Note: Descriptions are shown in the official language in which they were submitted.
~lZ8980
This invention relates to circuit interrupters, and
more specifically relates to a novel a~c runner construction
for the arc runner of ~n arc spinner t~pe of circuit
interrupter.
lhis application is related to copending Canadian
applications Serial No. 318,651, filed December 27, 1978
in the names of Lorne D~ ~cConnell, ~erald A. Votta and
Donald E. Weston, entitled ~lOVING CONTACT FOR P~DIAL BLOW-
IN E~FECT FOR ARC SPINNER INTERRUPTER; Serial ~o. 318,652,
filed December 27, 1978 in the name of Robert Kirkland Smith,
entitled EXTERIOR CONNECTED ARC RUNNER FOR ARC SPINNER
INTERRUPTER both o~ which are assigned to the assignee of
the present invention. This application is a divisional
application of copending application No. 326,707 filed ~5ay
1, 1979.
Arc spinner tvpe interrupters are known in the art
and are tvpically shown in U.S. Patent ~,052,577, in the name
of r~erald A. Votta, as well as ~.S. Patent ~,052,576, in the
name of Robert Kirkland Smith.
In these devices, a flat conductive ring, hereinafter
called the arc runner, is provided which is disposed in a
plane per~endicular to the axis of the interrupter and
perpendicular to the flow of arc current.
- 2 -
llZ8~80
- 3
during circuit interruption. This arc runner is then
electrically connected in series ~ith a coil to l~hich it
is closely coupled. A movable contact is then arranged
to make annular contact engagement and disengagement with
a cooperating annular surface of the arc runner facing
away from the coil. l~en the contact opens, an arc is
dra~n from the arc runner to the movable contact and the
arc current flows through the coil. This then induces a
circulating current in the arc runner, ~hich is a shorted
turn, and both the arc runner and coil then produce a
resultant magnetic field in the region of the arc.
The magnetic field component from the arc
runner circulating current is displaced in phase from
that of the coil so that a fairly substantial field is
present just before a current zero interval. The effect
of the arc current in the magnetic field produced by the
arc runner and coil is such that a Lorentz force is
established which tends to rotate the arc around the arc
runner. This rotational movement of the arc is through a
. 20 relatively static dielectric gas which fills the arc
space and thereby tends to deionize and cool the arc so
that the arc can be interrupted at the first current zero.
A problem exists in such interrupters when lo-
~currents (below about 3000 amperes) ~ith high transient
recover~ voltage (TRV) fre~ucncies of about 20 k l~z.
Thus, in this lo~ current range, the arc is interrupted
in a plain break r.~ode and not in a rotating arc mode.
llZ8980
Standard arc-resistant materials, such as copper tungsten
alloys, perform well in the plain break mode, but they do not
work well in the rotating arc mode. Standard electrolytic
copper performs very well in the rotating mode, but does not
work well in the plain break condition. Therefore, in the
past, it has been necessary to provide auxiliary means, such
as a puffer assist, to allow the use of electrolytic copper
for the rotating arc mode while giving the interrupter low
current, high frequency TRV interruption capability.
In copending application No. 326,707 there is dis-
closed and claimed a circuit interrupter comprising a
stationary contact assembly; a movable contact assembly;
a dielectric gas filled housing containing said stationary
and movable contact assemblies; and stationary contact
assembly including an arc runner contact and an electrical
coil and circuit connection means for connection said elec-
trical coil in series with said arc runner contact; said arc
runner contact containing, as at least a portion thereof,
a generally flat conductive disk having an axis which is
coaxial with the axis of said coil; said coil being disposed
adjacent one surface of said arc runner contact and being
in a plane parallel to the plane of said arc runner contact
and being closely magnetically coupled to said arc runner
contact; said movable contact assembly including a generally
cylindrical arcing contact which is coaxial with said arc
runner contact, and which is movable into and out of contact
with the surface of said arc runner contact which is opposite
to said one surface; at least one of said arc runner contact
and said movable arcing contact consisting of an alloy of
chromium copper to improve interruption capability.
According to the present invention there is provided
an arc runner for an arc spinner interrupter; said arc
runner including a flat annular ring consisting of an alloy
of chromium copper to improve interruption capability.
llZ8980
Thus in accordance with the invention, the arc
runner is made of a chromium copper alloy having about 0.9%
chromium by weight. It has been found that this material
has relatively high conductivity relative to copper (about
85~ of the conductivity of copper), and that it also
has relatively low arc erosion and good transient recovery
voltage withstand capability. Thus, the arc runner can be
used ~or interruption in both plain break and rotating arc
modes, without need for auxiliary means to assist interrup-
tion at low current.
