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Патент USA US2134573

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Oct. 25, 1938.
w. E. PAUL
Filed May 1’7. 1938
2 Sheets-Sheet 1
Willi am E. paul,
Oct..25, 1938.
w_ E, PAUL
Fìled May 1'7, 1938
2 Sheets-Sheet 2
. .E
Patented ocr. 2s, 193s-
William E. Paul, Schenectady, N. Y., assignor to
General Electric Company, a corporation ofY
New York Y
‘Applicationguay 17, 193s, serial No. 208,392
14 Claims. (cl. zoo-iso)
My invention relates to electric circuit breakers
of the fluid blast type wherein are pressure gen
erated upon opening of the circuit is
produce'azi arc-extinguishing fluid blast. -~ „
Heretofore, diiiiculty has been encountered in
designing a circuit breaker of the aforesaid type
to interrupt satisfactorily currents ranging from
a few amperes to those of short circuit propor
tions. This is due to the great variation of arc
0 pressure at different current values for a given
length of arc, such as in the case of a high volt
age power circuit breaker of the Well-known oil
blast type. In order to produce an effective arc
interrupting blast, the arc pressure at. low cur
5 rents must be utilized to maximum/advantage. At
tional view, partly in section, of an electric cir
cuit breaker of the oil blast type embodying my
invention; Fig. 2 is an enlarged sectional w‘ew
of -the arc control contact structure shown by
Fig. 1; Fig. 3 is an elevational view in perspec- 5
tive, partly in section, illustrating another form
of my invention; Fig. 4 illustrates an arc control
contact structure particularly suitable for circuit
breakers having a wide interrupting capacity,
Fig. 5 is a fragmentary view of another form ci’ w
arc control device embodying my invention, and
Fig. 6 is a partly sectional view of an are control
device employing the induction principle also
embodying my invention.
The circuit breaker illustrated by Fig. i is of the 1g
oil blast type and .comprises a steel
high currents, however, the 'pressure may be well-known
pressure' confining casing i within ywhich is
dangerously high- unless the arcg chamber is in
stantly vented or the arc is restricted as to length. ' mounted relatively movable contact structure in
» Various solutions to this problem have been cluding a ñ‘xed contact structure .2, movable con
:0 proposed including control initiated by the arc- . tact 3, and intermediate gate contacts 4. _The 20
generated pressure. However, in view of the ~high contact structure is oil-immersed as indicated.
opening,- speeds. now required in practice, it is' The intermediate contacts are mounted on an in
sulating baiiie structure 5 forming Within the
highly desirable that the arc pressure be antici
pated ratherA than allowed to develop before casing i a lower arc chamber 6 and an upper ex
z5 initiation o1’ control. Other methods have also haust chamber l. The baffle structure 5 is pro- 25
been proposed such as, -for example, short cir
cuiting part of the arc in case of heavy currents,
and conversely looping and lengthening the are
in the case of weak currents. However, these
5o methods are not always practical and satisfac
tory for particular operating requirements.
In accordance with my invention excessively
> high arc pressures are anticipated by électro
vided with a.` transverse passage 8 interconnecting
the chambers 6 and 'l` and also intersecting a
longitudinal bore 9 through which the movable
rod contact 3 operates. The conducting> gate
contacts 4 are, normally biased by springs 4' to 30
close the bore 9 at its lower end when the contact Y.
3 has moved past the gates toward the open
circuit position. In the closing operation the
magnetic meansresponsive to the magnitude of contact 3 simply biases the gates apart and moves
35 the current to be interrupted. More particularly, through the bore 9 into the arc chamber 6 to
the circuit breaker functions normally at, low engage the ilxed contact structure 2. The cir
cuit breaker structure so far described forms no
current values for developing suiiicientarc pres
sure to interrupt'arcing, whereas at high or short part of my present invention and is described
circuit currents the pressure-generating arc is in detail and claimed inv my U. S. Patent No.
1,947,224 for Circuit interrupting apparatus,
40 automatically shortened by utilizing electromag
granted February 13,- 1934.
netic forces‘in the circuit that is yto be inter
rupted for moving an electric conductor, which \ In the operation of this breaker, a pressure
generating arc is formed between the ñxed con
may form part of the contact structure, with re
spect to the arc path. With this' arrangement ` tact structure 2 and the intermediate or gate
45 excessively high arc pressures are anticipated contacts 4, the pressure generated within the
since the control is independent of the time of ~ oil-filled chamber 6 being utilized to create an
contact separation and solely dependent on the arc-extinguishing blast through the passage 8
transversely of the arc between the gate and
magnitude of the current to be interrupted.
