TransactionsPublished under the care of the General Secretary and the Treasurer . the commutator II, III are the brushes, to which the three-phase exciting andcompounding current is directly supplied. Of special interest is the theoretical process of commutationand the preliminary calculations of the resistance of the cross-connections. These latter can be calculated in a very completeand exact manner, and it is shown that, with a certain resistanceof the cross-connections, the commutation voltage and the short-circuit currents of c(;mmutation become nil. If then the resistanceis c
TransactionsPublished under the care of the General Secretary and the Treasurer . the commutator II, III are the brushes, to which the three-phase exciting andcompounding current is directly supplied. Of special interest is the theoretical process of commutationand the preliminary calculations of the resistance of the cross-connections. These latter can be calculated in a very completeand exact manner, and it is shown that, with a certain resistanceof the cross-connections, the commutation voltage and the short-circuit currents of c(;mmutation become nil. If then the resistanceis chosen too large, a short-circuit current is produced in the one 766 HEYLAXD: COMPOUNDED ALTERNATORS. direction; if it is chosen too small, in the other direction. Thatis to say, with a certain resistance of these cross-connections thecommutation voltage becomes equal to zero. Even from this pointof view the commutation in the present arrangement would bemore ideal than the commutation in direct-current machines, inwhich, as is known, the commutation voltage can be brought only. Fig. 2. to a minimum value, and never to zero without displacing thebrushes. On the other hand, we should emphasize the fact thatthis ideal commutation is not practically obtained here, for thefield pulsations and other conditions have as effect a certain com-mutation voltage. However, the result is theoretically very inter-esting in so far as it shows that there is for the cross-connectionsa certain most favorable resistance, with which the commutation HEYLAND: COMPOUXDED ALTERyATORS. 767 becomes a theoretically complete one. From a practical stand-point we then need only to adhere to practical experience, whichwill show to what brush voltage Ave can go with a given sub-division. The calculation is made in the following manner:Let us consider Fig. 1. Brush II is in the commutating position,that is, the position in which the brush bridges the dummy seg-ments and thus connects the beginning and the end of
Size: 1574px × 1588px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookidtr, booksubjectelectricity
