US3054876A - Magnetic assists for low current arcs - Google Patents

Description

Sept. 18, 1962 J. D. woon ETAL MAGNETIC AssTsTs FOR Low CURRENT ARcs 2 Sheets-Sheet 1 Filed Deo. 24, 1958 INVENTORS 2-Sheets-Sheet 2 J. D. WOOD ETAL MAGNETIC ASSISTS FOR LOW CURRENT ARCS Sept. 18, 1962 Filed Deo. 24, 19.58

United States Patent Otice 3,054,876 Patented Sept. 18, 1962 3,054,376 MAGNETIC ASSISTS FR LW CURRENT ARCS Joseph D. Wood, Wayne, Philip G. Smith, Hatboro, and

William A. Carter, Chester, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 24, 1958, Ser. No. 782,751 Claims. (Cl. 200-147) The instant invention relates to air magnetic circuit breakers and more particularly to magnetic assist means for arc interruption at low currents.

Air magnetic circuit breakers usually include an arc extinguishing means which operates in conjunction with magnetic blow-out means to eiiect a rapid interruption of the arc drawn between the parting contacts of the circuit breaker when the circuit breaker interrupts a current carrying circuit. The extremely low magnetic force produced by the magnetic means for movin's an arc of low current magnitude makes it necessary to provide an assist device to aid the arc extinguishing means in the interruption of low'current arcs.

Prior art devices have provided assists for the interruption of low current arcs which comprised a light blast of air directed to blow the arc into the arc chute, forming the arc extinguishing means, as the arc was formed when the breaker contacts parted. The light blast of air was usually supplied from a chamber and plunger assembly with either the plunger or chamber being actuated by some moving component of the breaker. IThe blast of air is created by the displacement of air in the chamber by the plunger.

This type of arrangement made it necessary to increase the amount of opening force in the operating mechanism of the breaker to compensate for the opposition from the displacement of air by `the plunger. Further, the air assist devices are operated each time the breaker operates, even when no current is being interrupted as well as to interrupt high current arcs, thereby resulting in unnecessary wear to the plunger and chambers well as tto associated parts.

t The device of the instant invention includes a specially designed magnetic circuit separate and distinct from the main magnetic blow-out means of the interrupter, and in addition thereto, to assist in the interruption of low current arcs. The coil of the magnetic assist is energized only by the arc after fthe arc is formed by the parting of the breaker contacts.

Means are provided whereby the magnetic assist coil is energized only during predetermined conditions of the arc. That is, the magnetic assist coil is by-passed when the arc current exceeds a predetermined value or after the arc has been driven into the arc chute a sufficient distance so that it is under the strong iniluence of the main magnetic circuit. The coil of the magnetic assists comprises a large number of turns to obtain the necessary flux to produce a strong magnetic held when only a low magnitude of current is flowing. Relatively small diameter Wire may be used in the assist coil since this coil will be required to carry current for only a short interval of time.

Accordingly, a primary object of the instant invention is to provide an air magnetic circuit breaker having novel means for low current arc interruption.

Another object is to provide a magnetic assist means, in

addition to the conventional magnetic blowout means, for the interruption of low current arcs.

Still another object is to provide assistance means for the interruption of low current arcs which does not require additional mechanical opening forces to be available in the breaker operating mechanism.

A fur-ther object is to provide an assist means for the interruption of low current arcs which is substantially nstantaneously by-passed when the circuit breaker interrupts high current arcs.

A still further object is to provide an assist means which is only operated during circuit breaker operation which results in the interruption of an arc.

Yet another object is to provide a longitudinally split arc runner construction for the insertion and withdrawal of the magnetic assist means.

These as well as other objects of the instant invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE l is a schematic illustrating a circuit interrupter including a novel magnetic assist means constructed in accordance with the instant invention.

FIGURE 2 is a schematic similar to FIGURE l illustrating a modiiication of the invention.

`FIGURE 3 is a schematic illustrating still another modification of this invention.

