JPH0154844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to improvements in magnetic shielding devices for stationary induction electric appliances such as transformers and reactors.

[Background of the invention]

In recent years, the capacity of stationary induction appliances has tended to become larger and larger, and the amount of leakage magnetic flux caused by the current flowing through the windings and lead wires has also tended to increase. In order to reduce the increase in loss in structural materials caused by the intrusion of leakage magnetic flux, magnetic shields made of laminated thin steel plates with high magnetic permeability such as silicon steel plates are placed on the surfaces of structural materials. ing. This will be explained with reference to FIGS. 1 to 4.

Fig. 1 shows a longitudinal cross-sectional view of a part of the transformer;
FIG. 3 shows a cross-sectional view. A part of the magnetic flux 8 generated between the inner winding 1 and the outer winding 2 flows toward the iron core 4 side, and the remaining part flows toward the tank 5 side. tank 5
The magnetic flux 8 flowing to the side flows through the tank 5 and creates a magnetic path returning between the inner winding 1 and the outer winding 2. When the magnetic flux 8 enters the tank 5 or flows through the tank 5, eddy current loss occurs in the tank 5 due to eddy currents (not shown) that try to cancel the magnetic flux 8, causing local damage to the tank 5. Overheating will occur. To prevent this, a magnetic shield 6 made of laminated thin steel plates with high magnetic permeability is attached to the inner wall of the tank 5 so that most of the magnetic flux 8 entering the tank 5 passes through the magnetic shield 6. This is designed to reduce losses in the tank 5. The range to which these magnetic shields 6 are attached is the entire area inside the tank 5 as shown in FIG. 2, and the area approximately facing the outer diameter L ₀ of the winding 3 as shown in FIG. 3.
In the case of FIG. 3, a high voltage lead wire (not shown) is drawn out from the interphase portion of the winding 3 in an ultra-high voltage system, so that the magnetic shield of the interphase portion is omitted. In addition, 7 is a fastener, and 9 is a center line of each phase.

Each of the magnetic shields 6 shown in FIGS. 2 and 3 is divided into a plurality of pieces in the width direction, as shown in FIG. By configuring like this,
Efforts are being made to reduce loss due to eddy current. In other words, in general, the eddy current loss We
is expressed by the following formula.

We = k × B ² × l ² × f ² , where k: constant depending on the material B: applied magnetic flux density l = shield width f: frequency From the above formula, by reducing the shield width l, the loss due to eddy current can be reduced. However, recently, due to an increase in the amount of leakage magnetic flux, the magnetic flux 8 that has entered the magnetic shield 6 has started to leak to the inner wall of the tank 5. This phenomenon is illustrated in Figures 5 and 6.
This will be explained using figures. In order to simplify the explanation, FIG. 5 shows a case where the magnetic material magnetic shield 6 facing the winding 3 is divided into three parts. It is already known that more magnetic flux 8 enters the magnetic shield 6B that is attached at a location away from the magnetic material. In FIG. 5, since a large amount of magnetic flux 8 penetrates into the magnetic material magnetic shield 6A, the magnetic flux density inside the shield becomes higher than that of the magnetic material magnetic shield 6B, and depending on the case, local saturation may occur. In particular, if the magnetic material magnetic shield 6 is divided at a position other than the phase center, and if the magnetic material magnetic shield 6A is locally saturated, part of the magnetic flux 8A will be transferred to the magnetic material through the tank 5. It was confirmed in experiments by the present inventors that the magnetic shield was transferred to the magnetic shield 6B. This transfer of the magnetic flux 8A may cause loss near the transfer portion in the tank 5, resulting in local overheating. FIG. 6 shows a case where the magnetic material magnetic shield 6 is divided into four parts, and similarly, a case where local overheating occurs due to the magnetic flux 8A moving inside the tank 5 is shown.

[Purpose of the invention]

An object of the present invention is to provide a magnetic shielding device for a stationary induction electric appliance that can prevent local overheating of a tank due to leakage magnetic flux transferred from the magnetic shield to the tank.

[Summary of the invention]

The magnetic shielding device for a stationary induction electric appliance of the present invention is provided when a magnetic shield made of a magnetic plate laminated at a position facing the winding is attached to the inner wall of a tank containing a winding. The winding is divided into left and right parts at a position facing the phase center of the winding, the total width is approximately 1/2 of the diameter of the winding, and the magnetic shield is installed on the tank inner wall. The magnetic plates are laminated to a thickness that allows the magnetic flux density to be maintained to the extent that the invading leakage magnetic flux does not saturate, thereby preventing local overheating of the tank due to the leakage magnetic flux.

