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Re: [TCML] (no subject)

The Transformer is 6000vac@1amp ccs . I was waiting to use it on a
amplifyer prodject that has not come along. Ive built other Hf Vhf and Uhf
Amps be for. A friend and I went to chicago to clean out the house of a SK
ham. We found a boat load of Tesla coil parts. 2 working coils. Hv caps up
to 80kv, many door knob caps and motors for rotory spark gap systems. And a
half built 3 feet  Tesla Coil. I entend on finishing his prodject. My
problem is i suck at math, all the formulas in the books drive me nuts. I
can build anything. But aldibra , for get it.Spelling not so good eather.

On Aug 15, 2017 7:42 PM, "Carl Noggle" <cn8@xxxxxxx> wrote:

> Jim, as usual, speaketh the TRVTH.
> An 8kV transformer will charge a capacitor to close to 12 kV, which is
> fine for a Tesla coil.  Your cap should be rated for at least 30kV, since
> it will be charged both positively and negatively, and should have some
> slack on top of that.  That will work for a rectified coil too, since the
> voltage will stay on one side of zero.  My coil runs on 9 kV, with 50kV
> rated caps.  If you go much above 15 kV of operating voltage, you will
> encounter unauthorized arcs, sparks and coronas which will require a new
> level of high voltage art and finesse.
> Excellent advice to build a coil with one NST for starters.
> --- Carl
> On 8/15/2017 10:01 AM, jimlux wrote:
>> On 8/15/17 9:11 AM, Jeff Allen wrote:
>>> Hello All, I have 8000vdc transformer at 1 amp. Do i need to use a
>>> voltage
>>> doubler to get up around 16000v? Can some one explain the differance
>>> useing
>>> ac or dc voltage for the Tesla? Im looking to build a large Tesla and big
>>> arckes. Thanks
>> is it 8kV DC, or AC?  Most transformers put out AC but sometimes they are
>> packaged with an integral rectifier.
>> For a first coil, I'd start with a (iron core) neon sign transformer,
>> build that up and get through all the peculiarities of building a coil.
>> But DC is a bit trickier to use - WIth AC, the circuit is pretty simple -
>> the supply voltage charges a primary capacitor until the spark gap breaks
>> down connecting it to the primary inductor.  That resonant LC is coupled
>> magnetically to the LC secondary circuit, the energy transfers from primary
>> to secondary, the voltage comes up on the secondary and you get sparks.
>> With AC, the supply goes through zero periodically, so the spark gap
>> "turns off" naturally.  With DC, you have to help it along -typically by
>> using a series inductor and a big HV diode - so now, you not only have your
>> HV supply, the primary capacitor and primary inductor, but you have a
>> "charging inductor" and a HV diode (that has to take a pretty abusive
>> environment... no 1N4001 in this application<grin>)
>> with 8kVA, you're also most likely looking at needing a rotary gap -
>> while people have built static gap coils at that power level, it's tricky -
>> probably a blast gap of some sort (high velocity air to "blow out" the
>> spark between half cycles, or at least cool the elecrodes).
>> Hence the suggestion to try a lower power NST based coil with a static
>> gap so you get the "feel" of tuning and stuff on something that won't
>> outright kill out or start a fire or spread shrapnel from a rotary gap or
>> worse if something goes wrong.
>> Or, find someone near you who's built coils before so they can give you
>> advice.
>> You'll also need a suitable primary capacitor - with 8kV you're going to
>> need a healthy HV capacitor that can take the RF current - current
>> techniques are "repurposed" and derated pulse discharge capacitors from
>> companies like Maxwell Labs/General Atomic OR series parallel strings of
>> high current polypropylene dielectric snubber capacitors.
>> Neither of these is cheap at this power level (hundreds of $)
>> Do you want a doubler?  That kind of depends - 8 kV is certainly enough
>> to make sure the spark gap breaks down, but you're also doubling the
>> current. Most AC coils run at 14-15kVrms which is about 20kV peak.  But
>> building a high power doubler is no trivial matter either.
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