US2146685A - Electric circuit interrupter - Google Patents

Description

Feb. 7, 193.9. D, c PRlNcE 2,146,685

ELECTRIC CIRCUIT' INTERRUPTER Filed Dec. 24, 1935 Iravehtov: David C. Prince, bg WM Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE General Electric Com New York Dany, a corporation of Application December 24, 1935, Serial N0. 56,050

4Claims.

My invention relates to electric circuit interrupters, more particularly to interrupters of the fluid blast type wherein pressure generated by arcing at one point in lthe circuit is utilized to create a fluid blast for interrupting arcing at another point in the circuit.

In certain types of air-break circuitl interrupters," such as expulsion fuses for example, turbulence of the highly heated gases, vapors and arc products exhausting through the arc is mainly relied upon for the interrupting action. That is, notwithstanding the presence of gas ionized by arcing mixed with un-ionized gas, the turbulence of the high velocity exhaust is such that during the brief interval of current reversal and before the recovery of voltage across the gap, the continuous stream of arc products is so broken up by insulating medium that the arc cannot reestablish. However, this process is largely fortuitous and depends upon extremely turbulent mixing of the un-ionized, or insulating, and ionized gases, since the ionized gases when at pressures of the order of atmospheric pressure and higher deionize quite slowly, retaining a considerable portion of their conductivity after several cycles at commercial power frquencies.4

The principal object of my invention is the provision of an improved circuit interrupter of the aforesaid fluid blast or expulsion type wherein the eil'ect of the highly heated ionized gas on the arc to be interrupted is minimized in a posij Itive and predetermined manner. In accordancev with my invention in a structural embodiment.. thereof, a so-called dead region is provided between the pressure generating arc andthe portion of the arc subject to the fluid blast, the arrangement preferably being such-that ythe unionized gas stored in theY dead region is substantially entirely expelled and used in the fluid blast kand the ionized gas subsequently is necessarily thoroughly mixed with and cooled by any unionized gas remaining in said region and also cooled by the structure dening said dead or storage region.

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 view, mainly in section, of an electric fuse of the expulsion type embodying my invention; Fig. 2 is a sectional view of the fuse taken along the line 2-2 of Fig. 1, and Fig. 3 is a view, mainly in section, of an electric circuit breaker likewise embodying my invention.

The electric circuit interrupter illustrated by Fig. 1 constitutes a fuse of the well known expulsion type comprising a mechanically strong cylindrical insulating casing I, end terminals 2 and 3, and a fusible element 4 extending through the cylinder l and electrically interconnecting the fuse terminals. The terminals are composed of a suitable conducting material, such as copper, the terminal 2 being in the form of a cap closing one end of. the cylinder l and the terminal 3 being in the form of a ring at the open end of the cylinder. The fusible element 4, which is electrically connected in any suitable manner to the terminals, is preferably providedvwith a reduced section or equivalent thereof at 4' for insuring initial blowing of the fuse in response to predetermined current in that region of the casing.

In the apparatus so far described, the circuit interrupter functions in the conventional manner, that is by blowing of the fuse within the cylinder l accompanied by violent expulsion of thegas, metallic vapor and arc products through .the open end of the cylinder.

vFor `the purpose of forming a so-called dead region adapted to serve as a gas reservoir between the pressure generating arc, that is, the portion of the arc within the closed or pressure confining part ofl the fuse casing, and a portion of the arc in another part of said casing subject to the gas blast, there is provided a sectionalized structure 8 positioned, in the present instance, within 35 the cylinder l between the terminals 2 and 3 and between the weakened portion of fuse element 4' and the open end of ,the cylinder.

