CA1310080C - Bus system - Google Patents

Abstract

ABSTRACT
A bus bar and duct combination as is disclosed comprising a plurality of bus bars encased and held, at a central part between end joint parts of the bus bars, within a metal duct such that the bus bars, the duct and electrical insulation members are in intimate contact to provide heat transfer from the bus bars to the duct by way of conduction.

Description

sUS SYSTEM
Thiq invention relates to a bus 6ystem for electrical distribution and relates particularly but not exclusively to bus ductin~ systems and to apparatus for bus take off connections.
Most presently known and used bus bars and bus bar duct systems are bulky due to the presence of airways along the ducts. There airways provide electrical clearance of the bus bars and cooling is effected wholly or partly by convection. Such cooling by convection is not an efficient or quick method of heat dissipation from the bus bars.
Another reason for the bulkiness of presently known and used systems is the necessity to provide mechanîcal reinforcement of the bus bars to restrain the bars against violent deformation should a short circuit or overload cause reactance between neighbouring bus bars. This reinforcement i~ usually effected by means of discrete insulating support within the duct or by continuously wrapping a group of bus bars with an insulating material of suitsble strength. Such methods invariably include additional air pockets, large or small, which result in convection heat transfer from the bus bars when heating occurs. Furthermore, known bus bar systems have lower current rating~ due to low contact pressures between serially connected bus bar lengths or great cost due to the necesslty to e.g. tin plate the ~oining tongues of bus bars.
It is the ob~ect or ob~ects of this invention to reduce or overcome some or all of the disadvantages of the currently used bus bars and/or bus bar duct systems.
According to the pre~ent invention there is provided a bus duct including a plurality of bus bars stacked in ~ubstantially parallel flat-to-flat relationship within a hou~ing. The bus bars have ~oining means external of the housing and the housing comprises a first pair of walls each di~po~ed one on either side, parallel to and longitudinally along the bus bars, and the second pair of : wall8 disposed transversely and longitudinally of the bus bars and fixed to the first pairs of walls to define a cavity within which the bus bars are accommodated. The .~ .
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~3~ 1 3 1 0080 `- first pair of walls and the bus bars being electrically insulated one from another by individual interpo~ed sheets of separate insulating material and the second pair of wall~ and the bus bars are electrically insulated from one another by resilient insulation means disposed between the plurality of bus bars and the second pair of walls. Each of the first pair of walls additionally includes a plurality of integrally formed outwardly pro~ecting longitudinally disposed cooling fins, the bus bars, insulating material of the interposed sheets and the resilient insulation means, and the first pair of walls being held in intimate contact with one another to provide conductive heat transfer from the bus bars to said cooling fins.
The duct provideg full mechanical support for the bus bars and thuR internal reinforcement means are not required. Preferably the bus bars are substantially entirely of copper or aluminium and the duct is of extruded aluminium having a plurality of integrally formed cooling fins around at least a ma~or portion of the periphery of the duct. Preferably the duct is formed of two, or two pairs of, symmetrical substantially U shaped cross-sectional complimentary duct ~ections. The duct may include a separate extruded rubber sealing and electrically insulating member between the sides of the bus bars and the ~ides of the duct which interleave with the insulating members between and extending laterally of the individual bus bars. Preferably, one or more bus bar and duct combination(s) are adapted for modulator interconnection or coupling.
A bus bar and duct combination may comprise a plurality of bus bars encased and held, at a central part between end ~oint parts of the bus bars, within a metal duct such that the bus bars, the duct and electrical insulation members are in intimate contact to provide heat transfer from the bus bars to the duct by way of conduction in which the duct is formed of constant cross-section extruded metal duct sections. Preferably the metal of the duct sections is aluminium or aluminium alloy. Preferably the duct sections have a plurality of integrally formed ?
cooling fins around the periphery of the duct formed from -.... ~- . -`- the duct sections to enhance radiation of heat from the combination and to increase the mechanical strength of the combination to guard against mechanical failure of the combination in the event of an electrical overload when a plurality of bus bar and duct combinations are used in an electrical supply system.
In a bus bar and duct combination as described above, the ~oint sections may be adapted for eoupling with other bus bar and duct eombination(s) and provided by splaying of the bus bars external of eaeh end of the duet to form substantially parallel spaced bus bar seetions which can be interleaved with another bus bar and duet combination in series. Modular bar and duct combinations facilitate interconnection with other bus bar and duct combinations.
Appropriate insulation is provided at the ~oint section between the pairs of bus bar ~oint sections. Preferably the bus bars have laterally extending U shaped slots therein to aecommodate appropriate joint holding means such as bolts and nuts. Preferably the ~oint is covered above and below by suitable insulating means and eover plates.
Preferably the ~oint is eovered on eaeh side and ~trengthened against movement or deformation by means of suitable fish or ~oining plate~. Preferably there i8 provided additional mean~ to connect each bus bar duct eombination to provide appropriate earthing of the eombination.
Preferred form~ of the invention will now be deseribed with referenee to the aeeompanying drawings in whiehs Fig. l is a partial eut away side view of a bus bar and duct eombination in aeeordanee with the invention;
Fig. 2 i8 a partial top view of the eombination of Flg. 1 showing both end eonnecting portions;
Fig. 3 is a cro~s-s3ctional view in the direction B-B
of Fig. l;
Fig. 4 is a cros~-sectional view in the direetion A-A
of Fig. l;
Fig.5 i~ an enlarged ~ide view of a ~oint between two bus bar~ of Fig. l;
Figs. 6 and 7 are eross-seetional elevations similar to Figure 4 showing alternate duct configurations according to the invention;

