File:The Street railway journal (1903) (14572982377).jpg

Identifier: streetrailwayjo221903newy (find matches)
Title: The Street railway journal
Year: 1884 (1880s)
Authors:
Subjects: Street-railroads Electric railroads Transportation
Publisher: New York : McGraw Pub. Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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cuit steadies any fluctua-tions and furnishes a reserve in case of a breakdown. In this waythe running of the auxiliaries, the excitation of the generatorsand the lighting of the plant are made entirely independent of themain current supply. Division Into Units.—Large alternating current city plants asat present installed represent a vast quantity of power under oneroof. Any accident which might cripple the plant would havevery serious results, and affect a large number of people and in-dustries. The greatest care should be taken to avoid such a pos-sibility. In order to prevent, as far as possible, the crippling ofthe entire plant by an accident to any part of it. some of the morerecent installations have been divided into units, each unit con-sisting of a generator, engine and condenser, together with thenecessary number of boilers to furnish steam for the engines andthe auxiliaries in connection with the boilers. It is intended that 5o8 STREET RAILWAY JOURNAL. (Vol. XXII. No. it.
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each unit shall be independent ofany other; in fact, there will be asmany separate power plants as thereare units. An emergency steamconnection is made between thesteam headers, but for emergencyuse alone. The unit method mini-mizes the danger of a completeshut-down of the plant, but theprice paid for it is the greateramount of reserve apparatus neces-sary, and also a somewhat poorereconomy if the unit idea is carriedout in detail as to feeders and sub-stations. Frequency.—By common consenta periodicity of 25 cycles per sec-ond has been adopted in the UnitedStates for alternating currentpower work. In Europe thereseems to be no fixed standard, eachinstallation following the ideas ofits designer. Rotary converterswork better at low frequency, andin a combined railway and light-ing plant where alternating currentlighting is to be done it is best togenerate at 25 cycles, use rotaryconverters at this periodicity forthe railway and direct-currentlighting, and install motor gen-erators to

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