GB731651A - Improvements relating to circuit arrangements for stopping a motor selector in telecommunication installations, more especially telephone installations - Google Patents

Abstract

731,651. Automatic exchange systems. ALBISWERKE ZURICH AKT.-GES. Oct. 9, 1953 [Nov. 22, 1952], No. 27888/53. Class 40 (4). In a selector which is driven by a motor of the kind comprising two stator coils M1, M2 alternately energized over contacts ml, m2 controlled by a cam on a rotor shaft, further cam-operated contacts b1 b2 are arranged to connect a selector wiper d to that stator coil which is de-energized at any particular time, so that when the selector engages a potentialmarked outlet it is stopped by simultaneous energization of both coils. The groups of contacts b1 m1; b2, m2; m1, m2 are arranged to make before break with the result that short but ineffective periods occur during running in which both stator coils are simultaneously energized. The basic arrangement is shown in Fig. 1 in which to start the switch a circuit for battery Ba is closed at contact w and the outlet required is marked over contact r. Braking windings B1, B2 may be provided in the motor, Fig. 3, to avoid the high current flow over the selector which arises when the marked outlet is found. With this arrangement B1, M1 or B2, M2 are energized in series at the marked contact and the current is reduced without any decrease in the total motor flux. The overlapping closure times of the contacts permit preparatory build-up of magnetic fields which results in a more rapid stopping action when both coils are energized simultaneously. To reduce the motor speed, a resistor R1 may be switched into circuit, in which ease a retarding current will alternate between M2, B2, R1 and M1, B1, R1 when M1 and M2 are energized respectively. In a modification, Fig. 4, a variable speed-regulating resistor Rq completes a closed circuit comprising windings B1, B2 which functions as a damping circuit for flux variations produced by the stator coils.