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

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Sue,

I posted this chart from a simulations awhile back:


Cpri    Ip (peek)       Vs (peek kV)    Streamer Power (W)
130     183             233             666.07
135     124             222             488.42
140     129             220             570.26
145     141             226             620.93
150     167             242             650.85
155     191             252             666.07

Here you can see the dip in primary current that also tends to dip the 
output voltage.  But running at the dip point is the most efficient.  You 
may actually see long sparks with the tuning off but at the expense of much 
more primary current.  Not sure how real these simulations are, but if you 
see that the lowest input current point also produces the best sparks, that 
would be a good thing :-)

Cheers,

        Terry

At 06:58 PM 2/20/2005, you wrote:
> 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