Patent GB-803581-A (GB)
Title: Improvements in and relating to electric stabilising circuit arrangements
Inventor: LAW HILTON
IPC: G05F1/12
Filed: 1954-05-28
Abstract: 803,581. Automatic regulation. ENGLISH ELECTRIC CO., Ltd. May 27, 1955 [May 28, 1954; Aug. 19, 1954], Nos. 15896/54 and 24161/54. Class 38 (4). In a current stabilizing network, the series connections across an A.C. supply 12, Fig. 1, of a linear inductor 10 and a bridge rectifier 11 supplying a load 13 gives a substantially constant load current with simultaneous proportional changes in supply voltage and frequency, the inductor impedance being sufficiently large to " swamp " that of the load. In order to improve the stabilization, a compensating current 12, derived from the secondary of a transformer 14 connected across the supply 12, is fed to rectifier 11 in opposition to the main load current I1. The series capacitor 15 and resistor 16 in the subsidiary circuit cause a gradual change in 12 with simultaneous proportional changes in supply voltage and frequency, whereby the small change in II is matched and the rectifier current II-12 maintained substantially constant. In order to compensate for supply voltage changes at a constant frequency, a further compensating current 13, derived from a potentiometer 17 across the secondary of transformer 14, is fed to the rectifier in opposition to the current II. The magnitude of the current 13 is controlled by a saturable inductor 18 in series with a linear inductor 19, whereby the current increases as the supply voltage increases in order to compensate corresponding increases in I1. A non-saturable inductor may be substituted for the capacitor 15, if the rate of change of I1 increases with voltage and frequency. In some instances it may be necessary for current 12 to aid current I1 in which case the resistorcapacitor circuit connected across the rectifier may be supplied from a further secondary winding on transformer 14 or may be connected across the inductor 10. In a modification, Fig. 2, the main series circuit comprises a linear inductor 40 in series with a bridge rectifier 41 supplying a load 44 across a transformer supply winding 42a. A smoothing network comprising elements 45-48 is connected between the rectifier output and load and presents a purely resistive impedance. A subsidiary circuit comprising series linear and saturable inductors 49, 50 is connected across the rectifier and is supplied from a transformer winding 42, whereby supply voltage variations at a constant frequency are compensated by a current 13 in opposition to the main load current I1 as in the system of Fig. 1. These independent voltage variations are further minimized by boosting the current I1 by means of a current 14 developed in a circuit comprising a saturable inductor 51 connected across the rectifier and supplied by a winding 42d, whereby the inductor saturates with increase in supply voltage to cause increase in the current 14. Simultaneous proportional changes in supply voltage and frequency are compensated by a D.C. current I21 fed to the load in opposition to the main D.C. load current I1<SP>1</SP>. This current is derived from a circuit comprising reactance combination 53, 54 supplied from a winding 42e the reactance combination having variable impedance over the range of frequency variation and resonating somewhat above the upper variation limit.