SINGLE DIRECT CURRENT ARC CHUTE, AND
BI-DIRECTIONAL DIRECT CURRENT ELECTRICAL
SWITCHING APPARATUS EMPLOYING THE SAME
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority from and claims the benefit of U.S.
Patent Application Serial No. 13/603,574, filed September 5, 2012, which is
incorporated by reference herein.
BACKGROUND
Field
The disclosed concept pertains generally to electrical switching
apparatus and, more particularly, to direct current electrical switching apparatus, such
as, for example and without limitation, direct current circuit breakers. The disclosed
concept further pertains to direct current arc chutes.
Background Information
Electrical switching apparatus employing separable contacts exposed
to air can be structured to open a power circuit carrying appreciable current. These
electrical switching apparatus, such as, for instance, circuit breakers, typically
experience arcing as the contacts separate and commonly incorporate arc chutes to
help extinguish the arc. Such arc chutes typically comprise a plurality of electrically
conductive plates held in spaced relation around the separable contacts by an
electrically insulative housing. The arc transfers to the arc plates where it is stretched
and cooled until extinguished.
Typically, molded case circuit breakers (MCCBs) are not specifically
designed for use in direct current (DC) applications. When known alternating current
(AC) MCCBs are sought to be applied in DC applications, multiple poles are
electrically connected in series to achieve the required interruption or switching
performance based upon the desired system DC voltage and system DC current.
One of the challenges in DC interruption is to drive the arc into the arc
chute, specifically at relatively low current levels. Some known DC switching
products use permanent magnets to drive the arc into the arc splitter plates. However,
they either provide only uni-directional current interruption, or they are relatively
large due to the use of two arc chutes in order to achieve bi-directional performance.
There is room for improvement in direct current electrical switching
apparatus.
There is also room for improvement in direct current arc chutes.
SUMMARY
These needs and others are met by embodiments of the disclosed
concept.
In accordance with one aspect of the disclosed concept, a direct current
arc chute comprises: a ferromagnetic base having a first end and an opposite second
end; a first ferromagnetic side member disposed from the first end of the
ferromagnetic base; a second ferromagnetic side member disposed from the opposite
second end of the ferromagnetic base; a third ferromagnetic member disposed from
the ferromagnetic base intermediate the first and second ferromagnetic side members,
the third ferromagnetic member having an end portion opposite the ferromagnetic
base; a first permanent magnet disposed on the first ferromagnetic side member, the
first permanent magnet having a first magnetic polarity facing the third ferromagnetic
member; a second permanent magnet disposed on the second ferromagnetic side
member, the second permanent magnet having the first magnetic polarity facing the
third ferromagnetic member; a first arc chamber disposed between the first
ferromagnetic side member and the third ferromagnetic member, the first arc chamber
comprising a plurality of arc splitter plates; and a second arc chamber disposed
between the second ferromagnetic side member and the third ferromagnetic member,
the second arc chamber comprising a plurality of arc splitter plates, wherein the first
permanent magnet and the first ferromagnetic side member extend away from the first
end of the ferromagnetic base and beyond the end portion of the third ferromagnetic
member, wherein the second permanent magnet and the second ferromagnetic side
member extend away from the opposite second end of the ferromagnetic base and
beyond the end portion of the third ferromagnetic member, wherein the first
permanent magnet and the first ferromagnetic side member extend toward the second
permanent magnet and the second ferromagnetic side member after the end portion of
the third ferromagnetic member, and wherein the second permanent magnet and the
second ferromagnetic side member extend toward the first permanent magnet and the
first ferromagnetic side member after the end portion of the third ferromagnetic
member.
As another aspect of the disclosed concept, a bi-directional, direct
current electrical switching apparatus comprises: separable contacts; an operating
mechanism structured to open and close the separable contacts; and a single direct
current arc chute comprising: a ferromagnetic base having a first end and an opposite
second end, a first ferromagnetic side member disposed from the first end of the
ferromagnetic base, a second ferromagnetic side member disposed from the opposite
second end of the ferromagnetic base, a third ferromagnetic member disposed from
the ferromagnetic base intermediate the first and second ferromagnetic side members,
the third ferromagnetic member having an end portion opposite the ferromagnetic
base, a first permanent magnet disposed on the first ferromagnetic side member, the
first permanent magnet having a first magnetic polarity facing the third ferromagnetic
member, a second permanent magnet disposed on the second ferromagnetic side
member, the second permanent magnet having the first magnetic polarity facing the
third ferromagnetic member, a first arc chamber disposed between the first
ferromagnetic side member and the third ferromagnetic member, the first arc chamber
comprising a plurality of arc splitter plates, and a second arc chamber disposed
between the second ferromagnetic side member and the third ferromagnetic member,
the second arc chamber comprising a plurality of arc splitter plates, wherein the first
permanent magnet and the first ferromagnetic side member extend away from the first
end of the ferromagnetic base and beyond the end portion of the third ferromagnetic
member, wherein the second permanent magnet and the second ferromagnetic side
member extend away from the opposite second end of the ferromagnetic base and
beyond the end portion of the third ferromagnetic member, wherein the first
permanent magnet and the first ferromagnetic side member extend toward the second
permanent magnet and the second ferromagnetic side member after the end portion of
the third ferromagnetic member, and wherein the second permanent magnet and the
second ferromagnetic side member extend toward the first permanent magnet and the
first ferromagnetic side member after the end portion of the third ferromagnetic
member.
