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First time SSTC build, advice needed

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Andrew H

Sat Dec 29 2007, 06:43PM

Registered Member #1198 Joined: Sat Dec 29 2007, 05:39AM
Location: Seattle, WA
Posts: 21

I am currently planning out my first SSTC build (incidentally my first TC of any kind). Four years ago, during my freshman year of college, I first became fascinated by TC of all kinds. I started working on a medium sized SGTC (6â€x20â€ secondary, 12kV 60mA NST) but never finished it. As I read more I became more and more interested in solid state TCs.

As I build up parts for my conventional TC I also started collecting high power MOSFETs and IGBTs. After I lost interest (and school consumed more of my time) I boxed up all my parts and stored them in my parentsâ€™ garage and in the closet of my old room. Now that I am close to graduating they have handed down an ultimatum that I need to take my electronic and TC parts or I am in danger of having it thrown out. When I went to start organizing the mess of parts over the winter break it rekindled my interest in SSTCs and I started to relearn what I had forgotten.

Here are the specs for the conventional SSTC I am planning on building in the near future:

Physical specifications:
Primary : two to six turns (as needed) of thick Cu wire (likely 10 gage or so) wound on a section of 6.5â€ PVC pipe
Secondary: 4.5â€x18â€ with 30 AWG magnet wire
Top-load: 3â€x12â€ flexible Al dryer duct

Power Section:
Half (or maybe full, see some of my questions below) of IRFP460 MOSFETs switching rectified 120VAC mains

Controller:
I plan on ripping off Steve Wardâ€™s Mini SSTC http://www.stevehv.4hv.org/SSTC5.htm

I have most of the parts already; the only things that I need to order are a small transformer for the logic power supply and the 30 AWG wire. Almost everything I know about electronics comes from reading various SSTC sites and part datasheets. I have a reasonable understanding of how simple controllers, like the one I am planning on using, operate. My hope is that by starting simple Iâ€™ll develop a better understanding of the control circuitry and drive requirements of large transistors. My goal is to scale up the classic SSTC design until I am conformable with basic power electronics and move on to bigger silicon and DRSSTCs.

I have a few questions regarding my planned SSTC:

1. Should I start with a smaller secondary (either length or overall dimensions)? It seems to me that a secondary of the size I proposed will allow me to ramp up the power before I have to build a new secondary but isnâ€™t too big for a small SSTC.
2. Should I start off with just a half bridge or should I go straight to the full bridge? Are there any additional difficulties (besides more parts) that a full bridge presents compared to a half bridge?
3. Should I use a voltage doubler? I have parts (a diode with a sufficient rating and a few 3300uF/350V inverter grade electrolytic capacitors)? The MOSFETs I have can handle the higher voltage but what advantage does that provide (and is it worth the trouble for a first time SSTCer)?

Thanks for the help.

~Andrew

J. Aaron Holmes

Sat Dec 29 2007, 09:13PM

Registered Member #477 Joined: Tue Jun 20 2006, 11:51PM
Location: Seattle, WA
Posts: 546

Hi Andrew! Welcome aboard! Great to see another Seattle-area Tesla coil enthusiast show up here.

...well, that's about it

Haven't build any SSTCs myself, so I'll make this fairly pointless post as brief as possible!

Cheers,
Aaron, N7OE

cbfull

Sat Dec 29 2007, 09:15PM

Registered Member #187 Joined: Thu Feb 16 2006, 02:54PM
Location: Central Ohio
Posts: 140

I have a couple of suggestions I'll share. If you want to oversize your secondary in anticipation of some unknown future enhancements, by all means that is up to you. Personally, I would design the secondary size around the ability of the circuit that will be powering it. If I wanted to do something different in the future, I would wind another secondary. For me, it also seems to give each individual project a lot of character.

I've only built each circuit (half and full H-bridge) one time to drive a flyback, and I would say that if you have the parts and the motivation, go for full bridge.

Just my own thoughts.

Andrew H

Fri Jan 04 2008, 04:10AM

Registered Member #1198 Joined: Sat Dec 29 2007, 05:39AM
Location: Seattle, WA
Posts: 21

I've finished ordering parts and they all *should* be in the mail (hopefully. between Christmas and New Years is a bad time to order parts). I also started construction with what I have already. So far I've only started the topload. It's about 3" x 13" made from Al dryer duct wrapped in Al tape. I'm going to two standard pie pans and some thick cardboard to finish out the middle.

Here are a couple of pictures:

1199419335 1198 FT1630 Topload On Tripod

1199419335 1198 FT1630 Topload Wrapping Finished

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