Matt’s Power Supply Upgrade

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Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Time for an update! I’ve been busy with alot of other projects but decided to get the fusor back online with a power supply upgrade.

I’m using two of those x ray transformers (driven at 40khz) in parallel and under oil to drive the new 7 stage multiplier. Since it’s been offline for awhile, I’ve been taking it somewhat easy before letting it rip:

Running at 10microns, I have pushed it up to 45kV and 20mA. After a few minutes, the fusor is pretty hot and the cathode is white, so I let it cool down. Power supply doesn’t show much stress other than the warm heatsink that the cm300dy is mounted on.

Over the next few days, I’ll keep pushing voltage higher and higher to see just what it can do.

-Matt
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Down to one transformer now. Had an internal flashover in one of the coils. Upon inspection, the secondary punched through the coil form and arced to the grounded shield that is between secondary and primary. Primary was undamaged. I was pushing close to 1kW (around 60kV and 17mA or so).
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Richard Hull
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Re: Matt’s Power Supply Upgrade

Post by Richard Hull »

Yes, 60kv has a way of transporting itself about the world. This is a level where super human effort is required to have things run smoothly. With real power behind 60kv, burning stuff up is the order of the day. All the best in keeping that last transformer working. HV power work can be such a pain.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

I decided to empty the oil, clean the enclosure (had debris in the bottom) and refill with fresh oil. I don’t have any way of vacuum potting the oil. How vital is it? Maybe that was the cause of the failure? The clearances are pretty tight so a trapped bubble is definitely possible. It’s been many months since I last ran the fusor, so I was hoping that soaking this long might have been good enough.

Starting to look back at my old plans of winding my own using the 3D print bobbin…

I think that I’ll focus on figuring out the popping sounds that I hear coming from the multiplier while this last transformer is still working :-)

-Matt
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

So I decided to wind the new coil last night using a 3D printed bobbin. I wound the secondary such that there are two separate coils, center tapped and 180deg out of phase, on the bobbin. Each coil is made up of 5 sections wound with 90 turns each of 27awg Essex ultrashield wire. So, 450 turns for each coil.
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I used my inductance meter (10khz signal) on the primary and my scope on the secondary to “verify” that I did this correctly. Here is the scope shot of the center tap and one of the coils.
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The core is a very large TDK n27 type core.
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Here is my math for what I expect:
Primary Turns = 10
Frequency = 40khz
Vin = 120vdc
Ae = 8.4cm

This gives me a B = 179mT and a step up of 45 times.
120Vin should give me 5400v out.

Edit: This will be submerged in oil. Also, I’ve got the flu so I’ve probably omitted something important :-)
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Richard Hull
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Re: Matt’s Power Supply Upgrade

Post by Richard Hull »

Beautiful work! Isn't it nice to have just a few really valuable electronic instruments to verify your phase arrangement. I am sure you knew about the wire wind direction to get this. I would have wound only two opposite pies about half way and clip lead scope/oscillator test the phase. I'm the guy who would cry at a fully wound failure to phase properly.

What we are sure we know often bites us in th' butt at the end of a job. Best to test and go, test and go, inch-worming to a successful outcome.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Hmmm…Didn’t think about that! That’s what happens when you tinker under the Flu :-)

I had re-read Finn Hammers nice transformer guide, so knew enough that I needed to be 180deg out of phase.

Hopefully this one is the last one. It should be able to handle more than my breaker can support.

-Matt
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Placed the new transformer in its enclosure and soaking in fresh mineral oil. Still have some more connections to make up and bubbles to get rid of before testing it. Any alternatives to vacuum degassing? Not sure I can find a suitable container big enough to fit this in…
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-Matt
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Dennis P Brown
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Re: Matt’s Power Supply Upgrade

Post by Dennis P Brown »

I can't offer any method that is as effective as vacuum degassing, then oil back filling. The very next best method is elevated temp to dry/remove trace water vapor in the dry assembly. Then putting under warm oil. Then, if available, placing this in a sonic cleaner tank to better remove remaining air.

Otherwise, soaking in as warm oil as safe is the only other alternative.

