Freddy Manders, Marco Haverlag Philips Lighting Eindhoven Paul Aben, Job Beckers, Winfred Stoffels...
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Transcript of Freddy Manders, Marco Haverlag Philips Lighting Eindhoven Paul Aben, Job Beckers, Winfred Stoffels...
Freddy Manders, Marco Haverlag Philips Lighting Eindhoven
Paul Aben, Job Beckers, Winfred Stoffels Technical University of Eindhoven
Optical study of the breakdown phenomenon in High Intensity Discharge lamps
Outline
Introduction HID lamps Background approach
Experimental Set-up Power supply Lamps under investigation
Experimental results DC ignition of low aspect lamps DC ignition of High aspect lamps AC ignition
Conclusions
Introduction
Experimental set-up
Experimental results
Conclusions
Philips
One of the biggest lamp manufactures in the world
In Eindhoven pre-development of all lighting sources
• Halogen• Fluorescent• Compact fluorescent• LED• HID • etc
USED FOR:
High efficiency High colour rendering
PRACTICAL APPLICATIONS
Stadiums Tennis courts Parking lots Automotive Shopping malls Beamers
Burner is filled with:
- Starting gas (Noble gases, e.g. Xe & Ar)
- Buffer gas (e.g. mercury)
- Radiation emitting substance (e.g. Na, Ce, Dy, Ca, …)
Introduction
Experimental set-up
Experimental results
Conclusions
Background
• HID lamps Ignition voltage • ~ 4 kV (300 mBar, pulse ignition, standard HID lamps)• ~ 18 kV (10 Bar Xe, pulse ignition, Automotive lamps)
• Issues• 1 st electron, small lamps ( Automotive, UHP)• insulation materials (cables, lamp cap, etc)• Safety issues, bigger lamps• More expensive electronics
• The lamp should always ignited
We need to lower the ignition voltage of the gas discharge
Introduction
Experimental set-up
Experimental results
Conclusions
Approach
Try to understand how breakdown in HID lamps happens
Study breakdown process in model lamps with an ICCD camera and change a few parameters
• Gas type (Ar / Xe)• Gas pressure (300 mBar, 700 mBar )• Length / diameter of the lamp• Positive / negative voltage• Voltage source (Pulse, AC)
Introduction
Experimental set-up
Experimental results
Conclusions
Experimental set-up
Introduction
Experimental set-up
Experimental results
Conclusions
Experimental set-upLamps
Voltage source
Pulse source of 5 kV with a rise time of 10 nsec.
AC voltage source from 25 kHz up to 3 MHz
-4
-3
-2
-1
0
1
2
3
1 1 0 0 1 2 0 0 1 3 0 0 1 4 0 0 1 5 0 0 1 6 0 0 1 7 0 0 1 8 0 0 1 9 0 0 1
• Low aspect ratio burners– Argon, p = 300 mbar, d =
7 mm
• High aspect ratio burners– Diameter = 4 mm– Argon and Xenon– electrode distance: 1.5 cm
and 2.7 cm– 300 mbar and 700 mbar
Introduction
Experimental set-up
Experimental results
Conclusions
Vo
ltage
(kV
)
Experimental results
DC pulse ignition of low aspect lamps
DC pulse ignition of high aspect lamps
AC ignition
Introduction
Experimental set-up
Experimental results
Conclusions
Low aspect ratio: Argon 300 mBar, -4.0 kV
0 max
6 ns
7 ns
9 ns
10 ns5 ns
12 ns
13 ns
14 ns
15 ns
0 ns
3 ns
4 ns
Introduction
Experimental set-up
Experimental results
Conclusions
Grounded side
High voltage
side
21 ns
19 ns
18 ns
17 ns
Low aspect ratio: Argon 300 mBar, -4.0 kV
• High voltage ionization expands spherical• High voltage ionization is not uniform, channels are visible, streamers.• Grounded emission becomes, because of the interaction with the wall
9 nsec
Introduction
Experimental set-up
Experimental results
Conclusions
-4.0 kV -3.0 kV -2.5 kV
7 nsec
11 nsec
16 nsec
17 nsec
21 nsec
16 nsec
29 nsec
