JP7309646B2 - bus duct - Google Patents

Description

The present invention relates to bus ducts.

The switchgear electrically connects the circuit breaker, the power system, and the load. A busbar with high heat dissipation performance is used for this connection, but a metal housing is used around the busbar to prevent electromagnetic waves from flowing into surrounding electronic devices due to the current of the busbar and to prevent electric shock. placed.

Metal chassis are usually made of low-cost steel, but since steel is a magnetic material, the current that flows through the busbars causes iron loss in the surrounding chassis, which increases the temperature of the chassis. Rise. If the temperature of the housing rises, there is a risk that a person who touches the housing will be burned, and the temperature of the conductor will rise, which can lead to deterioration in characteristics such as an increase in the resistance of the conductor. As a technique for improving these, there is Patent Document 1, for example.

In Patent Document 1, a box-shaped steel plate is formed around a conductor, and a part of the box is made of a synthetic resin plate that is a non-magnetic material, thereby suppressing iron loss and suppressing the temperature rise of the housing. there is

Japanese Patent Laid-Open No. 11-289611

In Patent Document 1, since the housing is made of a synthetic resin plate with a low Young's modulus, when a short-circuit current flows through the bus duct, a large electromagnetic repulsion occurs between the short-circuit current and the eddy current flowing in the housing. When it occurred, there was a possibility that the housing could not be held mechanically.

Furthermore, synthetic resins generally have lower thermal conductivity than metals, and there is a possibility that the temperature will rise due to poor heat dissipation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bus duct capable of improving the heat radiation performance without increasing the iron loss of the housing and maintaining the mechanical strength of the housing.

A preferred example of the present invention includes a housing and a conductor arranged in the housing, the housing containing stainless steel and an iron material , and a different kind of metal between the stainless steel and the iron material. A bus duct having an intermetallic corrosion prevention part.

According to the present invention, it is possible to improve the heat radiation performance without increasing the iron loss of the housing and maintain the mechanical strength of the housing.

4 is a diagram showing a bus duct in Example 1. FIG. 4 is a diagram showing a housing of the bus duct in Example 1. FIG. FIG. 4 is a diagram showing the flow of magnetic flux around a magnetic metal housing and a conductor; FIG. 4 is a diagram showing the flow of magnetic flux around a housing and conductors made of a combination of non-magnetic metal and magnetic metal. It is a figure which shows the structure of the fixture of a housing|casing. It is a figure which shows the dimension of the magnetic material of a housing|casing, and a non-magnetic material. 4 is a diagram showing the relationship between the bus duct and the direction of gravity in Embodiment 1. FIG. FIG. 10 is a diagram showing a bus duct structure having a housing with protrusions in Example 2; FIG. 10 is a diagram showing a bus duct structure having a black-painted non-magnetic material in Example 2; FIG. 10 is a diagram showing the positional relationship between a plurality of conductors and a housing in Example 3; FIG. 11 is a diagram showing the positional relationship between a plurality of conductors arranged in a triangular shape and a housing in a modified example of the third embodiment; FIG. 11 is a diagram showing the positional relationship between a plurality of obliquely arranged conductors and a housing in a modified example of the third embodiment; FIG. 10 is a diagram showing a bus duct in Example 4;

An embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 shown in FIG. 1 shows a bus duct 1 composed of a housing 2 and conductors 100 arranged in the housing 2 . A bus duct is a power trunk line system that can meet the power demand of, for example, a building or a factory. FIG. 2 is a diagram showing the housing 2. As shown in FIG. The housing 2 has a magnetic material 102 surface, a non-magnetic material 103 surface, and a dissimilar metal corrosion prevention portion 104 . Conductor current 199 flows through conductor 100 .

Since the conductor current is alternating current, the current flows in both directions perpendicular to the plane of the paper as shown in the figure. For example, the magnetic body 102 is made of steel, which is a low-cost housing material, the non-magnetic body 103 is made of non-magnetic stainless steel, and the intermetallic corrosion prevention section 104 is made of an insulator or the like. It will be explained that the loss of the housing can be suppressed according to the first embodiment in comparison with FIG.

FIG. 3 shows a bus duct of a housing composed only of a conductor 100 and a metal magnetic body 102, and is a diagram showing a comparative example for comparison with the present embodiment. When a current 199 of the same phase is passed through each conductor, a magnetic flux is generated near the conductors. This magnetic flux is divided into a magnetic flux 201 passing through the air around the conductor and a magnetic flux 200 passing only inside the housing.

