GB558027A - Improvements in and relating to electric frequency dividing systems - Google Patents

Abstract

558,027. Converting. TELEPHONE MANUFACTURING CO., Ltd., and DRAKE, B. Aug. 27, 1942, No. 12103. [Class 38 (ii)] A sub-harmonic frequency reducer adapted for example to reduce the frequency of a singlephase input to one third, has a corresponding number of branches, i.e. in this case three branches (a), (b), (c) containing non linear reactances L1, L2, L3 adapted to be set into oscillation with suitable relative phase displacement at the sub-harmonic frequency. The branches may contain transformers T1, T2, T3 and the secondary windings 4, 5, 6 of these constitute a three-phase system in mesh connection, which is adapted to produce a single phase sub-harmonic output current by coupling to it windings 1, 2 and 3 arranged so that winding 1 is in phase opposition to the connected windings 2 and 3 and has half the number of turns of either. In the arrangement of Fig. 6, the converter is started by means of an external three-phase low frequency source 7, 8, 9 which is eventually disconnected by a relay S/3. In a modification, Fig. 7 (not shown) starting is effected by means of a motor operating contacts to give properly timed starting impulses. In another modification, Fig. 5 (not shown), starting is effected by similar means to those described in Specification 548,441 and relays are provided to enable fresh attempts to be made if the first attempt does not produce the oscillation at the correct phase displacement. The three iron-cored inductances L1, L2, L3 or the transformers T1, T2, T3 may form one magnetic unit, Figs. 8, 9 (not shown).