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Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
I have been experimenting with Steve Wards Mini SSTC. The first bridge I built, used the IRFP260, and the coil performed very well! with over 6 inches of spark. However, it only ran off 110v, and I am trying to build a version for the European supply of 240v
I replaced the fets in the bridge with IRFP460`s , and increased the primary turns on my coil to 12 (since the original 4 exploded my half bridge!)
The coil works, with very little heating of the fets, but now I`m only getting 3 inches of arc! I have tried reducing the primary turns, one turn at a time, but all this seems to accomplish is to start heating the fets. I have also tried various sized top loads, but to no avail.
There must be something obvious I`m overlooking here!
The problem must surely be in the half bridge. the IRFP460`s have a higher on resistance than the `260`s, but I would still have expected decent output, on account of the higher voltage.
Should I be using smaller caps on the bridge? They are currently 0.68µF
Banned on 3/17/2009. Registered Member #487
Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617
Try increasing the coupling. Make a primary that is closer to the secondary and if it doesn't arc over after that then raise it till it does then drop it just a tad.
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
Ok will do! The primary is only separated from the secondary by 3 layers of aceatate sheet, I will try raising it a little, since it is right at the bottom of the coil.
Registered Member #1134
Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351
Well that worked a treat! I raised the Primary an inch, and now I`m getting a much more respectable 5+ inches of spark out, so I will keep at it! SSTC`s are odd beasts! Whenever I have built compact SGTC`s I have always ended up having to reduce coupling one way or another!
Banned on 3/17/2009. Registered Member #487
Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617
No problem.
I always did this on mine. I'd have a small gap maybe 1/4" between primary and secondary then raise it to a point just below flash overs. I had an interupted SSTC that could produce 15" sparks with no breakout point, but only after I found the perfect coupling this ay..
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Steve Wards Mini SSTC 240V