As another aspect of the disclosed concept, a bi-directional, direct
current electrical switching apparatus comprises: separable contacts comprising a
movable contact and a fixed contact; an operating mechanism structured to open and
close the separable contacts, the operating mechanism comprising a movable contact
arm carrying the movable contact; and a single direct current arc chute comprising: a
ferromagnetic base having a first end and an opposite second end, a first
ferromagnetic side member disposed from the first end of the ferromagnetic base, a
second ferromagnetic side member disposed from the opposite second end of the
ferromagnetic base, a third ferromagnetic member disposed from the ferromagnetic
base intermediate the first and second ferromagnetic side members, the third
ferromagnetic member having an end portion opposite the ferromagnetic base, a first
permanent magnet disposed on the first ferromagnetic side member, the first
permanent magnet having a first magnetic polarity facing the third ferromagnetic
member, a second permanent magnet disposed on the second ferromagnetic side
member, the second permanent magnet having the first magnetic polarity facing the
third ferromagnetic member, a first arc chamber disposed between the first
ferromagnetic side member and the third ferromagnetic member, the first arc chamber
comprising a plurality of arc splitter plates, a second arc chamber disposed between
the second ferromagnetic side member and the third ferromagnetic member, the
second arc chamber comprising a plurality of arc splitter plates, a first contoured
gassing wall disposed adjacent the first permanent magnet, and a second contoured
gassing wall disposed adjacent the second permanent magnet, wherein the first
permanent magnet and the first ferromagnetic side member extend away from the first
end of the ferromagnetic base and beyond the end portion of the third ferromagnetic
member, wherein the second permanent magnet and the second ferromagnetic side
member extend away from the opposite second end of the ferromagnetic base and
beyond the end portion of the third ferromagnetic member, wherein the movable
contact carried by the movable contact arm traces a path of motion between a closed
position of the separable contacts and an open position of the separable contacts, and
wherein the path of motion is disposed between the end portion of the third
ferromagnetic member and the first and second contoured gassing walls.
BRIEF DESCRIPTION OF THE DRAWINGS
A full understanding of the disclosed concept can be gained from the
following description of the preferred embodiments wi en read in conjunction with the
accompanying drawings in which:
Figure 1 is an isometric view of a steel and permanent magnet structure
including two permanent magnets for a single arc chute.
Figure 2 is a simplified top plan view of the steel and permanent magnet
structure of Figure 1 and also including a movable contact arm and separable contacts in
an open position.
Figure 3 is an isometric view of a bi-directional arc chute including a
steel and permanent magnet structure having two permanent magnets in accordance with
embodiments of the disclosed concept.
Figure 4 is an isometric view of one-half of the bi-directional arc chute of
Figure 3.
Figures 5 and 6 are end vertical elevation isometric views of the b i
directional arc chute of Figure 3.
Figure 7 is a top plan view of the bi-directional arc chute of Figure 3.
Figure 8 is an isometric view of an electrical switching apparatus with
some parts cut away to show internal structures in an open position in accordance with
embodiments of the disclosed concept.
Figure 9 is an isometric view of an electrical switching apparatus with
some parts cut away to show internal su ctures in an open position in accordance with
other embodiments of the disclosed concept.
Figure 0 is an isometric view of one of the gassing inserts of Figure 9.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As employed herein, the term "number" shall mean one or an integer
greater than one (i.e., a plurality).
As employed herein, the statement that two or more parts are
"connected" or "coupled" together shall mean that the parts are joined together either
directly or joined through one or more intermediate parts. Further, as employed
herein, the statement that two or more parts are "attached" shall mean that the parts
are joined together directly.
The disclosed concept is described in association with direct current
circuit breakers, although the disclosed concept is applicable to a wide range of direct
current electrical switching apparatus.
