VENT FOR ARC CHUTE
United States Patent 3803376
A circuit breaker having a spaced plate arc chute, with a V-shaped mouth region at the rear thereof, and separable arcing contacts positioned at this mouth region, is provided with venting control means stack positioned adjacent the front of the arc chute. The venting control means stack consists of a plurality of layers having screen sections and apertures, with the screen sections and apertures of different layers only partially overlapping to provide a tortuous path for arcing products emitted at the rear of the arc chute to rapidly deionize ionized portions of these arcing products.
US Patent References:
Circuit interrupter
Baker - February 1939 - 2147419
Arc chute for circuit breakers
Yarrick - March 1962 - 3025376
VENTING MEANS FOR CIRCUIT BREAKER ARC QUENCHER
Strobel - June 1971 - 3582966
Circuit interrupter
Baker - February 1939 - 2147419
Arc chute for circuit breakers
Yarrick - March 1962 - 3025376
VENTING MEANS FOR CIRCUIT BREAKER ARC QUENCHER
Strobel - June 1971 - 3582966
Application Number:
05/275521
Publication Date:
04/09/1974
Filing Date:
07/27/1972
View Patent Images:
Export Citation:
Assignee:
I-T-E Imperial Corporation (Philadelphia, PA)
Primary Class:
International Classes:
H01H9/34; H01H9/30; H01H33/08
Field of Search:
200/144R,147R,147B
Primary Examiner:
Macon, Robert S.
Attorney, Agent or Firm:
Ostrolenk, Faber, Gerb & Soffen
Claims:
1. A circuit breaker including fixed contact means; movable contact means positioned above said stationary contact means and operable into and out of engagement therewith; arc extinguishing arc chute means having a mouth region at the rear thereof; said movable and said stationary contact means being operatively positioned at said mouth region whereby electric current arcs drawn between said movable and said stationary contact means enter said arc chute; and labyrinth forming means, including a plurality of partially overlapping screen sections, positioned adjacent the front of said arc chute to deionize arcing products leaving said arc chute at the
2. A circuit breaker as set forth in claim 1 in which there is a forwardly deflectable insulating member adjacent the front of said arc chute at the bottom region thereof; said labyrinth means being at the top region of
3. A circuit breaker as set forth in claim 1 in which the labyrinth means includes a plurality of thin layers sandwiched together; a first and a second of said layers being spaced from one another, with each of said first and second layers including a first and a second of said screen sections; said first and second screen sections being laterally spaced.
4. A circuit breaker as set forth in claim 3 in which the first and second screen sections are spaced rectangles with the major axes of both screen sections of said first layer being parallel to each other and parallel to the major axes of both screen sections of said second layer and laterally
5. A circuit breaker as set forth in claim 4 in which each of the first and second layers includes an apertured section, with said first screen section being interposed between said second screen section and said aperture section; said aperture sections of said first and second layers overlapping the second screen sections of said second and first layers,
6. A circuit breaker as set forth in claim 5 in which each of said first and second layers includes a separator section interposed between said first and second screen sections; said separator sections of said first and second layers overlapping said first screen sections of said second
7. A circuit breaker as set forth in claim 6 in which there is a forwardly deflectable insulating member adjacent the front of said arc chute at the bottom region thereof; said labyrinth means being at the top region of
8. A circuit breaker as set forth in claim 6 in which a third of said layers is interposed between said first and second layers; said third layer having first and second rectangular windows having their major axes disposed at right angles to the major axes of said screen sections.
2. A circuit breaker as set forth in claim 1 in which there is a forwardly deflectable insulating member adjacent the front of said arc chute at the bottom region thereof; said labyrinth means being at the top region of
3. A circuit breaker as set forth in claim 1 in which the labyrinth means includes a plurality of thin layers sandwiched together; a first and a second of said layers being spaced from one another, with each of said first and second layers including a first and a second of said screen sections; said first and second screen sections being laterally spaced.
4. A circuit breaker as set forth in claim 3 in which the first and second screen sections are spaced rectangles with the major axes of both screen sections of said first layer being parallel to each other and parallel to the major axes of both screen sections of said second layer and laterally
5. A circuit breaker as set forth in claim 4 in which each of the first and second layers includes an apertured section, with said first screen section being interposed between said second screen section and said aperture section; said aperture sections of said first and second layers overlapping the second screen sections of said second and first layers,
6. A circuit breaker as set forth in claim 5 in which each of said first and second layers includes a separator section interposed between said first and second screen sections; said separator sections of said first and second layers overlapping said first screen sections of said second
7. A circuit breaker as set forth in claim 6 in which there is a forwardly deflectable insulating member adjacent the front of said arc chute at the bottom region thereof; said labyrinth means being at the top region of
8. A circuit breaker as set forth in claim 6 in which a third of said layers is interposed between said first and second layers; said third layer having first and second rectangular windows having their major axes disposed at right angles to the major axes of said screen sections.