FIGURE 4 is a iront elevation of the longitudinally split arc runner of FIGURE 3 looking in the direction of arrows 44.

lNow referring more particularly to FIGURE 1, circuit breaker lil comprises a lower terminal stud 11 insulated and spaced from an upper terminal stud 12 whereon stationary main 13 and arcing 14 contacts are mounted. Conducting bridge y15 is pivotally secured and electrically connected to lower terminal 11 at pivot 16. Movable main 17 and arcing 18 contacts are mounted to bridge 15 and operatively positioned for engagement with stationary main 13 and arcing 14 contacts, respectively, when the circuit breaker is closed. Movable arcing contact 18 is pivotally secured to bridge 15 in a manner well known to the art which enables main contacts 13, 17 to part, upon opening of the circuit breaker, before the parting of arcing contacts 14, 18 and upon closing of the circuit breaker, zarcing contacts 14, 18 will engage before main contacts 13, 17 are brought into engagement.

Rear arc runner 2t) extends upwardly in the region above stationary contacts d3, 14 `while front runner 21 is spaced from rear runner 20 and extends upwardly from the position occupied by bridge 15I when circuit breaker 10 is open. Jump gap 22. is disposed between stationary arcing Contact 14 and the bottom of rear runner 20. A plurality of spaced parallel plates 23 forming arc chute 24 generally of the type described in U.S. Patent 2,390,735 are disposed between parallel portions of the rear 20 and front 21 runners.

A main blow-out structure comprising main blow-out coil 30 and main iron circuit 31 associated therewith is operatively positioned to urge arcs drawn between the parting contacts 14, 18 into the region of plates 23 thereby elongating the arcs so that they may be eiectively cooled, by plates 23, for the rapid extinguishing thereof. One end 33 of coil 30 is electrically connected to rear runner 20 while the other end 34 of coil 30 is electrically connected to upper terminal stud 12.

Circuit breaker 10 also includes a magnetic assist means comprising magnetic assist blow-out coil 40 and its associated iron circuit 41 positioned in the region of the contacts 14, 13, 17, 18. One end 42 of coil 40 is electrically connected to front runner 21 while the other end 43 is electrically connected to return connection 32 which electrically connects front runner 21 to lower terminal stud 11. Front runner 21, in the region shunted by magnetic assist blow-out `coil 40, includes a gap 44 for a purpose to be hereinafter explained.

Interruption of an arc by circuit breaker proceeds as follows: with the circuit breaker in the closed, position, that is, with movable contacts 17, 18 in engagement with stationary contacts 13, 14 lbridge 15 is moved clockwise about pivot 16 by any one of the operating mechanisms well known to the art. directly between the sta-tionary 14 and movable 18 arcing contacts and occupies the arc path A. As arcing contact 18 proceeds to the right, a portion of the arc is extinguished by jump gap 22 and the arc then assumes the path B between rear runner 20 and movable arcing contact 18 with the arc current owing through main blowout coil 30.

Continued movement of arcing Contact 18 to the right results in further elongation of the arc until it occupies the path C between the closest portions of the rear 20 and front 21 runners in the lower regions thereof and the path D between the front runner 21 and movable arcing contact 18. Further movement of movable arcing contact 18 to the right causes the portion of the arc at path D to be extinguished. At this time the current path between upper terminal 12 and lower terminal 11 comprises return connection 32 through assist blow-out coil 40, the arc along path C to rear runner 20 and through main blow-out coil 30. If `the arc current is of a relatively high magnitude the voltage between the ends 42, 43 of assist blow-out coil 40 will be sufficient to break down the air in gap 44 and the arc current of path C will bridge gap 44 so as to by-pass magnetic assist blow-out coil 40.

Thus, it is readily seen that with an arc current of relatively low current Ithe current through assist blow-out coil 40 will cause a ux to be generated in the magnetic assist iron circuit 41 which is operatively positioned to force the arc upwardly into `arc chute 24 where it may be efciently acted upon by the main iron circuit 31 by main blow-out coil 30. If the arc current is of a high magnitude it will flow through assist blow-out coil 40 for only a short time during which the potential across gap 44 will build up to a break down voltage at which time assist coil 40 will be shunted so ythat only main blow-out coil will be energized.

With this novel arrangement, magnetic assist coil may be comprised of many turns of tine wire so that the flux in the assist circuit 41 will be of a high magnitude even though the current is of a low magnitude. When the current through assist blow-out coil 40 exceeds a predetermined value the current is shunted through gap 44.

