JP7175802B2 - vacuum circuit breaker - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum circuit breaker that cuts off current by separating contacts in a vacuum space.

Conventionally, a vacuum circuit breaker has been used in which a pair of separable electrodes are provided in a vacuum container, and an arc generated between the electrodes during current interruption is extinguished in vacuum (see Patent Document 1). Vacuum circuit breakers are required to improve breaking performance so that they can break high voltages and large currents in substation equipment and power receiving/distribution equipment. There is also a need for a vacuum circuit breaker as a clean device that can be operated without using an insulating gas with a large global warming potential.

JP-A-2003-92050

Dielectric breakdown (arc generation) between electrodes when current is interrupted in a vacuum circuit breaker can be explained based on the Paschen curve. FIG. 12 is a graph of the Paschen curve. In the graph of the Paschen curve in FIG. 12, the horizontal axis is atmospheric pressure×gap length, and the vertical axis is dielectric breakdown voltage (insulation strength). In the Paschen curve, it is known that if the gap length×atmospheric pressure on the horizontal axis at which the minimum value Vmin of the dielectric breakdown voltage is obtained is further reduced, the dielectric breakdown voltage rises sharply.

Under the vacuum pressure handled by the vacuum circuit breaker (for example, about 10 ⁻⁴ Pa or less), dielectric breakdown occurs under the condition of a value smaller than the value on the horizontal axis where the dielectric breakdown voltage is the minimum value Vmin in the graph of FIG. do. Also, since the air pressure becomes a vacuum and is substantially constant, the value of air pressure×gap length on the horizontal axis changes according to the gap length, and the breakdown voltage decreases as the gap length increases. Therefore, the region where the gap length is large is more likely to cause dielectric breakdown than the region where the gap length is small.

The inventor of the present invention studied the conditions under which dielectric breakdown occurs due to such a gap length, and studied the use of an electrode in which a concave portion is formed in the contact portion.

By the way, dielectric breakdown under vacuum in a vacuum circuit breaker is different from dielectric breakdown in the atmosphere in the atmosphere or in a gas atmosphere environment under high pressure. In a gas atmosphere environment, collision ionization between gas molecules and electrons accelerated by voltage advances electron multiplication, resulting in an electron avalanche and dielectric breakdown. On the other hand, under the vacuum pressure handled by the vacuum circuit breaker, the gas atmosphere is less, so the mean free path required for electrons to collide with gas molecules is remarkably long. This is the length at which electrons collide with the electrode without collision. Therefore, what triggers dielectric breakdown is electrons first generated by field electron emission from the cathode.

The present inventor considered that suppressing the generation of initial electrons due to such field electron emission is an important point in improving the insulation performance of a vacuum circuit breaker. Furthermore, as a result of various trials and errors, the present inventor conducted extensive research on the relationship between the suppression of initial electron generation due to field electron emission and the surface roughness of the contact portion. I devised an invention that can improve the insulation performance in

SUMMARY OF THE INVENTION It is an object of the present invention to provide a vacuum circuit breaker capable of improving insulation performance at a contact portion.

A vacuum circuit breaker according to one aspect of the present invention is a vacuum circuit breaker that includes a movable contact and a fixed contact that are provided in a vacuum vessel so that they can be brought into and out of contact with each other, and conduct electricity in a contact state and cut off electricity in a separated state. The electrode portions of the movable contactor and the fixed contactor have contact portions formed with opposing surfaces facing each other, and at least one of the opposing surfaces faces the other of the opposing surfaces in the contact state. It comprises a contact area that makes contact and a recess that is located at a greater distance from the other opposing surface than the contact area, and the bottom of the recess is formed to have a smaller maximum surface roughness (Rmax) than the contact area. It is characterized by

