Note: Descriptions are shown in the official language in which they were submitted.
WO 91/0822 PCT/US90/05102
-1
~D~j .TT ~~QT_,YMER DEVICE
HA . ~R~ QE T~ INVENTION
F;~~ ~ the Invention
This invention relates to conductive polymer compositions
and strip heaters comprising them, in particular self-regulating
strip heaters which comprise a pair of elongate metal electrodes
embedded in an elongate core of a conductive polymer composition
which exhibits PTC behavior. .
Tntroduct~ on ,~ the 2nvention
Conductive polymer compositions and electrical devices
comprising such compositions are well known. A conductive
polymer composition comprises a polymeric component and,
dispersed or otherwise distributed therein, a particulate
Conductive filler. Strip heaters, particularly self-regulating
strip heaters comprising conductive polymers, are also well-
known. ~In this application, the term strip heater is used to
mean a conductive polymer resistive element into which elongate
electrodes are embedded. In operation, such strip heaters
provide a varying level of heat in response to changes in the
thermal environment. Under normal operating conditions, this
self-regulating feature serves to limit the maximum temperature
which the heater achieves, thus providing reliability and
safety. However, under certain circumstances where the busbars
are exposed by external damage or by faulty installation, and
when the heater is electrically powered and exposed to an
electrolyte, an arc can occur between the electrodes. Unless
the arc is interrupted, the conductive polymer may burn and
could possibly result. One way to minimize this danger is
wo ~no~sz2 ~~) ~ ~ -zw ~cr~usooiosio?
to develop appropriate conductive polymer compositions in
which the polymer itself is flame-retardant or which contain
conventional flame retardant additives to work in conjunc-
tion with the strip heaters. Another method to minimize
risks from arcing faults is to use fuses or other circuit
protectian devices, e.g. arc fault interruptors or ground
fault detectors, as part of the strip heater circuit in
order to remove power from the circuit if an arc should
occur.
SUI~dARY Oh THE INVENTION
I have now found that the presence of a nonconduat,ive
filler in the conductive polymer composition in a strip
heater can reduce the trip tame of a fuse which forms part
of a strip heater circuit, and thus reduce the danger that
the heater will burn and cause damage. In a first aspect,
this invention discloses a strip heater assembly which
comprises
tA) a strip heater which comprises
(1) a resistive element which is composed of a
first conductive polymer composition which
comprises
(a) a polymer,
tb) a particulate conductive filler, and
(c) a particulate nonconductive filler, and
(2) two electrodes which can be connected to a
source of electrical Bower to cause currant
to flow through the resistive element, and
WO 91/03822 PCT/US90/OS102
2~3~~~~~
t8) a fuse,
the particulate nonconductive filler being such that when
the first composition is made into a standard strap heater as
hereinafter defined and the standard heater is tested in a
standard arcing fault test as hereinafter defined, it trips
the fuse in less than 30 seconds.
In a second aspect the invention discaloses a strap heater
assembly which comprises
(A> a strip heater which comprises
(1) a resistive element which is composed of a
conductive polymer composition which
comprises
ta) a polymeric component which comprises
polyethylene,
(b) a particulate conductive filler which
comprises carbon black, and
(c> a particulate nonconductive filler which
comprises Sb203, and
t2) two elongate wire electrodes which are
embedded in the resistive element and which
can be connected to.a source of electrical
Bower to cause current to flow through the
resistive element, and
tB) a fuse which is a very fast acting fuse and which
has a rating of 10A, 125/250V;
the particulate nonconductive filler being such that when
the composition is made into a standard strip heater and the .
WU 91/03$22 ~ ~ ~ ~ ~ ~a " PCf/tJS90/OSi02
standard heater is tested in a standard arcing fault test a,.
trips the fuse in less than 30 seconds.
In a third aspect the invention discloses a strip heater
circuit which comprises
tA) a strip heater which comprises
t11 a resistive element which is composed of a
conductive polymer composition which
comprises
(a) a polymer,
(b).a particulate conductive filler, and
tc) a particulate nonconductive filler, and
(2) two electrodes which can be connected to a
source of electrical power to pause current
to flow through the resistive element,
(B) a fuse. and
(~) a power supply,
the particulate nonconductive filler being such that when
the composition is made into a standard strip heater and the
standard heater is tested in a standard arcing fault test it
trips the fuse in less than 30 seconds.