The invention as illustrated in FIGURE l comprises a device wherein the arc current is caused to by-pass the magnetic assist blow-out coil 40 when the arc current exceeds a predetermined value. The modification of the inveniton illustrated in FIGURE 2 is directed to a construction whereby the arc current by-passes the magnetic assist blow-out coil 40 when the arc has reached a predetermined position in `arc chute 24.

v Now referring more particularly to FIGURE 2, circuit breaker 100 comprises essentially the same elements as circuit breaker 10 of FIGURE l. For the sake of brevity and clarity, like reference numerals are utilized to identify identical elements in both iigures.

`Circuit breaker 100 includes a front arc runner 60 having an inwardly curved portion 61, the lower end of which is connected to end 42 of magnetic assist blow-out coil 40 while the other end 43 of magnetic assist blow-out Initially, `an arc is drawn A 4 coil 40 is lconnected to return connection 32. A gap 52, dened by edges 50 and 51, is formed in front runner 60 in the region above curved portion 61. A jumper 63 is connected to front runner 60 above gap edge 51 and extends to assist blow-out coil terminal 43.

When circuit breaker is utilized to interrupt a current carrying circuit magnetic assist blow-out coil 40 is energized at the moment the portion D of the are is extinguished. The ilux generated in the magnetic assist iron circuit 41 forces the are upwardly toward arc chute 24. When the arc is in the path designated E magnetic assist blow-out coil 40 is still energized. However, as the arc continues to travel upwardly the end thereof terminating at front runner 60 will pass from one side of gap 52 to the other side. With the arc in lthe position deiined by path F the arc current will ilow through jumper 63 thereby passing magnetic assist blow-out coil 40.

When circiut breaker 100 is called upon to interrupt a circuit carrying a high magnitude current, the arc will travel 4upwardly into chute 24 at a very rapid rate so that the arc current will only pass through the magnetic assist coil 40 -for an extremely short interval of time. This enables coil 40 -to be constructed of many turns of fine wire with the resistance of the wire providing a measure of self protection in that the current magnitude is limited by the resistance.

Still another embodiment of the instant invention is illustrated in FIGURES 3 and 4. Circuit breaker 200 comprises a lower 201 and an upper 202 terminal stud to which external circuit connections are made. Conductive bridging member 203, pivoted -to lower stud 201 at pivot 204, bridges the gap between current studs 201 and 202 when the circuit breaker is in the closed position illustrated in FIGURE 3.

Contact block 205 is mounted to the end of upper stud 202 and carries stationary main contact 206 and stationary auxiliary arcing contact 208. Stationary auxiliary arcing contact 208 is mounted to lthe foot of L-shaped member 236 whose arm is pivotally mounted at 237 to contact block 205. Torsion spring 235, interposed between member 236 and block 205, biases member 236 in a counterclockwise direction about pivot 237 for a reason to be hereinafter explained. These stationary contacts 206 and 208 are engageable by movable main contact 207 and movable auxiliary arcing contact 209, gaectively, both of which are secured directly to bridge Insulating member 212 which is positioned above contact block 205, and another contact block 213 is positioned above insulating member 212 with stationary arcing contact 214 being secured to conductor block 213. Movable arcing contact 215, which cooperates with stationary arcing contact 214, is mounted to conducting member 216 pivotally mounted at 217 to bridge 203 and is biased in a counterclockwise direction about pivot 217 by means of tension spring 233.

Rear arc runner 220 is a longitudinally split member comprising a first longitudinally extending conducting portion 221, on the right with respect to FIGURE 4, and a second longitudinally extending portion 222 with a longitudinally extending insulator 223 being interposed between conducting portions 221, 222. It is to be noted, that conducting portion 221 includes an offset portion exending below the lower end of conducting portion 222, with the insulator 223 having an offset portion 224 to insulate the lower end of portion 222 from portion 221.

