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Re: Fusion Success with Precipitator Power Supply

Posted: Thu Jul 25, 2019 9:13 pm
by Mark Rowley
You definitely can. The DC output it isolated from the line in.

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Jul 26, 2019 1:54 am
by Bob Reite
Ah, I wonder if these were designed to operate with the outputs totally floating, and that grounding one side (no matter which) might stress them. I ordered one to experiment with, once I get my hands on it, I will study the design and see if any special precautions should be made.

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Jul 26, 2019 3:21 am
by ian_krase
Not really practical for those of us who are doomed to live in apartments.

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Aug 09, 2019 2:14 am
by Bob Reite
Well I broke down and bought the "600 Watt 60 KV" version off of Ebay. As far as getting 240 volts. I have been too lazy to run a 240 volt circuit to the attached garage, and if I wind up moving the fusor to "The Train Shed" and remote controlling it like Doug does, I would put the 240 volts out there.

So I had toroid transformer good for 1000 VA, and by connecting the various windings correctly I got a 120 to 230 volt transformer.

Now that I have one of these supplies in hand, I was able to determine that those are four flyback transformers with a built in 1/2 wave diode rectifier. Yes, they are getting away with hooking the HV secondaries in series and the primaries in parallel to drive with a two MOSFET half bridge circuit.

Well, As I suspected, the seller got his "10 mA" rating while it was only putting out 5 KV Best I've been able to get out of it is 2 mA at 25 KV for 50 watts. The voltage regulation stinks! If you leave the output control set where the device is giving 2 mA at 25 KV, and go open circuit, the output voltage will jump to 50 KV. Trying to get to a higher open circuit voltage makes things arc and trip the GFCI outlet. But the power supply does survive the abuse, maybe the GFCI tripping protects it.

Still deciding if I'm just going to "box it up and send it back", or redesign the driver, a full four device driver circuit that would have better regulation.

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Aug 09, 2019 8:26 am
by Mark Rowley
Hi Bob,
That's kinda odd and I'm wondering if your supply has some issues OR it's an specific issue with the 60kV unit. I can easily get 4-5mA at 25kV (even at 30kV for that matter). But this is with the smaller "two flyback" unit that's pictured above and what Finn used in his earlier post. I've never tried for any higher current due to concern of melting my grid.

I have yet to install the 60kV supply but it is here and on the bench. Time permitting I'll give it a run in the next few days. I'll report back once done.

Again, for those new to this subject, almost all of this was presented and explained in Finn's earlier report.

http://www.fusor.net/board/viewtopic.ph ... ore#p77912

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Aug 09, 2019 8:31 am
by Mark Rowley
Bob,
You said your supply was arcing at higher voltages? Where exactly did the arcing occur and did you pot the supply before attempting to go over 20kV (or higher)?

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Aug 09, 2019 4:02 pm
by Richard Hull
I wonder if they just threw two extra flybacks on the same electronics as the two flyback unit??

Richard Hull

Re: Fusion Success with Precipitator Power Supply

Posted: Fri Aug 09, 2019 5:23 pm
by Mark Rowley
There seems to be a few more components on the 60kV version. Here’s a side by side comparison.

Mark Rowley

Re: Fusion Success with Precipitator Power Supply

Posted: Sat Aug 10, 2019 6:47 pm
by Richard Hull
Looks like a lot beefier half bridge transistors in the 60KV unit. Probably just a stronger simple driver circuit, but based on the new 4 flyback load at 60 kv,, as noted by Bob in experiment, it falls on its face. The 60kv unit tends to collapse when working a fusor.

Richard Hull

Re: Fusion Success with Precipitator Power Supply

Posted: Sun Aug 11, 2019 2:59 am
by Mark Rowley
I need a few more details from Bob regarding his conclusion of 2mA at 25kV. Even though I have yet to put the 60kV unit through the paces, his claim seems very off to what I've see so far. What did he use for a load? Did he try to operate his fusor with it? If so, air or Deuterium? Did he employ a ballast resistor or no resistor? Chamber size compared to a 2.75" system? He claimed some arcing took place? details? Corona losses prior to arcing affecting current measurements? More details please. This will help greatly when I install the 60 later next week and make a comparative run with my Fusor. In the meantime I picked up the lesser known 40kV / 10mA supply. This one is similar to the 30kV unit but the flybacks appear about 25% larger than what's on the 30 and 60. I'll post results once I get around to testing it.

What I do agree on is the voltage regulation issue. Voltage output under load and no-load conditions could be wildly different. For example, if you are operating a stable plasma at 15kV and suddenly the plasma extinguished (causing no load) your voltage could instantly jump to 25kV or more (likely a lot more if using the 60). It would be crucial to make sure ones HV feedthrough and leads can withstand the full potential of this type of supply PLUS a healthy safety margin. Although they are comparatively tough, I'm skeptical if they can survive arcing for more than a couple of seconds. Beefing up the HV line and feedthru is clearly one of the tradeoffs for the inexpensive nature of this type of supply. Yes, more work has to go into HV handling, but it's still hundreds of dollars less (and immediately available) than the comparatively unobtainable continuous duty cycle iron cored transformer (or other well known expensive options).

Of course, this is all specific to it's intended use as a power supply for the 2.75" systems. I highly doubt it'd do anything for the classic large spherical fusor.

Bob, do you have any idea what the unmarked IC's are? I'm thinking the 8 pin is an op-amp similar to a LM358D but the unmarked 16 pin is a total mystery.

Mark Rowley