Description:
This invention relates to molded case circuit breakers in general and more particularly relates to novel means for preventing electric current arcs from bypassing a spaced plate type arc chute.
In high cirrent capacity molded case circuit breakers, spaced plate type arc chutes are often provided to receive and facilitate extinction of arcs generated during current interruption. When large quantities of ionized gases are vented out of an arc chute, there is great danger that flashover will occur between adjacent poles at the tops of the arc chutes thereof. The prior art has attempted to prevent flashover between poles by providing screening to cool and deionize arcing products exhausted from the arc chute. This has proven adequate for moderately high current interruption.
However, for circuit breakers of extremely high continuous current ratings, say 2,000 amperes and more, the quantity, temperature, and degree of ionization of the arcing products exiting from the arc chute is so intense that it is not unusual for a conducting path to form from the top of the innermost arc plate to the prior art screen hereinbefore referred to, across the screen, and back to the movable arcing contact arm. In effect, this conducting path causes the arc chute to be bypassed or shorted so that the arc chute becomes ineffective.
The instant invention solves this last noted problem by providing a labyrinth of relatively small screen sections, insulated and staggered with respect to each other, and positioned along the arc chute bypass path previously described. This screen formed labyrinth arrangement appears to rapidly deionize those ionized arcing products exiting from the arc chute at high values of available current experienced by circuit breakers of very high continuous current rating, thereby preventing the arc chute from being bypassed by the arcs drawn during current interruption.
Accordingly, a primary object of the instant invention is to provide novel means by which to prevent arcing products from short-circuiting an entire arc chute or some plates thereof.
Another object is to provide means of this type including a labyrinth of relatively small screen sections, insulated and staggered with respect to each other, and positioned at the end of the arc chute remote from the separable contacts.
These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:
FIG. 1 is a longitudinal cross-section showing the mechanism for one pole of a multipole molded case circuit breaker.
FIG. 2 is a fragmentary plan view of the circuit breaker of FIG. 1, with a portion of the cover removed.
FIG. 3 is a bottom view of the circuit breaker cover at that portion of the circuit breaker illustrated in FIG. 2.
FIG. 4 is an exploded perspective of the labyrinth forming elements.
FIG. 5 is an exploded perspective of the arc chute and elements used to control arcing products as they exit from the arc chute.
Now referring to the figures. Multipole very high current capacity molded case circuit breaker 25 includes base 26 and cover 27 secured to one another in abutting relationship at interface 28. In a manner well known to the art, base 26 is provided with longitudinal partitions 31, 32 which cooperate with longitudinal partitions 33, 34 of cover 27 to provide three longitudinally extending compartments within circuit breaker housing 26, 27, with each of these compartments containing duplicates for most elements of the single pole shown in FIG. 1.
The current path for each pole of circuit breaker 25 extends from load terminal block 35 through flexible conductors 36, 37 to the respective sets of lower and upper movable contact arms 42, 43. Each of the contact arms 42 mounts an individual movable main contact 44 engageable with stationary main contact strip 52, and each of the arms 43 mounts an individual movable main main contact 45 engageable with stationary main contact strip 53. Main contact strips 52, 53 are mounted to the upper surface of line terminal block 55.
Arcing contact arm 39 mounts arcing contact 46 at the left end thereof, with the right end of arm 39 being connected through flexible conductors to load terminal 35. Movable arcing contact 46 is engageable with stationary arcing contact 54 mounted to the upper surface of line terminal 55 and spaced forward of stationary main contact strip 53. Operating mechanism 56 is used to move contacts 44-46 into and out of engagement with stationary contact 52-54, latch system 57 is used to maintain mechanism 56 in contact operating condition, and trip device 58 is used to automatically release latch system 57 upon the occurrence of predetermined overload conditions for automatic opening of circuit breaker 25.
Arc chute 60, having a plurality of spaced metal plates 61 disposed within the U-shaped configuration formed by the front and sides of insulating housing 62, is positioned forward of main stationary contact 53. Stationary arcing contact 54 is disposed in the mouth region formed by the V-notches in the rear edges of arc chute plates 61 and partially closed by insulating sheets 73. Magnetic arc runner 64 at the bottom of arc chute 60 is secured to the upper surface of line terminal 55 by a pair of screws 66, which extend through clearance apertures 67 in arc runner 64 and through another pair of clearance apertures 68 in one leg of angle 69. Relatively stiff, yet flexible, insulating sheet 71 is riveted to the other leg of angle 99. Upper edge 72 of sheet 71 extends to the region of interface 28 and is in close proximity to the apertured front surface of arc chute housing 62.
