JPH0410662Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to improvement of an electromagnetic shielding device for AC electrical equipment.

[Conventional technology]

A conventional configuration of this type of device is shown in FIG.

In this figure, 1 is a tank that is a structure of AC electric equipment, 2A and 2B are reciprocating current bars that are housed in this tank and are conductors that flow the alternating current of AC electric equipment, and 3 is an electromagnetic shield, and the reciprocating current is In order to reduce the stray loss caused by the magnetic flux generated by the alternating current flowing through the bars 2A and 2B entering the tank 1, and to prevent local overheating of the tank, a tank is installed between the reciprocating current bar and the tank. A flat conductor is disposed close to 1. Note that A, B, C, D, and E are codes for indicating specific positions of the electromagnetic shield and the tank.

[Problem that the invention attempts to solve]

However, in the electromagnetic shield configured as described above, if the installation range is narrow, the eddy current loss occurring in the electromagnetic shield increases rapidly toward the end, and the eddy current loss occurring in the tank also increases due to the electromagnetic shield. There is a tendency for electromagnetic shielding to concentrate near the edges of the shield, and as a result, local overheating occurs in the concentrated area. Therefore, in order to obtain the desired loss reduction effect and local overheating prevention effect, it is necessary to provide electromagnetic shielding over a fairly wide area. It was necessary to set it up.

This idea was made to solve these problems, and it effectively reduces eddy current loss and prevents local overheating of the structure by using an electromagnetic shield installed within a predetermined area. It was designed to be achievable.

[Means for solving problems]

In this invention, the end of the electromagnetic shield is bent into a curved shape toward the conductor through which the alternating current flows, and is removed from the structure of the alternating current electrical equipment.

[Effect]

By bending the end of the electromagnetic shield into a curved shape toward the conductor through which the alternating current flows and removing it from the structure of the AC electrical equipment, eddy currents concentrated at the end of the electromagnetic shield (due to the current flowing through the conductor) can be removed. Of the magnetic flux, the magnetic flux generated within the electromagnetic shield by the magnetic flux passing through the electromagnetic shield becomes less likely to affect the structure, and the magnetic flux due to the conductor current is reduced by the eddy current generated within the electromagnetic shield. A magnetic flux in the opposite direction is generated and cancels the magnetic flux due to the conductor current, resulting in a decrease in the magnetic flux reaching the structure.

[Example of idea]

An embodiment of this invention shown in FIG. 1 will be described below.

In this figure, numeral 3 is an electromagnetic shield that is a feature of this invention, and its installation range, shape, and constituent materials are the same as those of conventional shields, except for a reciprocating current bar 2A whose end 3A is a conductor through which alternating current flows; Tank 1 is a structure that is bent into a curved shape toward 2B.
They are trying to stay away from it. The rest of the configuration is the same as the conventional one, so the explanation will be omitted. As described above, by bending the end portion 3A of the electromagnetic shield 3 into a curved shape toward the reciprocating current bars 2A, 2B, which are conductors through which alternating current flows, so that the electromagnetic shield 3 can be separated from the tank 1, the electromagnetic shield can be This reduces end effects and improves loss, etc. That is,
Among the magnetic flux due to the current flowing through the reciprocating current bars 2A, 2B, the magnetic flux passing through the electromagnetic shield 3 causes an eddy current generated in the electromagnetic shield 3 to be opposite to the magnetic flux due to the current flowing through the reciprocating current bars 2A, 2B. A magnetic flux is generated in the direction, canceling the magnetic flux due to the current of the reciprocating current bars 2A and 2B, and as a result, reducing the magnetic flux reaching the tank 1, which is a structure, reducing the eddy current loss generated in the tank 1, as well as electromagnetic shielding. This also reduces the eddy current loss in No. 3 itself. More importantly, the eddy current in the electromagnetic shield 3 tends to concentrate at the edges due to the skin effect, so if the electromagnetic shield 3 remains a flat plate,
The magnetic flux due to the eddy current concentrated at the end 3A increases, and if the tank 1 is nearby, it will be greatly affected, and the eddy current loss generated in the tank 1 will also tend to concentrate near the end 3A of the electromagnetic shield 3, causing local Overheating is likely to occur, but since the end 3A of the electromagnetic shield 3 is bent into a curved shape toward the reciprocating current bars 2A and 2B and released from the tank 1 as described above, the end 3A of the electromagnetic shield 3 is Eddy current loss occurring in the tank 1 due to concentrated eddy currents is reduced, and local heating thereof can also be prevented.

Figure 2 is a characteristic diagram to show the state of loss improvement. Figure a shows the loss density at each position of the electromagnetic shield, and A, B, and C on the horizontal axis are the same as those in Figures 1 and 3. These correspond to the positions indicated by A, B, and C, respectively. As is clear from this characteristic diagram, according to this invention, the electromagnetic shield 3
The peak of the loss density near the end of , ie, position B or position C, is much lower than that of the conventional one.

Further, FIG. 2b shows the loss density at each position of the tank, and D and E on the horizontal axis correspond to the positions indicated by D and E in FIGS. 1 and 3, respectively. As is clear from this characteristic diagram, according to this invention, the peak of the loss density near the end of the electromagnetic shield, that is, near the E position, is much lower than that of the conventional one.

As a result, electromagnetic shielding and total losses in the tank are also reduced, and local overheating of the tank is also less likely.

In the above examples, the cause of magnetic flux generation in AC electrical equipment was explained as a reciprocating current bar, but it goes without saying that the same applies to transformers, reactor windings, and other AC electrical equipment. do not have.

[Effect of idea]

This device is constructed as described above, and the end of the electromagnetic shield is bent into a curved shape toward the conductor through which alternating current flows, and is separated from the structure, thereby reducing eddy current loss and local overheating. It is effective in preventing.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of this invention, and Fig. 2 is a characteristic diagram showing the state of loss improvement in the above embodiment. Shows the distribution of loss density.
Further, FIG. 3 is a schematic diagram showing a conventional device. In the figure, 1 is a tank, 2A and 2B are reciprocating current bars, and 3 is an electromagnetic shield. Note that the same reference numerals indicate corresponding parts.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) In an electromagnetic shielding device for AC electrical equipment in which a flat electromagnetic shield made of a conductor is arranged between the structure of the AC electrical equipment and a conductor through which alternating current flows. An electromagnetic shielding device for AC electric equipment, characterized in that an end of the electromagnetic shield is bent into a curved shape toward the conductor and removed from the structure. (2) The electromagnetic shield for AC electrical equipment according to claim 1 of the utility model registration, wherein the structure is a tank of the AC electrical equipment. (3) The electromagnetic shield for an AC electrical device as set forth in claim 1 or 2, wherein the AC electrical device is a transformer. (4) The electromagnetic shield for an AC electric device according to either claim 1 or 2 of the utility model registration claim, wherein the AC electric device is a reactor.