High current and low current electrical busway systems having compatible bus plug

A low-current busway which includes a busbar spacing compatible with a high-current busway is described. A common bus plug connector for use with a high-current busway and a low-current busway is also described. The low-current busway includes busbars defined by first centerline-to-centerline spacing and a first thickness. The high-current busway includes busbars which include plug-in tabs with a second centerline-to-centerline spacing generally equal to the first spacing. The plug-in tabs are of a second thickness generally equal to the first thickness. The common bus plug connector includes a plurality of conducting fingers spaced at a third centerline-to-centerline spacing generally equal to the first and second spacings.

FIELD OF THE INVENTION 
The present invention relates generally to improvements in electrical power 
distribution busways and approaches to interconnecting such busway 
systems. More specifically, the present invention relates to methods and 
apparatus for providing a bus plug which is readily interchangeable with 
both high-amp and low-amp busway systems. 
BACKGROUND OF THE INVENTION 
Electrical power distribution, or busway, systems are used to distribute 
electrical power throughout buildings, particularly commercial or 
industrial type buildings. Generally, a busway includes a number of busway 
sections which are connected to one another by busway joints. Each busway 
section includes a housing that encloses a plurality of busbars which may 
be phase busbars, neutral busbars, or ground busbars depending on the 
particular application. High-amp busways, generally utilizing larger 
busbars, are employed for applications requiring current capacity of 
approximately 600 amperes or higher. For applications requiring less 
current, typically 100 to 800 amperes, low-amp busways are employed. Due 
to the lower current capacity requirements, low-amp busbars are generally 
smaller and do not maintain the same spacing as high-amp busbars. 
Machines, lights, tools and other components requiring electricity are 
provided access to the power conducting busbars at various power tap-off 
locations disposed along the busway. An opening is typically provided 
through the housing at each power tap-off location and the conductive 
material of the busbars is exposed for connection with an appropriate plug 
connector or bus plug. 
A bus plug generally includes an electrical box containing a protective 
device, such as a circuit breaker, and a disconnect switch. A mechanical 
connector is provided for mechanically attaching the bus plug to the 
busway. An electrical connector extends from the bus plug through a window 
in the busway housing. The connector includes several flat "stab" 
conductors, or fingers, that make contact with the busbars within the 
busway. The fingers of the connector must be spaced apart so as to be in 
registration with the busbars. Due to the differing busbar-to-busbar 
spacing for typical prior art high-amp and low-amp busways, bus plugs for 
high-amp systems and for low-amps systems are generally not 
interchangeable. 
Manufacturing and storing different plug connectors for different 
applications results in increased costs to both manufacturers and 
purchasers. Accordingly, it would be advantageous if a low-amp busway 
maintained a busbar-to-busbar spacing compatible with high-amp busways. 
Additionally, it would be advantageous if a common bus plug connector 
could be used for highamp and low-amp busways. 
SUMMARY OF THE INVENTION 
The present invention provides for a common bus plug connector for 
interchangeable use in both high-amp and low-amp busway systems with 
busbars which maintain a common centerline-to-centerline distance. 
Additionally, the present invention provides for a low-amp busway which 
maintains a busbar centerline-to-centerline distance that is compatible 
with the busbar centerline-to-centerline spacing of a high-amp busway. 
Thus, the present invention provides for an electrical power distribution 
system including a common bus plug connector, a compatible high-amp busway 
and a compatible low-amp busway. 
A more complete understanding of the present invention, as well as further 
features and advantages, will be apparent from the following Detailed 
Description and the accompanying drawings.

DETAILED DESCRIPTION 
The present invention provides for a common bus plug connector for 
interchangeable use in both high-amp and low-amp busway systems with 
busbars which maintain a common centerline-to-centerline distance. 
Additionally, the present invention includes a low-amp busway which 
maintains a busbar centerline-to-centerline distance that is compatible 
with the busbar centerline-to-centerline spacing of a high-amp busway. The 
present invention now will be described more fully with reference to the 
accompanying drawings, in which several presently preferred embodiments of 
the invention are shown. This invention may, however, be embodied in 
various forms and should not be construed as limited to the embodiments 
set forth herein. Rather, applicants provide these embodiments so that 
this disclosure will be thorough and complete, and will fully convey the 
scope of the invention to those skilled in the art. 
