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Messages - Spuriosity_

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1
I've found some alternate IGBTs that seem to do a better job for roughly the same amount:
https://au.mouser.com/datasheet/2/205/DS100526A(IXXH40N65B4)-595301.pdf
I'm looking at getting these for their low on resistance and higher pulse current rating compared to the FGA60N60s linked above,
https://www.fairchildsemi.com/datasheets/FG/FGA60N65SMD.pdf

Can anyone advise on which one to go for?

2
Solid state Tesla coils / Re: Mid-Sized SSTC
« on: June 25, 2018, 05:59:07 PM »
In terms of getting the secondary 'good-looking,' it's well worthwhile to build a winding jig out of whatever you have available. Mine was made out of some of my old mecanno, equipped with with a janked-together 555 PWM driver for my crappy motor. I don't know how I would have done it without it (still took 3 nights' work for 1300 turns because the wire kept doubling back on itself)

https://drive.google.com/open?id=1l5J9wIa7gPZUM2VoQrz6x1FAlDG1QWEF

The important parts to it were:
  • Clean the PVC pipe thoroughly, making sure to get rid of any stray fibers or dust particles. I didn't do this well enough, and my final coil has some small hairs jutting out that are very annoying and an arc-over risk. Do not wind next to a carpet like I did.
  • Tape the start of the winding down securely
  • Turn the winder on, keeping pressure on the wires to keep the windings tight together
  • Do not let the wires cross over- undo a frew windings if you have to. Make sure to keep tension on the wire with your fingertips - if it goes loose and the wire expands off the coil form, there is no way to fix it other than unwinding and rewinding.
  • If you have any kind of mechanical counter to keep track of how many windings, definitely use it. It's also possible to estimate based on how long the coil is.
  • When done, tape the end wire down with a full ring of tape
  • Keep the windings in place by applying some kind of lacquer. I bought some of this stuff https://au.rs-online.com/web/p/electronics-varnishes-lacquers/8232640/ and applied 3 coats of it as the thing turned on my winding jig. It's not really necessary to get specialist electronics lacquer, I just grabbed it for extra legit-ness.

3
Thanks for the advice. I'm leaning away from the linked brick IGBT.

The existing coil's primary circuit is an unholy hybrid of an 4-turn speaker-wire cylindrical winding and an 8-turn 8mm copper pipe conical winding - (originally I was planning on using the copper pipe only, but it had insufficient inductance that I improvised around). I'm aware of the issues in using this - including, but not limited to, induction heating of the central part and the general power losses that tend to happen in stranded wire - so I was planning on reworking the whole thing anyway.

SGTC MMC: One series string of 16x Kemet R76TR34704030J 470nF 1.6kV to form a 29.3 nF @ 25.6kV capacitor bank.

What kind of IGBT configuration would be most suitable for this size of coil? I'm currently leaning towards a doubled full-bridge made out of 8 FGA60N65SMD's (around $50 AUD on Mouser) as opposed to two CM300 units which would set me back upwards of $300 AUD. I know the latter is probably a better investment for long-term performance, but I'm willing to risk some silicon shrapnel.

4
Solid state Tesla coils / The hobo's SSTC
« on: June 18, 2018, 04:17:13 PM »
I've recently had the good fortune to crack open a microwave with a solid state 50N322A IGBT half-bridge power supply. I would very much like to cannibalise its larger parts to make some kind of SSTC. Working off http://pdf.datasheetcatalog.com/datasheets/toshiba/GT50N322A.pdf, the switching speeds aren't great, an order of magnitude slower than the DRSSTC grade FGH60T65SHD, but I'm hoping they might be just good enough for a low-power ~100kHz coil (to be achieved using a lot of windings)

I was looking at loneocean's SSTC 1 for inspiration - though my proposed coil will have more than double the windings (and a wider diameter to push up the resonant frequency), the same driver topology should hopefully work.

Before sinking any more thought into this - is this even worth building out, or am I just wasting my time on a project destined for mediocrity?

5
I'm currently in the early stages of designing my first DRSSTC, and am at the tricky point of deciding which IGBTs to order. I've noticed that there is a significant price disparity between the TO-247 packaged IGBTs, like https://au.mouser.com/ProductDetail/IXYS/IXGH48N60A3D1 versus modules like https://www.arrow.com/en/products/ixgn200n60b3/ixys. Reading the datasheets reveals that the current rating for the TO-247 units drops off dramatically with temperature compared to 200n60 module.

Could I get around this by attaching large heat sinks, or should I bite the bullet and get some proper bricks?

The secondary has already been wound (and used successfully on a simple SGTC) - its resonant frequency is 174 kHz, with a 360mm diameter toroid atop a 50 100 mm diameter, 460mm long 1300 turn secondary. Ideally I'd like to have >40cm sparks, but I'm not exactly sure what ball park I need my primary circuitry in to achieve this.

EDIT: 1am brain wrote down the secondary radius rather than diameter. Whoops.

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