. The street railway review . ndshafting. Bipolar and occasional tour-pole machines were continued asthe standard form up to about 1893. The older machines hadarmatures with surface coils, which were wound on by hand. Thecoils, being merely bound to the surface by layers of wire, ropeor canvas, had very little strength to resist torsional strains. Itwas, moreover, difficult to secure insulation between coils and ovei-the surface of the core, and good ventilation was impossible. It was a distinct step in advance when the Westinghouse com-pany placed the armature coils of its railway generators
. The street railway review . ndshafting. Bipolar and occasional tour-pole machines were continued asthe standard form up to about 1893. The older machines hadarmatures with surface coils, which were wound on by hand. Thecoils, being merely bound to the surface by layers of wire, ropeor canvas, had very little strength to resist torsional strains. Itwas, moreover, difficult to secure insulation between coils and ovei-the surface of the core, and good ventilation was impossible. It was a distinct step in advance when the Westinghouse com-pany placed the armature coils of its railway generators in par-tially closed slots on the periphery of the core. A tube of insula-tion was slipped over each conductor, giving perfect insulation,but not diminishing the difiiculty of winding. In 1892 the companyused bar windings, the bars being pushed through the core slotsand soldered to end connections. Strap-wound coils, prepared separately from the machine, andplaced in open slots on the armature surface, were a further distinct. LARGE SIZE LAWRENCE, PARIS & SCOTT DYNAMO— horseshoe field niajjnets of cast iron—Pacinolti drum armature. advance. Tin sc coils were held in place by wedges, driven intoyrooves ill the core. This gave perfect insulation, the coil as awhole being wound with insulating material; and the coil wasfurthermore well ventilated; also wires having a high poleiiliaidifference were well separated. This is considered to give muchbetter insulation than the so-called trough construction whichgives short distances from core to coil at ends, while the upperand lower parts of the coils are not in separate wrappings ofinsulation, as is customary in the fonuer method. In 1894 the Westinghouse company also began to use bar wind-ings in which a complete coil of forged copper bar, formed bymachinery and wrajiped with insulation, was laid in slots in theai mature cfire and held by wedges. During the first decade of the electric railroads, we have seenthat the pr
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
