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Re: DRSSTC - I think I heard Cross Conduction...



Original poster: "colin heath" <colin.heath4@xxxxxxxxxxxx>

hi sue,
        When I build the bigger H bridge, I have to look into why I can't
use as
much top loading as Steve W. uses. I have enough extra turns available to
get it in tune, but I get smaller sparks, and it draws much more current
:-(.
Sue
 i to have found this with my coil. as well as drawing more current the
problem with noise on the electronics gets much worse!
cheers
colin

----- Original Message -----
From: Tesla list <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, February 21, 2005 4:05 AM
Subject: Re: DRSSTC - I think I heard Cross Conduction...


> Original poster: Sue Gaeta <sgsparky@xxxxxxxxxxx> > > Get used it! It always happens that way. I have blown many 20A MOSFETs to > bits, but I still have the original 10 amp fast blow fuse that I started > out with! > > And everyone thought I was crazy when I said we should be using MOSFETs as > drop in replacement for fuses :-) > > I have replaced all my MOSFETs with IGBTs now. Not that I thought I would > get better performance, but I just wanted to see if burning IGBTs smelled > any different >:] > > I started playing around with my coil again last week, and I added a > 0.186uF cap in series with the primary. It is now officially a DRSSTC. My > tuning was way too high from where I predicted it should have been when I > swept the primary tank arrangement with the signal generator, which was > odd. The interesting thing that I noticed was that a dip in average H > bridge supply current, and an increase in spark length (obvious) coincided > with resonance. Just like a real transmitter! People don't usually talk > about tuning for a dip in supply current in this arena, but I just found > out that it does apply here. Yes, I am pulsing the driver at 100 Hz, but I > am talking about average current. > > When I build the bigger H bridge, I have to look into why I can't use as > much top loading as Steve W. uses. I have enough extra turns available to > get it in tune, but I get smaller sparks, and it draws much more current :-(. > Sue > > I am beefing up the traces, but I don't think anything could stop it once > it lets go. But the breakers and fuses did not trip so the IGBTs blew > themselves out of the circuit very quickly. Good since that really helps > limit damage. I am using the little IGBT as fuses in that case and they > almost worked. Maybe I need smaller IGBTs ;-)) > > Cheers, > > Terry > > > >