Jakob Maya

Characteristics of electrodeless ferrite-free fluorescent lamp operated at frequencies of 1-15 MHz

A RF electrodeless ferrite-free fluorescent lamp with a re-entry cavity was studied at driving frequencies, f = 1.2-15.0 MHz and RF power up to 80 W. Induction coils with different numbers of turns, from 6 to 26, were used to ignite and maintain the inductively coupled RF discharge in the lamp bulb. The lamp ignition and operational parameters (such as coil starting and maintaining voltages and currents, lamp impedance and resistance, starting power and coil power losses) were directly measured. The transformer model of an RF inductive discharge was applied to calculate the discharge parameters: plasma resistance and current, plasma effective RF electric field and plasma Q-factor. The results of the calculations are in good agreement with the experimental data published elsewhere. Due to low power losses in the induction coil with large number of turns (26), the power efficiency of the lamp at the frequency of 2.65 MHz was high, 92%, which provided high lamp efficacy of 83 lumen per watt (LPW) at a RF power of 60 W.

Pulse modulated high-pressure caesium discharge lamp

The high-pressure caesium discharge has a favourable spectral distribution consisting of a smooth recombination continuum in the visible range. When operated on a continuous power source, the spectrum in the visible region is close to blackbody radiation; however, the lamp efficacy is restrained by the self-reversed resonance lines occurring at 825 nm and 894 nm. Pulse modulation significantly increases the core plasma temperature, suppresses the near-infrared segment of the spectrum, strongly enhances the continuous radiation in the visible region, and successfully avoids overloading (<40 W cm-2) the arc tubes. The spectrum in the visible appears to have the same shape as blackbody radiation when the lamp is operated on a multiple pulse modulated power source. The arc tube geometry, caesium/mercury compositions, and power supply waveforms were optimized for photometric performance through a series of comparison tests. The lamp efficacy increased with narrower diameter arc tubes, higher lamp currents, as well as higher current crest factors (ratio of current pulse peak to RMS current). The highest efficacy achieved for the lamp operated on the pulse modulated power supply was 46 lpw. The lamp exhibits excellent dimming characteristics and has a colour rendering index (CRI) very close to a thermal source such as a tungsten halogen lamp. This study provides a framework for the design of a new lamp/ballast system which features excellent dimming characteristics, a near-perfect CRI, an efficacy above 40 lpw, and long life. The application for this light source could be a replacement for a high-end tungsten halogen or a white high-pressure sodium lamp.