The magnetic flux 200 passing only through the housing made of steel is large compared to the magnetic flux 201 passing through the air, which has a large magnetic resistance. As these magnetic fluxes increase, the core loss of the housing increases, resulting in a higher temperature rise. As shown in formula (1), when the current becomes high frequency, the eddy current loss calculated by the square of the frequency increases, and the iron loss W becomes larger.

FIG. 4 shows a configuration example in which magnetic flux 200 passing only through the housing is reduced in order to reduce iron loss, and shows a comparative example for comparison with the present embodiment. The housing is composed of a magnetic material 102 and a non-magnetic material 103 . Since the magnetic resistance of the non-magnetic material 103 is much higher than that of the magnetic material 102, the magnetic flux flowing into the housing becomes smaller than when the case is composed only of the magnetic material 102, and iron loss can be reduced.

However, if the magnetic material 102 and the non-magnetic material 103 are made of different metals, corrosion between dissimilar metals occurs when moisture such as water vapor is contained in the contact surfaces, resulting in deterioration of the mechanical strength of the housing. Therefore, as shown in FIG. 1, by forming a dissimilar metal corrosion prevention portion 104 made of an insulating material between the magnetic material 102 and the non-magnetic material 103, it is possible to prevent dissimilar metal corrosion.

Next, the electromagnetic repulsive force of the housing will be described. When current flows through the conductor, magnetic flux flows into the housing, but eddy currents are generated in the housing to negate the magnetic flux. The eddy current and conductor current generate an electromagnetic repulsive force between the housing and the conductor.

For example, when a very large current such as a short circuit current flows through the conductor, the electromagnetic repulsion becomes larger. When a large electromagnetic repulsive force is generated in the housing, the housing is distorted. Therefore, by using a material with a high Young's modulus as the nonmagnetic material 103, which can maintain mechanical strength even when a large electromagnetic repulsive force is generated in the housing, the housing can have high mechanical strength. .

In the first embodiment, an insulating material is provided between the magnetic material 102 and the non-magnetic material 103. However, a material having an ionization tendency intermediate between that of the magnetic material 102 and the non-magnetic material 103 is used as the anti-corrosion part between dissimilar metals. 104 may be used. Even in that case, corrosion between dissimilar metals can be prevented.

For example, when the magnetic body 102 is made of a metal such as iron and the non-magnetic body 103 is made of a metal such as SUS304 which is stainless steel, the intermetallic corrosion prevention section 104 is made of a material such as nickel. By making the dissimilar metal corrosion prevention part 104 metal, the amount of noise radiation can be reduced by making the entire housing conductive. However, if the conductor current has a low frequency such as a commercial frequency, the effect on other devices is small, so the non-magnetic material need not be a metal as long as it has a Young's modulus similar to that of metal.

As shown in FIG. 5, in this embodiment, fasteners 301 such as screws are used to fix the magnetic substance 102, the non-magnetic substance 103 and the intermetallic corrosion prevention portion 104 together. If the fixture 301 is a magnetic material, the magnetic metal and the non-magnetic metal can be brought into contact with each other through the fixture 301. Therefore, the magnetic fixture 301 is plated to prevent corrosion between dissimilar metals. . By adopting such a configuration, it is possible to avoid contact between the magnetic metal and the non-magnetic metal, and prevent corrosion between dissimilar metals.

Furthermore, in this embodiment, three conductors 100 are used for explanation, but the same effect can be obtained whether the phases of the conductor currents 199 of the conductors are the same phase or three phases, and it depends on the number of phases. do not. Also, although three conductors have been described, the same effect can be obtained with at least one conductor.

Here, although the housing is described as a part of the non-magnetic material, the relationship between the width (magnetic path length) 501 of the non-magnetic material 103 and the magnetic resistance will be described with reference to FIG. The magnetic resistance of the housing is calculated from the magnetic permeability of the conductor material, the cross-sectional area of the magnetic path, and the length of the magnetic path, as shown in Equation (2).

The magnetic resistance of the housing shown in this embodiment is determined by the lengths (magnetic path lengths) 503, 504, and 505 of the magnetic material 102, the total magnetic path length 506 of the magnetic material, the width 501 of the non-magnetic material 103, and the dissimilar metal. Using the width (magnetic path length) 502 of the anti-corrosion portion 104, it is calculated by Equation (3).

