Improvements in or relating to electric circuit arrangements for starting and operating from an alternating current supply a pair of low pressure electric discharge lamps

摘要

744,820. Supply systems for space discharge apparatus. GENERAL ELECTRIC CO., Ltd;, and CATES, J. Jan. 6, 1954 [Oct. 24, 1952], No. 26766/52. Class 38 (4). An electric circuit arrangement for starting and operating from an A.C. supply a pair of low pressure electric discharge lamps 1, 2 connected in series with each other and with a capacitive ballast impedance, includes two series connected capacitors 8, 9 in the ballast impedance and an auxiliary starting inductor 16 ehunted across one of the lamps and part of the ballast impedance, being connected at one end to a point between the said capacitors, the magnitude of the inductor being such as to pro-. duce starting first of the unshunted lamp and then of the shunted lamp. The lamp may be of the mercury vapour fluorescent type, and may as shown have earthed starting stripes 18, 19 and heatable cathodes 3 ... 6 heated by secondary windings 12, 15, 17 of a filament heating transformer 13, or they may be of the coldcathode type. The ballast impedance . may include an inductor 7 and the capacitors may be of equal capacity and constructed as in Specification 712,819, [Group XXXVI], so that failure of one automatically produces failure of the other. By providing two capacitors 8, 9 and arranging the connections as shown the action of either lamp as a rectifier when one of its electrodes fails is prevented. The circuit may form part of a larger circuit operating further lamps, e.g. a second pair of series-connected lamps inductively ballasted, to reduce flicker and effect power factor correction. Specifications 565,843; 712,819, [Group XXXVI]; and 744,819 are referred to.