JPH02105507A - Low-noise dry-type transformer - Google Patents

Abstract

PURPOSE:To reduce leakage of noise of low-frequency band from a ventilation window by setting the distance between a reflection plate and the ventilation window provided within a case, enabling direct and reflected sound waves to be superposed in reverse phase. CONSTITUTION:The main unit 5 of a transformer is stored within a case 1 and air for cooling enters or escapes from the case 1. An absorption material 9 is adhered to one part of the inner surface of the case 1. Also, vibration-proof rubber 10 is provided between the case 1 and a bottom plate 3 within the main unit 5 of transformer and a reflection plate 11 is provided within the case 1. Then, mounting positions of the ventilation window 7 and 8 and the reflection plate 11 are set so that the distance required for the direct sound of the main unit 5 of transformer to reach the ventilation windows 7 and 8 and the distance for the reflected sound by this reflection plate 11 to reach the ventilation windows 7 and 8 differ by the length obtained by multiplying the semi- wavelength of the direct sound by odd numbers. Thus, they are superposed in reverse phase at the ventilation window position to attenuate noise.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a low-noise dry transformer that can sufficiently reduce noise in a low frequency band.

(Prior Art) When a transformer is operated with excitation, vibration is generated, and the energy of this vibration is propagated to the outside through a case (container) and becomes noise. The main causes of this vibration are magnetostrictive vibration of the iron core and magnetic attractive force between the laminated layers or joints of the silicon steel strip.

Techniques for reducing such transformer noise have been reported. For example, as described in the literature "Noise and Noise Prevention" by Sakae Morita, published by Ohmsha, pages 266 to 267, there is a method of making the transformer case double-walled, a porous plastic on the inner surface of the case, There are means for attaching sound absorbing members made of glass wool, felt, etc.

(Problems to be Solved by the Invention) However, there are the following problems when applying the above-mentioned noise reduction means to a self-cooling dry type transformer that cools the transformer body inside the case by natural convection. . That is, it is not possible to construct a completely sealed double-walled structure due to the necessity of preventing temperature rise and simplifying operation and maintenance. Generally, due to the above-mentioned needs, double walls are provided with ventilation windows, but the leakage noise from these ventilation windows is large and the noise reduction effect is low.

Additionally, double walls are economically disadvantageous and require a large space.

In this case, narrowing the distance between the double walls in order to save space is still not effective because sound attenuation cannot be achieved.

Therefore, a configuration may be considered in which the above-mentioned means using the sound absorbing portion is applied to the means for making a double wall. In other words, a sound-absorbing material is inserted into the gap between the double walls to attenuate the sound. In this configuration, the sound pressure rises and falls within the space (gap), but since there is little movement of air particles, no sound absorption effect can be obtained. In addition, the frequency of the noise generated by the transformer is, for example, 100Hz, 200Hz when the power supply frequency is 50Hz.
.

Since the main component is 300Hz and belongs to the low frequency band, even if the above-mentioned sound absorbing member is used, the noise in the low frequency band can hardly be reduced, and overall, sufficient noise reduction cannot be achieved. There wasn't.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a low-noise dry transformer that can sufficiently reduce noise in a low frequency band.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention has the following structure. That is, in a low-noise dry transformer in which a ventilation window is provided in a case that houses the transformer main body, a reflecting plate is provided on the inner surface of the case, and the distance from which direct sound from the transformer main body reaches the ventilation window and the reflection The mounting positions of the ventilation window and the reflecting plate are set so that the distance from which the sound reflected by the board reaches the ventilation window differs by an odd number times the half wavelength of the direct sound. .

(Function) According to the relationship between the distance that direct sound travels to the ventilation window and the distance that reflected sound travels to the ventilation window, the wavelength or half wavelength of the direct sound and the reflected sound wave differs. , at the location of the ventilation window, the noise is superimposed in an opposite phase state, thereby attenuating the noise.

(Example) Hereinafter, a first example of the present invention will be described based on FIGS. 1 to 3. 1 is a case, and this case 1 is composed of a side plate 2, a bottom plate 3, and a top plate 4. 5 is a transformer main body, and 6 is a coil portion of the transformer main body 5. This transformer main body 5 is housed inside the case 1. The case 1 has an upper window 7 and an upper window 8, and the window 7.
Cooling air enters and exits the case 1 through 8.

On the other hand, a sound absorbing material 9 is adhered to a part of the inner surface of the case 1. This sound absorbing material 9 is made of, for example, porous plastic, glass wool, felt, or the like. Further, a vibration-proof rubber 10 is provided between the transformer main body 5 and the bottom plate 3 of the case 1. Also, inside the case 1, there is a reflector 1.
1 is provided.

