Re: Thanks for all the sstc help. one more ...

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi James,

If FETs don't blow from heat, it is getting too much voltage either on the
gate or from drain to source.  Maybe transorbs across both would fix the
problem.  Or, if they blow too, tell you where the problem is.

Cheers,

	Terry

At 02:57 PM 1/9/2002 -0800, you wrote:
>Thats not what i want to hear:(( I WANT TO GO SMALLER.
>my present sstc runs at just over 500khz fet heating
>is not too bad" power levels are 600watts" my poor
>voltage regulator for my pulse transformer and ic gets
>pretty hot though.
>PS> When i blow a fet it is never too hot to touch. It
>may have blown at a lower power level than it was
>rated for but they do not get hot. this is a mystery
>to me, but hay a lot of things R
>               James
>
>--- Tesla list <tesla-at-pupman-dot-com> wrote:
>> Original poster: "Jan Florian Wagner by way of Terry
>> Fritz <twftesla-at-qwest-dot-net>" <jwagner-at-cc.hut.fi>
>> 
>> 
>> > Thanks for all the help with the making of my
>> sstc. I
>> > am very plzed. it preforms well and ill have pics
>> > soon:)) I have been wondering how small of a coil
>> > might be built and still have spark output? and
>> what
>> > kind of control circuit should i use as freq go
>> past
>> > 600khz
>> 
>> 600kHz is pretty much. I'd think that at those
>> frequencies much more power
>> goes to cooking your transistors, than what goes to
>> the streamers.
>> Means, maximally some 10W are practical at those
>> freqs.
>> 
>> Expect of course if you use super fast mosfets and a
>> VERY low impedance
>> gate drive which can give out some ten amps peak, so
>> that mosfets are
>> switched faster than maybe 50ns. But, I'd figure
>> "standard" high
>> power mosfets like IRF740 are too slow for this,
>> they have around 50ns
>> rise and fall times plus maybe 100ns propagation
>> delay (someone please
>> correct me if this is wrong). 
>> 
>> At least in my opinion 400kHz is already on the
>> verge of being too high a
>> frequency. Better go lower freq. And larger
>> secondary (a bucket, maybe?).
>> 
>>  - jan
>> 
>> --
>> *************************************************
>>  high voltage at http://www.hut.fi/~jwagner/tesla
>> 
>> 
>> 
>
>
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