GB2042263A

GB2042263A - Improvements in or relating to circuit interrupters

Info

Publication number: GB2042263A
Application number: GB7904441A
Authority: GB
Original assignee: Terasaki Electric Co Ltd
Current assignee: Terasaki Electric Co Ltd
Priority date: 1979-02-08
Filing date: 1979-02-08
Publication date: 1980-09-17
Also published as: DE2905854A1; DE2905854C2; GB2042263B

Abstract

A circuit interrupter comprises a contact structure 16 including a pair of separable contacts 18, 24 connectable to an external circuit and enclosed in an electrically insulating enclosure 14, 58 to enable internal pressure within the enclosure to promote an increase in the arc voltage. An operating mechanism 36 is disposed externally of the enclosure 14, 58 for effecting contact opening and closing movements of the contact structure 16 and is electrically isolated by the enclosure 14, 58 from the contact structure 16. Means 50, 52 movably extending through the enclosure 14, 58 operatively interconnects the contact structure 16 and the operating mechanism 36 so as to transmit movements of the operating mechanism 36 to the contact structure 16. <IMAGE>

Description

SPECIFICATION Improvements in or relating to circuit interrupters This invention relates to circuit interrupters, and more particularly to air circuit interrupters.

Air circuit interrupters include a first type which has no insulating housing at all and a second type which has an insulating moulded housing enclosing the entire interrupter mechanism such as contact structures and operating mechanisms.

The first type of interrupter without housing is advantageous in that inspection and maintenance are easy and it is not expensive. However, the dielectric strength between the current carrying portion and the operating mechanism is relatively low and, especially when an electric arc is established bet ween the separated contacts, a leak current can sometimes flow to the operating mechanism. Also, since this type of the circuit interrupter does not include a housing, the gas pressure at the arcing region does not increase even upon arcing although an increased gas pressure at the arcing region is desirable because it increases the arc voltage. For these reasons, the first type of circuit interrupter without a housing is not suitable to handle a large interrupting current.

the second type of circuit interrupter has its current carrying portion and the operating machanism enclosed within an insulating housing, so that the pressure within the housing increases to a certain extent upon contact separation. However, since the entire mechanism including contact structure and the operating mechanism are all housed in a single housing, the housing is inevitably relatively large and it is difficult to achieve an efficient pressure rise effective for increasing the arc voltage. Also, the dielectric strength between the current carrying portion and the other conductive portion such as the operating mechanism is not very high. Moreover, the housing can cause problems for inspection and maintenance of the interrupter from the outside.

According to the invention, there is provided a circuit interrupter comprising a contact structure including a pair of separable contacts and being connectable to an external circuit, an electrically insulating enclosure substantially enclosing the contact structure to enable internal pressure within the enclosure to become effective in promoting an increase in the arc voltage, an operating mechanism disposed externally of the enclosure for effecting contact opening and closing movements of the contact structure and being electrically isolated by the enclosure from the contact structure, and means movably extending through the enclosure for operatively inter-connecting the contact structure and the operating mechanism so as to transmitthe movements of the operating mechanism to the contact structure.

A preferred circuit interrupter has a rated short circuit breaking capacity substantially greater than that of conventional air circuit interrupters with a relatively simple structure.

A preferred simple circuit interrupter exhibits a higher rated shorttime interrupting current capacity as compared to conventional circuit interrupters.

A preferred circuit interrupter has an insulating housing and yet is easy to inspect and maintain.

In a preferred circuit interrupter, the contact structure is substantially enclosed by an insulating housing so that, upon separation of the contacts, an electric arc established between the separated contacts raises the internal pressure within the arcing region defined by the housing to become effective in promoting an increase in the arc voltage.

The circuit interrupter may further comprise an arc extinguisher within the insulating housing. The arc extinguisher may include an arc extinguishing chamber containing a plurality of arc grids, an arc gas mixing chamber and an arc gas cooling grid. The arc extinguisher may be disposed within an arc extinguisher cover made of an insulative material and detachably mounted to the housing body. The interconnecting means between the contact structure and the operating mechanism may comprise a flange which covers off an opening in the housing through which the interconnecting means extends.

When the circuit interrupter is of the multipole unit type, the insulating housing can be an integrally formed housing provided with a plurality of pole unit chambers, therein, or an assembly assembled from separate pieces.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which: Figure lisa sectional side view of a circuit interrupter constituting a preferred embodiment of the present invention, with its contact structure and operating mechanism in their open positions; Figure 2 is a sectional side view of a part of the interrupter shown in Figure 1 with the contact structure in its closed position; and Figure 3 is an exploded perspective view of the insulating housing and the mould base used in the circuit interrupter shown in Figures 1 and 2.

A circuit interrupter 10 comprises a metal frame 12, a moulded base 14 secured to the metal frame 12, and a contact structure 16 mounted on the base 14. The contact structure 16 comprises a stationary main contact 18 and a stationary arcing contact 20, both mounted on and electrically connected to a source terminal 22 secured and extending through the mould base 14 for connection to an external cir cuit (not shown). The contact structure 16 also com prises a movable main contact 24 and a movable arcing contact 26, both mounted on a movable contact arm 28 pivotally supported on a bracket 30 mounted on a load terminal 32 secured to and extending through the base 14 for external connec tion. A flexible conductor 34 is connected between the contact arm 28 and the bracket 30 to ensure a good electrical connection therebetween.

The contact structure 16 is movable between the contact open position shown in Figure 1 and the con The drawing(s) originally filed were informal and the print here reproduced it taken from a later filed formal copy.

tact closed position shown in Figure 2 by an operating mechanism 36 mounted on the metal frame 12.

