US3141082A - Circuit breaker having improved arc runner of magnetizable material - Google Patents

Description

July 14, 1964 J. sA HOLLYDAY 3,141,082

cRouIT BRENNER HAVING INRRovED ARC RUNNER oF MAGNETIZABLE MATERIAL Filed May 15, 1961 #9- 45 INVENTOR.

JOSEPH 5. Hoz Y0/1y United States Patent() 3,141,082 CIRCUIT BREAKER HAVING IMPROVED ARC RUNNER OF MAGNETIZABLE MATERIAL lIosepli S. Hollyday, Pennington, NJ., assignor to Heinemann Electric Company, Trenton, NJ., a corporation of New Jersey Filed May 1S, 1961, Ser. No. 110,241 2 Claims. (Cl. 20G-147) This invention relates to electric circuit breakers and more particularly to an improved magnetizable grid arrangement for controlling the eelctric arcs that tend to arise between circuit breaker contacts upon the separation of the contacts.

It is an object of this invention to provide an improved arc runner of magnetizable material which will control electric arcs by moving the arc along the contact face, the improved arc runner being of small size and easily adapted to miniature circuit breakers.

The arcs which tend to form upon the separation of the contacts in a circuit breaker may be controlled and extinguished by a number of diierent methods. Some of these methods are: (l) the cooling of the arc, for instance, by moving it into an area of cool gases or causing the arc to move along the contacts or to impinge upon a relatively cooler member, (2) the lengthening of the arc, (3) the moving of the arc into an area having a neutral gas, and (4) the breaking of the arc into a number of smaller arcs.

The magnetizable grid arrangement of the present invention provides a magnetizable arc runner, in physical contact with one of the contacts, and partially surrounding the contact, for creating a zone of high ux density and a zone of low liux density as close to the associated contact as is physically possible. Since an electric current tends to move away from the zone of high ilux density and into the zone of low flux density, the arc is caused to move along the face of the contact for controlling and extinguishing the arc, in accordance with the foregoing iirst three enumerated methods.

In addition, a series of magnetizable, spaced grids are associated with the arc runner onto which the arc moves and breaks into a series of smaller arcs, to take advantage of the last mentioned method of controlling and extinguishing an arc.

lt is another object of the invention to provide a circuit breaker in which the improved form and arrangement of the magnetizable arc runner also aids in arc extinction by facilitating the transfer of heat by conduction away from the stationary contact and the arc.

The foregoing and other objects of the invention, the

principles of the invention, and the best modes in which ly have contemplated applying such principles will more fully appear from the following description and accompanying drawings in illustration thereof.

In. the drawings,

FIG. 1 is a side view of a circuit breaker mechanism embodying the invention, the circuit breaker being shown partly in vertical section and partly in elevation, and the circuit breaker mechanism being in the closed position of the contacts;

FIG. 2 is a fragmentary top plan view, partly in section, taken Ialong the line 2-2 in FIG. l;

FIG. 3 is a fragmentary, cross-sectional view of the contacts portion of the circuit breaker, partly in elevation, illustrating the contacts in the open position;

FIG. 4 is a sectional view, partly in elevation, taken along the line 4--4 of FIG. 3; and

FIG. 5 is a View, similar to FIG. 4, but illustrating a modification of this invention.

The invention is embodied in a circuit breaker com- ICC prising a metallic outer casing 10 and an inner casing 11 enclosinga circular stationary contact 12, having a flat contact face 13, and a circular movable contact 14, having a curved contact face 15. However, the diameter and thickness of the movable contact 14 is smaller than those of the stationary contact 12.

The action of the movable contact 14 on predetermined overload is set forth in Patent No. 2,360,922 and patent application Serial No. 40,380, now Patent No. 3,098,910. Such mechanism therefore does not form part of the invention but for claritys sake may be briey described as follows-the movable contact 14 is carried on the end of an arm 16 which is biased by a spring 17 toward the open position of the contacts 12 and 14. The arm 16 is connected by a pintle 1S to a latching mechanism 19 which is in turn connected to a handle 20, the latter being pivoted about a fixed pintle 21. When the handle 20 is rotated clockwise, as viewed in FIG. 1, the latching mechanism 19 and the arm 16 all move to the left and move the contact 14 out of engagement with the contact 12, the vcontacts 12 and 14 assuming the position illustrated in FIG. 3.

