JPH03204911A - Transformer core - Google Patents

Abstract

PURPOSE:To make it possible to constitute a low-noise transformer core without lowering magnetic characteristics by a method wherein a core consisting of grain-oriented silicon steel plates is arranged in the center part, another core, consisting of a material having magnetostriction lower than the grain-oriented silicon steel plate, is arranged on both sides of the above-mentioned core, both sides are integrally formed, and the cross-sectional area of the core of low magnetostriction material is specifically prescribed. CONSTITUTION:Picture frame-shaped laminated cores 11, which are formed by cutting a grain-oriented silicon steel plates 11a at an angle of 45 deg., are arranged in the center part in the direction of lamination, another laminated picture frame-shaped cores 12, which are formed by cutting a low magnetostriction 6.5% silicon steel plate 12a at an angle of 90 deg., are arranged in almost same cross-sectional area, and a core 10 is constituted by combining the above-mentioned cores in one body. In this case, the cross-sectional area of the laminated core 12 of 6.5% silicon steel plate 12a should be 10 to 50% of the entire cross-sectional area of the composite core 10. In the transformer core having the above-mentioned constitution, the deterioration in B-H characteristics on the high magnetic flux density region in commercial frequency, which is the defect of 6.5% silicon steel plate 12a, can be improved and, besides, its iron loss becomes better than the core made of 6.5% silicon steel plate 11a only.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a transformer core used for inverter power supplies and the like.

(Prior art) In recent years, 6.5% silicon steel sheets, which have low magnetostriction and excellent magnetic properties, have been used instead of the conventional 3% grain-oriented silicon steel sheets for iron cores used in induction equipment such as transformers. This is being considered.

It has been known for a long time that this 6.5% silicon steel sheet has almost zero magnetostriction and low iron loss, but as the silicon content increases, it becomes brittle, making rolling technology difficult. . However, recently, with improvements in rolling technology for brittle materials and advances in CVD methods, this 6.5% silicon steel sheet has been developed.

This 6.5% silicon steel plate has a magnetostriction of 0.3×10-'
Although it is an advantageous material for reducing noise in transformers, it has the disadvantage that the excitation current increases in commercial frequency equipment due to poor B-H characteristics in high magnetic flux density regions. Also,
Improving the B-H characteristics in a high magnetic flux density region has the problem of increasing iron loss.

For this reason, in commercial frequency transformers, the conventional silicon content is 3%.
It was necessary to design the magnetic flux density to be lower than that of grain-oriented silicon steel sheets, which was a bottleneck in making equipment smaller and lighter.

On the other hand, with recent advances in electronics technology, the number of devices using inverter power supplies, such as UPS power supplies, has increased significantly. This transformer for an inverter power supply has a fundamental wave component of 50 to 60 Hz, and contains harmonics of several kHz to several kHz depending on the switching element, so that noise from the device is a problem.

Conventionally, this inverter power supply transformer has been constructed by cutting a wound core 2 wound with a grain-oriented silicon steel plate 1 and combining it with a coil 3, as shown in FIG.

(Problems to be Solved by the Invention) However, in a wound core transformer using grain-oriented silicon steel sheets, the magnetostriction of the grain-oriented silicon steel sheets is as large as approximately 2×10 to 6 in the magnetic flux density range used, which is large compared to the inverter. There was a problem of increased noise due to harmonics caused by the switching frequency.

In particular, recently there has been a trend to install UPS power supplies indoors, so there has been a demand for noise reduction.

The present invention has been made to satisfy the above-mentioned needs.
The purpose of the present invention is to provide a transformer core suitable for use in inverter power supplies, etc., which can be configured to have low noise without reducing magnetic properties.

[Structure of the Invention] (Means and Effects for Solving the Problems) The transformer core of the present invention has a core made of grain-oriented silicon steel plate disposed in the center, and 6.5% silicon steel plates, for example, placed on both sides of the core. A combination core is used, in which a core made of a low magnetostrictive material such as
The cross-sectional area of the core made of low magnetostrictive material is 10 to 50 of the total core cross-sectional area.
%.