[Embodiments of the invention]

An embodiment of the magnetic shielding device for a stationary induction appliance according to the present invention will be described below with reference to FIG. 7, in which the same parts as those of the prior art are designated by the same reference numerals. The magnetic material magnetic shield 6 is
2 on the left and right with the position of the phase center line 9 of the winding 3 as the boundary
It is divided into individual pieces and laminated, and the total width thereof is approximately 1/2 of the diameter of the winding 3, and is attached to the inner wall of the tank 5 facing the winding 3. The pair of magnetic shields 6C and 6C formed separately are arranged as shown in FIG. In the oval tank, the first
They are arranged as shown in Figure 1. Therefore, since there are no adjacent magnetic shields other than the phase center position, even if the magnetic flux density inside the magnetic shields 6C, 6C is considerably high, the magnetic shields 6
The magnetic flux 8 that has entered C does not flow through the tank 5. Since the two magnetic shields 6C, 6C with the phase center as a boundary are located in magnetically symmetrical positions, they do not interfere with each other and no magnetic flux flows. Therefore, local overheating does not occur in the tank 5.

In the one in FIG. 8 showing still another embodiment, the seventh
In the case of the embodiment shown in the figure, if the width of the magnetic material magnetic shield 6C divided into two at the phase center position becomes too large, local overheating of the magnetic material magnetic shield 6C becomes a problem. A magnetic material magnetic shield 6D, which is narrower in width than the magnetic material magnetic shield 6C, is arranged on the surface facing the magnetic material magnetic shield 6C. As a result, local overheating of the magnetic material magnetic shield 6C can be prevented, and other effects similar to those of the above-described embodiments can be obtained.

FIG. 9 shows an embodiment in which the number of windings 3 is one, and in this example, the magnetic material magnetic shield 6C is 2.
It is arranged and attached at a position opposite to the winding 3.

The installation range L ₁ of the magnetic material magnetic shield described in each embodiment is best approximately 1/2 of the diameter L ₀ of the winding 3 in a general transformer. The width of this magnetic shield is determined by taking into account the weight when the magnetic plates are laminated and local overheating caused by leakage magnetic flux, but the width that minimizes local overheating and does not lead to an increase in weight is L ₀ / It becomes 2.

In this way, the magnetic shielding device for the stationary induction electric appliance of each embodiment divides the magnetic material magnetic shield into two parts, arranges the centers of the divided magnetic material magnetic shields to face the winding axis, and separates the magnetic material from the winding. Since the laminated thickness of the magnetic plate of the magnetic material magnetic shield is selected so that the magnetic flux density can be maintained to the extent that the invading leakage magnetic flux is not saturated, intrusion from the magnetic material magnetic shield into the tank can be prevented.

〔Effect of the invention〕

As described above, in the magnetic shielding device for static induction electric appliances of the present invention, the width of the magnetic shield is approximately 1/2 of the diameter of the winding, so the overall weight of the magnetic material magnetic shield can be reduced, resulting in lighter weight and lower cost. It is possible to aim for Furthermore, since the magnetic shield is arranged in two parts with the phase center position as a boundary, the amount of magnetic flux transferred to the tank in the magnetic shield is reduced, and local overheating of the tank can be prevented.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of a part of a transformer having a conventional magnetic shielding device, Fig. 2 is a cross-sectional view of a tank in which a magnetic material magnetic shield is attached to the entire inner wall of the device of Fig. 1, Figure 3 is a cross-sectional view of the tank in which a magnetic shield is attached almost only to the part of the inner wall facing the windings of the device shown in Figure 1, and Figure 4 is a cross-sectional view of the tank shown in Figures 2 and 3.
An explanatory diagram of the state in which the magnetic material magnetic shield shown in the figure is divided in the width direction, Fig. 5 is an explanatory diagram of the magnetic flux flow of Fig. 4,
Figure 6 is an explanatory diagram of the magnetic flux flow when the magnetic material magnetic shield in part A of Figure 3 is divided into four parts, and Figures 7 to 9
The figures are detailed views showing different embodiments in which the magnetic shielding device of the stationary induction electric appliance of the present invention is applied to the same part as the part A in Fig. 3, and Figs. 10 and 11 are respectively the magnetic material magnetism of Fig. 7. FIG. 2 is a cross-sectional view of a tank with a shield attached. 3...Winding, 5...Tank, 6, 6A, 6B,
6C, 6D...Magnetic material magnetic shield.

Claims (1)

[Claims] 1. A magnetic material magnetic shield made of laminated magnetic plates is attached to the inner wall of a tank containing a winding at a position facing the winding, the magnetic material magnetic shield is located at a position facing the phase center of the winding. It is divided into left and right parts, and the total width is approximately 1/2 of the diameter of the winding, and it is attached to the inner wall of the tank.
A magnetic shielding device for a stationary induction electric appliance, characterized in that the magnetic material magnetic shield has magnetic plates laminated to a thickness that can maintain magnetic flux density to such an extent that leakage magnetic flux penetrating from the windings does not saturate.