My invention will be more fully set forth in the movable contacts when the contact structure is
in the position illustrated.
50 following description referring to the accom
Where the length of the pressure-generating
panying drawings, and the features of novelty
which characterize my invention will be pointed
out with particularity in the claims annexed to
and forming a part of this speciñcation.
Referring to the drawings. Fig. 1 is an eleva
Yarc in the chamber 6 is substantially ñxed, it
will be apparent that although thebreaker may
work well on low or medium currents, for ex
ample, the pressure generated in the case of 55
short circuits may be so great as to damage or
destroy the breaker.
For the purpose of anticipating these excessive
pressures, I utilize electromagnetic forces of the
circuit to be interrupted to shorten automatically
the pressure-generating arc to an extent de
pending on the magnitude of the arc current.
To this end the ilxed contact structure 2 is pro
vided with an arcing member, such as a ring or
10 bell l0 that is relatively movable with respect to
the fixed structure along the path of the pressure
generating arc.
Referring more particularly to Fig. 2, which
illustrates the ilxed contact structure 2 in sec
15 tion and in greater detail, the main contact sup
port comprises a conducting frame II that is
suitably expanded at its lower end, as illustrated
in Fig. l, into good electrical contact with the
terminal portion I ' of the steel casing I. The
20 support I I can be generally in the form of a cyl
inder open at opposite ends and has'mounted
the case of higher currents the arc can be auto
matically shortened to la point comparatively
`close to the intermediate contact structure 3 as
illustrated in the dotted line position shown in
Fig. 1.
It will also be noted that the circuit includes
another loop formed by the segmental contacts
I3, flexible conductors I1 and the cylindrical car
rier I2. In this case the expanding iorcœ of'
the loop tend, in the case of heavy currents, to 10
bias'the segments I3 into good `contact engage
ment with the rod contact 3 for minimizing heat
ing due to contact resistance. Thiais an obvi
ous advantage, particularly where the normal
current rating of the breaker is high. In the case
oi' arc interruption the added friction between
the segments I3 and rod contact 3 may cause the
rod contact to. carry with it the arc control unit.
However, whenl its upper limit is reached the
contacts separate and if the current is sum
ciently high, the unit will remain in its short
thereon an arcing ring I0 which is provided with arc position; otherwise, the spring I3 will retract
a cylindrical depending extension I2 serving as the unit to an extent depending on the arc cur
a carrier for the segmental contacts I3 coacting rent. Therefore, the arc pressure is anticipated
25 with the rod contact 3. The segmental contacts in any case.
I3 are suitably biased in a well-known manner
Referring to Fig. 3 there is _illustrated a com
into contact with the rod 3 by garter springs I3 _«paratively~compact fixed contact unit arranged
and are electrically insulated _at I5 and I3 from generally to function in the manner of Fig. l.
the conducting carrier I2. The segments, how lIn this latter arrangement Athe circuit breaker
30 ever, are electrically connected byflexibleP leads structure is essentially the same and the fixed
Il to the lower end only of the carrier for .the contact structure likewise has several similar fea
purpose presently described.
tures. 'I‘he contact support as in the previous
The arcing ring I0 and carrier I2 constitute case is expanded at 23, such as by a pin wedge
a unit that is adapted for relative movement with at 23', into good contact engagement with the
35 respect to the frame II. 'I'he unit is normally steel casing I,'and an arcing bell 23 having a
biased to its position shown «within the frame>
depending cylindrical carrier 21 for the contact
by a helical spring I8 seated between an annular
segments (not shown) is mounted, as in the case
of Fig. 2, for relative movement in the frame 23.
Secured and electrically connected at 23 to the
insulating abutment I3 secured to the frame II
and an insulating collar 23 secured to the lower
end of the carrier I2. The carrier unit is limited
conducting frame 23 is a discontinuous ring 23
as to vertical movement by a lower abutment 2|
also connected at 33 by_ a flexible looped con
and an upper abutment 22 forming part of the
ductor 'to a counter or second discontinuous ring
23'. The ring 23’ is secured and electrically
connected to the bell 23 only at 3| so that the
frame coacting with the insulating collar 23.
The conducting frame II and the arcing‘ring I3
45 are electrically interconnected by looped flexible
conductors 23 designed to permit movement of
the arcing ring between the upper and lower lim
its previously described.
ring-like conductors 23 and 23' together with the
flexible conductor 33, form a loop that is bent
around the longitudinal axis of the arcing bell 23.
