Original Papers on Dynamo Machinery and Allied SubjectsW.J. Johnston, 1893 - 249 стор. |
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abscissæ alternate current machines Amperes angle apparatus armature armature core brushes calorimeter carbons cent centimetre Chance Brothers characteristic curve coefficient column commutator conductor connected constant convolutions copper coupled current passing Deflection determined diagram diameter difference of potential dynamo machine dynamo-electric machine dynamometer effect efficiency electric arc electric current electric light electromotive force energy engine equation experiments external circuit galvanometer given gives Gramme machine Hence horizon horse power incandescent induction integral of magnetic lamp lens lighthouse line integral loss magnet coils magnet limb magnetic field magnetizing force maximum mean measured mechanical motor observed obtained open circuit ordinates pole pieces positive potential difference produce pulley represents resistance revolutions per minute short circuited Siemens speed square temperature Thick Coil tion transformer velocity volts waste field watts wire yoke
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Сторінка 101 - The currents in the fixed coils around the magnets are not the only magnetising forces applied in a dynamo machine; the currents in the moving coils of the armature have also their effect on the resultant field. There are in general two independent variables in a dynamo machine, the current around the magnets and the current in the armature, and the relation of EMF to currents is fully represented by a surface. In well-constructed machines the effect of the latter is reduced to a minimum, but it...
Сторінка 60 - All but the first two arrangements named depend on residual magnetism to initiate the current, and below a certain speed of rotation give no practically useful electromotive force. A dynamo machine is, of course, not a perfect instrument for converting mechanical energy into the energy of electric current. Certain losses inevitably occur. There is, of course, the loss due to friction of bearings, and of the collecting brushes upon the commutator; there is also the loss due to the production of electric...
Сторінка 147 - ... machines, independently driven, it is not quite obvious what the result will be, for the polarity of each machine is constantly changing. Will two machines, coupled together, run independently of each other, or will one control the movement of the other in such wise that they settle down to conspire to produce the same effect, or will it be into mutual opposition ? It is obvious that a great deal turns upon the answer to this question, for in the general distribution of electric light, it will...
Сторінка 37 - A represents the current which will pass if the lamp be prevented from operating. Let ON represent the current to which the lamp is adjusted; then if the abscissa of A be greater than ON, the carbons will part. Through N draw the ordinate BN, meeting the curve in the point B ; and parallel to OA draw a tangent CD, touching the curve at D. If the point B is to the right of D, or...
Сторінка 184 - Fio. 3. induction be deduced on the assumption that the induction is a simple harmonic function of the time, results may readily be obtained vastly in excess of the truth.
Сторінка 75 - ... gas engine driving a dynamo, and using the electricity in the ordinary way in incandescent lamps, we can obtain more than 5 candles per cubic foot of gas, a result you would be puzzled to obtain in 16-candle gas burners. With arc lights instead of incandescent lamps many times as much light could be obtained. At the present time, lighting by electricity in London must cost something more than lighting by gas. Let us see what are the prospects of reduction of this cost ? Beginning with the engine...