. Electric traction and transmission engineering . RATE OF BRAKING IN MILES PER HOUR PER SECOND Fig. 55- connection with Fig. 49. The effect on schedule speed andon energy consumption of changes in the rates of accelera-tion and braking is not as conspicuous on long runs ason short ones. ENERGY CONSUMPTION. 129 The schedule speed of railway cars depends to a greatextent upon the duration of the stops for the purpose oftaking on or discharging passengers or freight. Obviously,the longer the period of standstill the lower will be themaximum schedule speed attainable by a given eq
. Electric traction and transmission engineering . RATE OF BRAKING IN MILES PER HOUR PER SECOND Fig. 55- connection with Fig. 49. The effect on schedule speed andon energy consumption of changes in the rates of accelera-tion and braking is not as conspicuous on long runs ason short ones. ENERGY CONSUMPTION. 129 The schedule speed of railway cars depends to a greatextent upon the duration of the stops for the purpose oftaking on or discharging passengers or freight. Obviously,the longer the period of standstill the lower will be themaximum schedule speed attainable by a given equipment. An increase in the time of coasting results in a reductionof the power consumption. The results of a series of recent 50 40 1-30 £20 10 6-CAR MOTOR TONS. <WG. BRAKING MILES PER HR. PER SEC STATION STOP-14 2 3 4 5 6 TIME IN SERIES POSITION, SECON DS. Fig. 56. tests on a 6-car train of the Manhattan Elevated Systemmade by H. S. Putnam are embodied in the curves ofFigs. 54, 55 and 56, which show for a given schedulespeed the influence on the percentage of coasting and per-centage saving in electrical energy, of acceleration andbraking rates, and of running time in series position. The motor performance curves and the speed and powercurves derived from them refer to a definite and constanttrolley voltage. In practice this voltage has not the samevalue at different points on the roadway, owing to the drop 130 TRACTION AND TRANSMISSION. of potential along the trolleys, on third rail, and on feedersfrom the substations. The minimum voltage at the carshould not be less than 350 volts for the usual 600-voltequipment. Consequently in selecting the car equipmentfor a proposed railway service due attention must be givento the voltage regulation on various parts of the road. Speed curves of cars op
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