The arcing bell 23 and carrier-21 are suitably
biased by a spring (not shown) to a retracted
position within the frame as in the case of Pig. 2,
In the closed circuit position shown (Fig. 2),
50 the circuit from the terminal of the movable
contact 3 to the terminal formed Vby the casing the spring being omitted in the interest of clear
I i's completed through the rod contact 3, seg
mental contacts I3, electrical connections I1,
In the operation of the device, the pressure
conducting carrier I2 and arcing ring I3, con l generating-arc, as in 'the previous case, is formed'
55 ducting loops 23, and conducting frame II. It
between the arcing bell 23 and the intermediate
will therefore _be noted that the circuit includes
contact structure 3. The path of the are current
through the nxed contact structure _is as indi
cated by the directional arrows, the current flow
ing from the arcing bell 23 through the ring 23'
in a clockwise direction as viewed, and through
the flexible conductor 33 in counterclockwise di
rection through the counter ring 23 which is me
chanically and electrically connected to the fixed
conducting contact support 2l. The segmental
contacts (not shown) can if desired be connected
a loop at the conductors 23 that can expand,
carrying with it the arcing ring _I3-, when current
of predetermined magnitude iiows through the
60 circuit.
Since the arcing ring I3 is at all“- times
electrically connected to the ilxed'contact struc
ture 2, movement of the carrier I2upwardlyagainst
the bias of spring I3 inresponsetoelectromagnetic
force of large currents automatically shortens the
65 arc distance between the intermediate contacts
4 and the fixedl structure 2. The pressure-gen
erating arc is correspondingly decreased in length.
and it will be apparent that the spring tension
at I8 and the design of the conducting loops 23
in the circuit in-the manner shown in Fig. 2.
When Athe breaker is opened the electromag
netic repulsion between the rings 23 and 23' due
may be so chosen that the pressure-generating
arc has a definite and predetermined length forv
a given current ñowing through the breaker.
With this arrangement the breaker can be de
21.) in an upward direction tending to shorten
signed so that the normal arc length at low cur
75 rents is sufilcient for arc interruption, and in
to the opposing directions of the current paths
causes extension of the arcing unitl (23, 23' and 70
the arc to an extent depending on the magnitude
of the arc current. This arrangement is obvi
ously more compact than that of Fig. 1 since the,
loop for utilizing the electromagnetic forces of 75
the circuit is concentrically disposed with respect
to the arc and in etfect bent back upon itself, as
contrasted with the laterally extending loops 23
of Figs. 1 and 2. '
mounted within a conducting support 4| that is
electrically connected to a terminal of the
breaker.- The relatively movable arcing ring 42
is in the present instance pivotally mounted with
respect to the support 4I by means of an arm 43 5
'I'he arrangement shown by Fig. 4 is particu
larly adapted to utilize to the maximum extent
the electromagnetic forces involved in a circuit
`sion 45 of the contact. carrier. A spring 46 func
loop associated with the movable arcing mem
ber. To this end the relativelymovable arcing
tions to keep the arcing ring normally in the re
tracted position shown, and a stop member 45'
member 34, which may ‘also constitute the con
tact structure, is electrically connected» at 35 to
in- the opposite direction.
an insulated conductor I36 that is normally ar
ranged in a ilattened double loop and connected
at its ether terminal at 31 to the conducting
expanding ring 31' corresponding in function to
the expanding ring 25 of Fig. 3. The movable
arcing member t4, which can be suitably formed
pivotally connected at 44 to a conducting exten- '
iixed to the support 45 serves to limit movement 10
The conducting loop. in the present instance
for' controlling the positionA of the arcing ring is
formed by the conducting members $3 and 45
and to this end the aforesaid members are elec
trically connected by a _flexible conductor at 41
adjacent the pivot 44 and are provided with `an _
insulating spacer' 48 for preventing short cir
cuiting of the loop. The operation is believed to
as a socket contact, for example, for coacting
with the contact tip of the movable rod 3 is
mounted for limited reciprocal movement with
respect ’to an insulating cylinder 38 having a
central bore’ 38’ within which a guide extension
39 of the movable member 34 is disposed. The
traversing the loop 43-45 to control the position
of the arcing ring in accordance with the mag
insulating cylinder 38 is ñxed within the expand
ing ring 3l'. _The extension 39 is resiliently
paratively simple in that the breaker in the 25 ï
biased by a helical spring 39' toward the re
tracted position shown. Accordingly, when cur
closed circuit position utilizes simply the con
ventional contact structure, the arcing ring func- i
rent traverses the breaker the insulated looped
tioning only upon opening of the circuit on
heavy or short circuit currents. The relation
between arc length and arc current can readily 80
conductor 36, which is suitably secured at one
point to the movable arcing element 34, such as
by a clip -member 38', tends to expand so as to
icrm a circle. Expansion of the loop is opposed
by the spring 38' which is selected as in the pre
vicus case in accordance with the operating re
Imiii‘ements of the breaker.
