GB657072A - Improvements in or relating to electric circuit arrangements for operating electric discharge lamps on a.c. - Google Patents

Abstract

657,072. Control systems for space discharge lamps. GENERAL ELECTRIC CO., Ltd., and WILLIAMS, C. E. Oct. 26, 1948, No. 27823. [Class 38 (iv)] In a circuit arrangement for varying the discharge current through a hot cathode discharge lamp 7 by means of a variable ballast impedance, and comprising a heating transformer 5 for the lamp electrodes adequate control of the electrode heating is ensured by forming the ballast impedance in two parts comprising respectively a first part 3 connected between the transformer primary 13 and a supply terminal 1, and a second part 8 connected between the transformer and a lamp electrode, one or both parts of the ballast impedance being adjustable. The ballast impedance may comprise two resistances or two inductances or one of each, and variation of the inductance may be effected either by D.C. saturation or by an adjustable choke core. Simultaneous variation of the two parts may be effected by gauging or, in the case of inductances, by providing two choke windings on a common core. The first part of the ballast may be provided by the transformer leakage reactance and when step-up in voltage is required the secondary winding 16 may be included on the heating transformer and connected between the second part of the ballast and the lamp. The arrangement may be applied to series or parallel connected discharge lamps and in the latter connection each lamp should have its own second part but may share the first part of the ballast impedance. Specification 657,073 is referred to.