JPH118914A - Closed-type distribution panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be able to easily open a cover as doors of a distribution box even if magnetic field is generated by a current flowing through conductors a arranged to the inside of the distribution box. SOLUTION: Non-magnetic spacers 12 are inserted between a box body and a steel door 4. The non-magnetic spacers 12 of high hardness material as brass or low hardness material as rubber with very small thickness change are attached to the circumference of a steel door 4 continuously or discontinuously. Magnetic attraction is decreased in proportion to the decrease of the quantity of flux passing through a box body 2 and the steel door 4, so that by the insertion of the non-magnetic spacers 12 between the box body 2 and the steel door 4 increasing the distance between them, the magnetic attraction decreases inversely proportional to the square of the distance and the possibility that the steel door 4 becoming unable to open can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a closed type switchboard having a conductor made of a ferromagnetic material and a conductor inside of which a current flows.

[0002]

2. Description of the Related Art It is desired that a material constituting a switchboard has high strength, is easy to process, and is low in price. The most universal material that can meet such demands is steel. Moreover, this steel is ferromagnetic. Therefore, hereinafter, a case will be described in which a switchboard is configured using steel, which is a ferromagnetic material, and a current flows through a conductor installed inside the switchboard. Hereinafter, a case where a direct current flows through the conductor will be described.

When a direct current flows through a conductor, a space around the conductor where a magnetic force acts, that is, a magnetic field is generated. The strength of the magnetic field is correlated with the magnitude of the current flowing through the conductor. Since the conductor is surrounded by steel, which is a structural material of the switchboard, the magnetic flux generated by this magnetic field tends to pass through steel having much higher magnetic permeability than air.

[0004] By the way, openings are provided in the front and rear surfaces (or side surfaces in some cases) of the switchboard so that the internal equipment can be maintained and inspected. However, these openings are usually closed to prevent danger. I have. Although there are various closing methods, it is common to cover the opening with a door having a hinge on one side or a hanging-type cover. The magnetic field generated around the conductor when an alternating current flows is an alternating magnetic field. When an alternating magnetic flux passes through the structural member of the switchboard due to the alternating magnetic field, an eddy current flows through the structural member, thereby causing a problem such as an increase in the temperature of the structural member. Therefore, when an alternating current is passed, the conductor through which the forward current flows and the conductor through which the return current flows are arranged close to each other. Even in this case, the magnetic flux is prevented from passing. However, in the case of direct current, even if there is only one conductor, inconvenience such as heat generation does not occur, so that the two reciprocating conductors are often arranged so as not to approach.

[0005]

When a magnetic flux passes through a box and a door constituting a switchboard due to a current flowing through a conductor and a magnetic field generated around the conductor, the magnetic flux causes a box to be formed. A suction force works between the door and the door. If the suction force is large, the door cannot be opened, and even if the suction force is not so large, there may be inconveniences such as the door cannot be easily opened.

An object of the present invention is to make it possible to easily open a cover of a switchboard such as a door even if a magnetic field is generated by a current flowing through a conductor installed in the switchboard.

[0007]

In order to achieve the above object, a closed switchboard according to the present invention comprises a box made of a ferromagnetic material, and a cover for closing an opening of the box also made of a ferromagnetic material. When the switchboard is made of a material and is provided with a conductor that allows a current to flow inside the box, when closing the switchboard, a gap member having a predetermined thickness made of a non-magnetic material is used. It is to be interposed between the box and the cover.

[0008] The spacing member is interposed continuously or intermittently around the entire periphery of the cover.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a perspective view of a conventional closed switchboard showing a box constituting a switchboard, a door and conductors installed therein. This closed switchboard comprises a box 2 and a steel door 4, both of which are connected by hinges 5. Since the conductor 6 through which a DC current flows is installed inside the switchboard, during operation of the switchboard, the steel door 4 is closed to prevent danger. Here, the direction of the direct current flowing through the conductor 6 is indicated by a thick arrow 7. It is well known that when a current flows through the conductor 6 in the direction of the arrow 7, a magnetic field in the direction indicated by the arrow 8 is generated by the right-hand rule.

FIG. 4 is a plan view of the conventional closed switchboard shown in FIG. 3 as viewed from above. Both sides of the box 2 are steel frames 3
, And a steel door 4 is provided on the front surface thereof. FIG. 4 shows a case where the steel door 4 is closed. As described above, the current flows through the internal conductor 6 from the bottom to the top. Then, a magnetic flux flows in the same direction as the magnetic field generated by this current.
And a magnetic flux 11 passing through the steel. As mentioned above, the magnetic permeability of steel, which is a ferromagnetic material, is much greater than that of air, so that most of the magnetic flux passes through the steel. However, due to the positional relationship between the conductor 6 and the steel frame 3 or the steel door 4, not all the magnetic flux passes through the steel, but the magnetic flux 10 passing through the air.
Also exists.

