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Publication numberUS2580291 A
Publication typeGrant
Publication dateDec 25, 1951
Filing dateFeb 21, 1947
Priority dateFeb 21, 1947
Publication numberUS 2580291 A, US 2580291A, US-A-2580291, US2580291 A, US2580291A
InventorsFriedrich Robert E, Leeds Winthrop M
Original AssigneeWestinghouse Electric Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Circuit interrupter
US 2580291 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

1951 R. E. FRIEDRICH EI'AL 2,530,291

CIRCUIT INTERRUPTER Filed Feb. 21, 1947 2 SHEETSSHEET 1 Fig-.1.

WITNESSES: INVENTORS r oberf Fr'v'edr/k-b nd M flfhr'ap/W leads.

D 1951 R. E. FRIEDRICH ETAL 2,

CIRCUIT INTERRUPTER Filed Feb. 21, 1947 Z SI-IEETSSI-IEET 2 5972. Fig: 3.

WITNESSES.

INYENTORS 7 EaberfE FF/ea'r/ch pnd M'nf/arop 1W. eea s.

Patented Dec. 25, 1 951 UNITED STATES PATENT OFFICE IRCUI IN U T Robert E. Friedrich and Winthrop M. Leeds, Pittsburgh, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 21, 1947, Serial No. 729,934

8 Claims, '(Cl. 200-150) This invention relates to circuit interrupters in general, and more particularly, to arc ex,- tinguishing structures therefor.

A general object of our invention is to provide air improved circuit interrupter, the movable contact assembly of which is of simplified construction.

Another object is to provide an improved circuit interrupter in which special provision is incorporated to bring about the rapid interruption of intermediate and low current values, especially in the charging current range.

Another object is to provide an improved cir-.- cuit interrupter of the type establishing both pressure-generating and interrupting arcs in which a simplified axially aligned movable contact assembly is employed to simultantouslv bring about the several breaks. Preferably, piston means are employed in the interrupter to facilitate the interruption of low current arcs.

Another object is to provide an improved circuit interrupter in which an auxiliary constricted arc passage is employed into which the pressuregenerating arc is drawn to assist in the extinction thereof.

Further objects and advantages will readily become apparent upon a reading of the following specification taken in conjunction with the drawings, in which:

Figure 1 is a side elevational view, partially n in section, of a circuit interrupter embodying our invention and shown in the closed circuit position;

Fig. 2 is an enlarged vertical sectional view through the left-hand arc extinguishing unit of Fig. 1, the contacts being shown in the closed circuit position;

Fig. 3 is a vertical sectional View taken along the line IIIII I of Fig. 2, the contacts being shown in the partially open circuit position;

Fig. 4 is a sectional view taken along the line IV-IV of Fig. 2; and

Fig. 5 is a sectional view taken along the line V-V of Fig. 2.

Referring to the drawings, and more particularly to Fig. 1 thereof, the reference numeral 4 designates a tank filled to the level 2 with a suitable arc extinguishing fluid 3, in this instance circuit breaker oil. Depending from the cover 4 of the tank 1 are two insulating terminal bushings '5 to the lower ends of which arerigidly secured identical arcextinguishing :units, generally designated by the reference-numeral 6 and shown more clearly in Figs. '2 and 3.

The extinguishing'units '6 of Fig. 1 are elec- 2 trically interconnected in the closed circuit position, as shown in Fig. 1, by a conducting crossbar I actuated vertically in a reciprocal manner by an insulating lift rod 8.

Referring more particularly to Figs. 2 and 3, it Will be apparent that we have provided a first relatively stationary contact 9 pivotally mounted at ID by the brackets ll integrally formed with the top metallic plate l2 of the unit 6. A flexible shunt 1,3 interconnects the stationary contact 9 with the metallic plate I 2 and hence to the con,- tact foot Hi. The contact foot 14 is threadedly secured, as at l5, to the lower end of the terminal stud extending interiorly through the terminal bushing 5.