- 4a -
11;Z8980
-- 5
BRIE~ DlSCRIYTIOIN OF TIIE DRAI~'INGS
Figure 1 is a side elevational viet~ of a
circuit breaker ~hich could incorporate the concept of
the present inventiorl.
Figure 2 is a front elevational vie~ of Figure 1.
Figure 3 is a top viel~ of Figures 1 and 2.
Figure 4 is a cross-sectional vie~ taXen along
the axis of one of the three interrupters of Figures 1, 2
and 3 and illustrates an interrupter with a center-fed arc
runner and shol~s the interrupter open above the center
axis and closed belo~ the center a~is.
Figure 4a is an electrical circuit di.agram of
the structure sho~n in Figure 4.
Figure 4b is an enlarged cross-sectional diagram
of the coil assembly of Figure 4v
Figure 5 is a perspective viel~ of the stationary
contact and arc runner shol~n in Figure 4.
Figure 6 is a perspective vie~Y of the movable
contact assembly of Figure 4.
Figure 7 is a cross-sectional vie~.~ of Figure 4
taXen across the section line 7-7 in Figure 4.
Figure 8 is a cross-sectional vie~ of Figure 4
taXcn across the section line 8-8 in Figllre 4.
Figure 9 is an end viel~ of the right-hand end
of Figure 4.
llZ8g80
-- 6
Figure 10 is an cnlargccl v;e~ of the statiol~ary
contact and arc runner of Figure 4 moclificd so that
current to the arc runner is connected at its outer
diameter.
Figure 11 scheinatically illustrates the arc
current ~etween the arc runner and the movable arcing
contact for different conditions of current feed to the
inside and outside of the arc runner and further sho-~s
different conditions of current flow, for inside feed and
outside feed to the arcing contact.
Figure 12 shows low current test results of
apparatus of the type sho~n in Figure 10 using a chromium
copper alloy arc runner, as compared to one using a
copper arc runner.
Figure ]3 shol.~s lo~ current test results
comparing the use of copper, copper tungsten, and
chromium copper materials at high TRV frequency.
DETAILED DESCRIPTION OF THE DRAl~INGS
.
Figures 1 to 3 illustrate a typical circuit
breaker which uses circuit interrupters of the type
constructed in accordance with the present invention.
Referring to Figures 1 to 3, the circuit breaXer is
mounted on a steel support frame 20 and is sho~vn as a
three-p]lase circuit breaker containing phases 21, 22
and 23. Each of phases 21, 22 and 23 consist of
ilZ~39~0
- 7
idcntical intcrr~1pters, one o ~hich ~ c (~c~;cribed
more flllly hereinafter, conta;ned in respective aluJninum
tanks 24, 25 and 26, \~hich have terminal bush;ngs 27-28,
29-30 and 31-32, respectively. Each of housings 24, 25
and 26 are capped at their right-hand end in Figure 1
and communicate with an operating mecl~anism housing 35,
~hich may include a jack-s}laft linkage which is coupled
to the interrupters within each of housings 24, 25 and
26 The operating mechanism is operable to simultaneously
open and close the three interrupters. Any suitable
- spring closing mechanism or the like, shown as the spring
closing mechanism 36, can be used to apply the input-
energy for the jack-shaft linkage in housing 35. Thus,
an operating linX 37 extending from the spring mechanism
36 is connected to an operating link 38 (Figure 1) ~hich
in turn rotates shaft 39 which is coupled to the inter-
ruptcrs of each phase as will be more fully described
hereinafter.
It is necessary that the housing 35 be sealed
since it will be filled with a suitable dielectric gas
such as sulfur hexafluoride and permits communication of
the insulating gas bet~een the interiors of all housings
24, 25 and 26.
The circuit breaXer described above is suitable
for use in connection l~ith a 15kV/25kA three-phase out-
dool~ circuit breaker and can have a total heigllt of aboutS2 inches ~ith frame and a total ~idth in Fig~rc 1 of
about 3g inches.