One terminal 225 of main blow-out coil 226 is electrically connected to upper current stud 202. The other terminal 227 of main blow-out coil 226 is connected to one terminal 228 of magnetic assist coil 229 whose other terminal 230 is connected to conducting block 213 upon which stationary arcing contact 214 is mounted. Blowout coil terminals 227 and 228 are connected by jumper 248 to conducting portion 222 of rear runner 220. Conducting portion 221 of rear arc runner 220 is connected to conducting block 213. Y

Upper iron circuit 231 is associated with main blowout coil 226 and is energized thereby while lower iron circuit 232 is associated with assist blow-out coil 229 and is excited thereby. It is noted that although separate iron circuits 2 31, 232 have been illustrated for blow-out coils 226, 229, respectively, a single iron circuit excited by both coils 226 and 229 may be utilized.

The upper portion of front arc runner 233 is positioned in spaced parallel relationship with respect to rear arc runner 220 and the lower end of front arc runner 233 is connected by return jumper 234 to lower current stud 201. When bridge 203 is pivoted clockwise about pivot 204, from the circuit breaker closed position of FIGURE 3, to bring circuit breaker 200 to the open circuit position, main contacts 206, 207 are lirst to part since spring 235 urges conducting element 208 to the right with respect to FIGURE 3. Continued clockwise movement of bridge 203 brings about the disengagement of auxiliary arcing contacts 208, 209.

Since the current path through auxiliary arcing contacts 208, 209 has now been broken, the current selects a parallel path through arcing contacts 214, 215. This parallel path comprises main blowout coil 226 and assist blow-out coil 229 in electrical series. The current through the two blow-out coils 226, 229 produces a voltage drop which appears across auxiliary arcing contacts 208, 209. This voltage attempts to maintain an arc at contacts 208, 209 but this arc impinges on the insulating member 212 thereby extinguishing this arc.

Arcing contacts 214, 215 then part forming an arc which is free to move up the right hand portion 221 of rear arc runner 220. At this time, the voltage drop across the magnetic assist blow-out coil 229 is across longitudinal extending insulating member 223. At low values of current, there is a low voltage drop between the portions 221, 222 of arc runner 220 so low that the arc remains on the right hand portion 221 and is driven far into arc chute 250 due to the high iield produced by magnetic assist blow-out coil 229 which comprises many turns. At high values of current, a high voltage drop is developed between portions 221, 222 of arc runner 220 so that the arc jumps the insulating barrier 223 thereby deenergizing the magnetic assist blow-out coil 229.

The arc is still driven upwardly in the chute 250 due to the magnetic iield produced by the main blow-out coil 226 since a high current is flowing through this coil 226, even though this coil 226 is comprised of a fewer number of turns than assist coil 229. The transfer of the arc to the left hand portion 222 of arc runner 220 prevents magnetic assist blow-out coil 229 from being destroyed by excessive heating and/ or mechanical forces.

Thus, we have provided a circuit breaker including novel magnetic means for assisting in the interruption of low current arc. The magnetic means does not include any movable parts which will wear out after repeated operations of the breaker. Further, the magnetic means does not require additional mechanical opening forces to be provided for the circuit breaker.

Although we have here described preferred embodiment of our novel invention, many variations and modiiications will now be apparent to those skilled in the art, and we therefore prefer to be limited, not by the specific disclosure herein, but only by the appending claims.

We claim:

1. A circuit breaker including a pair of cooperating contacts, an arc chute operatively positioned to receive an electric current arc drawn between said contacts upon parting thereof, rst means associated with said arc chute energizable by said arc for urging said arc deeply into said arc chute, and second means energizable by said arc; said second means being operatively positioned in the region of said contacts and being constructed to urge an arc of low current magnitude toward said first means;

said rst and second means being isolated from said cooperating contacts when said contacts are in an engaged position; a rear runner at one side of said arc chute and a front runner at the other side; one of said contacts being movable and the other of said contacts being stationary; said rear runner being positioned in the region of said stationary contact; said movable contact being movable from a rst position in engagement with said stationary contact, toward said front runner to a second position wherein said contacts are disengaged; said front runner including a gap therein; said second means comprising a second coil connected in electrical parallel with said gap; said gap being constructed to be arced over when current through said second coil exceeds a predetermined value thereby by-passing said current around said second coil through said gap to prevent damage to said second coil.