According to the present invention, since the contact portions of each contactor are separated under vacuum when the current is interrupted, the electric field can be concentrated on the side where the distance between the contact portions is long, that is, on the bottom of the concave portion, and the contact area can be reduced. It is possible to put the concave portion into a state in which it is easy to discharge. Furthermore, since the surface roughness of the concave portion is reduced, in other words, the surface roughness of the area where discharge is likely to occur is reduced, the generation of initial electrons due to field electron emission can be suppressed, and as a result, the insulation performance at the contact portion can be improved. can be done.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic block diagram which carried out the partial cross section view of the vacuum circuit breaker which concerns on 1st Embodiment. FIG. 2A is an explanatory view of the electrode portion of the fixed contact in the first embodiment as viewed from above. FIG. 2B is a vertical cross-sectional view of the contact portion taken along line AA of FIG. 2A. 3A and 3B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the second embodiment. 4A and 4B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the third embodiment. 5A and 5B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the fourth embodiment. FIG. 11 is an explanatory cross-sectional view of a contact portion according to a fifth embodiment; FIG. 11 is an explanatory cross-sectional view of a contact portion according to a sixth embodiment; 8A and 8B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the seventh embodiment. FIG. 20 is an explanatory cross-sectional view of a contact portion according to an eighth embodiment; FIG. 20 is an explanatory cross-sectional view of a contact portion according to a ninth embodiment; FIG. 20 is an explanatory cross-sectional view of a contact portion according to a tenth embodiment; It is a graph of a Paschen curve.

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments, and can be modified appropriately without changing the gist of the invention. In the following diagrams, part of the configuration may be omitted for convenience of explanation.

[First embodiment]
FIG. 1 is a schematic diagram showing a partial cross-section of a vacuum circuit breaker according to a first embodiment. As shown in FIG. 1 , the vacuum circuit breaker 10 includes a vacuum container 11 , and a movable contactor 12 and a fixed contactor 14 that are detachably provided inside the vacuum container 11 . In the vacuum circuit breaker 10, the movable contactor 12 and the fixed contactor 14 are energized (closed) when they are in contact (not shown), and energized (opened) when they are separated as shown in FIG.

The vacuum container 11 includes an insulating cylinder 15 made of ceramic or the like, and end plates 16 and 17 provided to close the upper and lower ends of the insulating cylinder 15 in FIG. A movable contactor 12 is provided through the upper end plate 16 so as to be vertically movable. A fixed contact 14 is fixed to the lower end plate 17 .

The movable contactor 12 is provided with a movable rod 19, and the movable rod 19 is movable in the axial direction (vertical direction) while maintaining the vacuum state in the vacuum container 11 via an airtight member (not shown) such as a bellows. provided in The movable-side rod 19 is connected to a breaking spring 20 that functions as a tension spring. contacts and is energized. From this state, by operating a latch or the like, the movable rod 19 is moved upward by the restoring force of the breaking spring 20 to move the movable contact 12 away from the fixed contact 14, thereby cutting off the energization.

The fixed contact 14 has a fixed rod 22 fixed via a fixed block 23 attached to the lower end plate 17 .

The movable contact 12 has an electrode portion 30 at one end (lower end in FIG. 1) of the movable rod 19 . The fixed contact 14 has an electrode portion 40 at one end (upper end in FIG. 1) of the fixed rod 22 . In the present embodiment, the electrodes 30 and 40 are vertically symmetrical and arranged to face each other. A shield 25 is provided outside each of the electrode portions 30 and 40 to protect the inner peripheral surface of the insulating cylinder 15 .

The electrode portions 30 and 40 include electrode body portions 31 and 41 having a cylindrical outer shape and disk-shaped contact portions 32 and 42 connected to the ends of the electrode body portions 31 and 41 by brazing or the like. ing. The upper surface of the contact portion 42 of the fixed contactor 14 is formed as a facing surface 43, and faces the facing surface 33, which is the lower surface of the contact portion 32 of the movable contactor 12, mutually.

A plurality of (six in the present embodiment) inclined slits 34 and 44 are formed in the electrode main body portions 31 and 41 so as to extend spirally while being inclined with respect to the axis thereof. The inclined slits 34 and 44 are formed at a predetermined depth from the outer peripheral surfaces of the electrode main bodies 31 and 41 . Slits 35 and 45 are formed in the contact portions 32 and 42, one ends of which are formed at the outer peripheral edges thereof, and the one ends of the slits 35 and 45 and the upper ends of the inclined slits 34 and 44 are formed so as to be continuous.

FIG. 2A is a top view of the electrode portion of the fixed contact according to the first embodiment. FIG. 2B is a vertical cross-sectional view of the contact portion of the stationary contact, taken along line AA of FIG. 2A. As shown in FIGS. 2A and 2B, the opposing surface 43 of the contact portion 42 of the stationary contactor 14 has a contact region 47 formed in an annular shape with a predetermined width along the outer peripheral edge thereof, and an in-plane contact region 47 . A concave portion 48 is formed on the center side. By forming the contact area 47 and the recess 48 , the distance of the recess 48 from the facing surface 33 (see FIG. 1 ) of the movable contactor 12 is longer than that of the contact area 47 . A contact area 47 is an area of the facing surface 43 that contacts the facing surface 33 of the movable contact 12 when energized (closed).