In general, the magnetic permeability _μ2 of a non-magnetic metal is approximately the same as the corrosion portion _μ3 between dissimilar metals, and is about 1/5000 of the magnetic permeability _μ1 of a magnetic metal. Therefore, Equation (3) can be expressed as Equation (4), and it can be seen that the magnetoresistance is higher than that in the case where the housing is entirely made of magnetic metal.

Although the magnetic flux path shown in FIG. 6 is used to show the relationship between the non-magnetic material width 501 and the magnetic resistance, the magnetic flux path does not have to pass through the central portion of the housing as shown in FIG. Furthermore, although the configuration in which the magnetic body length 506 is longer than the non-magnetic body width 501 has been described, iron loss can be further reduced if the non-magnetic body width 501 is longer than the magnetic body length 506 .

However, stainless steel, which is a non-magnetic material, is generally more expensive than steel, which is a magnetic material, and may increase the housing cost. Width should be determined. For example, when the total value of the width 501 of the non-magnetic material and the width 502 of the corrosion prevention portion 104 between dissimilar metals is 1/5000 of the total magnetic path length 506 of the magnetic material, the magnetic resistance can be expressed as in Equation (5). can. In this case, the magnetic resistance is double the magnetic resistance when the entire housing is made of magnetic material, and the magnetic flux is reduced to 1/2. can.

Also, FIG. 7 shows the relationship between the bus duct of the first embodiment and the direction of gravity 601 . In general, the bus duct 1 is arranged in the upper part of the bus duct room, and electronic parts and the like are arranged in the lower part of the bus duct room. In order to suppress electromagnetic waves from conductors in the bus duct 1 with respect to the electronic parts, a magnetic body 102 that absorbs magnetic flux is arranged on the side close to the electronic parts, that is, in the direction of gravity 601 . On the other hand, since the upper part of the bus duct 1 is often the ceiling, it is desirable to construct a non-magnetic material through which the magnetic flux passes in the direction opposite to the direction of gravity. Furthermore, since the natural convection generated by the rise in the temperature of the housing flows in the direction opposite to gravity, non-magnetic materials, which generally have lower thermal conductivity than magnetic A configuration in which a magnetic body is arranged is desirable.

According to the first embodiment, it is possible to improve the heat radiation performance without increasing the iron loss of the housing and maintain the mechanical strength of the housing.

The bus duct 1 of the second embodiment shown in FIG. 8 includes a housing composed of a magnetic material 102, a non-magnetic material 103, and a corrosion prevention portion 104 between dissimilar metals, and a bus duct composed of a conductor 100 arranged in the housing. As shown, the non-magnetic body 103 is provided with protrusions 401 to increase its surface area.

In general, non-magnetic metals, such as stainless steel, have lower thermal conductivity than magnetic metals, such as steel. In order to compensate for this low heat conduction, the heat dissipation performance is improved by convection and radiation, and the non-magnetic body 103 is provided with projections 401 to increase the surface area.

Instead of the projections 401, recesses may be provided on the outside of the non-magnetic body 103 to increase the surface area of the outside of the non-magnetic body 103 and improve the heat dissipation performance.

The same effect can be obtained by arranging the projection 401 inside the housing surface (on the conductor side), but if the projection shape is made of metal, the distance between the conductors becomes short, and there is a possibility that dielectric breakdown may occur. Therefore, it is desirable to provide a protrusion on the outside of the housing. Also, heat radiation performance may be improved by providing a concave portion inside the non-magnetic material 103 on the housing surface.

Further, in this embodiment, the projection 401 is provided on the non-magnetic material 103, but the same effect can be obtained by providing the magnetic material 102 with a projection or recess.

In the second embodiment, the structure provided with the projections 401 for improving the heat dissipation performance due to convection and radiation has been described. Furthermore, as a modification, as shown in FIG. 9, the bus duct housing 2 may be made of a non-magnetic material with a black coating 105 . According to such a configuration, the heat dissipation performance by convection cannot be improved, but the heat dissipation performance by radiation can be improved.

According to the second embodiment, as shown in the first embodiment, it is possible to maintain the mechanical strength of the housing without increasing the iron loss of the housing, and further improve the heat dissipation performance of the bus duct. be able to.