40 nsec
51 nsec
59 nsec
20 nsec
41 nsec
59 nsec
73 nsec
99 nsec
Low aspect ratio: Argon 300 mBar
Introduction
Experimental set-up
Experimental results
Conclusions
Low Aspect ratio: Argon 300 mBar, -2.5 kV
• High voltage emission region expands spherical• High voltage emission region is diffuse, burner is almost
completely filled with ionization• No grounded electrode emission is visible
59 nsec
Introduction
Experimental set-up
Experimental results
Conclusions
7 nsec
11 nsec
16 nsec
17 nsec
2 nsec
6 nsec
8 nsec
11 ns
39 nsec
60 nsec
99 nsec
128 nsec
-4.0 kV +4.0 kV +2.5 kV
Low aspect ratio: Argon 300 mBar
Introduction
Experimental set-up
Experimental results
Conclusions
Low aspect ratio: Argon 300 mBar
• In all 3 pictures mechanism is streamer• Negative streamers are in general more diffuse.• +4 kV: clearly streamer mechanism• +2.5 kV: slower and more diffuse
8 nsec16 nsec 99 nsec
+4 kV-4 kV +2.5 kV
Introduction
Experimental set-up
Experimental results
Conclusions
Conclusions low aspect ratio lamps
Introduction
Experimental set-up
Experimental results
Conclusions
• At high negative over voltage (-4 kV) discharge is a streamer
• For lower voltage there is a transition to a Fast Ionisation wave (-2 kV)
• Negative streamers are more diffuse then positive
• Discharge always starts at powered electrode because of interaction with wall
High aspect ratio burners
•Argon, p = 300 mbar, d = 1.5 cm, V = +4kV
52 ns 94 ns
8 ns 58 ns 99 ns
15 ns 69 ns 107 ns
23 ns 75 ns 109 ns
25 ns 84 ns 121 ns
39 ns 85 ns
93 ns48 ns
0 nsIntroduction
Experimental set-up
Experimental results
Conclusions
High aspect ratio burners: Ar300 mBar, +4kV
• streamer along burner wall• very little branching• grounded emission expands spherical and is diffuse
85 nsec
Introduction
Experimental set-up
Experimental results
Conclusions
Ar 300 mBar Ar 700 mBar Xe 300 mBar
23 ns
52 ns
75 ns
85 ns
121 ns
109 ns
99 ns
23 ns
51 ns
71 ns
85 ns
115 ns
98 ns
89 ns
22 ns
39 ns
57 ns
85 ns
140 ns
135 ns
106 ns
High aspect ratio burners: +4kV
Introduction
Experimental set-up
Experimental results
Conclusions
• Ar300: little branching, intense emission at grounded electrode
• Ar700: much branching• Xe300: much branching, very little emission at
grounded electrode
High aspect ratio burners: +4kV
85 nsec, Ar 700 mBar
85 nsec, Ar 300 mBar
85 nsec, Xe 300 mBar
Introduction
Experimental set-up
Experimental results
Conclusions
97 ns 269 ns
9 ns 108 ns 272 ns
20 ns 143 ns 301 ns
21 ns 188 ns 303 ns
29 ns 212 ns 313 ns
39 ns 242 ns
257 ns54 ns
0 ns
320 ns
340 ns
High aspect ratio burners: Ar 700 mBar - 4kV
Introduction
Experimental set-up
Experimental results
Conclusions
• High voltage ionization (negative voltage) very diffuse and at a very low intensity
• At grounded electrode streamers are formed• Two different mechanisms during one discharge
257 nsec
Introduction
Experimental set-up
Experimental results
Conclusions
High aspect ratio burners: -4kV
Conclusion high aspect lamps
Introduction
Experimental set-up
Experimental results
Conclusions
• More interaction with the wall because the distance to the wall is smaller
• Positive discharge branch more then negative
• Negative discharge is more diffuse and slower
•The higher the pressure the more branching
• Xe branches more then Ar
Comparison of velocities at + 4 kV
velocity / (106 m/s)
d = 1.5 cm d = 2.7 cm
Ar300 1.9 ± 0.1 1.6 ± 0.1
Ar700 1.3 ± 0.1 1.1 ± 0.1
Xe300 1.7 ± 0.1 1.4 ±0.1
Xe700 1.2 ± 0.1 1.0 ± 0.1
Introduction
Experimental set-up
