JP2881794B2 - Magnetically driven electrodes for vacuum interrupters - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetically driven electrode for a vacuum interrupter that magnetically drives and interrupts an arc.

B. Summary of the Invention The present invention relates to a magnetic drive type vacuum interrupter electrode, in which the outer diameter of the contact surface is substantially equal to the diameter of the lead rod, and the current path formed between the contact surface and the lead rod is Of the current components, the current component in the direction perpendicular to the contact surface is made larger than that parallel to the contact surface, and the spiral groove of the arc part is extended to the contact part side, thereby preventing arc concentration at the time of interruption In addition, the arc is moved from the contact portion to the arc portion by the self-diffusion force of the arc due to the metal vapor, and the arc is rotated and cut off in the arc portion.

C. Prior Art Generally, a vacuum interrupter is, as shown in FIG.
In a vacuum vessel 1, a fixed lead rod 3 having a fixed electrode 2 and a movable lead rod 5 having a movable electrode 4 and capable of moving up and down are provided. In the figure, reference numeral 6 denotes a bellows which makes the movable lead rod 5 movable, and 7 denotes a shield which covers the inner periphery of the vacuum vessel 1.

The electrodes 2 and 4 of such a vacuum interrupter are required to have various electrical characteristics such as a large current breaking ability characteristic, a low breaking current value characteristic, and a high withstand voltage value characteristic.

However, these properties are of opposite nature and it is difficult to achieve them all at the same time. Therefore, conventionally, an electrode material is selected with an emphasis on one of the characteristics depending on the use of the vacuum interrupter, or a special electrode structure is adopted.

Under such circumstances, a magnetic drive type electrode is known as a representative example for further improving the current breaking performance with the same electrode diameter.

An example of a magnetically driven electrode is shown in FIGS. 7 and 8. As shown in the figure, this electrode 8 is provided with a contact portion 11 at a central portion on one surface side of an arc portion 10 provided with a plurality of spiral grooves 9 and a lead bar 12 connected to the other surface side of the arc portion 10. By driving the arc in the outer peripheral direction by the magnetic driving force and preventing extreme heating of the electrode,
It is intended to increase the cutoff limit.

Since the electrode 8 is intended to rotate the arc, various attempts have been made so that the generated arc moves until the current reaches a zero point without stagnation.

That is, after the arc 13 is generated in FIG. 7, the arc 13 moves on the arc pedal 10a as follows. At this time, the arc 13 collects successively generated arcs and rotates as an arc column 13 '.

The driving force of the arc 13 is the magnetic force F generated by the U-shaped current path generated in the electrode portion due to the component of the current Ih generated in the radial direction of the electrode 8 in FIG.

Therefore, conventionally, in order to generate a large magnetic force F, a: the inner diameter of the contact portion 11 is made larger than the diameter of the lead rod 12, b: a high resistance material (SUS steel) is formed on the upper part of the lead rod 12. C: extending the inner end of the spiral groove 9 below the contact portion 11 as shown by 9a in FIG. 7 to lengthen the arc pedal 10a. For the rotational movement of the arc, a: The tip of the arc pedal 10a is lengthened as shown by 10b in FIG. 7 to make it easier for the arc to move to the adjacent pedal. B: The gap dimension with the surrounding arc shield Take measures such as

D. Problems to be Solved by the Invention The idea of a conventional electrode taking the above-described means is
A magnetic driving force by a so-called U-shaped force is quickly applied to the generated arc 13. Therefore, the movement of the arc 13 is such that the arc 13 generated at one point grows as described above, and the generated arcs are collected one after another and rotated as a large arc column 13 '.

However, even though the arc rotates, the magnetic driving force acting on the arc toward the outer periphery of the electrode acts on the arc, so that the rotation of the arc ends only at a part of the electrode surface, and the entire electrode surface is removed. Not used effectively.

Therefore, the breaking performance corresponding to the electrode diameter cannot be obtained, and as described above, the performance can be improved by taking measures such as lengthening the spiral groove 9, lengthening the arc pedal 10, and providing the blowout ring 14. However, there is a limit, and in particular, the above method causes another problem that durability is reduced.

FIG. 9 shows the relationship between the electrode diameter and the current breaking performance of a conventional electrode. The drawing also shows a vertical magnetic field application type electrode. As can be seen from the figure, in the magnetic drive type electrode, when the electrode diameter exceeds a certain size,
No improvement in blocking performance can be expected.

In particular, when the breaking current is 50 kA or more, the arc energy becomes large. Therefore, local concentration of the arc cannot be prevented only by the magnetic driving force, and the breaking performance hardly increases when the electrode diameter is 110 to 120 mm or more.

Further, in the case of a vacuum interrupter having a rated voltage of about 12 kV, the distance from the external wiring (indicated by “l” in FIG. 10)
Is about 250 to 350 mm, and the value of the electromagnetic force is about 20 Gauss / kA
mm (magnetic flux density / current / arc length), magnetic driving force F is 10gf
/ kAmm, especially when the arc is arc pedal 10a
In the case where the arc is located near the outer periphery (the position shown in FIG. 7), it becomes difficult for the arc to move in the circumferential direction, and the breaking performance is reduced.