112B980
-- 8
The interior of ~he interrupter for cach phase
is sho~n in Figure 4 for the case of phase 23 cncased
by housing 26. Ilousing 26 may be of steel or of any
other desired material and contains two openings 40 and
41 for rcceiving the bushings 31 and 32. Thus, openings
40 and 41 have short tubes 42 and 43, respectively,
welded thereto, which tubes receive suitable terminal
bushings 31 and 32 in any desired manner.
The terminal bushings 31 and 32 then have
central conductors 44 and 45, respecti~ely, whic]l are
terminated with jaw type contacts 46 and 47, respectively,
which receive movable contact assembly 48 and stationary
contact assembly 49, respectively, as will be later
described.
The right-hand end of housing 26 is capped by
an end assembly including seal ring 50 (Figure 4) which
contains a sealing gas~et 51 ~igure 4), an aluminum
support plate 52 ~Figures 4 and 5) and an end cap plate
53 which may be of steel. Ring 50 is welded to the right-
hand end of tube 26 and provides a bolt-hole ring. The
aluminum disk 52 is held in the position shown by the
plate 53 when the plate is bolted to the ring 50 as by
the bolts 54 and S5 sho~n in Figure 4. Note that plate
53 is sho~n in both Figure 4 and Figure 9 and, ~hen the
~late 53 is bolted up against the ring 50, it forms a
leaX-proof seal against the sealing ring 51.
~12898Q
g
]he opl~osite end of tube 26 h~s ~ ~)olt r;ng 60
l~e]ded thereto ~hich has a three-lo~e t~pe opening as
best sho~n in Figure 7. A short tube sect;on 61 is
then provided ~ith a seal;ng r;ng 62 conl-lected to ;ts
end ~hich receives a seal;ng gasket 6~ The outer
diameter of ring 62 contains a bolt ring circle having
bolt open;ngs ;n alignment ~ith the bolt openings in
member 60 so that bolts SUC]I as bolts 65 and 66 in
Figures 4 and 7 can secure together housing sections 26
and 61 with a good gas-tight seal being formed by the
seal 63.
The left-hand of section 61 ;9 then welded into
an opening in the tank 35 as sho~n. Thus the interior
of tube 26 and of the various elements .ith ~h;ch it
communicates are sealed from the external atmosphere and
the interior of tube 26 is filled ~ith sulfur hex~fluoride
at a pressure of about 3 atmospheres absolute. Note
ho-.ever~ that any desired pressure could be used and that
any dielectric gas other than sulfur hexafluoride or
combinations of dielectric gases as desired could be used
in place of sulfur hexafluoride.
The movable contact assembly 48 is best sho-~n
in Figures 4 and 6. The movable contact assembly is
connected to the operating crank 3~ of Figure 4 ~hich is
driven by the operating mechanism through a connecting
link 70 ~hich is pivotally conllected to the end of
elongated axially mo~able conductive member 71. Movable
~lZ8980
- 10 -
mcmber 71 is a conductive elongatcd hollow rod h~lv;ng a
closed end at its left w?lere the closed end portion at
its left-hand end is provided with a plurality of vents
such as vents 72 and 73 which, as will be described
hereinafter, permit flow of gas and arc plasma through
the movable contact and through these vents during an
interruption operation.
Movable member 71 is g~ided for motion by a
stationary conductive support member 74 which contains
a sliding contact member 75 (Figure 4~ ~hich maintains
electrical sliding contact ~ith the conductive tube 71.
A suitable insulation layer 76 (Figure 4) can be fixed
to member 74 to provide relatively lo-~ friction guiding -~
of the movable member 71. Contact 75 is then held in
lS place by a suitable conductive backup plate, such as
plate 77, which is held in place by suitable screws.
Conductive stationary support member 74 is
also provided with an up-~ardly extending conductive
tab 78 l~hich is fixed to member 74 by bolts 79 and 80
(Figure 6) and the tab 78 engages the jaw contact 46
when the device is assembled. The support member 74 is
then fixed to the ring 60 by thrèe insulation support
members 81 and 82 (Figure 6) and 83 (Figure 4~ which
may be molded epoxy members. The right-lland end of each
of these members is bolted to member 74 as by bolts 85,
86 and 87, respectively, and their opposite ends are
bolted to member 60 as by the bolt S8 shown in Figure 4
~lZ89t30
for the case of insulat;oll sul)l)ort mcrl)ber 83. Sil~ilar
~)olts connect the other insulation supports to the
member 60 but are not shown in the drawings. Thus, the
movable contact asscmbly is insulatably suppoTted from
the housing 26
The main movable contact element then consists
of a bulbous movable contact member 90 ~hich is termi-
nated by a plurality of segmcnted contact Iingers 91.