From the look of your very thick spacing, I am sure your x-former will operate fine if allowed to soak in oil for a while.

Your overall transformer work is very professional. Hope you experience no further issues.
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

I’ve been slowly stirring the oil every few hours to loosen bubbles. It’s looking like all of the obvious ones are about gone now, so it’s just trapped air in windings that has me worried. Hopefully me keeping things in the 5-6kV range will help?

I’m thinking I’ll let it soak a few days and then try it out at low voltage and higher current to warm up the windings. Maybe that’ll help?

-Matt
Peter Schmelcher
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Re: Matt’s Power Supply Upgrade

Post by Peter Schmelcher »

Matt I dry 3d filament spools and other things in a pressure cooker. I had to reverse or defeat the pressure safety vent devices and print an adapter to an automotive ac vacuum hose thread. Don't need to run the vacuum pump continuously because I installed a diaphragm isolation value in the hose. System lacks a window to see what is going on inside. Could use a USB camera and some LEDs instead of adding a window.
-Peter
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Emma Black
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Re: Matt’s Power Supply Upgrade

Post by Emma Black »

Matt this new transformer setup looks the business! I hope it performs well. You also have my sympathies, we also have the flu here, get well soon.

You could try adding something that will vibrate and agitate the oil while soaking to help free up the air bubbles, like the things you get for cement.
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Did some initial testing and I’m disappointed.

With my x ray transformer, I’m able to supply 20-30mA at 5kV with a frequency of around 25kHz (startup phase).

With this self made transformer, I’m only seeing around 8-10mA at 5kV.

Shorting the Secondary coils to the center tap, and using my inductance meter at 10kHz on the primary, I see the x ray transformer is showing about 1Ohm. The self made transformer is 2.5Ohm.

I’m no expert on high frequency ferrite, or transformers, but guessing this much higher impedance is the cause.

-Matt
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Quick (will do more measurements later) update:

I decided to go to an 18 turn primary to see if I could increase current (lower turns ratio) and decrease voltage output. This resulted as expected; more current at lower voltage.

I then added a full wave rectifier/capacitor to measure voltage into the multiplier via a fluke 6kV probe. I did this to see if I’m over volting my multiplier (I’m not) to account for the popping noises.

Lastly, I decided to add a series capacitor to resonate with my leakage inductance. This had a very substantial effect.

My leakage inductance is 129uH. Adding 165nF (cde942 capacitors rated for 13Arms) in series with the primary resonates at 34.5kHz. I’m driving the half bridge a little higher at 40kHz (need to experiment some with this).

This caused my current to more than triple from before. Upon ignition, my current used to hit around 7mA. Now it’s 30mA.

My last run was around 12 microns, 57kV and 20mA.

Looks like a series resonant capacitor was the way to go.

Edit: I also got around to running with the multiplier lid off so that I could see what the source of the popping sounds is. I could see strong circulating currents throughout the oil, but no flashes or arcing while the popping noises were occurring.

-Matt
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Decided to upgrade my multiplier container so that I can see what’s going on inside. It’s also a lot easier to get into if I need to.

Also added some rectifiers to the transformer output so that I can measure the output of the transformer to see if I’m over volting my capacitors.
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Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Looks like I might have figured out what my problem is…This whole time I was fixated on the multiplier. Today I started isolating things and found that (disconnected from fusor) I could push up to 70kV without any popping sounds. I reconnected and pumped down the fusor to try again. I began getting the popping noises around 45-50kV despite not running any deuterium. With the grid cold, I could see into the chamber and there were little arcs and flashes jumping from the cathode. Looks like that’s my problem…Short circuit from within the chamber.

Now to figure out why (I’ve been able to push much higher in the past) and how what to do (glow cleaning?) to fix this.

-Matt
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Bob Reite
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Re: Matt’s Power Supply Upgrade

Post by Bob Reite »

Does it look like it's arcing across the insulator inside? Or just flashes from the grid. If the latter, run an air plasma at a low enough voltage so it doesn't arc with enough current to get 500 watts input. Let it run like that for a few hours, or until the chamber is nice and hot, then turn off the HV and allow the chamber to go to a hard vacuum. That should clean things up.

