Electric engineering. (1902) (14774181121)

Identifier: electricengineer03inte (find matches)
Title: (Electric engineering.)
Year: 1902 (1900s)
Authors: International Library of Technology
Subjects: Electrical engineering
Publisher: Scranton, International Textbook Co.
Contributing Library: UMass Amherst Libraries
Digitizing Sponsor: Boston Library Consortium Member Libraries



Text Appearing Before Image:
systems so faras actual operation is concerned, the chief point in favor ofthe three-phase system being the saving in line wire. 67. Substations.—In many large transmission systems,it is customary to generate the power in one large centralstation and distribute it at high pressure to a number ofsubstations located at the various distributing centers. Atthese substations the current is transformed down and passedthrough rotary transformers, if direct current is necessary,and distributed to the various devices to be operated. Thisis commonly done in connection with both lighting andstreet-railway work. If alternating current alone is used,the voltage is merely stepped down by means of large trans-formers. Perhaps one of the best examples of three-phasetransmission is that of the Metropolitan Street Railway Com-pany, of New York. Most of the surface cars in New YorkCity are operated by direct current, at 500 to 600 volts, sup-plied to the cars by means of conductors placed in a conduit
Text Appearing After Image:
r ill hi ■ ii hi I <=■■ L. ... ..LiB § U ELECTRIC TRANSMISSION. 55 between the rails. Power is generated at one large centralstation located on the river front, where coal and water areeasily supplied. Large 3,500-kilowatt three-phase gener-ators are located in this station. They are of the revolving-field type and are driven directly by large, vertical Corlissengines. These machines generate current at a pressure of6,600 volts, so that no step-up transformers are used. Thecurrent is led from the main station by means of lead-coveredunderground cables to a number of substations located indifferent parts of the city. These substations contain thestep-down transformers and rotary transformers that arenecessary to convert the three-phase current into a directcurrent of 500 volts suitable for operating the street cars.Each of the rotary transformers is of 900 kilowatts capacity,and before sending the current into rotaries, it is trans-formed to six phases, as the increased numbe