If the contacts are in the position illustrated in FIG. 3, when the handle 20 is rotated counterclockwise, as viewed in FIG. l, the latching mechanism 19 and the arm 16 all move to the right, against the bias of the spring 17, the contacts 12 and 14 assuming the position illustrated in FIG. l.

Upon the occurrence of a predetermined overload condition, assuming the circuit breaker to be in the closed position of the contacts, FIG. l, the armature member 26 yis magnetically attracted toward the permeable pole piece 22 forming a part of the magnetic flux circuit for the magnetic flux generated by the solenoid coil 23, with which the permeable pole piece is associated. This movement of the armature 26 against the pole piece 22 and about the pintle 24, causes the oppositely extending member 25 (secured to the armature 26) to move upwardly and trip the transverse arm 27 forming part of the half-moon shaped latching pintle 28, so that the latching mechanism 19 is free to collapse under pressure from the spring 17. As illustrated in FIG. l, when the contacts 12 and 14 are engaged, the arm 27 is located immediately above the unlatching member 25 for the aforesaid purpose.

To prevent the arc that tends to form between the contact faces 13 and 15 whenever the movable contact 14 is moved away from the stationary contact 12 or to quench the arc that may have already been initiated by the movement of the movable contact, this invention provides a U-shaped magnetizable arc runner grid member 30, abutting the stationary contact 12 on three sides, and two magnetizable grids 35 and 36 spaced from each other and the arc runner 30, and positioned with respect to the stationary and movable contacts 12 and 14, as illustrated. The arc runner 30 has a pair of parallel legs 38 connected by a base or bight 39 and the grids 35 and 36 similarly each have a pair of legs 41 and a base or bight 42. The legs 3S extend downwardly tangential to diametrically opposite peripheral surfaces of the contact 12, and are cotcrminous with the lowest edge thereof, for establishing a concentrated magnetic flux iield in the air gap overlying the lowest edge portion of the stationary contact face 13 and also, across and below, but immediately adjacent, the lowest peripheral surface thereof, as illustrated by the dot-dash lines in FIG. 4. The inner surfaces of the legs 38 and the bight 39 are in intimate physical contact with the upper half of the cylindrical outer surface of the stationary contact 12 for establishing a zone of little to no magnetic tlux in the air overlying and, also, immediately above and adjacent the upper half of the contact 12, FIG. 4. Also, the grids 35 and 36 are positioned relative to the path of the movable Contact 14 so that the legs 41 are coterminous with the lowest edge portion thereof. Thus, zones of suciently unequal magnetic ux density are created adjacent the stationary contact 12 to cause the arc to move toward the bights 39 and 42.

The height of the arc runner 39, dimension A, between the stationary contact 12 and the upper inner casing wall 51, is made equal to or larger than the width, dimension B, of each of the legs 38, as illustrated. Since the thickness of the arc runner 30 is uniform, the cross-sectional area and mass, above the arc, through which the magnetic flux flows will be equal to or greater than the crosssectional area and mass (on the sides of the arc) dened by each of the legs 38. The foregoing in conjunction with the fact that the magnetic flux must bridge the ends of the legs 3S, by flowing through the air, creates a zone above the arc of less flux density than below the arc. It is to be noted that the arc does not tend to move toward the legs 38, because the symmetrical legs 3S provide zones of equal ux density to the right and left of the arc, as viewed in FIG. 4. Although, it has been determined experimentally that the aforementioned movement of the arc due to the varying tiux density Zones, takes place if the height of the bight 39, dimension A, is equal to the width of the legs 38, dimension B, FIG. 4, for an arc runner of uniform thickness, a more efficient arc extinguisher results if the bight 39 height is double or more the width of one of the legs 38.