~ ember 90 defines an out~.~ardly looping current
path from the centrally located conductive member 71
and may be suitably electrically connected to the end of
member 71 as by a threaded connection to the intermediate
conductive ring 92 ~hich is, itself, threaded to the
end of member 71. Intermediate member 92 also serves as
a seat for compression spring 93 ~hich is pressed against
the inner diameter of the interior sliding arcing contact
member 95. Arcing contact 95 has a central opening 96 at
its outer diameter and receives a suitable nonconductive
ring 97 ~hich enables member 95 to slide relatively
easily l~ith the fingers 91. Note that the ends of
fingers 91 bend in~ardly to define a shoulder 99 ~ihich
engages the shoulder 100 ~hen the fingers move to the
left ~hile the interrupter is opening.
The stationary contact structure 49 is best
Z5 sho~n in Figures 4 and 8. Stationary contact structure
49 has a main support housing section 110 l~hich may be
of aluminum and has a tab 111 e~tending thelefrom and
~lZ8980
bolted thereto as by the bolts 112 and 113. Tab 111 is
then received by the jaw contact 47 to make connection between
the stationary contact assembly and the terminal bushing 32.
Support member 110 then has three epoxy support
members 114, 115 and 116 bolted thereto as by bolts such
as the bolt 117 shown in Figure 4 for the case of member 114.
The support members 114 to 116 are then in turn bolted to
the aluminum disk 52 as by bolts such as bolt 118 shown in
Figure 4 for the case of member 114. Thus, the entire sta-
tionary contact assembly is insulatably secured from the
main support casing 26.
Member 110 has an intermediate aluminum support
member 120 (Figures 4 and 4b) bolted thereto as by bolts
such as bolt 121 shown in Figure 4 and a main stationary
contact sleeve 122 is threadably connected or otherwise
suitably connected to the member 120. The end of member
122 may have a contact ring insert 123 which may be of a
material which can resist arc erosion, such as copper-
tungsten or the like for receiving the inner ends of
contact fingers 91 of the movable contact when the in-
terrupter is closed, and for forming a good solid low-re-
sistance current conduction path between contact assemblies
48 and 49. Note that fingers 91 are outwardly and elasti-
cally pressed when they engage member 122 to provide high
pressure contact. The end of the contact sleeve 122 is then
terminated by a Teflon (a trade mark) ring 130 which
generally covers the outer end of the stationary contact
assembly and has the generally trapezoidal cross-sectional
shape shown. Ring 130 can be secured in place relative to
sleeve 122 as by threading or the like.
The stationary contact assembly shown in Figure 4
further contains a copper coil support member 140 (see
Figure 4b~ which consists of a central core section 141
- 12 -
~28980
which has a central opening 142 therein, and two integral
spaced flanges 143 and 143a extending from core 141.
Flange 143 acts as an arc runner and is a generally washer
shaped conductive plate which may be of a chromium copper
material. Rear flange 1~3a is preferably slotted to dis-
courage circulating current. Coil support 140 should be
sufficiently strong to withstand forces of repulsion which
tend to repel the coil winding and the arc runner 143. A
Teflon (a trade mark) or other insulation material nut 145
covers the inter;or surface of arc runner 143 and define
an annular shaped exposed contact area for arc runner 143.
Insulation members 148, 149 and 149a are disposed
between copper coil support member 140 and sleeve 122 to
prevent their accidental contact. The space between arc
runner 143 and flange 143a receives a winding 150 which is
a spiral winding, for example, consisting of eleven concen-
tric flat turns which are insulated from one another. If
desired, the turns of winding 150 can be made of other cross-
section shapes,
_ 13 ~
~128980
- 14 -
and could, for example, be s~uare in cross-scction. 'I'he
interiormost coil of winding 150 is electrically
connected to the central hub 141 while the outcrmost
coil of winding 150 is electrically connected to member
120 by the conductive strap 151. Thus, an electrical
connection is formed from terminal 111 (Figure 4) through
member 110, member 120, conductive strap 151, winding
150, and to the hub 141 of member 140. In the embodiment
of Figure 4, current is connected to arc runner 143 at
its interior. Current is introduced into hub 141 from
coil 140, and is then connected directly to the interior
diameter of arc runner 143.
There can be an outside feed of current to arc
runner 143, whereby the outer diameter of flange 143a
is connected to the outer diameter of the arc runner 143.
