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Xenon Imax Projector Bulb

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twenglish1

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Someone brought this bulb in to the junk yard, a friend of mine works at, so he bought and gave it to me cause he knew i would find interest in it, after disassembling it i found a part number which lead me to the specs, 2400 watts and 73,000 lumens!! Now i will need to find a way to power it, datasheet says roughly 100 amps at 24vdc, and of course being an arc lamp it will require a high voltage pulse ignition circuit, my first thought is a tig welder might be a simple way to power it as most have a high voltage arc starter
 

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FvM

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xenon power supply must be stable constant current, and ignition voltage is high kV range unlike tig welder. I don't think that welder supply will do.
 

Dan Mills

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Three things:

Firstly a safety warning, that is a HIGH Pressure lamp (Probably ~30ATM when running) and these things are known to fail 'energetically', leather apron, chainsaw trousers and a full face mask is indicated when working around short arc Xe (Also, they are an ocular hazard and some lack UV filtering).

You will need a lot of cooling air at considerable pressure, overheating will also cause an explosion.

The usual approach to firing these up is with a series injection igniter transformer with the primary driven by a spark gap/cap discharge arrangement, it is helpful to arrange to dump a cap charged to several hundred volts thru a few tens of ohms into the lamp as it strikes in order to initially heat the surface of the cathode to overcome the work function.

Supply is DC, from a current source, with relatively low ripple, and welding sets have been used for the purpose upon occasion (With additional cap banks and igniter/boost supplies), 12 pulse rectifiers with inductive ballast were the way it was historically done (Modified carbon arc supplies were commonplace in older cinemas).

Have fun, but be careful out there, these things are high energy systems.

Regards, Dan.
 

twenglish1

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Sorry did not realize at first you mentioned about using a transformer to coupled the hv, I will try to draw up a schematic of a power supply and high voltage starter
 

twenglish1

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Could anybody offer any pointers on designing the coupling transformer for the high voltage start? i have a dc welder which will produce at least 100 amps, might try to build a hv start circuit to be coupled into one of the welder output leads, my thoughts were a flyback or ignition coil driver, driving the coupling transformer through a spark gap, with its secondary in series with the high current circuit, however the problem then becomes that i will need to protect the welder circuitry from the high voltage pulses as it is an inverter welder and i would hate to destroy the switching devices, any suggestions?
 

SunnySkyguy

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Specs on this lamp are;
35kV ignition min
100ns ignition min
23Vdc nom +3/-4V
104A nom +6/-29A
2.4kW +0.3/-0.6 input
0.6kW output radiant.
Focal length 47.88mm
arc gap 1.91 mm ( Half wavelength resonance)
Seal temp 150'C max
 

twenglish1

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Those were the specs I found, forgot to post an update, I watched some videos on YouTube of people powering them using dc arc welders with an added hv start circuit, I may give this option a try depending on how clean the dc of my welder is, gonna check it with my scope, still got some research to do on the hv start, mostly the coupling to the low voltage dc part
 

GeorgesWelding

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A _quality_ inveter TIG welding machine should have no problem providing a smooth enough current source to power one of these, even older transformer machines had a fairly stable output current, at least the really huge(~800lbs ie:LOTS of copper and iron) ones I've dealt with did. The 35kV striking voltage will have to come from somewhere external though, and I'm not sure how you would go about protecting the welder from that magnitude of a high voltage being introduced. Most of the newer inverter TIGs that have the HF/HV arc starter generally operate in the area of 1-3kVAC at a frequency >1MHz and generally use a fly-back + cap + spark gap setup, although I have seen a couple that are entirely solid state and do not have a spark gap.

The highest strike voltage I've ever seen from a TIG machine was from a 415A-AC(325A-DC) transformer based machine I used to own that was manufactured in the 1980s, using mostly 60s and 70s era technology. It would put around 6.5kVAC at around 5MHz(hard to get a solid reading) across the output leads with the arc starter intensity cranked to the max, in the presence of the argon shielding gas. Normal settings would yield around 3.5kVAC at the output leads. Since four large diodes were the only semiconductors in the high-current path, simple high-voltage RC pass filters were used to provide a path for the HV while keeping it away from the diodes. The filters were set to appear as low impedance to the HV/HF while effectively being an open circuit to the high-current/low-voltage DC or AC welding power. Not sure how well this would work on an inverter though as it would depend entirely on how the output is designed.

I imagine that using a flyback transformer from something like a large CRT computer monitor or an ignition coil might be able to provide enough voltage to strike one of these lamps. If it's fed through a cap/spark-gap setup to really boost the oscillation frequency(up into the MHz range) then designing the coupling transformer is super easy. Take something like a 2.5" piece of PVC(plastic) pipe, wrap the negative welding lead around the pipe with around 10-12 turns. The pipe section must be long enough that the winding is only one layer with no gaps between the turns. Then get a piece of proper high-voltage wire(like the type used to provide the post-acceleration voltage to a CRT) and wind it directly on top of the welding lead. It's easy to keep track of the turns if you wind the smaller HV wire in the grooves left by the tight winding of the welding lead. I'd start with a 1:1 ratio and if it doesn't provide a high enough voltage, remove 1 turn at a time from the HV wire until the output voltage gets to where you need it. Keep in mind that you'll need at least a couple turns on the HV winding to provide adequate coupling. A hand full of broken ferrites from old SMPS transformers tossed inside the plastic pipe will also help with the coupling a little bit if it's absolutely necessary. This is essentially how the coupling transformer is designed on every TIG machine I've ever been inside although they usually don't have a plastic former.
 

twenglish1

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The only tig machine i used was a fairly large lincoln, i think it was a 250 amp model or somewhere around there, anyway it would throw a 2 inch spark with the high voltage arc starter, unfortunately i dont have access to that machine anymore(highschool shop) i tried doing some testing on a smaller xenon arc lamp from an old projector tv, i connected it to my dc inverter welder and tried to strike it with a stungun, it would flicker but it would not hold an ark, however i think there is already something wrong with the welder, i purchased it used and haven't been able to get it to actually weld, and the OCV is only 60volts where the name plate says it should be 80, might start a new thread on this topic to maybe see if i can get some help troubleshooting it, anyways back on topic, i had been thinking about trying what you just suggested i saw it done before on a homemade HV arc starter(https://www.casano.com/projects/hfstart/index.html) pretty simple and it seems like it should do the trick if i can get a good source of high current DC
 

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