Re: [TCML] Why air-core?

[Michael Twieg <mdt24@xxxxxxxx>]

At one point a group I was with attempted to make a magnifier for a SSTC
using a ferrite core immersed in mineral oil.  It was meant for about 10KW
of power.  At first we had trouble with arcing internally, since we couldn't
get all the air bubbles out of the windings.  We solved that issue, but then
found that the transformer had a lot of self capacitance, creating a self
resonant frequency near our intended frequency of operation, which kind of
killed the whole point of the magnifier.  I think it could be redesigned to
have less capacitance, but we kind of lost interest and went for a more
typical air core magnifier with a lower coupling coefficient.

-Mike

On Sat, Oct 1, 2011 at 10:22 PM, Eric Goodchild <ericgoodchild@xxxxxxxxx>wrote:

> On 10/1/2011 7:16 PM, Gary Lau wrote:
>
>> I was asked a fundamental question about Tesla coils recently.  I _think_
>> I
>> knew the answer, but I'd like to check.
>>
>> A Tesla coils is strictly an air-core transformer.  I said that steel or
>> ferrite cores are not used because:
>> 1) Core saturation would be likely
>> 2) The conductive core would degrade the high voltage standoff capability
>> 3) The coupling with a cored design would be too high
>>
>> Did I get it right?
>>
>> Thanks, Gary Lau
>> MA, USA
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>>
> I strongly agree with 1, core saturation would defiantly be a problem,
> particularly with a DRSSTC. At hundreds of amps peak you would need an air
> gap so big you may as well call it air core... This is how I figure it.
>
> Another thing I may add to that list  is that the size of the core would
> likely be massive if you could manage to get it to not saturate. A core of
> this size would be very unwieldy and heavy.
>
> 2 and 3 almost make logical sense to me.
>
> Eric
>
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