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Figs. 8 and 9 ~how joint bus bar and duct combinations in accordance with the invention;
- Fig. 10 ~hows an expansion joint bus bar and duct combination in accordance with the invention; and Fig. 11 shows an alternate joint detail of bus bar ànd duct combination in accordance with the invention.
Referring to the drawings, there is shown a bus bar and dùct combination 10 having a central part 11 and end or ~oint section6 12a or 12b. The central part 11 of the combination includes duct 13 and one neutral and three àctive phase and bu~ bars 14, 15, 16 and 17. The duct 13 comprise6 two extruded metal duct section6 13a, 13b of substantially U shaped cross-section which are connectable together to form the duct 13 and to enclose a passageway of 6ubstantially rectangular cross-section having upper and lowér wall6 18a, 18b and side walls l9a, l9b. The pas6àgeway contains bus bars 14, 15, 16 and 17 which are of ~ubstantlally tectangular cross-section ~as is usual) and extend beyond the ends of the duct to form joint parts as will be desctibed later.
The upper and lower walls of the duct 13 are 8eparated from the bus bars 14 and 17 respectively by duct insulatlon sheet6 20 to provide electrical insulation bétwéen the duct and the bus bars. The bus bars are separ~ted from one another by bus bar in6ulation sheets 21 to p~ovlde electrical insulation between ad~acent bus bar6.
The lnsùlation sheets 20 and 21 naturally extend the entire length of the duct 13 and extend beyond the duct into the ~oint sections 12. The insuiation sheets 20 and 21 extend laterally beyond the edges of the bus bars and intermesh wlth extruded rubber side in6ulators 22 which are designed ~o électrically insulate the bus bars from the duct side wall6 19 ànd to substantially 6eal the bus bars within the d~ct 13 to prevent an electrical conduction path around the edges of tbe in6ulating strips in the event of ingress of molstu~e. The bus bars 14, 15, 16 and 17 and insulation 20, , 1 3 1 00~0 21 are in intimate contact with each other and with the duct 13 as described to provide direct heat transfer from the bus bars to the duct by way of conduction to the outer surfaces of the duct to remove any excess heat generated due to current overloads or short circuit in or between the bus bars. The bus bars and associated insulation are rigidly néBtled wlthin the ducting over substantially its entire length to counteract àny excessive reactance or repulsion éffécts between bus bars which may occur with any current overload or short circuit condition when in use.
The duct sections 13a, 13b, as previously described are of extruded metal of substantially U shaped cross-section and preferably include a plurality of integ~ally formed fins 23 to increase the surface area of thé duct and to increase dissipation of heat generated as described above. Fin 23 may also provide a means of Bubstantially even overall surface heat dissipation.
The jolnt fins 24 at the centre joint line 25 of the duct include appropriate holes for provision of bolts 26 to hold the assembled combination 10 together. The joint flns 24 provide additional reinforcement of upper and lower duct wall6 18 aqainst any repulsion occurring between the bu~ bars for reasons described above.
At the ~oint sectlon6 12, the bus bars, which as prevlo~sly described, extend beyond the ends of the duct, are splayed apart to permit interleaving of the bus bars to provlde for electrical connection of serially disposed bus b~r ~nd duct combination sections. The interleaving bus bars and duct are adapted for mutual mating coupling.
As will best be seen in ~ig. 5, the bus bars 14, 15, 16 and 17 are splayed apart at their ends to form substantially parallel ~oint sections 14a, 14b, 15a, 15b, 16à~ 16b and 17a, 17b. The insulation sheets 20 and 21 termlnate short of the joint sections eg. 14a, 14b to permit interleaving of the bus bars to form the ~oint section and to permit electrical contact between pairs of bus bars 14a : . - .