The invention further includes, in a fourth aspect, strip
heaters whfch are useful in the assemblies and circuit defined
above and are novel in their own right, namely, a strip heater
which comprises a first conductive polymer composition
comprising
WO 91/03822 -5- PCflUS90105102
~~~~25~
(1) a polymer,
(2) a particulate conductive filler, and
t3> a particulate nonconductive filler
and which
(a) when tested following the procedure of UL VW-l,
has a performance which is similar to that of a
second heater made from a second conductive
polymer composition which is the same as the first
composition except that it does not comprise the
particulate nonconductive filler and
(b> when. tested fn a standard arcing fault test
(i) trips the fuse in less time than is required
by the second heater, and
(ii> trips the fuse in less than 30 seconds.
In a fifth aspect the invention discloses a strip heater
which comprises a first conductive polymer composition
comprising
(1) a polymer, '
(2) a partieulate conductive filler, and
(3) a particulate nonconductive filler
and which
(a) when tested following the procedure of UL VW-l,
does not pass the test= and
WO 91 /03822 PCT/US90/OS102
~~'~~~~~ °~-
(b) when tested in a standard arcing fault test
(i) trips the fuse in less time than is required
by a second heater made from a second conduc-
tive polymer composition which as the same as
the first composition except that it does not
comprise the particulate nonconductive
filler, and
(ii) trips the fuse in less than 30 seconds.
The invention further includes, in a sixth aspect, con-
ductive polymers which are useful in the assemblies, circuit
and strip heaters defined above and are useful in their own
right, namely a melt-extrudable first conductive polymer
composition which comprises
(1) a polymer,
(2) a particulate conductive filler, and
(3) a particulate nonconductive filler
said first composition being such that when the ffrst
composition is made into a standard strip heater
(i) when the standard heater is tested following the
procedure of UL test VW-1 its performance is
similar to a second heater which is made from a
second conductive polymer composition which is the
same as the first composition...,,except that it does
not comprise the particulate nonconductive filler,
and
(ii) when the standard heater is tested in a standard
arcing fault test (a) the time it requires to trip
WO 91 /03822 _ ~ _ PCTlUS90/05102
.
a fuse is less than the time required to trip a
fuse for the second heater, and (b) it trips the
fuse in less than 3() seconds.
In a seventh aspect the invention describes a melt-
extrudable first conductive polymer composition which
comprises
tl) a polymer,
(2) a particulate conductive filler, and
(3) 3 particulate nonconductive filler
said first composition being such that when the first
composition is made into a standard strip heater
(i) when the standard heater is tested following the
procedure of UL test VW~1 it does not pass the
test, and
(ii) when the standard heater is tested in a standard
arcing fault test (a> the time it requires to trip
a fuse is less than the time required to trip a
fuse for a second heater which is made from a
second conductive polymer composition which is the
same as the first composition except that it does
not comprise the particulate nonconductive filler,
and (b) it trips the fuse~in less than 30 seconds.
BRIEF DESCRIFTION OF T)3E DRAWING
Figure 1 is a cross-sectional view of a standard strip
heater of the inventionP
Figure 2 is a top view of a strip heater of the
invention; and
WO 91/03822 PCf/US90/05102
~0~6254
Figure 3 is a cross-sectional view of a strip heater along
line 3-3 of Figure 2.
DETAILED ~ESCATPTT_ON ~ ~, ,~N_y~N_~LON
The first conductive polymer composition of this invention
comprises a polymer which may be an organic polymer (such term
being used to include siloxanes), preferably a crystalline
organic polymer, an amorphous thermoplastic po:Lymer (such as
polycarbonate or polystyrene), an elastomer (such as
palybutadiene or ethylenelpropylene/diene (EPDM) polymer), ar a
blend comprising at least one of these. Suitable crystalline
polymers include polymers of one or more olefins, particularly
polyethylene; copolymers of at least one olefin and at least one
monomer copolymerisable therewith such as ethylene/acrylic acid,
ethylene/ethyl acrylate, and ethylene/vinyl acetate copolymers;
melt-shapeable fluoropolymers such as polyvinylidene fluoride .
and ethylene tetrafluoroethylene; and blends of two or more such
crystalline polymers. Suitable polymers and compositions
comprising them may be found in U.S. Patent Nos. 4,188,276,
4,237,441, 4,388,607, 9,470,898, 4,514,620, 4,534,889,
4,560,498, 4,591,700, 4,624,990, 4,658,121, 4,774,024 and
4,775,7781 and European Patent Publication Nos. 38,713, 38,728,
74,281, 197,759 and 231,068.