'Ihe structure 6 comprises a longitudinally positioned conducting arc member 'I to which are secured in radial position a plurality of iin-like members l, as best illustrated by Fig. 2. The iin-like members 8, which in the present instance are composed of conducting material, but which may, if desired, be composed of insulating ma- 5 terial, are of such length that they define gas spaces of appreciable volume which communicate respectively with the regions of both portions so that the ow of gas through the fuse cylinder is not appreciably restricted. 50 It will, therefore, be apparent that the specic design, including the dimensions and proportions of the intermediate structure 8, may be varied in accordance with the desired interrupting capacity and characteristics of the fuse.

In operation, excessive or predetermined current in the circuit in which theiuse is connected causes the fusible element to blow at 4' within the conned portion of the fuse casing, with the result that high instantaneous are pressure is set up within 'that part of the casing. This pressure not only causes violent ejection 'of the remainder of the fusible element from the fuse cylinder, but also a considerable volume of gas, metallicvapor and arc products at high velocity. However, upon initial blowing of the fusible element,` the arc tends to strike between the fuse terminals and the adjacent ends of the arc member 1, thereby separating th'e arc into two sections and forming a so-called dead -region unail'ected by the arc at the conducting structure 6.

Due to the expulsive action of the pressure generating arc between2 and "I, the arc within the open end of the fuse casing, that is, between the terminal 3 and the adjacent end of the arc member 1, is subjected to a uld blast composed initially, at least, mainly of the cool air or gas originally within .the dead region dened by the ns 8. Accordingly, the arc is subjected to a blast of deionized air which is substantially nonconducting and has high dielectric strength as compared with ionized gas. For normal operation, the `arc not only would be interrupted by this blast but the high dielectric strength of the cooled gas medium would prevent reestablishment of the arc when the full line voltage appears across the fuse terminals.

The structure 6 furthermore functions to cool and thoroughly mix the ionized gas blown from theV closed or pressure generating end of the fuse casing with un-ionized gas in the dead region prior to passage of this part of the uid blast through the arc gap in the open end of the tube. It will. be noted that the effective cooling area of the structure dening the dead space is large as compared with the cross-sectional area of the casing. Accordingly, the eiect of the hot ionized gas from the region of the pressure generating arc is minimized in a positive and predetermined manner prior to its passage through the gap subject to the interrupting blast.

Fig.. 3 illustrates a circuit breaker generally similar in-principle to the fuse above described. In this case, the switch casing 9 likewise comprises an insulating cylinder open at one end and closed by circuit terminal cap I at its other end. Relatively movable contact structure is disposed within the switch casing comprising, in the present instance, a fixed contact II connected to the terminal Ill, an lintermediate contact rod 1I2 guided for reciprocal longitudinal movement within the switch casing, and a movable contact I3 to which is connected an operating rod I4. The contacts II, I2 and I3 are generally in alinement, the intermediate contact I2 engaging at its opposite ends the fixed contact Il and the movable contact I3, respectively, and the movable contact I3 being electrically connected through the conducting operating rod I4 to the other terminal l5 of the breaker. The contact I2, which makes butt contact with fixed contact II, engages the movable contact I3. at a central opening I3' generally in the manner of a needle valve, i' so that separation of the contacts I2 and I3 pro'` vides an opening through thecontact I3 for exhaust of iiuid through the open end of tlie switch casing 9.

As illustrated, the breaker is in the closed cir-- cuit position and is held in such position by latch i5 operatively related to a tripping solenoid Il.

Asrin'the previous instance, a dead or unaffected region is formed between the pressure generating arc, which is formed between the contacts I I and I2, and a portion of the arc subject to the uid blast, which is formed between -the con-v tacts yI2 and I3, the arrangement comprising a plurality of fins I8 secured to and radially positioned with respect to the intermediate contact I2. The contact`I2 includes an outer sleeve I9 y isA opening movement of the contact I3. By reason of the spring 20, there is a limited following engagement between the contacts I2 and Il and immediate initial separation of the contacts vIl and I2, resul-ting in formation of the pressure generating arc within the closed or pressure confining part of the switch casing. When the sleeve, however, reaches .the shoulder 9 within the switch casing, following movement of the contact I2 is checked and separation of the contacts I2 and I3 draws another arc at that point.

