US3118036A - Circuit breaker contact and arc extinguishing means - Google Patents
Circuit breaker contact and arc extinguishing means Download PDFInfo
- Publication number
- US3118036A US3118036A US209418A US20941862A US3118036A US 3118036 A US3118036 A US 3118036A US 209418 A US209418 A US 209418A US 20941862 A US20941862 A US 20941862A US 3118036 A US3118036 A US 3118036A
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- United States
- Prior art keywords
- conductor
- contact
- arc
- runner
- bight portion
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H9/00—Details of switching devices, not covered by groups H01H1/00 - H01H7/00
- H01H9/30—Means for extinguishing or preventing arc between current-carrying parts
- H01H9/44—Means for extinguishing or preventing arc between current-carrying parts using blow-out magnet
- H01H9/446—Means for extinguishing or preventing arc between current-carrying parts using blow-out magnet using magnetisable elements associated with the contacts
Definitions
- Uur invention relates to contact and arc extinguishing assemblies, and particularly to such an assembly for use in electric circuit breakers which are required to interrupt high short-circuit currents.
- a particular-ly eltective known way of interrupting an arc is to move it into an arc extinguishing device or arc chute having a number of spaced metallic plates.
- a. particularly difficult problem is to cause the arc, once created, to move quickly away from its point of formation into the stacked arc chute plates so as to be quickly cooled and extinguished thereby. lf such movement does not occur quickly enough, an undesirable amount of contact material is vaporized, and a large amount of ionized gases created, causing danger of restriking and of pole-to-pole or three-phase failure, with consequent complete destruction of the device.
- lt is an object of the present invention to provide a circuit breaker Contact and arc extinguishing assembly which will cause the arc to move quickly away from its point of inception and into an array of stacked metallic plates, to cause rapid extinction thereby.
- a Contact and are extinguishing assembly comprising a movable contact and a stationary Contact.
- movable contact is carried by an elongated contact arm.
- ri'he stationary contact is carried by an elongated terminal member, extending in a direction substantially opposite to that or the contact arm.
- Arc cooling and extinguishing means is provided adjacent the area ot meeting7 of the contacts, comprising a series of stacked, spaced metallic plates, each having a notch cut therein from one edge.
- a magnetic arc runner is also provided having a first, generally tJ-shaped, portion including a bight portion extending substantially co-planar with the stationary contact, on one side thereof.
- rlhe arc runner includes elongated side portions which extend alongside the aforesaid elongated terminal member and which have localized points of contact with the supporting terminal member at the end thereof.
- the are runner has an angular notch cut in the bight portion, whereby the arc can move an appreciable distance away from the contact proper before encountering the metallic material of the arc runner.
- FIGURE l is a side elevation View of an electric circuit breaker incorporating the invention, portions of the casing being cut away;
- FIGURE 2 is an exploded perspective view of a stationary contact assembly as utilized in FIGURE l, and
- FlGURE 3 is a plan View taken generally on the line 3 3 of FlGURE l.
- FIGURE l the invention is shown in FIGURE l as incorporated in an electric circuit breaker comprising an insulating casing having a base lll and a cover 11 of molded insulating material.
- the circuit breaker illustrated is a three-pole circuit breaker, that is, it is adapted to control electric current in three separate electric paths, each of said paths comprising a pole portion of the circuit breaker. .
- the current path through the central one of said poles only will be described. @lt will be understood, however, that the invention is equally applicable to single, two, or threepole devices, the construction at the other poles being substantially identical.
- An incoming line terminal 12. is provided, supported on the base 10 by an insert 13, connected to a first elongated terminal member 1'4 by suitable means such as by a screwv 15.
- the terminal member 14 carries a stationary contact y16, which is adapted to be contacted by a movable contact 17 which is carried by a second elongated conductor in the form of contact arm 118.
- the contact arm 18 is pivotally supported by suitable means such as by a pivot pin 19, on a main contact arm Zd.
- the contact arm 2li is attached to a contact cross-arm 21 by suitable insulated means, not shown, which serves to gang together all the corresponding contact arms of the poles ot the circuit breaker.
