Patent GB-436929-A (GB)
Title: Improvements in and relating to electric circuit control apparatus
IPC: G05F1/32
Filed: 1933-12-18
Abstract: 436,929. Automatic regulation ; current transformers ; impedance networks. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.- (Assignees of Boyajian, A. ; 55, Stratford Avenue, Pittsfield, Massachusetts, U.S.A.) Dec. 18, 1933, No. 35584. Void [Abridged as open to inspection under Sect. 91 of the Acts, June 25, 1934]. [Classes 38 (ii) and 38 (iv)] [See also Group XL] In A.C. circuits comprising self saturable inductance and capacity connected in series or in parallel so as to have various resultant characteristics, the saturation of the inductance is produced by a D.C. biassing winding more than by the A.C. glow therein in order to reduce harmonics. The capacity and inductance curves and valves may be so chosen that the combination behaves as variable inductance, " saturable " capacity, and saturable inductance at various parts of its volt-ampere characteristic or shows this continuous or " jumping " effects. The combination may be arranged to operate over a range of its characteristic such that it behaves as a " saturable " capacity and may thereby be used to neutralize the effect of a series or parallel connected self-saturable choke. In this respect it may be connected across the secondary or a tertiary winding of a current transformer so as to neutralize the saturation and phase angle effects thereof so that such transformers may be designed for higher flux densities. If the D.C. winding of the saturable choke in the combination is energized through a rectifier from part of the A.C. flowing through its reactive winding and the series or parallel capacity is omitted, the resultant volt-ampere curve of the inductance may be arranged to have at first a rising and subsequently a falling characteristic or to show " jumping " effects. Worked on the falling part of its characteristic such a reactor may be used as effective capacity to neutralize the inductance of an inductance in series or parallel therewith. The effect may be enhanced by adding capacity in series and in parallel with such a reactor. If the reactor characteristic is arranged to have a flat saturation part it may be used for voltage regulating purposes in combination with the impedance drop in a line. Such an arrangement is shown in Fig. 12 in which the voltage across a load 44 is maintained constant by connecting a self saturating reactor 12 having a saturating winding 13, across the load and arranging that with the desired voltage Eo it operates on the knee of its volt-ampere curve. Any increase or decrease in voltage produces a large change in current through the reactor and a resultant change in the voltage drop in line impedances 45 so as to maintain the voltage Eo across the load. The effect is increased by adding series and parallel capacity in the reactor circuit so that when the voltage varies above and below Eo, the current taken by the reactor circuit changes from leading to lagging or vice versa. A constant voltage may be obtained from varying voltage supply by connecting such a circuit including the series and parallel capacity to the source through an inductance preferably having a saturating characteristic and tapping off the combination of reactor and series capacity paralleled by a further capacity. In a voltage regulating system, Fig. 10, an induction regulator 26 in the line is operated by a reversible induction motor 28, one stator winding 31 of which is energized from across the line 25 and the other from a bridge circuit formed by a centre tapped reactor or auto-transformer 33 connected in parallel with a combination of resistance 35 in series with a condenser 36 which is paralleled by a saturable reactor 37. The bridge circuit is energized from across the mains 25 and a saturating winding 38 of reactor 37 is energized through a rectifier 39 from the substantially constant voltage of the mains preferably through a circuit comprising capacity 41 and self-saturable inductance 42 in parallel. The bridge circuit and combination of capacity and inductance 36, 37 are such that at normal mains voltage the voltage across the stator winding 32 is in phase with that of the mains, but when the mains voltage rises or falls the voltage across the winding 32 leads or lags by a varying angle so as to operate the motor 28 in one or other direction to restore the mains voltage to normal.