GB191413231A - Improvements in and relating to Systems of Control for Electric Motors. - Google Patents

Abstract

13,231. British Thomson-Houston Co., [General Electric Co.]. May 29. Systems for continuous-current motors only.-In a series-parallel system for a number of pairs of electric motors, two series resistances are cut out during starting by contactors responsive to a weakened current only, and all the circuit changes for passing from series to series-parallel and parallel are obtained by means of a controller having only three working positions. The actuating- circuits and interlocks of the contactors for controlling four motors are shown in Fig. 10. When the master controller is moved to its first position, the contactors L, 13 are closed to connect the four motors A, B, C, D in series with the resistances R<1>, R<2> and parts of the windings of the contactors 11, 12. As the current drops, the contactor 11 closes to short-circuit the resistance R<1>, then the contactor 12 short circuits both the resistances R<1>, R<2>, and the contactor 11 opens. In the second position of the master controller, the contactor 17 closes a shunt circuit across the motors A, B, which includes the resistances R', R<2> and winding of the contactor 11 connected as shown in Fig. 4. The contactor 11 closes and contactor 12 opens. This causes contactor 13 to open and contactor 14 to close, thereby connecting one side of the motor A to earth. In the third position of the master controller, contactors 15, 16 close to complete shunt circuits round the motors B, C, as shown in Fig. 7. The small current flowing through the winding of contactor 12 causes that to close, and the interlocks break the actuating-circuit of contactor 17, and complete that of contactor 18. The four motors are then connected in parallel between the trolly and earth as shown in Fig. 9.