Referring to Figures 1 and 2, a steel and permanent magnet structure 2
includes two permanent magnets 4,6 for a single direct current arc chute 8. The
permanent magnets 4,6 are shown just inside of the two vertical legs 10,12 of a steel
structure 14, and are between the steel structure 14 and an insulative housing (not
shown). The single direct current arc chute 8 includes a ferromagnetic base 18 having
a first end 20 and an opposite second end 22. A first ferromagnetic side member 24 is
disposed from the first end 20, a second ferromagnetic side member 26 is disposed
from the opposite second end 22, and a third ferromagnetic member 28 is disposed
from the ferromagnetic base intermediate the first and second ferromagnetic side
members 24,26. The first permanent magnet 4 has a first magnetic polarity (S), is
disposed on the first ferromagnetic side member 24 and faces the third ferromagnetic
member 28. The second permanent magnet 6 has the first magnetic polarity (S), is
disposed on the second ferromagnetic side member 26 and faces the third
ferromagnetic member 28.
The first end 20 of the ferromagnetic base 18 and the first
ferromagnetic side member 24 disposed from the first end 20 define a first corner 30,
and the opposite second end 22 of the ferromagnetic base 18 and the second
ferromagnetic side member 26 disposed from the opposite second end 22 define a
second corner 32. The single direct current arc chute 8 defines a magnetic field
pattern 34. A movable contact arm 38 carries a movable contact 40, which
electrically engages a fixed contact 42 carried by a stationary conductor 44.
Whenever an arc (not shown) is struck between the movable contact 40 and the fixed
contact 42, which are disposed between the first and second ferromagnetic side
members 24,26, the magnetic field pattern 34 is structured to drive the arc toward one
of the first and second corners 30,32 depending on a direction of current flowing in
the arc. For example, for current flowing from the movable contact 40 to the fixed
contact 42, the arc is driven toward the corner 30 along path 45. Conversely, for
current flowing from the fixed contact 42 to the movable contact 40, the arc is driven
toward the corner 32 along path 46.
Unlike Figures 1 and 2, the disclosed concept employs an angled
permanent magnet side wall as shown in Figures 3-7, which is structured to improve
the orientation of the magnetic field. This, in turn, drives an arc into arc splitter plates
222,226. The improved magnetic field orientation forces a magnetic field null point
244 and field reversal away from the two arc chambers 220,224 of the arc chute 200,
and increases the magnitude of the magnetic field near the separable contacts 238.
The direction of the magnetic field beyond the end of the third ferromagnetic member
212 (between the member 212 and the separable contacts 238) pulls the arc to the first
arc chamber 220 or to the second arc chamber 224, depending on the polarity of the
electric current. The arc chute 200 employs a permanent magnet arrangement and a
single-break contact structure to achieve bi-directional DC switching and interruption
capability, including relatively low current levels.
In Figures 1 and 2, the magnetic field null point 48 and field reversal
are much closer to the separable contacts 42,44 and the arc splitter plates (not shown).
During instances when the arc column size is too large at relatively high current
levels, the arc could cross the null point 48 and enter the reversed field, which pushes
the arc away from the arc splitter plates.
Figure 3 shows the bi-directional direct current arc chute 200. The
direct current arc chute 200 includes a ferromagnetic base 202 having a first end 204
and an opposite second end 206, a first ferromagnetic side member 208 disposed from
the first end 204, a second ferromagnetic side member 210 disposed from the opposite
second end 206, and the third ferromagnetic member 212 disposed from the
ferromagnetic base 202 intermediate the first and second ferromagnetic side members
208,210. The third ferromagnetic member 212 has an end portion 214 opposite the
ferromagnetic base 202. A first permanent magnet 216 is disposed on the first
ferromagnetic side member 208 and has a first magnetic polarity (S) facing the third
ferromagnetic member 212. A second permanent magnet 218 is disposed on the
second ferromagnetic side member 210 and has the first magnetic polarity (S) facing
the third ferromagnetic member 212. The first arc chamber 220 is disposed between
the first ferromagnetic side member 208 and the third ferromagnetic member 212.
