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Re: Low Voltage Primary

Hi Max,

	If I left the cores in, it would be "just another transformer" where the
step up is controlled by the ratio of the windings.  However, with the
cores removed, I can reach much higher voltages through the resonant rise
effects of a Tesla coil where the step up is controlled by SQRT(Ls/Lp) (a
much higher value).  With the cores still in, a GM coil will only get 3 to
4 inch sparks if it is really driven hard.  But running them as Tesla coils
without the cores, allows 13.25 inch arcs which is 4 times longer.  Also,
at very high voltages (~200kV) the steel cores will saturate and eat up the
energy.  The neat thing is that the vacuum impregnated epoxy cores are
designed for extreme environments which allows them to withstand these
tremendous voltages (for a while at least).

Cheers,

	Terry


At 11:26 PM 12/20/1999 +0000, you wrote:
>Wouldn't it be better to leave the cores in. OK it wouldn't really be a
>TC but surely it would work better.
>
>Tesla List wrote:
>> 
>> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>> 
>> Hi Ross,
>> 
>>         I think it will work fine theoretically.  I have taken GM ignition 
>coils
>> and removed the iron cores so that I can run them as true Tesla coils
>> (single shot) and have obtained 13.25 inch sparks from them.  These have a
>> few hundred primary turns and "a lot" of secondary turns.
>> 
>> http://www.pupman-dot-com/listarchives/1998/November/msg00694.html
>> 
>> You may want to search the archives at www.pupman-dot-com for "GMHEICSLR"
>> 
>> These are very similar to what you propose for low frequency (10kHz), low
>> voltage (1500 V) coils.  However, be very cautious!!  I originally started
>> the GM coil project to make a simple "beginner's coil".  However, the low
>> frequency makes these ignition-coil Tesla coils pack a vicious shock if you
>> touch them!!  It became obvious that the shock was far too much for a
>> beginner to play with and it may be in the lethal range.  Low frequency
>> coils are really nasty shock wise and do not have that "you won't feel it"
>> advantage.  I "tested" it at 2 inch arcs and it really hit me!!  A 13 inch
>> arc would probably send me through the wall if it didn't kill me first (2.5
>> joules).
>> 
>> So there is nothing wrong with low frequency, low voltage Tesla coils
>> theoretically and they have been demonstrated.  However, don't touch them!!
>> 
>> Cheers,
>> 
>>         Terry
>>         Still holding the GMHEICSLR at 13.25 inches. :-))
>> 
>> At 07:10 PM 07/21/2002 -0500, you wrote:
>> >
>> >       Hi all,
>> >
>> >       I am interested in using low voltages for the tank circut.  If one 
>were
>> >to use a 240V tank circut, one would save the cost of transformers and
>> >caps, not to mention putting immense amounts of current through the
>> >primary coil.  (all this stemmed from reading a paragraph about "it
>> >ain't the volts but the amps that matters").  However, plugging numbers
>> >into wintesla gave some disappoiting numbers:  since the capacitance of
>> >the main cap would need to be around 230 uF, the primary's resonating
>> >frequency is very low, around 1.7 kHz.  Using standard 1/4 wavelength
>> >calculations, this gives a secondary amounting to 13000 or so turns
>> >(wintesla).  After admitting that a spark gap will not be easily
>> >constructed (I have a few ideas, ranging from ionized gas to statues of
>> >Buddha) My question is:  Is it possible to use the recommended 600-1000
>> >turns and still get the coil in good tune since the 1/4 wavelength idea
>> >has be disproven?  Anyone have any ideas?   Keep in mind that my
>> >knowledge of coiling is sparse at best.
>> >
>> >       Thanks,
>> >       Ross
>> >
>
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