. Electric traction and transmission engineering . l the motor cars and thus establish similar motor con-nections on them. To avoid accidents which may occurthrough the physical disability of a motorman, the operat-ing handle of the master controller is sometimes providedwith a button which must be held down in order to keepthe auxiliary control circuit closed. In some cases the con-nections are so arranged that releasing this button appliesthe air brakes as well as opens the control circuits. RAILWAY MOTOR CONTROL. 107 The essential features of the multiple-unit system ofcontrol as applied to
. Electric traction and transmission engineering . l the motor cars and thus establish similar motor con-nections on them. To avoid accidents which may occurthrough the physical disability of a motorman, the operat-ing handle of the master controller is sometimes providedwith a button which must be held down in order to keepthe auxiliary control circuit closed. In some cases the con-nections are so arranged that releasing this button appliesthe air brakes as well as opens the control circuits. RAILWAY MOTOR CONTROL. 107 The essential features of the multiple-unit system ofcontrol as applied to direct-current equipments are illus-trated in Fig. 48, which shows the^ principal motor andcontrol circuits for one motor car. For clearness the re-verser is omitted, as are also the circuits necessary for itscontrol. Assuming therefore that the reverser is properlyset, the subsequent operation of the control system duringinitial acceleration is as follows: turning one of the mastercontrollers to the first notch results in the closing of contac-. Fig. 48. tors a, b, and //, due to current received from train wires i,2, and 8, thus establishing connection with the line andplacing the two motors and a protecting resistance inseries. Turning the master-controller handle successively tonotches 2, 3, and 4 closes contactors c, d, and e, respectively,thereby progressively reducing the resistance by placingadditional resistance units in parallel. When the controllerhandle is moved to the fifth notch, contactor / is closed, Io8 TRACTION AND TRANSMISSION. short-circuiting the resistances and connecting the motorsin series across the Hne. In passing over the sixth or tran-sition notch contactors ^ to / and h are opened, followed bythe closing of contactors g and i. This places the motorsin parallel, with resistance in series with both. Turningthe master-controller handle successively to notches 7, 8,9, and 10 progressively reduces the resistance as beforeuntil each motor is operating on
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Keywords: ., bookcentury1900, bookdecade1920, bookidelectrictrac, bookyear1920