If it's across the insulator, a bake out may help with that. However on my original fusor, which has a lot of hours on it, the ion bombardment changed the ceramic into somewhat a conductor. Doug fabricated an insulator using boron nitride, which can stand the ion bombardment without changes in the insulating qualities.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Hi Bob,

I was just about to update that I’m back to hearing sizzle and popping coming from the multiplier :-(

Something is definitely wrong…My guess is that the mmkp383 capacitors just aren’t what they used to be and are being over voltage internally. Finn got away with it but using an old batch. I’m thinking the new ones don’t.

I’ve got a spare or two sitting around. I’ll try to test one on my 0-5kV power supply to see what voltage they actually fail at.

On the bright side, I managed to get a Hitek xr2000 that looks to be rated for 100kV and 20mA for cheap. I’ll scavenge out the transformer and multiplier to use. Hope this finally solves my power problems.

-Matt
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Okay, so I hooked up one of the spares to my other power supply. I ramped up to 2800v and left it for an hour and didn’t see any problems. So now I’m at a loss for what’s going on. Seems like these capacitors should be good for much more than their 1600v rating and that they shouldn’t be the issue?

Could it be arcing within the chamber causing the multiplier to make the audible noise?

-Matt
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Richard Hull
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Re: Matt’s Power Supply Upgrade

Post by Richard Hull »

if there is any arcing you will see it in the current meter. Analog meters are far to be preferred as they instantly respond to even tiny low current arcs. Most of us use digital meters or worse a multi-ported microcontroller A to D where there is a conversion time and little movement of the digits. You will see a current bump or unsteadiness with arcing. The current changes should follow the arc sounds.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

Yes, the analog meter that I installed on the high side goes berserk during these short circuits. The digital meter on the low side also goes nuts, but shows erroneous data.

I removed the cathode last night and found that the SS tubing used to connect the tungsten wire cathode to the feed through stalk had melted and was going “sparkler” mode. That’s what I’ve been seeing and hearing…_I also shattered the tungsten wire cathode on removal.

Looks like the new upgrades to the PSU have really worked things. I’ll have to come up with a new/beefy cathode now.

-Matt
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

I’ve been using my Bertran to test one of the spare capacitors. So far, I’ve taken it to 3200v for 1 hour without any failures. It’s rated for 1600vdc, so it appears that these probably ARE capable of much more.

Disconnecting the fusor from the PSU, I have been able to push up to 75kV without any popping or anything. Looks like it might have been my grid failing, all along.

-Matt
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Richard Hull
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Re: Matt’s Power Supply Upgrade

Post by Richard Hull »

There are so many failure modes when monkeying around in the area of voltages over 30kv both in air and in various vacuum states. The fusor, in arc conditions, is a local powerful RF source just itchin' to load into any ungrounded or unshielded instrumentation line. Everything to do with the fusor is metal! This metal is usually grounded. Is it any wonder high voltage doesn't play well when pumped into, around and through grounded metal? Or, by the same token, that in air it aids arc conditions as corona creates ion rich conduction paths to nearby grounded metal.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Matt_Gibson
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Re: Matt’s Power Supply Upgrade

Post by Matt_Gibson »

After killing my 901p, arcs and EMF has had me considering running my ground connection out my window and bonding directly to my house ground, next to my meter. My house ground wire is maybe 6 feet away from the window…Some flat ground strap should let me close the window on it and keep the seal happy. Hopefully the utility doesn’t think it suspicious :-)

-Matt
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Dennis P Brown
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Re: Matt’s Power Supply Upgrade

Post by Dennis P Brown »

I cover my pressure gauges with a fine wire mess; ditto for the main vacuum port for the fusor (mainly to protect the turbo from debris but also for the plasma.) This appears to work for protecting the gauges/equipment from the HV plasma. I use a metal water pipe as a master ground point for my entire house (besides the electric company's ground wire) and so this also works for the fusor. I also run independent ground wires to the turbo case and 'leak' valve besides the std ground for the fusor case.
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