The operating mechanism 36 may be of a conventional design and may include toggle links 38 and an operating handle 40, an electromagneticthrow-in mechanism 42, a tripping mechanism 44 and an over current instantaneous tripping mechanism 46, all of which may be of any conventional design.

The contact structure 16 and the operating mechanism 36 are operatively interconnected by an interconnecting means composed of a contact lever 50 and an operating rod 52 made of suitable insulating material. One end of the contact lever 50 is pivotably connected at 51 to the contact arm 28 and the other end of the lever 50 is connected to one end of the operating rod 52 through an adpusting nut 54 for adjusting the overall length of the assembled contact lever 50 and the operating rod 52. The other end of the operating rod 52 through an adjusting nut 54 for the toggle links 38. Thus, the movement of the operating mechanism 36 is transmitted through the interconnecting means to the contact structure 16.

The operating rod 52 has a flange 56 for a purpose which will be described hereinafter.

The circuit interrupter Further comprises an electrically insulating housing 58 mounted on the base 14. The insulating housing 58, together with the base 14, encloses the contact structure 16, and the operating mechanism 36 is not enclosed in the housing 58.

Accordingly, the interior space within the housing is relatively small so that a quick pressure increase is obtained upon current interruption, and the contact structure 16 is isolated by the insulative housing wall from the operating mechanism 36 so that the dielectric strength therebetween is very high. These rela tivelysimple arrangements make the circuit inter rupter applicable to a high rated current.

The housing 58 has formed therein an opening 60 through which the operating rod 52 interconnecting the contact structure 16 and the operating mechanism 36 movably extends. In order to allowthe operating rod 52 to be substantially axially movable, the opening 60 is a little largerthan the outer dimensions of the operating rod 52, thus forming a clearance between the outer surface of the rod 52 and the edge of the opening 60. This clearance is effectively closed off by the insulative flange 56 integrally formed on the operating rod 52 against the passage of the high pressure gas generated upon the current interruption. In order to effectively close the opening against the passage of the gas even when the contacts are in the closed position (Figure 2) or in the almost-closed position, the insulating housing 58 has a thick portion 62 around the flange 56.

In order to more fully utilize the advantage of the insulating housing 58 enclosing the contact structure 16, the housing also includes an arc extinguisher 64.

In the embodiment illustrated, the arc extinguisher 64 is disposed within an arc extinguisher cover 68 detachably attached to the main body of the housing 58 by any suitable means such as screws 70. The cover 68 has therein a plurality of arc grids 72, an arc gas mixing chamber 74 and an arc gas cooling grid 76.

In the preferred embodiment of the present invention, the insulating housing 58 is in the form illustrated in Figure 3. That is, the base 14 has three sections, one for each pole unit, which sections are separated from each other by vertical walls 78,80, 82,84 integral with the base 14.

The insulating housing 58 includes four partition walls 86, 88, 90 and 92 adapted to be fixedly attached to the vertical walls 78 to 84 on the base 14 by any suitable means such as screws 94. Therefore, when the housing 58 is attached to the base 14, the interior spaces defined by the housing 53 and the base 14 are isolated from each other by vertical walls 78 to 84 and 86 to 92. The openings 60 for allowing the operating rods 52 to pass are seen in the top of the housing 58 in Figure 3.

The arc extinguisher covers 68 are detachably attached by the screws 70 or the like to the open sides of the insulating housing 58 with leg portions 69 inserted into the open sides.

Thus, when the circuit interrupter is assembled, the contact structure 16, with portions ofthetermi- nals 22 and 32, is substantially completely enclosed by an enclosure composed of the base 14, the insulating housing 58 and the arc extinguisher cover 68 interfitting with each other. The mechanical strength of the thus formed enclosure can be easily increased by increasing the thickness of the walls of the components or by employing a stronger material in order to accommodate the increased internal gas pressure due to the electric arc upon current inter ruption.

If it is desired, the insulating housing 58 may be formed in three pieces each having two vertical walls, with the necessary modifications applied to the base 14. Alternatively, the arc extingusher cover 68 may be formed in a single larger piece having integrally formed therein three arc extinguishing chambers forthree pole units.

In orderto evaluate the presentinvention,the invention as disclosed was applied to a conventional air circuit interrupter of a 2,000A rating frame with a rated short time withstand current of 50kA, 1 sec. at 500V AC, and it was found that a rated short circuit breaking capacity of 1 00kA was achieved without changing the rated short time withstand current of 50kA, 1 sec., unlike a current limiting type circuit interrupter which requires a decrease in rated short time withstand current.

Claims

1. A circuit interrupter comprising a contact structure including a pair of separable contacts and being connectable to an external circuit, an electri cally insulating enclosure substantially enclosing the contact structure to enable internal pressure within the enclosure to become effective in promoting an increase in the arc voltage, an operating mechanism disposed externally of the enclosure for effecting contact opening and closing movements of the con tact structure and being electrically isolated by the enclosure from the contact structure, and means movably extending through the enclosure for operatively interconnecting the contact structure and the operating mechanism so as to transmit the move ments of the operating mechanism to the contact structure.

2. A circuit interrupter as claimed in claim 1, wherein the enclosure has disposed therein an arc extinguisher.

3. A circuit interrupter as claimed in claim 1 or 2, wherein the enclosure comprises an insulating base member and an insulating housing attached to the base member.

4. A circuit interrupter as claimed in claim 2, wherein the arc extinguisher is disposed within an arc extinguisher cover detachably attached to the enclosure main body.

5. A circuit interrupter as claimed in any one of claims 1 to 4, wherein the interconnecting means comprises means for substantially covering an opening in the enclosure through which the interconnecting means extends against the passage of gas.

6. A circuit interrupter substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.