GB748876A - Improvements in or relating to electric circuit arrangements for starting and operating from an alternating current supply two low pressure electric discharge lamps eachhaving two heatable cathodes - Google Patents

Abstract

748,876. Supply systems for space discharge apparatus. GENERAL ELECTRIC CO., Ltd., and CATES, J. Dec. 9, 1953 [Dec. 9, 1952], No. 31213/52. Class 38 (4). Two series-connected low-pressure .electric discharge lamps 1, 2 each having two heatable cathodes 3, 4 and 5, 6 are started and operated by a circuit which includes a resistance heated thermal starter switch whose normally closed contacts 17 shunt one, 2, of the lamps and whose heater resistance 18 is connected in series with both lamps, a cathode heating transformer 10 whose primary winding 11 is connected across the circuit A.C. input terminals 12, 13 and whose secondary windings 8; 9 supply heating current at least to the cathodes of the lamp 1 unshunted by the contacts 17, and a ballast impedance which consists of or includes an inductor 14 serially connected with the lamps; as shown, the arrangement provides that via the contacts 17 the full voltage is first applied to the unshunted lamp 1 which, after its cathodes have been heated by windings 8, 9, starts, and its discharge current flows through the cathodes 5, 6 of the shunted lamp 2 and the heaterresistance 18 heating same until contacts 17 open to generate a high voltage pulse across inductor 14 which causes or assists lamp 2 to start. The transformer 10 may also have a main secondary winding 11, 16 across which the lamps are connected. In modifications the transformer 10 also heats either one or both of the cathodes 5, 6 of lamp 2. The cathode heating windings may be connected in voltage-aiding relationship with the discharge voltage applied across the lamps. The ballast may include a capacitor 15 and be capacitive. The lamp 1 may have an earthed starting strip 7. Specification 720,268 is referred to.