GB1240267A - Electric power control circuit - Google Patents

Abstract

1,240,267. Automatic power control systems. ENGLISH ELECTRIC CO. Ltd. July 25, 1968 [July 26, 1967], No.34263/67. Heading G3R. The power consumed by a load is maintained constant at a desired value by a control system including a Hall device which monitors the current and voltage of an A. C. source supplying the load, the action of the system being modified by a signal proportional to the rate of change of load current or power input. As shown, the instantaneous power delivered by a three phase supply RYB to a load is monitored by two Hall multipliers H1, H2 the outputs from which are applied over respective resistors R1, R2 to an operational amplifier A which also receives a reference signal from a potentiometer PT1 associated with Zener diodes ZD1, ZD2. The operation, e.g. summation, integration etc., performed by the amplifier A is determined by its feedback impedance Z and its output, which is proportional to the actual power consumed by the load and the desired value set by PT1, is smoothed by filters R4, C1 and R5, C2 and is applied to a control element for governing the power consumption of the load. A voltage for stabilizing instantaneous input excursions is also applied to amplifier A at terminal TM1, this voltage being proportional to the rate of change of power or current. For use with a D.C. load, e.g. an electro-chemical process, the output from the amplifier may be used for transductor control of the D.C. quantity, or it may be used for varying the firing angle of devices such as mercury arc valves or thyristors in a controlled rectifier or inverter.