US2863969A

US2863969A - Barriers for isolation of circuit breaker phases

Info

Publication number: US2863969A
Application number: US622952A
Authority: US
Inventors: Edmunds William Harold
Original assignee: ITE Circuit Breaker Co
Current assignee: ITE Circuit Breaker Co
Priority date: 1956-11-19
Filing date: 1956-11-19
Publication date: 1958-12-09
Anticipated expiration: 1975-12-09
Also published as: GB877809A

Description

Dec. 9, 1958 w. H. EDMUNDS BARRIERS FOR ISOLATION OF CIRCUIT BREAKER PHASES Filed Nov. 19, 1956 2 Sheets-Sheet l w. A; EDMUNDS 7 Dec. 9, 1958 BARRIERS F OR ISOLATION OF CIRCUIT BREAKER PHASES Filed Nov. 19, 1956 2 Sheets-Sheet 2 dLL J ///4 Z z 2 V TOR. 4 w/Luim ywgaiwmmw United States Patent i BARRIERS FOR ISOLATION OF CIRiIUlT BREAKER PHASES William Harold Edmunds, Havertown, Pa., assignor to I-T-E (Iircnit Breaker Company, Philadelphia, Pa, a corporation of Pennsylvania Application November 19, 1956, Serial No. 622,952

12 Claims. (Cl. 200144) My invention relates to a barrier member which is positioned in one or more channels of a molded case circuit breaker to prevent the circulation of ionized gas from the contacts of one phase to the contacts of another phase through openings in the channel walls.

Multi-phase molded case circuit breakers usually comprise a fixed contact and a movable contact which is attached to a contact arm for each of the circuit breaker phases. Each of the contact mechanisms are then operated from a common operating shaft which is in turn operated by a single operating handle and operating mechanism. This mechanism could, of course, include tripping devices for automatically operating the circuit breaker responsive to fault conditions as well as all of the devices commonly in use in the field of molded case circuit breakers. Each of the contact mechanisms are positioned in a respective channel of the circuit breaker base. These channels are substantially enclosed when a circuit breaker cover is connected to the top of the circuit breaker base.

Since, however, the movable contact arms of each pair of cooperating contacts is operated from a common operating shaft, the operating shaft must penetrate the channel walls which normally isolate the phases from one another. In so penetrating these channel walls, it is, of course, necessary that openings be placed in the walls.

In view of this condition it is now possible for ionized gas, due to contact disengagement, to circulate through the openings in the channel walls and so interconnect conducting members of different phases through an ionized gas path which could subsequently lead to a phase to phase flashover.

This condition is particularly severe when the circuit breaker is coordinated with current limiting devices as is set forth in my co-pending applications Serial No. 461,378, filed October 11, 1 954, to William H. Edmunds entitled Circuit Breaker Having Electrical and Mechanical .Co-ordination with a Current Limiting Device, and

Serial No. 622,042, filed November 14, 19 56, to William H. Edmunds entitled End Mounting of a Current Limiting Device Associated With a Circuit Breaker, and assigned to the assignee of the instant application, which are herein made a part of this specification.

When each of the circuit breaker phases are connected in series with a respective current limiting fuse or current limiting device as set forth in the above noted co-pending applications, the let-through current of a current limiting fuse, prior to operation of the current limiting fuse, may be so high that blow-off forces causes separation of the cooperating contacts. This condition leads to the production of ionized gas, as is well known in the art. This ionized gas may then fiow through the openings in the channel wall which are necessary in view of a common operating shaft and other equipment which is common to each of the circuit breaker phases and requires mechanical communication through the channel walls, whereby a phase to phase fault condition could be established. Y

This condition has been a particularly severe one and has severely limited the use of the above noted combination of a circuit breaker and a current limiting fuse wherein these components are both electrically and mechanically coordinated as is set forth in co-pending applications Serial No. 461,378, filed October 11, 1954, and Serial No. 622,042, filed November 14, 1956, and assigned to the assignee of the instant application.

I have found that I can overcome this condition by inserting barrier means across at least one of the channels which is positioned between the cooperating contacts and the openings in the associated channel wall. Thus when this contact produces ionized gas due to contact blow-off during operation of an associated current limiting fuse the ionized gas will be substantially isolated in this one channel and will not seep through the openings in the channel wall so as to communicate with contacts of another phase. In a similar manner ionized gas caused by contacts of another phase will be prevented from communicating with isolated conducting members of the phases.

