Author Topic: Metal Halide Parking Lot Shoebox Startup  (Read 1006 times)
flyoffacliff
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Metal Halide Parking Lot Shoebox Startup « on: April 25, 2015, 04:28:19 PM » Author: flyoffacliff
Started recording right after they came on. Anyone know the fixture? Why does the one warm-up so much faster?

http://www.youtube.com/watch?v=1CSiuWgudlw
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dor123
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Re: Metal Halide Parking Lot Shoebox Startup « Reply #1 on: April 26, 2015, 04:36:43 AM » Author: dor123
Regarding to the difference in run-up rate of both lamps: If each MH lamp is of different brand, or one is older than the other, this may cause each lamp to run up at different times. Some MH lamps runs up faster than other MH, mainly if one lamp is probe-start and the other is pulse-start, or both pulse-start with different arctube design.
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Medved
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Re: Metal Halide Parking Lot Shoebox Startup « Reply #2 on: April 26, 2015, 08:27:28 AM » Author: Medved
The placement will suggest something like 400W or so, so most likely probe start on a CWA.
These ballasts feed the lamps by pretty constant current, so the real power delivered to the lamps when they are still cold is rather low and it increases only as they warm up.
That means they start to warmup veeryyy slooowlyyy, only when "tipping over" certain temperature/pressure state, the warm up speeds up.
Here what differs is the time, when the lamps reach the "tipover" point, so the difference could be really tiny. It could just be as tiny as a bit different mounting position (slightly different angle of the starting probe,...).
Or just random production tolerance variation, batch-to-batch difference, different level of wear, till even different arctube construction of different maker, really all is possible...
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flyoffacliff
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Re: Metal Halide Parking Lot Shoebox Startup « Reply #3 on: May 03, 2015, 05:23:05 PM » Author: flyoffacliff
The placement will suggest something like 400W or so, so most likely probe start on a CWA.
These ballasts feed the lamps by pretty constant current, so the real power delivered to the lamps when they are still cold is rather low and it increases only as they warm up.
That means they start to warmup veeryyy slooowlyyy, only when "tipping over" certain temperature/pressure state, the warm up speeds up.
Here what differs is the time, when the lamps reach the "tipover" point, so the difference could be really tiny. It could just be as tiny as a bit different mounting position (slightly different angle of the starting probe,...).
Or just random production tolerance variation, batch-to-batch difference, different level of wear, till even different arctube construction of different maker, really all is possible...


Thank you for explaining everything clearly. Just wondering, how did you know it was 400W probe start on a CWA?
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Medved
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Re: Metal Halide Parking Lot Shoebox Startup « Reply #4 on: May 03, 2015, 10:58:06 PM » Author: Medved
Just the way how it warms up suggest for a constant current feed. And the only wide spread ballast behaving as a constant current source is the CWA. And because the pulse start lamps need at least some arctube temperature stabilization (the current should reduce at higher arc voltages), they are not used with CWA, so I have guessed for the probe start.
Moreover that combination is the most common for that output in the US as well...
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