US1819154A

US1819154A - Vacuum circuit breaker

Info

Publication number: US1819154A
Application number: US301271A
Authority: US
Inventors: Otto H Eschholz
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1928-08-22
Filing date: 1928-08-22
Publication date: 1931-08-18
Anticipated expiration: 1948-08-18
Also published as: DE549243C; GB317781A; FR680473A

Description

Aug. 18, 1931. o. H. EscHHoLz VACUUM CIRCUIT BREAKER Filed Aug. 22, 1928 INVENTOR CZo/fzfzvknr.

ATTORNEY gli 9 Patented Aug. 1s, 1931" UNITED sTATEs PATENT OFFICE OTTO H. ESCHHOLZ, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA VAUUM cinco-1T BREAKER.

Application led August 22, 1928. Serial No. 301,271.

My invention relates to circuit breakers and particularly to circuit breakers wherein the contact members of the circuit breaker are disposed in a vacuum.

An object of my invention is to provide a vacuum circuit breaker wherein ample space is provided for the expansion of the are without directly coming in contact with the Walls of the circuit breaker and wherein particles discharged from the arc such as ions and electrons are intercepted before they reach the side walls of the enclosure, thus cooling the arc, deionizing the space in the vicinity thereof and freeing the space within the enclosure of vapors incident to the volatilization of the contact members.

A further object is to so subdivide the arcing chamber that the length of any unob structed path along lines of force of the elec- 9 'tric field is less than the mean free path which an electron must traverse in order to ionize the gas within said arcing chamber at the operating pressures therein.

A further object of my invention is to provide a vacuum circuit breaker wherein the space between the point at which anarc is drawn within thecontacts, and the side walls of the enclosure is less than the mean-free path of the electrons discharged from the arc in order that the electrons shall be intercepted before they have reached velocities sulicient to ionize the space within the enclosure by collision with other particles.

A further object of my invention is to provide a vacuum circuit breaker wherein the circuit breaker contacts. are moved in the direction of the a-Xesthereof and wherein the enclosure is relatively shallow in the kdirection of the movement of the contact members and wherein the side walls are disposed at relatively great distances from the point at which the arc is drawn, thereby providing an enclosure that is compact and eicient for facilitating extinguishment of the arc.

A further object of my invention is to provide a vacuum type` circuit breaker wherein part or all of the enclosing walls is made flexible to provide a diaphragm which may serve as a support for the movable contact member 'ceeds a predetermined value, the arc serving to actuate electrode material that absorbs the gases within the enclosure. v

These and other objects that will be made apparent throughout the further description of my invention are attained by means ofthe circuit breaker apparatus hereinafter described and illustrated in the accompanying drawings, wherein;

Figure 1 is a vertical section through a circuit breaker embodying features of my infvention, and

Fig. 2 is a sectional view of a detail for insulating the intercepting barriers from the enclosure walls.

Referrin particularly to Figure 1, the

Ycircuit brea er comprises a supporting frame 3. mounted upon insulating pillars 4 which may be connected to any suitable switchboard or frame structure. A shallow metal casing 5 serves as an enclosure for the relatively movable contact members 6 and 7 the former being mounted upon a terminal 8 secured by welding to a plate 9. The plate9 is mounted upon an insulating illar l1 which surrounds 90 v the terminal 8, whic rests upon the end wall 12 of the enclosure 5. A vacuum-tight connection between plate 9 and insulator 11 is effected by flexible fianges 13 which are welded or soldered to the insulator as well as to the plate 9 and end wall 12 in a manner well known to those skilled in the art. 4

The movabe contact 7 is mounted upon a terminal 14 which is supported on a iexible Wall .15 of the enclosure 5', the wall 15 being 10o secured at its marginal edges by Welding. The Wall 15 is annular and made exibleby corrugations in order that a full opening movement of the movable contact 7 may take place Without causing any portion of the Wall 15 to be stressed beyond its elastic limit.

The terminal 14 carrying the contact 7 is biased to open position by mean-s of a spring 16 disposed between the supporting member 3 and the free end of a lever 17 fulcrumed upon a pivot 18 mounted upon the support 3. The circuit breaker is maintained in a closed position by means of an electromagnet 19 that is energized through a control circuit 21. The operating mechanism for the circuit breaker is here illustrated more or less diagrammatically and it will be understood that the parts Will beso designed and proportioned as to operate the contact terminal 14 under the pressure conditions existing When the enclosure is highly evacuated.

The plate 9 is yieldingly retained against displacement by means of a spring 22, the movement of the plate 9 being positively limited by an inwardly extending iange 23 disposed on the cover 2/1 which surrounds the 'insulating bushing 11. The space surrounding the insulating bushing 11 and the exposed portion of the Contact terminal 8 is filled with an insulating liquid such as oil thereby reducing the over-all dimensions of the parts supporting the contact terminal 8 by reason of the superior insulating quality of the liquid compound as compared With air.v The cap member 211is made of insulating material and is provided With a iange 25 by means of Which it is bolted to the end vvall 12 of the enclosure 5.

