JPH03236204A - Iron core for three-phase transformer - Google Patents

Abstract

PURPOSE:To reduce the curved intrusion of magnetic flux into a central leg part and to improve magnetic characteristics such as iron loss by using a 6.5% silicon steel plate whose magnetostriction is smaller than that of a directional silicon steel plate only for the central leg part. CONSTITUTION:A 6.5% silicon steel plate is used only for a central leg part 12. One-directional or highly oriented silicon steel plates which are used in conventional apparatuses are employed for other both side-leg parts 1 and 1 and upper and lower yoke parts 3 an 4. Since the 6.5% silicon steel plate of the central leg part 12 is nondirectional, it is not necessary to consider directivity. When the plate is formed in a strip shape, the plate can be readily cut. Meanwhile, a batten plate whose both ends are cut at 45 deg. is used for the side leg parts 1 and 1. A batten plate whose one side is cut at 45 deg. and other side is cut at 90 deg. is used for the upper and lower yoke parts 3 and 4. Thus the characteristics of the directional silicon steel plates are utilized. The iron core of this transformer is constituted by appropriately laminating the above described punched plates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an iron core for a three-phase transformer that reduces iron loss.

(Prior Art) Conventionally, grain-oriented silicon steel plates have been mainly used as materials for iron cores for three-phase transformers. As shown in Fig. 3, its structure consists of both side legs 1, 1, center leg 2, and upper and lower yoke parts 3, 4, and is formed by laminating silicon steel plates cut into a predetermined shape. .

However, in recent years, highly oriented silicon steel sheets with enhanced unidirectional orientation have also come into use. When such a highly oriented silicon steel sheet is used in a three-phase transformer core, as described in Japanese Patent Application Laid-Open No. 57-194507,
Although the iron loss of the entire transformer core is lower than that of unidirectional silicon steel sheets, it has the disadvantage that the building factor (transformer iron loss/material iron loss) when the transformer is assembled becomes extremely poor. One reason for this is said to be that in the case of a highly oriented silicon steel plate, the distortion of the magnetic flux waveform in the central leg portion 2 is greater than that in a conventional unidirectional silicon steel plate.

The distortion of the magnetic flux waveform is caused by the inflow of magnetic flux into the central leg 2 when the central leg 2 is not excited during three-phase excitation, and has a higher orientation than conventional unidirectional silicon steel sheets. It is shown that this tendency is greater for silicon steel sheets. FIG. 4 is a diagram obtained by analyzing the equipotential diagram of magnetic flux at the T-junction of a transformer constructed using the conventional method using the finite element method, in which both legs 1.1 are energized and the center A state in which the leg portion 2 is not excited is shown. According to this, a large amount of magnetic flux flows into the central leg 2, and the distortion of the magnetic flux waveform becomes particularly large in the central leg 2. Eddy current loss is expressed as 05F2 in a grain-oriented silicon steel plate, where F is waveform distortion, and as is clear from this, waveform distortion increases the eddy current loss component. Furthermore, in the case of a highly oriented silicon steel sheet, the magnetic domain width is larger than that of a conventional unidirectional silicon steel sheet, so that the eddy current loss accounts for a large proportion of the total iron loss. This is also a cause of worsening the core loss building factor of highly oriented silicon steel sheets.

(Problems to be Solved by the Invention) As mentioned above, if the core structure of a three-phase transformer is made of unidirectional or highly oriented grain-oriented silicon steel plates as shown in FIG. In the case of Wl-90°, the amount of magnetic flux going around to the central leg increased as shown in FIG. 4, and the eddy current loss tended to increase. If the eddy current loss increases, the iron loss as a transformer will increase.
There were problems such as poor magnetic properties.

The present invention has been made to solve the above problems,
The purpose is to provide an iron core for a three-phase transformer that has improved magnetic properties such as iron loss by reducing the circulation of magnetic flux into the central leg.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the core for a three-phase transformer of the present invention has a central leg made of 6.
．． It is characterized in that 5% silicon steel plates are arranged and grain-oriented silicon steel plates are arranged and laminated on both side leg parts and yoke parts.

