. Electric railways, theoretically and practically treated . tube,threaded at both ends to receivenuts to hold the segments in posi-tion. Mica is used for insulatingpurposes, as it has high insulatingproperties, and wears under theaction of the brushes at about thesame rate that the copper does. Thismaintains at all times a smooth sur-face upon the commutator. Themaximum voltage between commu-tator segments seldom exceeds 20volts. Assuming that the voltageis uniformly distributed, a 500 voltmachine with a closed series windingwould then possess 25 bars betweenadjacent poles, or for a four pole
. Electric railways, theoretically and practically treated . tube,threaded at both ends to receivenuts to hold the segments in posi-tion. Mica is used for insulatingpurposes, as it has high insulatingproperties, and wears under theaction of the brushes at about thesame rate that the copper does. Thismaintains at all times a smooth sur-face upon the commutator. Themaximum voltage between commu-tator segments seldom exceeds 20volts. Assuming that the voltageis uniformly distributed, a 500 voltmachine with a closed series windingwould then possess 25 bars betweenadjacent poles, or for a four pole machine 100 bars. 55 railway motor has 141 commutator segments, 64 motor 105 bars, the 1,000 motor 93 bars,the Westinghouse 50 E motor 165 bars, the Westinghouse56 motor 117 bars, the motors of greater capacity havingthe greater number of segments. A large number of com-mutator segments is desirable for a railway motor to pre-vent flashing over of the commutator, which sometimesoccurs when the motor circuit is momentarily Fig. 32.— FORMEDARMATURE COIL. 68 ELECTRIC RAILWAYS. The terminals of the armature conductors are usuallysoldered into projections of the commutator in practice, when repairing armature coils, a
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorkvannostrand
