Re: [TCML] design idea

[<lightningfor@xxxxxxxxxxxxxxxxxxxxxx>]

Thanks Steve,
I appreciate the feed back.
My reason for asking relates back to the big VTTC coils I have been
developing.
Basically, the 10kv that I am applying to the tank is not enough to give
me the arc length I need.
I figured that if I fed the 10kv into the primary of the Ferrite
transformer I could use the stepped up voltage of the secondary to put
accross the tank circuit.
I am experienting with a drive circuit on the grid of the valve to drive
the ferrite with...

I also like the fact that one side of the tank can be grounded (as you
mentioned)...

I am really wishing I had started with IGBT's instead of valves!!! and may
still have to go that way yet... We will see.
The big problem I am having at the moment is my drive circuit seems to
suffer badly (has a fit) every time there is a mismatch of tuning with any
of the tuned stages. My first attempt did not have any feedback from
primary or secondary into the frequency generating part of the circuit, so
I will re design and see if I get better results.
One observation is that the valve seems to "feed back" out of tune energy
into the circuit... where as IGBT's etc don't appear to do this as badly...

Any feed back welcome...

Carlos


On Sat, 4 Feb 2012 01:01:19 -0600, Steve Ward <steve.ward@xxxxxxxxx>
wrote:
> Hi Carlos,
> 
> This works just fine, and i have done similar things before, and plan
> on doing this in the future.  What it does for you is allows impedance
> matching between a low voltage bridge that is low impedance, and a
> tank circuit that might be more economical to build at a higher
> impedance.  But, if you do the engineering, you will find that adding
> such a transformer in there is not going to really help the efficiency
> (though if done properly, it wont hurt noticably either).
> 
> So sure, it can work, but i suggest thinking about *why* you would add
> such a transformer.  My reasons were to combine multiple H-bridge
> drives, and to conveniently alter my drive impedance (so i could run
> more volts on the bridge at less current, so same power but less
> Silicon conduction loss) to better match the capacitors i had
> available.  The cost is of course, you have added a transformer and
> its losses.  Though, one distinct benefit i see is that it allows you
> to directly RF ground your tank circuit providing good robustness to
> primary strikes (though you gotta make sure your transformer's
> insulation is good!).
> 
> Thats how i see it, anyway.
> 
> Steve Ward
> 
> On Fri, Jan 27, 2012 at 1:21 AM,  <lightningfor@xxxxxxxxxxxxxxxxxxxxxx>
> wrote:
>> Hi All,
>> I have an idea on an electronic tesla coil that I am thinking about
>> playing with, and I'm looking for feedback.
>> This may not be a new Idea, but I haven't seen it before...
>>
>> The basic concept is to drive the primary tank circuit with a ferrite
>> transformer...
>> So you would have the typical HF driver circuit with a pair of big
IGBTs
>> or similar on the end, driving the primary of a suitable ferrite
>> transformer at the correct frequency.
>> The secondary of the ferrite transformer would step the voltage up,
>> providing HV and HF to drive the tank of the tesla coil...
>>
>> I am not looking for a better way to do things, just a different way.
>>
>> As far as I can understand, this would work, but I am looking for
>> feedback...  been done before,why not, potential problems, potential
>> advantages, dissadvantages etc.
>>
>> Carlos
>>
>>
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