. Electric railway gazette . FIG. shown, the direction of the current inthe outer circuit will be automa tically changedat the proper time. In Fig. 28 th e coil is in oneof its neutral positions. Just before this D hasbeen in contact with «i and E with n\ the currentat that time was flowing from n through E G Dioin. When the coil has arrived at the vertical po-sition shown in Fig. 28, there is no electromotiveforce generated, but just after it has passed thisposition the section n passes from under brush Eand section in passes from under brush D. There-fore brush E rests upon sect
. Electric railway gazette . FIG. shown, the direction of the current inthe outer circuit will be automa tically changedat the proper time. In Fig. 28 th e coil is in oneof its neutral positions. Just before this D hasbeen in contact with «i and E with n\ the currentat that time was flowing from n through E G Dioin. When the coil has arrived at the vertical po-sition shown in Fig. 28, there is no electromotiveforce generated, but just after it has passed thisposition the section n passes from under brush Eand section in passes from under brush D. There-fore brush E rests upon section m and brush Dupon section n. Fig. 29, just as the direction ofthe electromotive force in the coil changes, so thatthe current will continue to flow in the same di-rection in the circuit E O D as before. This arrangement, by which the alternatingcurrent is changed to one always flowing in the. FIG. 26. same direction, is termed a commutator, and theline joining the positions of the brushes where thechange of direction or commutation takes placeis called the axis of commutation. We have already accomplished part of our pur-pose, but not all, for while the current now alwaysflows in the same direction it is an exceedinglyunsteady one, having atone time no electromotiveforce at all and at others a maximum. We musthave a more uniform current, and to this end letus add another coil at right angles to the 30. If this second coil is added and the commutatorsplit into four sections the currents in both col Iswill be rectified and as the coil h is in its neutralposition while coil c is generating its maximumelectromotive force and vice versa, there will beno time when the circuit is without current, forwhile coil h is contributing nothing, the othercoil c is doing its best. Referring to the cut itwill be seen that each coll will come into actionwhen it comes within 45 deg
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Keywords: ., bookcentury1800, bookdecade1890, bookidelectricrail, bookyear1895
