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Патент USA US3075172

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atcnt o ‘all’,
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Jan. 22, lbdg
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or
$31
$375,162
Arthur A. Schupp, in, La .l'olla,
Harold
Forsen,
den Blego, l'lalih, assignors to General Dy “L. :QS
t-Jor
porn-‘ion, New York, NSiL, a corporatii n o Delaware
Flled that. 2.6, 196d, Set". Isle. 65,tl2 GA
2 ?airns. (Cl. 33§-~2%®)
The present invention relates to resistors and more
the magnetic forces tending to move the sections l2 apart
become greater.
The number of folds in the ribbon it) depends upon
the desired physical size of the resistor, and the length
of the ribbon Zlti. In the illustrated embodiment, the
ribbon to is folded seven times to form four sets of
parallel sections 12.
Disposed between the folded sections 12 of the rib
are spacers or strips 1d of hard, heat resistant
particularly to low inductance resistors having a pulsed 10 bon
insulating material, such as phenolic impregnated canvas.
current capacity above about 1,090 ainperes.
The spacers lid, in addition to serving as insulation be
Presently available low inductance resistors have been
tween the adiacent sections 12 serve as backing mem
designed for relatively low current. When such a resistor
bers for the sections 12.
design has been employed to construct a resistor for high
in order to increase the electrical creep path between
currents, especially greater than 1,000 amperes, the re
the section 32, the spacers
are made wider than the
sulting resistor has been torn apart by the magnetic
ribbon
and are transversely staggered as shown in
forces developed in the resistor and/or has been heated
FIGURE 3. The spacers M are made longer than the
to such a high temperature that the resistor has burned
out.
sections 12 and, as shown in FIGURE 2, end spacers to,
An object of the present invention is the provision of 20 which are short lengths of the insulatin‘r material, are
a low inductance resistor having a pulsed current capac
ity of over about 1,060 arnperes. Another object of the
invention is the provision of a low inductance resistor
which has a relatively long life with current pulses of over
LOllO arnpercs. Still another object is the provision of
a low inductance high current resistor which is durable
in use and inexpensive to manufacture
disposed between the outwardly extending longitudinal
ends of the spacers 16 in abutting relation 1 'p with the
interconnecting portions 13, whereby the interconnect
ing portions 13 are retained in position.
Electrical connections are made to the
of the rib
bon lb through a pair of spaced apart L-shaped terminal
blocks
and
of conductive material, the correspond
Various other objects and advantages of the present
invention will become apparent by reference to the fol
ing legs of which are in parallel relationship. The ter
lowing description and accompanying drawings.
sheet
of suitable insulation, such as silicone rubber.
The sheet 24 is extended beyond the boundaries or" the
terminal
and between spacers ‘id to increase the elec
trical creep path between the terminals 2t’; and 22. The
ends of the ribbon it? are connected to the inwardly fac
ing mat‘ .-al portions of the shorter legs 26 and 2% of the
in the drawings:
PEGURE l is a perspective view of a low inductance
high current resistor constructed in accordance with the
present invention.
FIGURE 2 is an enlarged side View of the resistor
shown in FlGURE 1; and
FEGURE 3 is a cross sectional view taken generally
along line 3—3 of FIGURE 2.
in accordance with the present invention a low in
ductance resistor is provided which has a pulsed cur
rni
terminals
and 2,2 are insulated from each other by a
and 22, respectively, by suitable means,
such as hard solder.
Means are provided on each of the longer legs 34}
and 32 of the terminals 2%‘ and 22, respectively, for at~
taching
electrical cable (not shown) thereto.
in
the illustrated embodiment, the attaching means for ter
minal 2e includes an internally threaded tubular con
duit 3d suitably connected at right angles to the longer
tive material which is bent back upon itself so as to form
leg 35) thereof. The attaching means for terminal 22 in
a pair of spaced apart, coextensively extending folded
back sections. A spacer of insulating material is dis 45 cludes an internally threaded tubular conduit 36 which
in suitably connected to tan o?set portion 33 of the leg
posed between the folded back sections of the ribbon and
rent capacity above approximately 1,000 amperes. Gen
orally the resistor comprises an elongated ribbon of resis
32 of the terminal 22.
