Patent GB-621203-A (GB)
Title: Improvements relating to electrical regulating arrangements
IPC: G05F3/06
Filed: 1945-12-22
Abstract: 621,203. Automatic voltage regulation. HARMER, H. M. Dec. 22, 1945, No. 27722. [Class 38 (iv)] In a voltage regulating arrangement of the kind wherein a load voltage is derived from an A.C. supply voltage, in part from a voltage component obtained by means of a reactive circuit and which, with decrease in load or increase in the A.C. supply voltage increases in value and tends to alter its phase relative to the latter from 90 degrees displacement towards 0 or 180 degrees, and in part from a component which is a proportion of the supply voltage and introduced in a direction opposed to the 0 or 180 degrees displacement (as the case may be) of the first component, a part is also deirved from a third component developed across an inductance, the value of which can be varied by a D.C. biassing voltage applied to a winding or windings thereof. The invention is developed from the arrangement shown in Fig. 2, wherein a voltage Vr applied to a load R is derived from a system comprising an inductance L and condenser C connected in series across a supply Vs and, in parallel with one of them, e.g. the condenser C, and a load resistance R, an inductive reactance L<SP>1</SP> having a core which is worked above the knee-point of its magnetization curve, the nett reactance of the parallel reactances being made numerically equal to the other opposite reactance L at the normal frequency of supply and with its flux density not exceeding the knee point. The second component is derived from a transformer T connected across the supply voltage or a part thereof, and is in opposition to the first component. According to the invention, the third component is obtained by connecting in series with the inductance L and condenser C an inductance L<SP>2</SP>, Fig. 4, in the form of a transformer with its secondary winding additive to that of L<SP>1</SP> or T, the inductance of L<SP>2</SP> being variable by varying the permeability of its core by a biassing direct current or rectified alternat. ing current applied to a winding or windings W thereof. The effect of the third voltage Vb is to raise or lower the resultant voltage Vr across the load R, depending upon the direction in which Vb operates relative to the other voltages Va and Vc in the load circuit. At the same time, the equivalent positive internal impedance introduced will, to a greater or less extent, cancel the negative internal impedance of the load circuit. A constant voltage Vr is thus maintained across the load. In one modification, Fig. 5 (not shown), the load circuit is made independent of frequency variations in the A.C. supply by deriving the biassing voltage of L<SP>2</SP> from a bridge rectifier connected across the supply mains in series with a tuned circuit comprising a condenser and inductance. The biassing current may be derived from other parts of the main circuit, e.g. the voltage Vr, either directly or through amplifying means. The biassing ampere turns may be proportioned between separate windings supplied with differently derived currents, and the current may be varied by a manually or automatically adjustable resistance. The load voltage across R may be rectified and smoothed, and by a third connection from the network a threephase rectifier may supply the load. Specification 515;207 is referred to.