. Electric railway journal . ly certain that the efficiency of railroad motors is ashigh as the state of the art will permit with presentcommercial conditions. Mr. Storer took for illustration the losses due tofriction and windage, which he translated into termsof train resistance. He stated that a motor of from40-hp to 50-hp capacity should have approximately 400watts friction loss with a car speed of 10 , corre-sponding to about a 20-lb. train resistance. With a two-motor car, weighing 20 tons, armature friction andwindage amounts to 2 lb. per ton. The axle-bearinglosses would probably
. Electric railway journal . ly certain that the efficiency of railroad motors is ashigh as the state of the art will permit with presentcommercial conditions. Mr. Storer took for illustration the losses due tofriction and windage, which he translated into termsof train resistance. He stated that a motor of from40-hp to 50-hp capacity should have approximately 400watts friction loss with a car speed of 10 , corre-sponding to about a 20-lb. train resistance. With a two-motor car, weighing 20 tons, armature friction andwindage amounts to 2 lb. per ton. The axle-bearinglosses would probably be about one-half as much. Thereare few data available from which gear and axle-bear-ing losses can be determined, but it is hoped that in thenear future further tests will be made which will enablethe standardization committee of the A. I. E. E. to givemore definite figures for the efficiency of axle bearingsand gears. It is possible to use some form of frictionless bear-ing for armatures, but such bearings as yet have not. SAVING ENERGY IN CAR PROPULSION—RHEOSTATIC LOSSESDURING ACCELERATION Pig. 3, parallel control; Fig. 4, series-parallel control; Fig. 5,series, series-parallel, parallel control. Shaded areas show rheo-static losses. had sufficient tests under heavy service conditions tojustify their adoption, especially as the cost is consider-ably higher than the ordinary sleeve bearing. Rheostatic Losses In the matter of rheostatic losses, it is impossible toavoid such losses altogether, but they can be reduced toa much lower amount than has ordinarily been the prac-tice. Figs. 3, 4 and 5 show the relative rheostaticlosses in straight parallel control, standard series-parallel control, and control using full series, series-parallel and full parallel, respectively. In these dia-grams the shaded areas represent rheostatic losses. Iftwo motors are assumed to accelerate with a current togive 10 per cent voltage drop in the internal resistanceof each motor, then, as shown i
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