FIG. 1 shows a partial cross-sectional view of a high-amp busway 10 which 
may be advantageously employed in accordance with the methods and overall 
system of the present invention. The presently preferred high-amp busway 
10. is described in greater detail in U.S. Pat. No. 5,442,135 entitled 
"Electrical Power Distribution Busway and Housing" which is incorporated 
herein in its entirety. The high-amp busway 10 includes a plurality of 
busbars 12 disposed within a busway housing 14. Each busbar 12 is coated 
with an insulative layer 13. The insulative layer 13 on each busbar 12 
prevents electrical contact or arcing between the busbars 12. FIG. 2 is a 
perspective view illustrating the busbars 12 of the high-amp busway 10. In 
the preferred embodiment, the busbars 12 share a centerline-to-centerline 
spacing 12a of generally 0.29 inches. Due to varying thicknesses of 
insulative layer 13, however, the centerline-to-centerline spacing may 
range from 0.29 inches to 0.35 inches. The busbars 12 include plug-in tabs 
16 configured for engagement with a bus plug connector. The plug-in tabs 
16 are preferably formed by a coining operation from the conductive 
material of busbars 12 and have a thickness of approximately 0.094 inches. 
A insulator assembly 18, which includes a removable door 20, provides 
access to the plug-in tabs 16 through a plurality of openings 18. 
Additionally, the plug-in tabs 16 maintain the same 
centerline-to-centerline spacing 12a of approximately 0.29 inches as the 
busbars 12. As seen in FIG. 1, the housing 14 includes a plurality of 
slots 24 and upper and lower flanges 22 which provide a structure for the 
common bus plug connector (described below) to connect. 
As shown in FIGS. 3A and 3B, a series of busway 10 and busbar 12 widths 
corresponding to a series of maximum amperage ratings can be manufactured 
in order to provide varying current capacity requirements. FIG. 3A shows a 
Table 300A which lists the busway widths, busbar widths, busbar 
thicknesses and maximum current capacity for aluminum composition busbars 
12 for alternative embodiments of busway 10 in accordance with the present 
invention. FIG. 3B shows a Table 300B which lists the busway widths, 
busbar widths, busbar thicknesses and maximum current capacity for copper 
composition busbars 12 for alternative embodiments of busway 10 in 
accordance with the present invention. All of the alternative embodiments 
of the high-amp busway 10 include the upper and lower flanges 22. 
FIG. 4A shows a cross-sectional view of a low-amp busway 40 in accordance 
with the present invention. The presently preferred low-amp busway 40 is 
described in greater detail in U.S. patent application Ser. No. 09/165,758 
filed on the same date as the present application, entitled "An Electrical 
Power Distribution Busway Having A Two-Piece Housing" which is 
incorporated by reference herein in its entirety. A plurality of low-amp 
busbars 42 are horizontally contained within a busway housing 44 in a 
spaced-apart relationship. The busbars 42 are coated with an insulating 
layer 43 to prevent arcing between the busbars 42. In the preferred 
embodiment, the insulating layer 43 is an epoxy insulation applied via an 
electrostatic spray process. A pair of vertical side channels 46 are 
joined to form the busway housing 44. The busbars 42 are spaced apart at a 
predetermined centerline-to-centerline distance 42a approximately 
corresponding to the centerline-to-centerline distance 12a of the high-amp 
busbars 12. In the preferred embodiment of the present invention, the 
centerline-to-centerline distance 42a is approximately 0.32 inches. 
Additionally, the busbars 42 are of generally the same thickness, 0.094 
inches, as the plug-in tabs 16, allowing a common bus plug connector 
(described below) to connect to both the plug-in tabs 16 and the busbars 
42. The housing 44 includes a plurality of slots 58 (shown in FIG. 6) and 
upper and lower flanges 48 which provide a structure for the common bus 
plug connector to connect. 
