JPS63110711A - Iron core of transformer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

[Conventional technology]

The core of a transformer is composed of laminated thin silicon steel plates. For example, in the core of a three-phase three-leg internal iron transformer, the ends of the silicon steel plates are cut into approximately 45" pieces, as shown in Figure 4. A structure is adopted in which iron plates are stacked alternately while butting against each other.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 configured in a double-step shape inscribed in a circle as shown in Fig. 5(a).This is because the winding wire wound around the leg iron 1 is cylindrical. This is because this iron core structure can accommodate the largest amount of iron plates in the winding, making it possible to make it smaller and lighter.On the other hand, the cross-sectional shape of the yoke 2 is not only circular like the leg iron 1 but also A square structure is used, but the former circular structure has the same width as the iron plate of the leg iron and yoke, so it is less likely to cause uneven magnetic flux and has good core characteristics, but has the disadvantage that the iron core becomes larger and the weight increases. A yoke structure with a rectangular cross section has the advantage of lower core height and lighter core weight, but because the widths of the steel plates of the legs and yoke are different, the magnetic flux increases in the lamination direction. There is a problem that this causes non-uniformity and increases iron loss characteristics.A yoke structure that takes advantage of both of these advantages is shown in Fig. 5 (b).
There is a so-called D-shaped cross-sectional yoke, which has a cross-sectional shape similar to the letter D, as shown in the figure. This structure has good iron loss characteristics because the steel plate widths of the leg iron and yoke are equal.

Since the narrow steel plate located on the surface of the yoke moves inward to the core window, the leg irons connected to it can be shortened, making the core lighter than a yoke with a circular cross section. There are features that allow it. However, in the core configuration with such a D-shaped cross-section yoke, as shown in Fig. 6, the center line Y-Y of the iron plate width at the surface layer of the yoke moves toward the core window side compared to the center line x-x of the inner side. Therefore, the length of the magnetic path in the surface layer of the core is relatively short. Therefore, as a method for eliminating the above-mentioned drawbacks of a core having a yoke with a D-shaped cross section, Japanese Patent Application Laid-Open No. 57-53113 discloses In order to make the magnetic resistance of the surface layer of the core almost equal to the magnetic resistance inside the core, configurations have been disclosed in which the iron plate in the surface layer of the core is made of an iron plate with lower magnetic permeability than other iron plates, or a steel plate with a thicker plate thickness is used. In either configuration, the magnetic resistance of the core can be made uniform, but there is a problem in that the core loss characteristics are lowered compared to when the core is all made of iron plates made of the same material. Using an iron plate with a small . Furthermore, the use of thicker steel plates in the surface layer of the core can increase eddy current loss, so implementing these techniques alone will not allow the core to have a yoke with a D-shaped cross section. It cannot be expected that the iron loss characteristics will be sufficiently improved.

[Problem that the invention seeks to solve]

The above conventional technology partially uses materials with low magnetic permeability or thick materials in order to make magnetic resistance approximately equal, but the problem is that iron loss cannot be reduced compared to when the core is made of iron plates made of the same material. was there.

An object of the present invention is to provide a transformer core that improves magnetic properties by increasing the effective cross-sectional area at the core joint so that iron loss does not increase even if the magnetic flux density at the yoke becomes uneven. It is in.

[Means for solving problems]

The above object is achieved by step-lapping the iron core joint where the yoke having a D-shaped cross section is significantly affected by non-uniform magnetic flux, thereby increasing the effective cross-sectional area and reducing the cross-over magnetic flux density at the joint.

[Effect]

At core joints where large inhomogeneity of magnetic flux occurs in yoke parts with a D-shaped cross section, the number of step laps is increased from the center of the core to the surface layer so that the effective cross-sectional area in the lamination direction increases. Reduces the flux density at the core joint and reduces iron loss.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 is a cross-sectional view of the transformer core, with (a) showing the leg iron and (b) showing the yoke. Figure 2 shows the core joint between leg iron 1 and yoke 2 in Figure 1, and (a) in the figure is a cross-sectional view of A block (b), B block (Q), and C block in Figure 1. The structure has a structure in which the number of step wraps is changed from 1 to 3 to 5 in order to increase the effective cross-sectional area in the lamination direction toward the surface layer of the core.

According to this construction method, the magnetic flux density becomes higher in the surface layer of the iron core, which increases iron loss, but as shown in FIG.
~ As shown in (Q), the joining position is shifted in a stepwise manner in the stacking direction, so the crossover magnetic flux density at the joint is relaxed, reducing iron loss in this area and significantly reducing various characteristics such as excitation current and noise. It becomes possible to improve the In carrying out the present invention, the leg iron 1 and the yoke are arranged in such a way that the notch does not increase at the joint between the leg iron 1 and the yoke 2 even if the step wrap method is changed so that the effective cross-sectional area increases. It is desirable that the total overlapping margin of 2 is approximately constant.

Another embodiment shown in FIG. 3 shows the same part as FIG. 2, and the iron plate of the yoke 2 shown by diagonal lines in the figure, where the magnetic flux density is non-uniform, is more oriented than the iron plate used for the leg iron 1. Examples are shown of materials that reduce the loss of the iron plate itself without changing its properties, such as thin plate materials and laser-treated materials. By using this material, in addition to the effect of increasing the effective cross-sectional area, it is possible to further reduce loss.

〔Effect of the invention〕

According to the present invention, the step-wrap method is changed so that the effective cross-sectional area increases as the magnetic flux density increases in the surface layer of the D-type yoke, and the magnetic flux is relaxed at the core joint.

It has the effect of reducing iron loss, exciting current, noise, etc.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a leg iron and a yoke showing an embodiment of the present invention;
Fig. 2 is a cross-sectional view showing the step-lap method in the lamination direction in the joint structure of the leg iron and yoke of the present invention, and Fig. 3 is another embodiment of the present invention in which the yoke is made of low-loss material. Figure 4 is a plan view showing the conventional core joining method, Figure 5 is a cross-sectional view of the conventional leg iron and yoke, and Figures 6 and 7 are the iron core showing the problems with the conventional method. FIG. 2 is a plan view and an explanatory diagram of magnetic flux density distribution in the direction of the intermediate layer of the yoke. 1.2...leg iron, 3,4...yoke.

Claims (1)

[Claims] 1. In a transformer core formed by combining a leg iron having a substantially circular cross-sectional shape and a yoke having a cross-sectional shape convex to the outside of the core window and having approximately the same iron plate width as the leg iron, the iron core A transformer core characterized in that the number of step wraps is changed so that the effective cross-sectional area in the lamination direction at the core joint increases as the surface layer increases.