The first arc chamber 220 includes the plurality of arc splitter plates 222. The second
arc chamber 224 is disposed between the second ferromagnetic side member 210 and
the third ferromagnetic member 212. The second arc chamber 224 includes the
plurality of arc splitter plates 226. The first permanent magnet 216 and the first
ferromagnetic side member 208 extend away from the first end 204 of the
ferromagnetic base 202 and beyond the end portion 214 of the third ferromagnetic
member 212. The second permanent magnet 2 18 and the second ferromagnetic side
member 210 extend away from the opposite second end 206 of the ferromagnetic base
202 and beyond the end portion 214 of the third ferromagnetic member 212. The first
permanent magnet 216 and the first ferromagnetic side member 208 extend toward the
second permanent magnet 218 and the second ferromagnetic side member 210 after
the end portion 214 of the third ferromagnetic member 212. The second permanent
magnet 218 and the second ferromagnetic side member 210 extend toward the first
permanent magnet 216 and the first ferromagnetic side member 208 after the end
portion 214 of the third ferromagnetic member 212.
The arc chute 200 of Figure 3 employs extended and angled
ferromagnetic side members 208,210 and permanent magnets 216,218 along both
sides 228,230, respectively, of the arc chute 200, which provides a dual arc chamber
structure 220,224 with a ferromagnetic center barrier formed by the third
ferromagnetic member 212.
The angled permanent magnet and ferromagnetic side member side
wall structure of the arc chute 200 improves the orientation of the magnetic field
which drives the arc into one of the dual arc chambers 220,224 (depending on the
current direction) and splits the arc. As shown in Figures 3-7, the bottoms of the
example V-shapes 232,234 of the angled permanent magnet and ferromagnetic side
member side wall structures point toward each other.
As contrasted with the magnetic field pattern 34 of Figure 2, in which
the magnetic field null point 48 and field reversal are relatively close to the movable
contact 40 and the fixed contact 42, for the structure of the arc chute 200 of Figures 3-
7, the magnetic field null point 244 and field reversal are moved relatively far to the
right (with respect to Figure 7) of separable contacts 238 (shown in Figure 8), and the
magnitude of the magnetic field is increased near the separable contacts 238. As
shown in Figure 2, the magnetic field at the magnetic field null point 48 is zero.
Moving the magnetic field null point away from the separable contacts 238 results in
a relatively larger magnetic field at the location of the separable contacts 238.
The advantage of this movement of the magnetic field null point and
the line of magnetic field reversal is as follows. An arc forms between the separable
contacts 238 (shown in Figure 8) when they initially part. It is desired to move the arc
to the right or to the left (with respect to Figures 5 and 6) and into the respective right
or left (with respect to Figures 5 and 6) splitter plates 226,222, depending on the
direction of current flow in the arc. If the magnetic field is relatively large, then the
arc will more quickly (and more reliably) move off of the separable contacts 238 and
into the arc splitter plates 222,226 and be extinguished (in order to interrupt the
current). When the arc can be extinguished and interrupt the current relatively more
quickly, then there is less damage to the separable contacts 238 and the arc splitter
plates 222,226 per interruption, and the life of a corresponding electrical switching
apparatus, such as circuit breaker 240 (Figure 8), is extended.
Example 1
The following factors can increase the magnitude of the magnetic field
near the fixed contact 242 (shown in Figure 8): (1) increasing the thickness of the
permanent magnets 216,218; (2) increasing the strength of the material of the
permanent magnets 216,218, although relatively stronger magnetic materials are
generally susceptible to demagnetization at relatively lower temperatures; (3)
decreasing the distance between the separable contacts 238 (shown in Figure 8) and
the intermediate ferromagnetic (e.g., without limitation, steel) member 212; and (4)
increasing the distance between the separable contacts 238 and the magnetic field null
point 244 (shown in Figure 7).
Example 2
The first permanent magnet 216 and the first ferromagnetic side
member 208 are parallel with the second permanent magnet 218 and the second
ferromagnetic side member 210 between the first end 204 of the ferromagnetic base
202 and the end portion 214 of the third ferromagnetic member 212. The second
permanent magnet 218 and the second ferromagnetic side member 210 are parallel
with the first permanent magnet 216 and the first ferromagnetic side member 208
between the opposite second end 206 of the ferromagnetic base 202 and the end
portion 214 of the third ferromagnetic member 212.
Example 3
The first permanent magnet 216 and the first ferromagnetic side
member 208 both angle toward the second permanent magnet 218 and the second
ferromagnetic side member 210 after the end portion 214 of the third ferromagnetic
member 212. The second permanent magnet 2 and the second ferromagnetic side
member 210 both angle toward the first permanent magnet 216 and the first
ferromagnetic side member 208 after the end portion 214 of the third ferromagnetic
member 212. This allows the magnetic field to pull the arc toward the desired arc
splitter plates 222 or 226 regardless of the initial arc motion direction. The direction
of the magnetic field beyond the end portion 214 of the third ferromagnetic member
212 (between the member 212 and the separable contacts 238 (Figure 8)) pulls the arc
to the first arc chute 220 or to the second arc chute 224, depending on the polarity of
the electric current.
