US1940120A - Electric switch and arc extinguishing apparatus - Google Patents

Description

Dec. l9,` 1933. w. s. EDSALLl 1,940,120

ELECTRIC SwlTCH AND ARC EXTNGUISHING APPARATUS Filed May 22, 1930 Patented Dee. 11a-'1933v william s. Brookline, Mass., miinor to Condit Electrical Manufacturing Corporation,

South Boston, Mass., a

chusetts of Massacorporation Application4 May22, 1930. Serial No.V 454,647

claims. (c1. zoon-150)."l

This invention relates to electric switches and y particularly to oil immersed switches and alternating current switches. l One of the objects oi the present invention 'is to provide an oilimmersed electric switch with means which is supported independently ofy the stationary and movable'. switch members for breaking up the. circuit interrupting 4arc into aplurality oil small arcsand for cooling the smallarcs so that they are rapidlyextinguished and so that circuit interruption takes place with a' mini'- mum of disturbance either to the oil or to the circuit controlled by the switch.

Another-object of theinvention is the provision of an electric switch having means traversed by x to be raised to engage the toe portions of the tact members together and also for setting up aA the switch current for forcing the separable -c0n magnetic tield that blows the circuit interrupting arc into a plurality of conducting plates where the arc is broken upinto a plurality of short arcs that are rapidly deionized and extinguished.

A further objectv of. the invention is the provision oi' a plurality of closely spaced metal plates which are supported close to but independently of the stationary andmovable switch members and preferably b y the insulating lining of the oil receptacle in which the switch members', are immersed Aand which plates act to receivethe circuit interrupting arc and divide itinto a plurality of A short arcs which are rapidly deionized and extinguished.

A yet further object of the invention is generally to improve the construction and operation of electric switches.

Fig. 1 is av sectional elevation of an elect'ric switch embodying the present invention.

Fig.. 2 is an enlarged sectional detail of the cooperating parts of the stationary and movable contact members. Fig. 3 is a plan view of the apparatus of Fig. 2.

4* Fig. 4 is a perspective detail of one of the plate ent invention includes the oil containin As here shown, the switch embodying lthe prescasing comprising the oil containing receptacleo and the switch frame 12 which constitutes a cover for the open top of the oil receptacle.

` ary switch members 14 having conductingv studs .The switch includes a pair of insulated station- 16." Said switch members are carried by theframe 12 and depend into the oil of the receptacle. Each stationary switch member is provided with a main current-carrying .contact member that comprises an' inverted brush member 18 that is secured to the lower end of the stud 16. An auxiliary contact or arcing member` the arms 22 of a supporting frame Ythat is clampedl t between the shank of the 'brush member and a nut 24 on the .stud 16. The movable switchmember includes a' lifting rod 26 that is vertically movable to openand close the'switch and is operated by suitable mechanism not herein necessary to illustrate. The lifting rod'at its lower -end carries a bridging member 28 which comprises aninverted channel having depending anges 30 and a horizontal connecting web 32.. Said web islocated loosely upon a spacing bushing 34 carried by a stud 36 that is secured to and depends below the lifting rod 26. Said bridging member is adapted brush membersy 18 and thereby toclose the current vcarryingtpath of the circuit through the switch. A ysupporting member 38 is located on` said stud 36 beneath the bridging member 28 and between the ilanges 30 thereof. '.Saidsupporting y member comprises an'inverted channel of nonmagnetic material having depending ilanges 40 and ahorizontal connecting wev 42. Said web is, apertured to receive the stud 3 and is clamped to the lifting rod between the collar 34 and the nut 44. A conducting bar 46 is located within the anges of the supporting member and is clamped against the lower i'ace of the web 42 and is provided at each end Withanouter depending section 48, a lower horizontal and inwardly directed section 50 which is parallel with the body portion 46 and an upwardly directed inner end section 52, all of which cooperate to form a conducting loop. .A movable auxiliary contact or arcing 'member 54 cooperates with and is similar in construction to the stationary .arcing .member 20 and is locatedbetween th'e upstanding ears 56 of a horizontal arm 58 which is extended loosely and generally horizontally inwardly into pivotally connected with the end ci the upturned inner. section 52. The inner endl o! said arm is connected electrically through a flexible conductor'62 with the inner end portion of the horizontal section 50. f An insulatingbushing 64 surrounds saidv arm inthe slot '60 and thereby prevents the arm from contacting electrically .with any outer portion ofthe loop. Al spring 66 is receivedin a cup 68 carried by the bottom section 50 .and bear.;J against said insulating bushing Y whereby tourge said arm and the arcing member carried thereby towards the stationary arcing member 20.

