GB756431A - Improvements in and relating to circuits for starting and operating electric discharge tubes - Google Patents

Abstract

756,431. Supply systems for space-discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 8, 1952 [Dec. 8, 1951], No. 31066/52. Class 38 (4). A starting and operating circuit for a pair of gaseous electric discharge tubes, e.g. fluorescent lamps D1, D2, comprises a transformer 11 having a primary winding P with connections to an A.C. source, a high leakage reactance secondary winding S and a low current capacity auxiliary winding A, a ballast capacitor C1, a leading current lamp operating circuit comprising in series at least the secondary winding S, the ballast capacitor C1 and connections for including both lamps, a coupling capacitor C2, and a leading current lamp starting loop circuit comprising connections for including only one D1 of the lamps both of the capacitors C1, C2 and all the windings in series, all the windings being in voltage aiding relationship within the loop circuit. The coupling capacitor C2 is to prevent the circulation of direct current by either lamp acting as a rectifier on failure of one electrode thereof, and thereby permits the low current capacity of the auxiliary winding A. In Figs. la and 3a, not shown, the operating circuit includes the primary winding P which is arranged in such circuit in voltage aiding relationship with the secondary winding S. To reduce shock hazard, as shown, one, or in Fig. 3a, both, connections from the primary winding P to the source terminals 15, 16 are made through contact pairs 17, 18 and 20, 21, each short circuited by one of the respective contact pins 2<SP>1</SP> and 2 of each lamp, whereby removal of either lamp open-circuits or disconnects respectively the primary winding from the source. In Fig. 1a a magnetic shunt provides a loose coupling between the primary and auxiliary windings.