US2413555A - Electric circuit interrupter - Google Patents

Description

TIME IN SECONDS Dec. 31, 1946. c. H. FLURSCHEIM ELECTRIC CIRCUIT INTERRUPTER Filed Oct. 15, 1945 Inventor:

PRESSURE m TERRUPTING UNIT IN LB5.PE .SQUAEE INCH. H S OTneH Cedric HFIurscheim.

Patented Dec. 31, 1946 ELECTRIC CIRCUIT INTERRUPTER Cedric H. Flur'sche'im, Bowdon, England, assignor to Metropolitan-Vickers Electrical Company Limited, London, England, a British company Application October 15, 1945, Serial No. 622,470 In Great Britain January 6, 1945 8 Claims. 1

My invention relates to electric circuit interrupters and more particularly to circuit interr'up'ters of the type in which relative movement between the contacts is obtained in response to a supply of fluid under pressure. My invention is especially applicable to fluid blast circuit breakers such as the so-calle'd gas blast circuit breaker.

It has been common practice in connection with electriccircu'it interrupting devices to provide two sets of contacts, one set being generally referred to as arcing contacts while the other set is generally referred to as current carrying contacts. Various arrangements have been provided for causing the current carrying contacts to separate first so that all the current is transferred to the arcingcontac'ts whereupon the arc is finally drawn at the arcing contacts and is interrupted there. burning at all but the arcing contacts which may be constructed of a material which is especially are resistant.

In fluid operatedcircuit interrupting devices, and particularly since the advent and extensive use of the gas blast circuit breaker, it has become common practice to cause relative separation of the contacts through operation of a suitable fiu'id motor associated therewith. One type of gas blast circuit breaker which has been extensively used employed fluid operated contacts which are biased to the closed position by means of suitable biasing means or the like. An example of such a circuit breaker is disclosed and claimed in Uebermuth Patent 1,904,577, granted April 18, 1933.

. t would be desirable in electric circuit breakers employing fluid operated contacts to provide both arcing and current carrying contacts with simple means involving no interconnections between these different types of contacts to cause sequential operation of said contacts.

It is an object of my invention to provide a new and improved circuit interrupting device having two or more sets of relatively separable contacts provided with means whereby said sets of contacts are caused to open in a desired sequence.

It is another object of my invention to provide an electric circuit interrupter employing two independent sets of parallel arranged contacts adapted to be operated to the open position by applying fiuid to suitable associated fiuid operated means and wherein sequential operation of said sets of contacts is obtained without any Such an arrangement eliminates contact mechanical interconnections between said different sets of contacts.

Still another object of my invention is to provide an electric circuit breaker employing piston operated contacts arranged in parallel with each other with spring biasing means biasing said contacts to the closed position, in which the ratio of the piston area to the spring loading of one of said contacts difiers from the ratio of piston area to the spring loading of the other of said contacts.

Further objects and advantages of my invention willbecome 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 somewhat schematic diagrain partly in section of an electric circuit interrupting device embodying my invention, and Fig. 2 is a curve diagram to aid in understanding my invention.

Although my invention is applicable to electric circuit breakers whether they be single phase or polyphase, for the sake of simplicity in the drawing as well as in the description, my invention has been illustrated in connection with only a single phase circuit interrupter.

As illustrated in the drawing, the electric circuit interrupter comprises an interrupting unit generally indicated at l which is connected in series with an isolating or disconnecting switch 2 between circuit terminals 3 and 4 of an associated circuit to be controlled. The interrupting unit I comprises an arcing or contact chamber 5 which is illustrated as being formed of conducting material having in one side wall thereof an opening through which extends an insulating bushing 6 Supporting a tubular conducting member I, one end of which extends into interrupting or contact chamber 5. The end of conducting member 7 extending into chamber 5 is provided with a circumferential flange 8 so as to provide a fixed contact surface. A central opening 9 is provided in conducting member I at the flanged end thereof defining a blast nozzle or orifice through which the air or other gas of the fluid blast to be described hereinafter is adapted to be discharged from the contact or pressure confining chamber 5 through tubular conductor 1. Tubular conducting member 5, one end of which provides an annular fixed contact, is in many respects quite similar to the fixed contact disclosed in copend- 3 ing application Serial No. 597,022, Cox and Wilcox, filed June 1, 1945, and assigned to the same assignee as the present application.