The entire case 1 is installed on a foundation foundation 13 via a channel steel 12. In this case, the reflector 11 and the upper window 7. The position of the upper window 8 is set as follows. First, I will explain the noise of the transformer. That is, the noise of the transformer is, for example, at the power supply frequency f. When excited at -50H, magnetostrictive vibrations occur at 2 f o and 4 f o
, 6 f o... f. vibrates at an even multiple of However, the frequency that becomes a problem in this case is 2fo's 100H
The 200Hz component of z or 4f is the main component. Here, the 100 Hz component of 2fo will be explained.

Figure 2 shows the temporal change in the fundamental wave vibration of the transformer at time t, ~
This is shown for one cycle of t4. In other words, as shown in FIG. 2(a), the distance between the transformer main body 5 and the coil 6 expands at time t1, and returns to the original state at time t2 as shown in FIG. 2(b), and the second As shown in Figure (C), it shrinks at time t3, and as shown in Figure 2 (d
), it returns further to the original state at time t4. As shown in the figure, the area where the vibration is large is around the center of the coil 6, so the center part of the coil 6 contributes to the noise.

In other words, the vibration of the central part of this coil 6 becomes noise,
Sound directly leaks through the upper window 7 and upper window 8 and is propagated to the outside.

Here, if the generated noise frequency f and the wavelength of the sound wave are λ, the following relationship is obtained.

λ-T c: Sound velocity Therefore, as shown in FIG. The upper window 7. The mounting positions of the upper window 8 and the reflection plate 11 are set.

In this embodiment, from the center of the coil 6, the upper window 7 and the upper window 8 are
For example, if the noise generation frequency is f-300Hz, then λ - T - T - 1,33 m Speed of sound in air at room temperature c = 340 m/see In other words, the wavelength λ is 1.33 m. , R2-
R, -λ/2-0.665m.

g4-Ω3=λ/2-0.665m It is said that

Next, top 2! The effect of +'4 formation will be explained. That is, when the transformer main body 5 is excited, noise is emitted due to magnetostrictive vibration. Therefore, the noise is generated by
Areas with large vibrations contribute the most to noise, and coil 6
The central part of In this case, some sound is radiated directly to the upper window 7 and the upper window 8, and some sound is radiated to the upper window 7 and the upper window 8 as reflected sound by the reflecting plate 11. The other (relatively high frequency components) are absorbed by the sound absorbing material 9.

Here, in this embodiment, the direct sound distance g1Ω3 and the reflected sound distance Ω21g4 are made different by a length equivalent to half a wavelength (λ/2), so the upper window 7 and the upper window 8 The phases of the two superimposed sound waves are shifted by half a wavelength and have opposite phases. Therefore, the rain sound waves cancel each other out due to interference and are significantly attenuated. As a result, the noise in the low frequency band, which is the sound of f, which is the main component, is significantly reduced. In other words, the leakage sound is canceled out at the outlet (the upper window 7 and the upper window 8), and the noise to the outside of the case 1 is reduced.

In the above embodiment, the reflector 11 is attached parallel to the top plate 4 and the bottom plate 3, but the reflector 11 may be tilted as shown in FIG.

[Effects of the Invention] As described above, in the present invention, a reflector is provided in the case, and the direct sound and reflected sound are made to overlap each other in opposite phases due to the distance relationship between the reflector and the ventilation window. As a result, it is possible to effectively reduce the leakage of noise in the low frequency band from the ventilation window, resulting in an excellent effect of reducing noise.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional front view showing the first embodiment of the present invention, and FIG.
The figure is a diagram showing the passage of time for one cycle of the fundamental wave vibration of the transformer main body to explain the present invention, Figure 3 is a noise propagation diagram to explain the present invention, and Figure 4 is a cross section showing the second embodiment. It is a front view. 1...Case, 2...Case side plate, 3...Bottom plate of case, 4...Top plate of case, 5...Transformer main body,
6...Coil, 7...Upper window, 8...Upper window, 9...
・Sound absorbing material, 10... Vibration proof rubber, 11... Reflection plate, 1
2... Channel steel, 13... Foundation foundation. Applicant's representative Patent attorney Takehiko Suzue Figure 1 SeC (a) 25eC (b) SeC 45eC (d) Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a low-noise dry transformer in which a case for storing a transformer body is provided with a ventilation window, a reflecting plate is provided on the inner surface of the case, and a distance from which direct sound from the transformer body reaches the ventilation window;
The distance from which the sound reflected by the reflector reaches the ventilation window is:
A low-noise dry type transformer, characterized in that the installation positions of the ventilation window and the reflection plate are set so that they differ by a length that is an odd number times the half wavelength of the direct sound.