[Electric engineering.] . e dynamos to enablethem to charge the batteries. In railway work, where theload fluctuates very rapidly, the booster is so constructed asto make the battery discharge when the load is heavy andcharge up when it is light. In lighting plants, the booster isusually shunt-wound or compound-wound and is driven by amotor. Fig. 71 shows one scheme of connections. Only theessential parts are here shown, so as to illustrate the principlesinvolved without confusing the diagram with the variousinstruments and switches. For this reason, also, a simpletwo-wire system is illustrate
[Electric engineering.] . e dynamos to enablethem to charge the batteries. In railway work, where theload fluctuates very rapidly, the booster is so constructed asto make the battery discharge when the load is heavy andcharge up when it is light. In lighting plants, the booster isusually shunt-wound or compound-wound and is driven by amotor. Fig. 71 shows one scheme of connections. Only theessential parts are here shown, so as to illustrate the principlesinvolved without confusing the diagram with the variousinstruments and switches. For this reason, also, a simpletwo-wire system is illustrated. G is the generator supply-ing current to the lamp load L. A is the battery and B anumber of cells at one end, from which connections arebrought out to terminals c. A sliding contact d makes con-nection between contacts c and the bar e, so that by sliding d,the number of effective cells and, hence, the voltage of thebattery may be increased or decreased as desired. Thisarrangement is known as an end-cell switch, and the. c A 3 0 t)Lo°rf Fig. 71. cells B are called end cells. Fis a single-pole double-throwswitch, by means of which the battery may be connectedacross G in series with the booster or directly across theline. In the figure, the switch is thrown up, as indicatedby the dotted line, and the battery is being charged, because 76 ELECTRIC LIGHTING. § 17 the voltage generated in the booster armature is added tothat of the generator. When F is thrown down, the batteryA discharges into the line and the voltage may be regulatedby means of the end-cell switch. 65. In lighting installations, the necessary regulationcan easily be effected by means of end-cell switches, becausethe load does not fluctuate with great rapidity, as in railwaywork. In most large plants, two end-cell switches are pro-vided in parallel, as indicated in Fig. 71, the second switchbeing shown dotted. This allows two different voltages tobe taken from the battery, or in case of heavy loads the twoswitche
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