[Electric engineering.] . raight out, thus pulling the blades out of theclips. Extra blocks may be kept on hand, ready fused, andone of these put in place of the blown fuse with very littledelay or danger to the attendant. The fuse is shown at /,and is clamped by means of the screws m, n. A vent hole/is provided in the lignum-vitae cover and the rush of airthrough this vent, together with the confined space, resultsin the suppression of the arc. When fuses are being 26 ELECTRIC LIGHTING. 11 replaced, care should be taken to see that the switch con-necting the fuse block with the dynamo is open
[Electric engineering.] . raight out, thus pulling the blades out of theclips. Extra blocks may be kept on hand, ready fused, andone of these put in place of the blown fuse with very littledelay or danger to the attendant. The fuse is shown at /,and is clamped by means of the screws m, n. A vent hole/is provided in the lignum-vitae cover and the rush of airthrough this vent, together with the confined space, resultsin the suppression of the arc. When fuses are being 26 ELECTRIC LIGHTING. 11 replaced, care should be taken to see that the switch con-necting the fuse block with the dynamo is open. This fuseblock is suitable for currents up to 150 amperes at ^,500 volts,and is the type of fuse shown on the switchboard in Fig. higher pressures fuse blocks are used in which the fuseis pulled wide apart as soon as it blows, thus breaking thearc. The use of fuses on low-tension lighting switchboards isnot as common as it once was, their place being taken bythe automatic circuit-breaker. Fuses are, however, used. Fig. 27. largely for alternating-current boards and also for protect-ing individual circuits on low-tension, direct-current are not as convenient or reliable as circuit-breakers,because it takes time to replace them when they blow, andonly too often they are replaced by a heavier fuse or even acopper wire, which is of scarcely any use as a , fuses of the same size do not always blow at thesame current, much depends on the nature of the fuse-block terminals. If the clamps are not screwed up tightly, Sir ELECTRIC LIGHTING. 27 local heating- will result, and the fuse will blow with asmaller current than it should. Also, it has been foundthat a fuse of a given cross-section and material will carry aheavier current when the distance between the terminals isshort than when it is long, on account of the conductingaway of the heat by the terminals. os ««?>. Circuit-Breakers. — The circuit-breaker is essen-tially an automatic swi
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