Example 4
The permanent magnets 216,218, ferromagnetic side members
208,210, and ferromagnetic center barrier formed by ferromagnetic member 212 are
preferably covered with electrical insulation (not shown) to prevent shorting out of the
arc column. The arc chute 200 is divided into the two arc chambers 220,224 with
separate arc splitter plates 222,226.
Example 5
The permanent magnets 216,218 are made of a shaped polymer-filled
magnetic material.
Example 6
The first permanent magnet 216 and the first ferromagnetic side
member 208 both form the first V-shape 232 having a first crest portion 246 facing
the second permanent magnet 218 and the second ferromagnetic side member 210.
The second permanent magnet 2 18 and the second ferromagnetic side member 210
both form the second V-shape 234 having a second crest portion 248 facing the first
permanent magnet 216 and the first ferromagnetic side member 208. The first crest
portion 246 is proximate the second crest portion 248.
Example 7
The crest portions 246,248 are proximate movable contact arm 250
(Figure 8) and proximate a movable contact 252 (Figure 8) between the movable
contact 252 and a pivot point 254 (Figure 8) of the movable contact arm 250. The Vshapes
232,234 form an example straight line (best shown in Figures 3, 4 and 7) for
ease of manufacture, and are preferably as close as possible to the movable contact
arm 250 and to the movable contact 252 while staying between the movable contact
252 and the pivot point 254.
Example 8
The permanent magnets 216,2 8 are suitably shaped (e.g., without
limitation, with a polymer-filled magnetic material). Another positive effect of such a
design can be the influence of the cross-section-reduction "behind" (to the right with
respect to Figure 7) the arc to drive the arc forward (to the left with respect to Figure
7) as a result of fluid dynamics. The example cross section reduction crest portions
246,248 "behind" (to the right with respect to Figure 7) the separable contacts 238
(Figure 8) increases the magnetic field at the location of the separable contacts 238,
improves the orientation of the magnetic field "behind" the separable contacts 238,
and moves the magnetic null further "behind" the separable contacts 238. This cross
section reduction also makes it relatively more difficult for arc gasses to flow in the
direction toward the crest portions 246,248.
Example 9
Figure 8 shows a bi-directional, direct current electrical switching
apparatus, such as the example circuit breaker 240, which includes the separable
contacts 238 in an open position, an operating mechanism 258 structured to open and
close the separable contacts 238, and the single direct current arc chute 200 of Figure
3. The separable contacts 238 include the fixed contact 242 and the movable contact
252 carried by the movable contact arm 250. The operating mechanism 258 includes
the movable contact am 250 carrying the movable contact 252 with respect to the
single direct current arc chute 200.
Example 10
The movable contact 252 carried by the movable contact arm 250
traces an entire path of motion between the closed position (not shown, although a
position intermediate the open and closed positions is shown in phantom line
drawing) of the separable contacts 238 and the open position (as shown in Figure 8)
of the separable contacts 238. The V-shapes 232,234 (Figures 3-6) form a straight
line for ease of manufacture and are preferably as close as possible to the movable
contact arm 250 and to the movable contact 252 while staying between the movable
contact 252 and the pivot point 254 of the movable contact arm 250.
Example 11
An arc forms between the fixed contact 242 and the movable contact
252 when the separable contacts 238 move from the closed position toward the open
position of the separable contacts 238. The arc is disposed between the end portion
214 of the third ferromagnetic member 212 and the first and second crest portions
246,248, and is driven toward one of the first and second arc chambers 220,224.
Example 12
The first permanent magnet 216 and the first ferromagnetic side
member 208 both angle toward the second permanent magnet 218 and the second
ferromagnetic side member 210 after the end portion 214 of the third ferromagnetic
member 212 along a portion of the path of motion of the movable contact 252. The
second permanent magnet 218 and the second ferromagnetic side member 210 both
angle toward the first permanent magnet 216 and the first ferromagnetic side member
208 after the end portion 214 of the third ferromagnetic member 212 along the portion
of the movable contact path of motion.
Example 13
The first V-shape 232 has the first crest portion 246 along a portion of
the movable contact path of motion, and the second V-shape 234 has the second crest
portion 248 along the portion of the movable contact path of motion.