Crystalline polymers are particularly preferred, although
not required, when it is desired that the composition exhibit
PTC (positive temperature coefficient) behavior. The term "PTC
behavior" is used in this specifi-
CVO 9t/03822 PCTlUS9Ul05102
9 ~~~~°~~~
ca n on to denote a composition or an electrical device which
has an Rlq value of at least 2.5 or an 8100 value of at
least 10, and preferably both, and particularly one which
has an R30 value of at least 6, where Rl~ is the ratio of
the resistivities at the end and the beginning of a 14°C
range, 8100 is the ratio of the resistivities at the end and
the beginning of a 100°C range, and R30 is the ratio of the
resistivities at the end and the beginning of a 30°C range.
The composition also comprises a particulate conductive
filler which is dispersed or otherwise distributed in the
polymer. The particulate conductive filler may be, for
examgle, carbon black, graphite, metal, metal oxide, or a
combination of these. Alternatively, the conductive filler
may itself comprise a conductive polymer in which a par-
ticulate conductive filler is distributed in a polymer
matrix and the matrix is then ground into particles before
being dispersed in another polymeric matrix. The par-
ticulate conductive filler is present in the composition in
an amount suitable for achieving the desired resistivity,
normally 5 to 50% by weight of the comgosition, preferably
to 40% by weight, particularly 15 to 30% by weight.
The particulate~nonconductive filler comprises a
material which is electrically insulating, i.e.,has a
resistivity of greater than 1 x 109 ohm-cm. Preferably the
nonconductive filler. has a melting temperature of less than
1000°C. Suitable materials include metal oxides which are
easily reduced, e.g. Sb203, Pb02, H203, Mo03, and HiZ03. In
this application, easily reduced means that the material has
a reduction potential of less thaai +0.5 volts, preferably
less than +0~.4 volts,, particularly less than +0.375 volts.
Particularly preferred is Sb203. For ease of dispersion in
WO 91/038ZZ PCT/~590/0510Z
~~Db~~~4
-lo-
the polymer matrix, the filler is preferably in the form of
particles which have a particle size of 0.01 to 50 ~tm,
particularly 0.05 to 50 ~Lm, especially 0.10 to 10 Vim. The
nonconductive filler may be single material or it may comprise a
blend of metal oxides or a metal oxide and another particulate
filler. Although a blend of Sbz03 and decabromodiphenyloxide
(also known as decabromodiphenylether), DBDPO, is commonly used
as a flame retardant package in polymers, the presence of the
DBDPO or any other halogenated material is not necessary for
satisfactory performance in the compositions of the invention.
The conductive polymer composition may also comprise inert
fillers, antioxidants, prorads, stabilizers, dispersing agents,
or other components. Mixing is preferably effected by melt-
processing, e.g. melt-extrusion. Subsequent processing steps
may include extrusion, molding, or another procedure in order to
form and shape the composition. The composition may be
crosslinked by irradiation or chemical means.
The conductive polymer composition may be used in any
current carrying electrical device, e.g. a circuit protection
device, a sensor, or, most commonly, a heater. The heater may
be in the form of either a strip or a laminar sheet in which the
resistive element comprises the composition of the invention.
Strip heaters may be of any cross-section, e.g. rectangular,
elliptical, or dumbell ("dogbone"). Appropriate electrodes,
suitable for connection to a source of electrical power, are
selected depending on the shape of the electrica-1 device.
Electrodes may comprise metal wires or braid, e.g. far
attachment to or embedment into the conductive polymer, or they
may comprise
wo ~no3azz ~ ~ ~ ~ ~ ~ ~ Pcrius9oiosioz
-11-
metal sheet, metal mesh, conductive te.g. metal- or carbon-
filled) paint, or other suitable materials.
In order to provide environmental protection and
electrical insulation, it is common far the resistive
element to be covered by a dielectric layer, e.g. a
polymeric jacket (fox strip heaters) or an epoxy layer (for
circuit protection devices). The dielectric layer may
comprise flame retardants or other fillers. For some strip
heater applications, a metallic grounding braid is present
over the dielectric layer in order to provide physical
reinforcement and a means of electrically grounding the
strip heater.
