US2391759A - Electric circuit interrupter - Google Patents

Description

De c. 25, 1945.

T. w. wlLcox ELECTRIC CIRCUIT INTERRUPIER Filed Aug. 9, 1943 Inv'entov: Thomas W. Wilcox b W ZJwJ v f His Attorneg.-

a Q P Patented Dec. 25, 1945 ELECTRIC CIRCUIT INTER'RUPTER Thomas W. Wilcox, Harrow, England, assignor to General Electric Company, a corporation of New York Application August 9, 1943, Serial No. 497,914 In Great Britain August 11, 1942 4 Claims.

My invention rel-ates to electric circuit interrupters and more particularly to a new improved contact arrangement for electric circuit breakers employed for the interruption of heavy currents.

It is well known that the arc energ in a circuit breaker for example increases with increase in the length of the arc. Such increase in are energy requires the dissipation of a considerable amount of heat during the are interrupting operation. It is desirable in circuit breakers for interrupting heavy fault currents to keep the are drawn as short as possible in order to maintain the arc energy at a minimum value. It is also desirable to move the roots of the are on the associated contact so as to reduce the vaporization and consequent erosion of such contact. Many arrangements have been suggested for causing movement of the arc roots, most of which, nowever, have been fairl complicated and expensive.

It is an object of my invention to provide new and improved means for causing movement of the arc roots on an associated contact so as to reduce the vaporization and consequent erosion of the contact.

It is another object of my invention to provide a new and improved arrangement in an electric circuit interrupter for maintaining the arc energy ata minimum value.

Further objects and advantages of my invention wil1 become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing in which Fig. 1 is a sectional view of a portion of an electric circuit interrupter embodying my invention, and Fig, 2 is a view taken .on line 2--.2 of Fig. 1.

Although my invention is of general application and may be used in circuit interrupters of various types, it is of particular use in alternat mg current fluid blast electric circuit breakers wherein arc extinction is brought about by the action of a blast of fluid such as compressed air or' gas. The invention is furthermore particularly adapted for use in fluid blast circuit breakers in which the direction of the blast is parallel with but opposite to the direction of movement of the switching member.

Referring now to the drawing, I have illustrated a cylindrical insulating arc extinguishing chamber l0 formed of insulating material and provided with a portion of restricted cross-sectional area H which will hereinafter be referred to as a nozzle, or restriction H. Mounted within arc extinguishing chamber ID are a pair of relatively movable contacts comprising a fixed contact generally indicated at l2, and a movable rod contact l3. Fixed contact I2 is suitably supported above nozzle H and is in the form of an annulus or socket member which forms a nozzle contact through which the blast of fluid, such as air, is directed. Preferably fixed contact 12 is provided with spring biased contact members M for electrically engaging rod contact I 3 which latter may be in the form of a tube as shown in Fig. 1, if desired.

Any suitable means for causing relative separation between contacts I2 and I3 may be provided. I have chosen to illustrate this means as comprising a piston l5 reciprocatingly mounted in a suitable cylinder within arc extinguishing chamber l0. Piston I5 is operatingly connected to rod contact I3. A suitable spring I6 is provided which biases rod contact l3 into conducting engagement with fixed contact [2. The upward movement of rod contact I3 is limited by means of a stop I! supported within chamber l0. Arc extinguishing chamber [0 is connected at a point above piston l5 and below nozzle II with a source of fluid under pressure (not shown) by means of conduit 18. In Fig. 1 the circuit interrupter is disclosed at an intermediate point during the opening operation when fluid under pressure is being supplied through conduit i 8 causing piston 15 to move downwardly and furthermore causing a blast of fluid to flow through nozzle I l and nozzle contact [2 to extinguish the arc drawn between relatively movable contacts l2 and I3. As soon as the fluid under pressure supplied to conduit I8 is shut off spring IE will force rod contact [3 toward nozzle contact l2 to reclose the circuit. Contacts l2 and 13 are respectively connected to line terminals [9 and 20, schematically shown.

As has been pointed out above, it is essential insofar as eflicient operation of the circuit breaker is concerned, that the arc be short and be prevented from looping or bowing in order to keep the are energy at a minimum. When the fixed nozzle contact 12 is small in diameter it frequently happens that in itself it suffices to prevent such bowing or looping, but when circuit breakers are constructed for heavy currents such as the circuit breaker in Fig, 1, the diameter of nozzle contact l2 may become so large that the arc can form a considerable loop beyond nozzle contact l2. My invention is particularly concerned bers definitely prevents bowing orlooping and' also minimizes erosion of the contact because the.

are roots cannot remain at any one fixed point on the contact.

