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(11) | EP 0 056 632 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Circuit interrupter |
| (57) A circuit interrupter includes a cylindrical container (5) having an arcuate inner
wall of electrically insulating material and containing an arc extinguishing fluid.
A rotary shaft (7) is provided along an axis of the container (5), at least one stationary
contact (3 or 4) is provided at a predetermined position on the inner wall, and a
movable contact (6) is mounted on the rotary shaft (7) in such manner as to be brought
into and out of engagement with the or each stationary contact. A closing member (15)
is disposed at one end of the opening movement path of the movable contact (6) and
substantially closes the clearance between the inner wall and the rotary shaft (7)
and, when the interrupter is opened, sweeps along the inner wall of the container
(5) towards the closing member (15) to compress the arc extinguishing fluid between
the two members (15, 16). The compressing member (16) has a blow outlet (18) which
causes the compressed fluid to blow into the space where arcs are generated upon cpening
of the interrupter. |
BACKGROUND OF THE INVENTION
[0002] A conventional interrupter of this type is shown in Fig. 1, and-comprises an input terminal 1, an output terminal 2, stationary contacts 3 and 4, a container 5, a movable contact 6, a rotary shaft 7, and a sealing member 13 for preventing fluid leakage. Reference character A designates a pressure generating contact region, and B an interrupting contact region. The operation of the interrupter is effected according to a system in which, similar to an oil interrupter or an SF6 gas interrupter, in addition to arcs to be extinguished, pressure generating arcs are formed. The pressure generated by the formed arcs is utilized to blow the fluid against the arcs to be extinguished. That is, this conventional interrupter constitutes a kind of self-extinguishing chamber. Accordingly, when a large current is interrupted the pressure generated is large, as a resul.t of which a large amount of arc extinguishing fluid is caused to flow to thus positively extinguish the arcs. However, such an interrupter is disadvantageous in that, when the current to be interrupted is smaller than a certain value, the pressure generated is small, and accordingly it takes a relatively long time to extinguish the arcs or sometimes it is impossible to extinguish them.
[0003] An object of this invention is to provide an interrupter in which can be reliably extinguished even with relatively small currents.
[0004] The foregoing object has been achieved by the provision of an interrupter which comprises a container having an arcuate inner wall made of an insulating material and containing an insulating fluid such as SF6 gas, a rotary shaft extending along the central axis of the container, stationary contacts disposed at predetermined positions on the inner wall, and a movable contact mounted on and turnable with the rotary shaft to be brought into and out of engagement with the stationary contacts. A closing member is provided near the end of the opening movement path of the movable contact and substantially closes the clearance between the inner wall and the rotary shaft, and a compressing member extends radially from the rotary shaft to sweep along the inner wall of the container towards the closing member when the interrupter is opened to compress the arc extinguishing fluid between the closing and compressing members. The compressing member has a blow outlet cut therein so that the compressed arc extinguishing fluid is caused to blow against the arc space through the outlet.
[0005] In conventional puffer type of interrupter a piston and cylinder are utilized. In the interrupter of this invention, however, the closing member serves as a stationary puffer plate while the compressing member serves as a movable puffer plate. The construction of the interrupter of this invention is thus comparable to and suitable as a rotary switch. It has a positive interruption capability which is independent of the current level, and yet can be manufactured at a relatively low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] In the accompanying drawings:
Fig. 1 is a sectional view of a conventional interrupter;
Fig. 2 is a sectional view of a first embodiment of an interrupter according to this invention;
Figs. 3(A), 3(B) and 3(C) are sectional views taken along line III-III in Fig. 2; and
Figs. 4 through 7 are explanatory diagrams showing the essential components of other embodiments of the interrupter according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS .
[0007] A first embodiment of an interrupter according to this invention is shown in Figs. 2 and 3, and comprises an input terminal 1, an output terminal 2, stationary contacts 3 and 4 provided at predetermined positions on the arcuate inner wall 50 of a container 5 made of insulating material, a movable contact 6 mounted on a shaft 7 located along the central axis of the container 5 such that the contact 6 is brought into and out of engagement with the stationary contacts 3 and 4 as it is rotated about the shaft 7, an energizing mechanism output wheel 8, an energizing mechanism input wheel 9, an upper bearing frame 10, a lower bearing frame 11, ball bearings 12, gas seals 13, and 0-rings 14. The interrupter further comprises a closing member or wall 15, a split or two part compressing member 16, an energizing spring 17, and a blow outlet 18. The closing member 15 is provided near the end of movement of the movable contact which is moved in opening the interrupter, and substantially closes the space between the inner wall 50 and the rotary shaft 7. The compressing member 16 protrudes from the rotary shaft 7.
[0008] When the interrupter is opened the compressing member 16 is rotationally advanced along the inner wall 50 of the container towards the closing member 15 to compress the arc extinguishing fluid between the closing member and the compressing member. The blow outlet 18 allows the arc extinguishing fluid compressed by the member 16 to flow into the arc space. The container 5 may be a cylinder of insulating material.