The current path for either inslde or outside feed to arc
runner 143 is schematically shown in Figure 4a. Suitable
insulation layers are provided as necessary to define the
inside or outside-fed connection to the arc runner 143.
Figure 10, which will be later described, shol-~s the
outside feed in detail.
In the construction described to this point,
it can be seen that the assembly of the interrupter is
simplified by the removable connection between the
movable and stationary contact assemblies 4~ and 49 with
the jaw contacts 46 and 47 for the terminal busllings 31
and 32.
llZ~80
- 15 -
The currcnt ~ath tllrough the interruptcr, ~hen
the interrupteIs are in the closed position sho~n below
the center line in Figure 4, is as follows:
Current enters terminal 31 and flows through
S jaw contac~ 46 and tab 48 and is then connected to the
conductive ~ember 71 through the sliding contact 75.
Current then flows a~ially out-~ardly into movable contact
member 90 and then through the contact fingers 91 and
into contacts 123 and 122. Current then continues to
flow into member 120 and-member 110 and then through the
tab 111 into the jaw contact 47 and then out of the
bushing 32.
In order to open the interrupter contacts, the
operating mechanism causes link 38 to rotate counter-
cloc~ise in Figure 4, thereby mo~ing conductive member
71 to the left. During the initial opening motion, the
contact fingers 91 move to the left in Figure 4 so that
the main contacts open and electrical current flow is
commutated ~rom the main contact into the arcing contact
95, ~hich is still engaged with the arc runner 143, coil
150, and then througll members 120 and 110 to tab 111.
Contact 95 may be of a copper chromium
material or some other material ~ell suited to withstand
arcing duty. The arcing contact 95 is initially strongly
held against the arc runner ]43 under the influence ofthe spring 93. Once the movable contact fingers 91 have
moved sufficicntly far to the ]eft, however, shoulder 99
( ~.Z~3980
- 16 -
of the fingers 91 pick up shoulder 100 of arcing contact
95 and, for the first time, the arcing contact 95 begins
to move to the let, and out of contact with arc runner
143. An arc is then drawn between the arc runner surface
143 to the arcing contact 95 ~hich arc current flows in
series ~ith the coil 150.
The current through coil 150 then sets up a
magnetic field which has a component extending perpendi-
cularly through the arc current flo~ing between arc
1.0 runner 143 and contact 95. At the same time, since
coil 150 is very closely coupled to the arc runner 143
(l~hich is a short-circuited turn), a circulating current
is induced in the arc runner 143. This circulating
current is phase-shifted relative to the arc current and
the current in coil 150. The current in the coil 150
and the circulating current in runner 143 produce a
magnetic field in the arc space, which field has a
component which is perpendicular to the arc current.
The arc current and the magnetic field interact to
produce a.Lorentz force on the arc, thereby causing the
arc to rotate rapidly around the axis of runner 143 and
contact 95. Consequently, the arc spins rapidly through
the relatively stationary dielectric gas, thereby to
cool and deionize the arc so that it will extinguish at
current zero.
Improved operation is obtained when current applied to
the arc runner 143 is app.lied at its outer di~lneter,
~lZ8980
so that a blow-in magnetic force is applied to the arc
current, causing it to bend toward the axis of rotation of
the interrupter.
The effect of the outside feed to the arc runner can
be best understood by a consideration of Figures 10 and 11.
Figure 11 schematically illustrates a few of the disclosed
stationary contact assembly components.
Figure 10 shows the movable contact assembly 48
of Figure 4 along with a stationary contact assembly 49
which is modified for outside feed of current. Thus, in
Figure 10, arc runner 143 is modified to have a cu~ shape,
and has cylindrical wall 200 which extends coaxially over
winding 150, and is threadably engaged to the outer periphery
of flange 143a. Suitable insulation disks 201 and 202
and insulation cylinder 203 insulate coil 150 from cylindrical
wall 200, runner 143 and flange 143a. Insulation sleeve 204
insulates contact sleeve 122 from the conductive wall 200.
Lead 151 is connected to the outermost coil of
winding 150, and its innermost coil is connected to hub 141.
The arc runner 143 is mechanically held closely coupled to
coil 150 by steel bolt 205 which is sheathed with insulation,
such as Teflon (a trade mark) cylinder 206 and Teflon (a
trade mark) cap 207. Bolt 206 presses against plate 208
and insulatibn disk 209 as shown.