I have further found it desirable to place small openings in the barrier for allowing a controlled leakage of ionized gas from the channel, so as to prevent too high a pressure from being created within the isolated portion of the channel, which pressure could eventually rupture the molded case of the circuit breaker. By way of example, I have drilled a plurality of small holes in the barrier, their area being substantially small in comparison to the cross-sectional area of the complete area. Clearly I could have used slots in the barrier for achieving the same pres sure relief function and, if desired, the combination of slots and holescould be used, as will be hereinafter described.

Accordingly, the primary object of my invention is to provide a novel structure for multi-phase molded case circuit breakers which will prevent phase to phase flashover due to the communication between the conductors of two or more phases of ionized gas.

Another object of this invention is to provide a barrier in at least one channel of a multi-phase molded case circuit breaker wherein the cooperating contacts of each phase are placed in a separate channel whereby the barrier isolates the portion of the channel containing the cooperating contacts and the portion of the channel which has openings therein for allowing interconnection between the various mechanisms.

Still another object of my invention is to provide pressure relief openings in the above mentioned barriers.

Another object of this invention is to isolate the conducting members of at least two phases of a three phase molded case circuit breaker from one another by positioning isolating barriers, having pressure relief openings therein, between the pairs of cooperating contacts and openings in their respective channels.

These and other objects of the present invention will become more apparent when taken in connection with the following description and the drawings in which:

Figure 1 is an exploded perspective View of a multiphase molded case circuit breaker having my novel barrier construction and adapted to coordinate with current limiting devices.

Figure 2 shows a side cross-sectional view taken through the barriers of the device of Figure 1 when the device is assembled.

Figure 3 shows a front view of one of the barriers of my novel invention.

Figure 4 shows a side cross-sectional view taken along the lines 44 of Figure 3.

Figure 5 shows a fragmentary view of one of the channel walls of Figure l and particularly illustrates the common operating shaft extending through an aperture in the channel wall.

Figure 1 shows a circuit interrupting device comprising a base portion 20 and a connectible cover member 22. The base portion 20 has an extension seen generally at 24, which extension carries disconnect contacts such as

disconnects

26 and 28. The

disconnects

26 and 28 cooperate with studs 3b and 32 of the current limiting device 34 which is contained in the current limiting device housing 36. The current limiting device 34 cooperates with a first circuit breaker phase including the movable contact arm 33, while a second and third current limiting device cooperates with a second and third phase including the

contact arms

46 and 42, respectively, by means of a similar stud and disconnect contact arrangement.

This type of construction is specifically set forth in my co -pending application Serial No. 622,044, filed November 14, 1956, which is now part of the instant specification, and reference can be made therto for construction details concerning the cooperation between the fuse housing 36 and the extended base 24 as well as details concerning the mechanism included as the circuit breaker base 21).

It is, however, to be noted that while the instant ap'plication will describe my invention in conjunction with a circuit interrupting device comprising a coordinated circuit breaker and current limiting device, my novel invention could be applied to any circuit breaker type device. In the case of Figure 1 the cover 22 is first fastened to the circuit breaker base 20 and the current limiting device housing 36 is thereafter connected by the heretofore described disconnect means so that each circuit breaker phase is connected in series with the corresponding current limiting device.

When the cover 22 is connected to the base 20, the channel wall 44' and side wall 46 cooperate with channel wall 48 and side wall 56 of cover 22 to form a channel which encloses contact arm 38 and the cooperating contacts associated therewith. That is to say, contact arm 3 carries a movable contact which is movable into and out of engagement with a fixed contact (not shown) and this system is enclosed by the above channel. In a similar manner channel wall 52 of circuit breaker base 26% and channel wall 54 of cover 22 cooperate so as to form a channel for the circuit breaker phase including contact arm 40, while channel walls 52 and 54 of circuit breaker base 2d and cover 22, respectively, cooperate with side walls 56 and 53, respectively, to form a channel for enclosing the cooperating contacts associated with contact arm 4-2. It is necessary, however, that contact arms 3%, it and 42 be operated from a common shaft, partially seen in Figure 1 as shaft 60.

Since the shaft 6t) must communicate with each of its respective contact arms, it is necessary that this shaft I 62 is formed to allow passage of operating shaft 60.

