Film-Tech Forum ARCHIVE: Switching Pwr Supplies and Carbon Arcs

This is topic Switching Pwr Supplies and Carbon Arcs in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Frank Angel (Member # 248) on 07-28-2011, 04:19 PM:

Can a typical Switching power supply be adapted to power a carbon arc, say a Peerless Magnarc? It is burning 80smps now, a little under 3600w. Can, say, a Strong Xetron supply be used to power the arc if a ballast resistance is inserted so as not to short the supply when striking the arc?

Posted by Louis Bornwasser (Member # 3063) on 07-28-2011, 07:41 PM:

Xenon volts are about 24 volts dc. Carbon voltages are 2 times higher for copper coated and about 65 volts for rotating. Louis

Posted by Monte L Fullmer (Member # 2797) on 07-28-2011, 10:44 PM:

Wow,no wonder why xenon is cheaper to operate. "Gennies" and tungar bulb rectifiers really gobbled up the line current real bad for less results.

Posted by Ken Lackner (Member # 1002) on 07-29-2011, 06:35 AM:

quote: Frank Angel
a Strong Xetron supply

Was "Xetron" a typo?

Posted by Sam D. Chavez (Member # 1841) on 07-29-2011, 09:24 AM:

65 Volts? This must be open circuit and not under load. It has been a long time since I worked on lamps but I seem to remember 29 Volts across a running rotating 11mm carbons in a Stong Futura lamphouse. 29 Volts x 100 Amps = 2,900 Watts which sounds about right.

There are a couple of systems running in the Bay Area I can check.
I don't know of anyone who has attempted this modification.

Posted by Louis Bornwasser (Member # 3063) on 07-29-2011, 01:25 PM:

8mm and 7mm neg is 60-65 amps at 41 volts;

11mm is 115 amps at 63 volts.

I am simplifying the infor from an old National Projector Carbon Bulletins binder.

It HAS been a long time. Louis

Posted by Tony Bandiera Jr (Member # 2365) on 07-29-2011, 03:57 PM:

Seeing as how Strong switchers can barely handle Xenon bulbs reliably, what do you think the outcome of trying to strike a carbon's arc will be? [Roll Eyes]

And remember that Xenon supplies start off with a high open-circuit voltage.

Posted by Mark Gulbrandsen (Member # 72) on 07-29-2011, 09:12 PM:

You can arc weld with the output of a Krell Amplifier so it might work with a switcher if you have a correctly sized ballast resistor in series. I have also heard of running Xeon off of the old MG sets. That was pure DC.

Mark

Posted by Tony Bandiera Jr (Member # 2365) on 07-29-2011, 09:14 PM:

I too have heard of running Xenon off of MG sets...once the bulb is lit it is supposedly going to last longer on MG output as the DC is more "pure".

Posted by Louis Bornwasser (Member # 3063) on 07-30-2011, 08:28 PM:

In the old days, when Christie had a xenon conversion for the Magnarc, they also offered a ballast for the MG set. Worked OK.

We're working on a xenon power supply that is comprised of all those old Kelmar DC supplies in series parallel. Let's see: 5 amps, I'll need 16 to reach 80 amps. Then 3 sets of those to reach 25 volts. Not bad, 48. That's about the amount I have. louis

Posted by Robert Throop (Member # 61) on 07-31-2011, 12:40 PM:

Why not get a power supply designed for the job? There must be plenty of carbon arc rectifiers to be had.

Posted by Frank Angel (Member # 248) on 07-31-2011, 04:15 PM:

Because I am finding that lately in my older years, I tend to evaluate equipment based on what I can lift easily. [thumbsup]

Posted by Mark Gulbrandsen (Member # 72) on 07-31-2011, 08:10 PM:

Seems like Louis is doing the same thing! Those Kelmar supplies only weigh in at about 5 pounds each. Hey, I only have two more DP-70 to remove from service then I'm through moving those...