Spellman DXR3000/LC -- Help??

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Greg Courville
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Spellman DXR3000/LC -- Help??

Post by Greg Courville » Wed Apr 19, 2006 7:28 pm

The Spellman DXR3000/LC I bought on Ebay has arrived. It was well-packed in a huge box with an enormous quantity of urethane foam, and it looks to be in good shape. The unit weighs about 20-30kg, by my estimation... very heavy to carry around. The seller had no information on the unit other than that it was pulled from a working environment, and the Spellman rep I contacted told me that he would try to find a datasheet in the archives but never emailed back again. The rear-panel label says "INVERTER", "DXR-3000/LC", and "0-60kVDC, 50mA". The output appears to be floating -- neither side is tied to ground, as far as I can see. However, the two output wires are extremely thick, and the rubber insulation on them is rather thin. The strands themselves do seem to have a dark reddish tint to them, though the lighting conditions in here are rather bad so it's hard to tell for sure... could this be litz wire? If so, this would suggest that the output is high-frequency AC, and that this unit was probably meant to drive an external multiplier stack... which would be unfortunate. Then again, I could be wrong, so I'd appreciate opinions from others more experienced than I.
Attached are several high-resolution photographs showing the internals and front/back panels. You cannot see this in the photo, but under each of the 30 red-dipped wirewound devices (there are two stacks: one with 14, and one beneath it with 16) seen in the HV section is a small orange capacitor about the size of the middle segment of my pinky finger. I would really like to be able to use this beautiful unit in its original form, but I figure that in the worst case I've at least scored an awesome project enclosure, some great knob assemblies and panel meters, a whole mess of SCRs, a few large toroids, a big fat relay, a 2-pole circuit breaker, some high-wattage resistors, a handful of HV caps, a big DC box fan, etc.
I have access to a 220V outlet, but I'll need to find a line plug and cable, and before I even think about applying power, I'll need to find some cleaner way to terminate the output connections, and come up with a specific plan for investigation so I don't end up doing something stupid out of bored curiosity.
The most important thing I'd like to find out at this point is whether this is a self-contained supply, or merely a driver for a multiplier stack. Any insights the group can offer would be greatly appreciated. Also, if anyone has any experience with these older units (...or a manual, if I'm really lucky!), any information you can provide would be most helpful. Eventually I will have to figure out the function of the rear-panel terminals as well... terminals 8-9 and 10-11 on TB-1 (remote programming terminals, I presume) are strapped together, so the supply is probably already configured for local control via the front panel...
I look forward to your thoughts on this matter!
Attachments
HV_output.jpg
HV_output.jpg (561.05 KiB) Viewed 3520 times
HV_section.jpg
HV_section.jpg (952.58 KiB) Viewed 3520 times
overview.jpg
overview.jpg (934.2 KiB) Viewed 3520 times
front_panel.jpg
front_panel.jpg (878.61 KiB) Viewed 3520 times
rear_panel.jpg
rear_panel.jpg (725.77 KiB) Viewed 3520 times

DaveC
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Re: Spellman DXR3000/LC -- Help??

Post by DaveC » Thu Apr 20, 2006 12:24 am

Hi Greg -

I am almost certain you have gotten the Driver for a rather stout 60kV DC supply. I am reasonably familiar with Spellman supplies made over the last 10 yrs or a bit more... and this one seems to be lacking some necessary hardware.

The biggest clue is the absence of a high voltage receptacle or HV cable terminating inside. But check that carefully to be certain.

For 60 kV, Spellman used RG - 8/U heavy coax, or an Okonite Xray cable with Alden, Fed Std or other Xray terminations.

All is not lost, though, as you could build an air unsulated muliplier for this box to drive.

Dave Cooper

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Re: Spellman DXR3000/LC -- Help??

Post by Greg Courville » Thu Apr 20, 2006 2:15 am

Given a few good component deals, I'm confident that I could build such a multiplier stack, but the big issue would be getting the regulation and display circuitry to work properly given that I do not have data on the rear-panel connectors or the details of the original stack.
What would likely be the voltage range of the output of this unit? Up to a few kilovolts, perhaps? To those such as Dave above who have experience with these units, any clue how many stages the multiplier stack might have had? Having looked closely at the output cable, I'm almost positive that the individual strands are enameled, which suggests that the output is a high-frequency AC. What might be the frequency range this device operated at?
I will try to rig up the necessary measurement setup so that I can see what output, if any, I can get from this device. In the mean time, any further insights would be greatly appreciated!

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Re: Spellman DXR3000/LC -- Help??

Post by DaveC » Thu Apr 20, 2006 8:10 am

Greg - the Spellman multpliers are typically 10 kV per stage for the 80kV through 130 kV units. I am not certain what frequency they use, but probably between 15 and 50 kHz, possibly a bit higher.

The "Reverse Recovery Time" of the HV Diodes limits the frequency you can put into multiplier. Diodes need to turn off fully and the HV ones are stacks of typically 10 chips. The package Trr goes up as they are stacked. The best diode today are as low as 30 ns, but less costly parts go up to several hundred ns for Trr.