In view of this aperture it is now possible for ionized gas, created for example by the operation of contact arm 258 to a disengaged position, to circulate through the aperture 62 and into the area of the cooperating contacts of contact arm 40 or through both the walls 44 and 52 and into the cooperating contacts associated with contact arm 42. This condition could then lead to a phase to phase fault between the conducting members of the phase including contact arm 38 and one of the other phases.

In order to prevent this condition, I have placed my novel barrier in at least one of the above noted channels so as to isolate the movable contacts associated with the channel and the apertures in the channel wall. By way of example, Figure 1 shows my

novel barriers

64 and 66 as being fastened to the cover 22 and having an extended 4 portion which will fit into the channel members of the circuit breaker base 20.

This constructionis best seen in Figure 2 wherein the channels formed by the

members

44, 46, 48 and are enclosed by the barrier 64, While the

channel comprising member

52, 54, 56 and 58 are enclosed by the barrier member 66. Hence when the circuit interrupting device is assembled as seen in Figure 2, the barriers Will be positioned, as shown in the dotted lines of Figure 1, so as to isolate the pairs of cooperating contacts which would create ionized gas and the apertures in the associated channel walls whereby circulation of ionized gas between live conductors of a pair of phases is prevented. In the case of Figures 1 and 2, each of the three channels are isolated from one another, the two outer channels containing the barriers. The center channel which has the operating handle 74 positioned therein and contact arm 4% requires no barrier, since its respective contacts are inherently isolated because of the other two

barriers

64 and 66.

It has been found desirable that the barriers have pressure relief openings therein so as to allow a controlled leakage of ionized gas which will prevent the creation of too great a pressure'which could possibly blow the cover 22 away from the base 20 when gas is created due to contact separation. These pressure relief openings are best seen in Figures 3 and 4 in conjunction with barrier member 64 wherein four small holes 72 and a slot 74 allows a controlled leakage of ionized gas. Clearly, however, any desired type of pressure relief opening could have been utilized, the slot and hole arrangement shown in Figures 3 and 4 being for illustrative purposes only.

The slot 74 is more specifically produced by allowing a clearance between the top of cover 22 and the barrier 64 while the barrier 64 as well as the barrier 66 may be rigidly fastened to the cover 22 by any desired type of fastening means such as a slot type engagement and cementing as'is shown in Figures 2, 3 and 4.

In the foregoing I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly I prefer to be bound not by the specific disclosure herein, but only by the appended claims.

I claim:

1. In a multi-phase molded case circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; a barrier; said common contact arm shaft extending through openings in the sides of each of said channels; said barrier extending across one of said channels and being positioned between said cooperating contacts and said operating shaft; said barrier substantially preventing circulation of ionized gas from its channel to the other said channels to thereby prevent phase to phase flashover during current interruption.

2. In a multi-phase molded case circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating conta ts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels; said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase flashover during current interruption.

3. In a multi-phase molded case circuit breaker having a base and a cover connectible to said base, a pair of co operating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels and being positioned between said cooperating contacts and said operating shaft; said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel, said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase fiashover during current interruption.

4. In a multi-phase molded case circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms be ing mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels; said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel; said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase fiashover during current interruption.

5. In a multi-phase molded case circuit breaker having a base and a cover connectible to said base, a pair of cooperting contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating Contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels and being positioned between said cooperating contacts and said operating shaft; said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel, said barrier being fastened to said cover and positioned to move into its said position when said cover is fastened to said base, said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase flashover during current interruption.

6. In a multiphase molded case circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a first and second barrier extending across a first and second channel of said plurality of said channels; said barriers being positioned between their corresponding cooperating contacts and said operating shaft; said barriers having small openings therein for pressure relief functions, said barriers substantially preventing circulation of ionized gas between said cooperating contacts positioned in said channels.

7. In a multi-phase molded case circuit breaker; said molded case circuit breaker having pairs of cooperating contacts for each phase; said molded case circuit breaker having a plurality of longitudinally disposed channels, each of said pairs of cooperating contacts being disposed in a respective channel of said plurality of channels; the sides of said channels having openings therein; a barrier positioned across one of said channels and substantially enclosing said channel; said barrier being positioned between the cooperating contacts of said channel and the opening of said channel; said barrier substantially preventing circulation of ionized gas from said last mentioned pair of cooperating contacts to other channels through said opening in said last mentioned channel.

