GB395779A - Improvements in and relating to mercury vapour rectifiers - Google Patents

Abstract

395,779. Rectifying alternating current. AKT.-GES. BROWN, BOVERI, ET CIE, Baden, Switzerland. Feb. 5, 1932, No. 3462. Convention date, Feb. 5, 1931. [Class 38 (ii).] In grid-regulated mercury-vapour rectifiers, the grids are normally negatively charged but are periodically subjected to a positive potential of short duration in order to render their respective anodes conducting, the positive potential being distributed to the grids by rotary contact apparatus having adjustable timing to enable the output voltage of the rectifier to be varied. Figs. 3 and 5 show alternative arrangements each comprising a polyphase rectifier 2, a supply transformer 1, load circuit 5, and a set of grids 4 connected to a source of negative potential and to a rotary distributer 8. In Fig. 3, the source of negative potential is shown as a battery 15, and in Fig. 5 negative bias is derived from a tapping on a resistance 18 in the circuit of the exciter anodes. In the first case, the source of positive potential supplied to the distributer 8 is shown as a battery 11, and in the second case, the positive potentials are derived by tapping the positive half waves from a transformer 17 associated with the distributer. In both cases the distributer is driven synchronously with the supply frequency by a motor 9, and grid current limiting resistances 6, 6a are provided. Protection against excess current and back-ignition may be provided by inserting an automatic switch 13 in the distributer circuit, the switch being adapted to open under fault conditions and interrupt the positive voltage impulses which normally render the rectifier operative. Angular displacement of the non-rotary part of the distributer for effecting voltage regulation may be effected by hand or automatically in response to output voltage, load current, or both.