The pressure initially generated is, therefore, effective immediately to cause a blast of gas through the central opening in the contact I #to exhaust from the switch casing and hence through the arc between the contacts I2 and I3. Accordingly, the un-ionized gas within the dead region deilned by -the fins I8 not only functions in the manner above described to provide a substantially un-ionized gas blast through the arc between the contacts I2 and I3, but also prevents reestablishment of arcing between these contacts in the manner described in connection with Fig. 1.

The application of my invention to a circuit breaker is obviously not limited to the specic construction shown, and, by way of example, the.

pressure generating arc could if desired be formed by a fusible element, the pressure being utilized to open the contact I3 as weil as to create the interrupting blast.

It should be understood that my invention is not limited to specific details of construction and arrangement thereof herein illustrated, and that changes and modiilcations may occur to one 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:

l. An electric circuit interrupter of the gas blast type comprising a pressure-confining casing, circuit controlling means including spaced terminals and interposed conducting arc means arranged to form in said lcasing two breaks in series in accordance with the circuit interrupting operation, one of said breaks being adjacent to an exhaust opening of said casing and the other break being more remotely positioned in said casing so as to form a pressure-generating arc, and means interposed between said breaks comprising a sectionalized gas-cooling structure having a large effective surface area as compared with' k the cross-sectional areeI of said casing, said structure forming a plurality of passages in communication with the regions of said breaks.

2. An electric circuit interrupter of the gas ex- ,pulsion type comprising a pressure-conining in accordance with the circuit-interrupting operation, one of said breaks being adjacent an exhaustl opening of said chamber, and the other area of said chamber interposed between said breaks for defining a sectionalized (as contrasted with a substantially open) space, said sectionalized space also serving as a reservoir for cool un-ionized gas and communicating with the regions of both said breaks whereby an initial charge of cool gas from said sectionalized space is projected across the arc at said exhaust opening by the pressure generated at the other arc, and the highly heated arc gases from said pressure-generating arc are subsequently effectively cooled in said structure prior to passage through the break at said exhaust opening.

3. An electric circuit interrupter'of the gas expulsion type comprising a casing, circuit terminals associated with said casing, a fusible element disposed within said casing and adapted initially to blow at a point within an enclosed part of said casing, said casing having a pressure reliei' opening at another part thereof, means positioned intermediate said terminals for segregat# ing arcing at the terminal adjacent said point of initial blowing and that adjacent to said relief opening, and gas-cooling structure disposed within said casing intermediate the regions of said arcing, said cooling structure having a large ei.'- fective surface area as compared with the crosssectional area of said casing and defining a plurality of passages communicating with said regions, said passages also serving as a reservoir for cool un-ionized gas whereby the arc pressure generated within said'casing at said point of initial blowing causes expulsion of un-ionized gas from sad passages through the other arc and the heated arc gases from said region of initial blowing are cooled prior to expulsion through said other arc.

4. A circuit breaker of the gas expulsion Itype comprising a pressure-confining chamber, relatively movable contacts arranged to form two breaks in series within said chamber in accordance with the circuit-opening operation, one of said breaks being adjacent to an exhaust opening of said chamber, and the other break being remotely positioned within said chamber so as to form a pressure-generating arc, and gas-cooling structure having a large effective surface area as compared with the cross-sectional area of said chamber interposed between said breaks defining a sectionalized (as contrasted with a substantially open) space, said sectionalized space serving also as a reservoir for cool un-ionized gas and com-r municating with both regions of arcing whereby an initial charge of cool gas from said sectionalized space is projected across the arc at said exhaust opening by the pressure generated at the -other arc, and the heated arc gases from said pressure-generating arc are subsequently effectively cooled in said structure prior to passage through the break at said exhaust opening.

DAVID C. PRINCE.

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