JPS6233728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-phase transformer core having a central leg iron constructed by laminating electrical iron plates to which minute strains are applied for the purpose of reducing iron loss.

Conventionally, this type of iron core has been, for example, as shown in FIG. 1 of the accompanying drawings. That is, in the figure, numerals 1 and 2 are outer leg irons, 3 is center leg iron, 4 and 5 are upper yoke irons, and 6 and 7 are lower yoke irons, which are formed by laminating electrical iron plates cut into a predetermined shape. ing. Here, the solid line indicates the core piece of the top layer, and the dotted line indicates the portion of the next layer that is different from the top layer. Unidirectional silicon steel sheets are generally used as these electrical iron plates, but progress in unidirectional silicon steel sheets has been remarkable, and in recent years,
Furthermore, highly oriented silicon steel sheets with improved orientation in one direction have come into use. Since the highly oriented silicon steel sheet has improved orientation in the rolling direction compared to conventional unidirectional silicon steel sheets, its magnetic properties when magnetized in the rolling direction are improved. However, on the other hand, the magnetic properties in directions deviated from the rolling direction become worse. Therefore, when this highly oriented silicon steel sheet is used in the core of a three-phase transformer, the iron loss of the entire transformer core is lower than when a unidirectional silicon steel sheet is used, but the building factor of iron loss is The drawback was that it became extremely bad. One reason for this is that in the case of a highly oriented silicon steel plate, the distortion of the magnetic flux waveform of the central leg iron 3 is greater than that in a conventional unidirectional silicon steel plate. FIG. 2 shows an example of the magnetic flux waveform of such a central leg iron 3. In the figure, curve a shows the magnetic flux waveform when a highly oriented silicon steel plate is used, and curve b shows the magnetic flux waveform when a conventional unidirectional silicon steel plate is used. Now, when comparing the two, it can be seen that the magnetic flux waveform a when a highly oriented silicon steel plate is used has a shape close to a trapezoid, indicating that the distortion of the magnetic flux waveform is large. This distortion of the magnetic flux waveform is caused by the distortion of the central leg iron 3 when the central leg iron 3 is not excited during three-phase excitation.
This is due to the inflow of magnetic flux into the unidirectional silicon steel sheet, and this tendency is greater in the highly oriented silicon steel sheet than in the conventional unidirectional silicon steel sheet. Figure 3 shows
This is a diagram obtained by analyzing the equivector potential line 8 using the finite element method when the outer leg irons 1 and 2 are energized and the center leg iron 3 is not energized. An inflow of magnetic flux into 3 is observed. Distortion of the magnetic flux waveform increases the eddy current loss component of the iron loss components. Further, 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 also causes a worsening of the iron loss building factor of the highly oriented silicon steel sheet. Next, Figure 4 shows the building graph of iron loss in each leg and yoke of a three-phase transformer core using highly oriented silicon steel sheets and a conventional three-phase transformer core using unidirectional silicon steel sheets. These are the results of analyzing the actor using the finite element method. The upper row of numerical values indicating this building factor is for the case of highly oriented silicon steel sheet, and the lower row is for the case of conventional unidirectional silicon steel sheet. This is shown at the location. Note that this figure shows only the upper half of the three-phase transformer core. In this way, three-phase transformer cores using highly oriented silicon steel sheets have an extremely poor building factor for iron loss in the central leg iron 3, making it impossible to take advantage of the low iron loss characteristics of highly oriented silicon steel sheets. However, it also had the disadvantage of being economically disadvantageous.

The present invention eliminates the conventional drawbacks in three-phase transformers, reduces iron loss, and improves the building factor of iron loss in the central leg iron, thereby creating an energy-saving and cost-saving three-phase transformer. The purpose is to provide a three-phase transformer core that is a phase electromagnetic induction equipment core.

In order to achieve this object, the present invention applies a highly oriented silicon steel plate with high magnetic permeability and low iron loss to the parts of the three-phase transformer core other than the central leg iron, and the central leg iron It is characterized by being constructed by laminating highly oriented silicon steel plates with low magnetic permeability and low iron loss by applying linear minute strain in the direction perpendicular to the other.

The effect of applying this minute strain will be explained next.

Highly oriented silicon steel sheet with linear microstrain does not increase hysteresis loss among iron loss components, but subdivides magnetic domains to reduce eddy current loss, thereby reducing iron loss. There is. In this case, the magnetic permeability is reduced because minute strain is applied. That is, applying strain to a steel plate means that mechanical internal stress remains in the steel plate, resulting in a decrease in magnetic permeability. This decrease in magnetic permeability is
Generally, it is explained that this is due to the formation of a reflux magnetic domain and a reversal magnetic domain, which are formed to relieve the magnetostatic energy due to the demagnetizing field caused by this internal stress.

