Ingineria Iluminatului - Journal of Lighting Engineering - Prof. Florin ...

Figure 4 250 Watt HID lamp voltage and current
experimental oscillograms
Figure 6 Simulation oscillogram of the illumination
arc voltage drop U arc and the anode and cathode
areas voltage drops Uak for 250 W HID lamp
Figure 5 250 Watt HID lamp voltage and current
simulation oscillograms
20
10
0
-10
-20
[ oM ]
-30
-40
-50
-60
-70
dUarc/dIL
[ 1 дел = 1ms ]
Figure 7 Illumination arc differential resistance
change for one period of the supply voltage at
frequency 50 Hz
The simulation volt-ampere dependences in time are corresponding adequate with the experimental.
This model allows recording the voltage drop of the illumination arc as well as the anode and cathode
areas voltage drops. It can be seen that the illumination arc has strong negative differential impedance
from the graph on Figure 7.
The obtained during simulation 250 Watt HID lamp volt-ampere characteristics powered by
sinusoidal voltages with frequencies respectively 50 Hz and 500 Hz are given on Figure 8 and Figure 9.
During increasing the working frequency of HID lamp a volt-ampere characteristic linearization is
observed. It can be considered that the HID lamp differential resistance takes positive values at
frequencies higher than 500 Hz. This means that increasing the frequency of the supply voltage allows to
decrease the size of the induction ballast and to improve significantly the stability at work.
INGINERIA ILUMINATULUI 15-2005 31