GB1329018A - Voltage regulators - Google Patents

Abstract

1329018 Automatic voltage regulation and control C L WANLASS 8 Sept 1970 [15 Sept 1969] 42928/70 Headings G3X; G3R A voltage regulator providing an AC voltage of constant RMS value from an AC supply 10, 11 comprises a saturable inductor 12 and a capacitor 13 series-connected across the supply through a switch 16, the inductor having an inductance sufficiently large to prevent the supply alone from causing saturation, which condition is produced initially by movement of the switch arm 16<SP>1</SP> to engage contact 18 and thereby by-pass a number of turns on the inductor, after which the regulator commences operation and the arm 16<SP>1</SP> is returned to the contact 17. Alternatively saturation may be produced by other means such as a momentarily-energized winding on the inductor core 15, short circuiting of a number of inductor turns or charging the capacitor 13 by direct energy transfer thereto. Operation of the regulator consists in core saturation at a predetermined point in each half cycle of the supply 10, 11 to allow discharge of the capacitor 13, the subsequent re-charge by the action of the inductor and the supply reducing the current until the core 15 goes out of saturation. At the next change of supply polarity the above cycle is repeated, Fig. 2 (not shown). With given design parameters such as operating frequency, core material and B-H characteristic of the inductor core, the instant of core saturation in each half cycle is constant to produce a constant output voltage. If the supply volts change, the first instant after the change will alter but subsequent instants will be correspondingly changed, so that the output voltage will remain constant. The output may be taken at 20, 21 from taps on the inductor winding 14 or from a secondary winding on the core 15 whose output may be rectified, Fig. 4 (not shown) or supplied to a tapped auto-transformer Fig. 5 (not shown). Figure 6 shows a closed loop control system wherein the output voltage at terminals 54, 55 is sensed to derive an error signal, which is applied to a winding 50 on an auxiliary core 49 arranged to vary the flux-carrying capacity of the inductor core 48 and hence the instant of saturation in each half cycle. Another closed loop control system is shown in Figure 8, which uses a modified inductor comprising two cores 60, 61 and two ganged starting switches 86, 87. Series connected secondary windings 91, 92 supply a rectifier 93 whose output voltage is sensed to derive an error control signal for respective control windings 88, 89 on the cores 60, 61. Another two-core arrangement in which the output is taken from tappings on the windings 84, 85 is described, Fig. 7 (not shown). Alternatively the error signal may control the frequency of the AC supply 80, 81, which may be derived from a DC to AC converter using power transistors or silicon controlled rectifiers controlled by the error signal. If the regulator becomes overloaded the inductor stops saturating and resumes its initial high impedance state to cease the regulator operation.