The compositions of this invention are particularly
useful when, in the form of strip heaters, they are used
in conjunction with a fuse and act to "trip" the fuse faster
than strip heaters comprising conventional materials. A
fuse °'trips' when the current in the circuit comprising the
fuse exceeds the rated value of the fuse. Fuses are
categorized based on their vverloa~d fusing characteristics,
i.e. the relationship between the value of current through
the fuse and the time for the fuse to open as described in
Bulletin SFH, "Boas Small Dimension Fuses', l~lsy 1985, the
disclosure of which is incorporated herein by reference. Of
the mayor categories (slow blowing, non-delay, and very fast
acting?) it is. very fast acting fuses which are most useful
in this invention) These fuses have little, if any, inters-
tional delay in the overload region. Although the selection
of a specific fuse is dependent on the normal operating con-
ditions of t~~ stri~a heater and the anticipated fault con-
ditions, fuses which are particularly preferred are very
fast-acting ceramic ferrule fuses with a current rating of
WO 91103822 ° 12 ° P~d'llJS90105102
ampe '~g~~ ~~~~ ~ oltage rating of 125/250 volts . Such
fuses are available, for examgle, from the Hussman Division
of Cooper Industries under the name Huss GHB°-10. The fuse
may be an independent component in the circuit or it may be
in a fused plug assembly, i.e. an assembly in which the fuse
is part of the plug which connects the strip heater to the
power source, e.g, an outlet or a power supply.
Strip heaters of the invention are commonly used in a
strip heater assembly which comprises the strip heater and a
fuse. , Alternatively, the strip heater is a component of a
strig heater circuit which comprises the strip heater, a
power supply, and a fuse. The power supply can be any
suitable souree of power including portable power supplies
and mains power sources. Other components, such.as
resistors, thermostats, and indicating lights, may also be
present in the circuit.
In this specification, a "standard strip heater" is
defined for testing gurposes. A "standard strip heater" is
one in which a conductive polymer composition is melt-
extruded around two 22 AWG stranded nickel/copper wires to
groduce a strip heater of flat, elliptical shape as shown 'in
Figure 1. The heater has an electrode spacing of 0.10 inch ~..
(0.25 cm) from the center of one electrode to the center of
the second electrode. The thickness of the heater at a
point centered between the electrodes is 0.08 inch (0.20
cm). The heater is jacketed with a composition which
containw 31.9 by weight of a standard flame retardant
package as described in Example 1. The jacket is 0.030 inch
(0.076 cm) thick.
The standard strip heater is tested by means of a
"standard arcing fault test". In this test (which is more
WO X1/03822 -13~ PCT/US90105102
fully described in Example 1), a standard strip heater is
connected in a circuit to a power supply and a 10A, 125/250v
fuse. An arc is initiated between two exposed electrodes of
the heater and the time to interrupt the current and '
extinguish the arc by means of tripping the fuse is
recorded. I have found that a standard strip heater which
comprises the composition of the invention ti. e. a first
conductive polymer composition) trips the fuse faster than a
second strip heater which comprises a second conductive
polymer composition, i.e..a composition which is the same as
the first composition except that it does not comprise the
nonconductive particulate filler. The time to trip a fuse
for-the standard heater generally will be at least two times
as fast, preferably at least three times as fast, gar-
ticularly at least five times as fast, e.g. five to eight
times as fast as the second heater. Thus the standard
heater will trig the fuse in at most half the time required
to trip the fuse in a circuit which comprises a second
heater. When tested in the standard arcing fault test, a
standard strip heater of the invention normally will trip
the fuse in less than 30 seconds, preferably in less than 25
seconds, particularly in less than 20 seconds, e.g. in 5 to
seconds. 14n additional aspect of the invention is that
the addition of the nonconductive particulate filler results
in an increase is the number of current spikes observed
during the arcing fault test. Even if the amplitude of the
spikes is similar for both types of heaters, there generally
will be at least.2 times, greferably at least 3 times, par-
ticularly at least 4 times as many current spikes in a given
period, e.g. 30 seconds, fox the heater comprising the first
composition., .
A second test which is conducted on heaters comprising
the first composition of the invention is the UL VW-1
WO 91/03822 PCT/US90/05102
-14-
vertical-wire flame test (Reference Standard for Electrical
Wires, Cables, and Flexible Cords, UL 1581, No. 1080, August 15,
1983. In this test, a heater sample is held in a vertical.
position while a flame is applied. In order to pass the test,
the sample cannot "flame" longer than 60 seconds following any
of five 15-second applications of the test flame. The period
between sequential applications of the test flame is either 15
seconds (if the sample ceases flaming within 15 seconds) or the
duration of the sample flaming time if the flaming lasts longer
than 15 seconds. In addition, combustible materials in the
vicinity of the sample cannot be ignited by the sample during
the test. In this specification, when the performance in this
test of the heater of the invention is said to be "similar" to
that of a second heater which comprises a second conductive .
polymer composition, it means that if ten different samples of
the standard heater are tested, eight of them (i.e. 80~) must
have the same result (i.e. pass or fail) as ten samples of the
second composition.