'ïhe insulated conductor 36 can obviously form
any desired number of loops in order to meet the
be apparent from the above description, the arc
current after transferring to the arcing ring 42
nitude of the arc current.
This design is com
be chosen by suitable adjustment of the’spring
tension at 46, and also by changing the dimen
sions of the Íloop Íi3--4B.
In the arrangement shpwn byFig. 6, the in
duction principle is employed for the purpose of
‘simplifying the structure in certain cases and for
anticipating high arc pressures in the manner
previously referred to. To this end the magnetic
force for moving the arcing member for decreas
ing the arc length is obtained from induced'cur
the number ci coils can be increased. The con
ductor loops are also preferably designed so that l rent instead of :from a direct series connection.
Referring more particularly to the structure
the arcing member 34 is at the position of mini
mum arc length when the loop is in the form of disclosed, the expanding member or ring 50 for
securing and electrically connecting the contact
a substantially complete circle. 'With this ar
rangement the electromagnetic forces acting on structure to the lower part _of the breaker casing
the loops are substantially dissipated iii/hoop asin thepreceding cases, is electrically connected
through a. series coil 5| to the ñxed contact struc
tension and the movable arcing unit is accord
ingly not _subjected to high mechanical stresses ture 52';which coacts with the movable rod con
when in the, position of minimum. arc length. ' tact 3. 'In the present case the fixed contact 52 ‘
When the circuit is interrupted the' spring 39' is-.mounted within a stationary insulating cylin- 5o
returns the arcing member 3l to its initial re “der 53 that'is secured to the switch casing in any .
particular design requirements of the breaker.
For example, where lateral space is restricted,
tracted position where it remains in they case ofv suitable manner, the cylinder being provided
with lateral ñanges 53' for positioning the arc
small current interruptions.
' In the arc control devices so far described, it
should be noted that the electromagnetic forces
tending to iniluence the position of the arcing
member are present before the arc is actually
formed. Accordingly,- there is a 'tendency to
initiate and accelerate the movement of the'
arcing member before thè arc is drawn. This is
particularly important in the case of short cir
control means.
The movable arcing member for decreasing the
arc length in accordance with the magnitude of
the current _comprises in the present instance a
-conducting sleeve 54_of copper or the like mounted
around and concentrically of thev insulating cyl
inder 53. The sleeve 54 is biased by a spring 55
seated on the upper flange 53’ of the fixed cylin
der 53 toward a retracted position with respect
the oil by the are might otherwise retard the to the arc path, and as showrris- in the maximum
arc-'regulating operation of the arcing member. v_ arc length position. For the purpose of relieving
This is overcome according to my >invention by gas pressures a‘nd eliminating piston eil'ect, the
cuit currents since the`pressure generated within
' applying the electromagnetic forces to’ the arcing
member so that it moves along with the movable
contact until it reaches itsregulating position as
sleeve 54 is- provided with apertures‘54'.
When current of predetermined magnitude
traverses the series coil 5l current is induced in -
determined by the-magnitude of the arc current. the conducting ring 54, which forms in effect a
other words, _the‘control anticipates` excessive short-circuited secondary of la transformer, so 70
‘ that the primary and induced cur'rents flowing
arc pressure _due to a long, heavy current arc.
Fig. 5 illustrates a simplified arrangement
wherein the _nxed segmental contacts 4l! coac\t
with the rod contact 3 in the manner above de
scribed, the segmental contacts being suitably
in opposite directions establish a repellant force
tending to raise the ring 5,4 against the bias of
_ spring 55 to the arc-controlling position required.
The are lsìthereby bridged in part, the total arc '
2,134, 578
length then comprising the two short arcs formed
between the rod 3 and ring 5l, and the ring Il
and iìxeo'; contact 5t.