Experimental results
Conclusions
Introduction
Experimental set-up
Experimental results
Conclusions
1.2
1.2
1.2
1.2
velocity / (106 m/s)
d = 1.5 cm d = 2.7 cm
Ar300 1.9 ± 0.1 1.6 ± 0.1
Ar700 1.3 ± 0.1 1.1 ± 0.1
Xe300 1.7 ± 0.1 1.4 ±0.1
Xe700 1.2 ± 0.1 1.0 ± 0.1
Comparison of velocities at + 4 kV
Introduction
Experimental set-up
Experimental results
Conclusions
1.4
1.4
1.4
1.4
velocity / (106 m/s)
d = 1.5 cm d = 2.7 cm
Ar300 1.9 ± 0.1 1.6 ± 0.1
Ar700 1.3 ± 0.1 1.1 ± 0.1
Xe300 1.7 ± 0.1 1.4 ±0.1
Xe700 1.2 ± 0.1 1.0 ± 0.1
Comparison of velocities at + 4 kV
Introduction
Experimental set-up
Experimental results
Conclusions
velocity / (106 m/s)
d = 1.5 cm d = 2.7 cm
Ar300 1.9 ± 0.1 1.6 ± 0.1
Ar700 1.3 ± 0.1 1.1 ± 0.1
Xe300 1.7 ± 0.1 1.4 ±0.1
Xe700 1.2 ± 0.1 1.0 ± 0.1
1.2
1.1
1.1
1.1
Comparison of velocities at + 4 kV
Conclusions velocity measurements
Introduction
Experimental set-up
Experimental results
Conclusions
• Out of the camera pictures it is possible to calculate the velocity of the discharge. The speed are all in the order of 10^6 m/s which is normal for a streamer discharge
• The velocity results for the high aspect ratio lamps with 4 kV show that there are some relations:
The factor the velocity changed
Distance between electrodes changed from 1.5 cm to 2.7 cm
1.2
Gas pressure changed from 300 to 700 mBar
1.4
Gas type changed from Ar to Xe
1.1
Breakdown voltage for AC ignition for high aspect lamps
0 50 100 150 200 250 300 350 4001400
1600
1800
2000
2200
2400
2600
Ign
ition
vo
ltag
e (V
)
Frequency (kHz)
300 mbar Xenon 700 mbar Xenon
-29%
-26%
Introduction
Experimental set-up
Experimental results
Conclusions
For DC pulse ignition ~ 4 kV is needed to ignited the 700 mBar Xe lamps so AC lowers the breakdown voltage with ~ 50 %
Experimental results (AC ignition - Xenon)
50 100 150 200 250 300 350 400 450
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05N
orm
alize
d ig
nit
ion
vo
ltag
e
Frequency (kHz)
300 mbar Xenon 700 mbar Xenon
Two regimes in which the burners can ignite
Introduction
Experimental set-up
Experimental results
Conclusions
Experimental results of 300 mBar Xe (AC ignition)
Low frequencies: Discharge travels via the wall Looks like pictures of pulse ignition (streamer-like channels, branching)
High frequencies: Discharge travels through the gas Ionisation channel has the shape of a streamer …
30kHz
80kHz
140kHz
200kHz
300kHz
400kHz
Introduction
Experimental set-up
Experimental results
Conclusions
700 mBar of Xe
Maximum velocity of ionisation front: smv 4
max 10)3.04.1(
Shape looks like a streamer-like discharge Maximum velocity of the ionisation channel is in the order of those in Townsend discharges.
Contradiction:
300 mBar Xenon at 200 kHz
Introduction
Experimental set-up
Experimental results
Conclusions
Introduction
Experimental set-up
Experimental results
Conclusions
Conclusions on AC ignition
AC ignition voltage about 50-60% lower than pulse ignition voltage Ignition voltage is a decreasing function of frequency
At relatively low frequencies the ionisation channel travels along the wall At relatively high frequencies the ionisation channel travels through the gas
Ionisation channel builds up step-wise over many periods Ionisation channel only grows during voltage maximum
Possible explanation: Due to alternating E-field more charged particles stay in the volume, and are able to ionise for a longer time.
The higher the frequency, the more charged particles stay in the volume.
Thank you for your attention!