In such an iron core configuration, for example, most of the magnetic flux components of 50 Hz and 60 Hz, which are the fundamental wave components of the inverter power supply, flow through the grain-oriented silicon steel plate, which has high magnetic permeability in this frequency range.
Most of the harmonic components of 2 to 5 kHz due to switching will flow through the low magnetostrictive material with high magnetic permeability in this frequency range.

Figures 2 and 3 show a comparison of the characteristics of iron loss and excitation capacity of an iron core using a 6.5% silicon steel plate as a low magnetostrictive material and an iron core using a grain-oriented silicon steel plate.

As is clear from this figure, at a frequency of 50Hz, iron loss
The 6.5% silicon steel core is worse in terms of excitation capacity, especially the excitation capacity when the magnetic flux density is 1.5%. It has deteriorated more rapidly than in the area beyond OT. However, as the frequency increases, the difference in characteristics becomes smaller (at 400 Hz, both cores have almost the same characteristics, and at higher frequencies, the 6.5% silicon steel core has better characteristics in terms of iron loss and excitation capacity). show.

This is because the specific resistance of the 6.5% silicon steel sheet is greater than that of the grain-oriented silicon steel sheet, so at high frequencies, the eddy current flow decreases and the magnetic permeability increases.

Note that the combined characteristics of both cores show approximately the average characteristics of each core.

On the other hand, as shown in Figure 4, the noise characteristics of the 6.5% silicon steel core are lower than those of the grain-oriented silicon steel core over the entire frequency range, and as the frequency increases, both cores There is a larger difference in the noise values.

That is, for example, in an inverter power supply transformer, 501
(Since the magnetic flux waveform contains harmonics of several kHz in addition to the fundamental wave of 60 Hz or They discovered that by adopting an iron core configuration, it is possible to suppress deterioration of magnetic properties and significantly reduce noise.

In this case, by interposing a buffer material between the iron core made of grain-oriented silicon steel plate and the iron core made of low magnetostrictive material, frictional noise due to the difference in porcelain distortion characteristics between the two can also be reduced.

(Example) An example of the present invention will be described using FIGS. 1(a) and (b). In the figure, the grain-oriented silicon steel plate 11a is
A frame-shaped laminated iron core 11 that has been cut and laminated is arranged at the center in the lamination direction, and on both sides thereof are 6 and 5 layers made of a low magnetostrictive material.
% silicon steel plates 12a are cut at 90° and laminated to form a combination core 10 in which strip-shaped laminated cores 12 are arranged with approximately the same cross-sectional area, and each laminated core is integrated.

In this case, the stacked core 12 of 6.5% silicon steel plates 12a placed on both sides accounts for 10 to 50% of the total cross-sectional area of the combined core 10.
I have to.

Although the coils are not shown, they are wound and inserted into the core legs.

In the transformer core with such a configuration, the grain-oriented silicon steel plate 11a is used at a ratio of more than half (50 to 90%) of the total cross-sectional area of the combination core 10, so 6.5% silicon is used. The deterioration of B-H characteristics in the high magnetic flux density region at commercial frequencies, which is a drawback of the steel plate 12a, can be improved, and the iron loss is also improved by 6.5% compared to the iron core made of the silicon steel plate 11a alone.

This is because by using the combination core 10, most of the magnetic flux flows through the grain-oriented silicon steel plate 11a, which has high magnetic permeability in the commercial frequency range.

On the other hand, regarding harmonic components (approximately 2 to 5 kHz) due to the switching frequency of the inverter, most of the magnetic flux components flow through the 6.5% silicon steel plate 12a, which has high magnetic permeability in the high frequency range, and Exhibits excellent magnetic properties for power supplies.

Regarding noise, noise increase due to high frequencies is a particular problem, but the magnetostriction of the 6.5% silicon steel plate 12a is 0.3X1.
It is about 0-6, and about 2×1 of the grain-oriented silicon steel plate 11a.
Compared to 0-6, it is very small at about 1×10, so noise can be significantly reduced.

Table 1 shows the case where the ratio of 6.5% silicon steel sheet to the total core cross-sectional area is 5%, 10%, 30%, and 50%, and the case where the ratio is 50% and the core made of grain-oriented silicon steel sheet. 6.
When a cushioning material such as a rubber sheet with a thickness of about 1 inch is interposed between the iron core made of 5% silicon steel plate, and only grain-oriented silicon steel plate and 6.5% silicon steel plate only. The noise characteristics of the inverter power supply transformer are shown below.