FIG. 10 is a diagram showing the configuration of the bus duct of Example 3. FIG. The bus duct is composed of a housing 2 composed of a magnetic material 102 , a non-magnetic material 103 , and an intermetallic corrosion prevention section 104 , and conductors 100 A, 100 B, and 100 C arranged in the housing 2 . As shown in FIG. 10, regarding the positional relationship between housing 2 and conductors 100A, 100B, and 100C, conductor 100A is closest to housing 2 when the distances between other conductors 100B and 100C and housing 2 are compared. is placed in the shortest position. The surface of the housing 2 closest to the conductor 100A is composed of a non-magnetic material 103. As shown in FIG.

According to the third embodiment, among the magnetic fluxes described in the first embodiment, the influence of the magnetic flux 201 passing through the air can be reduced, and iron loss can be suppressed. The arrangement relationship between the conductors 100A, 100B, 100C and the housing 2 is determined by the insulation distance, and the non-magnetic material is arranged in the housing where the distances between the conductors 100A, 100B, 100C and the housing 2 are relatively short. I wish I could. Furthermore, although the description has been made using FIG. 10, the same effect can be obtained with the conductor arrangement as shown in FIGS.

FIG. 11 is a diagram showing the positional relationship between the conductors 100A, 100B, and 100C arranged in a triangle and the housing 2. As shown in FIG. FIG. 12 is a diagram showing the positional relationship between the conductors 100A, 100B, and 100C arranged obliquely and the housing 2. As shown in FIG. 11 and 12, the conductor 100A is arranged closest to the housing 2 compared to the other conductors 100B and 100C. A non-magnetic material 103 is arranged in the housing 2 that is closest to the conductor 100A.

According to the third embodiment, as shown in the first embodiment, it is possible to improve the heat radiation performance, maintain the mechanical strength of the housing, and reduce the influence of the magnetic flux 201 passing through the air in the magnetic flux. Furthermore, iron loss can be suppressed.

FIG. 13 is a diagram showing a bus duct of Example 4. FIG. The bus duct is composed of a housing 2 composed of a magnetic material 102 , a non-magnetic material 103 , and an intermetallic corrosion prevention section 104 , and conductors 101 A, 101 B, and 101 C arranged within the housing 2 . A recess 402 is provided in each of the conductors 101A, 101B, and 101C.

When an alternating current flows through a conductor, the current concentrates on the surface of the current due to the skin effect. If the conductor has recesses, it is possible to control the current density distribution of the conductor. For example, as shown in FIG. 13, current concentration occurs in the direction opposite to the concave portion 402 by providing the concave portion 402 on the side opposite to the surface facing each of the three-phase conductors 101A, 101B, and 101C. The total magnetic flux produced by the three-phase current is affected by the distance between the conductors. If the distance between the conductors is long, the cancellation effect is small, and if the distance between the conductors is short, the cancellation effect increases.

According to the fourth embodiment, by arranging the conductors 101A, 101B, and 101C having the recesses 402, regions with high current densities can be the surfaces facing the three-phase conductors 101A, 101B, and 101C, respectively. The same effect as when the distance is shortened can be obtained.

Reference Signs List 1 Bus duct 2 Casings 100, 100A, 100B, 100C Conductors 101A, 101B, 101C Conductors having recesses 102 Magnetic substance 103 Non-magnetic substance 104 Corrosion prevention part between dissimilar metals 199 Conductor current 301 Fixed Tool 401 ... Protrusion

Claims (7)

a housing;
a conductor disposed within the housing;
The housing is
A bus duct containing stainless steel and iron material and having a dissimilar metal corrosion prevention part between the stainless steel and iron material . The bus duct according to claim 1,
said stainless steel is arranged in a direction opposite to gravity,
The iron material is a bus duct arranged in the direction of gravity. The bus duct according to claim 1,
The stainless steel bus duct having protrusions. The bus duct according to claim 1,
The stainless steel is a bus duct painted black. The bus duct according to claim 1,
The bus duct, wherein when there is a first conductor closest to the case among the plurality of conductors, the case closest to the first conductor is the stainless steel . The bus duct according to claim 1,
A bus duct having a fixture for fixing the iron material , the stainless steel , and the dissimilar metal pipe corrosion prevention part, wherein the fixture is plated for preventing corrosion between dissimilar metals. The bus duct according to claim 1,
The bus duct, wherein each of the plurality of conductors has a concave portion on a side opposite to a surface facing each of the conductors.

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