2. A circuit breaker including a pair of cooperating contacts, an arc chute operatively positioned to receive an electric current arc drawn between said contacts upon parting thereof, iirst means associated with said arc chute energizeable by said arc for urging said arc deeply into said arc chute, `and second means energizeable by said are; said second means being operatively positioned in the region of said contacts and being constructed to urge an arc of low current magnitude toward said rst means; said iirst and second means being isolated from said cooperating contacts when said contacts are in an engaged position; a rear runner at one side of said arc chute and a front runner at the other side; one of said contacts being movable and the other of said contacts being stationary; said rear runner being positioned in the region of said stationary contact; said movable contact being movable from a iirst position, in engagement with said stationary y contact, toward said front runner at a second position wherein said contacts are disengaged; said front runner including a gap therein; said second means comprising a second coil connected between said gap and said movable contacts; current conducting means connected in electrical parallel across a series combination including said gap and said second coil; said gap being operatively positioned to cause arc current heretofore owing through said second coil to be shunted through said current conducting means when said arc has reached a predetermined position in said arc chute thereby preventing damage to said second coil.

3. A circuit breaker comprising cooperating contact means, an arc chute operatively positioned to receive an electric current arc drawn between a iirst set of contacts, of said contact means, upon parting thereof, tirst means associated with said arc chute energizable by said arc for urging said arc deeply into said arc chute, second means also energizable by said arc; Said first and second means being isolated from said cooperating contacts when said contacts are in an engaged position; said second means being constructed to urge an arc of low current magnitude into said arc chute; said second means being yautomatically deenergized `when said arc attains a predetermined characteristic; said arc chute including a longitudinally split arc runner; said arc runner including a iirst and a second longitudinally extending conducting portion, an insulating means interposed between said first and said second conducting portion; said insulating means and said conducting portions being operatively connected to said tirst and said `second means to cause deenergization of said second means when said arc is of said predetermined characteristic.

4. A circuit breaker `comprising cooperating contact means, an arc chute operatively positioned to receive an electric current arc drawn between a itirst set of contacts, of said contact means, upon parting thereof, iirst means associated with said arc chute energizable by `said arc for urging said arc deeply into said arc chute, second means also energizable by said arc; said rst and second means being isolated from said cooperating contacts when said contacts are in an engaged position; said second means being constructed to urge an arc of low current magnitude into said arc chute; said `second means being automatically deenergized when said arc attains a predetermined characteristic; said arc chute includingT a longitudinally split arc runner; said arc runner including a first and a second longitudinally extending conducting portion, an insulating means interposed between said first and said second conducting portion; said insulating means and said conducting portions being operatively connected to said first and said second means to cause deenergization of said second means when said arc is of said predetermined characteristic; said first conducting portion being longer than said second conducting portion; said first portion including at a first end thereof an offset portion positioned opposite a first end of said second portion.

5. A circuit breaker comprising cooperating contact means, an arc chute operatively positioned to receive an electric current arc drawn between a first set of contacts, of said contact means, upon parting thereof, first means associated with said arc chute energizable by said arc for urging said arc deeply into said arc chute, second means also energizable by said are; said first and second means being isolated from said cooperating contacts when said contacts are in an engaged position; said second means being constructed to urge an arc of low current magnitude into said arc chute; said second means being automatically deenergized when said arc attains a predetermined characteristic; said arc chute including a longitudinally split arc runner; said arc runner including a first and a second longitudinally extending conducting portion, an insulating means interposed between said first and said second conducting portion; said insulating means and said conducting portions being operatively connected to said first and said second means to cause deenergization of said second means when said arc is of said predetermined characteristic; said first means comprising a first coil and said second means comprising a second coil; said contact means comprising a first and a second pair of cooperating contacts, with each of said pairs of contacts including a stationary contact; another insulating means interposed between said stationary contacts; said second coil being electrically connected between said first and said second arc runner portions with said first portion also being electrically connected to said stationary contact of said first pair of cooperating contacts; said first coil being electrically connected between said second arc runner portion and said stationary contact of said second pair of cooperating contacts.

