GB661053A - Improvements in and relating to saturable reactor magnetic amplifiers - Google Patents

Abstract

661,053. Magnetic amplifiers. BRITISH THOMSON-HOUSTON CO., Ltd. March 28, 1949 [April 2, 1948], No. 8371/49. Class 40 (iv). [Also in Group XXXV] A voltage doubler magnetic amplifier, Fig. 1, comprises (1) a saturable three-limbed core split longitudinally along the centre limb 2 which carries a short-circuited winding 10 and one or more control or signal windings 8, 9; (2) two reactor windings 6, 7 wound respectively on the outer core limbs; (3) two parallel connected circuits (see equivalent circuit, Fig. 2) fed with A.C. at 1 and each comprising reactor windings 6, 7, rectifiers 11, 12 and capacitors 13, 14, respectively, with the capacitors 13, 14 connected together across the load 15. With two control or signal windings 8, 9 as shown, a bias signal may be applied to one winding and a varying signal to the other or two signals may be applied to the two windings respectively to obtain an output proportional to the sum or difference between the two. The L and C of the two parallel circuits may be so chosen that each circuit is series resonant at a frequency below the frequency of the applied A.C.; for example, if the latter is 60 c/s. the reactor windings and capacitors may be tuned to 7 to 10 c/s. In operation the two parallel connected circuits are respectively conducting during opposite half-cycles of the applied A.C. and reactor windings 6, 7 correspondingly produce additive unidirectional fluxes and subtractive or phase opposition alternating fluxes in centre limb 2. Short-circuited winding 10 tends to prevent any net alternating flux (due to flux in one section of limb 2 not being exactly balanced by 180 degrees apart flux in the other section of limb 2) from introducing induced voltages or circulating currents in the signal windings. The unidirectional fluxes tend to partially saturate the magnetic core and the amplifier is regenerative because any increase in saturation of the core produced by a direct current in signal winding 8 or 9 reduces the effective inductance of the reactor windings 6, 7 and causes larger direct currents to flow therethrough; this in turn further increases the saturation of the core. The split core construction producing air-gap at 5 preferably of the order <SP>1</SP>/ 32 to <SP>1</SP>/ 16 inch is stated to reduce hysteresis effects and thus prevent masking of feeble applied signals, for example, with D.C. applied signals as small as 1.0 micro-rnicrowatt, there is an amplifier power gain of over one million.