Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. . Fig. 65. Sprague-General Elec-tric Current Limit Relay 161 66 ELECTRIC RAILWAYS from the motor circuit diagram in connection with the contactortable. The master controller is somewhat different from that pre-viously described, in that the reverse direction of the reverser issecured by a m
Cyclopedia of applied electricity : a general reference work on direct-current generators and motors, storage batteries, electrochemistry, welding, electric wiring, meters, electric lighting, electric railways, power stations, switchboards, power transmission, alternating-current machinery, telegraphy, etc. . Fig. 65. Sprague-General Elec-tric Current Limit Relay 161 66 ELECTRIC RAILWAYS from the motor circuit diagram in connection with the contactortable. The master controller is somewhat different from that pre-viously described, in that the reverse direction of the reverser issecured by a motion of the master controller handle in the oppositedirection from that which produces forward motion. The diagramshows four forward positions of the master controller—two eachon series and parallel—and two reverse positions. A much greater use of the interlock principle is used in theautomatic control and it is upon this feature that the student shouldconcentrate particular attention. ]\Iost of the auxiliary switchesused have four pairs of contacts, the purposes of which will be ex- j—-jJinnP—e=3-r r-O O-J ?mi COA/Tpoz ciKun. Fig. 66. Diagram of Interloclcs, Sprague-General Electric Automatic Control plained. The number of these at first appears confusing but, asthe same general principle underlies the operation of them all, thiscomplexity is only apparent. The operating principle of the automatic acceleration will bestudied with the aid of Fig. 66. In this figure are represented threecontactors, each with four pairs of auxiliary contacts. These con-tactors, when closed, cut out sections of resistance grids and thusincrease the current in the motor circuit. The purpose of the schemeis to have these contactors close automatically one after the other,with sufficient intervals between to allow the increasing countere. m. f. of the motors to keep down the current. This is as if a motor-man, in rotating an ordinary cylinder controller handle, were com- 162 ELECTRIC RAILWAY
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