(Function) According to the core for a three-phase transformer of the present invention, only the center leg uses a 6.5% silicon steel plate that has less magnetostriction than a grain-oriented silicon steel plate, so there is less magnetic flux going around to the center leg. This reduces waveform distortion. This reduces eddy current loss, thereby reducing the core loss of the transformer.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front view of one embodiment of the present invention, and as shown in the same figure, only the center leg 12 is made of 6.5% silicon steel plate, and the other side legs 1, 1 and the upper and lower yoke parts are made of 6.5% silicon steel plate. 3.4 uses a conventionally used unidirectional or highly oriented grain-oriented silicon steel plate.

In addition, although the example shows a case in which the center leg portion 12 is constructed using a strip-shaped punched plate, this is because the 6° 5% silicon steel plate is non-directional, so there is no need to consider the directionality. This is because it is good and the strip shape is easier to cut. On the other hand, for the side legs 1, 1, a punched board with both ends cut at 45° is used, and for the upper and lower yoke parts 3.4, one is cut at 45° and the other is cut at 90°.
Utilizing the characteristics of grain-oriented silicon steel sheets by using 0'-cut blanks. The transformer core is constructed by appropriately laminating the above-mentioned punched plates, but the size, stacking thickness, etc. of the core are the same as conventional ones and there is no particular change.

As mentioned above, according to this embodiment, since the 6.5% silicon steel plate is used only for the central leg 12, the magnetic flux wraps around (see Fig. 4), which shows the magnetic flux distribution in the conventional iron core structure. ) will decrease. This is because the 6.5% silicon steel plate is non-directional, so the magnetic flux flows in the direction of smaller magnetic resistance, that is, the direction where the length of the magnetic path is the shortest. This is because there will be less.

FIG. 2 shows the magnetic flux distribution due to the iron core configuration of this embodiment, and it can be seen that the magnetic flux flowing around to the central leg portion I2 is smaller than in FIG. 4.

Table 1 shows the iron loss, building factor, and
This shows the loss ratio. In this table, the circuit configuration of the iron core is compared with ■ one made of highly oriented silicon steel plate, ■ one made of unidirectional silicon steel plate, and ■ only the central leg section is 6.5.
% silicon steel plate is shown.

From Table 1, it can be seen that the transformer using 6.5% silicon steel plate only for the central leg (■) has a lower total iron loss than the transformer (■) using highly oriented silicon steel plate for all parts, and the building factor has decreased significantly.

Table 1 In the above embodiment, the core structure shown in FIG. 1 was explained, but the scrapless core structure using the conventional 45° cutting plate shown in FIG. %
Even if a silicon steel plate is used, the same effects as in the above embodiment can be obtained. It goes without saying that similar effects can be obtained with a V-notch miter core.

"Effects of the Invention" As explained above, according to the present invention, the magnetic flux that wraps around the center leg is reduced and waveform distortion is reduced, so iron loss is reduced and the three-phase We can provide transformer core. In addition, 6.5% silicon steel sheet has a small magnetostriction of less than 1/3 of that of grain-oriented silicon steel sheet, so using 6.5% silicon steel sheet for the center leg, which has large waveform distortion, which contains many high frequency components, This also has the effect of reducing noise.

[Brief explanation of drawings]

Fig. 1 is a front view of one embodiment of the present invention, Fig. 2 is an equivector potential diagram showing the magnetic flux distribution at the T-junction of the three-phase transformer core shown in Fig. 1, and Fig. 3 is a conventional highly oriented FIG. 4 is an equivector potential diagram showing the magnetic flux distribution at the T-junction of the three-phase transformer core shown in FIG. 3. 1...Side legs 2...Central legs 3.4...Upper and lower yoke (8733) Agent: Patent attorney Yoshiaki Inomata (and others)
1 person) Figure 3 Figure 4 Figure 2

Claims (1)

[Claims] 6.5 with lower magnetostriction than grain-oriented silicon steel plate in the center leg
An iron core for a three-phase transformer, characterized in that % silicon steel plates are arranged and grain-oriented silicon steel plates are arranged and laminated on both side legs and yoke parts.