. Revised and enlarged ed. of the science of railways . mp cannot be readily made for a pressurehigher than about one hundred volts. On theother hand, the cost of conduc-tors for delivering current atone or two hundred volts be-comes very large if the dis-tance be more than a few thou-sand feet. The desirable sys-tem is one in which the energycan be transmitted at highpressure and utilized at lowpressure. The direct currentdoes not admit of any readyand convenient transforma-tion. The alternating current,on the other hand, through theagency of the transformer orconverter, enables this to beacc
. Revised and enlarged ed. of the science of railways . mp cannot be readily made for a pressurehigher than about one hundred volts. On theother hand, the cost of conduc-tors for delivering current atone or two hundred volts be-comes very large if the dis-tance be more than a few thou-sand feet. The desirable sys-tem is one in which the energycan be transmitted at highpressure and utilized at lowpressure. The direct currentdoes not admit of any readyand convenient transforma-tion. The alternating current,on the other hand, through theagency of the transformer orconverter, enables this to beaccomplished. An alternating current trans-former in its essential elementsconsists of two windings, eachof one or more coils of copperwire wound around a core ofiron, usually of thin plates. If one of the windingsor sets of coils be connected to a circuit on whichthe pressure is, say, one thousand volts, an alter-nating magnetism is produced in the iron, which,in turn produces an electro-motive force in theother, or secondary winding. The electro-motive. Three Hundred andSeventy Five Kilowatt(500 horse-power) RaisingTransformer. Wires fromgenerator are connectedto large terminals onmarble block at rear end;wires to high tension line(15,000 voltsj are connectedto terminals at front. Theflat coils are placed sideby side and spread apartat the ends to allow circu-lation of oil between thecoils. ELECTRICITY AS A MOTIVE POWER. 423
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