GB837176A - Improvements in or relating to magnetic amplifiers - Google Patents

Abstract

837,176. Magnetic amplifiers. WESTINGHOUSE ELECTRIC CORPORATION. March 21, 1958 [March 28, 1957], No. 9106/58. Class 40 (9). Each of the parallel connected reactors 20, 50 of an auto-selfexcited amplifier is connected in series with an additional reactor 30 or 60 which have cross-connected feed-back windings 34 and 64. Series energized bias windings on all cores prevent the cores from being completely switched by the A.C. source 90 in the absence of a control signal. Significant output appears across the load when the bias is backed off by opposing control windings. The arrangement is designed to give a constant voltage across the load which may be a relay having a low impedance while being operated and a higher impedance when operated. With a high load current the feedback windings 34 and 64 keep the impedance of reactors 30 and 60 to a minimum but as the impedance of the load increases the load current falls and the impedance of reactors 30 and 60 increases. The circuit may be made bi-stable by feeding back current from the load circuit directly to the control windings to hold the amplifiers locked in an operated state and by providing additional control windings to enable the operated state to be inhibited and the bias re-instated, see Fig. 2, not shown. The control circuit may include windings on the reactors 30 and 60 (see Fig. 3, not shown). The load may be energized in a rectifier bridge circuit or from a centre-tapped transformer (see Figs. 4 and 5, not shown). In Fig. 6, the cores 20 and 50 are set during firing half-cycles when the excitation windings are energized and are reset during the intervening half-cycles from an alternating source 120 unless inhibited by a voltage across 70, 72, which backs off the rectifiers 28 and 58.