US2262516A - Electric circuit breaker - Google Patents

Description

Nov. 11, 1941. D. PRINCE 2,262,516

ELECTRIC CIRCUIT BREAKER Filed Dec. 19, 1940 Invent or David C. pme,

by ifm/V5 His "Attovfay Patented Nov. 11, 1941 ELECTRIC CIRCUIT BREAKER David C. Prince, Schenectady, N. Y., assignor to General Electric Company. a corporation of New York Application December 19,1940, Serial No. 370,819

(Cl. 20G-148) 6 Claims.

My invention relates to electric circuit breakers, more particularly to circuit breakers of the gas blast type wherein a blast of gas under pressure is directed through the arc formed upon separation of the breaker contacts, and has for its principal object the provision of an improved gas blast circuit breaker for high voltage circuits that is effective in applying the blast for arc interruption and that is efficient in the use of compressed gas.

My invention will be more fully set forth in the following description referring to the accompanying drawing, 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.

Referring to the drawing, Fig. 1 is a plan View of a double-break circuit breaker embodying the present invention, Fig. 2 is an enlarged View partly in section of circuit breaker structure shown in Fig. l, Fig. 3 is a sectional View of a modified form of my invention and Fig. 4 is a similar View of another form of circuit breaker embodying the present invention.

The double-break circuit breaker shown by way of example in Fig. 1 comprises a movable switch blade or bridging member I for completing the circuit between the terminals of the breaker indicated at 2 and 3. The bridging member I is preferably rotatably mounted on an insulator 4 so that after arc interruption the terminals 2 and 3 can be suitably isolated with respect to the bridge I by air gaps. The fixed terminals 2 and 3 are connected to arc extinguishing chamber housings 5 and 6 respectively, each chamber being connected through a conduit l to a suitable source of compressed gas (not shown).

When it is desired to interrupt the circuit, compressed gas is admitted to the conduits 'l to cause separation of the breaker contact structure. A shield 5 is mounted at the end of the chamber housing 5 and is provided with a centrai aperture through which a contact 8 engages the coacting shield contact 9 on the bridging member. Similarly, the chamber housing 6 is provided with a shield 6 through which the contact IU operates to engage the corresponding bridge contact I I. When the arcing caused by separation of the aforesaid pairs of contacts has been interrupted by gas blast, the bridging member I is rotated by suitable means (not shown) to the isolating position.

Fig. 2 illustrates the arcing chamber at 6 with the contacts inrclosed circuit position. The arcing chamber is formed by an insulating cylinder I2 constituting a guide for the movable rod contact I0. Thechamber passage I3 formed within the cylinder is restricted at the exhaust opening I4 so that the contact ID has a slight clearance. The shield 6' is suitably mounted on the end of the cylinder as illustrated.

The operating means for the contact IU in the present instance comprises a combined piston and valve structure I5. A piston member I6 is reoiprocally operable in an enlarged portion I'l of the cylinder arranged to be in direct communication with the gas supply conduit 1. The piston i6 has secured thereto a cylindrical portion I8 that is guided in the passage I3 so as normally to function as a valve and close that passage, with respect to the supply conduit 1. The combined piston and valve structure, which is here shown as directly connected to the movable rod contact IO, is spring biased at I9 toward the circuit closing position. The circuit through the breaker structure above described comprises the contacts II and I0, the pistonvalveY i5, spring I9 and terminal 3.

The operation of the circuit breaker is as follows. When the circuit is to be interrupted by reason of a short circuit or overload, gas under pressure is admitted to the supply conduit 1. Immediately upon admission of the pressure gas to the space Il, the piston I6 is forced toward the right against the bias of spring I9. The initial movement of the contact I0, it will be observed, causes separation of the contacts II and I0 resulting in the formation of a short power arc. However, the interrupting gas blast is delayed at this time by reason of the cylindrical valve member I8 which closes the passage I3.

I have found that this initial delay in the application of the blast may under certain conditions result in less deterioration of the switch contact structure by reason of the limited energy, i. e. heat, generated -by a short arc. That is, other things being equal, the energy or heat dissipated by an arc is proportional to the length of the arc. If now, the gas blast is prematurely directed through the arc path, the arc itselfk may be looped so as appreciably to increase the length thereof. In addition, an arc subject to an air blast has higher losses so that it develops more heat than an arc of the same length in comparatively still air. These factors combine to cause excessive generation of heat with resultant deterioration of the breaker structure. i

By premature applicationof-.the'gas'blast is meantsubjection of `thearcto the gas'blast before the arc has reached a predetermined or preferred length for most positive interrupting action. lInother words, there is an optimum forfthe'arc, length in respectto Inost effective applicationjof the' gas` blast.'l This optimum dependson thelnature of the circuit to be interrupted and is thev minimum distance that after arc interruptiony at, a current zero.