- the contact arm 18 is connected by a suitable fflexible connector 22 to a conductor 23, which in turn is connected to an input terminal 24 of a. current responsive assembly or trip unit 2S.
- the trip unit 25 has an outgoing or load terminal strap 26 which is connected together with a load terminal 27 to an insert 28 by suitable means such as by a screw 29.
- All of the contact arms 18 are adapted to be moved between open and closed circuit positions by suitable operating mechanism, not shown, including an operating link 3i) and a releasable member 3l releasably engaged by a latch portion 25A of the trip unit L5.
- the operating mechanism is adapted to be operated manually by means or" a manually engageable handle member 32 projecting through an aperture in the top wall of cover 1l.
- rihe trip unit 25 contains current responsive means for releasably retaining the member 3l in latched condition as shown. Upon the occurrence of predetermined current conditions, the member 31 is released, causing automatic opening of the contacts.
- the relcasable member 3l is adapted to bc re-engaged with the trip unit 25 lfollowing tripping, by movement of the manually operable handle 32 to its oli position, indicated in dotted lines.
- a series of stacked spaced metallic plates 34 are provided.
- Each. of said plates is generally rectangular and has a general-ly V-shaped notch 35, sce FIGURE 3, cut therein from one edge.
- the plates 35s are supported in ⁇ superimposed spaced or stacked relation by suitable means, not shown, such as an insulating ber supporting wall at their outer edges.
- the elongated conductor la which supports the stationary contact 16 is provided with a magnetic arc runner indicated in PlG- URE 2 generally at 36.
- the arc runner 3d is generally U-shaped, having a oight 37, which is generally co-planar with the contact 16 when the parts are assembled, see FIGURE l.
- Connected to the bight portion 37 are clongated side extensions 3b* Iwhich extend along opposite side edges of the conductor ll-i to a point adjacent the 3 end of the conductor ld which supports the contact i6.
- the bight portion 37 is generally co anar with the contact and is positioned on the side of the contact lo in which it is desired to move the are.
- the extensions 3S are provided with projections 39, which contact opposite side edge portions il of the condoctor la adjacent the contact-supporting end.
- the eight portion 37 also .has a generally U-shaped notch 37A cut therein. rl-he bight portion 37 is insulated from the corresponding portion of the conductor ld by suitable means such as by an insulating spacer di.
- a circuit breaker of the type shown incorporating the invention rated at 225 amperes nominal rating, when tested in a power system capable ot delivering 14,600 peak amperes at 600 v. under shortcircuit conditions, the short-circuit was interrupted successfully within one cycle.
- the same circuit breaker, using conventional types of arc runners either failed completely to pass the required testing by reason of destruction of the device, or caused so much burning Iand damage to the circuit breaker, including vaporization and scattering of molten particles, as to render the breaker unusai ble thereafter.
- the arc runner 36 being of generally U-sliaped configuration, and surroundthe stationary contact lo on three sides, serves to draw the are toward the bight portion of the U by its magnetic action.
- vaporization and scattering ot molten metal is avoided by the fact that no part of the runner is close to the contact lo, especially in the immediate neighborhood in which the arc is rst created. "thus, in this vicinity, the arc runner 36 comprises only the side portions 33 and the bent-over flanges 38A, neither of which is exposed directly to the newly formed are.
- lt is an important feature of the invention that, sine/e the are runner 3io* is insulated or spaced from the conductor E4 at its bight portion 37A but in contact at the ends of the extensions 33, the current path, when the arc is on the bight portion 37, is along each or the opposite sides 38 to the points of connection 3l), fnl, with the conductor ld and thence outwardly toward the line terminal end of the conductor ld.
- the current foil ows an accentuated U shape at this time, which further intensities the magnetic action, driving the arc further into the are cooling and extinguishing plates 34.
- the existence of this current path is evidenced by the fact that in shortcircuit testing, the projections 39 often become welded to the conductor dit by the action of the current.
- a Contact and are extinguishing assembly comprising:
- said are runner having a portion or said bight portion cut away whereby said are runner serves to draw an arc toward said bight portion without vaporization or melting of metallic material of said runner.
