GB558145A - Means for the fine regulation of an alternating current voltage - Google Patents

Abstract

558,145. Regulating transformer and other A.C. voltages. ALLMANNA SVENSKA ELEKTRISKA AKTTEBOLAGET. March 4, 1942. No. 2834. Convention date, March 17, 1941. [Classes 38 (ii) and 38 (iv)] An A.C. voltage is progressively regulated between two values by simultaneous regulation in dependence on each other of two saturable inductances connected in series, and at the same time the load current taken from their interconnection is determined. Fig. 2 shows a motor circuit supplied at variable voltage from a tap regulated transformer between the tap bus bars 14, 15, of which are connected the inductances 18, 19. The voltage drop in these inductances is maintained at a fixed phase difference, such as 90 degrees with a view to obtaining minimum dimensions for the inductances, by e.g. a quadrature relationship between the rectified currents in the paralleled saturating windings obtained by inductance 21 and resistance 20. The requisite progressive change may be obtained by means of a winding or windings saturating the inductance 21. The load current is determined by the total current supplied to the saturating windings of inductances 18, 19 which, as shown, is determined by a current transformer 17 in the load circuit. Fig. 3 shows an arrangement in which an automatic progressive change of voltage follows a tap change. Windings 29, 30 acting respectively in aid of and in opposition to a self saturating winding 28 are supplied respectively from half the tap bus bar voltage and by the difference between this voltage and that across one inductance. A modification using the full tap voltage on winding 29 is also referred to. The load current is determined by the saturating current applied to an inductance 25. The invention is not restricted to the quadrature relation referred to but by suitable selection of the impedances in the saturating circuits the phase relation of the inductance voltages may lie anywhere between 60 degrees and 135 degrees the appropriate phase relation between their saturating currents before rectification being respectively 120 degrees and 45 degrees. Resistances adiusted indirectly may be used instead of impedance elements to regulate the saturating currents of the inductances 18, 19 and their phase relation may be controlled by a phase angle meter responsive to the phase relation of the currents in the inductances. Specification 434,456 is referred to.