[0009] Fig. 3(A) shows the interrupter in the "on" state, Fig. 3(B) shows it being opened, and Fig. 3(C) shows it in the "off" state.
[0010] In operation, the energizing spring 17 is extended by turning the input wheel 9 through a predetermined angle. Upon disengagement of a latch (not shown) the output wheel 8 - starts rotation quickly. As a result the shaft 7 connected to the output wheel 8 is rotated so that the movable contact 6 is disengaged from the stationary contacts 3 and 4 to generate arcs. At the same time the compressing member 16 is rotated together with the shaft 7 to approach the closing member 15 so that the arc extinguishing fluid between these members is gradually compressed while the gas decomposed by the arcs expands, as a result of which the arc extinguishing medium is caused to blow into the arc space through the blow outlet 18, as shown by the broken tail arrows in Fig. 3(B). The dielectric strength in the space where the arcs have been generated is therefore quickly restored after the current passes through the zero point, thus withstanding the restriking voltage which occurs immediately after the interruption and extinguishing of the arcs. The movable contact 6 is further rotated to the final open position of the interrupter as shown in Fig. 3(C) to complete the interruption sequence.
[0011] To facilitate and maximize the above-described operation the container 5 is completely closed by the upper and lower bearing frames 10'and 11, the gas seals 13 and the 0-rings 14. Furthermore, the compressing member 16 is shaped so that it lies as close to the inner wall of the container as possible with the exception of the clearance formed between the compressing member and the contacts, so that it can smoothly turn whereby leakage of the arc extinguishing fluid is minimized. The closing member 15 is also designed so that it lies as close to the outer wall of the rotary shaft 7 as possible but without restricting the shaft from smoothly turning., so that leakage of the arc extinguishing fluid is further minimized.
[0012] A second embodiment of the invention is shown in Fig. 4, wherein the interrupter is substantially semicircular in section. In this embodiment the closing member 15' is configured as a flat wall of the container.
[0013] Fig. 5 is a sectional view showing the essential components of a third embodiment, wherein the container is divided into three equal parts to interrupt three-phase circuits. Accordingly, the interrupter has three compressing members and closing members.
[0014] In the above embodiments when the movable contact 6 rests on the stationary contacts 3 and 4, the movable contact forms an angle e with the compressing member 16 as shown in Fig. 3(A), so that during interruption the mechanical action of the compressing member and the heat of arcs. generated in the chamber R contribute to the compression of the arc extinguishing fluid in the chamber. The invention is not limited to such a disposition, however, and in some circumstances the angle 6 may be reduced to zero as shown in the embodiments of Figs. 6 and 7.
[0015] In each of the above embodiments a pair of stationary contacts 3 and 4 are provided for each movable contact 6. If the current is allowed to flow to the rotary shaft through the stationary contact 3 and the movable contact 6, however, and an output terminal electrically engaging the rotary shaft is employed, then the stationary contact 4 can be omitted.
1. A circuit interrupter, comprising: a container (5) having an inner wall (50) made
of an electrically insulating material and containing an arc extinguishing fluid;
and a stationary contact (3 or 4) provided on said inner wall (50); characterized
in that said inner wall (50) is arcuate; in that a rotary shaft (7) is provided along
an axis of said container (5); in that a movable contact (6) is provided on said rotary
shaft (7) in such a manner that said movable contact (6) is rotatable through an angular
path into and out of engagement. with said stationary contact; in that a closing member
(15) is disposed at one end of said path substantially to close a clearance between
said inner wall (50) and said rotary shaft (7); and in that a compressing member (16)
extends from said rotary shaft (7) and during opening of the interrupter is turned
along the inner wall (50) of said container (5) towards said closing member (15) to
compress the arc extinguishing fluid between said closing member (15) and said compressing
member (16), said compressing member (16) having a blow outlet (18) to allow said
arc extinguishing fluid to blow into a space where an arc occurs upon opening of the
interrupter.
2. An interrupter as claimed in claim 1, characterized in that at least a portion
of said container (5) is cylindrical.
3. An interrupter as claimed in claim 1 or -2, characterized in that said compressing
member (16) extends radially from said rotary shaft (7) at an acute angle with respect
to a radial line connecting the center of said shaft (7) and said movable contact
(6), in a trailing or lagging direction with respect ct the direction of opening rotation
of said shaft (7).
4. An interrupter as claimed in any one of claims 1 to 3, characterized in that said
closing member (15) extends from said inner wall (50) of said container (5) into close
abutment with said rotary shaft (7).
5. An interrupter as claimed in claim 4, characterized in that plurality of interrupting
units are provided in said container.
6. An interrupter according to any one of the preceding claims, characterized in that
two stationary contacts (3, 4) are provided on said inner wall (50) and in that said
movable contact (4) is rotatable into and out of engagement with both contacts substantially
simultan- eously.
7. An interrupter according to any one of claims 1 to 4, characterized in that a single
stationary contact ( 3 or 4) is provided on said inner wall (50) and in that said
shaft (7) is employed as a further contact.