The invention is illustrated by the drawing in which Figure '
1 shows a cross-section of a standard strip heater 1.
Electrodes 5, 7 are embedded in the first conductive polymer
composition 3 (the resistive element). A polymeric jacket 9
surrounds the heater core. Figure 2 shows a top view of strip
heater 1 which has been prepared for the arcing fault test
described below. A V-shaped notch 11 is cut through the
polymeric jacket 9 and the conductive polymer composition 3 on
one surface of the heater in order to expose electrodes 5 and 7. '
The cross-sectional view~oF the heater along line 3-3 is shown
in Figure 3. Electrodes 5, 7 remain partially embedded in the
conductive polymer 3.
!VU '~ 1 /03822 ~ ~ ~ ~ ~ ~ (~ PCf/US90/05102
_15-
The invention is illustrated by the following examples.
Example 1 (Comparative Example)
The ingredients listed in Table I were preblended and
then mixed in a co-rotating twin-screw extruder to form
pellets. The pelletized composition was extruded through a
1.5 inch (3.8 cm> extruder around two 22 AWG stranded
nickel/copper wires to produce a strip hE=_ater. The heater
had an electrode spacing of 0.106 inch (0.269 cm) from
center-to-center and a thickness of 0.08;i inch (0.211 cm) at
a center point between the wires, The heaster was jacketed
with a 0.030 inch (0.076 cm) layer of a composition
containing 10% by weight ethylene/vinyl acetate copolymer
(EVA), 36.8% medium density polyethylene, 10.3% ethylene/
propylene rubber, 23.4% decabromodiphenyloxide, 8.5% ; ,
antimony oxide, 9.4% talc, 1.0% magnesium oxide, and 0.7%
antioxidant.
The heater was tested using the standard arcing fault
test described below. The results are shown in Table II.
In a related test, the amplitude and frequency of the
current spikes produeed when a heater was tested following
the procedure of the arcing fault test but without the use
of a fuse were recorded. In this modified arcing fault
test, the samples were allowed to burn for three minutes
after a flame was initiated. The results are shown in
Table III.
The heater was tested following the procedures of the
UL VW-1 vertical-wire flame test (Reference Standard for
Electrical Wires, Cables, and Flexible Cords, UL 1581, No.
1080, August 15, 1983). Of the 10 samples tested, five
passed the test. These results are shown in Table Iv.
WO 91/03822 PCT/U590l05102 ,
-16-
Stanriar~3 Arc-i_t1g Fc~Wt- T .S .
A standard, jacketed 25 inch- (64 cm-) long strip heater.
was prepared by stripping one inch (2.5 cm) of jacket and core
material from a first end to expose the two electrodes. A
transverse v-shaped notch was cut half-way through the thickness
of the heater 2 inches (5.1 cm) from the second end and the
jacket and core polymer were removed from the top half in order
to expose part of each of the two electrodes. The electrodes at
the first end were connected in a circuit in series with a
120V/lOOA power supply, a contactor relay, a 0.1 ohm/100 watt
shunt resistor, and a 10A, 125/250V very fast acting fuse (Buss
GBBTM-20, available from the Bussman Division of Cooper
Industries). A chart recorder was connected across the shunt
resistor in order to measure the voltage drop. When the relay
was closed, the sample was powered. A sufficient quantity of 10
to 20~ saline solution was applied to the exposed v-notch until
an arcing fault was initiated. The chart recorder was monitored
until the current was interrupted and the arc was extinguished
(i.e. until the fuse tripped). Both the time duration of the
arc, as determined from the current spikes on the chart, and the .
distance of arc fault propagation on the strip heater were
measured. In some instances, the number of current spikes
present during the arcing fault was also determined.
Fxa p,l es 2 to 6
For each example, pellets of the composition of Example 1
were preblended with the inorganic materials in the proportions
shown in Table I. After mixing in a co-rotating twin screw
extruder and pelletizing, the
WO 91 /03822 PCTf 0590/05102
-17-
compositions were extruded to form strip heaters with the
same geometry as that of Example 1 and were jacketed as in
Example 1. The results of the arcing fault test and the
vertical flame test are shown in Tables II and IV. It is
apparent that those compositions which <:ontain Sb203 have
significantly faster trip times in the atrc fault test than
comparable materials which do not contain the filler.