Accordingly, in the drawing I have provided a plurality of arcing members 2! associated with fixed contact [2 as will become apparent from the 'following description which are arranged with their longitudinal aXes in a plane at right angles to the path of movement of movable contact is and disposed tangentially to a circle concentric with the axis of'this path 'of movement. I have illustrated arcing contacts 2| as being welded or otherwise suitably fastened to an annular conducting member 22 which is suitably mounted above contact l2. and electrically connected thereto. In this way, the arcing members 2! are arranged to be connected to one another at their outer ends and also to the source of current supply through terminal IS. The arcing members, furthermore, all extend in the same direction from the circle to which they are tangential, which may be clockwise or counterclockwise. In Fig. 2, I have illustrated the arcing members as extending from the circle to which they are tangential in a counterclockwise direction.

When fluid under pressure is supplied to arcing chamber I!) through conduit I3 an arc is drawn between relatively separable contacts 12 and I3 and a blast of fluid through nozzle ii and nozzle contact I2 tends rapidly to cool the arc and cause extinguishment thereof. The fluid blast will cause the arc to extend upwardly so that the arc roots strike on one of the arcing members 25. will be observed, therefore, that when this happens a current loop is present and the electromagnetic force by virtue of the current flowing in this loop will tend to bow the loop so that the arc will move toward the inner tip 2| of the arcing member 2|, from which it will move to the next adjacent arcing member whereupon the process will be repeated so that the arc will be transferred from arcing member to arcing member in a substantially circular path in a clockwise direction, as viewed in Fig. 2. Although in the drawing I have illustrated four arcing members arranged substantially at right angles with each other, it will be obvious that more or less arcing members may be provided.

In view of the detailed description included above, the operation of the circuit interrupting device embodying my invention will be obvious. With this arrangement a very simple means for causing movement of the arc roots to prevent erosion of the contacts is obtained and furthermore the arc is prevented from bowing or becoming unduly long by arcing members 2! thereby maintaining the arcing energy at a minimum.

While I have described a particular embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent in the United States is:

1. In an electric circuit breaker, a pair of relatively movable contacts comprising a fixed contact and a movable contact, means for producing relative separation of said contacts to draw'an arc therebetween, a conducting member electrically connected to said fixed contact and normally carrying no current, a plurality of arcing members arranged with their longitudinal axes in a plane at right angles to the path of said movable contact and being mechanically supported and electrically connected to said conducting member, said arcing members being disposed tangentially to a circle concentric with the axis of said path of said movable movable contact, and means fortransferring said are from said fixed contact to one of said arcing members, the arrangement of said arcing members with respect to each other and the contacts being such that the path of the current flowing between said movable contact and said conducting member including said are is in the form of a loop so that the electromagnetic force produced causes the arc roots to move from arcing member to arcing member thereby minimizing erosion of said members.

2. In an electric circuit breaker, a pair of relatively movable contacts comprising a fixed contact and a movable contact, means for producing relative separation of said contacts to draw an arc therebetween, an annular conducting member electrically connected to said fixed contact and normally carrying no current, a plurality of arcing members arranged with their longitudinal axes in a plane at right angles to the path of said movable contact and being mechanically supported and electrically connected to said annular member, said arcing members being disposed tangentially to a circle concentric with the axis of said path of said movable contact, and means for transferring said are from said fixed contact to one of said arcing members, the arrangement of said arcing members with respect to each other and the contacts being such that the path of the current flowing between said movable contact and said annular member including said are is in the form of a loop so that the electromagnetic force produced causes the arc roots to move in a generally circular path from arcing member to arcing member thereby minimizing erosion of said mem bers.

3. In an electric circuit interrupter for controlling an associated electric circuit comprising'a pair of contacts at least one of which is movable so that said contacts are separable to draw an arc therebetween, means for connecting said contacts with said associated circuit, one of said contacts having associated therewith, in conducting relation, a plurality of fixed arcing members arranged with their longitudinal axis at an angle approximating a plane normal to the path of the moving contact, each arcing member being disposed tangentially to a circle surroundingthe axis of said path with all of said arcing members extending in the same. direction from the circle to Which they are tangential, o that an are drawn between said contacts will engage said arcing members sequentially being moved from one to another by the electromagnetic force of the current in the are, thereby to minimize erosion of the members and accordingly. to minimize the amount of metallic vapor in the arc and therefore facilitate the inter!- ruption of the arc.

4. In an electric circuit interrupter comprising a pair of contacts at least one of which is movable so that said contacts are separable to draw an arc therebetween, an arcing member normally carrying no current arranged with its longitudinal axis in a plane at right angles to the path of said movable contact and disposed tangentially to a circle concentric with the axis of said path, and means for causing the arc drawn between said contacts to appear between said movable contact and said arcing member whereby the path of the current flowing through said arc is in the form of a loop so that the electromagnetic force produced causes the arc to move along said arcing member to minimize erosion of said member.

THOMAS W. WILCOX.

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