Reduced Flickering of Metal Halide Lamps by Optimized Electrode Design

Fromm, D.C.; Hohlfeld, A.

doi:10.1080/00994480.1993.10748042

Cited by 8 publications

(14 citation statements)

References 3 publications

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“…In the experiments shown the observations already made in [2][3][4] are explained more clearly: the mode change from diffuse to spot occurs abruptly and is accompanied by a steep decline of the lamp voltage. It follows the current change with a time lag.…”

Section: Discussionmentioning

confidence: 51%

“…Observations on mode changes in HID lamps and their effect on lamp voltage have been reported for sinusoidal current in [2][3][4] and in slowly changing dc currents [1].…”

Section: Introductionmentioning

confidence: 99%

“…In the calculations, the work function of pure tungsten was used. (3) The real electrode rods carried wire-wound coils, which were loosely attached to the rod. In the calculations the coil was simulated as a massive cylinder with flat surfaces, in complete thermal contact with the rod.…”

Section: Introductionmentioning

confidence: 99%

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Cathodic arc attachment in a HID model lamp during a current step

Bötticher

Graser

Kloss

2003

J. Phys. D: Appl. Phys.

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Changes in the cathodic arc attachment mode during a current step are studied both experimentally under well-defined and reproducible conditions, and by finite element calculations. A transition from diffuse to spot and back to diffuse attachment is observed as the response to the step. Spot formation is identified experimentally by a sharp peak in the light intensity in front of the cathode and a steep decrease in the lamp voltage. Numerical three-dimensional solutions of the thermal-conduction equation in the cathode body exposed to nonlinear surface heating give good quantitative agreement of the time course of the observed changes in attachment modes. The model that describes the heating by the near cathode layer uses a simpler equation for the ion current density than other models in the recent literature. The model describes how an excess energy flux is created in the layer in front of a spot, which cannot be transported back to the cathode by the ion current and must, therefore, be supplied to the arc. The calculated integral excess power shows a time course similar to the observed light intensity.

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Section: Discussionmentioning

confidence: 51%

“…Observations on mode changes in HID lamps and their effect on lamp voltage have been reported for sinusoidal current in [2][3][4] and in slowly changing dc currents [1].…”

Section: Introductionmentioning

confidence: 99%

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Cathodic arc attachment in a HID model lamp during a current step

Bötticher

Graser

Kloss

2003

J. Phys. D: Appl. Phys.

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“…2 Present address: Philips Lighting B.V., Central Development Lighting, 5600 JM Eindhoven, The Netherlands. 3 Present address: Hella KGaA Hueck & Co., Dept. EE-4VE, D-59555 Lippstadt, Germany.…”

Section: Introductionmentioning

confidence: 99%

The boundary layers of ac-arcs at HID-electrodes: phase resolved electrical measurements and optical observations

Langenscheidt¹,

Lichtenberg²,

Dabringhausen³

et al. 2007

J. Phys. D: Appl. Phys.

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Arcs are operated in noble gases with sinusoidal and switched dc currents of different frequencies in a model lamp between tungsten electrodes with properties appropriate for high intensity discharge lamps. The sum of the cathode and anode fall, called electrode sheath voltage ESV(t) = uc(t) + ua(t), is determined by a variation of the arc length and the anode fall ua(t) by probe measurements along the arc axis and an extrapolation procedure. It is found that ua(t) adopts low, approximately constant values within a half cycle. Therefore the time variation of the ESV reflects that of uc. It was observed by high speed photography that a high value of uc after current zero crossing (CZC) may initiate a transition of the initially diffuse mode of cathodic arc attachment into a spot mode. It is accompanied by a breakdown of uc causing the formation of a voltage peak starting at current zero crossing. It is a prominent example of the so-called commutation peak (CP). By an adjustment of the operation conditions to a low uc the cathodic arc attachment remains diffuse during the whole half-cycle. It is also indicated by high speed photography that the arc constriction in front of the anode is relieved with increasing operation frequency. It is illustrated by measurements that commutation peaks may be removed by an increase in the arc current, a decrease in the electrode cooling, a reduction of the filling gas pressure and an increase in the operation frequency. Moreover it is demonstrated, that the formation of a CP is sensitively dependent on the electrode surface structure.

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“…If the re-ignition time for each electrode is different, then the electric current and consequently the intensity of the emitted light will be different for each half cycle. For network frequency supply of 50/60 Hz this leads to a flickering light of the same frequency (Fromm 1993). Mentioned effects and processes can change the shape or the position of the discharge in the arc tube or even both.…”

Section: Introductionmentioning

confidence: 99%

Light Flicker-Factor as a Diagnostic Quantity for the Evaluation of Discharge Instabilities in HID Lamps

Afshar

2006

LEUKOS

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There are some phenomena in High Intensity Discharge (HID) lamps which have the potential to make the discharge unstable. Discharge instability, can lead to some transients in light intensity or in its periodic form, to annoying light flickering. Instabilities appear in a vast range. Depending on the strength of the source of instability, it varies from a very slight deflection of sodium sheath to extreme deviations of conducting channel from its normal position which can extinguish the lamp as well. In order to detect the existence of such phenomena and predict their potential power, their effects and consequences on the light intensity can be analyzed. This has been done by using a tuned model of the human eye-brain system, to predict the perceptibility of the transient changes of light. The purpose of this paper is to introduce the 'light flicker factor' based on eye-brain model as a measure of discharge instabilities. The implementing method of the model and a proper measuring system for light flicker factor is being discussed. Some laboratory experiments to support this method of measurement are presented.

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Reduced Flickering of Metal Halide Lamps by Optimized Electrode Design

Cited by 8 publications

References 3 publications

Cathodic arc attachment in a HID model lamp during a current step

Cathodic arc attachment in a HID model lamp during a current step

The boundary layers of ac-arcs at HID-electrodes: phase resolved electrical measurements and optical observations

Light Flicker-Factor as a Diagnostic Quantity for the Evaluation of Discharge Instabilities in HID Lamps

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