Switchboards for power, light and railway service, direct and alternating current, high and low tension . ck of the board theyshould be so arranged that rain and snow cannot enterthrough them and reach the board, and in damp w^atlierthey should be closed tightly. A perfectly watertightceiling should be constructed over the entire switchboardso as to obviate all danger of injury by water falling fromoverhead. Switchboard fronts are made of marble and marbleizedslate, both of which arc suitable for the purpose, whenfree from seams and metallic veins. Marbleized slateis much superior to the plain
Switchboards for power, light and railway service, direct and alternating current, high and low tension . ck of the board theyshould be so arranged that rain and snow cannot enterthrough them and reach the board, and in damp w^atlierthey should be closed tightly. A perfectly watertightceiling should be constructed over the entire switchboardso as to obviate all danger of injury by water falling fromoverhead. Switchboard fronts are made of marble and marbleizedslate, both of which arc suitable for the purpose, whenfree from seams and metallic veins. Marbleized slateis much superior to the plain stone, as the enamel makesit waterproof. Polished marble is also better than therough stone, on account of the polish rendering the sur-face more impervious to moisture. \Mien there is muchdampness in the air there is a liability of more or lessleakage in the switchboard if the voltage is high. Thiscan be reduced by varnishing the back of the slabs afterthey have been well dried out by heat. Fig. 39 shows the back of a switchboard arranged fortwo generators connected in the three-wire system. The 05. S*) The back of the switchboard. leads from the generators come up through the floorand are made of large flexible cables. As will be noticed,all the bars are supported entirely by the connections
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1906
