Note: Descriptions are shown in the official language in which they were submitted.
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41PR06674
INSULATED ELECTRICAL POWER
DIsTRIsuTIoN suswAy TABS
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BACKGROUND OF THE INVENTION
Electric power busway used within industrial
power distribution systems generally consist of a
plurality of rectangular copper or alumimlm bars
; 5 closely spaced and separated by means of an
electrically insulative coating. Every two feet or
so, the bars are shaped to provide a spaced gap
between the indlvidual bars and the bottom edge of
each of the bars is abraded to remove the insulative
material and expose a contact region on both flat
sides of the bar. This exposed contact is then tin or
silver-plated to provide an electric contact blade for
connection with a power take-off assembly which
includes a corresponding plurality of blade receiver
stabs which mate with the blade portions of the shaped
bars. The air gaps between the shaped bars provide
sufficient electrical insulative spacing to prevent
arcing between~the different phases of a multi-phase
power~system wherein each bar carries one-phase of the
system current. The so called "expanded connector
region" containing the shaped bars effectively provide
electrical access to the busway by means of the
contact blades. When a four-bus power distribution
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system is employed, the added length for each expanded
connector region corresponds to an increase of
approximately six percent for each bar. For the
~; four-bus power distribution system, this represents an
equivalent six percent increase in the weight of
conductor material over an equivalent linear distance
spanned by the closely spaced bars within the
remaining extent of the bus system. For the long
lengths of busway required in most industrial
operations, the amount of extra conductor material
required to provide sufficient expanded connector
regions is substantial.
Canadian Application Serial No. 582,155,
filed November 3, 1988, Hibbert et al, entitled
"Thermally Efficient Power Busway Housing" describes a
lightweight electrical power bus assembly that
includes power bus conductors bolted to the power bus
housing. To expand these bus hars to provide for
connection with the power take-off assembly would
create thermal loads to the system to substantially
- ~ reduce the overall thermal efficiency. This Canadian
application should be revlewed for its teachings of
the use of thermally conductive and electrically
insulative coatings.
Canadian Application Serial Mo. 576,343,
filed September 1, 1988, Richards et al, entitled
"Power Distribution Busway System" teaches the use of
an expanded integrally formed contact blade on each of
the bus bars in the power take-off region of the
system to allow for connection with the power take-off
assembly without expanding the respective bus bars.
The use of integrally formed contact blades, however,
requires expensive forming equipment that must be
incorporated within the bus bar manufacturing
operation. The present invention proves a simpler and
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more cost efficient method of providing extended
contact blades.
U.S. patent 4,394,532, issued July 19, 1983
to Aguayo and Japanese Patent 40590 both describe the
attachment of linear contact blades to miniaturized
bus bars used within electronic computers for
electrical connection with the individual bus bars.
The attachment of linear contact blades to industrial
power distribution systems carrying currents in excess
of hundreds of amperes, however, has not heretofore
proved commercially feasible.
One pu~pose of the instant invention
therefore, is to provide a power bus system which
allows interconnection with a plurality of power
take-off assemblies without increasing the amount of
conductor material at each individual power take-off
position and without having to expand a part of the
individual power buses.
SUMMARY OF THE INVENTION
Rectangular power bus conductors within a
closely-spaced power bus system are each provided with
an off-set extending conductor blade to provide a
power take-off region for electrical connection with a
power take-off assembly without increasing the amount
of copper material used within the power bus system.
; Each conductor blade is off-set from the preceding
blade within the power take off region to provide
sufficient interphase air gap for electrical isolation
purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a bottom perspective view of a
multiphase busway system and power take-off assembly
according to the prior art,
FIGURE 2 is a front sectional view of a
thermally efficient busway system used with bus bars
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having the contact blade tabs according to the
invention;
FIGURES 3A and 3B are top perspective views
of the contact blade tabs and bus bars according to
the invention; and
FIGURE 4 is a front sectional view of the
busway system of Figure 2 containing bus bars having -
the contact blade tabs according to the invention.
