Efficient light source based on an inductive ferrite-free discharge at frequencies of 300–3000 kHz

Abstract

Glass cylindrical tubes from 30 to 50 cm long and from 5 to 7 cm in diameter are used to initiate an inductive discharge in electrodeless luminescent lamps at frequencies of 300–3000 kHz with a power of 50–300 W. The tubes are filled with mercury vapor and an inert gas (argon at a pressure of 0.1 mm Hg), and their inner surface is covered by a phosphor and protective coating. An induction coil (from 5 to 14 turns) made of a low-resistivity multiple-conductor cable embraces the discharge tube in the longitudinal direction, forming a discharge-initiating loop. Because of a high Q factor of the coil, Q c = 400, the power losses in it are 4–5 W at frequencies higher than 400 kHz; the energy efficiency of the lamp is η = 0.95–0.96. Luminous efficiency ɛ of the lamp grows with discharge excitation frequency, reaching ɛ = 83–84 lm/W at a frequency of 530 kHz and a power of 150 W.