Labyrinth assembly 75, having three edges thereof secured within appropriate recesses of cover 27, is constructed of four insulating spacer layers 81-84 (see FIG. 4) and two screened layers 85, 86. Each of the spacer layers is of identical construction and includes a pair of rectangular windows 87, 88, having their major axes disposed vertically with respect to FIG. 4. Each of the screen layers 85, 86 is of identical construction and includes rectangular windows 91, 92 in an insulating frame. Screen segments 93, 94 are disposed within the respective windows 91, 92 and the major axes of windows 91, 92 are at right angles to the major axes of windows 87, 88. The major axes for windows 91, 92 of layer 85 are laterally offset from the major axes for windows 91, 92 of layer 86. Each of the layers 85, 86 also includes a pair of aligned elongated apertures 95, 96, extending parallel to the longitudinal axes of windows 91, 92, with window 92 being interposed between window 91 and apertures 95, 96. Apertures 95, 96 of layer 85 are positioned at one end of assembly 75, and apertures 95, 96 of layer 86 are disposed at the other end of assembly 75.
All of the windows 87 are in alignment as are all of the windows 88. Two spacer layers 82, 83 are interposed between screen layers 85, 86. Spacer layers 81 and 84 are positioned at the front and back of assembly 75 and act primarily to retain screened segments 93, 94. Screen segments 93, 94 and apertures 95, 96 of layers 85, 86 only partially overlap, so that arcing gases leaving arc chute housing 62 through apertures in the front thereof, after passing through one of the screen layers, are to a great extent forced to move at right angles to their original flow path in searching for paths through screen layer 86. The arcing gases forced to take the tortuous paths are substantially deionized and will not provide flashover paths at the front of arc chute 60.
For those features of construction in circuit breaker 25 that have not been described in detail herein, reference is made to one or more of the copending applications Ser. Nos. 275,568, 275,577, 275,446, 275,578, 275,507, 275,454, 275,508, 275,621, 275,623, 275,624, 275,569, 275,522, all filed of even date herewith, and all assigned to the assignee of the instant invention.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now become apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein but only by the appending claims.
In high cirrent capacity molded case circuit breakers, spaced plate type arc chutes are often provided to receive and facilitate extinction of arcs generated during current interruption. When large quantities of ionized gases are vented out of an arc chute, there is great danger that flashover will occur between adjacent poles at the tops of the arc chutes thereof. The prior art has attempted to prevent flashover between poles by providing screening to cool and deionize arcing products exhausted from the arc chute. This has proven adequate for moderately high current interruption.
However, for circuit breakers of extremely high continuous current ratings, say 2,000 amperes and more, the quantity, temperature, and degree of ionization of the arcing products exiting from the arc chute is so intense that it is not unusual for a conducting path to form from the top of the innermost arc plate to the prior art screen hereinbefore referred to, across the screen, and back to the movable arcing contact arm. In effect, this conducting path causes the arc chute to be bypassed or shorted so that the arc chute becomes ineffective.
The instant invention solves this last noted problem by providing a labyrinth of relatively small screen sections, insulated and staggered with respect to each other, and positioned along the arc chute bypass path previously described. This screen formed labyrinth arrangement appears to rapidly deionize those ionized arcing products exiting from the arc chute at high values of available current experienced by circuit breakers of very high continuous current rating, thereby preventing the arc chute from being bypassed by the arcs drawn during current interruption.
Accordingly, a primary object of the instant invention is to provide novel means by which to prevent arcing products from short-circuiting an entire arc chute or some plates thereof.
Another object is to provide means of this type including a labyrinth of relatively small screen sections, insulated and staggered with respect to each other, and positioned at the end of the arc chute remote from the separable contacts.
These objects as well as other objects of this invention will become readily apparent after reading the following description of the accompanying drawings in which:
FIG. 1 is a longitudinal cross-section showing the mechanism for one pole of a multipole molded case circuit breaker.
FIG. 2 is a fragmentary plan view of the circuit breaker of FIG. 1, with a portion of the cover removed.
FIG. 3 is a bottom view of the circuit breaker cover at that portion of the circuit breaker illustrated in FIG. 2.
