JPH03268311A - Iron core of transformer - Google Patents

Abstract

PURPOSE:To remarkably reduce noise by a method wherein, on the outside of a wound core formed by winding a grain oriented silicon steel strip, magnetic material whose magnetostriction is lower than that of said strip is wound so as to constitute a combined iron core, and the sectional area of the magnetic material of low magnetostriction is made equal to 10-50% of the sectional area of the total iron core. CONSTITUTION:A wound core 11a formed by winding a grain oriented silicon steel strip 11a is arranged on the inside part; magnetic material 12a of low magnetostriction is wound around the outside of the wound core 11a so as to constitute a combined iron core, the sectional area of the iron core formed by winding the magnetic material 12a is made equal to 10-50% of the sectional area of the total iron core. Hence, in a magnetic flux waveform wherein a fundamental wave contains higher harmonics, the greater part of the fundamental wave component is loaded on the grain oriented silicon steel strip, and higher harmonic components are loaded on the magnetic material of low magnetostriction, thereby restraining the degradation of magnetic characteristics. Hence a low noise transformer iron core can be obtained without deteriorating magnetic characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a transformer core used in an inverter power supply and the like having low loss and low noise characteristics.

(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 and put into practical use.

This 6.5% silicon steel plate has a magnetostriction of 0.3×10-6
This makes it an advantageous material for reducing noise in transformers; however, it has the disadvantage of increasing excitation current in commercial frequency equipment due to poor B-H characteristics in high magnetic flux density regions. Furthermore, there is a problem in that improving the B-H characteristics in a high magnetic flux density region increases 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 inverter power supply transformer generally has a fundamental wave component of 50
~60Hz, and several kHz depending on the switching element
Because it contains harmonics of ~10-odd kHz, equipment noise is a problem.

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

(Problem to be solved by the invention) However, in a wound core transformer using a grain-oriented silicon steel plate, the magnetostriction of the grain-oriented silicon steel plate is as large as approximately 2X10-6 in the magnetic flux density region used, and is highly adjustable due to the switching frequency of the inverter. There was a problem with the noise caused by the waves.

In particular, there is a recent trend to install UPS power supplies indoors, so noise reduction has been desired.

The present invention was made to reduce the above-mentioned noise,
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 characteristics.

[Structure of the Invention] (Means for Solving the Problems) The transformer core of the present invention has a wound core in which grain-oriented silicon steel plates are wound, and a 6.5% silicon steel plate on the outside thereof. It is characterized in that a combination core is made by winding a low magnetostrictive magnetic material such as, and the cross-sectional area of the core made of the low magnetostrictive magnetic material is 10 to 50% of the total core cross-sectional area.

With this type of core configuration, even if a material such as 6.5% silicon steel plate cannot be wound with a small curvature below the bending curvature, which is brittle, the corner part can be easily wrapped by the wound core made of grain-oriented silicon steel plate wound on the inner part. Since the winding curvature is increased, a low magnetostrictive magnetic material can be easily wound thereon.

On the other hand, when such a wound core is applied to, for example, an inverter power supply transformer, the fundamental wave component of 50 Hz or 6
Most of the magnetic flux component at 0Hz flows through grain-oriented silicon steel sheets with high magnetic permeability in this frequency range, and 2 to 10
As for the harmonic components of kHz, most of them will flow to a low magnetostrictive magnetic material such as 6.5% silicon steel plate, which has 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 magnetic 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 plate iron core is worse in terms of excitation capacity, and in particular, the excitation capacity deteriorates rapidly in the region where the magnetic flux density exceeds 1.0T. However, as the frequency increases, the difference in characteristics becomes smaller, and at 400Hz, both cores have almost the same characteristics, and at higher frequencies, the 6.5% silicon steel sheet has better characteristics in terms of iron loss and excitation capacity. It shows.

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 that at high frequencies, the thin current loss decreases and the magnetic permeability increases. Note that the combined characteristics of both cores are 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 sheet core are lower than those of the grain-oriented silicon steel sheet iron core in all frequency ranges, and as the frequency increases, the noise characteristics of both iron sheets decrease. The difference in noise values is even greater.

That is, for example, in an inverter power supply transformer, 50H
Since the magnetic flux waveform contains harmonics of several kHz in addition to the fundamental wave of 60 Hz or 60 Hz, the fundamental wave component is mostly absorbed by grain-oriented silicon steel sheet, and the harmonic component is absorbed by 6.5% silicon steel sheet. They discovered that by configuring the core to be supported by a low magnetostrictive magnetic material, it is possible to suppress deterioration of magnetic properties and significantly reduce noise.

In addition, by arranging the wound core made of low magnetostrictive magnetic material in the outer part as in this core configuration, the low magnetostrictive magnetic material is placed in the large part of the radiation surface where noise is generated, resulting in an even lower noise effect. There are some characteristics that make it bigger.

(Example) An embodiment of the present invention will be described with reference to FIG.

