GB388772A - Improvements relating to electric current transforming and rectifying devices and the utilization thereof - Google Patents

Abstract

388,772. Rectifying alternating current ; charging batteries. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and DOUBLE, H. S., 173, Greenvale Road, Eltham, both in London. Aug. 28, 1931, Nos. 24256/31 and 4850/32. [Classes 38 (ii) and 38 (iv).] In apparatus for supplying direct current to a secondary battery B, or to a load L in parallel with the battery, comprising a transformer TR and a rectifying device, the primary winding of the transformer being connected to the alternating current circuit through a choke or chokes, the impedance of which is varied by a magnetizing winding or windings carrying the direct current output or a part thereof, regulating means are associated with the choke or chokes and with the magnetizing windings for the purpose of varying the output characteristics of the arrangement for imposing higher and lower voltage limits at which heavy current is supplied. The arrangement is such that a heavy charging current is supplied when the battery voltage falls below the lower limit, and continues to flow until the battery voltage reaches the higher limit, after which the charging current either falls to zero or continues at a low value, so that a trickle charge still flows to the battery. In the arrangement shown, two separate chokes CH1, CH2 are provided, and the magnetizing windings MC1, MC2 are oppositely connected, so that any alternating currents induced in them cancel out. The same effect may be obtained by providing a single choke with an extra limb, not traversed by alternating flux, on which the magnetizing winding is placed. The magnetizing windings are shunted by a variable resistance R2, and the chokes by a condenser C1 and variable resistance R1. In a modified arrangement, a dip in the output characteristic is obtained by providing a further winding on each choke, these windings, shown in broken lines, being connected, in series with a regulating resistance R3, across the leads on the direct-current side of the rectifier and acting in opposition to the main magnetizing windings. The rectifying device may comprise a bridge arrangement of copper oxide rectifiers a .. d. The windings of the chokes and the magnetizing windings may be tapped to secure further regulation. The effects obtained by the various methods of regulation are described with the aid of output characteristic curves.