Figure 9 shows another bi-directional, direct current electrical switching
apparatus, such as an example circuit breaker 300, in an open position. The circuit
breaker 300 can be similar to the electrical switching apparatus 100 of Figure 2, except
that it includes a first contoured gassing wall 302 disposed adjacent a first permanent
magnet 304, and a second contoured gassing wall 306 disposed adjacent a second
permanent magnet 308. Similar to the electrical switching apparatus 100 of Figure 2,
the circuit breaker 300 includes separable contacts 310 having a movable contact 312
and a fixed contact 314, and an operating mechanism 316 structured to open (shown
in Figure 9) and close (not shown) the separable contacts 310. The operating
mechanism 316 includes a movable contact arm 318 carrying the movable contact
312.
Somewhat similar to the direct current arc chute 8 of Figures 1 and 2, a
single direct current arc chute 320 includes a ferromagnetic base 322 having a first
end 324 and an opposite second end 326, a first ferromagnetic side member 328
disposed from the first end 324, a second ferromagnetic side member 330 disposed
from the opposite second end 326, and a third ferromagnetic member 332 disposed
from the ferromagnetic base 322 intermediate the first and second ferromagnetic side
members 328,330. The third ferromagnetic member 332 has an end portion 334
opposite the ferromagnetic base 322. The first permanent magnet 304 is disposed o
the first ferromagnetic side member 328 and has a first magnetic polarity facing the
third ferromagnetic member 332. The second permanent magnet 308 is disposed on
the second ferromagnetic side member 330 and has the first magnetic polarity facing
the third ferromagnetic member 332. A first arc chamber 336 is disposed between the
first ferromagnetic side member 328 and the third ferromagnetic member 332 and
includes a plurality of arc splitter plates 338. A second arc chamber 340 is disposed
between the second ferromagnetic side member 330 and the third ferromagnetic
member 332 and includes a plurality of arc splitter plates 342. The first permanent
magnet 304 and the first ferromagnetic side member 328 extend away from the first
end 324 of the ferromagnetic base 322 and beyond the end portion 334 of the third
ferromagnetic member 332. The second permanent magnet 308 and the second
ferromagnetic side member 330 extend away from the opposite second end 326 of the
ferromagnetic base 322 and beyond the end portion 334 of the third ferromagnetic
member 332.
However, in contrast to the direct current arc chute 8 of Figures 1 and
2, the first contoured gassing wall 302 is disposed adjacent the first permanent magnet
304, and the second contoured gassing wall 306 is disposed adjacent the second
permanent magnet 308. The movable contact 312 carried by the movable contact arm
318 traces a path of motion between the closed position (not shown) of the separable
contacts 310 and the open position (shown in Figure 9) of the separable contacts 310,
and the path of motion is disposed between the end portion 334 of the third
ferromagnetic member 332 and the first and second contoured gassing walls 302,306.
Figure 10 shows one 306 of the first and second contoured gassing
walls 302,306 of Figure 9. The other contoured gassing wall 302 is a mirror image of
the wall 306. The addition of gassing materials "behind" (e.g., to the right with
respect to Figure 9) the separable contacts 3 0 causes an additional flow of gas
toward the single direct current arc chute 320 to help drive the arc thereto.
Example 14
Preferably, a first insulating casing or insulator 344 is disposed about
the first permanent magnet 304, and a second insulating casing or insulator 346 is
disposed about the second permanent magnet 308.
Example 1
The first contoured gassing wall 302 is coupled to the first insulating
casing or insulator 344 about the first permanent magnet 304, and the second
contoured gassing wall 306 is coupled to the second insulating casing or insulator 346
about the second permanent magnet 308. These contoured gassing walls 302,306
improve the bi-directional switching and interruption capability at relatively high
current levels by driving the arc into one of the two arc splitter plates 338 or 342.
These also block the arc from entering into the reversed magnetic field and achieve
bi-directional DC switching and interruption capability, including relatively high
direct current levels.
Example 16
A magnetic field between the first and second permanent magnets
304,308 reverses direction at a volume of space distal from the first and second arc
chambers 336,340, beyond the end portion 334 of the third ferromagnetic member
332 and beyond the closed position of the separable contacts 310. The first and
second contoured gassing walls 302,306 are structured to block such volume of space.
Otherwise, the reversed magnetic field would push the arc away from the arc splitter
plates 338 or 342.
Example 17
The movable contact arm 318 includes an insulating casing or insulator
348 disposed thereabout.
Example 18
Each of the first and second contoured gassing walls 302,306 has a
curved portion 350 that approximates the path of motion of the movable contact 312.
Example 19
The end portion 334 of the third ferromagnetic member 332 also has a
curved portion 352 that approximates the path of motion of the movable contact 312.
Example 20
As was discussed above in connection with Figures 1 and 2, the direct
current arc chute 8 generates a magnetic field containing a null point 48 and a field
reversal which are relatively close to the back end of the two arc chambers 50,52
adjacent to the pivot point 39 of the movable contact arm 38.