Cooperating with the fixed contact which will hereinafter be designated by the numeral 8, which specifically refers to the circumferential flange, are a plurality of movable .contacts it and II. For the sake of simplifying the drawing, only two movable contacts I9 and II have been illustrated, although it should be understood that any number of such parallel arranged movable contacts may be provided. In the above mentioned Cox et al. application, three such parallel arranged movable contacts are illustrated. Movable contacts 10 and II may be conventional pin-type retractable contacts such as are disclosed in the above mentioned Uebermuth patent or as illustrated may comprise pivotally arranged contacts I and H pivotally mounted to contact chamber as indicated at [2 and I3 respectively. The contact It] is illustrated as a current carrying contact while the contact H is illustrated as an arcing contact and is preferably provided with a tip I l of are resistant material, such as tungsten or the like. It will be understood that where more than two movable contacts suchas Hi and H are employed, only a single arcing contact H is generally required while the remaining paral lel arranged movable contacts would be current carrying contacts, the number depending upon the magnitude of the current to be carried.

In order to provide relative separation between the movable contact Ill and fixed contact 8, I pro- Vide a fluid motor comprising a piston l5 movable in a cylinder l6 which may or may not be integral with pressure confining chamber 5. Piston i5 is connected by a link I! With movable contact [0.

In order to provide relative separation between the movable contact II and fixed contact 8, I provide a fluid motor comprising a piston 18 movable in a cylinder l9 which may or may not be integral with pressure confining chamber 5. Piston IB is connected by a link 20 with movable contact I l.

Both of the contacts l0 and II are biased to the closed position by suitable compression spring means indicated at 2! and 22 respectively. The spring means 22, as will be brought out in greater detail hereinafter, is illustrated as comprising a pair of nested springs 22a and 22b.

In order to cause operation of the fluid motors comprising pistons l5 and I8 and also to supply a blast of arc-extinguishing fluid adjacent the relatively movable contacts for arc-extinguishing purposes, pressure confining or contact chamber 5 is preferably connected by means of a conduit 23 and blast valve 24 to a source of fluid under pressure 25 which is preferably, as illustrated, a tank containing air or other gas under pressure.

In order to cause the current carrying contacts of interrupting unit I to open before the arcing contacts separate so that the only are drawn is at the arcing contacts sequential operation of the arcing and current carrying contacts is desired. In accordance with my invention this is accomplished without any mechanical interconnection whatever between the arcing and current carrying contacts or between the operating means therefor. In accordance with my invention the ratio of the piston area l5 to the spring loading applied thereto is different from the ratio of the area of piston I8 to its spring loading. Specifically, the ratio of the area of piston [5 to the force exerted thereon by spring 2i is greater than the ratio of the area of piston 18 to the force exerted thereon by springs 22a and 2212. With this arrangement it is obvious that fluid under pressure supplied to pressure confining chamber 5 from source 25, as it builds up from zero pressure to full pressure, will cause movement of piston l5 and consequently movement in the opening direction of current-carrying contact In prior to movement of piston l8 and opening of arcing contact II. As a consequence thereof, during a circuit interrupting operation current-carrying contact I0 is first opened to transfer all the current to arcing contact H whereupon arcing contact H is subsequently opened and the are drawn is rapidly extinguished by a blast of fluid under pressure across fixed contact 8 and through opening 9. A an example, the ratios of piston area to spring loading might be made such that in an electric circuit breaker operating at a normal air or gas pressure of 200 pounds per square inch, current-carrying contact It will begin to open when the pressure in chamber 5 reaches 25 pounds per square inch, whereas arcing contact II will not begin to move to the open position until the fluid or air pressure has risen to 75 pounds per square inch.

In Fig. 2 there is plotted a curve illustrating the pressure build-up in pressure confining chamber 5 as a function of time with zero time being indicated at the instant blast valve 24 is opened. When the pressure builds up to the point indicated at T1 in Fig. 2 current-carrying contacts such as ID are opened and not until the pressure builds up to the point indicated at T2 in Fig. 2 is arcing contact I! moved to the open position. t

In the arrangement disclosed in Fig. l the ratios of piston area to spring loading is accomplished by having the same piston area in each case and. varying the spring loads. It will be understood however that the same result could be accomplished by varying the piston areas and having the same spring loading in each case.

It will be obvious that with my invention the only contact which will require any attention is contact II where an arc is drawn. It will be obvious that arcing contact ll 'could be so positioned in the interrupting head I as to have the most accessible location and furthermore it could also be positioned inthe most favorable interrupting relation with respect to opening 9 which defines the blast nozzle, since the current-carrying contacts, such as I0, perform no interrupting operation.

In view of the detailed description included above, the operation of the. circuit interrupting device embodying my invention will be obvious to those skilled in the art. When blast valve 24 is opened sequential operation of current-carrying contact IE! and arcing contact H is obtained without any mechanical relationships or connections between these contacts. It Will be understood that suitable means for operating disconnecting contact 2 will be provided following interruption of the circuit in chamber 5 so that the circuit will remain open when the blast valve 24 is closed and contacts l0 and Il reclose in response to their biasing means.

It Will be understood that my invention is quite applicable to any circuit breakers in which the arrangement of the pressure displaceable contacts and the cooperating fixed contact or contacts are of any desired form other than that mentioned or described above.

