GB515266A - Improvements in and relating to electric battery charging systems - Google Patents

Abstract

515,266. Charging batteries. BRITISH THOMSON - HOUSTON CO., Ltd., and LUDBROOK, L. C. May 27, 1938, No. 15891 [Class 38 (iv)] In electric battery charging systems, more particularly for charging and keeping fully charged the batteries for emergency lighting systems, a rectifier is provided to supply the battery and a load in parallel, the output of the rectifier being controlled by the battery current to maintain the said charging current at a small positive value independently of any changes in the supply voltage and the load current. As shown in Fig. 1, grid-controlled rectifier tubes 2, 3 are fed from a mains transformer 1, a lagging A.C. bias being applied to their grids from a transformer 4. Control of the grids is obtained by varying the D.C. component of the grid bias in known manner. The rectifier supplies a load 6 and battery 16, there being a low resistance 7 in the battery circuit. The D.C. coil of a saturable reactor 8 is connected across the resistance 7, and resistors 10, 11 are connected across windings on the two outer limbs, so that the voltage developed across these resistors is a fraction of the current through 7. An auxiliary D.C. bias is supplied across a potentiometer 12, and the conditions are such that a change in battery current due to any external cause automatically regulates the grid bias of the rectifier and controls the output of the latter so that the charging current is maintained within certain limits. In a modification a rectifier tube supplying saturating current to a reactor in the primary circuit of transformer 1 is controlled similarly to the rectifiers 2, 3. To supply a full charge when required the sensitivity of the control is reduced by inserting an impedance 17 in series with the saturating winding of the reactor 8.