GB528248A - Improvements relating to the starting of gaseous electric discharge devices such as lamps - Google Patents

Abstract

528,248. Electric supply ; transformers ; discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. March 21, 1939, No. 8979. Convention date, March 22, 1938. [Classes 38 (ii) and 38 (iv)] [Also in Group XL] A discharge lamp with two anodes 3, 4 have these connected to the ends of a transformer secondary 13, whose mid point is connected to the cathode 2 either directly or through windings 14 supplying heater current to the cathode ; across one half of the secondary is connected a condenser 28 in series with a resistance 35 and switch 29. When the main switch 16 is first closed, the cathode heater circuit becomes operative, but the resistance 35 prevents discharge across the lamp until the bimetallic strip 34 short-circuits the resistance ; the condenser 28 and secondary then form a resonant circuit capable of applying sufficient voltage between the cathode and anode 4 to break down the discharge gap and start the lamp. The circuit through condenser 28 is opened during normal running by the switch 29 its attached armature 31 being attracted at the air gap in the leg 18 of the transformer. This comprises two E-shaped cores 9, 10 separated by a gap, the central legs providing a return path for the unidirectional component of the flux. Magnetic shunts 11 are arranged in the core part carrying the primary winding 12. To improve the power factor a condenser 24 and series reactance 25 are connected across the secondary 13, the reactance 25 being wound on a E-core 26 separated by non- magnetic material from the core 10. The lamp may have a fluorescent coating.