Ricardo Paulino Marques

Impact of Current Crest Factor at High and Low Frequency Operation on Fluorescent Lamp Electrodes

The current crest factor (CCF) is a measure of wave shape distortion and indicates the potential for high peak current, which can damage the lamp electrode and reduce lamp life. The value of 1.7, which is regarded as an acceptable limit by the American National Standards Institute (ANSI) and International Electricity Commission (IEC) ballast performance standards is based on 50/60 Hz operation. High frequency operation involves different electrode operating conditions and the validity of this limit could be questionable. This paper evaluates the relative effect of waveform distortions at high-frequency and the low frequency amplitude modulation of high frequency sinusoidal waveforms on electrode emitter depletion with respect to 60 Hz sinusoidal current steady state operation. The emission of electrode mix is evaluated by barium line measurements and cathode fall monitoring on special-made lamps with clear ends

Current pulse fed high-pressure-sodium lamps

Spectral and photometric time-averaged measurements at nominal lamp power rating are presented for pulse operated HPS lamps of several manufacturers and different sodium concentrations. The choice of pulse and cycle parameters, which determine the optimal ratio between pulse and simmer powers are discussed. Spectra at various operating conditions as well as curves relating CCT, luminous flux and color rendering index with pulse cycle parameters are presented. Acoustic emissions were measured and are briefly discussed.

Sound Emissions From Pulse Operated High-Pressure-Sodium Lamps

Current-pulse-fed high-pressure-sodium lamps generate audible noise even if lamp power frequency does not excite longitudinal acoustic resonance modes inside the arc tube. This noise is caused by magnetostriction in conductive parts of the arc tube-supporting frame and in the wires passing through the seal of the outer glass envelope. Conductor dimensional changes effectively couple mechanical energy to the jacket. Photoacoustic effects also cause noise due to pressure waves in a thin air layer surrounding the lamp. This paper investigates experimentally both phenomena and quantifies their contribution in order to minimize acoustic emissions.

Electrode erosion in pulse operated high-pressure-sodium lamps

This paper investigates the electrode behavior of HPS lamps under pulse operation during vapor arc mode and thermionic state. Records of barium Ba II line (/spl lambda/= 455.4 nm) intensity emissions near one electrode surface were taken during the first 20s after lamp starting with different pulse parameters. The results are compared with measurements obtained with the lamp operating at line frequency.

An Alternative Optical Method for Acoustic Resonance Detection in HID Lamps

Acoustic resonances are observed in high-pressure discharge lamps operated with ac input modulated power frequencies in the kilohertz range. This paper describes an optical resonance detection method for high-intensity discharge lamps using computer-controlled cameras and image processing software. Experimental results showing acoustic resonances in high-pressure sodium lamps are presented.

Sound emissions from pulse operated high-pressure-sodium lamps

Current pulse fed HPS lamps generates audible noise even if the lamp power frequency does not excite longitudinal acoustic resonance modes inside the arc tube. This noise is caused by magnetostriction in conductive parts of the arc tube-supporting frame and in the wires passing through the seal of the outer glass envelope. Conductor dimensional changes effectively couple mechanical energy to the jacket. Photoacoustic effects also cause noise due to pressure waves in a thin air layer surrounding the lamp. This paper investigates experimentally both phenomena and quantifies their contribution in order to minimize acoustic emissions.

EEFL (External Electrode Fluorescent Lamp) driving methods.

EEFLs (External Electrode Fluorescent Lamps) are used as backlight source for large screen size LCDs. Since electrodes are outside of the discharge tube, lifetime is enhanced when compared with CCFLs (Cold Cathode Fluorescent Lamps) and a single inverter can drive multiple EEFL tubes and a compact design can be realized. EEFLs can be driven by both sinusoidal and square waveforms. Moreover, synchronizing the self-discharge time of the dielectric wall charge with the voltage rising and falling can enhance luminance. This paper presents luminance measurements for different driving alternatives and lamp voltages.

Light emission of electroluminescent lamps under different operating conditions

Electroluminescent (EL) lamps are flat solid-state ac driven devices in which light is generated by impact excitation to optical energies of luminescent centers in a Mn-, Cu- or Tb doped ZnS phosphor layer by high-energy electrons and radiant decay to ground state of these luminescent centers. They are useful in applications which require diffuse low level uniform illumination. This paper presents measurements of light emission and related spectra of EL lamps as function of operation frequency and sinusoidal voltage amplitude. The excitation of other voltage waveforms is also analyzed and parameters of the equivalent electrical circuit are presented.