Accordingly; the arc pressure is anticipated
_even before separation of the contacts, since the
movement of the arcing member is entirely inde
pendent of the movable contact structure. A
particular advantage oi' this arrangement resides
said member towards a retracted position with
respect to said arc path and ñexlble conducting
means interconnecting said member and ñxed
contact forming a loop for moving said arcing
member into the arc path to an extent depending
on _the magnitude of the arc current.
6. An electric circuit breaker ot the fluid blast
type comprising relatively ilxed, movable and
in the fact that flexible conductors, or “pigtails”,
intermediate contact structures arranged so that
the arc pressure generated between said inter
unnecessary but may be used if desired. ‘
mediate structure and one of said other structures
It should be understood that> my invention is , tends to interrupt the circuit, and arc control
16 connected to the movable arcing member are
not limited to speciñc detalls of construction and
arrangement thereof herein i11ustrated,"a.nd` that
15 changes and modiñcations may occur to one
skilled in the art without departing from the
' spirit of` my invention.
What I claim as new and desire to secure by
Letters Patent of the United States, is:
i. An electric circuit breaker of the fluid blast
type comprising separable contact structure be
tween which an arc»is formed upon opening of
the circuit, a movable arcing member and electro
magnetic means controlled by the arc current for
moving said arcing member with respect tothe
arc path so as to decrease the length of said arc
to an extent depending on the magnitude of the
.arc current.
2. fm electric circuit breaker of the arc-gener
l ated ñuid blast type comprising separable con
tact structure between which a pressure-gener
ating arc is formed upon opening ofthe circuit,
an arcing member movabie with respect to one
of the contacts, and electromagnetic means con
V, trolied by the arc current for causing movement
of, said arcing member into the arc patli‘so» as to
decrease the length of said arc to an extent de
pending on the' magnitude ofthe arc current.
3. en electric circuit breaker of the arc-gener
ñuid blast type comprising a pair of rele.u
"rely movable contacts between which an arc is
formed upon opening of the circuit, contact struc
ture positioned intermediate said contacts in the
open circuit position thereof, an arcing member
one of 'said contacts, said arcing
movable beyond said contact 'tc
trard said intermediate contact structure and into
the arc path, and electromagnetic means ccn
troïìed by the arc current for causing movement
of said srcirig member so as to decrease the
length of the arc between said arcing member
and intermediate contact structure te ar. extent
depending on the magnitude of the are current.
é. .en electric circuit breaker of the arc-gener
biast type comprising separable contact
structures between which an arc is formed upon
cpenng of the circuit, an arcing member eiec
trîcail; connected to and movable with respect
c- c’ the contacts and electromagnetic means
._ ' by the arc current prior to separation
said contact structure for moving said arcing
member with respect tc the arc path so as to
decrease the ‘length of said arc tc an extent de
pending on the magnitude of the arc current,
said eiectromegnetíc means tending tc initiate
the movement of said arcing member at the um»
stent overload occurs `whereby generation of ex~
cessiye src pressure is anticipated.
means for the pressure generating arc including
an arclng member movable with respect to one of
said contact structures into the arc path, and elec 15
tromagnetlc means for biasing said arcing mem
ber into the arc path for shortening said arc to
an extent depending on tbe magnitude of the arc
7. An electric circuit breaker of the arc-gener 20
ated iluid blast type comprising a ñxed contact»
and a relatively movable contact between which
a pressure-generating arc is formed upon separa
tion of said contacts, arc control means mounted
for relative movement with respect to said fixed
contact comprising an arcing ring movable be
tween said fixed contact and a position beyond
the same into the arc path, means biasing said
arcing ring towards a retracted position with re
spect to said path, contact means for coacting
with said movable contact carried by and movable
with said arcing member, and iiexibie conducting
means inter-connecting said fixed contact struc
ture and said arcing ring, said conducting means
being formed as a loop so that the electromagnetic
forces of the arc current tend tc bias said arcing
ring into the arc path to an extent depending on
the magnitude of the arc current.
8. An electric circuit breaker of the arc-gen
erated fluid biast type comprising iîsed contact
structure and a coacting movabie Contact,
control structure mounted for reiat‘ve move
ment with respect to said nxed cen-tac; struc
ture comprising an arcing ring adapted tc coac‘i'.
