GB702463A - Improvements relating to electrical power distribution systems - Google Patents

Abstract

702,463. Installation wiring. G. M. ENGINEERING (OTTERY ST. MARY), Ltd. Jan. 28, 1952 [Feb. 14, 1951], No. 3599/51. Class 38 (4). [Also in Group XXXVI] In a power distribution system comprising a number of busbars supported in metal ductings connected end to end and plug-in fuse boxes adapted to be secured to the ductings at intervals to provide distribution tap-off points, the busbars are engaged on one edge by first insulating members or cradles spaced along the ductings and are engaged and guided on the other edge by second insulating members positioned intermediately ofthe first members. The system is described as applied to factory installations where horizontal busbar runs at the different floor levels are connected by a rising main, Fig. 1 (not shown). Each ducting unit 1 is twelve feet long and has six tap-off points provided at busbar support cradles 13, Fig. 3, each cradle 13, Fig. 7, comprising a moulded insulating block grooved at 18 to receive the lower edges of the three phase busbars 11 and a neutral busbar 12 and having openings 21 extending right through to permit engagement of the plug-in fuse box contacts with the busbars from therebelow. The cradles 13 are supported by ducting closure plates 26 engaging shouldered edges on the cradle bases 28, the plates 26 being secured to the ducting by screws 27, Fig. 4. Moulded insulating guides 14, Fig. 9, are secured to the top wall of the ducting 1 mid-way between the cradles 13 and have notches 17 which receive the top edges of the busbars 11, 12. Adjacent ductings are joined by side plates 5 and a top strip 6, earthing continuity being ensured by a strap 9, and the busbars 11, 12, are connected by expansion joints of copper strip or braid 54. Bolts 30 extend through the ducting 1 and have nuts 35, clamping phosphor bronze earthing clips 36, the heads of the bolts being located in cradle end grooves 23. The fuse boxes 38, Fig. 11, have suspension plates 48 slotted at 50, the lower ends of the slots being enlarged and having a pressed out seating 51. The slots 50 receive bolts 29, 30, and the box 38 is secured to the ducting by nuts 52 having a shoulder which engages in the seating 51, Fig. 13, earthing of the box being ensured by the engagement of the plates 48 with the clips 36. The box encloses three phase fuses 39 and a neutral terminal block 42, leads 40, 41, to the. consuming device leaving through a.conduit-43. Contact with the busbars 11, 12, is made by pairs of contacts 47 which enter the ducting through the openings 21 in a cradle 13. To prevent the box being mounted back-to-front with the neutral lead 41 connected to a phase busbar 11, the cradle grooves 23, and hence the bolts 29, 30, are displaced from the centre line of the openings 21, and the centre line of the contacts 47 is similarly displaced from the centre line of the slots 50. The openings 21 in a cradle 13 not used as a tapping point may be closed by a plate having flanges which spring over the earthing clips 36, Fig. 12 (not shown). To take the weight of the busbars 11, 12, in a rising main or ducting 3, certain of the guides 14, e.g. one out of the six guides 14, in each ducting unit, is replaced by a stout insulating block 61, the block 61 having grooves to receive the busbars and being secured by bolts 62 to the ducting 3, Fig. 17. Adjacent the top and bottom surfaces of the block 61 each busbar 11, 12, is drilled at 59 to receive split-pin 60, whereby the block supports-the busbar.