- a contact and arc extinguishing assern ly compris ⁇ ing:
- a generally U-shaped are runner carried by said termina-1 strap comprising a bight portion extending across said conductor adjacent said contact on the side thereof opposite said end portion
- An electric switch comprising:
- said arc runner including a pair of elongated side portions extending along opposite edges of said first conductor, means insulating the biUnt portion of said arc runner from said elongated conductor, means electrically connecting the extremities of said side portions to said conductor adjacent said meeting area of said contacts, and
Description
Jan- 14,1964- s. 5:.GAUTH1ER ETAL 3,118,036
CIRCIT BREAKER CONTACT AND ARC EXTINGUISHING MEANS Filed July 12, 1962 F/GJ.
/NVENTORSI fE/TH W /l/E/N, DA V/D 5. Po WELL, G50/5E E. @AUTH/5R,
By Cad/@ 7 ATTORNEY.
United States Patent O 3,118,036 ClRCUlT BREAKER CNTACT AND ARC EXTINGUISHING MEANS George E. Gauthier, Plainville, Keith W. Klein, Simsbury,
and David B. Powell, Bristol, Conn., assignors to General Electric Company, a corporation of New York Filed July 12, 1962, Ser. No. 209,418 3 Claims. (Cl. 20G-144) Uur invention relates to contact and arc extinguishing assemblies, and particularly to such an assembly for use in electric circuit breakers which are required to interrupt high short-circuit currents.
A particular-ly eltective known way of interrupting an arc is to move it into an arc extinguishing device or arc chute having a number of spaced metallic plates.
ln attempting to interrupt higher short-circuit currents in such assemblies without increasing the overall size of the assembly, a. particularly difficult problem is to cause the arc, once created, to move quickly away from its point of formation into the stacked arc chute plates so as to be quickly cooled and extinguished thereby. lf such movement does not occur quickly enough, an undesirable amount of contact material is vaporized, and a large amount of ionized gases created, causing danger of restriking and of pole-to-pole or three-phase failure, with consequent complete destruction of the device.
This problem is especially acute in circuit breakers in which the relatively movable contacts are carried by the ends of elongated conductive members extending in substantially opposite directions from the area oi meeting of the contacts, and therefore of generation of the arc. ln such an arrangement, the current path while arcing is occurring is such that there is no definite tendency of the magnetic effects of the current path on the arc to move the arc in the desired direction.
lt is an object of the present invention to provide a circuit breaker Contact and arc extinguishing assembly which will cause the arc to move quickly away from its point of inception and into an array of stacked metallic plates, to cause rapid extinction thereby.
it is another object of the invention to provide means for moving an arc quickly into a series of larc extinguishing plates without the vaporization of an excessive amount of metallic material in the process.
ln accordance with the invention in one lform, there is provided a Contact and are extinguishing assembly comprising a movable contact and a stationary Contact. The
movable contact is carried by an elongated contact arm. r
ri'he stationary contact is carried by an elongated terminal member, extending in a direction substantially opposite to that or the contact arm. Arc cooling and extinguishing means is provided adjacent the area ot meeting7 of the contacts, comprising a series of stacked, spaced metallic plates, each having a notch cut therein from one edge. A magnetic arc runner is also provided having a first, generally tJ-shaped, portion including a bight portion extending substantially co-planar with the stationary contact, on one side thereof. rlhe arc runner includes elongated side portions which extend alongside the aforesaid elongated terminal member and which have localized points of contact with the supporting terminal member at the end thereof.
in addition, the are runner has an angular notch cut in the bight portion, whereby the arc can move an appreciable distance away from the contact proper before encountering the metallic material of the arc runner.
T he invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.
ln the drawing,
ICC
FIGURE l is a side elevation View of an electric circuit breaker incorporating the invention, portions of the casing being cut away;
FIGURE 2 is an exploded perspective view of a stationary contact assembly as utilized in FIGURE l, and
FlGURE 3 is a plan View taken generally on the line 3 3 of FlGURE l.
in the drawing, the invention is shown in FIGURE l as incorporated in an electric circuit breaker comprising an insulating casing having a base lll and a cover 11 of molded insulating material. The circuit breaker illustrated is a three-pole circuit breaker, that is, it is adapted to control electric current in three separate electric paths, each of said paths comprising a pole portion of the circuit breaker. .For the purposes of the present invention, the current path through the central one of said poles only will be described. @lt will be understood, however, that the invention is equally applicable to single, two, or threepole devices, the construction at the other poles being substantially identical.