A strip heater formed from the composition of Example 2
was also tested following the modified arcing fault test
described in Example 1. As shown in the results in Table
III, the amplitude of the current spikes and the burn rate
were comparable for bath the conventional eamposition
(Example l> and the composition of the invention (Examgle
Zl. The major difference occurred in the frequency of the
current spikes; the spikes were much more prevalent for the
composition of the invention than for the conventional
material.
Example 7
Following the grocedure of Example 1, the ingredients
listed in Table I were preblended, mixed in a co-rotating
twin screw extruder, and pelletized. The pellets were
extruded over two 16 AWG 19-strand nickel-coated copper wire
electrodes to produce a strip heater with a wise spacing of
0.285 inch (0.724 cm) center-to-center and a thickness of
0.057 inch (0.145 cm) at a position intermediate to the
electrodes. The heater was jacketed with the same material
as in Example 1. The results of testing are shown in Tables
II and IV.
WO 91/03822 -18- PCT/US90/05102
Exam 1e
Pellets of the composition of Example 7 were blended
with 11.71 by weight decabromodiphenyloxide and A.3~ Sb203
before extrusion into pellets. The pellets were extruded to
~orm a strip heater as in Example 7. The results of testing
are shown in Tables II and IV.
wo m/o3sz? PCT/US90/OSlo2
2~~~25~
-19-
Table I
CONDUCTIVE POLYMER FORMULATIONS
(Components in Percent by Weight)
~mL~an -n _., i 2 3 4 5 6 7 8
EEA 51.7 43.4 49.6 47.5 43.4 35.2 29.3 24.6
CB 30.3 25.5 29.1 27.9 25.5 20.6 17.2 14.5
MDPE 17.2 14.4 16.5 15.8 14.4 11.7
HDPE 32.4 27.2
Antioxidant 0.8 0.7 0.8 0.8 0.7 0.5 0.5 0.4
Sbp03 4.3 4.0 8.0 4.3 '
Zn0 20.0 16.8
A1203 3HZ0 16.0 32.0
DBDPO 11,7 11.7
Process Aid 0.6 0.5
Notes to Table I:
EEA is ethylene/ethyl acrylate copolymer.
CB is carbon black with a particle size of 28 nm.
MDPE is medium density polyethylene.
HDPE is high density polyethylene.
Antioxidant is an oligomer of 4,4-thio bis(3-methyl 1-6-t-butyl phenol)
with an average degree of polymerisation of 3 to 4, as described in U.S.
Patent No. 3.986,981.
Sb203 is antimony trioxide with a particle size of 1.0 to 1.8 dun.
2n0 is zinc oxide with a particle size of 0.15 /,tm.
A1z03 3HZ0 is alumina trihydrate with a particle size of 0.15 ~IZn.
DBDPO is decabromodiphenyl oxide (also known as decabromodiphenylether).
WO 91/03822 PCT/US40/05102
_20_
~~~~15~ ~a~le
II
P.I2CING FA ULT RESULTS
TEST
Circuit Fuse Turn Hurn
Length ResponseLength Rate
Example (feet) (seconds) (in min)
(i.nches)
1 2 97 2.1 1.30
100 180 4.3 1.43
2 2 6.9 0 --
50 9.4 0 __
100 19 0.3 0:94
3 2 9 0 __
4 2 6 0 __
2 60 1.1 1.10
100 159 3.0 1.13
6 Z 40 0.8 1.20
100 * 5.0 -_
7 2 74 Z.5 1.22
8 2 18 0.2 0.67
*The test was discontinuedafter minutes, eventhough the
5
fuse did not trap.
WO 91/03822 PCT/US90/05102
_21_
Table III ~~~~~~~
MODIFIED ARCING FAULT TEST RESDLTS
Amplitude Freduency
Circuit of Current of Cua:rent burn
Length Spikes Spi)ees Rate
Example ( feet ) f a~ ) ( ~k/0 .5 min ) ( in min )
1 2 31 - 71 8 2.06
50 8 - 41 1(i 2.08
100 5 - 21 3~1 2.52
2 2 27 - 100 2fi ~ I.83
50 6 - 40 . 63 2.00
100 4 - 30 88 2.34
Table IV
VERTICAL i~IRE FLAME TEST (UL VW-1)
Example ~ Pass
1 50~
2 100
3 100
4 100
7 100
8 100