(Leaving space below) Table 1 Noise of transformer for inverter power supply From Table 1, the noise of the transformer for inverter power supply is as follows: It can be seen that when the ratio of 6.5% silicon steel plate to the area is 10 to 50%), the magnetic flux density is reduced by 5 to 8 dB at 1.5T. Furthermore, it can be seen that the core configuration with a buffer material interposed therein provides a further reduction of several dB compared to the core configuration without a buffer material.

On the other hand, when the ratio of the 6.5% silicon steel plate to the total core cross-sectional area is 5%, the noise reduction effect is small. In addition,
If the ratio of 6.5% silicon steel plate 12a to the total core cross-sectional area is 50%, the noise is almost the same as that of a core with only 6.5% silicon steel plate 12a, so 6.5% more
Even if the proportion of the silicon steel plate 12a is increased, the noise reduction effect is small, and on the contrary, magnetic properties such as iron loss and excitation current deteriorate, which is not preferable.

In the above embodiment, the laminated iron core 1 of 6.5% silicon steel plate 12a is
2 are placed on both sides of the laminated iron core 11 of the grain-oriented silicon steel plates 11a, but this is because the silicon steel plates 12 with a small magnetostriction of 6.5% L% are placed on both sides in the core lamination direction where the radiation surface for noise generation is large.
This is to obtain a greater noise reduction effect by arranging the iron core 12 of a.

In this way, by making the core 10 a combination of the grain-oriented silicon steel plate 11a and the 6.5% silicon steel plate 12a, it is possible to reduce deterioration of magnetic properties and obtain a transformer core for an inverter power supply with very low noise. I can do it.

In this inverter power supply transformer core, grain-oriented silicon steel plate 1
The composite core 10 is constructed by combining a frame-shaped stacked core 11 using 1a and a strip-shaped stacked core 12 using a 6°5% silicon steel plate 12a, but the present invention is not limited to this. Considering the sacrifice, both core materials are 90″
It is also possible to construct a cut rectangular stacked core by combining these.

Also, grain-oriented silicon steel plate 11a constituting the combination core 10
It is also possible to use a wound core structure instead of the frame-shaped stacked core 11.

Furthermore, the same effect as described above can be obtained even if both core materials are configured as a wound core structure.

Further, the present invention is not limited to inverter power supply transformers, but can also be applied to iron cores of high-frequency transformers to obtain similar effects.

[Effects of the Invention] As explained above, according to the transformer core according to the present invention, it is possible to improve the deterioration of the B-H characteristics in the high magnetic flux density region of the low magnetostrictive material and to significantly reduce noise. .

[Brief explanation of drawings]

FIGS. 1(a) and (b) are exploded perspective views and assembled perspective views showing the transformer core of the present invention, and FIG. 2 is an iron core using a 6.5% silicon steel plate and a grain-oriented silicon steel plate. Figure 3 is an explanatory diagram showing a comparison of iron loss characteristics of iron cores using 6.5% silicon steel plate and grain-oriented silicon steel plate. FIG. 5, which is an explanatory diagram showing a comparison of noise between iron cores using silicon steel plates and grain-oriented silicon steel plates, is a front view showing a conventional transformer for an inverter power supply. 10...Combination core, 11...Picture frame-shaped stacked core, 1
1a... Grain-oriented silicon steel plate, 12... Strip-shaped stacked iron core, 12a... 6.5% silicon steel plate (low magnetostrictive material).

Claims (2)

[Claims] (1) An iron core made of a grain-oriented silicon steel sheet is placed in the center, and iron cores made of a material with lower magnetostriction than the grain-oriented silicon steel sheet are placed on both sides of the iron core, and both iron cores are made of a material with low magnetostriction. The cross-sectional area of the core is 10 to 50% of the total core cross-sectional area.
A transformer core characterized by the following. (2) The transformer core according to claim 1, characterized in that a buffer material is interposed between the core made of a grain-oriented silicon steel plate and the core made of a low magnetostrictive material.