Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . points diametn- ^P : ;—p—7 r n ., J2Z Leads r-oh-m. cally opposite fgv i-ohm and connected (£*^~rom ? 2,-oli-ms one to each col- ]^lL 3-amperes. lector ring. With Fig M. F. and P. D. of an Armature,the increased number of coils the alternating E. M. F. is increased, since theE. M. in the coils at any instant are in unison. The com-mutator and collector rings may both be mounted on thesame armature shaft, when the machine will give either adirect or alternating current, or
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . points diametn- ^P : ;—p—7 r n ., J2Z Leads r-oh-m. cally opposite fgv i-ohm and connected (£*^~rom ? 2,-oli-ms one to each col- ]^lL 3-amperes. lector ring. With Fig M. F. and P. D. of an Armature,the increased number of coils the alternating E. M. F. is increased, since theE. M. in the coils at any instant are in unison. The com-mutator and collector rings may both be mounted on thesame armature shaft, when the machine will give either adirect or alternating current, or both, at the same time to two 350 PRACTICAL ELECTRICITY. independent circuits. The dynamo would then be called adouble current generator. The collector rings would be con-nected one to each diametrically opposite section of the com-mutator ; for example, 1 and 5 in Fig. 324. 328. Siemens Drum Armature.—Instead of winding thearmature coils upon a laminated ring, they are sometimes. Fig. 329. -Multi-Coil Siemens Drum pattern. wound upon a cylindrical laminated iron core made by as-sembling, upon the armature shaft, thin sheets of soft iron;after being properly insulated the coils are wound upon thecore, and connected in series and to the commutator in the same manner as that given forthe ring armature. Fig. 330depicts a four-coil Siemensdrum armature with its com-mutator, suitable for a bipolarfield. In practice a greatmany coils are wound uponthe core covering its entirearea, the commutator sectionsincreasing with the sub-division of the armature induced E. M. F. in thatpart of a coil under one pole isin the opposite direction tothat in the other half of thecoil so that the two E. M. are in series, as in two consecu-tive coils in the ring armature. Both halves of the drumarmature coils are in parallel with the external circuit so that
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1901
