RE: Zener SSTC?

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

Original poster: "Peter Reid" <peter-at-reidconsulting-dot-com.au> 

Chris,

I don't believe zeners would work at all for TC operation, especially in
the Tank Circuit. I'll explain my reasoning.

Zeners diodes have a forward and reverse voltage drop. The forward one
is what is specified. Ie a 5v6 has a forward voltage of about 5.6v
before it starts to conduct current (ie it clamps the voltage). It has a
reverse voltage drop of about 0.6v just like a normal diode. Using a
zener in a tank circuit wouldn't work for quite a few reasons.

Firstly the fact that it has a reverse voltage of 0.6v means that the
diode will actually clamp the ringing, which is used in the energy
transfer process. Basically It would look like a short circuit for all
negative going voltage waves.

Secondly, A spark gap lets the voltage build up, to the set level before
It conducts, however (unlike a zener) once it starts conducting the
voltage across the gap gets very low (close to 0v). (A zener would still
have its forward drop across it.) Resulting in practically no energy
being transferred across it, and though the tank circuit.

Thirdly, I am sure finding a zener that has a forward voltage drop of
say 12,000V and a peak current handling capability in the 100's of amps
probably doesn't exist. Well not within our budgets anyway!.

Fourthly, Assuming there was 30mA RMS flowing though a zener that's got
a forward voltage of 10,000v that's over 300W RMS being dissipated in
the diode. So the losses associated with a zener would FAR outweigh any
losses in a spark gap type system!.

Hope this helps a bit.


Regards

Peter Reid

Webpage: http://tesla.reidconsulting-dot-com.au
Email: peter-at-reidconsulting-dot-com.au



-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, 16 January 2004 12:03 PM
To: tesla-at-pupman-dot-com
Subject: Zener SSTC?

Original poster: Chris Roberts <quezacotl_14000000000000-at-yahoo-dot-com>

Hi everybody,
We all know that a conventional tesla coil uses a spark gap that fires
and
switches the current whenever the voltage builds high enough, but has
anybody ever thought about using zener diodes to replace the spark gap?
Zeners do the exact same thing, but allow you to fire more reliably,
(wouldn't have to worry much about misfires) and I would think that they

wouldn't have as many losses related to them either. So has anybody
thought
about making a "conventional" coil (tank capacitor, primary, etc.) but
replacing the sparkgap with zeners? You could also get away with using a

really low voltage since you don't need it to break the air gap. Mabye a

simpler OLTC? Would you be able to get zeners rated for that kind of
thing?
Anybody else think that this could work?


-Chris