GB720268A - Improvements in or relating to electric circuit arrangements for operating electric discharge lamps - Google Patents

Abstract

720,268. Supply systems for space-discharge apparatus. GENERAL ELECTRIC CO., Ltd., CATES, J., and JENKINS, H. G. April 18, 1952 [April 20, 1951], No. 9285/51. Class 38 (4). A circuit arrangement for ensuring starting of one or more series-connected low-pressure hotcathode electric-discharge lamps when subjected to low ambient temperatures or 2 reduced supply voltage comprises an electrodeheating transformer having a primary winding P connected directly to A.C. input terminals I1, I2 and two or more electrode-heating secondary windings S1 . . . S3 connected each to one of the lamp electrodes E1 . . . E4, the windings S1 and S2 being connected also to the input terminals S through a ballast inductance B, to apply the supply voltage across the electrodes, and comprises also one or more resistance-heated thermal switches having normally closed contacts T1, T2 connected between the secondary windings and heater resistance H1, H2 serially connected with the ballast inductance: hence, on starting, the electrodes are heated by the transformer, and furthermore a current flows through the inductance and the switch heaters and contacts until one of the switch contacts opens to generate a voltage pulse from the inductance to start the corresponding lamp, such contacts being held open during lamp running by the discharge current. The other lamps, if any, start after the first, the heating of their switch heaters being continued by the discharge current of the then running lamp. Where there are more than one lamp, each secondary winding additional to those supplying the end electrodes of the lamp series, supplies the two adjacent electrodes of a lamp pair, and there may be a separate switch for each lamp, as shown, or one for all the lamps. The overall ballast may be inductive or capacitive. The secondary windings may be in voltage aiding or opposition relative to the primary winding. In the Provisional Specification the thermal switches may alternatively be glow switches, and an earthed starting stripe may be provided. Specification 602,858 is referred to.