An incoming line terminal 12. is provided, supported on the base 10 by an insert 13, connected to a first elongated terminal member 1'4 by suitable means such as by a screwv 15. The terminal member 14 carries a stationary contact y16, which is adapted to be contacted by a movable contact 17 which is carried by a second elongated conductor in the form of contact arm 118. The contact arm 18 is pivotally supported by suitable means such as by a pivot pin 19, on a main contact arm Zd. The contact arm 2li is attached to a contact cross-arm 21 by suitable insulated means, not shown, which serves to gang together all the corresponding contact arms of the poles ot the circuit breaker. The contact arm 18 is connected by a suitable fflexible connector 22 to a conductor 23, which in turn is connected to an input terminal 24 of a. current responsive assembly or trip unit 2S. The trip unit 25 has an outgoing or load terminal strap 26 which is connected together with a load terminal 27 to an insert 28 by suitable means such as by a screw 29.
All of the contact arms 18 are adapted to be moved between open and closed circuit positions by suitable operating mechanism, not shown, including an operating link 3i) and a releasable member 3l releasably engaged by a latch portion 25A of the trip unit L5. The operating mechanism is adapted to be operated manually by means or" a manually engageable handle member 32 projecting through an aperture in the top wall of cover 1l. rihe trip unit 25 contains current responsive means for releasably retaining the member 3l in latched condition as shown. Upon the occurrence of predetermined current conditions, the member 31 is released, causing automatic opening of the contacts. The relcasable member 3l is adapted to bc re-engaged with the trip unit 25 lfollowing tripping, by movement of the manually operable handle 32 to its oli position, indicated in dotted lines.
For the purpose of aiding in the cooling and extinction of the arc, a series of stacked spaced metallic plates 34 are provided. Each. of said plates is generally rectangular and has a general-ly V-shaped notch 35, sce FIGURE 3, cut therein from one edge. The plates 35s are supported in `superimposed spaced or stacked relation by suitable means, not shown, such as an insulating ber supporting wall at their outer edges.
As shown particularly in FGURE 2, the elongated conductor la which supports the stationary contact 16 is provided with a magnetic arc runner indicated in PlG- URE 2 generally at 36. The arc runner 3d is generally U-shaped, having a oight 37, which is generally co-planar with the contact 16 when the parts are assembled, see FIGURE l. Connected to the bight portion 37 are clongated side extensions 3b* Iwhich extend along opposite side edges of the conductor ll-i to a point adjacent the 3 end of the conductor ld which supports the contact i6. The bight portion 37 is generally co anar with the contact and is positioned on the side of the contact lo in which it is desired to move the are.
The extensions 3S are provided with proiections 39, which contact opposite side edge portions il of the condoctor la adjacent the contact-supporting end. The eight portion 37 also .has a generally U-shaped notch 37A cut therein. rl-he bight portion 37 is insulated from the corresponding portion of the conductor ld by suitable means such as by an insulating spacer di.
in operation, upon the occurrence ot high short-circuit currents, it has been found that the are is moved quickly from its point of inception, in the area 16A of the contact le outwardly onto the bight portion 37 of the arc run ier 36 and then into the spaced are chute plates 34, quickly extinguishing the are.
For example, a circuit breaker of the type shown incorporating the invention, rated at 225 amperes nominal rating, when tested in a power system capable ot delivering 14,600 peak amperes at 600 v. under shortcircuit conditions, the short-circuit was interrupted successfully within one cycle. Under the same test, the same circuit breaker, using conventional types of arc runners either failed completely to pass the required testing by reason of destruction of the device, or caused so much burning Iand damage to the circuit breaker, including vaporization and scattering of molten particles, as to render the breaker unusai ble thereafter.
