Patent GB-784864-A (GB)
Title: Improvements in or relating to a device for supplying an electric out-put quantity in dependence upon an electric in-put quantity
IPC: G05B11/01
Filed: 1954-07-27
Abstract: 784,864. Inductors; automatic voltage control systems. SIEMENS - SCHUCKERTWERKE AKT.-GES. July 27, 1954 [July 27, 1953; July 1, 1954], No. 21987/54. Classes 38 (2) and 38 (4). [Also in Group XXXIX] An output dependent on the variation of a D.C. voltage from a predetermined value is provided by a pair of saturable reactors A, B, Figs. 2 and 3, one of which includes a permanent magnet 4 acting as a magnetic standard of reference. By providing two reactors, variations in the A.C. supply energizing the main windings does not affect the output. As shown, each reactor has an inner core 1 with series-connected main windings 2, 3 which produce a circulating flux in the core limbs, the core being preferably formed from material having a substantially rectangular hysteresis loop. Associated with each core is a control winding 6, Fig. 2, energized from the variable D.C. voltage 21 and arranged in an outer core structure comprising low coercivity limbs 5, 7, 8 formed, for example, from carbonyl iron and provided with air gaps 9, 10. Reactor A in addition has a permanent magnet 4 which reacts with the control winding flux in the outer core structure in such a way that a difference flux passes through the core 1. The main windings of each reactor are energized from separate secondary windings of a transformer 23. When the D.C. voltage is at its correct value, the main winding inductances of the two reactors are equal and no D.C. output is detected across differentially-connected load resistors 25, 27 which are separately energized over rectifier bridges 24, 26. As the permanent magnet flux exceeds that of the control winding, a change in D.C. voltage causes the impedances of the two main windings to alter in opposite respects so that a differential output voltage is produced across the load resistors. The construction may be modified as shown in Fig. 3 in which a single control winding 31 is common to both reactors. A single feed-back winding 33 is also provided. Alternative arrangements of connecting the load resistors with half-wave rectifiers and separate or centre-tapped transformer secondary windings are described with reference to Figs. 4 and 5 (not shown). In Fig. 6 is shown an arrangement for regulating a rectified voltage obtained from a three-phase alternating supply by controlling saturable chokes 112 having control and feed-back windings 132 and 133 respectively. The rectified voltage at terminals 116, 117 is supplied to a pair of saturable reactors arranged as previously described and represented schematically at 106, their outputs acting differentially in loads constituted by the control windings 107, 108 of a further magnetic amplifier 121. The response time of this amplifier is reduced by a transient feed-back winding 135 which is energized over a condenser 136 by changes in the rectified voltage. The output of the further amplifier acts in the control windings 132 of the saturable chokes, which windings, together with the feed-back windings 133, are duplicated in the drawing.