RE: Sold state IGBT disruptive coil spark gap idea

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Again,

First, all the current readings in today's scope pictures are off by 
a factor of ten.  Everywhere where the scope says 200A/div is really 
20A/div.  I set the calibration number wrong on the current probe.  I 
put a note in the file too now.

I took some more readings and ran some numbers and all the times, 
energies, and power levels work out so "everything is under control" :o))

I thought this would happen...  I almost put in the diode originally 
but I was trying to get away with it :o)  The SIDACs are staying on 
very long (many microseconds) even with a current reversal.  They 
stay shorted just like a "real" spark gap...  That shorts out the 
capacitor and takes all the power out of the gate drive circuit.  The 
circuit keeps turning off every cycle and is burning up all the 
energy thus the poor efficiency...

So, it should just need a say 1N5918 diode between the transorb and 
the capacitor to trap the voltage in the gate drive circuit 
regardless of what the SIDACs are doing.  Just a 12 cent part so no 
big deal at all...

I will make the change and retest tomorrow.

Cheers,

        Terry



> Hi,
>
> I got the parts today and built up the circuit.  I tested it out and 
> the charging circuit for the gate drive is not working right.  Does 
> not look like anything serious, just have to figure it out.  I put 
> my notes here:
>
> http://hot-streamer.com/temp/Sidac-Gap-2.pdf
>
> Sorry, it turned out at 1.8MB with all the pictures...
>
> Cheers,
>
>         Terry
>
>
>
>
> > Hi All,
> >
> > I was up late last night working on an idea for an IGBT replacement 
> > for a conventional coil spark gap.  I woke right up at 2PM this 
> > afternoon (semi-retired people can do that :O)))  and started 
> > getting some parts and wrote a paper up on it here:
> >
> > http://hot-streamer.com/temp/Sidac-Gap-1.pdf
> >
> > It is not super cheap, but not insanely expensive either.  Might be 
> > great for lower voltage MOT systems with E-bay big IGBTs...
> >
> > There has been ZERO real testing so don't get over excited ;-))
> >
> > It basically uses IGBTs fired by strings of SIDACs.  Each section 
> > should be fully independent and they can be put in series as needed 
> > for any voltage.  One could "tap" the string for various power 
> > levels.  Power losses seem very pleasant.
> >
> > It will take some real world testing to see if and how well it 
> > works, but the things seems sound.  It is an easy and simple 
> > circuit that hopefully not much can go wrong with :o))
> >
> > Parts on order...
> >
> > Cheers,
> >
> >         Terry