SSTC Q's

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

Original poster: "Alan Sharp by way of Terry Fritz <twftesla-at-qwest-dot-net>" <AlanSharp-at-compuserve-dot-com>

>I'm considering building a SSTC.  I know just about nothing on the
>subject, so I need some help.  

try my page:     www.alansharp.co.uk there is a link on the bottom of
my home page to the SSTC web ring.

>First, what kind of voltage/currents are typically used in the primary
>circuit?  I just bought some MOSFETs, rated 500VPk, 12 amps for $6.50 a
>piece; will they work? 

up to 350V DC - and the current depends on the power used but peak currents
can be 4 times higher - or more than average currents.  Your FET's are fine
for
350V working (leaves some headroom) 12A is fine. Start with a primary with
a lot of
turns.

Did I get ripped off?? (I doubt it :-)) -
 I can get them a bit cheaper here from RS Components.
RSWWW-dot-com  UK and international.

>I know I'll need to parallel some even if they are suitable.

Paralleling is not so easy - a simple 4 FET H bridge can deliver 500W - 1KW
or more.

>What sort of drive circuits are used?  I could probably use a 555 timer
>thingy to fire the drive transistors, but there are better ways, right? 

>Do you guys use square or sinusoidal wave drives?

Square waves - keeping switching loses down.  A 555 timer (one of the fast
varieties
can be used)

>What is the tank circuit arrangement?  Is a cap used, or is the primary
>inductor driven straight from the MOSFETs, without a cap.

No Cap - adjust the output frequency to the resonance frequency.

>I've been playing with my new FETs today, and they sure are easier to
>deal with than bipolars! :-)).  I understand that MOSFETs can be
>paralleled with ease (no thermal balancing resistors).  Is this true?

They have their problems - they do need a high drive current to charge
the gate capacitance (1000-10000pF).  Avoid parelleling them - start with
a half bridge then a H Bridge then build the 200MW monster :)

All the best

Alan Sharp UK