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Topic: Bulb Current

Tim Sherman
Expert Film Handler

Posts: 125
From: North Ridgeville, OH, USA
Registered: Aug 2000

posted 09-24-2000 09:29 PM

So i was just curious what is the normal current rating on some of the xenon bulbs i run a drive-in and we run orc bulbs. one is a 4,500 watt and run that at 140amps the other is a 5,000 watt and its run at 150 amps. what is the recomended amperage for these bulbs? Or should i use ohm's law and take a voltage and amperage reading multiply them together and until i get the proper wattage? and ajust accordingly until it all matches?

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John Wilson
Film God

Posts: 5438
From: Sydney, Australia.
Registered: Dec 1999

posted 09-25-2000 12:33 AM

I'd say you're at least 10 amps over power on both of those...maybe even a little more.

Normally, in the xenon box there's a rated amp reading indicated.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 09-25-2000 08:04 AM

In every brand of xenon that I know of there is a card that shows the minimum and maximum current. They also show the current and voltage that the lamp was tested at before it left the facory.

I'd go by that card unless you have a good reason not to.

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 09-25-2000 10:27 AM

Not to be picky-picky, but one should also check the current rating on the power supply, so as not to overload it.

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 09-25-2000 04:03 PM

All above is correct. My experience tells me that current is the most important factor to watch, and refer to the literature with the lamp as guidelines to follow.

As the lamp ages, the arc gap will increase as the cathode tip burns away. As the gap increases, the voltage will go up.

Wattage is an interesting number to observe but you don't necessarily want to follow that as a controlling guideline. Better to observe the current range of the lamp.

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Tim Sherman
Expert Film Handler

Posts: 125
From: North Ridgeville, OH, USA
Registered: Aug 2000

posted 09-25-2000 07:31 PM

I am running them at the wattage that came on the card in with the bulb. On the 5,000 watt it said it was tested at a nominal amperage of 150amps withch is what i have it set at. someone told me that the nominal was just for testing perposes and was only like 85% of the rated current. so im not sure if this is true or if i sould keep it running at 150 amps i bulb only has a couple hundred hours on it so it is still pretty new. maybe i'll just have to contact the manufaturer. anyone know the number of orc (or i think its perkin elmer making the bulbs now)

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"Come on out to the drive-in and spend a night out with the stars"
ME!!

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 09-25-2000 09:12 PM

I'd say that if you're burinig it at the current listed on that card you aren't hurting it any.

There should also be a listing for minimum and maximum current. Anywhere in that range should be fine. You can vary it as needed for your theatre as long as you use common sense.
(Don't go 150 amps just because the mfg. says you can when all you need is 120 amps to light your screen.)

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 09-25-2000 09:32 PM

Lamps and lamp power supplies are like hot dogs and hot dog buns.

They sell hot dogs in packages of eight, but the buns are in packages of 10. They don't match.

Same with lamps and lamp power supplies. The current ratings don't match, so you either can't get the lamp up to it's full current rating, or you can go too far...

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 09-26-2000 07:25 AM

Randy has a good point; use the amperage you need to achieve proper illumination on screen. The problem is to determine that illumination level -- most booths and operators are not equipped with spot meters. We're also usually in a position where the correct light level was just about everything you could get out of the system.

If the theatre was done right in the first place, there's a little "head room" that allows for some natural degradation in the system -- new bulbs are brighter than old bulbs, screens get a little dusty and less reflective, etc.

I always followed the policy of running a lamp around 80-85% of it's maximum value when new. That allows the current to be increased through the life of the lamp to maintain somewhere near constant illumination.

Lamp manufacturers do different things in rating their lamps. Some give a current range: maybe a 4kw runs from 135-150. Others used to give a "nominal" value, with a plus/minus range; i.e. maybe a 4kw would be 140A +/- 10%.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 09-26-2000 01:41 PM

Some of the xenon lamp manufacturers publish product listings of their lamps, that include the recommended operating current range. For example, here is an on-line listing for the Osram XBO 5000 W/H OFR lamp:
http://ecom.sylvania.com/osicatalog/multiresult.asp?Item=69315

Clicking on the "Product Info Bulletin" shows all the technical data you need. If you can't find a listing, contact the lamp manufacturer for a data sheet for the lamps you use. Exceeding the maximum current greatly increases the risk of catastrophic explosion. Running below the minimum current shortens the life of the lamp (premature blackening), and can cause unstable operation and ignition difficulties.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

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Glenn Conatser
Film Handler

Posts: 73
From: Northern California
Registered: Aug 2001

posted 06-27-2002 06:32 PM

When adjusting the amp setting on a Christie CC40 lamphouse to get the proper amount of current i noticed a couple of houses are running just a little bit over. Im running a Christie 3000 watt bulb when the max current listed is 110 amps and a couple are running at 112 to 113. Is this going to cause any problems or shorten the bulb life significantly. All the others are running at around 108 to 110.

Thanks,
Glenn

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 06-27-2002 06:48 PM

Maximum is just that MAXIMUM.

If you verify that your current on a 3KW lamp is indeed over 110amps, you are playing with fire. Sure it is only 2% over but it is over none the less.

Since you have a CC-40U, why not set the internal links to "LOW"...that SHOULD get you in range.

Steve

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"Old projectionists never die, they just changeover!"

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Glenn Conatser
Film Handler

Posts: 73
From: Northern California
Registered: Aug 2001

posted 06-27-2002 10:28 PM

Actually Steve the settings where on low and we could only get 95 amps with the current setting at 6. So we changed the taps to high and set the current knob back to one before we turned it back on. 103 to 105 amps at 1 on the current knob is what we where getting when we switched it back on. I turned it up to 2 and it went upto 112 to 114 amps. Im just gonna back off one click on the current knob tomorrow and well be back in range.

Thanks for the warning.

Glenn

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 06-27-2002 10:58 PM

Next trick on the Christie...with the links on "HIGH" you can move the input from 208 to 230 to drop the current as well (the 208/230 taps only have an affect when you are on the "high" lnks).

Steve

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"Old projectionists never die, they just changeover!"

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