Cooperating with the first relativelystationary contact 9- is a first movable rod-shaped contact it which is spaced by an insulating portion I 7 from a second movable rod-shaped contact E8, the first and second movable contacts together with the insulating portion ll being avially alignedand constituting a rod-shaped movable contact assembly, generally designated by the reference numeral 19. The lower end of the movable contact assembly l-9 comprises conducting rodshaped member 29 having a flange 2| rigidly secured thereto, as by welding or the like, which provides a lower seat for a "compression spring 22, the upper end of which seats against a metallic plate 23 disposed at the lower end of the unit 6. Consequently, the movable contact assembly I9 is biased downwardly in the circuit opening direction and is maintained in its upper position 'by the engagement therewith of the conducting cross-bar 7.

Suitable plate or other structure is provided to establish a vented interrupting chamber 24 in which the interrupting are 25 is established between the first relatively movable contacts e, [5. Also, a-substantially confined pressure-generating chamber 26 is provided in which the pressuregenerating are 21 is established by being drawn between the second movable contact [8 and a second relatively stationary gohtract 2 8.

We have provided means electrically interconnecting the second relatively stationary contact 28 with thejirs t movable contact IS during the opening operation so that the two arcs may be s erially related. More specifically, we have provided bridging contact means, generally designated by the reference numeral 29, and including a conducting cylinder 30 having slider contacts 3| associated with its upper end. The

slider contacts -3 'l are preferably biased into contacti-ng engagement with the rod-shaped first movable contact [6 by circular leaf-springs 32. Preferably, the second relatively stationary contact 23 also consists of segmental contacts biased inwardly by circular leaf-springs 32.

The cylinder 30 constitutes a piston chamber, generally designated by the reference numeral 33, in which a piston member 34 moves, being biased downwardly in the circuit opening direction by biasing means, assuming in this instance the form of a compression spring 35. The compression spring 35 is interposed between the top side of the piston 34 and a metallic ring-shaped plate 35 welded into position within the cylinder 30. A flange 3'5, integrally formed with the first movable contact 16, is employed to pick up the piston 34 during the closing stroke and to charge the piston means 38 against the downward biasing action exerted by the compression spring 35.

It will be noted that the insulating portion I1 is exteriorly provided with surface corrugations,

generally designated b the reference numeral 39, I

and in this instance assuming the shape of a plurality of integrally formed stacked washers having diiferent external diameters.

It will be noted that adjacent the lower end of the unit 6 we have provided a constricted arcing passage, generally designated by the reference numeral 45, and formed by the positioning of a plurality of insulating washers 4|, 42 of different internal diameter disposed in contiguous relationship. A closure member 42a closes the arcing passage 4!] at the lower-end thereof. Tie rods 43 serve to hold the several plates together in compressed relationship.

A portion of the plate structure has formed therein kidney-shaped openings 44' which upon alignment cooperate to form a pair of vertical flow passages, generally designated by the reference numeral 45. The vertical fiow passages 45 constitute passage means interconnecting the piston chamber 33 and the constricted arcing passage 40 with the interrupting chamber 24. The plate structure forming the interrupting chamber 24 includes three types of plates. The first type is herein designated an insulating orifice plate and is designated by the reference numeral 45. The configuration of the orifice plate 46 is more clearly shown in Fig.5. It will be observed that the plate 46 has the kidney-shaped openings 44 provided therein and also has formed therein an orifice 4! through which the first movable contact lfi is moved.

The second type of plate employed in the interrupting chamber 24 is herein termed an insulating inlet plate 48, and has a configuration more clearly shown by the dotted lines in Fig. 5. The insulating plate 48 has a cutout portion 49 provided therein which permits communication between the vertical flow passages 45 and the interrupting are 25, the latter being drawn through the orifices 41. The third type of plate in the interrupting section 24 is herein termed a vent plate, and is generally designated by the,

reference numeral 50. The vent plate 50 is a composite plate and is formed by the cooperation of two insulating halves the configuration of which is more clearly shown in Fig. 5. Referring to this figure, it will be observed that each half 5| has a kidney-shaped opening 44 provided therein. Also, the two plates 5| are spaced laterally apart to provide opposed vent passages 52 leading in opposite directions out of the unit 6.

Certain features of the interrupting chamber construction are set forth in U. S. patent appli- 4 cation, Serial No. 465,244, filed November 11, 1942, now U. S. Patent 2,406,469, issued August 27, 1946, to Leon R. Ludwig, Winthrop M. Leeds, and Benjamin P. Baker, and assigned to the assignee of the instant application.

