GB771479A - Improvements in or relating to magnetic amplifiers - Google Patents

Abstract

771,479. Magnetic amplifiers. GENERAL ELECTRIC CO., Ltd., and PARTON, K. C. Nov. 25, 1954 [Nov. 30, 1953], No. 33190/53. Class 40 (4). In a polyphase half-wave magnetic amplifier comprising a first polyphase rectifier bridge providing A.C. terminals and D.C. terminals, at least one reactor element having a core of highly remanent material is included in each pair of arms of the bridge between the A.C. terminals and a voltage is applied to the main winding, or to a control winding, of each reactor element during the half-cycles when the associated rectifier element in the bridge is substantially non-conductive in order to reset the flux in the reactor element to a predetermined value, this voltage being applied by means of a second polyphase rectifier bridge coupled to the first bridge by the reactor elements. Preferably the applied resetting voltage consists of alternate half-cycles of a constant alternating voltage in series opposition to an adjustable unidirectional voltage and is greater than that required to give full resetting. As shown, six rectifier elements 10 to 15 are arranged in a bridge circuit with six reactor elements 20 to 25 in series with them, a three-phase A.C. supply being connected to 31, 32, 33 and a load circuit 35 to leads 34 and 36. The reactor elements 20, 22 and 24 are connected via further rectifiers 40, 42, and 44 respectively to one terminal 37 of a unidirectional voltage source, and the reactor elements 21, 23 and 25 are connected via rectifiers 41, 43, and 45 respectively to its other terminal 38. In operation load current is drawn for one half of each cycle from the A.C. supply for each phase, and each reactor element becomes saturated once per cycle. Resetting is effected for each phase during alternate half-cycles in which load current is blocked by rectifiers 10-15, and in which current flows from 31, 32 or 33 to 33, 31 or 32 via reactor 21, 23 or 25, rectifier 41, 43, or 45, the voltage source connected to 37 and 38, rectifier 44, 40, or 42, and reactor 24, 20, or 22, respectively. The amount of resetting is directly dependent upon the difference between the voltages of the A.C. supply and the adjustable unidirectional voltage source. Modifications are described in which the resetting voltage is applied to a control winding of each reactor element, and in which the resetting voltage is applied to a tapping on the main winding of each reactor element.