It has been found that When an arc is formed in a high vacuum, its perfomance is radicallydiff'erent from that of an arc drawn in air at -atmospheric pressures. The only gases present for supporting the arc are the vapors produced by volatilization-of the contact members. Electrons are discharge laterally in all directions at relatively high velocities and ample'space should be provided for the expansion of the momentary arc environing the separable contacts Without its coming in Contact with the Walls of the enclosure.

The side walls of the enclosure are, therefore, disposed at a rela-tively great distance from the point at which the arc is drawn, the distance being less than\the mean free path of the electrons under the existing vacuum conditions, thereby reducing to a minimum, the collisionof electrons tending to ionize 'the space Within the enclosure.

Conical barriers 26 are disposed Within the enclosure in substantially the manner illustrated in Figure 1, vthe barriers being superimposed and secured to the enclosure 5 by means of metal threaded inserts27 that are embedded in an insulatin'gblock 28 that is secured to the enclosure wall byA cement 29 and to deionize the arc almost instantaneously after the formation thereof. The barriers intercept electrified particles before they have attained velocities sufficient to ionize by collision any remanent gas Within the space. The space, therefore, is effectively deionized. The immediate proximity of the barriers to the arc stream provides surfaces upon Which metallic vapor subliming at the electrode surface rapidly condenses, such vapors accordingly serving as getters for any gases present in the arc space or that may have been released from the contacts and from the materials constituting the enclosure Walls.

The barriers 26 may be of insulating material or may be metallic and in either case their surfaces may be of a substance such as aluminum which has a good chemical aiiinity for such permanent gases as are likely to be present at any time in the enclosure. In such case the latter will be eliminated by chemical combination With the barrier surfaces. The barrier surfaces may also comprise a material adapted to be sublimed by the heat emanating from the arc and Which on condensing produces a getter action.

By reason of the maintenance of the high vacuum and the deionized space surrounding the contacts, the arc will be permanently extinguished substantially at the instant When the zero potential of the voltagel cycle is reached. After the arc has been extinguished, the high vacuum existing Within the enclosure Will prevent reforming of' the arc even though the contacts are separated a relatively short distance apart.

The enclosure 5 is provided with a vacuum valve 32 of the type illustrated and described in U. S. Patent #1,223,736 issued April 24, 1917 through which the enclosure may be initially exhausted. Since no claim is made to this device, a detailed description is deemed unnecessary.

In order to maintain the high degree of vacuum desirable for operation of avacuu m circuit breaker, it is necessary to prov1de a means for eliminating the gases such as those which may be released from the contacts or the material constituting the enclosure. For this urpose, I have provided a getter pump 33 t at comprises a pair of elec- I diuin of a transformer 35i. The ends of the electrodes 34 are spaced apart a suicient distance to cause an arc, which may be termed a getter arc to be drawn between them when the perssure within the enclosure attains a predetermined value. The activated elec trode material will absorb gases Within the enclosure. When the pressure within the enclosure has been reduced sufficiently for successful operation of the circuit breaker. the getter arc will automatically be eX- tinguished for the lack of gaseous particles to sustain it. Y

It will be recognized that a pump of the form just described is notthe only one which may be employed in connection with m circuit interrupter and that other suitable ypumps will be known to persons of skill in the art, which may be substituted for.' it.

While I have illustrated but one embodiment of my invention, it will be Aapparent to those skilled in the art that various changes, modifications, substitutions, additions and omissions may be made in the apparatus illustrated without departing from the spirit and scope of my invention as set forth in the appended claims.

I claim as my invention 1. In a vacuum circuit breaker, an evacuated enclosure, a plurality of spaced super- "imposed annular barriers havingr substantially centrally disposed aligned openings eX- tending transversely of the enclosure, and a pair of relatively movable contacts disposed to draw an arc in a zone between at least two of the barriers so that the arc is substantially surrounded by the boundaries of the said openings, the boundaries of said openingsbeing spaced from the electrodes a suiiicient distance to prevent contact of the ar'clldrawn between the electrodes with the barriers, and

the barriers being so positioned as to intercept electrons and gasesradiated from the arc toward parts of the enclosure Unshielded by the electrodes.

walls of the enclosure and having srbstantially centrally disposed aligned openings extendin transversely of the enclosure, and a pair o relatively movable contacts disposed to draw an arc in a zone between at least two of the barriers so that the arc is substantially surrounded by the boundaries of the said openings, the boundaries of said openings being spaced from the electrodes a suiicient distance to prevent contact of the arc drawn between the electrodes with the barriers, and the barriers being so positioned as to intercept electrons and gases radiated from the arc toward parts of the enclosure unshielded by the electrodes. ,l

In testimony whereof, I have hereunto subscribed my name this 8th day of August,

OTTO H. ESCHHOLZ.

2. In a vacuum circuit breaker, an evacdisposed to draw an arc in a zone between at least two of the barriers so that the arc is substantially surrounded by the boundaries of the said openings, the boundaries of said openings being spaced from the electrodes a suicient distance to prevent contact of the arc drawn between the electrodes with the barriers, and the barriers being so positioned as to intercept electrons and gases radiated from the arc toward parts of the enclosure unshielded by the electrodes.

3. In a vacuum circuit breaker, an evacuated enclosure, a plurality of spaced superimposed annular barriers mounted on the