. Un testo-libro di ingegneria elettrica;. 450 3-18.10* 14-6 20 490 3-46.106 21-3 25 505 3-56.106 motore 27-3 la £ = 500 - 2-75 . 7„ giri/min = 3-18.106.1 5 486-2 970 10 472-5 590 15 4587 460 20 445 410 25 431-2 390 220 Electrical Engineenng per mezzo di queste cifre abbiamo can.determine la velocità alla quale un trampardel peso determinato salirà una data pendenza, così come la corrente presa indoing così. Sia p(7 ijg ^j^g peso della vettura in tonnellate metriche (i tonnellate metriche = looo kg*),/il coefficiente di trazione, cioè la forza in kg necessaria per muovere l'onetone a velocità costante sul livello,e s la pendenza o la pendenza

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. A text-book of electrical engineering;. 450 3-18.10* 14-6 20 490 3-46.106 21-3 25 505 3-56.106 Motor 27-3 la £ = 500 - 2-75 . 7„ r.p.m. = 3-18.106.1 5 486-2 970 10 472-5 590 15 4587 460 20 445 410 25 431-2 390 220 Electrical Engineenng By means of these figures we can.determine the speed at which a tramcarof given weight will ascend a given incline, as well as the current taken indoing so. Let p(7 ijg ^j^g weight of the car in metric tons (i metric ton = looo kg*), /the tractive coefficient, i.e. the force in kg required to move oneton at a steady speed on the level, and s the slope or gradient in parts per thousand; then the pull required on the level will be W .f. On the slope, the weightAB (Fig. 203) acting vertically downwards can be resolved into two com-ponents, one normal to the surface and the other AO, which has to be directlyovercome by the tractive pull. We have from the figure AO = AB.sm^. If we substitute for sin ^ its value 1000 and for AB the weight of the car in kilogrammes, we have AO = xoooW.^ = W.s.1000. The pull on the car must therefore be given by the formula F = W.f+ W.s= l^{/+s)kg*.If the radius of the car-wheels be r metre, the torque on the axles must^^ F.r=W{f+ s) .y met.-kg. If the gear is such that the motor runs k times as fast as the car axles, thetorque of the motor, by the conservation of energy, must be a ^th part ofthat on the axles. If we assume, further, that the gearing has an efficiency7], we obtain the following formula for the total torque of all the motorson the car: p ^ W.r.(f+s) h. 2M, = In our present example the radius of the wheels was 0-39 metre and theratio of the gearing 4-9. If we assume that the weight of the car is 8 tonsand the tractive coefficient 12 kg per ton, we have YM - ^ • °^^ • ^^^ ^ ^^ ^ °^^^ • ^^^ ^ ^^4-9.77 ij * See footnote on page 4^. 68. Example of Traction Motor Calculation 221 In our case, as is almost universal, each car was provided with twomotors, so that each motor had to produce hal

Parole chiave associate all'immagine

• bookcentury1900
• bookdecade1920
• bookidcu3192400440
• bookyear1920