As shown in Figure 9, during infrequent instances when an arc (not
shown) initially moves away from the arc splitter plates 338,342 at relatively high
current levels, the arc is large enough to cross the null point 48 (shown in Figure 2)
and enter the reversed field, which pushes the arc away from the arc splitter plates
338,342. The disclosed contoured gassing walls 302,306 block the arc from entering
into the reversed magnetic field to achieve bi-directional DC switching and
interruption capability at relatively high current levels. The addition of gassing
materials "behind" the separable contacts 310 causes an additional flow of gas toward
the arc chute 320 to help drive the arc toward the arc chute 320.
Example 2
The two example gassing walls 302,306 are added to the magnet
insulators 344,346 and block the volume where the magnetic field reverses its
direction and otherwise would push the arc away from the arc splitter plates 338,342.
Alternatively, the two gassing walls 302,306 can be an integrated part of the magnet
insulators 344,346. These support the arc quenching at a sufficient level of current
without affecting the magnetic field.
The magnet insulators 344,346 are preferably employed to prevent
possible breakdown or back striking during switching and interruption.
Both the entire movable contact arm 318 and the entire stationary
conductor 354 are preferably insulated. This prevents formation of an arc "behind"
(e.g., to the right with respect to Figure 9 and toward the pivot point 356 of the
movable contact arm 318) the separable contacts 310. An arc can form "behind" the
separable contacts 31 due to ionized gas from the initial arc, where the gap between
the movable contact arm 318 and the stationary conductor 354 is relatively small.
Example 22
The gassing walls 302,306 out-gas and move the arc toward the arc
splitter plates 338,342. In contrast, in Figures 1 and 2, the magnetic field near the
magnetic field null point 48 is not large enough to reliably move the arc (not shown)
toward the splitter plates (not shown) every time. The out-gassing of the gassing
walls 302,306 produces a gas pressure that prevents the arc from moving away from
the arc splitter plates 338,342 (toward the magnetic null point), and it also helps to
move the arc towards the arc splitter plates 338,342.
Example 23
Preferably, the gassing walls 302,306 are gassing inserts, which are as
large as possible behind the path of the movable contact 312.
While specific embodiments of the disclosed concept have been
described in detail, it will be appreciated by those skilled in the art that various
modifications and alternatives to those details could be developed in light of the
overall teachings of the disclosure. Accordingly, the particular arrangements
disclosed are meant to be illustrative only and not limiting as to the scope of the
disclosed concept which is to be given the full breadth of the claims appended and
any and all equivalents thereof.
What is Claimed is:
1. A direct current arc chute (200) comprising:
a ferromagnetic base (202) having a first en (204) and an
opposite second end (206);
a first ferromagnetic side member (208) disposed from the first
end of the ferromagnetic base;
a second ferromagnetic side member (210) disposed from the
opposite second end of the ferromagnetic base;
a third ferromagnetic member (2 2) disposed from the
ferromagnetic base intermediate the first and second ferromagnetic side members,
said third ferromagnetic member having an end portion (214) opposite the
ferromagnetic base;
a first permanent magnet (216) disposed on the first
ferromagnetic side member, said first permanent magnet having a first magnetic
polarity facing the third ferromagnetic member;
a second permanent magnet (218) disposed on the second
ferromagnetic side member, said second permanent magnet having the first magnetic
polarity facing the third ferromagnetic member;
a first arc chamber (220) disposed between said first
ferromagnetic side member and said third ferromagnetic member, said first arc
chamber comprising a plurality of arc splitter plates (222); and
a second arc chamber (224) disposed between said second
ferromagnetic side member and said third ferromagnetic member, said second arc
chamber comprising a plurality of arc splitter plates (226),
wherein said first permanent magnet and said first
ferromagnetic side member extend away from the first end of the ferromagnetic base
and beyond the end portion of said third ferromagnetic member,
wherein said second permanent magnet and said second
ferromagnetic side member extend away from the opposite second end of the
ferromagnetic base and beyond the end portion of said third ferromagnetic member,
wherein said first permanent magnet and said first
ferromagnetic side member extend toward said second permanent magnet and said
second ferromagnetic side member after the end portion of said third ferromagnetic
member, and
wherein said second permanent magnet and said second
ferromagnetic side member extend toward said first permanent magnet and said first
ferromagnetic side member after the end portion of said third ferromagnetic member.
