GB739042A - Improvements in operating circuit arrangements for electric discharge lamps - Google Patents

Abstract

739,042. Supply systems for space discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd. June 29, 1951 [July 21., 1950], No. 18283/50. Class 38 (4). A dimming circuit for a plurality of gas and/ or metal vapour electric discharge lamps 8 comprises a transformer 15 whose primary winding of a constant number of turns is connected to A.C. supply terminals 1 and whose secondary winding of a variable number of turns is connected to a series circuit which includes a common stabilizing choke 7 and the low-voltage primary windings 6 of a plurality of individual lamp transformers to the higher voltage secondary windings 5 a respective lamp is connected, the lamp electrodes 9 being supplied with heating current from the secondary windings 12 of a plurality of respective electrode heating transformers having their primary windings 13 connected to a source of sensibly constant voltage ; operation of means, e.g. a tapping 14, by which the number of secondary turns is varied varies the current in the series circuit and hence the light output from the lamp. Preferably, as shown, the electrode heating transformer primary windings 13 are supplied from discharge current supply terminals 1. The transformer 15 may be autowound, as shown, or double-wound. The lamps may be of the low-pressure fluorescent type and may have earthed starting strips 11 and radio interference suppression condensers 10. In the Provisional Specification the lamps may be dimmed by a series resistor instead of the transformer 15. Specification 644,547 is referred to.