Here, the bottom portion 48a (the dotted area in FIG. 2A) inside the concave portion 48 has a smaller maximum surface roughness (Rmax) than the contact area 47 and is formed as a smooth surface. For example, the maximum surface roughness Rmax of the bottom portion 48a is 0.25 μm, and the maximum surface roughness Rmax of the contact region 47 is 8 μm.

A plurality of slits 45 (six in this embodiment) are formed in the contact portion 42 and extend from one end of the outer peripheral edge of the contact portion 42 to the bottom portion 48a of the concave portion 48 which is inward. The other end (inner end) of the slit 45 is formed so as to be located on the bottom portion 48 a inside the boundary between the contact area 47 and the recess 48 . Although not shown, in the contact portion 32 of the movable contactor 12, the slit 35 has the same shape as the slit 45, although the facing surface 33 does not have a concave portion. Due to the slits 35, 45 and the inclined slits 34, 44, the conducting path of the electrode parts 30, 40 becomes coiled, generating a vertical magnetic field (a magnetic field in a direction parallel to the vertical direction in FIG. 1), thereby improving the cut-off characteristics. become.

In the present embodiment, the facing surface 33 of the contact portion 32 of the movable contactor 12 is formed as a flat surface except for the area where the slits 35 are formed, and the entire facing surface 33 serves as the contact area.

In the vacuum circuit breaker 10, in the energized state where the movable contact 12 and the fixed contact 14 are in contact with each other, the contact area 47 of the fixed contact 14 and the facing surface 33 of the movable contact 12 at a position opposite thereto come into contact. . On the other hand, in the interrupted state, the facing surface 33 of the movable contactor 12 faces the contact area 47 and the bottom portion 48a of the recessed portion 48 of the fixed contactor 14 in a non-contact state separated by a predetermined distance.

When the contact portions 32, 42 of the fixed contact 14 and the movable contact 12 are separated from each other in order to interrupt the current from the energized state in the vacuum circuit breaker 10, an arc is generated between the contact portions 32, 42. .

Immediately after the opposing surface 33 and the contact area 47 that are in contact with each other are separated from each other at the contact portions 32 and 42 when the current is interrupted, the opposing surface 33 and the bottom portion 48a of the recess 48 becomes larger. Based on the explanation of the Paschen curve (see FIG. 12), the bottom 48a of the concave portion 48, which is separated from the facing surface 33, is more likely to be discharged, and an arc is selectively generated. In other words, it is possible to suppress the arc from being generated in the contact area 47, and to stably create a state in which dielectric breakdown is possible at the bottom 48a of the recess 48. FIG.

In addition, since the surface roughness of the bottom portion 48a of the concave portion 48 is reduced, the surface roughness of the portion where dielectric breakdown occurs can be reduced, and the generation of initial electrons due to the field electron emission described above can be suppressed at the bottom portion 48a. can. As a result, the dielectric breakdown is less likely to occur, and the dielectric breakdown voltage can be maintained at a high value to improve the insulation performance between the facing surface 33 and the bottom portion 48 a of the recess 48 , and the breaking performance of the vacuum circuit breaker 10 . can be improved.

Here, when the current is interrupted, macroscopic electric field concentration occurs at the edge portions of the slits 35 and 45 for generating the vertical magnetic field. Since the slit 45 of the fixed contact 14 is formed in both the bottom 48a of the recess 48 and the contact region 47, electric field concentration occurs at the edge of the slit 45 located in the bottom 48a where discharge is more likely to occur, resulting in dielectric breakdown. become. As a result, dielectric breakdown can be prevented in the contact area 47 and stable dielectric breakdown can occur in the recess 48, thereby improving the insulation performance (dielectric breakdown voltage).

According to the first embodiment as described above, by setting the maximum surface roughness Rmax of the bottom portion 48a small, the ultimate electric field strength can be increased. Although the ultimate electric field strength varies greatly depending on the electrode material, the degree of vacuum, the presence or absence of conditioning, and the processing conditions, it is about 1.5 μm depending on the change in the maximum surface roughness Rmax of the bottom portion 48a (for example, 2.5 μm and 0.8 μm). It is possible to increase about 7 times.

