DRSSTC1 Progress

[sparkydownunder]

Hi Coilers

Just a quick update on my first Tesla Coil.
Its all coming together, and all the key elements have been put together (finally!)
Take a look at the album ive attached, its got all the main bits ive put together.

still got to do:
- wind feedback transformers
- make a breakout point
- wire everything together

Im rather unhappy with my secondary (cracking epoxy and a few minor high spots) so im going to test it at low power but im fully expecting a bang lol

Annnnyways, take a look and let me know what you all think

https://imgur.com/a/CHKne

[Hydron]

Most of it looks good so far, but I do have some questions about the MMC

You've noted that it's 2kV/0.25uF - is this correct, and is that the DC or AC voltage rating? 2kV rating only allows ~200A peak current at 63kHz for a 0.25uF capacitor before going over the voltage limit! If each cap is 2kV with 3 in series giving 6kV then you're looking at more like a 600A limit (set the OCD to 500 or so to play it safe), but it's still not a lot of headroom.

If there are issues with the MMC rating, then one thing to note is that a DRSSTC doesn't need the expensive high pulse current rated CD942 caps - many other polypropylene capacitors have been successfully used.

[Mads Barnkob]

Your secondary coil / topload, primary coil and bridge looks fine. Not any serious flaws that jumps in the eye. Please do provide more details with coil sizes, frequencies and part numbers etc.

The way you made the MMC layout you have some connections close to eachother that are not at the same potential. The leads between one strings capacitor 1 and 2 and is very close to the leads of another strings capacitor 2 and 3, it will properly only be a problem if it sees a high peak voltage that is not shared evenly.

I agree with Hydron that the low peak voltage rating will be a limiting factor, using bricks you should be able to run it at 800-1000 Apeak.

[sparkydownunder]

Hi guys, thanks for the response!

Just to address those issues (very keen eyes on both of you). The IGBTs I have were hand-me-downs from the university only rated at a 180A. So ive undersized the MMC to save some cash and scale it to the IGBTs. Both of them will be upgraded down the line to a much higher rating.

As far as specs go:

Bridge   2x SKM 200GB173D
Bridge supply   1x 450v 8200uf electrolytic (massively oversized) 
Primary coil   Flat, 9 turns ~24.89mH at current tap (7.5ish)
MMC   6kV 0.25uF
Secondary ~2100 turns
Resonant frequency   Around 63 kHz.

Thanks for the feedback guys

[Mads Barnkob]

Do not let the hard switching or pulse hard switching ratings fool you, when we talk about soft switching / ZCS / resonant switching there is some huge advantages in switching speeds and losses that makes us able to really overdrive the current. Hydron pushed 750 Apeak through a SKM200 brick. http://4hv.org/e107_plugins/forum/forum_viewtopic.php?169902.0#post_169917

[Hydron]

Do not let the hard switching or pulse hard switching ratings fool you, when we talk about soft switching / ZCS / resonant switching there is some huge advantages in switching speeds and losses that makes us able to really overdrive the current. Hydron pushed 750 Apeak through a SKM200 brick. http://4hv.org/e107_plugins/forum/forum_viewtopic.php?169902.0#post_169917

That link mentions CM300s, but as Mads said, I ran ~750A peak with SKM200GB125Ds without any issues. The only reason I changed to the CM300s (I had both available) was the theoretical extra headroom if I wanted to push the coil harder.