and 14b, 15a and 15b etc. Interpo6ed between these electrically connected pair~ of bus bars are ~o~nt insulator6 2i to prc~vide electrical insulation between the neutral and three active phase bus bar pairs 14a, 14b and 15a, 15b, etc.
The ~unction is held together to provlde good contact between the member bars of the bus bar pairs by meanB of ~unction nut/bolt 2B and washer 31 combination together with ~oint cover plates 29 and appropriate junction plàte in6ulation 30. Furthermore, each bolt/nut combination i6 provided with a number of bolt insulators 32 having a~
tubular 61eeve 6ection 33 and 35 and an intermediate flange 34.
The upper 61eeve portion 33 of one tubular BeCtion 18 adapted to fit within the face of the lower eleeve portion 35 and the bore of the combination adapted to teceive and in6ulate bolt 28. Flange sections 34 extend latetally and overlap with joint in6ulators 27 and plate in6ulator6 30 to en6ure adequate electrical insulation of the p~rts of the ~oint from one another. The bolt/nut combinàtlon 28 i6 in electrical contact with earth connectlon 36 which is al60 in électrical connection with dUct ~3 by mean8 of earth bolt6 37.
The ~olnt i6 6tabilized by way of fi6h plate6 38 whlch cooperate with fl6h plate flange6 39 on duct 13 and a1BO wlth cove~ plate flange6 40 on ~oint covee plate 29.
The fish plate 16 held in place by way of nut and bolt combinatlons 41. -The entlre bus bar and duct combination is sub~t~ntlally 6ealed, e.g., by way of moulded neoprene rubbet collar 42. Additionally neoprene rubber 6ealing material may be included at the 6play of the bu6 bar6 a6 shown at 43 in Flg. 1.
The bus bar and duct combination preferably lhclude# slots 44 at the ~oint 6ections of the bu6 bar6 to f~cllltate as6embly of a series of bu6 bar duct combination6 ; as described.

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, . -', ' ,. , 1 3 ~ 0080 Referring to Figure 6, there i~ shown in cros~-6ection ~imilar to Figure 4, a bus bar and duct combinatlon 50 comprising four bus bars 51 encased in duct 52 a6 previously described. The duct 52 comprises extruded 5 alumlnium alloy upper 53 and lower 54 sections and side sections 55. The bus bars 51 are, as before, separated from one another and from the upper and lower duct sections 53,54 by appropriate insulation 56. The bus bars 51 are also, as before, 6eparated from the side duct sectlon6 55 by mean6 of 10 lh6ulation 57 preferably, neoprene rubber. The upper and iower duct ~ections 53 and 54 are each integrally formed~ by extru610n and include mechanical strengthening and cooling flng 58.
Referring to Figure 7, there is shown in 15 cros6-#ection 6imilar to Figure 6, a duct 60 comprising two extruded aluminlum alloy duct sections 61 and 62 integrally fo~med wlth mechanical 6trengthening and cooling fins 63.
Integrally formed flanges 64 on duct side sections 65 permit thë duct when a66embled to rigidly encase and support bus 20 b~r~, not 6hown.
Referrlng to Figure6 8 and 9, there i6 6hown an alternXtlve ~olnt con6truction for ~oining two bu6 bar and duct comblnation6 71 and 72. The combinations are ~oined at rlght ~ngles to permlt the bu6 bar and duct combination to bé routéd in ~ dlfferent direction. The combination6 71 and t2 ~re connected together by mean6 of ~oint piece 73 a6 shown be~t ln Flgure 9. The ~oint piece 73 lnclude6 bu6 barB 74 ~ prevlously and splayed to interleave wlth bus bars not shown of comblnations 71 or 72 a~ ha6 previou61y 30 been de6c~1bed. Sultable ln6ulatlon (not 6hown) and cover pl~te(~j 75 are lncluded ta provide rigldity and mol6ture resl~tance to the ~oint.
Referrlng to Flgure 10, there 16 6hown generally at 90 a fi~ther alternatlve ~olnt con6truction for ~oining two 35 btls b~lr ~nd duct combinatlon8 91 and 92 in the form of an éxp~n~lon ~olnt 93. The expan6ion ~olnt 93 lncludes a , ,~

