GB611298A - Improvements in or relating to starting switches and circuit arrangements for electric discharge devices - Google Patents

Abstract

611,298. Supply systems for space discharge apparatus. THORN ELECTRICAL INDUSTRIES, Ltd., and STRANGE, J. W. April 26, 1946, No. 12719. [Class 38 (iv)] In a circuit for an electric discharge lamp 14, comprising a ballast impedance 11 in series with one or more filamentary electrodes 15 and a starting switch 12, 13, a resistor 16 is connected across the impedance at starting by means of a subsidiary switch, preferably of the thermally-operated type, whereby to decrease the preheating period of the lamp. In the arrangements of Figs. 2 and 3 (not shown), the resistor 16, which is a tungsten filament the bimetallic element 17 and heater 18 of the subsidiary switch, Fig. 1, are contained in an evacuated or gas-filled envelope, whereby the resistor assists in heating the said element. In a modification, Fig. 4 (not shown), the envelope also contains the bimetallic element 13 and heater 12 of the starting switch. In an alternative, the two thermal switches may be replaced by a combined switch having a common bimetallic element and heater and separate contacts for each circuit. The heater coils 12 and 18 may be connected in the part 22 of the circuit. The subsidiary switch may be electromagnetically operated. According to the Provisional Specification, the shunt across the ballast may be an impedance.