TransactionsPublished under the care of the General Secretary and the Treasurer . ok at the subject of designing in a broad wayand he has written much about it, where, instead of considering thelesigning of individual machinery, he gives the principles which governthe design of different lines and types, as he has here. I have gainedmuch from Mr. Hobart, not always by accepting his ideas, but by sug-gestions which have resulted from them. The following paper was then read by title, whereupon the Sectiondissolved nftor a vote of thanks, by acclamation, to the Chairman and tothe Acting Chairman
TransactionsPublished under the care of the General Secretary and the Treasurer . ok at the subject of designing in a broad wayand he has written much about it, where, instead of considering thelesigning of individual machinery, he gives the principles which governthe design of different lines and types, as he has here. I have gainedmuch from Mr. Hobart, not always by accepting his ideas, but by sug-gestions which have resulted from them. The following paper was then read by title, whereupon the Sectiondissolved nftor a vote of thanks, by acclamation, to the Chairman and tothe Acting Chairman of the Section, THE COMMUTATION OF DIKECT AND ALTER-NATING CURRENTS. BY PROF. E. ARNOLD and J. L. LA COUR, Electroteclmical Institute, Karlsruhe. I. COMMUTATION IN DIEECT-CUJtRENT MACHINES. 1. The Closed-Circuit Direct-Current Wixdixq. Nearly all direct-current machines are built nowadays withclosed-circuit armature windings. The simplest of these wind-ings is the Pacinotti spiral winding to which every other re-en-trant or closed winding may be referred. Fig. 1 shows the two-. FiG. 1. Paci>*otti Ring Winding. pole plan of this type of winding. Between the brushes B^ andB2 the same number of turns is always included; the inducedin each of these turns has the same curve-form as the field. Con-sequently, for the indicated position of the armature there isinduced in each coil a momentar} , which is determined fromVol. 1 — 51 [801] 802 ARNOLD AND LA COUR: COMMUTATION. the field-curve, Fig. 2a, by the position of the coils in the the coils are distributed equally over the armature, a voltageis obtained vi^hich is equaf to the number of coils times the meanvalue of the induced in a coil during its movement frombrush to brush. If we measure the voltage between one brush,for example, the negative B^^, and different points ol the commu-tators surface, and plot these as functions of the position of therespective point on the commutators surface, we ob
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