FIG. 4B shows an alternative embodiment of a low-amp busway 49 in 
accordance with the present invention. As shown in FIGS. 5A and 5B, a 
series of busway 40 and busbar 42 widths corresponding to a series of 
maximum amperage ratings can be manufactured in order to provide varying 
current capacity requirements. FIG. 5A shows a Table 500A which lists the 
busway widths, busbar widths, busbar thicknesses and maximum current 
capacity for copper composition busbars 12 for alternative embodiments of 
busway 10 in accordance with the present invention. FIG. 5B shows a Table 
500B which lists the busway widths, busbar widths, busbar thicknesses and 
maximum current capacity for aluminum composition busbars 12 for 
alternative embodiments of busway 10 in accordance with the present 
invention. All of the alternative embodiments of the high-amp busway 
include the upper and lower flanges 48. 
FIG. 6 shows a perspective view of the low-amp busway 40. A door assembly 
50 is attached to the busway housing. The presently preferred door 
assembly 50 is described in greater detail in U.S. patent application Ser. 
No. 09/165,696, entitled "Dual-Hinged Door For An Electrical Power 
Distribution Busway", which is incorporated by reference herein in its 
entirety. Door assembly 50 includes a plurality of slots 52 which provide 
access to the busbars 42 contained within low-amp busway 40. While a 
presently preferred door assembly is described herein, it will be 
recognized that other suitable mechanisms may be employed to provide 
access for connection to the busbars 42. 
FIG. 7 shows a perspective view of a common, or interchangeable, bus plug 
70 in accordance with the present invention. The presently preferred bus 
plug 70 is described in greater detail in U.S. patent application Ser. No. 
09/165,690, now U.S. Pat. No. 6,023,030, filed on the same date as the 
present application, entitled "Bus Plug Door Interlock" which is 
incorporated by reference herein in its entirety. The bus plug 70 includes 
a plurality of conductive fingers 72 for connecting to the plug-in tabs 16 
of high-amp busway 10 and the busbars 42 of low-amp busway 40. In the 
preferred embodiment, the fingers 72 are composed of copper. As seen in 
FIG. 9, each finger 72 is held in place by a steel tension member 73 which 
is connected to the finger 72 by a pair of rivets 74. The tension members 
73 force each finger 72 to maintain contact with an opposing finger 72 
when the bus plug 70 is not connected to the busway. The finger ends 75 
are arc-shaped to provide a lead-in to facilitate connection to the 
busbars 12 and plug-in tabs 16. Each finger 72 is of appropriate thickness 
to allow for flow of electrical current and to fit within the slots 52 and 
the openings 18. Each pair of conductive fingers 72 is spaced apart at a 
predetermined distance of 0.32 inches, generally corresponding to the 
centerline-to-centerline distance of the high-amp busbars. In other words, 
the pairs of conductive fingers 72, the high-amp busbars 12 and low-amp 
busbars 42 maintain approximately the same centerline-to-centerline 
spacing. 
The bus plug 70 includes a pair of mounting hooks 74 disposed on opposite 
sides of the bus plug 70. The mounting hooks 74 are adapted to attach to 
the flanges 22 of the high-amp busway 10 and the flanges 48 of the low-amp 
busway 40. A support rail assembly 76 provides a generally U-shaped 
structure to enclose the housing 44 of the low-amp busway 40 and the 
housing 14 of the high-amp busway 10. An interlock stab assembly 78 is 
disposed on the bus plug adjacent to the support rail assembly 76. 
FIG. 8 is an end view of the high amp busway 10 connected to the common bus 
plug 70 in accordance with the present invention. The bus plug 70 engages 
the housing 14 of the high-amp busway 10 and is locked into place by the 
interlock stab assembly 78 engaging the slots 24. Additionally, the 
mounting hooks 74 lock onto the flanges 22. As best seen in FIG. 9, the 
conductive fingers 72 engage the busbar plug-in tabs 16, providing an 
electrical connection for current to flow. Each busbar plug-in tab 16 is 
disposed between a pair of conductive fingers 72. 
FIG. 10 is an end view of the low-amp busway 40 connected to the common bus 
plug 70 in accordance with the present invention. The bus plug 70 engages 
the housing 44 of the high-amp busway 40 and is locked into place by the 
interlock stab assembly 78 engaging the slots 58. Additionally, the 
mounting hooks 74 lock onto the flanges 48. As best seen in FIG. 11, the 
conductive fingers 72 engage the busbars 42, providing an electrical 
connection for current to flow. Each busbar 42 is disposed between a pair 
of conductive fingers 72. As described above, each finger 72 is held in 
place by a tension member 73 which forces the finger to maintain contact 
with the busbar 42.