As described above, there was a limit to the improvement of the breaking performance due to the outward magnetic driving force.Therefore, the present inventors returned to the origin and contacted the arc generated by the self-diffusion force of the metal vapor generated at the time of breaking. Tried to be able to move from the part to the arc part.

That is, the electrodes were configured so that the outward magnetic driving force was minimized. Specifically, assuming that the outer diameter of the lead rod and the outer diameter of the contact surface are substantially equal, the current path between the lead rod and the contact surface is orthogonal to the contact surface (shown by a in FIG. 11). ) Is made the majority, and consideration is given to minimizing the component in the direction parallel to the contact surface (shown by B in FIG. 1).

A vacuum interrupter was assembled using this electrode, and its breaking performance was tested.
A 30% improvement was obtained. Moreover, when the electrode after the test was disassembled and the electrode surface was observed, there was no local erosion, and traces of arc were found on almost the entire electrode surface (in the conventional one, local erosion was observed). . From this, it was found that the entire electrode surface was effectively used.

In addition, the inner wall of the shield of the vacuum interrupter
The occurrence of burrs was also small. This indicates that reduction in breakdown voltage after interruption can be prevented, and as a result, an increase in the number of interruptions of large current can be expected.

Therefore, good results can be obtained by moving the arc from the contact portion to the arc portion by the self-diffusion force of spontaneous instead of forcibly driving the generated arc by the outward magnetic force as in the conventional case. Turned out to be.

On the other hand, in order to smoothly move the arc from the contact portion to the entire arc portion by the self-diffusion force, it is necessary that the arc generated at the contact portion is not concentrated.

However, the arcs generated at multiple points are concentrated by the sneak current indicated by the arrow B in FIG. 7, the arcs become thicker, effective diffusion by the self-diffusion force cannot be performed, and the erosion of the contact portion and the arc portion also occurs. It is local and grows big.

E. Means for Solving the Problems Based on the above findings, in the present invention, a contact portion having a ring-shaped contact surface is provided at the center of one surface of an arc portion having a plurality of spiral grooves, and the other surface is provided. In a magnetically driven electrode for a vacuum interrupter having a lead rod connected to the center of the electrode, at least a current component in a current path formed between the contact surface and the lead rod at the time of energization is orthogonal to the contact surface. When the component in the direction is Iv, and the component in the direction parallel to the contact surface is Ih, the contact portion, the arc portion, and the lead rod are connected and configured so that Iv> Ih, while the inner end of the spiral groove is It extended to the contact portion.

The contact portion is made of a material containing chromium and copper as main components, for example, a composite metal of Cu-Cr-Mo is adopted.

The arc portion is made of a magnetic material and a material containing copper as a main component, and a composite metal of Fe-Cr or magnetic stainless steel-Cu is employed.

Further, as a structure in which the inner end of the spiral groove is extended to the contact portion, the spiral groove is connected to the inner end of the spiral groove and opened to the surface of the contact portion to form a groove. However, the one extended to the back part of the contact part corresponds to this.

F. Function The above-mentioned electrode for vacuum interrupter
Since the sneak current is suppressed due to the resistance of the groove of the contact part, dispersion occurs without causing arc concentration, each arc moves from the contact part to the arc part by the self-diffusion force of the generated metal vapor, In the arc portion, the entire rotation is performed, and the cutoff is performed by effectively using the electrode surface.

G. Embodiment FIG. 1 shows a plane view of an electrode for a vacuum interrupter according to an embodiment of the present invention, and FIG. 2 shows a cross section taken along the line II-II.

The arc portion 21 has a disk ring shape, and has a number of spiral grooves 22 formed from near the inner peripheral surface at the center to the outer peripheral surface.

A concave portion 23 is formed in the inner peripheral portion on the surface side of the arc portion 21, and a ring-shaped contact portion 24 is fitted into the concave portion 23 and brazed to the arc portion 21. The inner diameter of the contact portion 24 and the inner diameter of the arc portion 21 are substantially equal. The contact portion 24 is formed with a number of extension grooves 25 connected to the inner ends of the spiral grooves 22 of the arc portion 21. actually,
After integrating the arc portion 21 and the contact portion 24, the spiral groove 22 and the extension groove 25 are formed at a stretch by NC cutting or the like.

A lead rod 26 is brazed to the center of the back side of the arc portion 21. The outer diameter of the lead rod 26 and the outer diameter of the contact portion 24 are substantially equal.

As described above, by connecting and connecting the arc portion 21, the contact portion 24, and the lead rod 26, the contact surface 24a of the contact portion 24 (the contact portion 24
Direction perpendicular to the contact surface 24a in the current path formed between the lead bar 26 and the current path (the direction indicated by a in FIG. 11).
Can be made larger than the current amount in the direction parallel to the contact surface 24a (the direction indicated by b in FIG. 11). Moreover,
An extension groove 25 is formed in the contact portion 24 so that the contact portion 24 has a narrow area e.
In other words, the extension groove 25 is provided so that the current path in the circumferential direction is small, so that the circumferential resistance at the contact portion 24 is large. As a result, arc concentration can be prevented.