Google on High Voltage Diodes for a few choices, and be sure to check out is www.voltagemultipliers.com (they're in Tulare, CA) . Their products are about the best around They make their own diodes as well as various custom multiplier assemblies. Their catalog is a short course in multiplier technology. They are pricey, however.

Hope this helps a bit.

Dave Cooper

Greg Courville
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Re: Spellman DXR3000/LC -- Help??

Post by Greg Courville » Thu Apr 20, 2006 4:33 pm

Thanks Dave; I have requested the VMI catalog. I doubt I'd be able to afford anything they make, but hopefully it will be a useful resource nonetheless.
Am I correct in thinking that the voltage and current sensing is done externally in the multiplier unit, rather than by some sort of guesswork based on the voltage and current going into the multiplier? If so, I imagine that it would be hard to coax any kind of useful output out of the driver without something connected. Perhaps if I'm really lucky I can find someone who has a manual for it and will let me see it for less than $100 (what Spellman quoted me for a copy of the manual)!

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Re: Spellman DXR3000/LC -- Help??

Post by DaveC » Thu Apr 20, 2006 6:46 pm

Spellman's price for a manual does seem high, but perhaps its old enough to not be in their electronic files.

You're correct as to where current and voltage are sensed. These are at the multiplier itself. The HV from a divider within the potted multiplier assembly. That's how I build them, too. You can then make use of the natural voltage grading of the multiplier stack to help with shielding and electrical stress issues.

Current is generally sensed at the return lead from the external circuit to the multiplier low side (same for either output polar).
Some type of surge current detection is generally employed,as well, using either a small current sense transformer or equivalent circuit. This takes the drive off quickly in the event of a sparkover somewhere. One method uses a simple bridge rectifier with an RC circuit on the output to make a low pass filter whose output is roughly proportional to the peak detected current signal. This can then be used to trip off the drive to the main switching transistors.

You will no doubt need to rig up a dummy load to see if the internals of the inverter box are good. You should be able to do this with some ceramic high wattage resistors. I would suggest putting together something with a few hundred watts capacity... a couple of 100 watt lamps comes to mind... but what to use depends on the output voltage. You will need to fire it up some how to see what voltages it produces. The switchers will use the DC voltage, probably across midpoint to each end of the (missing) HV transformer to the multiplier. So the V pk-pk will be at least 2xVDC.

So... you need to make a few careful measurements and figure out a load resistance... remember if you use a lamp load, to allow for the 10 times increase in resistance as it lights. Might be better if you can find them to use some husky wirewound ceramics. The inductance may cause some ringing, but that shouldn't hurt anything


Have fun, and be careful...

Dave Cooper

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Re: Spellman DXR3000/LC -- Help??

Post by Richard Hull » Mon Apr 24, 2006 3:12 pm

You have quite a beast there. Such a full system is on the order of $10,000+ new. As noted above, it is a three pice system.

The controller
The stack
The cabling

Having just one item is close to having nothing. The stack alone would have been the best deal going. Having the controller alone will have you spending a gang of bread to utilize its full capability.

Again, as Dave said, good luck and be careful.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Andrew Seltzman
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Re: Spellman DXR3000/LC -- Help??

Post by Andrew Seltzman » Mon Jun 05, 2006 4:36 am

Here is your multiplier stack on ebay:
7625756522

Andrew Seltzman
www.rtftechnologies.org
Andrew Seltzman
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Greg Courville
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Re: Spellman DXR3000/LC

Post by Greg Courville » Mon Jun 05, 2006 12:01 pm

Yup, saw that the other day and was cursing my self for getting rid of the controller already. I would have kept it around, but I barely have room to move around in here, so the constant temptation to dump something and recover some money and precious living/storage space often has me selling something off only to realize a week later that I could have used it.
Oh well! I've got an NST and a string of 1N4007's which I can use for demo operation once the vacuum system is ready, and in the mean time I'll keep looking for a suitable HV supply or the components to build one. Small X-ray transformers such as those found in dental X-ray heads seem particularly appealing, though I think one would have to go to great lengths to cool one well enough for continuous operation. I've got around 500 1N4007 diodes, which are delightfully cheap (around $0.02/ea in quantity) and from which I should be able to make a decent rectifier by stringing them together under oil (although so far I've had no problems with an open-air string up to about 20kV). I also have a beautiful 25A variac which I'm dying to build into something, and a small pile of little "doorknob" style capacitors. It would be fun to build the supply, but I will of course continue looking for something premade that might be suitable.
Thanks!

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Re: Spellman DXR3000/LC

Post by DaveC » Mon Jun 05, 2006 7:37 pm

Greg -

You should be able to do quite a lot with the 1N4007's. Since you have lots of them, be real conservative in the voltage stressing, Stay about 50% of their 1000 PRV rating, and you should do fine.

They will work well at the mains power frequency, but probably can also run up to a few kHz, if you are conservative in loading.

Dave Cooper

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