White the specitic phenomena occurring during the process of arc interruption is diiiicult to state with assurance of accuracy, it is believed that the arc runner 36, being of generally U-sliaped configuration, and surroundthe stationary contact lo on three sides, serves to draw the are toward the bight portion of the U by its magnetic action. At the saine time, vaporization and scattering ot molten metal partie-les is avoided by the fact that no part of the runner is close to the contact lo, especially in the immediate neighborhood in which the arc is rst created. "thus, in this vicinity, the arc runner 36 comprises only the side portions 33 and the bent-over flanges 38A, neither of which is exposed directly to the newly formed are.
lt is an important feature of the invention that, sine/e the are runner 3io* is insulated or spaced from the conductor E4 at its bight portion 37A but in contact at the ends of the extensions 33, the current path, when the arc is on the bight portion 37, is along each or the opposite sides 38 to the points of connection 3l), fnl, with the conductor ld and thence outwardly toward the line terminal end of the conductor ld. Thus the current foilows an accentuated U shape at this time, which further intensities the magnetic action, driving the arc further into the are cooling and extinguishing plates 34. The existence of this current path is evidenced by the fact that in shortcircuit testing, the projections 39 often become welded to the conductor dit by the action of the current.
While the invention has been shown in one particular embodiment, it will be readily appreciated that many modications thereof may readily be made, and we therefore intend by the appended claims to cover all such modicaticns as fall within the true spirit and scope of the invention.
What we claim as neviI and desire to secure by Letters Patent of the United States is:
l. A Contact and are extinguishing assembly comprising:
(a) a pair of relatively movable contacts movable into and out of engagement with each other,
(b) an elongated conductor,
(c) at least one of said contacts beinf7 carried by one ,end portion of said conductorl (d) generally U-shaped a'c runner carried by said conductor adjacent said one Contact, said arc runner having a eight portion extending across said conductor on the side of said contact away from sai end of said conductor,
(e) said biglit portion having bent over side-portions extending along each side ot said conductor to said end of said conductor, and
(f) said are runner having a portion or said bight portion cut away whereby said are runner serves to draw an arc toward said bight portion without vaporization or melting of metallic material of said runner.
2. A contact and arc extinguishing assern ly compris` ing:
(a) a movable contact,
(b) a relatively stationary contact,
(c) a conductive terminal strap supporting said stationary contact at one end thereof,
(d) a generally U-shaped are runner carried by said termina-1 strap comprising a bight portion extending across said conductor adjacent said contact on the side thereof opposite said end portion,
(e) said are runner having side portions extending alomY opposite edges ol said conductor to a point adjacent the end of said conductor, and
(f) means insulating said bight portion of said arc runner `from said elongated conductor (g) whereby the current path when an are is in Contact with said 'night portion is such as to comprise a return-bent portion tending to move said are away from said one end of said conductor, said bight portion having a portion thereof cut away to reduce melting and vaporization of metal of said runner by said are.
3. An electric switch comprising:
(fr) an insulating casing,
(b) a first elongated conductor mounted in said Casin",
(c) a relatively stationary contact mounted on said rst conductor adjacent one end thereof,
(d) an elongated contact arm pivotally mounted at one end in said casing,
(e) a relatively movable Contact carried by said contact arm at the end thereof remote from said pivotally mounted end,
(f) said contact arm and said -tirst conductor extending in opposite directions from the area of meeting of said contacts,
(g) a plurality of spaced metallic plates supported adjacent said relatively stationary contact, said plates having aligned notches cut therein from one edge thereof, said relatively movable contact being movable within the space dened by said notches,
(h) a generally U-shaped are runner carried by said first elongated conductor, said arc runner comprising a bight portion extending across said conductor sabstantially co-planar with said stationary contact,
(i) said arc runner including a pair of elongated side portions extending along opposite edges of said first conductor, means insulating the biUnt portion of said arc runner from said elongated conductor, means electrically connecting the extremities of said side portions to said conductor adjacent said meeting area of said contacts, and
(j) said bight portion of said arc runner having a portion cut away in the direction of said first elongated conductor,
(k) whereby an are generated between said relatively movable and stationary contacts is attracted toward said bight portion and into said are extinguishing and cooling plates without inciting a substantial amount of metal or" said arc runner.