In the present case, the blast'is applied to the arc shortly after the arc has been drawn through the restricted passage at I4. The instant application of la strong high velocitygas blast at this point is effective to cause arc interruption within the restricted passage with minimum generation of heat. It will also be observed that the v consumption of compressed gas is no'lmore than that essentially required, since` a wasteful and useless premature blast-'fis eliminated.

Afterinterruption of the arc and prior to return of the contact I to closed position, the bridging member I of the breaker is rotated by suitable means toisolating position. The interrupting chamber at functions in a manner similar to that above described. It will be observed that erosion of the arc chamber at the restricted passage lI4 does not aifect normal opening of the contacts as in the case of a prior type circuit breaker wherein the build-up of pressure for operating the contacts may be hindered by leakage around the contact at the exhaust opening.

In the modification shown by Fig. 3, the arc is acted upon by a plurality of cross blast jets, instead of by a longitudinal blast. A 'plurality of strong cross blasts is very effectivein interrupting high voltage, circuits.v The. insulating switch casing 20 for the arc chamber is closed at one end by the fixed contact 2| and is provided with lateral blast passages 22 disposed along the arc path. The piston-valve structure I5 is similar to that shown in Fig. 2 and further description thereof is unnecessary. When the breaker is opened the arc is first 'formed in the passage I3 opposite the cross blast passages. is delayed by the cylindrical valve I8 so that a predetermined length of arc is opposite the cross blast jets before the'gas under pressure is admitted to the passage'I3. As in the previous case,

so that the blast is entirely directed in the most effective manner through the transverse blast passages 32. l l

It will be noted that where high pressure storage vessels are used as the source of gas supply, special reducing valves or the like for applying the pressure to the operating means for opening the breaker contacts is unnecessary. Furthermore, no gas is consumed in operating the breaker will prevent restrlkingfofthe recovery voltage contacts sinceall venting takesplace across the arc path. Y

In the case of Figs. 3 and 4, it shall be understood that suitable disconnecting or isolating means can be provided for isolating the circuit breaker after interruption of the arc.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modifications may` occur to one The application of the blast y the short arc is quickly interrupted without exn cessive generation of heat.

In Fig.4, the cross blast arrangement is further modified so that the delayed blast is more effective. The insulating casing 30 for the arc chamber is in this case provided with insulating baffies 3l extending across the path of the arc so as to provide transverse blast passages 32. These transverse passages or ports are uncovered as the contacts separate. The cross blast passages 32 are also connected directly to a passage 33 that is opened to the blast pressure only after predetermined separation of the contacts 2 I--IIL This predetermined movement is necessary to uncover the cross blast ports and corresponds to the preferred length of arc, `or optimum, above referred to. v

. The piston-valve structure I5fis in the present case modified to linclude a recessed portion at 34 arranged to connect the space at Il with the passage 33 after predetermined movement of the piston I6. The Valve portion 34 prevents escape of gas along the longitudinal axis of the arc skilled in the art Without departing from the spirit of my invention.

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

1. An electric circuit breaker of the gas blast type comprising relatively movable contacts separable to form an arc gap, means for directing a gas under pressure through said gap for interrupting arcing, and means for blocking flow of said gas through said arc gap after separation of said contacts until said gap has reached a predetermined length, said means thereupon admitting an arc interrupting blast to said gap.

2. An electric circuit breaker of the gas blast Y type comprising relatively movable contacts separable to form an arc gap, means for directing a gas under pressure through said gap for interrupting arcing, and piston structure operatively related to said contacts to cause separation thereof, said piston structure controlling ilow of said gas so that the interrupting blast is posi- *tively blocked and delayed until the contacts v sages leading to said arc gap so as to block and delay application of the gas blast until the arc gap has reached a predetermined preferred,

length for most effective arc interruption.

4, An electric circuit breaker of the gas blast vtype comprising a xed contact, and a movable contact separable to form an arc gap, passage means fordirecting a gas blast from a pressure supply source through said gap for interrupting arcing, and piston structure arranged to control said passage means leading to said arc gap so as to block and delay application of the gas blast until the arc gap has reached a predetermined preferred lengthA for most effective arc interv ruption.

5. An electric circuit breaker of the gas blast type comprising insulating structure dening an arc chamber, a vpair of contacts, one of which is movable to form an arc gap in said chamber,

means for directing a gas blast into said chamber` and through said gap for interrupting arcing, and combined valve and piston structure operatively connected to said movable contact arranged to be acted uponby said gas for causing n ports, means including a passage leading from a pressure supply source for directing a gas blast into said chamber and through said gap and exhaust ports for interrupting arcing by crossblast action, and valve structure operatively connected to said movable contact, circuit opening movement incident to separation of said contacts also operating said valve structure to control said passage so as to block and delay application of the gas blast to said chamber until the arc gap has reached a predetermined preferred length for mostI eil'ective arc interruption.

DAVm C. PRINCE.

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