. Electric railways, theoretically and practically treated . nt value be greater,the motors will be of insufficient capacity and will heatexcessively. If the effective value be smaller than the con-tinuous value, the motors are too large for the given service. Plotting of Theoretical Speed-Time Curve. — Whenplotting speed-time curves for a given motor, the followingdata is essential: The motor characteristic curves, motors operating online voltage, geared in the desired ratio. The profile and general contour of road. The total weight per car, including car body, trucks,motor equipment, control
. Electric railways, theoretically and practically treated . nt value be greater,the motors will be of insufficient capacity and will heatexcessively. If the effective value be smaller than the con-tinuous value, the motors are too large for the given service. Plotting of Theoretical Speed-Time Curve. — Whenplotting speed-time curves for a given motor, the followingdata is essential: The motor characteristic curves, motors operating online voltage, geared in the desired ratio. The profile and general contour of road. The total weight per car, including car body, trucks,motor equipment, control, brake apparatus, and passengerload. The number of motors to a single car equipment. The maximum speed desirable, and the proposedschedule speed between stations. The rate of acceleration and the rate of braking. 38 ELECTRIC RAILWAYS. Examples. — As a specific example of the process of plot-ting a speed-time curve, assume the following data given:Motor Curve Type 8i, Westinghouse Motors (Fig. i6).Four-motor equipment having 33 wheels. 30 15 20 10 1500. 1000 Fig. 16. —CURVES OF TYPE 8i, WESTINGHOUSE MOTOR. Distance between stations, 2,480 feet. Schedule speed, miles per hour. Rate of acceleration and braking, per S. Total train weight, 32 tons. ANALYSIS OF TRAIN PERFORMANCE. 39 Profile and general contour as follows : Prom station A to station B = 2,480 feet. A, first 600 feet, an up gi-ade of 19^. 600 to 1,200 an up grade of i % and a 2° curve. 1,200 to 2,480 feet, level table should be prepared (Fig. 17) representing theequivalent traction due to grades and curves referring toprevious equations. EQUIVALENT TRACTION IN POUNDS PER TON. GRADES. cuRv: ES. NET. Distance. Per CentGrade. Traction due to Grades. Degree ofCurvature. Traction due to Curves. Total Traction in lbs. per ton. 0 to 600 + 1 — 20 0 0 20 to 1,200 + 1 — 20 2° to 2,480 0 0 0 0 0 Fig. 17. If there are several speed-time curves to be plotted,which is usually the case, t
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