an element of insulating material is disposed on the out
wardly facing surface of each section. Means are pro
vided for clamping the spacer, the folded back sections
Elongated rectangular elements or side forms
and
d2; of hard, heat resistant insulating material such as
metal (an alloy of 43% nickel and the balance copper),
minals 2t) and 22 by suitable means such as screws 4:13
and the elements together with a pressure such that the 50 phenolic impregnated paper are provided on the out
wardly facing surfaces of the folded ribbon ill‘. The
frictional force on the sections is greater than the force
ends of the elements
and d2 are provided with suit
due to t‘ errnal expansion of the sections.
able recesses ed and 46, which respectively receive the
More speci?cally, the resistor illustrated in the draw
shorter legs 26 and 28 of the terminals 2d and 2.2. The
ing includes an elongated ribbon lid of resistance mate
are respectively attached to the ter
rial, such as stainless steel, Nichrome, Monel, Advance 55 elements lit} and
threadedly engaged with the terminals
and 22.
When
a
high
current
is
passed
through
the
ribbon lit,
and length which depend upon the resistance and in
the magnetic pressure forces the ribbon
into any
ductance desired.
The ribbon lit} is folded over on itself through a series 60 voids existing adjacent the ribbon id, that is, voids in
etc.
The ribbon it} is made of a cross sectional area
of alternately reverse bends extending across the width
f the ribbon so as to provide an even number of spaced
apart, coextensively extending parallel sections or folds
l2 interconnected by portions 13. In this way, the mag
netic ?eld energy produced by the current flowing through
one section 12 is substantially reduced by the magnetic
?eld produced by the oppositely directed current in the
other section 32 of the pair. Accordingly, a low in
ductance results. The closer the spacing etween the
sections 12 the lower is the inductance of the resistor.
However, as the sections 1’? are spaced closer together,
the spacers id and lo, and in the side forms 4d and 4E2,
and results in tearing of ‘the ribbon ltl. In the illus
trated embodiment, such voids occur at the separations
(indicated by the reference numeral 5r‘) existing between
the ends ‘or’ the terminals 2d and 22 and the recesses 44
and 45. To prevent tearing of the ribbon lit), the voids
5t? are ?lled with a hard insulating material, such as
epoxy resin.
The sections 12 of the ribbon lit, the spacers
and
lie and the side forms as and 42 are clamped together
by suitable clamping means 51?, which in the illustrated
embodiment, includes a plurality of transversely extend
3,075,182
41.
"a
ing, longitudinally spaced apart clamps. Each of the
clamps 52 includes a pair of steel channels 54 and 56,
respectively disposed on the outwardly facing surfaces of
the side forms lid and 42. The channels 54 and as are
connected together by bolts 53 and so extending through
the ends of the channels 54i and 56.
In the illustrated
embodiment, each of the bolts 58 and so is provided with
in uniform fashion to provide a plurality of coextensive
parallelly arranged planar segments that are spaced apart
and joined by folded end sections, a plurality of insulat
ing spacers, one each of said insulating spacers being
disposed between each pair of adjacent ones of said
coextensive parallelly arranged planar segments of said
strip, a plurality of insulating elements, one each of said
insulating elements covering the exposed surface of each
of said folded end sections of said strip, a pair of termi
When a high current is passed through the ribbon 10,
the ribbon tends to lengthen due to the heat developed 10 nal blocks, a ?rst of said terminal blocks being elec
trically connected to one end of said strip of resistive
therein by the current. This lengthening of the ribbon
material and a second of said terminal blocks being elec
lid, if not restrained, will eventually tear the ribbon apart.
trically connected to ‘the other end of said strip, a pair
To prevent such lengthening the clamps $2 are spaced
a nut 62 and washer 64-.
of side forms positioned along oppositely disposed planar
along the side forms as and
at such a distance and
are maintained under such a pressure by the bolts 58 and 15 segments of said strip of resistive material and adjacent
the connection of the ends of said strip with said terminal
do that the frictional force on the ribbon lid‘ is greater
blocks, a plurality of clamps spaced along the longitudinal
than the force due to thermal expansion ‘of the ribbon 10‘.
