TransactionsPublished under the care of the General Secretary and the Treasurer . /3ro sec. Je= iJi= 5 = 10^ Henry n—1470. ^A:^^^^eo. Fig. 35. exponential curve. With large self-inductions and surface veloci-ties, on the contrary, in which the breaking of the current is ac-companied by sparks, the curve, according to which the currentdisappears, is quite deformed. This appears plainly from theoscillograms. Concerning the voltage curve h, this runs horizontal as long asthe current is nil. When the current begins to increase, the volt-age between brush and commutator sinks slig
TransactionsPublished under the care of the General Secretary and the Treasurer . /3ro sec. Je= iJi= 5 = 10^ Henry n—1470. ^A:^^^^eo. Fig. 35. exponential curve. With large self-inductions and surface veloci-ties, on the contrary, in which the breaking of the current is ac-companied by sparks, the curve, according to which the currentdisappears, is quite deformed. This appears plainly from theoscillograms. Concerning the voltage curve h, this runs horizontal as long asthe current is nil. When the current begins to increase, the volt-age between brush and commutator sinks slightly, owing to thedrop of voltage in the inserted resistance R^. If the currentdisappears, the voltage again increases rapidly and, with largeself-inductions, passes be^^ond the limits of the impressed two*oscillograms. Figs. 34 and 35, were recorded under almost Fig. 34a. J J J J J J J J JJJy J J J Fic:. M^ Fig. 47a. I — S37 ARNOLD AXD LA COVR: COMMUTATION. 837 ft the same conditions. However, the tips of the voltage curve, atthe moment of opening, show a somewhat different is caused only by the processes which at the moment of de-livery take place at the brush points. As is evident, the voltage at the moment of opening can riseto times the amount of the impressed voltage. Since theseexcesses of voltage originate in the released energy, it is obviousthat this voltage is the direct cause of the spark formation. 9. The Energy Eeleased at the Disappearance of theAdditional Current, At the disappearance of the additional current the electromag-netic energy i il max S is released; this can be transformed neitherinto mechanical nor chemical energy; it must, therefore, pass overinto heat. This occurs naturally at the place where the currentis broken, that is, under the brush tips. When this release ofenergy is either excessive, or occurs too rapidly, sparks , the
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