In the figure, a hoop-shaped grain-oriented silicon steel plate 11a is wound inside to a certain thickness to form a wound core 11. Next, a hoop-shaped 6 made of a low magnetostrictive magnetic material is placed on top of this wound core 11.
．． A wound core 12 is formed by winding a 5% silicon steel plate 12a to a specified stacking thickness, and a combined core 13 including both cores is constructed.

In this case, the cross-sectional area of the wound core 12 made of the 6.5% silicon steel plate 12a placed on the outside is 1 of the total cross-sectional area of the combined core 13.
It is set to 0-50%. The combined core 13 may be constructed by separately winding the grain-oriented silicon steel-wound core 11 and the 6°5% silicon steel-wound core and combining them later. Although not shown, the combined iron core 13 is a C-cut core that is formed immediately after formation because it is inserted into each of the iron core legs. Note that this combination core 13 may also be a one-turn cut core having a cut portion for each steel plate.

In a 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 combined core 13, so 6.5% silicon steel plate is used. It is possible to improve the deterioration of B-H characteristics in the high magnetic flux density region at commercial frequencies, which is a drawback of 12a, and the iron loss is also better than that of the core made of 6.5% silicon steel plate 11a alone.

This is because by using the combination core 13, 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 10 kHz) caused by switching frequencies such as inverters, most of the magnetic flux components flow through the 6.5% silicon steel 12a, which has high magnetic permeability in the high frequency range, and the inverter power transformer It exhibits excellent magnetic properties.

Regarding noise, noise increase due to harmonics is a particular problem, but the magnetostriction of the 6.5% silicon steel plate 12a is 0.3X10
-6, and about 2×10 of the grain-oriented silicon steel plate 11a.
-', it is very small at about 1×10, so noise can be significantly reduced.

Table 1 shows the noise characteristics of the inverter power transformer.

Table 1 Noise of transformer for inverter power supply From Table 1, the noise of the transformer for inverter power supply is as follows: The noise of the transformer for inverter power supply is as follows. 5-8d in
It can be seen that B is reduced. 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, when the ratio of the 6.5% silicon steel plate 12a to the whole core cross section is 50%, the
゜Since the noise is almost the same as that of an iron core made of only 12g of 5% silicon steel plate, even if the proportion of 6.5% silicon steel plate 12a is increased further, the noise reduction effect will be small, and on the contrary, the iron loss and This is not preferable because magnetic properties such as excitation current deteriorate.

In the above embodiment, the wound core 1 of the 6.5% silicon steel plate 12a is
2 is wound on the outside of the wound core 11 of the grain-oriented silicon steel plate 11a, so the bending curvature at the core corner part can be large, and the 6.5% silicon steel sheet is relatively brittle and cannot be wound with a small bending curvature. Even raw steel plate 12a can be easily wound to form wound core 1.
2 can be formed.

In addition, since the 6.5% silicon steel 12a is wound on the outside of the combination core 13, the 6.5% silicon steel plate 12a with low magnetostriction is placed in the core portion with a large noise-generating radiation surface. By arranging these, a greater noise reduction effect can be obtained.

Further, the effect of significantly reducing vibration of the transformer can be obtained.

In this way, by forming the core 13 in which the grain-oriented silicon steel plate 11a and the 6.5% silicon steel plate 12a are combined, the deterioration of the magnetic properties can be reduced, and a transformer core for an inverter power supply with very low noise and vibration can be obtained. I can do it.

Note that this core configuration is not limited to inverter power transformers;
Of course, it is effective for iron cores of devices that contain harmonics in the fundamental wave (50Hz or 60Hz), such as rectifier transformers.

[Effects of the Invention] As explained above, the transformer core according to the present invention has the effect of improving the deterioration of B-H characteristics in the high magnetic flux density region of low magnetostrictive magnetic materials and significantly reducing noise. It will be done.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the transformer core of the present invention, and FIG.
, An explanatory diagram showing a comparison of core loss characteristics using a 5% silicon steel plate and a grain-oriented silicon steel plate. Figure 3 shows the excitation capacity of an iron core using a 6.5% silicon steel plate and a grain-oriented silicon steel plate. An explanatory diagram showing a comparison. Fig. 4 is an explanatory diagram showing a comparison of the noise of iron cores using 6.5% silicon steel plate and grain-oriented silicon steel plate. Fig. 5 is a front view showing a conventional transformer for inverter power supply. It is. 1a... Grain-oriented silicon steel plate, 1... Grain-oriented silicon steel plate wound core, 2a... 6.5% silicon steel plate (low magnetostrictive magnetic material), 2
...6.5% silicon steel plate wound core, 3...Combination core.

Claims (1)

[Claims] A wound core with a grain-oriented silicon steel plate wound thereon is arranged on the inner side, and a magnetic material with lower magnetostriction than the grain-oriented silicon steel sheet is wound around the outside of the wound core to form a combination core, and among these, a low magnetostrictive magnetic material is wound. A transformer core characterized in that the cross-sectional area of is 10 to 50% of the total core cross-sectional area.