The operation of our improved interrupter will now be explained. In the closed circuit position of the interrupter, as shown in Figs. 1 and 2, the electrical circuit therethrough includes contact foot l4, metallic plate l2, flexible shunt l3, first relatively stationary contact 9, first movable interrupting contact l6, slider contacts 3|, circular leaf-springs 32, conducting cylinder 38, circular leaf-springs 32 to the second relatively stationary contacts 28, second movable rod-shaped contact 18 through the conducting cross-bar I to the right-hand arc extinguishing unit 6. The circuit extends through the right-hand are extinguishing unit 65 in an identical manner to its passage through the left-hand arc extinguishing unit 5 to the right-hand terminal stud of the interrupter. During the opening operation, suitable means not shown, but which is responsive to either manual operation or to excessive current conditions in the circuit controlled by the interrupter, causes downward opening motion of the lift rod 8.

The downward motion of the lift rod 8 causes corresponding downward opening movement of the cross-bar 1 to permit the compression spring 22 to cause downward following motion of the movable contact assembly I 9. This causes simultaneously the establishment of an interrupting are 25 between the contacts 9, I5 and a pressuregenerating are 2'! between the contacts 28, I8. Assuming the current conditions to be high, the considerable pressure established by the are 21 within the pressure-generating chamber 25-will act through the vertical flow pas ages 45, through apertures 53 in cylinder 39 into the piston chamber 33 to stall the piston 3 and prevent the downward movement thereof. The considerable pressure thus established within the pressuregenerating chamber 25 will force fluid, in this instance oil, to pass upwardly through the vertical flow passages 45 to pass radially inwardly toward the interrupting are 25 within the cut-out portions 49 of the insulating inlet plates 48. The oil, after contacting the interrupting are 25, passes through the orifices 41 provided by the insulating orifice plates 45 to pass out of the unit 6 through the opposedvent passages 52 provided by the vent plates 50. Circuit interruption soon follows, and upon a subsidence of the pressure within the unit 5, the piston 34 will be moved downwardly within the piston chamber 33, as caused by the compression spring 35, to force a flushing flow of oil upwardly through the passages-45 into the interrupting chamber 24 and out of the unit 6 through the vent passages 52.

During the interruption of relatively low currents where the pressure generated by the are 21 within the pressure-generating chamber 26 is relatively low, the piston 34 will be effective to cause oil flow from the piston chamber 33 through the apertures 53 (Fig. 3) and upwardly, as indicated by the arrows in Fig. 3, toward the interrupting are 25 to effect the extinction thereof in a manner as previously described.

It sometimes happens that intermediate current values are sufiicient to stall the piston 34' but create insufficient pressure within the pressure-generating chamber 26 for strong oil flow toward the interrupting chamber 24 to bring about prompt arc interruption of the are 25. Our invention includes the provision of a constricted arcing passage 40, in this instance assuming the form of an annular piston chamber 54. The pressure-generating are 21 is drawn downwardly into this constricted arcing passage 48 or chamber 54 and is subjected to a longitudinal flow of oil therein as caused by the downward piston action of the insulating portion 11. The annular corrugations provided both on the insulating portion I! and on the walls of the arcing passage 40 provide a readily accessible quantity of oil to be acted upon by the pressure-generating are 21. The provision of these corrugations a so prevents carbonization and consequent electrical breakdown along the insulating portion I? and also along the vertical walls of the arcing passage 40. Thus, the insulating portion [1 of the movable contact assembly I9 displaces oil as it moves into the restricted chamber 43 subjecting the pressure arc 21 within this chamber to a deionizing flow of oil to assist in arc interruption.

Preferably, in order to permit free upward or downward travel of the piston member 34 we provide one or more passages 55 connecting the top side of the piston member 34 with the region exterior to the unit 6.

A compression spring 56 is preferably provided biasing the first relatively stationary contact 9 downwardly so as to create the requisite contact pressure in the closed circuit position as shown in Fig. 2. A gas relief valve 51 may also be provided being spring-biased to the open position to permit egress of gas out of the dome-shaped contact foot [4. During circuit interruption, the pressure will close the valve 51. An over-pressure valve 58 may also be employed to limit the pressure.

