GB803240A - Improvements relating to current limited rectifying systems employing magnetic amplifiers - Google Patents

Abstract

803,240. Automatic voltage and current control systems. STANDARD TELEPHONES & CABLES, Ltd. Oct. 7, 1955 [Oct. 11, 1954; March 24, 1955], No. 28622/55. Class 38 (4). An automatically-regulated D.C. supply of the kind in which a saturable reactor is in series with a rectifier and in which constant voltage control is superseded by constant current control once a limiting current is reached, consists of the combination of all the following features. A portion of the output voltage of the main rectifier W1 is tapped off a potentiometer R2 and applied to a control winding 3 on a selfsaturating magnetic amplifier L2 in opposition to a reference voltage derived from a source CVS. The reference voltage is arranged to be normally greater than the voltage from potentiometer R2 so that rectifier W2 conducts. The output of the magnetic amplifier L2 is applied to the control winding of the main saturable reactor L1 by way of a bridge rectifier W5 which minimizes A.C. components being fed back from the control winding of reactor L1 to the amplifier L2 as in Specification 803,239. The voltage appearing across one arm of the bridge rectifier W5 is fed back to a stabilizing winding 9 on the amplifier L2 as in Specification 803,239. The reactor L1 is thus normally controlled via the amplifier L2 to maintain the output voltage of the rectifier W1 constant. The input current to the rectifier W1 is measured by a current transformer T2, the output of which is rectified at W6 and applied in series with a rectifier W7 and the voltage across potential divider R2 to a control winding 10 on the amplifier L2. Then when the output voltage of rectifier W6 exceeds that across R2, rectifier W7 conducts and energizes winding 10 to tend to maintain the input current to the main rectifier W1 constant at the value reached. The voltage control winding 3 on amplifier L2 is shunted by a rectifier W8 so as to limit the signal that can be passed through the winding 3 when the system is operating in the current limiting mode. In a modification, Fig. 2 (not shown), the current limiting signal is superimposed on the main. A.C. windings of the magnetic amplifier, and several slight modifications are made to the remainder of the circuit. Specifications 665,335, 745,796 and 803,241, [Group XXXIX], also are referred to.