FIG. 4 is an exploded perspective of the labyrinth forming elements.
FIG. 5 is an exploded perspective of the arc chute and elements used to control arcing products as they exit from the arc chute.
Now referring to the figures. Multipole very high current capacity molded case circuit breaker 25 includes base 26 and cover 27 secured to one another in abutting relationship at interface 28. In a manner well known to the art, base 26 is provided with longitudinal partitions 31, 32 which cooperate with longitudinal partitions 33, 34 of cover 27 to provide three longitudinally extending compartments within circuit breaker housing 26, 27, with each of these compartments containing duplicates for most elements of the single pole shown in FIG. 1.
The current path for each pole of circuit breaker 25 extends from load terminal block 35 through flexible conductors 36, 37 to the respective sets of lower and upper movable contact arms 42, 43. Each of the contact arms 42 mounts an individual movable main contact 44 engageable with stationary main contact strip 52, and each of the arms 43 mounts an individual movable main main contact 45 engageable with stationary main contact strip 53. Main contact strips 52, 53 are mounted to the upper surface of line terminal block 55.
Arcing contact arm 39 mounts arcing contact 46 at the left end thereof, with the right end of arm 39 being connected through flexible conductors to load terminal 35. Movable arcing contact 46 is engageable with stationary arcing contact 54 mounted to the upper surface of line terminal 55 and spaced forward of stationary main contact strip 53. Operating mechanism 56 is used to move contacts 44-46 into and out of engagement with stationary contact 52-54, latch system 57 is used to maintain mechanism 56 in contact operating condition, and trip device 58 is used to automatically release latch system 57 upon the occurrence of predetermined overload conditions for automatic opening of circuit breaker 25.
Arc chute 60, having a plurality of spaced metal plates 61 disposed within the U-shaped configuration formed by the front and sides of insulating housing 62, is positioned forward of main stationary contact 53. Stationary arcing contact 54 is disposed in the mouth region formed by the V-notches in the rear edges of arc chute plates 61 and partially closed by insulating sheets 73. Magnetic arc runner 64 at the bottom of arc chute 60 is secured to the upper surface of line terminal 55 by a pair of screws 66, which extend through clearance apertures 67 in arc runner 64 and through another pair of clearance apertures 68 in one leg of angle 69. Relatively stiff, yet flexible, insulating sheet 71 is riveted to the other leg of angle 99. Upper edge 72 of sheet 71 extends to the region of interface 28 and is in close proximity to the apertured front surface of arc chute housing 62.
Labyrinth assembly 75, having three edges thereof secured within appropriate recesses of cover 27, is constructed of four insulating spacer layers 81-84 (see FIG. 4) and two screened layers 85, 86. Each of the spacer layers is of identical construction and includes a pair of rectangular windows 87, 88, having their major axes disposed vertically with respect to FIG. 4. Each of the screen layers 85, 86 is of identical construction and includes rectangular windows 91, 92 in an insulating frame. Screen segments 93, 94 are disposed within the respective windows 91, 92 and the major axes of windows 91, 92 are at right angles to the major axes of windows 87, 88. The major axes for windows 91, 92 of layer 85 are laterally offset from the major axes for windows 91, 92 of layer 86. Each of the layers 85, 86 also includes a pair of aligned elongated apertures 95, 96, extending parallel to the longitudinal axes of windows 91, 92, with window 92 being interposed between window 91 and apertures 95, 96. Apertures 95, 96 of layer 85 are positioned at one end of assembly 75, and apertures 95, 96 of layer 86 are disposed at the other end of assembly 75.
All of the windows 87 are in alignment as are all of the windows 88. Two spacer layers 82, 83 are interposed between screen layers 85, 86. Spacer layers 81 and 84 are positioned at the front and back of assembly 75 and act primarily to retain screened segments 93, 94. Screen segments 93, 94 and apertures 95, 96 of layers 85, 86 only partially overlap, so that arcing gases leaving arc chute housing 62 through apertures in the front thereof, after passing through one of the screen layers, are to a great extent forced to move at right angles to their original flow path in searching for paths through screen layer 86. The arcing gases forced to take the tortuous paths are substantially deionized and will not provide flashover paths at the front of arc chute 60.
For those features of construction in circuit breaker 25 that have not been described in detail herein, reference is made to one or more of the copending applications Ser. Nos. 275,568, 275,577, 275,446, 275,578, 275,507, 275,454, 275,508, 275,621, 275,623, 275,624, 275,569, 275,522, all filed of even date herewith, and all assigned to the assignee of the instant invention.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now become apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein but only by the appending claims.