From the foregoing description, it will be apparent that we have provided an improved circuit interrupter of the type establishing simultaneously a pressure-generating arc and an interrupting are by the incorporation of an internal insulating section I! disposed between the first and second movable contacts I6, [8 of the movable contact assembly [9. This provides high speed operation without the complication of a lever system or external operating rods. We have also given special attention to the rapid interruption of low magnetizing and line-charging currents by the provision of the piston means 38, driven by a spring 35 and charged during the closing stroke by upward closing movement of the movable contact assembly !9. During high current interruptions, back pressure will stall the piston 34 but still there will be flushing oil flowing following the subsidence of pressure within the unit 6. Low current interruptions are obtained by the action of the piston means 38 and also by the drawing of the pressure-generating arc 2'! downwardly into the constricted. arcing passage 46. tive interrupter in which special provision for adequate deionizing oil flow is provided in each part of the current range; low, medium, and high.

Although we have shown and described a specific structure, it is clearly to be understood that the same was merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art, without departing from the spirit and scope of the appended claims.

We claim as our invention:

'1. In a circuit interrupter, a rod-shaped movable contact assembly including a first rod- Thus, we have provided an effec-' shaped movable contact and a second rod-shaped movable contact separated by an insulating portion, relatively stationary contact structure including first and second relatively stationary contacts, slider contact means electrically interinterconnecting the first rod-shaped movable contact with the second relatively stationary contact during the opening operation, means forming a pressure-generating chamber and an interrupting chamber, passage means interconnecting the two chambers, the first movablecontact being separable from the first relatively stationary contact to draw an interrupting arc withthe interrupting chamber, the second movable contact being separable from the second relatively stationary contact to establish a pressureg-cnerating are within the pressure-generating chamber, means defining a constricted arcing chamber through which the rod-shaped movable contact assembly moves, the pressure-generatin are drawn between the second relatively stationary and movable contacts being drawn into the constricted arcing chamber, the surface of the insulating portion being grooved and movable into the constricted arcing chamber to force fluid longitudinally of the constricted arcing chamber adiacent the pressure-generating arc therein by piston action.

2. In a circuit interrupter, an arc extinguishing unit including means defining a pressuregenerating chamber and a vented interrupting chamber, passage means interconnecting the two chambers, a relatively stationary first contact disposed at one end of the unit, a movable rodshaped contact assembly movable longitudinally of the unit and carrying first and second movable contacts spaced by an insulating portion, the first stationary and movable contacts cooperating to establish an interrupting arc Within the interrupting chamber, the second movable contact being positioned adjacent the lower end of the unit, a second relatively stationary contact being positioned adjacent the lower end of the unit, an annular piston chamber associated with the pressure-generating chamber and having surface corrugations on the walls thereof through which the movable contact assembly moves, the are drawn between the second relatively stationary and movable contacts being a pressuregenerating arc and initially drawn within the pressure-generating chamber and subsequently drawn into the piston chamber, the insulating portion confining the presure-generating are within the piston chamber by piston action, and slider contact means electrically interconnecting the second relatively stationary contact with the first movable contact during the opening operation so that the two arcs will be serially related.

3. In a circuit interrupter of the liquid break type, an arc extinguishing unit, a relatively stationary first contact disposed at one end of the unit, a movable rod-shaped contact assembly movable longitudinally of the unit and carrying first and second movable contacts spaced by an insulating portion, the second movable contact being positioned adjacent the lower end of the unit, a second relatively stationary contact being positioned ad acent the lower end of the unit, an annular piston chamber having surface corrugations on the walls thereof through which the movable contact assembly moves, the are drawn between the second relatively stationary and movable contacts being drawn into the piston chamber, the insulating portion confining the arc within the piston chamberby piston action,-

slider contact means electrically interconnecting the second relatively stationary contact with the first movable con-tact during the opening operation so that the two arcs will be serially related, means defining a vented interrupting chamber within which the interrupting arc is drawn by the first relatively stationary and movable contacts, means defining a substantially confined pressure-generating chamber adjacent the intermediate portion of the unit within which the pressure-generating arc is drawn between the second relatively stationary and movable contacts, and liquid fiow passage means interconnecting the pressure-generating chamber with the interrupting chamber.

