GB682716A - Means for controlling the candle-power of luminous electric discharge tubes - Google Patents

Abstract

682,716. Supply systems for space discharge apparatus. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. June 15, 1950 [June 20, 1949; March 13, 1950], No. 14936/50. Class 38 (iv). The light output of one or more groups of one or two series-connected tubes is controlled by an adjustable impedance connected on the secondary side of each lamp group supply transformer, the latter having separate windings for heating the tube electrodes. In the preferred embodiment shown, the primary winding of a high reactance transformer 35 is auto-connected with the discharge current supplying secondary winding in a series circuit comprising the tubes 1, 2, undirectional valves 41 and the selfexcitation windings 39, 40 of a two-cored transductor 36. The tube current is controlled by variation of a rheostat 25 in the energizing circuit, comprising a rectifier 26 and a current transformer 33 in the supply line 6, of seriesconnected transductor windings 42, 43. A resistor 30 shunts the tubes to by-pass part of the no-load current to permit very low levels of illumination, and further tube groups may be connected to conductors 47, 48 for simultaneous control. In other embodiments a separate ballast reactor and double-wound normal reactance transformer may replace that shown, and a rheostat replaces the transductor; or a single transductor may control all the groups through a plurality of further transformers, one for each group.