As shown in FIGS. 3 and 4, the extension groove 25 may be extended to the back surface of the contact portion 24 without opening the contact surface 24a. The point is that a portion that becomes a resistance to the flow of the current may be connected to the spiral groove 22 in the circumferential direction of the contact portion 24.

In the electrode, a reinforcing plate 27 made of stainless steel, Inconel, or the like is provided on the back surface of the arc portion 21.

In this embodiment, the contact portion 24 has an outer diameter of 40 mm and an inner diameter of 20 mm.
Thus, it is formed by infiltrating Cu into a porous sintered body of Mo—Cr.

The arc portion 21 has an outer diameter of 80 mm, the number of spiral grooves (= the number of arc pedals 30 a) is 12, the width of the spiral groove 29 is 4 mm, and F
Cu (50%)-Fe (42) in which Cu is infiltrated into a porous sintered body of e and Cr
%)-Cr (8%).

As shown in FIG. 5, the electrodes having the above-described configuration are fixed electrodes 28,
FIG. 6 shows the results of a test conducted on the current interrupting performance by changing the electrode diameter by forming a vacuum interrupter as the movable electrode 29. In FIG. 5, constituent members of the vacuum interrupter are the same as those shown in FIG. 10, and the same members are denoted by the same reference numerals. The test conditions were a voltage of 12 kV,
The gap between the electrodes is 12 mm.

An extension groove 25 is formed in the contact portion 24 of the electrodes 28 and 29 so that the contact portion 2
Since the resistance along the circumferential direction of 4 is increased, arcing that occurs at multiple points during current interruption is prevented from being concentrated. Therefore, arcs are generated and dispersed at multiple points. That is, the generated arc is prevented from becoming thick as before. The dispersed arc spreads in the radial direction due to the self-dispersing force of the metal vapor, moves from the contact portion 24 to the arc portion 21, and is rotated and extinguished by the spiral groove 22 of the arc portion 21. In FIG. 1, the movement of the arc is illustratively shown by an arrow A at only one point.

As a result of the test, the breaking performance of the vacuum interrupter using the electrode of the present invention (indicated by-in FIG. 6) was 10 to 10 times smaller in each diameter than that of the conventional product (indicated by x-x in FIG. 6).
Very good results were obtained even with a large diameter of 120 mm, which is 30% better.

H. Effects of the Invention The magnetically driven electrode for a vacuum interrupter according to the present invention is:
When the current component in the current path formed between the contact surface of the contact portion and the lead rod at least at the time of energization, the component in the direction perpendicular to the contact surface is Iv, and the component in the direction parallel to the contact surface is Ih. , Iv> Ih so as to connect the contact portion, the arc portion, and the lead bar, while extending the inner end of the spiral groove to the contact portion, when the current is interrupted, the arc is dispersed and generated. Since the metal vapor moves to the entire area of the arc due to its self-diffusion force, and the entire arc rotates to extinguish the arc, the breaking performance is improved, and the electrode surface can be used effectively. As a result, the size of the vacuum interrupter can be reduced. Also, since the arc is a dispersed arc, the erosion of the contact portion is small, and each generated arc is moved over the entire arc portion by self-diffusion, so that the erosion of the arc portion is also small. Furthermore, since the generation of the dirt and burrs of the shield of the vacuum interrupter is suppressed, the withstand voltage can be improved and the number of times of interrupting the large current can be increased.

[Brief description of the drawings]

FIG. 1 is a plan view of a vacuum interrupter electrode according to one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line II-II, and FIGS. 3 and 4 are other embodiments. FIG. 5 is a plan view of the electrode according to the present invention and a cross-sectional view taken along the line IV-IV in the direction of the arrow, FIG. 5 is a vertical cross-sectional view of a vacuum interrupter having the electrode according to the embodiment, and FIG. Graph showing the relationship of the seventh
The figure is a plan view of a conventional magnetically driven electrode, and FIG.
9 is a graph showing the relationship between the electrode diameter of the conventional electrode and the breaking performance, FIG. 10 is a schematic diagram of a vacuum interrupter, and FIG. 11 is an explanatory diagram of a current path. In the drawing, 21 is an arc portion, 22 is a spiral groove, 24 is a contact portion, 24a is a contact surface, 25 is an extension groove, and 26 is a lead rod.

Claims (1)

(57) [Claims] A vacuum interrupter comprising: an arc portion having a plurality of spiral grooves; a contact portion having a ring-shaped contact surface provided at the center of one surface; and a lead bar connected to the center of the other surface. In the magnetically driven electrode for use, when closing current is applied, the arc portion is formed in a ring shape having a hole in the center so that a current parallel to the contact surface is not generated in the lead bar, the arc portion and the contact portion, The inner diameter of the contact portion provided at the center of the arc portion is made equal to the inner diameter of the hole, and the outer diameter of the contact portion is made equal to the outer diameter of the lead rod. The arc portion is made of a material containing a magnetic material while the tip of the lead rod is fitted and connected to the hole so as not to come into direct contact with the inner surface of the spiral groove. To the department Vacuum interrupter magnetic drive type electrode, characterized in that.