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g plur~lity of bus bar connection plates 94 and 95 for individual electrical connection with the corresponding bus bars of the comb~nations 90 and 91. The plates 94 and 95 are connected by flexible expansion means 96 comprising a plurality of leaves or lamination~ of aluminium or copper sheet covered with a heat shrink plastics material to electrically insulate the expansion means 96 one from another as the ~oint moves a6 a result of the variations of the heat generated in the bus bar and duct combination from periods of low electrical current to periods of peak electrical current flow through the system. The joint include6 cover plate or plates 97 fixed at one end 98 to comblnation 91 and free to move at the other end 99 in relatlon to the other combination 92 as the movement due to heat expansion of the combinations dictates.
Referring to Figure 11, there is shown an alternative form of ~oint construction 100 (similar to that shown in ~igure 5) between two bus bar and duct combinations 101 and 102. The bus bars 103, 104, 105 and 106 of combination 101 are splayed to interleaf with bus bars 107, 10~ 109 and 110 of combination 102. The bus bars as before ~re apptop~iately 6eparatedj as and where required, by in~ tion mean6 111 ln 6imilar manner as hereinbefore de~ctibed.
The bus bars are preferably of aluminium metal but may be of copper if greater current carrying capaclty is ~equlred or may be made of any other 6uitable metal or metal ~llog oe cond~ctor. The insulating material may be of any ~itable materl~l and is preferably a pressed urethane flbreglaB6 sheet material of, for example, 1/16 to 1/32 inch ~1.6 to 0.~ mm approximately) thick. The bus bar and duct sy~tems may bé of any convenient length and most usually of 12 foot or 3.5 m in length. In the alternative, the earth connectlon between erlally connected bus bar and duct séctlon~ may be e6tabllshed by the ~oint cover plates or the flsh or ~oining plates.
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1 3 1 00~0 Whilst there i6 described herein a preferred form of the invention it will be readily apparent to those skilled in the art that modifications may be made to the bus bar and duct combination without departing from the spirit of the invention. For example, the bus bars have been described as being in a single stack of four substantially flat bars but they may equally well be constructed in a two by two stack. The bus bars may even be of quarter circular cross-6ection such that the bundle of four bus bars with appropriate insulation therebetween, forms a cylindrical bus bar combination which is then encased in tubular insulat~ion and J bus duct of two hemi-cylindrical cross-section extruded metal duct sections.
Furthermore, the duct sections instead of being ~ointed along plane/line 25 may be jointed along a plane/llne parallel to the bus bars themselves.

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Claims (6)

1. A bus duct including a plurality of bus bars stacked in substantially parallel flat-to-flat relationship within a housing, said bus bars having joining means external of said housing, said housing comprising a first pair of walls each disposed one on either side, parallel to and longitudinally along said bus bars and a second pair of walls disposed transversely and longitudinally of said bus bars and fixed to said first pairs of walls to define a cavity within which said bus bars are accommodated, said first pair of walls and said bus bars being electrically insulated one from another by individual interposed sheets of separate insulating material, said second pair of walls and said bus bars being electrically insulated one from another by resilient insulation means disposed between the plurality of bus bars and the second pair of walls, each of said first pair of walls additionally including a plurality of integrally formed outwardly projecting longitudinally disposed cooling fins, said bus bars, insulating material of said interposed sheets and the resilient insulation means, and first pair of walls being held in intimate contact with one another to provide conductive heat transfer from said bus bars to said cooling fins.

2. A bus duct as claimed in Claim 1 wherein the bus bars are rigidly held along substantially their entire length by said housing.

3. A bus duct as claimed in Claim 1 wherein the housing comprises two complementary shaped integrally formed extruded sections which form said first and second pairs of walls and said cooling fins.

4. A bus duct as claimed in Claim 1, 2 or 3 wherein the walls of the housing are of substantially uniform thickness.

5. A bus duct as claimed in Claim 1, 2 or 3 wherein the cooling fins also provide additional mechanical strength to the first pair of walls.

6. A bus duct as claimed in any one of Claims 1 to 3 wherein said first pair of walls and said bus bars are electrically insulated one from another solely by said individual interposed sheets of separate insulating material, and said second pair of walls and said bus bars are electrically insulated one from another solely by the resilient insulation means disposed between the plurality of bus bars and the second pair of walls.