. A textbook on electric lighting and railways. International correspondence schools, Scranton, Pa. v. 1-3, 5 . 71. Pole Pieces.—The motor has four poles ])rovidedwith flanged pole pieces that are laminated ; the flanges serveto hold the field coils inplace, and the lamitions not only do awaywith a great deal of heatin the pole piece, butfrom the way in whichthey are built up, theyproduce a magnetic fieldthat does away withmuch of the sparkingat the brushes. Thepole pieces are madeof iron plates shaped. 66 ELECTRIC RAILWAYS. 24 something- like the full-line part of Fig. 47 (/). The polepieces
. A textbook on electric lighting and railways. International correspondence schools, Scranton, Pa. v. 1-3, 5 . 71. Pole Pieces.—The motor has four poles ])rovidedwith flanged pole pieces that are laminated ; the flanges serveto hold the field coils inplace, and the lamitions not only do awaywith a great deal of heatin the pole piece, butfrom the way in whichthey are built up, theyproduce a magnetic fieldthat does away withmuch of the sparkingat the brushes. Thepole pieces are madeof iron plates shaped. 66 ELECTRIC RAILWAYS. 24 something- like the full-line part of Fig. 47 (/). The polepieces are built up of these plates, every other one of whichis turned end for end. The result of this manner of con-struction is shown in Fig. 47 (a), where, along the horizontalcenter part of the pole piece, the plates are close together,but on the horns only half of the plates come out on eachside. This plate construction, to a great degree, does awaywith sparking at the brushes, because the thinning out ofthe metal on the horns of the pole pieces produces what \\^A z. sJiaded field or fringe. This means that the pole-piece horns are so made that the lines of force are distributedin such a way that they gradually become thinner and thin-ner at the proper rate and in the right place. This shadedfield provides a fringe that reverses the current in thecoil passing under the brush, and hence brings about thechange in the direction of the current with but little sparking. 73. Field Coils.—The fie
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectelectri, bookyear1901
