GB916957A - Electric remote control system - Google Patents

Abstract

916,957. Control of A.C. motors. SOC. TECHNIQUE POUR L'INDUSTRIE NOUVELLE S.A. July 18, 1961 [Aug. 31, 1960], No. 25944/61. Class 38 (3). [Also in Group XXX] In a system for controlling railway switch points M a relay 2 operates an alarm if the points are forced out of position (trailed), and it also takes part in starting the motor so that it is tested each time the points are operated. The motor has three-phase windings X, Y, Z connected in star by lines L1 . . . L3 for running but it is started on two phases only, windings Y and Z being connected in series, and a fourth line L4 being switched in by the relay 2. Change-over is effected by limit switches 11, 12 and 21, 22 which disconnect L4. At the completion of each run, in either direction, a D.C. supervisory current is established through the four lines and the motor windings, a high resistance device U, and one of two windings on relay 2. This current is insufficient to operate the relay unless the points are trailed, when U is short-circuited. In this event, the relay closes and, besides operating an alarm, prevents the motor being switched on until the trailing is corrected and the relay reset. An arrangement is described whereby resetting requires the use of a special key, which may also operate a counter. For normal starting, the relay closes upon operation of a starting relay 1 and is held on by current through its second winding. This second winding remains energized from a resistance/capacitance circuit D, C for a short time after the motor is energized, i.e. during the starting period, or in an alternative arrangement the second winding circuit includes a transformer, the primary of which is in series with the line L4; it is thus de-energized when the motor has started and L4 has been cut out by 11 or 21.