2. The direct current arc chute (200) of Claim 1 wherein said first
permanent magnet and said first ferromagnetic side member are parallel with said
second permanent magnet and said second ferromagnetic side member between the
first end of the ferromagnetic base and the end portion of said third ferromagnetic
member; and wherein said second permanent magnet and said second ferromagnetic
side member are parallel with said first permanent magnet and said first ferromagnetic
side member between the opposite second end of the ferromagnetic base and the end
portion of said third ferromagnetic member.
3. The direct current arc chute (200) of Claim 2 wherein said first
permanent magnet and said first ferromagnetic side member both angle toward (232)
said second permanent magnet and said second ferromagnetic side member after the
end portion of said third ferromagnetic member, and wherein said second permanent
magnet and said second ferromagnetic side member both angle toward (234) said first
permanent magnet and said first ferromagnetic side member after the end portion of
said third ferromagnetic member.
4. The direct current arc chute (200) of Claim 1 wherein said first
permanent magnet, said second permanent magnet, said first ferromagnetic side
member, said second ferromagnetic side member and said third ferromagnetic
member are covered with electrical insulation.
5. The direct current arc chute (200) of Claim 1 wherein said first
permanent magnet and said second permanent magnet are made of a shaped polymerfilled
magnetic material.
6. The direct current arc chute (200) of Claim 1 wherein said first
permanent magnet and said first ferromagnetic side member both form a first V-shape
(232) having a first crest portion (246) facing said second permanent magnet and said
second ferromagnetic side member; wherein said second permanent magnet and said
second ferromagnetic side member both form a second V-shape (234) having a
second crest portion (248) facing said first permanent magnet and said first
ferromagnetic side member; and wherein the first crest portion is proximate the
second crest portion.
7. A bi-directional, direct current electrical switching apparatus
(240) comprising:
separable contacts (238);
an operating mechanism (258) structured to open and close said
separable contacts; and
the direct current arc chute (200) of Claim 1.
8. The bi-directional, direct current electrical switching apparatus
(240) of Claim 7 wherein said separable contacts comprise a movable contact (252)
and a fixed contact (242); and wherein said operating mechanism comprises a
movable contact arm (250) carrying said movable contact with respect to said single
direct current arc chute.
9. The bi-directional, direct current electrical switching apparatus
(240) of Claim 8 wherein said first permanent magnet and said first ferromagnetic
side member both form a first V-shape (232) having a first crest portion (246) facing
said second permanent magnet and said second ferromagnetic side member; wherein
said second permanent magnet and said second ferromagnetic side member both form
a second V-shape (234) having a second crest portion (248) facing said first
permanent magnet and said first ferromagnetic side member; and wherein the first
crest portion is proximate the second crest portion.
10. The bi-directional, direct current electrical switching apparatus
(240) of Claim 8 wherein said first permanent magnet and said first ferromagnetic
side member both form a first crest portion (246) facing said second permanent
magnet and said second ferromagnetic side member; wherein said second permanent
magnet and said second ferromagnetic side member both form a second crest portion
(248) facing said first permanent magnet and said first ferromagnetic side member;
and wherein said first crest portion and said second crest portion are proximate the
movable contact arm and proximate the movable contact between the movable contact
and a pivot point (254) of the movable contact arm.
1 . The bi-directional, direct current electrical switching apparatus
(240) of Claim 0 wherein an arc forms between said fixed contact and said movable
contact when said separable contacts move from the closed position of said separable
contacts toward the open position of said separable contacts; and wherein said arc is
disposed between the end portion of said third ferromagnetic member and the first and
second crest portions, and is driven toward one of said first and second arc chambers.
12. The bi-directional, direct current electrical switching apparatus
(240) of Claim 7 wherein said separable contacts comprise a movable contact (252)
and a fixed contact (242); wherein said operating mechanism comprises a movable
contact arm (250) carrying said movable contact with respect to said single direct
current arc chute in a path of motion between a first position in which said movable
contact and said fixed contact are closed and a second position in which said movable
contact and said fixed contact are open; wherein said first permanent magnet and said
first ferromagnetic side member both angle toward said second permanent magnet and
said second ferromagnetic side member after the end portion of said third
ferromagnetic member along a portion of said path of motion; and wherein said
second permanent magnet and said second ferromagnetic side member both angle
toward said first permanent magnet and said first ferromagnetic side member after the
end portion of said third ferromagnetic member along the portion of said path of
motion.
13. The bi-directional, direct current electrical switching apparatus
(240) of Claim 12 wherein said first permanent magnet and said first ferromagnetic
side member both form a first V-shape (232) having a first crest (246) along the
portion of said path of motion; wherein said second permanent magnet and said
second ferromagnetic side member both form a second V-shape (234) having a
second crest (248) along the portion of said path of motion; and wherein the first crest
is proximate the second crest.