GB918783A - Improvements in or relating to phase control of three phase power supplies - Google Patents

Abstract

918,783. Automatic phase control. COLE Ltd., E. K., COX, V. J., and BEAVEN, R. P. Sept. 12, 1960 [Sept. 24, 1959], No. 32472/59. Class 40 (5). Relates to an apparatus or system for maintaining in correct symmetrical phase relation a three-phase power supply derived from circuits providing two single-phase outputs substantially in quadrature; which comprises means for feeding these outputs to an arrangement of Scott-connected transformers with which is connected a phase discriminator which derives an error signal proportional to the extent of any incorrect phase relationship at the three-phase output terminals, and means for utilizing the said error signal to vary the phasing between the two single-phase outputs to correct the said incorrect phase relationship. The two singlephase outputs may be obtained from a single oscillator O with a phase-shifting network R1, W1 in its output (see Fig. 1) or from two separate locked oscillators (Fig. 2, not shown). The two outputs are fed via power amplifiers whose outputs are voltage-regulated to the two inputs of Scott-connected transformers X. The threephase outputs are taken from the terminals A, B, C of this system, and across two pairs AB, AC, rectifier circuits BR1, BR2 are arranged to feed opposite polarity outputs to control windings W3, W4 of a saturable core reactor L1. Any difference in the two outputs alters the flux through, and hence the inductance of, winding W1, so as to alter the phase angle between the two inputs to the Scott transformers, and restore the three-phase outputs to their correct relationships.