.
- 17 -
~lZ8980
- 18 -
Contact ]22 ~n Figure 10 is thread~d onto a
conductive support 210 which, as in Figure 4, is suitably
connccted to member 110 and terminal bushing 32.
It should be noted that flange 143a is slotted
as by slot 211 at one or more places on its perlphery to
avoid inducing a circulating current around flange 143a.
It will be clear from Figure 10 that-the
current path to arc runner 143 will follow the path of
the arrows so that current wlll be connected to runner
143 around its full outer periphery. The effect of thls
outside feed of current is best understood from Figure
11 which schematically shows the arc runneT 143 for
different current feed conditions.
Figure 11 illustrates, by graduated arrows,
lS the magnetic flux density field B plotted across the
pertinent regions of the area through which the arc
between arc runner 143 and mo~able arclng contact 95
will travel. It will first be noted that the intensity
of the magnetic field is greatest closest to the arc
runner 143. This is because the magnetic field B is
produced by t~e circulating current in member 143 and
also by the coil 150 which is disposed behind member 143.
Thus, as the distance from coil 150 and member 143 increases,
the field strength is reduced. At the same ti~ne, the
direction of the field vector yaries over the area and
is seen to be parallel to the interrupteT central axis
at regions along the central axis of member 143 and then
~Z8980
- 19 -
becomes closer to a pcrl)endicular to thc ccntral ~xis of
member 143, progressing radially out~ard from the axis.
The force which is exerted on the arc current
drawn bet~een arc runner 143 and movable arcing contact
95 is given by the vector cross product bet~ecn the
magnetic field B and the arc current. Thus, tlle closer
to perpendicular the arc current is to the field vector,
the greater will be the force tending to rotate the arc
around the annular arc runner area.
If the current coming into arc runner 143 was
straight and parallel to the central axis of runner 143
and in the absence of other disturbing forces, the arc
current would take the path 159. Thus, the arc current
would have a relatively large component perpendicular to
the various field vectors B to produce a rather high
rotating force.
In the prior art, however, current is intro-
duced to the arc runner 143 at the inside diameter of the
arc runner. Thus, current has ta~en the path shown in
the solid line 160. Because of the bend in the current
160, a magnetic blow-off force will be exerted on the
arc current, and the arc current ~ill follo-~ the outwardly
bowed path 161. Because of this, the arc current in the
high field region near the arc runner 143 will be more
parallel to the magnetic field vector B, so that a
relatively low rotating force will be applied to the arc
8980
- 20 -
current. Moreover, the arc 161 is outwardly blo~Jn, thus
leading to the possible danger that the arc will transfer
back to the main contact 122.
In accordance with the invention, the current
feed is to the outside of the arc runner 143, as shown by
the dotted-line path 162 in Figure 11. This then produces
a blow-in or inward magnetic force on the arc, which is
directed tol~ard the axis of the arc runner 143, thereby
to cause an in~ard bo~ing of the arcing current as shown
by the arc current path 163. Note that the maximum
inl~ard bowing occurs closest to the arc runner 143, where
the magnetic field B is the highest. Thus, in these very
high lntensity regions, the arc current is almost
perpendicular to the magnetic field, thus producing
extremely high rotating forces on the arc. ~qoreover, the
arc 163 is blown away from the outside, thereby
minimizing the danger of a flashover to the main contact
members.
The opposite end of the arc root is on the
arcing contact 95 as shown in Figure 11. An important
aspect of the new device is that the current flow through
the arcing contact 95 is radially outward, and over the
dotted-line path 170 rather than the prior art type of
inside feed to the arcing contact, sho~n in the solid
line 171 path.
By causing the current path through the arcing
contact to be an outside feeding path, current in the
~Z8980
- 21 -
moving contact 95 flo~s in the radially out~ard path
from the arc root region and from the axis of the movable
contact, Thus, there is an inward blow-off force applied
to the arc root and to the arc in the region of the
arcing contact 9S. That is to say, the arc l~ill tend to
be moved in~ardly toward the axis of the arcing contact
gS rather than out~ardly, as would occur for an inside
feed along the path 171 as in the prior art. This tends
to maintain arc position on the most radially in-~ard
portion of the arcing contact so that arc position and
arc length is maintained to minimize arc energy input to
the gas and to prevent a flashover to the main contact.,
It was previously pointed out, with respect to
Figures 4 and 6, that the movable contact member 71 had
openings such as openings 72 and 73 therein. OtlleT
openings are also distributed around the left-hand end of
member 71. It has been found that these openings ~
assist in the removal or distribution of arc plasma which
is produced during arcing. Thus, it has been f,ound
desirable to have some means for directing the arc plasma
away from the arc zone during the interruption operation
in order to move the arc plasma away from the main
stationary contact.