Therefore, the magnetic permeability decreases for the above reasons, but since it is caused by internal stress, it naturally depends on the interval (physical distance) between the minute strains. If the distance between the microstrains exceeds 10 mm, the magnetic permeability decreases only slightly, but if the distance is about 5 mm, for example, the permeability decreases by about 30%.
In this way, the degree of decrease in magnetic permeability varies depending on the interval between the applied microstrains. Therefore, a highly oriented silicon steel sheet with linear microstrain can be said to be a low iron loss material with reduced magnetic permeability, that is, a material with small eddy current loss.

This is convenient for use in the central leg iron of a three-phase electromagnetic induction equipment core. That is, in the center leg iron, the magnetic flux is distorted due to the intrusion of the magnetic flux when the center leg iron is not excited, but when the magnetic flux is distorted, the eddy current loss in the material increases due to its harmonic components. To prevent this, in order to prevent magnetic flux from entering, the permeability of the central leg iron should be made low, that is, the magnetic resistance should be made large, and even if the magnetic flux waveform is distorted, iron loss will not increase, that is, eddy current loss. It is preferable to use materials with low constituents.

Furthermore, in order to achieve a lower iron loss effect, it is preferable that the iron loss of the original material itself is also low.

The present invention has been constructed in consideration of the above effects and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings showing one embodiment thereof.

FIG. 5 shows an example of a three-phase transformer core in which the central leg iron 11 is constructed by laminating electric iron plates to which a linear minute strain 12 is applied perpendicular to the magnetization direction. This means that when a suitable linear microstrain is applied to a unidirectional silicon steel sheet in the direction perpendicular to the rolling direction, the 180
It is said that iron loss, especially eddy current loss, which is a component of iron loss, is reduced because the magnetic domains are subdivided, and this effect is particularly noticeable in highly oriented silicon steel sheets with large magnetic domain widths. The electric iron plate to which this linear microstrain has been applied is
By laminating and configuring the central leg iron 11 where distorted wave magnetic flux is generated, it is possible to reduce not only eddy current loss due to fundamental wave magnetic flux but also eddy current loss due to harmonic components of distorted wave magnetic flux. be. In addition, due to the linear microstrain applied in the direction perpendicular to the rolling direction (magnetization direction), from the above, if the spacing between the microstrains is set to 5 to 10 mm, the magnetic permeability will decrease by 25%. The inflow of magnetic flux into the center leg iron 11 in a state where the center leg iron 11 is not excited is reduced, and the distortion of the magnetic flux waveform of the center leg iron 11 is alleviated. As a result, the building factor of iron loss in the central leg iron of a three-phase transformer core using a unidirectional silicon steel plate, particularly a highly oriented silicon steel plate, is improved. FIG. 6 shows the calculation results of the building factor of iron loss when the center leg iron 11 is formed by laminating highly oriented silicon steel plates to which linear microstrain is applied. The building factor of iron loss of the center leg iron 11 is improved by approximately 7.5% compared to that constructed from the conventional highly oriented silicon steel plate shown in FIG.

In the above embodiment, the center leg iron 11 of the so-called scrap press iron core is subjected to linear minute strain 12.
Although we have shown an example of a structure made of laminated iron plates with a As in the embodiment shown in the figure, it may be constructed by laminating electric iron plates in which such a linear minute strain 22 is applied to the central leg iron 21. In this case as well, the effect is the same as that of the above embodiment. It is possible to achieve the same effect as.

As described above, according to the present invention, the central leg iron of the three-phase transformer iron core is formed of an electrical iron plate to which minute strain has been applied.
In particular, since the construction is made of laminated highly oriented silicon steel sheets, the building factor of iron loss in the three-phase transformer core is improved, and therefore a transformer with good characteristics can be manufactured economically. , the present invention has.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the core of a conventional three-phase transformer.
Figure 2 is a curve diagram showing the magnetic flux waveform of the central leg iron of the three-phase transformer core in Figure 1, Figure 3 is an equivector potential diagram showing the magnetic flux distribution in the three-phase transformer core in Figure 1, and Figure 4 is an equivector potential diagram showing the magnetic flux distribution in the three-phase transformer core in Figure 1. The figure is an explanatory diagram showing the building factor of iron loss in the three-phase transformer core of Figure 1, Figure 5 is a plan view showing an embodiment of the three-phase transformer core of the present invention, and Figure 6 is the Fig. 5 is an explanatory diagram showing the improved iron loss building factor of the three-phase transformer core, Fig. 7 is a plan view showing another conventional three-phase transformer core, and Fig. 8 shows the present invention compared to the conventional three-phase transformer core. FIG. 8 is a plan view of the three-phase transformer core of FIG. 7; In the figure, 1 and 2 are outer leg irons, 3, 3', 1
1 and 21 are central leg irons, 4 and 5 are upper yoke irons, 6.7 are lower yoke irons, 8 is equal vector potential line, 12,
22 is a linear minute strain.

Claims (1)

[Claims] 1. A three-phase transformer core, characterized in that the central leg iron of the three-phase transformer core is constructed by laminating highly oriented silicon steel plates to which linear microstrain is applied in a direction perpendicular to the rolling direction.