By the way, in the vacuum circuit breaker 10, the contact area 47 contacts or presses against the facing surface 33 of the movable contactor 12 during storage, distribution, or construction, and during testing before actual operation, each contactor 12, 14 may be repeatedly opened and closed. Even in this case, the bottom portion 48a of the concave portion 48 can be kept out of contact with the contact portion 32 of the movable contactor 12, and a good surface condition with a small maximum surface roughness can be stably maintained. can be ensured and the insulation performance described above can be maintained. In addition, the contact area 47 has a rougher surface than the bottom 48a of the recess 48, and the contact area 47 tends to be rougher even if tests and transportation are performed before actual operation. This relationship can be easily maintained.

Next, embodiments of the present invention other than those described above will be described. In the following description, the same reference numerals may be used for components that are the same as or equivalent to those in the embodiments described before, and the description may be omitted or simplified. In addition, in the drawings after FIG. 3, the halftone dot area similar to that in FIG. 2A is formed to have the same maximum surface roughness as that of the bottom portion 48a of the first embodiment.

[Second embodiment]
Next, a second embodiment of the invention will be described with reference to FIG. 3A and 3B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the first embodiment. As shown in FIGS. 3A and 3B, in the second embodiment, the shape of recess 48 is changed from that in the first embodiment.

In the second embodiment, the concave portion 48 is formed in a groove shape and is formed along the trajectory of one circle (closed loop) having the same center as the outer peripheral edge of the contact portion 42 . Also in the second embodiment, the other end (inner end) of the slit 45 is formed so as to be positioned at the bottom 48 a of the recess 48 . In addition, on the facing surface 43 of the contact portion 42 , not only the outer region of the recess 48 but also the inner region are formed as the contact region 47 . Also in the second embodiment, the bottom portion 48 a is formed as a smooth surface having a smaller maximum surface roughness (Rmax) than the contact area 47 .

[Third embodiment]
Next, a third embodiment of the invention will be described with reference to FIG. 4A and 4B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the third embodiment. As shown in FIGS. 4A and 4B, the third embodiment differs from the second embodiment in that the groove-shaped concave portion 48 is formed in two concentric circles. In the third embodiment, the other end (inner end) of the slit 45 is positioned at the bottom 48 a of the inner recess 48 of the double recesses 48 .

[Fourth embodiment]
Next, a fourth embodiment of the invention will be described with reference to FIG. 5A and 5B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the fourth embodiment. As shown in FIGS. 5A and 5B, the fourth embodiment is different from the second embodiment in that the groove-shaped recesses 48 are formed concentrically in three layers. In the fourth embodiment, the other end (inner end) of the slit 45 is positioned at the bottom 48 a of the outermost recess 48 among the triple recesses 48 . According to the second to fourth embodiments, even if the concave portion 48 is formed in a groove shape, it is possible to obtain the same effects as in the first embodiment. By changing the number of recesses 48 to be formed, it is possible to obtain a good balance between the effect of reducing the manufacturing cost and the effect of improving the insulation performance.

[Fifth embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 6 is an explanatory cross-sectional view of the contact portion according to the fifth embodiment. As shown in FIG. 6, in the fifth embodiment, the contact portion 32 of the movable contact 12 also has recesses similar to the recesses 48 in the contact portion 42 of the fixed contact 14, unlike the first embodiment. 38 is formed. In FIG. 6, the recesses 38 and 48 have the same size and shape when viewed from above, but the recesses 38 and 48 may have different sizes, shapes, and formation positions.

According to the fifth embodiment, the distance (gap length) between the bottoms 38a, 48a of the recesses 38, 48 can be increased, and stable insulation performance can be maintained even in a high electric field.

[Sixth embodiment]
Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 7 is an explanatory cross-sectional view of a contact portion according to the sixth embodiment. As shown in FIG. 7, in the sixth embodiment, the concave portion 38 in the contact portion 32 of the movable contactor 12 is changed from the fifth embodiment.

In the sixth embodiment, the concave portion 38 of the movable contact 12 is formed in a groove shape along a circular trajectory like the concave portion 48 of the second embodiment. In FIG. 7, the concave portion 38 of the movable contactor 12 is formed to be larger than the concave portion 48 of the fixed contactor 14, and is set at a position where they do not overlap vertically. According to the sixth embodiment, it becomes difficult for the parts to undergo dielectric breakdown to be the same, and the degree of freedom of the parts can be ensured.

