How many start ups is an HID bulb capable of?

I know that generally HID bulbs are rated at a few thousand hours, but that is largely dependant on how many times you turn it on and off. How many individual startups is an HID bulb normally good for? (specifically, the standard 35 watt like you might find in an X990)

BatteryCharger said:

I know that generally HID bulbs are rated at a few thousand hours, but that is largely dependant on how many times you turn it on and off. How many individual startups is an HID bulb normally good for? (specifically, the standard 35 watt like you might find in an X990)

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I cannot speak for the cheaper Asian bulbs which I believe (?) that unit comes with. For Philips, Osram, GE bulbs, doing Cold starts is at least 50,000 starts. The overdriven starting, typical with this technology is 75 to 100 watts initialy to speed up the warm up phase of the plasma. Once steady state is reached after 15-25 seconds it has been ramped down to 35 watts at the bulb.

2/3rds of the way down this page there is a graph showing life over starts per hour. Eyeballing it you get around 2000 hours with 5 starts per hour (12 mins per start). The life increases to 3500 hours if the number of starts per hour is reduced to 1 (1 hour per start). Increasing the number of starts per hour to 20 (3 mins per start) the life drops to only 1000 hours.

That_Guy said:

2/3rds of the way down this page there is a graph showing life over starts per hour. Eyeballing it you get around 2000 hours with 5 starts per hour (12 mins per start). The life increases to 3500 hours if the number of starts per hour is reduced to 1 (1 hour per start). Increasing the number of starts per hour to 20 (3 mins per start) the life drops to only 1000 hours.

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If a hot (steady state) lamp is shut down and restarted within 1/2 second, the effect on lamp life is negligible. The plasma state is still active and the impedance is still low and does not require very high voltage to reestablish the arc. Doing the math above of 20 cold starts per hour with 1,000 hours is 20,000 starts. We have done this testing on GE bulbs Not Philips which are the provider of the above quoted data by Nucon. We have found the GE bulbs to be superior and more robust than the Philips or Osram. They also cost 20% more than either Philips or Osram D2S bulbs. They also have a higher lumens maintenance over the life.

XeVision said:

If a hot (steady state) lamp is shut down and restarted within 1/2 second, the effect on lamp life is negligible. The plasma state is still active and the impedance is still low and does not require very high voltage to reestablish the arc.

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Thanks for that, I have often wondered about that myself. Reading here and elsewhere you get the impression that hot-striking the lamp bad and that you should wait a while before re-striking the lamp to minimise damage. However, I thought that hot-striking the lamp would be less bad than cold-striking the lamp because the lamp is already warmed-up. Thanks for confirming what I have often wondered!

That_Guy said:

Thanks for that, I have often wondered about that myself. Reading here and elsewhere you get the impression that hot-striking the lamp bad and that you should wait a while before re-striking the lamp to minimise damage. However, I thought that hot-striking the lamp would be less bad than cold-striking the lamp because the lamp is already warmed-up. Thanks for confirming what I have often wondered!

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If you wait more than a second it is harder on the bulb. Maximum restrike voltages as high as 25 KV are required.

Humm, ok. Is it really that much harder on the bulb? If it's hot the salts are already vaporized so all the ballast has to do is re-strike the arc. If it's cold it has to strike the arc, then drive the lamp at 75W to accelerate start-up, drive higher current through the electrodes due to the lower voltage across the arc, and vaporize the solid halide salts. This sounds much more stressful to me.