When the steel door 4 is closed, the steel frame 3
The gap d between the steel door 4 and the steel door 4 is very small and may be considered to be zero. When the magnetic flux 11 passing through the steel flows from the steel frame 3 to the steel door 4, an attractive force is generated between the two. This attractive force is proportional to the amount of magnetic flux and inversely proportional to the square of the gap d. Therefore, if the ratio of the magnetic flux 11 passing through the steel in the total magnetic flux generated by the current flowing through the conductor 6 is large, and if the gap d is small, the attractive force becomes large, and the door is difficult to open.

FIG. 1 is a plan view of a closed switchboard showing an embodiment of the present invention. FIG. 1 which is an embodiment of the present invention and FIG. 4 which is the above-mentioned conventional example are different in that a non-magnetic spacer 12 is inserted between the box body 2 and the steel door 4. When the nonmagnetic spacer 12 is inserted, the distance between the box 2 and the steel door 4 increases by the thickness of the nonmagnetic spacer 12.
As described above, since the suction force is inversely proportional to the square of the gap, the suction force is greatly reduced. Therefore, the non-magnetic spacer 12
If the thickness is increased, the risk that the door will not open can be eliminated. Further, since the magnetic permeability of the nonmagnetic spacer 12 is as small as that of air, the magnetic resistance of the magnetic flux 11 passing through the steel increases. Therefore, the ratio of the magnetic flux 11 passing through the steel in the total magnetic flux is reduced, so that the attractive force between the box 2 and the steel door 4 is also reduced.

FIG. 2 is a perspective view of a closed switchboard showing another embodiment of the present invention. The non-magnetic spacing member 12 is inserted between the box 2 and the steel door 4, and as shown in FIG. 2, the non-magnetic spacing member 12 inserted in the upper part of the switchboard has a continuous configuration. In addition, the nonmagnetic spacing member 12 inserted into the side of the switchboard is intermittent. Since the main purpose of the non-magnetic spacing member 12 is to maintain the spacing between the box 2 and the steel door 4, it may be continuous or intermittent. However, if the intermittent non-magnetic spacing member 12 is inserted into the upper portion, dust may enter the switchboard from a portion where the non-magnetic spacing member 12 does not exist. .

Further, the non-magnetic spacing member 12 may be a hard material made of a copper alloy such as brass, or a material having a small hardness such as rubber, as long as the thickness dimension does not change. Can be used for

[0015]

According to the present invention, the magnetic flux when a current flows through a conductor installed in a deviation type switchboard is attracted when passing from a box made of a ferromagnetic material through a cover also made of a ferromagnetic material. However, according to the present invention, the amount of magnetic flux passing through this portion can be reduced by inserting a spacer made of a non-magnetic material between the box and the cover.
The suction force is greatly reduced by increasing the spacing. As a result, it is possible to obtain an effect that it is possible to avoid a disadvantage that the cover does not open or becomes difficult to open.

[Brief description of the drawings]

FIG. 1 is a plan view of a closed switchboard showing an embodiment of the present invention.

FIG. 2 is a perspective view of a closed switchboard showing another embodiment of the present invention.

FIG. 3 is a perspective view of a conventional closed switchboard showing a box, a door, and a conductor installed in the switchboard that constitute the switchboard;

4 is a plan view of the conventional closed switchboard shown in FIG. 3 as viewed from above.

[Explanation of symbols]

 2 Box 3 Steel frame 4 Steel door 5 Hinge 6 Conductor 7 Current direction 8 Magnetic field direction 10 Magnetic flux passing through air 11 Magnetic flux passing through steel 12 Non-magnetic spacing material

Claims (3)

[Claims] 1. A box made of a ferromagnetic material having a front part, a rear part, or a side part, which is partially or wholly open, made of a ferromagnetic material. In a closed switchboard having a configuration in which the opening of the body is closed with a cover made of a ferromagnetic material, a spacing member having a predetermined thickness made of a nonmagnetic material is interposed between the box and the cover. Closed switchboard featured. 2. The closed switchboard according to claim 1,
A closed switchboard, wherein the spacing member is interposed all around the cover. 3. The closed switchboard according to claim 1,
A closed switchboard, wherein the spacer is intermittently interposed around the cover.