I 4. A circuit interrupter of the liquid break type including means defining a substantially confined pressure-generating chamber and a vented interrupting chamber, relatively stationary contact structure including first and second spaced relatively stationary contacts, a cooperating movable contact assembly including first and second relatively movable contacts spaced'by an insulating portion, the first relatively movable contact separating from the first relatively stationary contact to establish an interrupting arc within the vented interrupting chamber, the second relatively movable contact separating from the second relatively stationary contact to establish a pressure-generating arc within the substantially confined pressure-generating chamber, means electrically connecting the second relatively stationary contact to the first relatively movable contact during the opening operation so that the two arcs will be serially related, liquid passage means interconnecting the substantially confined pressure-generating chamber with the vented interrupting chamber so that liquid under pressure from the pressure-generating arc may fiow toward the interrupting arc to effect the latters extinction, a constricted arcing passage closed at one end by a closure member and communicating at its other end with the substantially confined pressure-generating chamber, actuating means for the movable contact assembly including a rod shaped member secured to the second relatively movable contact and passing axially through the constricted arcing passage, the rod-shaped member also passing through an aperture provided in the closure member, the cross-sectional area of the insulating portion being greater than the cross-sectional area of the rod-shaped member so that when the pressure-generating arc is drawn into the constricted arcing passage piston action of the insulating portion takes place to provide a longitudinal forced fiow of liquid adjacent the pressure-generating arc to facilitate the latters extinction.

5. A circuit interrupter of the liquid break type including means defining a substantially confined pressure-generating chamber and a vented interrupting chamber, relatively stationary contact structure including first and second spaced relatively stationary contacts, a cooperating rodshaped movable contact assembly including a first rod-shaped movable contact and a second relatively movable contact spaced by a rodshaped insulating portion, the first relatively movable rod-shaped contact separating from the first relatively stationary contact to establish an interrupting arc within the vented interrupting chamber, the second relatively movable contact separating from the second relatively stationary contact to establish a pressure-generating are within the substantially confined pressure-gen crating chamber, means electrically connectingthe second relatively stationary contact to the first relatively movable rod-shaped contact dur ing the opening operation so that the two arcswill be serially related, liquid passage means interconnecting the substantially confined pressure-generating chamber with the vented inter-- member, the cross-sectional area of the rod-' shaped insulating portion being greater than the cross-sectional area of the rod-shaped member So that when the pressure-generating arc is drawn into the constricted arcing passage piston action of the insulating portion takes place to provide a longitudinal forced fiow of liquid adjacent the pressure-generating arc to facilitate the latters extinction.

6. A circuit interrupter of the liquid break type including means defining a substantially confined pressure-generating chamber and a vented interrupting chamber, relatively stationary contact structure including first and second spaced relatively stationary contacts, a cooperating movable contact assembly including first and second relatively movable contacts spaced by a corrugated insulating portion, the first relatively movable contact separating from the first relatively stationary contact to establish an interrupting arc within the vented interrupting chamber, the second relatively movable contact separating from the second relatively stationary contact to establish a pressure-generating arc within the substantially confined pressure-generating chamber, means electrically connecting the second relatively stationary contact to the first relatively movable contact during the opening operation so that the two arcs will be serially related, liquid passage means interconnecting the substantially confined pressure-generating chamber with the vented interrupting chamber so that liquid under pressure, from the pressure-generating arc may flow toward the interrupting arc to effect the latters extinction, a constricted internally corrugated arcing passage cl-osed at one end by a closure member and communicating at its other end with the substantially confined pressure-gencrating chamber, actuating means for the movable contact assembly including a rod-shaped member secured to the second relatively movable contact and passing axially through the constricted internallycorrugated arcing passage, the rod-shaped member also passing through an aperture provided in the closure member, the

cross-sectional areas of the corrugated insulating portion being greater than the cross-sectional area of the rod-shaped member so that when the pressure-generating arc is drawn into the constricted internally corrugated arcing passage piston action of the insulating portiontakes;

place to provide a longitudinal forced fiow of liquid adjacent the pressure-generating arc to facilitate the latters extinction.