While I have shown and described a particula 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 in its broader aspects 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 of the United States is:

l. Ina fluid operated electric circuit breaker comprising a plurality of relatively separable contacts including a set of arcing contacts and a set of current-carrying contacts, means for biasing said arcing contacts to the closed position, means for biasing said current-carrying contacts to the closed position, fluid operated means for opening said arcing contacts, fluid operated means for opening said current carrying contacts, and means for supplying fluid under pressure to said fluid operated means for causing opening of said current carrying contacts and said arcing contacts, said means for biasing said current-carrying contacts to the closed position and said fluid operated means for said current-carrying contacts being so proportioned relative to the means for biasing said arcing contacts to the closed position and said fluid operated means for said arcing contacts that said current-carrying contacts open in response to operation of said means for supplying fluid under pressure to said fluid operated means prior to opening of said arcing contacts.

2. In a fluid operated electric circuit breaker comprising a plurality of relatively separable contacts including a set of arcing contacts and a set of current-carrying contacts, means for biasing said arcing contacts to the closed position, means for biasing said current-carrying contacts to the closed position, fluid operated means including a first piston for opening said arcing contacts, fluid operated means including a second piston for opening said current-carrying contacts, and means for supplying fluid under pressure to said fluid operated means for causing opening of said current-carrying contacts and said arcing contacts, said means for biasing said arcing contacts to the closed position and said first piston being so proportioned relative to the means for biasing said current-carrying contacts to the closed position and said second piston that said current-carrying contacts open in response to operation of said means for supplying fluid under pressure to said fluid operated means prior to opening of said arcing contacts.

3. In a fluid operated electric circuit breaker comprising a plurality of relatively separable contacts including a set of arcing contacts and a set of current-carryin contacts arranged in parallel relationship, a flrst spring means for biasing said arcing contacts to the closed position, a second spring means for biasing said current-carrying contacts to the closed position, fluid operated means including a first piston for opening said arcing contacts, fluid operated means including a second piston for opening said current-carrying contacts, and means for supplying fluid under pressure to said fluid operated means for causing opening of said current-carrying contacts and said arcing contacts, said first spring means and said first piston being so proportioned relative to said second spring means and said second piston that said current-carrying contacts open in response to operation of said means for supplying fluid under pressure to said fluid operated means prior to opening or said arcing contacts.

4. In a fluid operated electric circuit breaker comprising a plurality of relatively separable contacts including a set of arcing contacts and a set of current-carrying contacts arranged in parallel relationship, a first spring means for biasing said arcing contacts to the closed position, a second spring means for biasing said current-carrying contacts to the closed position, fluid operated means including a first piston for opening said arcing contacts, fluid operated means including a second piston for opening said current-carrying contacts, and means for supplying fluid under pressure to said fluid operated means for causing opening of said current carrying contacts and said arcing contacts, the ratio of the area of said second piston to the force exerted by said second spring means being different from the ratio of the area of said first piston to the force exerted by said first spring means.

5. In a fluid operated electric circuit breaker comprising a plurality of relatively separable contacts including a set of arcing contacts and a set of current-carrying contacts arranged in parallel relationship, a first spring means for biasing said arcing contacts to the closed position, a second spring means for biasing said currentcarrying contacts to the closed position, fluid operated means including a first piston for opening said arcing contacts, fluid operated means including a second piston for opening said ourrent-carrying contacts, and means for supplying fluid under pressure to said fluid operated means for causing opening of said current-carrying contacts and said arcing contacts, the ratio of the area of said second piston to the force exerted by said second spring means being greater than the ratio of the area of said first piston to the force exerted by said first spring means.

6. In a fluid operated circuit breaker comprising arcing contacts and current-carrying contacts with means for biasing said contacts to the closed position, separate fluid operated means for said arcing contacts and said current-carrying contacts, and means for causing said arcing contacts and said current carrying contacts to operate in a predetermined sequence during the circuit interrupting operation comprising a predetermined relationship between the biasing means and fluid operated means for both said arcing and said current carrying contacts.

7. In a fluid operated circuit breaker comprising arcing contacts and current carying contacts with means for biasing said contacts to the closed position, separate fluid operated means for said arcing contacts and said current carrying contacts, and means for causing said arcing contacts and said current carrying contacts to operate in a predetermined sequence during the circuit interrupting operation comprising identical fluid operated means for aid arcing and current carrying contacts but different biasing means.

8. In a fluid operated circuit breaker comprising arcing contacts and current carrying contacts with means for biasing said contacts to the closed position, separate fluid operated means for said arcing contact and said current carrying contacts, and means for causing said arcing contacts to open after said current carrying contacts have opened during the circuit interrupting operation comprising identical fluid operated means for said 1 arcing and current carrying contacts but different biasing means.

CEDRIC H. FLURSCHEIM.

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