The arc runner 30 and the grids 35 and 36 extend between opposed insulating plates 45 and 47 and are retained therein by integral lugs 49 extending into suitable openings therein, the plates 45 and 47 being formed from vulcanized liber. The legs 38 of the arc runner 3i) are constructed so that they occupy substantially all of the Space between the outer peripheral surface of the stationary contact 12 and the opposed plates 45 and 47 and all of the space between the outer peripheral surface of the stationary contact 12 and the adjacent upper Wall 51 of the inner casing. Since the arc runner 30 is disposed in abutment with the right hand inner wall 53, the arc runner 30, in effect, closes the right hand end of the arc chute between plates 45 and 47, except for the portion below the contact 12 and between the legs 38.

Since the inner surfaces of legs 38 and the bight 39 are in intimate physical contact with at least one half of the cylindrical outer surface of the circular stationary contact 12, the arc also tends to be extinguished due to the conduction of heat away therefrom. This conduction of heat away from the arc is further facilitated by the abutment of the rightmost surface of the arc runner 30 with the peripheral inner casing wall 53, the abutment of the sides of the arc runner with the insulating plates 45 and 47, and the abutment of the arc runner 30 with the upper peripheral inner casing wall 51.

Also, the stationary contact 12 is soldered to the terminal structure S, the latter extending through a hole 56 in the wall 53. The terminal 55 is insulated from the outer casing by a glass bushing 58 about which is a cylindrical metal sleeve 57 which is welded to the casing 10 to secure the thus formed terminal assembly thereto. As illustrated, a space 59 is thus formed into which the expanding hot gases created by the are may enter. Some of these gases also enter the small space between the insulator inner casing 11 and the outer casing 10 formed due to the sliding t relation between these parts. Since the grids 35 and 36 are also in sliding fit relation with the casing wall 51 and the insulator plates 45 and 47, these gases also escape by movement upwardly and t0 the left, FIGS. l and 3. Further, movement of the gases upwardly and to the left is facilitated by the movement upwardly of the arc.

The arc runner 30 and the grids 35 and 36 are substantially the same shape, size and thickness and are all made of iron, so that they retain little to no residual magnetism after arc extinction.V However, due to the smaller diameter of the movable contact 14, the inner opposed faces of the legs 41 are spaced apart and clear the movable contact 14 a minimum distance suflicient to permit its free passage therebetween, while as stated, the arc runner 30 is in intimate contact with the stationary contact 12.

When the contacts 12 and 14 are in the closed position (FIG. l) and the circuit breaker is connected to the circuit to be protected, a magnetic field is created in the magnetizable arc runner 30 at all times due to the current passing through the contacts 12 and 14. The strength of this magnetic field is directly proportional to the amount of current passing through the circuit breaker. Upon the occurrence of a heavy overcurrent, for instance, a short circuit, the strength of the magnetic eld will be greatly increased so that a field of high ux value and high potential exists when the contacts are opened by the collapse of the linkage 19 and the bias of the spring 17.

Both prior to contact separation and after contact separation, the magnetic lines of flux are normal to the arc which tends to form, and in the zone of the arc runner 3i), they flow through the high permeability material but must flow across the air gap between the ends of the legs 38, creating zones adjacent the arc, of different flux density. That is, as viewed in FIG. 4, upon contact separation and the creation of an arc a zone of high ux density is created below the part of the stationary contact 12 from which arcs tends to be drawn and generally across the air gap between the lower ends of the legs 38, whereas in the air zone above the stationary contact 12, as viewed in FIG. 4, a zone of low flux density is created due to the single concentrated mass of the base 39 above the stationary contact, and in the air zone of the legs 38 between these two flux zones a flux zone of intermediate flux density is created by the legs 38, since the legs are on opposite sides of the stationary contact 12 and each has a mass equal to or less than the mass of the base 39.

Due to the zones of different iiux density, the arc moves along the contacts 12 and 14 toward the bight 39 and, as the movable contact 14 separates further from the stationary contact 12, toward the bights 42 also. As the arc moves along the contacts 12 and 14 toward the bight 39 or the bights 39 and 42, the arc raises to a boiling point new spots first on the contacts and then on the runner and grids. This boiling absorbs a large amount of thermal energy of the arc in the form of latent heat of fusion and latent heat of vaporization. The movement of the boiling point distributes the erosion caused, thereby making the surface less irregular than would otherwise result, insuring that sufficient surface contact will be made when the contacts are reclosed.

