So I recently built the microbrute drsstc from EVR and was having pretty good results. I was up to 23in arcs at 350A and 80VAC in on my variac.

I decided to make the breakout point a little longer and pointed upwards a bit more so as to avoid ground strikes. That’s when everything went wrong. Blew an IGBT (60n60 minibricks).

I replaced the bad IGBT, went back to the original breakout point, and then tried again. Blew both IGBTs this time. Thinking that the 60n60s were simply fakes or whatever (got them on eBay for cheap) I then swapped the IGBTs to the “Thunderbolt” IGBTs that EVR sells. I decided to remove the secondary and place a tin can in its place.

Tested at very low power (30vac in from variac), heard the buzzing from the Interruptor, and then blew one of these new and $$$ IGBTs.

Completely at a loss for what on earth could be happening here? I don’t even know where to begin with testing seeing as I only changed the breakout point before all of this started.

Before going into great detail of the system, what could cause these IGBTs to just suddenly begin failing (shorted) at low voltage?

-Matt

Hi all,

So I decided to work on a 7 stage full wave CW for my fusor PSU upgrade and have a question about design. I’ve seen one instance where a commercial multiplier used larger capacity capacitors for the first stage…I think that this would assist with charging the following stages, but don’t understand how to quantify this benefit. Is it worth doing/messing up symmetry (I have severe OCD when it comes to layout:-)) over? Or is it more of a product specific design?

I’m asking because I found that I have just enough 150nF (1600v) capacitors to do this with if it offers some nice benefits. The rest of the multiplier will use 100nF (1600v) capacitors. The 150nF are sized a little larger which will cause some uneven layout…

First stage capacitance would work out to be 75nF and the remaining stages would all be 25nF. If there’s considerable benefit, I’d be able to ignore the asymmetric layout, but if there’s little benefit, I’d rather not. 

Thanks!
Matt

Hi all,

I had a segmented high voltage transformer bobbin 3D printed. I’m having THE WORST time trying to actually wind this thing. The first few layers start off great, but then, somehow/someway, it all just goes to crap. I can’t keep each layer PERFECTLY flat so that the next layer stays flat.

Am I missing something?

Anyone here with some legit skills that I could pay to do this for me? I’ve spent 30 hours and this is as far as I’ve gotten. There’s no way I’m going to succeed in winding each layer flat.



-Matt

Hi everyone,

I recently built a full wave CW multiplier (6 stages) and a hand wound ferrite transformer (20kHz) to power it. I used 6kV 47nF wima FKP1 capacitors (2 in series per stage). The voltage rating should be 72kV if I assume 100% voltage rating of the capacitors. This is running under oil.

So far, I’ve pushed it to -66kV and 11mA to power a fusor. This shouldn’t be stressing it, but I can hear the sounds of popping coming from the multiplier. I’m afraid that I’m hearing the capacitors having punch through events. Each time I hear popping noises, I see my voltage dip. I’ve opened up the multiplier a few times to test the capacitors and see they are still reading within spec…

Anyone here with experience? Are these 6kV capacitors just not rated for 6kV or do I have something fundamentally wrong?

Here are a few pictures of the new, two coil center tapped transformer, the completed multiplier, and the multiplier under construction.

Edit: Forgot to add details of the transformer for completeness:

506 turns per coil and I am now using a 7 turn primary fed by a car amp and a signal generator. Primary voltage is 55vrms. My output calculation going into the multiplier is 506/7*55*1.414 = 5622v. This should be putting around 11kV across each stage which is under the 12kV rating. This is why I’m confused by what sounds like capacitor failure. I’m unable to see through the multiplier container, so am assuming it’s not from arcing between stages/wire/diodes etc.

-Matt

Hi everyone,

I’ve been out of the game for many years, but remember the ucc37322 being the go-to for DRSSTCs…

Here’s what I’m trying to do:

I have a homemade ferrite transformer that I want to drive at 35-40khz. This will feed a full wave CW multiplier (6 stages). I have a cm300dy half bridge that I want to use for this. Would doubling up on ucc37322 (18A total) driven by a TL494 be enough to drive such a large IGBT at 40khz?

I see that everyone has gone t0-220 route. I’m assuming this is to drive these bricks very hard so that max pulsed currents can be used for drsstc use, no? In my case, there aren’t really high pulsed currents needed, as this is for a CW multiplier/ferrite transformer setup.

Thanks!
Matt