristics such as materials with low magnetic permeability or thick materials. Various properties such as core loss, exciting current, and noise can be significantly improved.

There is a concern about the difference in magnetic properties between the joining method shown in Figure 2 (a) applied inside the core and the joining method shown in Figure 2 (in Figure 2) applied to the surface layer of the core, but the inventors' experiments According to
~40 inches larger, without increasing iron loss,
It is effective in that it can increase the magnetic resistance of the surface layer of the iron core and make the magnetic flux density uniform.

FIG. 3 shows another embodiment of the present invention, showing the same parts as FIG. ) are shown respectively. In this configuration, the yoke on the surface layer shown in (b) is 45 degrees and 9 degrees.
Although it has a 0' end face and is divided, this division only works to increase the magnetic resistance of the surface layer and does not impair the iron loss characteristics. It is no different from what was stated above.

In addition, in the above-mentioned embodiment, if the range of the surface layer of the core where the yoke is divided is t on both sides as shown in Fig. 1, then from the viewpoint of the performance of the core, this t is equal to the total width of the core in the stacking direction. It is desirable to set it to about 5 to 15%.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a leg iron and a yoke showing an embodiment of the present invention;
FIG. 2 is a plan view showing the joining method at each part of the core of the present invention;
Fig. 3 is a plan view showing the joining method of each part of the core showing another embodiment of the present invention, Fig. 4 is a front view of the core of an inner iron type three-phase transformer, and Figs. 5 and 6 are the conventional D They are a cross-sectional view and a plan view, respectively, showing problems with a transformer core having a yoke with a shaped cross section. 1... Leg iron, 2+ 2a, 2b, 2 (+++ yoke.

Claims (1)

[Scope of Claims] 1. In a transformer core comprising a combination of a leg iron part and a yoke part that is convex outward from the core, an integral yoke that is not divided near the center in the stacking direction of the core, and . A transformer core, characterized in that a plurality of longitudinally divided yokes are laminated and combined together in the vicinity of the surface layer of the core.