Re: Still working on that Sheppard-Taylor converter

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rob by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rob-at-pythonemproject-dot-com>

Tesla list wrote:
> 

> 
> Well, with kV diodes and kV MosFETs I'm still blowing things up, even
> after severely damping the input inductor.  I think maybe the parts I am
> using are just too fast, so that parasitic inductances are ringing up.
> Also, I am using a UC2710 MosFET driver, which is probably producing an
> extremely fast rise time on the gates.  Its capable of more than 6A
> drive.  Maybe I need to sim with 1nS risetime pulses :)  That will make
> for a very long sim.  Rob.
> 
> --
> -----------------------------
> The Numeric Python EM Project
> 
> www.pythonemproject-dot-com

I found the problem in my PSpice simulation.  I had a 5 ohm resistor
between the pulse source and the gate transformers.  In real life that
resistor is very small.  My the 1kV FETs have much higher gate
capacitance, so I wasn't fully turning them on in the simulation like I
was with the 600V FETs.  

When I went to 0.1 ohm, suddenly, my 1kV MOSFets had 1200V across them. 
Dumb mistake.  I am going to buy a variac, so I can slowly ramp up the
voltage.  It is amazing that a 170V supply can produce such a high
voltage, but my inductor is very high Q, 160uH on a large Amidon iron
powder core, Mu=35.

Off to the electronics supply store!  Rob.

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