TransactionsPublished under the care of the General Secretary and the Treasurer . of the surface is about the width of one lamination ^ greaterthan the width of the brush b^; consequently, we must substitutein the formula for P^ox > &i + y^ instead of h^. It becomes v/2~ T> . *i + /^ ^ — -m ^ _ Jr sin — — ^fc 2 In order to avoid short circuit between tlie brushes, one mustalways make the brushes at least one laminations width smaller 2 T than the mth part of the double pole distribution —- m 870 Hence, ARNOLD AND LA COUR: COMMUTATION. If we substitute this value in the equation for Pmaxy
TransactionsPublished under the care of the General Secretary and the Treasurer . of the surface is about the width of one lamination ^ greaterthan the width of the brush b^; consequently, we must substitutein the formula for P^ox > &i + y^ instead of h^. It becomes v/2~ T> . *i + /^ ^ — -m ^ _ Jr sin — — ^fc 2 In order to avoid short circuit between tlie brushes, one mustalways make the brushes at least one laminations width smaller 2 T than the mth part of the double pole distribution —- m 870 Hence, ARNOLD AND LA COUR: COMMUTATION. If we substitute this value in the equation for Pmaxy we obtainfor the amplitude of the mean potential curvo P. < 1-15 P.« m = 6 Pmax < P. cZ). Tlie currents generated hy ihe mean potential curve. The situation of the sine curve relative to the connected seg-ments depends on tlie position of the brushes. If the vertex ofthe potential curve is displaced towards the middle of the seg-ments by tlie angle «, Fig. 58, one may decompose the sine curve Jmftt ^. Fig. 58. Mean Potential Curve of Hey-land commutatob. into two others, of which one has the amplitude Pmax coea andthe other the amplitude Pma^ sin or. The vertex of the firstcoincides with the middle point of the laminations, while the ver-tex of the second curve in the middle point of the laminationspasses through zero. The sine curve with the amplitude Pmax cosoc furnishes theexciter current of the generator. In order to calculate exactlyits , one must first obtain the course of the currents in all ARNOLD AND LA COUR: COMMUTATION. 871 parts of tlie winding, Fig. 59, which is effected in the sameway as are calculated the currents in a S3s^;em of mains. Forthe sake of simplicity, let us suppose that the four parallelbranches are not electrically connected with each other, then itis sufficient to calculate a mean potential for the connected lami-nations. If we have, for example. Fig. 59, four current-bearing
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