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Hi all, I am in the process of restoring my film equipment and have a question about electrical things. I did a little digging and discovered that it’s possible to power a xenon lamp with an arc welder inverter. Fantastic! - BUT there’s no igniter to hook it up to, then comes the issue of cabling length, etc. The igniter currently in there isn’t responding but I don’t think it’s bad. It made the familiar clicking sound before. Is there a way to engage it separately and connect it to the lamp and the inverter arc welder to the igniter and have it hooked up to some sort of momentary switch? I explained my issue in an earlier post about everything going on with this lamphouse. How would I go about extending the lamp lead cabling to reach outside of the projector lamphouse, and for that matter where would I even find the kind of fiberglass insulated heat resistant cable that it is currently hooked up into inside? How does the igniter get power? Is it from the DC current that would go to it? Also, and this is the final question I can think of: is it possible to hook up the lamp leads back into the rectifier and connect the inverter arc welder directly into those leads? I’m not sure if this would be safe but then again I know the rectifier spits out DC from AC anyway? I haven’t tried this though because it could possibly be the dumbest and least safe thing anyone has ever done in the history of film projection! I’m trying to keep costs to a bare minimum. I have already tried other sources of illumination and want to stick with this high power xenon.
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There's a difference between something being "possible" and something being "practical."
Yes, you can use a welding rectifier to power a xenon lamp but with two caveats.
1) The duty cycle of a welder is short. Maybe a minute or two, powered on, followed by a minute or two powered off.
I don't think that a welder would stand up to continuous duty for two-plus hours. It'll probably overheat and self destruct.
2) I don't know whether a welder's output is capable of putting out clean, DC power. I'm sure that there is a lot of ripple and overall variation in its voltage and current. Too much ripple or too much variation can and WILL destroy a xenon lamp on short order... Possibly even explosively!
Welding doesn't require clean, stable DC for long periods of time like movie projection does.
I suppose if you can find a welder that's up to spec, you could experiment but don't say I didn't warn you.
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For an interesting take on this you may want to search the Applied Science channel on youtube. He did just what you are wanting to do, although he uses his for a 1kw xenon searchlight built in a trashcan. There are a few videos, just search around. I'll warn you, its an internet rabbit hole, this guy is brilliant.Comment
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There are plenty of used xenon power supplies available some very cheap or even free if you look around. In order to make what you propose work you are going to need to install filtering capacitors and capacitors to build up the open circuit voltage needed to light the lamp. It is really not a project for someone who isn't really experienced with these power supplies and electronics/electrical components. It would be very easy to start a fire or worse these are lethal amounts of power and playing with large capacitors without the knowledge to do it safely can lead to death.Comment
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I was told many years ago that the output of an arc welder was not filtered enough for a xenon bulb. I wouldn't try that. Like Sean said, there are plenty of used power supplies sitting around looking for a home.Comment
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There were many arc welders used as xenon rectifiers over the years alot were commercially rebadged. Imax rectifiers were usually Miller arc welders. But one must add more filtering a boost supply and adjust to the duty cycleComment
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Wasn't there an extensive thread about this on the "old" FT website?
If my memory is correct, two of the biggest problems with using a welder type supply, as others have pointed out, are the duty cycle and lack of filtering you need for a xenon (or even carbon arc) supply.Comment
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Yes, I remember something along this line on the old forums. But as Gord said... There is a lot to add to a welding rectifier to get it to work properly. Xenon is very sensitive to ripple, and high ripple = short lamp life. By the time you get done adding all the crap to a welding rectifier, you may as well just look for a used xenon rectifier that fits your size lamp.Originally posted by Jim Cassedy View PostComment
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Our Thai friends tend to use this quite often, and modify welding inverters for Xenon operation.
For up to 2 kW, inverter arc welder cabinets can do the job quite well. They are basicly current regulated DC supplies based on switcher technology.
Electrically even the smaller ones are designed for around 2.5 kW (20A max / 120V 10A/ 240 V mains), as mentioned before, the duty cycle is limited by thermal capacity.
The duty cycle is marked on the box, the continuous capacity stated by the 100% current. For the smaller non commercial Home Store types, this is around 50 A, 1 kW.
It fits quite well for Xenon operation, as the output voltage is limited to around 25 - 30 Volts, the actual burning voltage of a small Xenon lamp between 19 and 25 Volts.
If there wasn't a "BUT". To safely ignite, a no load voltage of around 100 V is required, sometimes with a little power capacity, to feed an auto ignition relay set in the lamphouse, or
one of the modern DC feed single pulse igniters, used in the last generations of movie projectors or found in digital cinema projectors. This could require more efforts.
To gain that 100 V voltage, a small capacitor (like 220uF/120 V) across the output might work, as there are overlayed spikes from the switcher in that region on the output voltage,
filtering for an arc welder is not required. These spikes do not outlive the feed cables and the igniter coils,
For manual ignition it works in most cases, turn on welder, wait a couple of seconds, use momentary pushbutton connected in series with igniter primary transformer.
Using a kilowatt bulb in most cases works quite nicely with a small inverter welder. For larger bulbs, 2,5 kW and on, the 25 V safety limitation will not be sufficient.
Higher loads than the 100% stated current, might lead to thermal shut off, unwanted in movie showing. That means, you must improve the cooling by adding extra fans, cooling fins, or other measures. Something definitively not good to be done by someone not educated in electronics design. You are dealing with high power high voltage circuits, that can be lethal to touch.
In that case a larger home style, or a commercial grade welder (rated for higher duty cycle) with higher 100% current is the better way. These also have a better filtered DC on the output, as they use a better design with more storage capacitors.
And last, remember AC welding transformer (the super heavy ones) do not work, they destroy the lamp immediately.
But, afair, this all was discussed in this forum in detail. Use the search.Comment
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One important thing also, specialy cheaper ones tend to have bad ac filtering. So you can have noise on ac lines generated by welder all around.........i remember using some 300eur one 10year ago did make so much noise on ac line that it was almost impossible to use any kind audio equipment in the room while lamp was on
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