File:Electric traction and transmission engineering (1920) (14737278626).jpg

Identifier: electrictractio00shel (find matches)
Title: Electric traction and transmission engineering
Year: 1920 (1920s)
Authors: Sheldon, Samuel, 1862-1920 Hausmann, Erich, 1886-
Subjects: Electric railroads
Publisher: New York : Van Nostrand
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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l scales for ordinatesand abscissae the cotangent of the angle between a por-tion of the curve and a parallel to the axis of abscissaerepresents the corresponding speed in miles per hour. Ifthe elements be straight the speed is constant, and inplotting these curves the average running speed is assumedto be maintained throughout. The perpendicular elementsrepresent stops of durations proportional to the lengths ofthe elements. The ordinate of a point where two curvescross each other gives the time when the correspondingcars meet each other, while its abscissa determines the neces-sary location of a turnout, if the road have but a singletrack. For a specific ptoblem the time-table should haveindicated upon it also the distribution of copper and thelocation of towns, villages, and substations. Confining the attention to a single section of the road,and assuming an average value of current taken by a carwhen running and another greater value when starting, the THE DISTRIBUTING SYSTEM. 149
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3iNIl 11 150 TRACTION AND TRANSMISSION. magnitudes of the currents and the distances from the sub-stations of their points of drainage, corresponding to anychosen time, can be readily obtained. A comparison of theresults for different times readily reveals the worst condi-tion likely to arise. With single-track interurban roadsgiving infrequent train service such condition is Hkely tooccur when and where two trains pass each other. Having determined the worst condition, the adequacy ofthe assumed distribution of copper can be determined bythe method outlined in the preceding section. The mini-mum voltage permissible at the car on 600-volt systems is300 volts, or with high-class service 350 volts. In the case of a supplementary conductor with numerousconnections with a contact conductor which extends between

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