[Seventh embodiment]
A seventh embodiment of the present invention will now be described with reference to FIG. 8A and 8B are explanatory diagrams similar to FIGS. 2A and 2B of the electrode portion according to the seventh embodiment. As shown in FIGS. 8A and 8B, in the seventh embodiment, the bottom 48a of the recess 48 is stepped to have a two-step height, unlike the first embodiment. . Note that the number of such steps may be increased as appropriate.

[Eighth embodiment]
Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG. 9 is an explanatory cross-sectional view of the contact portion according to the eighth embodiment. As shown in FIG. 9, in the eighth embodiment, the bottoms 38a and 48a of both recesses 38 and 48 are stepped to have a two-step height, unlike the fifth embodiment. is doing.

[Ninth Embodiment]
Next, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 10 is an explanatory cross-sectional view of a contact portion according to the ninth embodiment. As shown in FIG. 10, in the ninth embodiment, the bottoms 38a, 48a of both the recesses 38, 48 are provided with steps to provide two steps in height, unlike the sixth embodiment (see FIG. 7). It is formed into a shape having

[Tenth embodiment]
Next, a tenth embodiment of the present invention will be described with reference to FIG. FIG. 11 is an explanatory cross-sectional view of the contact portion according to the tenth embodiment. As shown in FIG. 11, in the tenth embodiment, the bottom portion 38a of the concave portion 38 in the movable contactor 12 is provided with a step to increase the height of two steps compared to the fifth embodiment (see FIG. 6). It is formed into a shape that has The recessed portion 48 of the fixed contact 14 is formed in a step-free shape as in the first and fifth embodiments.

By making the bottom portions 38a and 48a two steps high as in the seventh to tenth embodiments, the distance between the bottom portions 38a and 48a, which is the gap length, and the distance between the bottom portions 38a and 48a The distance between the facing surfaces 33 and 43 can be lengthened, and stable insulation performance can be maintained even in a high electric field.

It should be noted that the present invention is not limited to the above embodiments, and can be implemented with various modifications. In the above embodiments, the sizes, shapes, directions, etc. shown in the accompanying drawings are not limited to these, and can be changed as appropriate within the scope of exhibiting the effects of the present invention. In addition, it is possible to carry out by appropriately modifying the present invention as long as it does not deviate from the scope of the purpose of the present invention.

In each of the above embodiments, if the contact portion 32 of the movable contact 12 and the contact portion 42 of the fixed contact 14 are different in shape, size, formation position, and presence/absence of the concave portions 38 and 48, , the shapes of the contact portions 32 and 42 may be reversed. Furthermore, the shape of each recess 38, 48 when viewed from above is not limited to a circular shape or an annular shape, but may be an elliptical shape or a polygonal shape as long as the maximum surface roughness Rmax of the bottoms 38a, 48a is small. Various changes are possible, such as

Moreover, the slits 35 and 45 may be formed discontinuously in the extension direction as long as they generate the same vertical magnetic field as in the above embodiments. However, it is preferable that part of the slits 35, 45 be formed in the bottoms 38a, 48a of the recesses 38, 48 in order to generate macroscopic electric field concentration at the time of current interruption.

Further, in the electrode portions 30 and 40, the contact portions 32 and 42 and the electrode body portions 31 and 41 are separately fixed, but they may be integrally formed.

REFERENCE SIGNS LIST 10 vacuum circuit breaker 11 vacuum vessel 12 movable contact 14 stationary contact 30 electrode section 32 contact section 33 facing surface 35 slit 37 contact area 38 recess 38a bottom 40 electrode section 42 contact section 43 facing surface 45 slit 47 contact area 48 recess 48a bottom

Claims (3)

A vacuum circuit breaker comprising a movable contactor and a fixed contactor which are arranged to be contactable and detachable inside a vacuum vessel, are energized in a contact state, and cut off the energization in a separated state,
The electrode portions of the movable contact and the fixed contact include contact portions formed with facing surfaces facing each other,
At least one of the opposing surfaces includes a contact area that contacts the other opposing surface in the contact state, and a recess that is located at a distance from the other opposing surface that is greater than the contact area,
A vacuum circuit breaker according to claim 1, wherein the bottom of the recess is formed to have a maximum surface roughness (Rmax) smaller than that of the contact area. 2. The vacuum circuit breaker according to claim 1, wherein said contact portion has a slit for generating a vertical magnetic field on said facing surface. 3. The vacuum circuit breaker according to claim 2, wherein the slit extends from the outer edge of the contact portion to the bottom portion of the recess.

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