GB774229A - Improvements in or relating to electromagnetically operated switch devices - Google Patents

Abstract

774,229. Converting. SIEMENS-SCHUCKERTWERKE AKT.-GES. Jan. 31, 1955 [Jan. 30, 1954], No. 2898/55. Class 38 (2). [Also in Group XXXVII] An electromagnetically operated switch in series with a switching choke 25 in a converting system comprises a first holding magnet 1 with an armature and associated contact bridge 15, the magnet 1 carrying two windings. The first winding 9 through which flows part at least of the main current is so arranged that as the current decreases the effect of the magnet in holding the armature against a spring is reduced. The second winding 5 is energized from a winding 27 on the switching choke by the voltage developed during the opening current step to weaken the holding effect still further until the armature is released and moved by the spring to open the switch. The switch can thus be arranged to open in the current step, both when this is long and the voltage developed in choke winding 27 is small and when it is short and the voltage developed is larger. The armature 15 is held in the open position by a second holding magnet 16 incorporating a permanent magnet 21 until the supply voltage rises in the forward direction when current flowing through winding 18 diverts the holding flux from permanent magnet 21 through shunt 20. The armature 15 then moving under spring force approaches the first holding magnet 1, a movement which is assisted by the effect of winding 10 on shunt 7 in series with winding 18. This diverts some of the flux of permanent magnet 12 away from shunt 7 to polepieces 3. When main contacts 28 are bridged the rising load current passes through winding 9 also on shunt 7 which it saturates to divert the flux of magnet 12 wholly to the polepieces to retain the armature in the closed position during forward current flow. In one modification shunt 7 is undivided, the windings surrounding it completely, Fig. 2 (not shown). In another modification shunt 7 is replaced by a movable shunt to allow adjustment of the opening current and the windings are no longer on the shunt but on the limbs between the poles and the permanent magnet. Also the winding 5 may be connected to winding 27 through the main contacts 28. The permanent magnets may be replaced by electromagnets. Two switches 15, 151 according to the invention may be connected in parallel, one designed for carrying the main current and the other for opening and closing small currents, Fig. 4. Windings 191, 101 of switch 15<SP>1</SP> are connected in series with the main contacts of switch 15 which opens after and closes before switch 15<SP>1</SP> which carries the main current. Windings 5, 5<SP>1</SP> are connected in series to a winding 27 on the single switch choke 25. The holding flux may, if desired, be derived entirely from the main current.