Electro-dynamics: The Direct-current MotorLongmans Green and Company, 1898 - 298 páginas |
Otras ediciones - Ver todas
Términos y frases comunes
100 amperes 45 amperes accelerating current acceleration curve armature axis brushes cent centimetres circuit connected in series current curve current per motor diagram diameter difference distance travelled driving wheel dynamo eddy current equal Example expenditure of energy f.p.s. per second feet per second final speed find the induction foot-pounds force factor frictional torque full speed gearing given distance gives greater Hence horizontal horse-power hysteresis increase induced tension induction curve line watts lines of force lines per pole load machine magnetic circuit MAGNETISATION CURVES main shaft maximum current mechanical efficiency mechanical watts miles an hour miles per hour motor shaft obtained pole-tip pounds railway motor reduced represent resistance to motion revolutions per minute revolutions per second running series-wound motor speed curve starting rheostat Suppose surface conductors terminal tension tion tons torque curve torque loss total current total torque tractive effort velocity ratio volts weight
Pasajes populares
Página 25 - ... heat are those of molecules, and are so numerous, so small individually, and so irregular in their distribution, that they quite escape all our methods of observation ; whereas when the motions and displacements are those of visible bodies consisting of great numbers of molecules moving all together, the communication of energy is called work. Hence we have only to suppose our senses sharpened to such a degree that we could trace the motions of molecules as easily as we now trace those of large...
Página 25 - ... acted on by forces having potentials. The second law relates to that kind of communication of energy which we call the transfer of heat as distinguished from another kind of communication of energy which we call work. According to the molecular theory the only difference between these two kinds of communication of energy is that the motions and displacements which are concerned in the communication of heat are those of molecules, and are so numerous, so small individually, and so irregular in...
Página 89 - ... of two electric-motors coupled in such a way as to admit of their rotating at different speeds. The two shafts are placed in line, and each is fitted with a bevel-wheel, gearing into an intermediate wheel. The axis of the intermediate wheel is at right angles to the line of the motor-shafts, and is free to rotate in a plane at right angles to that line. The motors can be made to rotate at different speeds by altering the strength of the magnets of either or both. The motion of the intermediate...
Página 268 - Fig. 7; point the forefinger in the direction of the lines of force, the thumb in the direction of the motion of the wire, then the middle finger will point in the direction of the induced emf 11.
Página 245 - Prof, cams- the heat watts is divided by the tension of the line, we obtain the part of the total current that represents the loss due to heat When the current representing the heat loss has been deducted from the total current at any instant, the remainder represents the expenditure of energy in producing acceleration and overcoming train resistance. The proportion of these two can be obtained from the curve of total torque, since that tells us how much is being used for accelerating, and how much...
Página 250 - ... of series - parallel control is to halve the heat lost. As an illustration of the application of these principles to the heavier class of railway work we may take the Metropolitan Elevated Railroad of Chicago. Particulars of this railway have been given by Mr. MH Gerry, and may be found in a paper published in the Proceedings of the American Institute of Electrical Engineers for 1897. The rolling stock consists of motor cars and passenger cars. The former measure 47 feet in length, and weigh...
Página 220 - W(EC/R)3 ... (14) It appears, then, that, when a train of weight W tons has to be started from rest and moved through a distance of D feet, the tension of the line being E volts, the accelerating current c,, amperes, and the internal drop when running at full speed c...
Página 43 - If the current flows in a circular path, then if we imagine the fingers of the right hand curving in the direction of the current, the thumb will point in the direction of the magnetic field inside the coil (see Figure 25-4).
Página 234 - ... will rapidly diminish ; the form of the curve has been calculated and plotted in the figure. We must now consider the influence of series winding on the curves of current and acceleration. In Fig. 6, let values of the current be measured horizontally, and values of the induction factor be measured vertically. Take ah equal to 15 amperes, and set up hb equal to 35'5 on the vertical scale. Then b is a point on the induction curve of the motor. For, whatever are the values of M for large currents,...
Página 52 - If the radius of the wheel is 18.7 in., what is the velocity in feet per minute of a point on the circumference?