This movement of the arc facilitates impingement of the arc upon the bights 39 and 42 and the breaking up of the arc into two smaller separate arcs. Movement upwardly of the arcs or arcs so formed continues until the arc or arcs are drawn from the position on the bights Where the ilux density is equal on all sides.

The aforementioned movement further tends to extinguish the arc because the movement of the arc into the large mass of the bights 39 and 42 moves the arc to a cooler region. When the arc moves upon the bight 39 and the bights 42, these large masses present a cooler surface to the arc (relative to the contacts 12 and 14) which also aids in its extinction.

To further facilitate the arc extinction, the grid 36 (farthest to the left) is disposed, as illustrated in FIG. 3, relative to the movable contact 14 so that when the movable contact 14 comes to rest in the contacts open position, the movable contact 14 is surrounded by the grid 36 in a manner similar to the manner in which the stationary contact 12 is straddled by the arc runner 30 except that there is no physical contact between the grid 36 and the movable Contact 14. Also, the grid 35 between the grid 36 and the arc runner' 31) is disposed approximately midway therebetween.

The arc runner 30 has parallel surfaces transverse to the path of movement of the movable contact 14 and a uniform thickness approximately that of the stationary contact 12, the vertical surfaces (FIG. l) of the arc runner 3i) and the stationary contact 12 all being parallel. However, the stationary Contact 12 is made slightly thicker than the arc runner 3ft, about .005 to .015 inch thicker, and the surface of the arc runner is initially disposed below the stationary contact face by this amount to that if the movable contact 12 should shift to one side or the other, while in service, the possibility of interfering engagement between the arc runner 30 and the movable contact 12, which would prevent proper abutment of the stationary and movable contact, is avoided. Also, this arrangement provides a margin for wear of the contacts. Likewise, the face of the movable contact 14 is initially, in the open position of the contacts, disposed somewhat to the right of the (rightrnost) surface of the grid 36.

As illustrated in FIG. 5, when the stationary contact 60 is square (or rectangular) the arc runner grid 61 is made to have an opening between its legs 62 to conform thereto so as to be in intimate contact with three sides of the stationary contact.

Also, the arc runner may be welded to the stationary contact for increasing arc extinction effectiveness and the stationary and movable contact members are formed from materials similar to coin silver or silver-cadmium oxide alloy while, as stated, the magnetizable arc runner is made of iron.

From the foregoing, it is seen that immediately upon initial separation of the contacts, the magnetic linx of the magnetizable arc runner creates zones of high and low flux density immediately adjacent to the stationary contact. These zones of varying iiux density cause the arc to move toward the bights and lengthen, to move into a zone of cooler neutral gases, to break into plural arcs between the bights, while at all times the large mass of the arc runner, particularly the bight, facilitates the transfer of heat by conduction away from the stationary contact and the arc.

Having .described the invention, I claim:

1. In a circuit breaker the combination of a case, stationary and movable contacts, a mechanism for moving said movable Contact away from said stationary contact, said contacts being the only electrically conductive elements from which arcs may be drawn on contact separation, and a magnetizable member completely surrounding the stationary contact on three sides thereof, said magnetizable member including a base and two legs in the form of a U-shape, said base having a mass, on the side of the stationary contact toward which movement of the are is desired, which is equal to or greater than but not dess than the mass of one of the legs, said legs being coterminous with the edge portion of said stationary contact farthest from said base and disposed on opposite sides of the stationary Contact, whereby the initial arc is immediately surrounded on contact separation by a zone of lowest fiux density at the base toward which the arc tends to move, a zone of highest flux density extending between the ends of the legs on the side opposite from that toward which the arc moves and with which the initial arc reacts to initiate movement thereof, and zones of intermediate iiux density between the aforesaid zones of high and low iiux density and on opposite sides of the arc to magnetically guide the arc toward said base, said case including a peripheral portion of electrical insulating material, said magnetizable member engaging said peripheral case portion and being in intimate physical Contact with a portion of the peripheral outer surface of said stationary contact, whereby extinction of the arc is further facilitated by conduction of heat from said arc through said stationary contact and magnetizable member directly to said peripheral case portion.

