. The Street railway journal . tain number of revolutions the numberof poles must be directly proportional to the number of alterna-tions of the supply circuit increasing and diminishing with 262 STREET RAILWAY JOURNAL. [Vol. XXIII. No. 7. them, and that in order to obtain a motor that is simple in itspolar structure, the line alternations must be very low; forinstance, a 700-revolution motor having 2000 alternations perminute must have eight poles. The method by which these motor characteristics are securedis interesting. Both the field self-induction and the armatureself-induction are limite
. The Street railway journal . tain number of revolutions the numberof poles must be directly proportional to the number of alterna-tions of the supply circuit increasing and diminishing with 262 STREET RAILWAY JOURNAL. [Vol. XXIII. No. 7. them, and that in order to obtain a motor that is simple in itspolar structure, the line alternations must be very low; forinstance, a 700-revolution motor having 2000 alternations perminute must have eight poles. The method by which these motor characteristics are securedis interesting. Both the field self-induction and the armatureself-induction are limited by a special construction of the polepieces. Referring to the diagram it will be noted that slots orholes are cut in the pole piece from end to end, parallel to theshaft. These spaces are holes rather than slots, on account ofthe greater magnetizing power required when slots are cross section of the field magnet is such that the principalmagnetic reluctance is found in the air gap and in the teeth of 1 151 14. LAMME MOTOR the field and armature, and the magnetic circuit is so propor-tioned that beyond normal current the teeth in the pole slotsrapidly approach saturation. The self-induction of the armature is, of course, proportionalto the square of its turns and to the permeability of its mag-netic circuit, and that part of the magnetic circuit which is inthe armature itself must have low permeability for the reasonthat it carries the main torque producing flux. The poles of adirect-current armature, which are due to the armature wind-ing, appear between the pole pieces of the field on the surfaceof the armature, and find their return magnetic circuit throughthe structure of the pole pieces from tip to tip, in accordancewith well-known laws and many familiar diagrams. At thispoint Mr. Lamme attacks the integrity of the armature mag-netic circuit, and by means of his slots in the pole pieces he hasevidently contrived to reduce the cross magnetizing of thearmatu
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectstreetr, bookyear1884
