GB661705A - Improvements in electric circuit arrangements for operating electric discharge lamps - Google Patents

Abstract

661,705. Control systems for space discharge lamps. GENERAL ELECTRIC CO., Ltd., and WILLIAMS, C. E. March 31, 1950 [April 22, 1949], No. 10764/49. Class 38(iv). Dimming of a discharge lamp 7 supplied through a stabilizing condenser 9, is effected by a variable inductance 15 shunted across and/or a variable inductance in series with the condenser of limiting values such that the ballast is always predominantly capacitative. Variation of the inductance may be effected by tapping the winding or adjusting the core position but preferably by energization of a control winding 16 with direct current. To obtain simultaneous adjustment of a lamp 24 supplied through an inductive ballast 26 the latter may comprise a saturable choke, the control windings 31 and 16 being supplied through the tapping 34 on a potentiometer resistance 35 so as to obtain automatic decrease in saturation of one choke with increased saturation of the other. Alternatively, this latter requirement may be effected by providing a constantly energized biassing winding on one choke whilst the two control windings are supplied in series with the variable control current, Fig. 3 (not shown). The sensitivity of the control may be increased by providing a feed-back winding on the choke, energized in accordance with the lamp current.