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Solid State
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From: Andrew Chin [SMTP:chinny-at-ozemail-dot-com.au]
Sent: Thursday, March 19, 1998 7:10 AM
To: Tesla List
Subject: Re: Solid State
"Someone else on this list asked a similar question to this one. The reply
below is just a copy of the reply I sent before. BTW, I don't think mylar
would make a good dielectric for Tesla coil use. Mylar apparently has poor
AC characteristics and will probably blow with your first switch on."
I actually thought of doing this at one stage. Running a high voltage
transformer at the resonant frequency on the mains side, such that it will
ring the primary at the same frequency. The problem is that getting a high
voltage transformer to run at the frequencies of a Tesla coil (about 200kHz
for mine), is a feat to be seen. Sure you can try and build your own
transformer, and this would take remarkable engineering skills.
If you're thinking of maybe running a NST at that frequency, you can
forget it. You'll most likely saturate the transformer and it will start
getting hot. I tried this method and could only get the NST to 450Hz!!
There is an alternative scheme that I devised, which involves using
several transformers, and pulse them each in turn. The following diagram
will hopefully explain:
Transformer 1:
__ __ __
| | | | | |
| | | | | |
___| |________________| |_______________| |__________________
Transformer 2:
__ __ __
| | | | | |
| | | | | |
________| |________________| |_______________| |_____________
Transformer 3:
__ __ __
| | | | | |
| | | | | |
_____________| |________________| |_______________| |________
Transformer 4:
__ __ __
| | | | | |
| | | | | |
__________________| |________________| |_______________| |___
Resultant:
__ __ __ __ __ __ __ __ __ __ __ __
| | | | | | | | | | | | | | | | | | | | | | | |
| | | | | | | | | | | | | | | | | | | | | | | |
___| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |_| |__
(excuse the ASCII art. A fixed font might help.)
By doing this, you can keep the frequency to the indvidual transformers
within the tranformers capabilities. You can then combine the outputs
together to get a frequency, in this case, 4 times the frequency of the
transformer. i.e. if you wanted to operate a 200kHz coil, you could get 4
transformers and run each at 50kHz. You can see that this scheme can be
easily expanded to incorporate more transformers.
The critical thing with this method is getting the timing right, and this
usually means a single oscillator running some logic which does the wave
shaping. In the example above I showed pulses for clarity. In practice,
you could do it with a sinewave, and even a squarewave, swinging from
positive to negative. (using H-drive)
I never got around to testing this scheme due to the lack of transformers,
but I have simulated and built the logic circuits to it, and it is flawless.
To get to the point, you really need to get hold of some high frequency,
high voltage transformers, for this method of ringing the primary to work.
Andrew Chin chinny-at-ozemail-dot-com.au
>From: Michael Andrus [SMTP:andrus-at-ccountry-dot-net]
>Sent: Wednesday, March 18, 1998 4:44 PM
>To: tesla-at-pupman-dot-com
>Subject: Solid State
>
>In a tesla circut is it possible to generate the specific frequency that
the secondary resonates at BEFORE the transformer? The reason I ask is not
to build a better mouse trap but to build a oscillator with MOSFET
transistors. These do not come in the high voltage variety but do allow
120v at about 10 amps.
>
> I was wondering if anyone can tell me another use for mylar other than
ballons. I would like to use it as the dielectric for my capicator but I do
not have a good source for it.
>
> Thanks in advance, Michael
Andrus