axis of each of said side forms for clamping said side
The necessary clamping pressure may be determined
forms, spacers, insulating elements, and planar sections
by ?rst calculating the temperature rise of the ribbon
it) assuming that all the energy supplied to the resistor is 20 of said strip of resistive material together with a pressure
such that the frictional force on said planar segments
dissipated in the ribbon in a very short time. Using this
and folded end sections of said strip is greater than the
temperature rise, the elongation of the ribbon may be
force imparted thereto due to thermal expansion result
calculated, and then using Young’s modulus of elasticity
ing from the passage of current therethrcugh, and in
for the material of the ribbon, the lengthwise pressure
sulating means for ?lling voids existing in the clamped
may be calculated. The lengthwise force is then found
together structure to prevent the possibility ‘of said strip
by multiplying the pressure by the cross-sectional area
of resistive material being severed due to the action of
of the ribbon. The necessary clamping force is then cal
magnetic
pressure forces thereon while current is passed
culated by dividing the lengthwise force in the ribbon by
therethrough from said ?rst terminal to said second
the coe?icient of friction between the material of the rib
terminal.
bon ‘and the material of the spacers l4» and 16 and of the
side forms 40 and 42.
in one embodiment of a low inductance resistor, the
ribbon is made of an alloy of 43% nickel and the bal
ance copper. The ribbon is 1.125 inches Wide and 0.004
inch thick and is approximately 12 feet long. The ribbon
is folded 7 times and 1/32 inch phenolic impregnated can
vas spacers are disposed between the folds of the ribbon.
The side forms are 1/2 inch thick phenolic impregnated ‘
2. A low inductance resistor having a pulsed current
capacity greater than 1000 amperes, which resistor com
prises a strip of resistive material folded back upon itself
in uniform fashion to provide a plurality of coextensive
parallelly arranged planar segments that are spaced apart
and joined by folded end sections, a plurality of insulating
spacers, one each of said insulating spacers being disposed
between each pair. of adjacent ones of said‘coextensive
parailelly arranged planar segments of said strip and
paper. The unit is clamped together by 1/2 x 1 inch steel
channels, which are tied together by 1A" bolts. The chan 40 extending beyond the edges thereof, a plurality of in
sulating elements, one each of said insulating elements
nels are spaced approximately every 2 inches along the
covering the exposed surface of each of said folded end
length of the resistor and the clamping force on the rib
sections of said strip, a pair of terminal blocks, a ?rst
bon is equal to about 100 lbs. per bolt.
‘ '
of
said terminal blocks being electrically connected to
The above resistor has an inductance of less than 0.05
one end of said strip of resistive material and a second
microhenry and a resistance of 0.6 ohm. The resistor
of said terminal blocks being electrically connected to
may be pulsed over 3,000 times at one minute intervals
the other end of said strip, a pair of side forms positioned
with 20,000 ampere pulses which last for 5 microseconds
along oppositely disposed planar segments of said strip
Without adversely affecting the structure of the resistor.
of resistive material and adjacent the connection of the
The temperature inside the resistor during such an opera
tion is about 300° F. The temperature at the surface of 50 ends of said strip with said terminal blocks, a plurality
of clamps spaced along the longitudinal axis of each of
the resistor is about 200° F.
said side forms for clamping said side forms, spacers,
As can be seen from the above a resistor construction
insulating elements, and planar sections of said strip of
is provided which has a very low inductance and a high
resistive material together with a pressure such that the
current capacity. The reason the resistor can Withstand
high cur-rents is that the clamping pressure on the side 55 frictional force on said planar segments and folded end
sections of said strip is greater than the force imparted
forms is large enough so that the frictional force on the
thereto
due to thermal expansion resulting from the pas
ibbon is greater than the forces due to thermal expan;
sage of current therethrough, and insulating means for
sion of the ribbon. Another reason is that all voids into
?lling voids existing in the clamped together structure
which the magnetic pressure would force and tear the rib
60
to prevent the possibility of said strip of resistive mate
bon are ?lled with hard material. Moreover, the folded
rial being severed due to the action of magnetic pressure
sections of the ribbon extend coextensively and therefore
forces thereon while current is passed therethrough from
the sidewise magnetic pressure on the ribbon is small.
said ?rst terminal to said second terminal.
Various changes and modi?cations may be made in the
above described low inductance, high current resistor with
References fitted in the ?le of this patent
out departing from the spirit or scope of thepresent inven 65
UNITED STATES i’ATENTS
tion. Various features of the invention are set forth in the
accompanying claims.
What is claimed is:
.
l. A low inductance resistor having avpulsed current
capacity greater than 1000 amperes, which resistor com 70
prises a strip of resistive material folded back upon itself
560,588
677,941
Leonard ______________ __ May 19, 1896
Case _________________ __ July 9, 1901
1,687,677
Little _______________ __ Oct. 16, 1928
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