asl

bers are maintained in engagement by the magnetic reactions'of't/he currents traversing the arm effect is most needed.

yplates '70, however, serves to enhance. the magand the looped portions of the conductor 46. Pole plates '1U of magnetic material are secured to the depending flanges 40 of the supporting member 38 and lie on opposite Isides of the loop portion of the conductor and extend outwardly therefrom and are terminated on opposite sides of the arcing members, whereby to concentrate the magnetic flux of-the loop portion of the conductors and` of the arms 58 in the arc zone between the contact members whereby to react with the circuit interrupting arc in a -direction to force the arc outwardly toward the opposite side walls of the oil receptacle.

The magnetic field set up by the looped portion of the conductor even without the pole plates .-is suflicient in itself to exert a strong blowout effect upon the circuit interrupting arc, especially at the high values of current where the blowout The presence of the pole netic blowout effect of the conducting loop for relatively low values of current so that the switch has a strong blowout effect at all values of current where the length of the interrupting arc will be important.

Protective plates 72 of insulating and arc resisting material are preferably located on the inner faces of the pole plates so as to prevent the pole plates from being contacted with or damaged by the circuit interrupting arc.

The construction thus described is essentially the same as is disclosed Aand claimed lin the copending application of Chester D. Ainsworth, Serial No. 453,179 led May 17, 1930,V and assigned tothe assignee of the present application.

In accordance with the present invention,

' means arelprovided to receive the magnetically distorted circuit interrupting arc and to divide the long arc into a series of separate short arcs land to cool or deionize rapidly the short arcs so that they are rapidly extinguished with small disrturbance to theoil orto the circuit controlled by the switch. To' this end a plurality of horizontal metal plates 74 having goodheat absorbing or conducting and dissipating ability, as copper plates, are disposed in `verticallyspaced rows or stacks close tothe arc zones between the separable arcing` members and between said arcing members and the opposite side walls of the oil-- receptacle.

The stacks of plates preferably are sufficiently long to -extend adjacent the entire length of the arc zone between the contact membersso that the plates are effective to receive the arc even though the arc should persist for the entire length of opening movement for the switch members. Ordinarily, however, itis not necessary to extend the stacks downwardly this extreme distance. Each stack of plates is contained .within an insulating holder 76 which has a vertical rear wall 77 and forwardly extended walls 78'that terminate in confronting walls 80 provided with rows of` teeth 82 and slots 84 located between the teeth. The plates 74 are l0- wall 76 to provide a vertical channel 88 between the plates and the wall that is ,open at the top and also at the bottom in which any gas or liquid that is forced out of the stack can escape from the holder. The inner edges of the plates preferably abut against shoulders 90 of said holder whereby to define the position of the plates in the holder. Preferably the plates are only rel tained frictionally in the holder so that if burned or damaged they can be readily removed and replaced by other plates.