6. A circuit breaker comprising cooperating contact means, an arc chute operatively positioned to receive an electric current arc drawn between a first set of contacts, of said contact means, upon parting thereof, first means associated with said arc chute energizable by said arc for urging said arc deeply into said arc chute, second means also energizable by said arc; said first and second means being isolated from said cooperating contacts when said contacts are in an engaged position; said second means being constructed to urge an arc of low current magnitude into said arc chute; said second means being automatically deenergized when said arc attains a predetermined characteristic; said arc chute including a longitudinally split arc runner; said arc runner including a first and a second longitudinally extending conducting portion, an insulating means interposed between said first and said second conducting portion; said insulating means and said conducting portions being operatively connected to said first and said second means to cause deenergization of said second means when said arc is of said predetermined characteristic; said first means comprising a first coil and said second means comprising a second coil; said contact means comprising a first and a second pair of cooperating contacts, with each of said pairs of contacts including a stationary contact; another insulating means interposed between said stationary contacts; said second coil being electrically connected between said first and said second arc runner portions with said first portion also being electrically connected to said stationary contact of said first pair of cooperating contacts; said first coil being electrically connected between said second arc runner portion and `said stationary Contact of said second pair of cooperating contacts; said first pair of cooperating contacts being constructed to open after the opening of said second pair of cooperating contacts upon operation of .said circuit breaker from its closed to its open position; said second coil being comprised of a greater number of turns than said first coil.

7. In combination, a pair of cooperating contacts, an are chute having a pair of arc runners operatively positioned to receive an arc drawn between said contacts upon separation thereof, main blowout means housed in said arc chute for urging said arc into said arc chute, auxiliary blowout means positioned in the region of said cooperating contacts for urging said arc in the direction of said main blowout means, one of said arc runners having a gap, said auxiliary blowout means being connected across said gap for developing a voltage drop across said gap during circuit interruption whereby the voltage drop urges the arc to jump said gap.

8. in combination, first and second cooperating contacts, an arc chute operatively positioned to receive an are drawn between said contacts upon separation thereof, main blowout means housed in said arc chute, auxiliary blowout means positioned in proximity to said contacts for urging said are in the direction of said main blowout means, a pair of arc runners housed in `said arc chute, one of said runners having a spark gap which splits said arc runner into an upper and lower portion, said auxiliary blowout means being connected between said first contact and the upper portion of said split arc runner, the lower portion of said split arc runner being connected to said first contact whereby the voltage developed by said auxiliary blowout means during circuit interruption causes the spark gap to draw an arc between the halves of said split arc runner causing the lower half of said split arc runner to by-pass said auxiliary blowout means.

9. A pair of cooperating contacts, an arc chute operatively positioned to receive an arc drawn between said contacts upon separation thereof, said are chute including a front and a rear arc runner and first and second blowout means, said first blowout means being connected to said front arc runner for urging said arc deeply into said arc chute when said arc is transferred from said cooperating contacts to said arc runners, said second blowout means positioned in the immediate area of said cooperating contacts and connected to said front arc runner for urging said arc in the direction of said first blowout means when said arc is drawn between said arc runners, said front arc runner having a gap for deenergizing said second blowout means when the current drawn by said second blowout means attains a predetermined magnitude, said first and second blowout means being isolated from said contacts when said contacts are in an engaged position.

l0. A pair of cooperating contacts, an arc chute operatively positioned to receive an arc drawn between said contacts upon separation thereof, said arc chute including a front and a rear arc runner `and first and second blowout means, said first blowout means being connected to said front are runner for urging said arc deeply into said arc chute when said arc is transferred from said cooperating contacts to said arc runners, said second blowout means .positioned in the immediate area of said cooperating contacts and connected to said rear arc runner for urging said arc in the direction of said first blowout means when said arc is drawn between said arc runners, said rear arc runner having a gap for deenergizing said second blowout means when the current drawn by `said second blowout means attains a predetermined magnitude, said first and second blowout means being isolated from said contacts when said contacts are in an engaged position.

References Cited in the file of this patent UNITED STATES PATENTS 410 Zajc May 29, 1951 Thommen Feb. 4, 1958 Fust Dec. 22, 1959 FOREIGN PATENTS Great Britain Ma)r 22, 1924 France Nov. 28, 1938 Germany Nov. 6, 1958

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