2. In a circuit breaker the combination of a case, stationary and movable contacts, a mechanism for moving said movable contact away from said stationary contact, said contacts being the only electrically conductive elements from which arcs may be drawn on Contact separation, and a magnetizable member completely surrounding the stationary contact on three sides thereof, said magnetizable member including a base and two legs in the form of a U-shape, said base having a mass, on the side of the stationary contact toward which movement of the are is desired, which is equal to or greater than but not less than the mass of one of the legs, said legs being coterminous with the edge portion of said stationary contact farthest from said base and disposed on opposite sides of the stationary contact, whereby the initial arc is irnmediately surrounded on contact separation by a zone of lowest flux density at the base toward which the arc tends to move, a zone of highest flux density extending between the ends of the legs on the side opposite from that toward which the arc moves and with which the initial are reacts to initiate movement thereof, and zones of intermediate flux density between the aforesaid zones of high and low flux density and on opposite sides of the are to magnetically guide the arc toward said base, the magnetizable member being disposed below the surface of the stationary contact so that if the movable contact shifts laterally during opening and closing movement of the contacts, interference between the magnetizable member and the movable contact is prevented.

References Cited in the le of this patent UNITED STATES PATENTS 2,116,791 Jackson May 10, 1938 2,360,922 Wilckens Oct. 24, 1944 2,467,937 Jackson Apr. 19, 1949 3,016,438 Heilman Ian. 9, 1962

Claims (1)

1. IN A CIRCUIT BREAKER THE COMBINATION OF A CASE, STATIONARY AND MOVABLE CONTACTS, A MECHANISM FOR MOVING SAID MOVABLE CONTACT AWAY FROM SAID STATIONARY CONTACT, SAID CONTACTS BEING THE ONLY ELECTRICALLY CONDUCTIVE ELEMENTS FROM WHICH ARCS MAY BE DRAWN ON CONTACT SEPARATION, AND A MAGNETIZABLE MEMBER COMPLETELY SURROUNDING THE STATIONARY CONTACT ON THREE SIDES THEREOF, SAID MAGNETIZABLE MEMBER INCLUDING A BASE AND TWO LEGS IN THE FORM OF A U-SHAPE, SAID BASE HAVING A MASS, ON THE SIDE OF THE STATIONARY CONTACT TOWARD WHICH MOVEMENT OF THE ARC IS DESIRED, WHICH IS EQUAL TO OR GREATER THAN BUT NOT LESS THAN THE MASS OF ONE OF THE LEGS, SAID LEGS BEING COTERMINOUS WITH THE EDGE PORTION OF SAID STATIONARY CONTACT FARTHEST FROM SAID BASE AND DISPOSED ON OPPOSITE SIDES OF THE STATIONARY CONTACT, WHEREBY THE INITIAL ARC IS IMMEDIATELY SURROUNDED ON CONTACT SEPARATION BY A ZONE OF LOWEST FLUX DENSITY AT THE BASE TOWARD WHICH THE ARC TENDS TO MOVE, A ZONE OF HIGHEST FLUX DENSITY EXTENDING BETWEEN THE ENDS OF THE LEGS ON THE SIDE OPPOSITE FROM THAT TOWARD WHICH THE ARC MOVES AND WITH WHICH THE INITIAL ARC REACTS TO INITATE MOVEMENT THEREOF, AND ZONES OF INTERMEDIATE FLUX DENSITY BETWEEN THE AFORESAID ZONES OF HIGH AND LOW FLUX DENSITY AND ON OPPOSITE SIDES OF THE ARC TO MAGNETICALLY GUIDE THE ARC TOWARD SAID BASE, SAID CASE INCLUDING A PERIPHERAL PORTION OF ELECTRICAL INSULATING MATERIAL, SAID MAGNETIZABLE MEMBER ENGAGING SAID PERIPHERAL CASE PORTION AND BEING IN INTIMATE PHYSICAL CONTACT WITH A PORTION OF THE PERIPHERAL OUTER SURFACE OF SAID STATIONARY CONTACT, WHEREBY EXTINCTION OF THE ARC IS FURTHER FACILITATED BY CONDUCTION OF HEAT FROM SAID ARC THROUGH SAID STATIONARY CONTACT AND MAGNETIZABLE MEMBER DIRECTLY TO SAID PERIPHERAL CASE PORTION.

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