1. - ericssonhistory.com

More documents

Recommendations

Info

Fig- 4Label holder NBM miTable IStripProtector elementsConnectionNEL 111)0-0HZ)NFL 3101NFL 3111Fuse NGH 2201 (0.5 A)Combined fuse NGH 5001-05-2)NFL 3201NFL 3211Fuse NGH 2202 (1 A) and overvoltagearrester NGA 3001Combined fuse NGH 5001 andover-voltage arrester NGA 3001L ^ 1||..o~X—|-0sFig. 2 shows three of the 10-pair strips tabulated above, viz. NEL 1100,NFL 3111 and NFL 3211. They are assembled on a frame of nickel-platedbrass sheet, which at the same time constitutes the earth connection for theover-voltage arresters. The 10-pair fuse strips NFL 3101 and combined fusestrips NFL 3111 are of identical construction, differing only in the protectort^x6977Fig. 5Over-voltage arrester NGA 3001 (left)and combined fuse NGH 500116
•G rLrlFig. 6The combined fuse NGH 5001A end capB fuse wireC glass tubeD rodE solderF helical springelements. Similarly the 10-pair strips NFL 3201 are of identical constructionto strips NFL 3211. The pairs are on 10 mm centres. Every installed 10-pairstrip occupies a vertical space of 105 mm.The contact springs, of tinned german silver, are assembled on plasticblocks with high insulation resistance to breakdown and leakage currents.The leakage current paths are at least 4 mm long, which suffices forindoor installation. Under the connecting screw is a slot for the wire. Thisarrangement greatly simplifies the wireman's work, as the end of the wireneed not be formed into a loop.The Protector MountingFig. 3 shows a protector mounting for five 10-pair strips. When carryingover-voltage arresters, the mounting at the same time serves as earth connection.As stated above, mountings are made for one. two and five 10-pairstrips. No waste of space is involved in placing several mountings one abovethe other. For instance, one 10-pair and two 20-pair mountings occupy thesame space as a 50-pair mounting. The mounting is made of nickel-platedbrass and has earth terminals at each end. It also carries fanning strips forthe jumper wires. The fanning strips are made of anodized aluminium. Theanodization provides satisfactory protection against corrosion and is electricallyinsulating.1000100101,iVsAB\nni0,1 0,2 0,5 1 101|11111\\\ •*Fig. 7 X 2150Fusing curve of combined fuse NGH5001Label Holder NBM 1111Every 10-pair strip can be fitted with a label holder as shown in fig. 4. Twospring catches permit the holder to be pushed into position without needingto be secured by screws. It is supplied with label and transparent protectingplate.Over-voltage Arrester NGA 3001This protector, illustrated in fig. 5, consists of two cylindrical metalelectrodes of a patented alloy which are pressed into a plastic tube so as toproduce the proper gap between them. The breakdown voltage is 700—1.000 volts d.c. As in all over-voltage arresters of this type, the strikingpotential increases by 10 to 20 per cent on steep wave front voltage surges.Its load capacity is greater than that of carbon arresters. Arrester NGA 3001withstands a large number of discharges of up to 0.2 coulombs, whereascarbon arresters are often short-circuited at 0.1 coulombs. In the event of apermanent arc being formed, the electrodes become heated. This causes theplastic tube to soften, whereupon the electrodes are forced together by themounting springs so that the line becomes earthed. The protector must then bereplaced.Combined Fuse NGH 5001This fuse, illustrated in fig. 6, is of a patented design. The end caps A andthe glass tube C are the same as in fuse NGH 22. F is a helical spring which,at point E, is attached by a solder of low melting point to the metal rod D.Also soldered to point E is an insulated resistance wire, which is first wounda number of turns around the rod and then continues in the form of fusewire B. At fairly low currents the rod heats up until the solder at point Emelts. Owing to the relatively large mass of the rod. a certain period elapsesbefore the break occurs. At high currents wire B melts very quickly, andbefore the solder. Fig. 7 shows the fusing curves of the solder (A) and theA fuse wire (fi). The curve of the combined fuse unit thus follows the fullvdrawn line. The resistance of this fuse is only about 4 ohms. The resistanceof the old type of heat coil was 8 ohms.17
Page 3 and 4: ERICSSON REVIEWVol. XXXIV 1957RESPO
Page 5 and 6: ERICSSON REVIEWVol. XXXIV No. 1 195
Page 7 and 8: ularities serious enough to affect
Page 9 and 10: Faults at Centrum Jan.—June 1956.
Page 11 and 12: The same practice is adopted at the
Page 13 and 14: Mechanization of the Aland Telephon
Page 15 and 16: The quality of cable construction w
Page 17 and 18: exchange, while another has perhaps
Page 19: Fig. 2 X 6975IO-pair strips(From le
Page 23 and 24: Visual Staff Locator System for Sma
Page 25 and 26: Fig. 4 x 8008Keyset KEM 3294placed
Page 27 and 28: Traffic Signals at Vasterbron, Stoc
Page 29 and 30: Three Programme Vehicle ControlThe
Page 31 and 32: x 8009 Ordinary vehicle control imp
Page 33 and 34: TownExchangeNumberof linesTownExcha
Page 35 and 36: NEWS/romAll Quarters of the WorldL
Page 37 and 38: L M Ericsson, Midsommarkransen, isa
Page 39 and 40: 3056 .(487ricss\nUQ;Jao0-V5roc0-ft

1. - ericssonhistory.com

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?