[Electric engineering.] . 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
[Electric engineering.] . 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 switch that opens the circuit wheneverthe current becomes too large. The current is usually sent. Fig. through an electromagnet or solenoid, which operates a tripand releases the switch when the current exceeds the amountfor which the breaker is set. Fig. 28 shows a typical 28, ELECTRIC LIGHTING. 17 circuit-breaker in the closed position. The current entersat a, passes through the coil c to stud d, thence to stud d and clip h, across through the cross-connecting piece j to a similarclip not shown in the figure. Thearm carrying the crosspiece j isheld in against the action of thespring k by means of the catch /.When the current reaches theamount for which the breaker isadjusted, the plunger in is drawnup, hitting the rod n a blow andreleasing the catch. This allowsthe arm to fly out, thus breakingthe circuit by pushing the bladesat each end of j out of clips 29 shows a front view of thesame style of breaker. The arcis not broken at the copper con-tact clips, as they are provided with auxiliary carboncontacts/that remain in contact shortly after the bl
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