No references cited,
Claims (1)
1. A CONTACT AND ARC EXTINGUISHING ASSEMBLY COMPRISING: (A) A PAIR OF RELATIVELY MOVABLE CONTACTS MOVABLE INTO AND OUT OF ENGAGEMENT WITH EACH OTHER, (B) AN ELONGATED CONDUCTOR, (C) AT LEAST ONE OF SAID CONTACTS BEING CARRIED BY ONE END PORTION OF SAID CONDUCTOR, (D) A GENERALLY U-SHAPED ARC RUNNER CARRIED BY SAID CONDUCTOR ADJACENT SAID ONE CONTACT, SAID ARC RUNNER HAVING A BIGHT PORTION EXTENDING ACROSS SAID CONDUCTOR ON THE SIDE OF SAID CONTACT AWAY FROM SAID END OF SAID CONDUCTOR, (E) SAID BIGHT PORTION HAVING BENT OVER SIDE-PORTIONS EXTENDING ALONG EACH SIDE OF SAID CONDUCTOR TO SAID END OF SAID CONDUCTOR, AND (F) SAID ARC RUNNER HAVING A PORTION OF SAID BIGHT PORTION CUT AWAY WHEREBY SAID ARC RUNNER SERVES TO DRAW AN ARC TOWARD SAID BIGHT PORTION WITHOUT VAPORIZATION OR MELTING OF METALLIC MATERIAL OF SAID RUNNER.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US209418A US3118036A (en) | 1962-07-12 | 1962-07-12 | Circuit breaker contact and arc extinguishing means |
| FR940973A FR1362897A (en) | 1962-07-12 | 1963-07-10 | Circuit breaker contact and means for extinguishing the arc |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US209418A US3118036A (en) | 1962-07-12 | 1962-07-12 | Circuit breaker contact and arc extinguishing means |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3118036A true US3118036A (en) | 1964-01-14 |
Family
ID=22778679
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US209418A Expired - Lifetime US3118036A (en) | 1962-07-12 | 1962-07-12 | Circuit breaker contact and arc extinguishing means |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US3118036A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3402273A (en) * | 1965-12-01 | 1968-09-17 | Ite Circuit Breaker Ltd | Arc chamber for circuit breakers |
| JPS5077766U (en) * | 1973-11-19 | 1975-07-05 | ||
| US4086460A (en) * | 1977-03-17 | 1978-04-25 | General Electric Company | Circuit breaker having improved line strap construction |
| US4229630A (en) * | 1980-03-17 | 1980-10-21 | Westinghouse Electric Corp. | Circuit breaker utilizing improved arc chambers |
| EP0140173A1 (en) * | 1983-10-14 | 1985-05-08 | Siemens Aktiengesellschaft | Switch part for an electrical switching device |
| US4761626A (en) * | 1984-12-26 | 1988-08-02 | Hitachi, Ltd. | Circuit breaker |
| US4970481A (en) * | 1989-11-13 | 1990-11-13 | General Electric Company | Current limiting circuit breaker contact arm configuration |
-
1962
- 1962-07-12 US US209418A patent/US3118036A/en not_active Expired - Lifetime
Non-Patent Citations (1)
| Title |
|---|
| None * |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3402273A (en) * | 1965-12-01 | 1968-09-17 | Ite Circuit Breaker Ltd | Arc chamber for circuit breakers |
| JPS5077766U (en) * | 1973-11-19 | 1975-07-05 | ||
| US4086460A (en) * | 1977-03-17 | 1978-04-25 | General Electric Company | Circuit breaker having improved line strap construction |
| US4229630A (en) * | 1980-03-17 | 1980-10-21 | Westinghouse Electric Corp. | Circuit breaker utilizing improved arc chambers |
| EP0140173A1 (en) * | 1983-10-14 | 1985-05-08 | Siemens Aktiengesellschaft | Switch part for an electrical switching device |
| US4618748A (en) * | 1983-10-14 | 1986-10-21 | Siemens Aktiengesellschaft | Switching device for electrical switching apparatus |
| US4761626A (en) * | 1984-12-26 | 1988-08-02 | Hitachi, Ltd. | Circuit breaker |
| US4970481A (en) * | 1989-11-13 | 1990-11-13 | General Electric Company | Current limiting circuit breaker contact arm configuration |
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