By providing openings 72 and 73 or other
similar openings along the lcngth of conductor 71, the
intense heat produced by the plasma in the region bet-~een
the separating contact 9S and runner 143 ~ill act as a
llZ8980
source to cause hot gases to move to thc left alc)rlg the
axis of the tube 71 and t]~en out through the openings of
the tube. That is to say, thc openings, such as
openings 72 and 73, help define a flow channel along the
S ccnter of the moving contact along which the hot gases
can move in order to remove excess hot gases from the
arcing zone.
This is extremely useful at higher current
levels, where large amounts of hot gases are produced.
It also has limited use in connection ~ith lo~ current
interruption where a limited amount of hot gas is
produced. Hol~ever, in the case of low current inter-
ruption, it is useful to provide means for producing a
negative pressure region within contact 71 to permit
movement of at least a limited amount of gas a~ay from
the arc zone. This could be accomplished, for e~ample,
by blocking substantially the full interior of
conductor 71 with a light insulation filler material
and leaving a relatively small gas volume sufficient only
to allo--~ full movement of the arcing-contact 95 to the
right, relative to the movable contact ~hen the contact
opens. This limited movement ~.ill then cause a propor-
tionally large increase in the volume to the left of
contact 95 during opening, thereby to pro~uce a negative
pressure zone into which a limited aTnount of gas could
flol- under lo~ current interruption conditions.
~,~.28980 ~
- 23 -
As previously indicated, and in accord.lnce
~ith the invention, arc runner 143 and other contact
components are preferably made of a chromium copper
a]loy, preferably one having 0.9% chromium by ~eight.
This material has been found to perform ~ell in the high
current arc rotation mode of operation since its
conductivity is 85% that of elec~rolytic copper. In
accordance l~ith the in~ention, this material was also
found to perform about as well as copper tungsten in
the lo~ current, high TR\r frequency mode. Note that
copper tungsten cannot be used for the arc runner since
its resistance is too high for proper operation in the
arc rotation mode.
Figure 12 shol~s test results of an interrupter
of the type shol~n in Figure 10 using a chromium copper
material for arc runner 143 I~hich had 0.9~ by l~eight of
chromium. In Figure 12, the shaded band 200 shol~!s the
boundary of successful operations (in the region to the
left of band 200), ~ith the interrupter using the chromium
Z copper arc runner. By comparison, the dotted line 201
sho~s the boundary of successful operations using an
electrolytic copper arc runner. Auxiliary interruption
means are required for lo~ current, high TR\I frequency as
seen by boundary 201. The dramatic impro~ement of
boundary 200, using the novel chromium copper alloy arc
runner, reduces or completely eliminates the need for
SUC}I auxiliary equipment.
~lZ8980
- 24 -
As pointed out previously, the chromillm copper
arc r~lnner performs almost as well as copper in the arc
TOtation mode, and it performs almost as well as copper
tungsten in the plain break mode. Figure 13 shows the
S res~llts of an experiment comparing copper, copper
tungs~en and chromium copper at low current, high TRV
frequency operation. In carrying out the experiment,
a copper arc runner was used, facing a slotted fixed
contact of the different compositions. A two inch gap
was formed between the arc runner and contact and 15 kV
R.~.S. was placed across the gap and an arc was arti-
ficially initiated. The coil in series with the arc
runner had 7-1/2 turns.
The test results produced the success-failure
boundaries 210, 211 and 212 for copper, chromium copper
(0.9% chromium) and copper tungsten materials,
respectively, for the slotted contact facing the arc
runner. It can be seen that the chromium copper lS
almost as effective as the coppe~ tungsten in the low
current, high TRV frequency range of operation and in
the plain break mode. It is also seen that the chromium
copper is vastly superior to the copper (boundary 210)
in the low current range.
Although a preferred embodiment of this
invention has been described, many variations and modi-
fications will now be apparent to those s~illed in the
ilZ~398(~
- 25 -
art~ and it ;s preferred thercfore that the instant
invention be limited not by the s~ecific disclosure
herein but only by the appended claims.