The holders '76 arey secured to the opposite walls of the insulating tank lining 92 and are secured to said lining by horizontally spaced vertically extended Z-bars 94 which are secured by screws 96 to the lining and provide chan- `nels in which the oppositely extended ange's 98 of the holders are located. The holders preferably are loosely received in said supporting channels so that they can be withdrawn with the plates as a unit upon need. 1

The outer edges of the plates are located close to the separable arcing members and the movable arcing members, when the switch opens, are caused to travel downwardly in front of said stacks of plates. The magnetic fieldy in the arc zone causes the arcs to be blown outwardly toward the stack and in between the plates thus to divide the arcs into a series of short arcs which by the blowout field are forced over the surfaces of said plates and toward the tank walls.

jIhe spaces between the plates are relatively narrow so that the oil that is between the plates tends to remain therein .so that the arcs are caused to be held magnetically into intimate contact with the bodies of oil. 'Ihe bodies of oil are maintained cold by the cooled platesand thereby rapidly extinguish the short arcs. The movement of the arcs over the plates also cools and deionizes the arcs so that the result is that the arcs are rapidly extinguished and the circuit interrupted with small disturbance to the oil and to the switch circuit.

Any oil gases that are generated are caused to be cooled by the plates so that danger of ignition of any combustible mixture in the gas expansion space of the switch casing above the oil level is' minimized.

/The arc voltage that can be absorbed by any pair of spaced plates depends largely upon the spacing therebetween. When the spacing of the the plates can not be exerted throughout the entire arc zone between them, the arc potential that can be absorbed across any pair of plates isv in the vicinity of three hundred volts, which represents the break down, value` of the instantaneously recovered dielectric strength of the normal gas insulating medium between the plates.v

When, however, the plates are close together, for instance, a millimeter merel or less, so that the vdeionizing effect of the plates can extend plates. In this latter case each pair of plates can absorb a'thousand volts or more, the arc going out at the current zero and not being re-established unless the recovered potential is high 413() plates'is so great that the deionizing effect of l tionary and movable switch members having cooperating arcing members immersed in the oil in said casing, and an arc extinguishing device comprising an insulating holder carried by said lining having opposed toothed walls and a stack of superposed arc-receivirg and .extinguishing metal plates located in the interdental spaces of and carried by said walls having their similar ends terminated close to said arcing members and the line of movement ot said movable switch member.

2. An electric vswitch comprising an oil containing casing, an insulating lining therein, stationary 'and movable switch members having cooperating arcing members immersed in the oil in said casing, and an arc extinguishing device comprising an insulating holder carried by said lining having opposed toothed walls and a stack oi superposed arc-receiving and extinguishing metal plates located in the interdental spaces of 'and carried by said walls having their similar ends terminated close to said arcing members and the line oi' movement oi said movable switch member, and electromagnetic means carried by said movable switch member which forces the circuit interrupting arc into said stack of plates where the arc is divided into a series of short arcs that are rapidly extinguished.

3. An electric switch having separable oil immersed arcing members, and an arc extinguishing device having means which supports it independently oi said arcing members, said device including a holder having an oil containing channel which is open at the top and bottom and a plurality of superposed metal plates which are located in said channel, said plates being extended outwardly beyond said holder and having their similar outer ends terminated close to the line of separation of said arcing members and having their inner ends spacedv from the end of said channel,` thel spaces between said plates being open to said channel, and means which yforces the circuit interrupting arc into the engagement of said plates.

4. An electric oil switch having stationary and movable arcing members, an arc' extinguishing .device comprising a stack of spaced electricallyconducting plates located close to and extended in the direction oi movement of said movable arcing member, a casing removably enclosing said arcing members and plate-stack and containing oil that quenches the arc and occupies the spaces between the plates, and an insulating lining disposed removably between said casing wall and said arcing members and constituting the support for said stack, the stack being removable with the lining. y

5. An oil immersed electric switch comprising an oil containing casing, stationary contact members depending therein, a bridging member for connecting said contact members movable vertically thereunder, and arc extinguishing de'- vces comprising stacks of vertically spaced horizontal metal. plates disposed 'each beside the bridging member and a separate one o! said stationary contact members and between said contact member and said casing and immersed in the oil and having oil between lthe plates, said stacks being located close to and extended inthe direction o! movement of said bridging member, and an insulating Alining located removably within said casing and outside of said stacks, said stacks being carried by and being removable with said lining, and said lining constituting means which supports said stacks in the aforesaid position.

WILLIAM S. EDBALL.`

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