8. In a multi-phase molded case circuit breaker; said molded case circuit breaker having pairs of cooperating contacts for each phase; said molded case circuit breaker having a'plurality of longitudinally disposed channels, each of. said pairs of cooperating contacts being disposed in a respective channel of said plurality of channels; the

tween the cooperating contacts of said channel and the opening of said channel; said barrier substantially preventing circulation of ionized gas from said last mentioned pair of cooperating contacts to other channels through said opening in said last mentioned channel; said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel.

9. A circuit interrupting device comprising a multiphase molded case circuit breaker and a plurality of cur rent limiting devices removably connected to a respective phase of said multi-phase circuit breaker, said current limiting devices being constructed to operate on fault currents above a predetermined value and above the interrupting rating of said circuit breaker; said circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multiphase circuit breaker, each of said channels being substantiaily enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; a barrier; said common contact arm shaft extending through openings in the sides of each of said channels; said barrier extending across one of said channels and being positioned between said cooperating contacts and said operating shaft; said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase flashover during current interruption; said pairs of cooperating contacts being subjected to blow-off forces by the let-through current of said current limiting means to thereby produce said ionized gas at high pressure.

10. A circuit interrupting device comprising a multiphase molded case circuit breaker and a plurality of current limiting devices removably connected to a respective phase of said multi-phase circuit breaker, said current limiting devices being constructed to operate on fault currents above a predetermined value and above the in terrupting rating of said circuit breaker; said circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multiphase circuit breaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels, said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel, said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase flashover during current interruption; said pairs of cooperating contacts being subject to blow-0d forces by the letthrough current of said current limiting means to thereby produce said ionized gas at high pressure.

11. A circuit interrupting device comprising a multiphase molded case circuit breaker and a plurality of current limiting devices removably connected to a respective phase of said multi-phase circuit breaker, said current limiting devices being constructed to operate on fault currents above a predetermined value and above the interrupting rating of said circuit breaker; said circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contacts into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multi-phase circuitbreaker, each of said channels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a barrier, said barrier extending across one of said channels and being positioned between said cooperating contacts and said operating shaft; said barrier having an opening therein of relatively small area with respect to the area of said barrier for preventing too high a pressure from building up in said corresponding channel; said barrier being fastened to said cover and positioned to move into its said position when said cover is fastened to said base; said barrier substantially preventing circulation of ionized gas from its channel to the other of said channels to thereby prevent phase to phase flashover during current interruption; said pairs of cooperating contacts being subject to blow-off forces by the let-through current of said current limiting means to thereby produce said ionized gas at high pressure.

12. A circuit interrupting device comprising a multiphase molded case circuit breaker and a plurality of current limiting devices removably connected to a respective phase of said multi-phase circuit breaker, said current limiting devices being constructed to operate on fault currents above a predetermined value and above the interrupting rating of said circuit breaker; said circuit breaker having a base and a cover connectible to said base, a pair of cooperating contacts for each phase of said molded phase circuit breaker, one of said pairs of cooperating contacts for each phase being mounted on a Contact arm, each of said contact arms being pivoted on a common contact arm shaft, each of said contact arms being constructed to move one contact of said last mentioned pair of cooperating contact into and out of engagement with its cooperating contact; operating means common to each of said contact arms for moving each of said contact arms to an engaged position; said base having a channel therein for each phase of said multiphase circuit breaker, each of saidchannels being substantially enclosed when said cover is connected to said base, each of said pairs of cooperating contacts and corresponding contact arms being mounted in a respective channel; said common contact arm shaft extending through openings in the sides of each of said channels; a first and second barrier extending across a first and second channel of said plurality of said channels; said barriers being positioned between their corresponding cooperating contacts and said operating shaft; said barriers having small openings therein for pressure relief functions, said barriers substantially preventing circulation of ionized gas between said cooperating contacts positioned in said channels; said pairs of cooperating contacts being subject to blow-off forces by the let-through current of said current limiting means to thereby produce said ionized gas at high pressure.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,863,969 December 9, 1958 William Harold Edmunds It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 18, for Serial No. 622,044," read Serial No. 622,042,

Signed and sealed this 4th day of August 1959.

Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Nos 2,863,969 December 9, 1958 William Harold Edlr lunds It is hereby certified that error appears in the-printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 18, for Serial No. 622,044," read Serial No, 622,042,

Signed and sealed this 4th day of August 1959.

Attest:

KARL H. AXLINE ROBERT C. WATSON Commissioner of Patents