GENERAL DESCRIPTION OF THE INVENTION
Before describing the electric power busway
system of the invention, it is helpful to describe one
example of a power busway system 10 as currently
-~ employed which is depicted in Figure 1. The busway
system usually includes four bus bar conductors 11-14
(hereafter "bars"~, each carrying a separate phase of
a multi-phase power distribution system and each
containing an insulative coating 15 to electrically
insulate the bars from each other and the housing (not
shown). An expanded connector region 9 is shown along
the bars wherein each of the bars is shaped to define
corresponding spaces 20, 21, 22 and the insulation is
removed to expose a copper or aluminum contact blade
16-19 which is subsequently tin or silver-plated.
These expanded connector regions 9 are arranged every
two feet or so t accommodate a power take-off assembly
27 for delivering power to associated electrical
equipment. A commonly employed power take-off
assembly generally comprises a metallic enclosure 28
which~supports three or four corresponding spring type
contact blade receiver stabs 23-26 which are
electr~ically insulated~from each other and from the
enclosure 28. A pair of metal grounding plates 29, 30
are provided outboard of the receiver stabs. A
knock-out 31 is formed within one side of the
enclosure~to allow for wire connection between the
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contact blade receiver stabs and the associated
electrical equipment. When electrical interconnection
is made between two separate power busway systems, a
similar expanded connector region with the contact
blades omitted, is employed. One such power busway
interconnecting arrangement is described within
Canadian Application Serial No. 594,601, filed March
23, 1989, Hibbert et al, entitled "Adjustable Joint for
Electrical Busway", and Canadian App:Lication Serial No.
594,602, filed March 23, 1989, Beberman et al, entitled
"Thermally Efficient Splice Joint for Electrical
Distribution Busway". Both of these Canadian
Applications should be reviewed for their teachings of
busway joint connectors.
A thermally efficient busway system 32 such as
described in the aforementioned Canadian Application
Serial No. 582,155 is depicted in Figure 2 to consist
`~ of a pair of side plates 33, 34 encompassing bus bars
;~ 35-38. The side plates and bus bars are held together
by means of a thru~bolt 39 and an insulative epoxy
coating 40 electrically isolates the bus bars from each
other and from the side plates. As noted within the
aforementioned Canadian application, the close
proximity of the bus bars promotes the transfer of heat
out to the side plates 33, 34 whereby the heat becomes
dissipated to the surrounding air. It is important
therefore not to have to separate the bus bars in order
~ o provide~for interconnection therewith. The
;~ ~ invention accordingly provides means for allowing for
electrical connection with the individuaI bus bars
within a thermally efficient busway system without
~having to~separate the individual bus bars.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The means for providing electrical connection
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with the bus bars within the busway system 32
according to the invention is best seen by referring
now to Figures 3A and 3~. An off-set contact blade
tab 43 hereafter "off-set tab" is formed from a single
bar of copper or aluminum to define a planar vertical
surface 44 and a curved surface 45. The planar
surface is arranged for good electrical connection
with a power take-off receiver by welding or braæing
the bottom edge 46 of the off-sat tab 43 onto the top
surface 42 of a copper or aluminum bus bar 41. When
the off-set tab 43 is welded to the bus bar as
indicated at 49 in Figure 3s, an epoxy coating 48 is
applied to both the bus bar 41 and the off-set tab
43. The epoxy coating electrically isolates the
rectangular copper or aluminum bar 47 and the off-set
tab 43, except for that part, ~4A of the planar
vertical surface 44 to which electrical connection is
made. The opposite surface of the off-set tab 43,
although not shown, is also masked during the epoxy
deposition purpose to insure a good electrical contact
with the power take-off receiver.
The function of the curved surface 45 is
best seen by referring now to Figure 4 wherein a
busway section 50 i5 depicted containing bus bars
25 35' 38', each containing an off-set tab 43 welded
thereto. The off-set tabs extend upwards through
corresponding slots 52 formed in the cross-piece 51
that joins the upstanding rails 53 on the busway
enclosure side plates 33, 34 to define insulating
30 spaces 54, 55, 56 which can receive standard power
take-off assemblies such as depicted earlier at 27 in
Figure 1. It is noted that the epoxy coating 40 is
; applied to the bus bars 35'-38' except for the exposed
surfaces 44A. This provides good electrical isolation
to the off-set tabs to prevent inadvertenk contact
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therewith except by means of the power take-off
assembly.
The provision of a welded connection between
the off-set tabs and the bus bars, readily lends
itself to an automated welding process whereby the
off-set tabs are robotically welded to the bus bars at
predetermined locations during the bus bar
manufacturing and assembly process.
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