relatively movable contact spaced by a rod-. shaped corrugated insulating portion, the first relatively rod-shaped movable contact separating from the first relatively stationary contact to establish an interrupting are within the vent-j ed interrupting chamber, the second relatively movable contact separating from the second relatively stationary contact to establish a pressure-{- generating are within the substantially confined pressure-generating chamber, means electri-l cally connecting the second relatively stationary contact to the first relatively rod-shaped movable contact during the opening operation so that the two arcs will be serially related, liquid passage means interconnecting the substantially confined pressure-generating chamber with the vented interrupting chamber so that liquid under pressure from the pressure-generating arc may flow to-,

ward the interrupting arc to effect the latters ex-' tinction, a constricted internally corrugated arc-J, ing passage closed at one end by a closure mem-; her and communicating at its other end with the substantially confined pressure-generating cham-' ber, actuating means for the rod-shaped movablev contact assembly including a rod-shaped mem-;

ber secured to the second relatively movable contact and passing axially through the constricted internally corrugated arcing passage, the rodshaped member also passing through an aperture: provided in the closure member, the crosssectional area of the rod-shaped corrugated in sulating portion being greater than the crosssectional area of the rod-shaped member so that when the pressure-generating arc is drawn into the constricted internally corrugated arcing pas; sage piston action of the insulating portion takes, place to provide a longitudinal forced flow of liquid adjacent the pressure-generating arc to facilitate the latters extinction.

8. A circuit interrupter of the liquid break type including means defining a substantially confined pressure-generating chamber and a vented interrupting chamber, relatively station-F ary contact structure including first and second spaced relatively stationary contacts, a cooper; ating movable contact assembly including first and second relatively movable contacts spaced by an insulating portion, the first relatively movable contact separating from the first relatively stationary contact to establish an interrupting are within the vented interrupting chamber, the second relatively movable contact separating from the second relatively stationary contact to establish a pressure-generating are within the substantially confined pressure-generating chamber, means electrically connecting the second relatively stationary contact to the first relatively movable contact during the opening operation so that the two arcs will be serially related, liquid passage means interconnecting the substantially confined pressure-generating chamber with the vented interrupting chamber so that liquid under pressure from the pressure-generating arc may flow toward the interrupting arc to efiect the latters extinction, piston means including a piston chamber disposed between the first relatively stationary contact and the second relatively stationary contact through which the movable contact assembly moves, a piston disposed within the piston chamber and freely movable independently of the movable contacts, the piston chamber communicating with the aforesaid liquid passage means so that liquid forced by the working motion of the piston will flow in the same direction through the liquid passage means as the liquid flowing from the pressure-generating are, means biasing the piston to move within the piston chamber, and means movable with the movable contact assembly for picking up the piston on the closing stroke and charging the same against the biasing action exerted by the biasing means.

ROBERT E. FRIEDRICH. WINTHROP M. LEEDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,077,338 Lingal et al Apr. 13, 1937 2,098,801 Erben Nov. 9, 1937 2,138,382 Leeds et al. Nov. 29, 1938 2,158,846 Balachowsky May 16, 1939 2,199,607 Bakken May 7, 1940 2,253,009 Baker Aug. 19, 1941 2,372,589 Leeds Mar. 27, 1945 2,412,897 MacNeill Dec. 17, 1946

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2077338 *Sep 12, 1934Apr 13, 1937Westinghouse Electric & Mfg CoCircuit interrupter
US2098801 *Mar 12, 1937Nov 9, 1937Gen ElectricHigh voltage electric circuit interrupter
US2138382 *May 28, 1937Nov 29, 1938Westinghouse Electric & Mfg CoCircuit breaker
US2158846 *Feb 4, 1937May 16, 1939Gen ElectricElectric circuit breaker
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3214554 *Jul 6, 1960Oct 26, 1965Westinghouse Electric CorpArc-extinguishing grid structure for fluid-blast circuit interrupters
US4562324 *Mar 29, 1984Dec 31, 1985S&C Electric CompanyElectrical contact for use in a current-interrupting unit
US4806932 *Mar 11, 1986Feb 21, 1989Entropy, Inc.Instrument landing and takeoff system
Classifications
U.S. Classification218/103, 200/260
International ClassificationH01H33/88, H01H33/98, H01H33/70, H01H33/92
Cooperative ClassificationH01H33/98, H01H33/92
European ClassificationH01H33/92, H01H33/98