GB742513A - Improvements in and relating to voltage stabilisation devices for a.c. circuits - Google Patents

Abstract

742,513. Automatic regulation; transformers. HOWE, H. Sept. 9, 1953, No. 24929/53. Classes 38 (2) and, 38 (4). [Also in Group XXXIX] An automatic A.C. voltage stabilizer comprises a transformer having two magnetic circuits made from materials having dissimilar magnetic characteristics but arranged to have equal fluxes when the primary voltage is normal, the fluxes becoming unequal when the primary voltage fluctuates and giving rise to an overall secondary voltage of suitable magnitude and direction to compensate for the fluctuation. In the first embodiment, Fig. 1, a load W1, W2 is supplied from a source L1, L2 in series with the secondary S of the transformer. The transformer primary is wound in two parts P1, P2 to produce opposing fluxes in each core A, B, whilst the secondary embraces both cores. If the supply voltage falls below normal the flux in core B decreases at a quicker rate than that in core A and the difference of flux produces the corrective voltage in the secondary. A rise in supply voltage produces the reverse effect. In a modification, Fig. 2 (not shown), there is a single primary and a split secondary. In a further embodiment, Fig. 3, the core B is split into two parts B1. B2, and provided with a pair of feed-back windings F1, F2, connected oppositely in series and energized from the secondary winding of a current transformer Q or a series rectifier V in the load circuit. The windings F1, F2 create a varying degree of partial saturation in the two rings which reduces the impedance of their primary winding P2. This increases the voltage across the primary P1 and by thus increasing the disparity in flux between the cores and provides an additional boost voltage. In a further embodiment, Fig. 4, the load W1, W2 is supplied in series with the secondary S5 of a booster transformer U of the kind described in Specifications 742,487 and 742,494. The booster has two pairs of control windings El, E2, H1, H2, energized from the secondary S7, S8 of the transformer J which is modified by the addition of a tertiary winding S6 on core A connected to the centre tap of the winding S7, S8 and to a point common to the booster control windings. When the supply voltage is normal there is no voltage induced in the secondary S7, S8 and the voltage of the tertiary winding S6 is applied equally to both pairs of booster control windings and the booster voltage is zero. When the supply voltage is below normal the flux in core B falls more than that in core A. Renco a voltage appears across each of the secondary sections S7, S8. The booster control windings El, E2 receive the subtractive voltage from windings S6 and S7, whilst the windings H1, H2 receive the additive voltages from windings S6 and S8 and so produce a corrective boost voltage across the booster secondary winding S5. A rise in supply voltage reverses these effects. In a modification, Fig. 5 (not shown), the transformer J has a single primary and two separate secondaries, plus the tertiary winding. In a further modification, Fig. 6 (not shown), the booster unit has a single primary and two separate secondaries. It is also stated that the current compounding arrangement of Fig. 3 can be added to the booster circuit of Fig. 4.