Patent GB-1367135-A (GB)
Title: Voltage or power factor regulator circuit
IPC: G05F1/44
Filed: 1971-08-11
Abstract: 1367135 Converting ACME ELECTRIC CORP 11 Aug 1971 [15 Sept 1970] 37670/71 Heading H2F [Also in Division G3] An automatic voltage or current regulator comprises an energy storage means 18 (Fig. 13) charged from a bi-directional switching circuit 30, 31, 34A, 35A via an inductive reactance 39 from an A.C. supply, the switching circuit being arranged so that 18 is charged with a single polarity by current passed over 180 degrees of each half cycle of the A.C. input, the phase of the switching circuit being controlled at 38 in dependence on output voltage or load power factor. As described, capacitor 18 is charged from the secondary 81 of transformer 79 via diodes 30, 31 so that the left hand plate is positive. The charge on capacitor 18 is automatically adjusted by a control circuit 38 which turns on thyristors 34A, 35A at appropriate times. A regulated voltage is available across a load 36. In Fig. 1 (not shown) reactor 39 is avoided by use of a leakage reactance transformer and the load 36 is connected directly across capacitor 18. In Fig. 2 (not shown), the switching circuit is replaced by a double pole double throw switch and the transformer 79 is omitted. In Fig. 15, the thyristors are replaced by transistors 34, 35 the conduction angle of which is controlled by means of a saturable transformer 38A. In Fig. 14 (not shown) reactor 39 is replaced by two reactors connected in series with opposite ends of winding 81 and having a common core. In Fig. 8 (not shown) the A.C. is derived from a square wave inverter and an A.C. output is obtained from an auxiliary winding on the transformer. Figure 18 shows a complete circuit for regulating the voltage across capacitors 18. The capacitors 18 are charged with the upper electrode positive by diodes 30, 31 which rectify the output of winding 134 of leakage reactance transformer 65. The voltage is regulated by controlling the conduction period of thyristors 136, 137. Capacitor 159 in the control circuit is charged via resistor 158 from a potential divider 157 across the output 131, 132, until unijunction transistor 156 breaks down, pulsing a transistor 162 which changes the state of a bi-stable circuit comprising transistors 163, 164. An output from the higher voltage side of transistors 163 or 164 is passed by one of a pair of silicon unilateral switches (e.g. 169) to trigger thyristor 137 which modifies the voltage across output terminals 131, 132. Half a cycle later, the bi-stable 163, 164 is reset so that silicon unilateral switch 170 breaks down, triggering thyristor 136 which turns off thyristor 137 by means of a commutating circuit 140 ... 143. The phase angle of the triggering pulses fed to thyristors 136, 137 thus adjusts the output voltage to a value depending on setting of variable resistor 157. Transistor 173 is turned off at the beginning of each half cycle so that capacitor 174 can charge to a value which reaches the firing voltage of unijunction transistor 156 after 90 degrees. This provides an automatic current limit. Starting arrangements.-The output from secondary winding 133 is rectified by diodes 146, 147 to provide a voltage for the initial charging of capacitors 174 and 159. Automatic power factor correction.-In Fig. 11 the phasing of switches controlling the charging of capacitor 18 from a A.C. source 17 is controlled at 105 in dependence of the angle between current and voltage of a reactive load 110 so as to provide automatic power factor correction.