with said movable contact, a contact ce.L ler se
cured to and dependingrfrom said arcing ring, a
plurality of contact elements mounted in said
carrier for engagement with said movable con
tact, means electrically connecting said contact
eiements to said carrier oniy at one end thereof,
means eiectrically connecting the opposite end
of'said carrier at said arcing ring to said fixed
contact structure, said means forming a loop
arranged sc that said arcing ring is biased into
the arc path to an extent depending on the mag
nitride of the arc current traversing said loop,
said contact -lcments being likewise biased into
contact engagement with said movable contact
in e. similar manner, and spring means for bias~
ing said arcing ring and contact carrier towards GO
a retracted position with respect to said arc path,
9. An electric circuit breaker of the arc-gen
erated fluid bïast type comprising ñxed and mov
abîe contact structures, arc control means as
sociated with said Sxed structure including a
conducting member in the form of a discontin
nous ring, said ring being eiectrically and rigidiy
connected at one end to said'iixed structure, a
“_ „en electric circuit breaker of the arc-gener
,- ated
bias; type comprising a fixed contact
relativeiy movabie discontinuous ring generally
similar to said first ring in superposed position
with res
t to said ñrst ring, flexible conduct«
ing means interconnecting the free end of said
a ccactin'g movable contact, an arcing mem
__ ber mounted on said fixed contact for reciprocal
-~rectilinear movement with respect thereto, said
ar'cmg member being adapted to extend beyond
said ized contact into the arc path, means biasing
first ring and one end of said second ring, con~
tact means including an arcing member mount
ed for mcïement with said second ring, said 75
said fixed structure comprising an arcing mem
second ring and arcing member being electrically
ber, aS flexible conductor normally formed as a
connected at another» end of said ring so that
compressed coil having a plurality of turns elec
arc current ilowing from said arcing member to
said fixed contact structure traverses said rings ' trically interconnecting said fixed structure and
5 in opposite directions whereby said arcing mem
ber is biased into the arc path to an extent de-`
arcing member, said coil being mechanically
connected at one terminal to said arcing member
pending on the magnitude of the arcflcurrent, - whereby expansion of _said coil due to passage of
and resilient means for biasing in the opposite arc current therethrough tends to move said arc
ing member into the path of the arc for decreas-direction said arcing member.
ing the length thereof, and means resiliently 10
10. An electric circuit breaker oi the arc-gen
said arcing member in the opposite direc
erated fluid blast type comprising relatively vmov
tion, the minimum arc length position of said
able contact structure between which a pressure
generating arc is formed upon separation of said arcing member being determined by the fully
contact structure, are control means associated extended position of said coil whereby the elec
with one of said contact structures comprising tromagnetic stresses at high currents are sub
an arcing member adapted to move into the stantially dissipated in hoop tension.
13. An electric circuit breaker of the fluid
path of said arc for decreasing the length there
of, and electromagnetic means for controlling blast type comprising separable contact struc
the position of said arcing member in said path ture between which a pressure-generating arc is 20
to an extent depending on the magnitude of the
arc current comprising conducting means inter
connecting said contact structure and said arcing
member, said conducting means forming a cur
rent path in the shape of a compressed loop that
is positioned substantially eoncentrically with
respect to said arcing member.
11. An electric circuit breaker of the arc-gen
erated iiuid blast type comprising relatively mov
able contacts between which a pressure-gener
ating arc is formed upon separation thereof, one
of said contacts including a- relatively movable
arcing member adapted to move into the are
path for decreasing the length of said arc, and
a flexible conductor interconnecting said con
I tact and arcing member, said conductor being
formed as a coil so that' arc current traversing
said conductor tends to move said arcing mem-_
ber into the arc path to an extent depending on
the magnitude of the arc current whereby the
40 minimum arc length position is attained when
said conductor assumes a generally circular form.
12. An electric circuit breaker of the arc-gen
erated fluid blast type comprising fixed and mov
able contact structures, arc control means
ß mounted for relative movement with respect to
formed upon opening of the circuit, and arc con
trol means associated with one part of said con
tact structure including a conducting `\’arcing
member movable with respect to said part into
the are path, means for resiliently biasing said
member towards a retracted position with respect 25
to said arc path, and means traversed by the arc
current related to said arcing member so that
said arcing -member is repelled by magneticv
forces into the arc path to an extent depending
electric circuit
of saidbreaker
arc current.
of the fluid" blast
type comprising separable contact structure be
tween whicha pressure-generating arc is formed l
upon opening of the circuit, a movable arcing
member forming a short-circuited conductor, 35
means resiliently biasing said arcing member >
toward a retracted position with respect to the
are path, and means traversed by the arc cur
rent associated with said contact and inductively
related to said arcing member, said arcing mem 40
ber being. repelled into the arc path by the re
sulting magnetic forces to decrease the length
of the arc to an extent depending on the magni
tude of the arc current.
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