Re: tesla coil current

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Chris the great" <downnessisgoingup-at-hotmail-dot-com> 

I want to!
Perhaps it's because I am young.  And stupid.

However keep in mind you are a fairly large resistive load, which means 2 
things- less current, and more internal heating from I2R losses!  Yay!




>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: tesla coil current
>Date: Thu, 06 Nov 2003 16:21:10 -0700
>
>Original poster: John <fireba8104-at-yahoo-dot-com>
>
>Hi Bert,
>It makes sense. I believe it was Tesla that first noticed the high current 
>produced by some of his coils. Plus taking into account resonant voltage 
>rise with a ,somewhat, stable resistance the current has to increase, well 
>in most cases.The only thing I don't get is why current is left out the TC 
>explanations, It should be included since it does affect performance as 
>with resistance. After reading Bert's post does anyone want to try out the 
>skin affect? I'm not.
>Cheers,
>John
>P.S I saw the article "Making Small Change Smaller" in pop sci.Cool.
>
>
>Tesla list <tesla-at-pupman-dot-com> wrote:
>Original poster: Bert Hickman
>
>John,
>
>The situation is actually quite a bit more complex. Even though the
>"average" secondary current may be fairly low, the peak current that's
>available in a moderately sized disruptive system can be in the range of an
>ampere to tens of amperes depending on the circumstances.
>
>First, there are the current pulses which transfer charge from the toroid
>into the leader channel and into growing streamers. These pulses are an
>essential consequence of streamer growth, and although they are of fairly
>short duration (10's of nanoseconds), they have peak currents of 3-10
>amperes in a medium sized coil with a moderately large toroid. And, once a
>conductive leader has formed, there is a reactive displacement current
>which flows from the toroid into (and out of) the leader's self-capacitance
>at the operating frequency of the coil. This displacement current may be an
>ampere or two for a disruptive coil operating with a peak output voltage of
>250 - 400 kV.
>
>However, the current peaks that occur during a power arc to ground can be
>much higher. You've undoubtedly noticed that power arcs which connect
>between the topload and a solid ground are considerably brighter and
>noisier than free air streamers. Once the secondary rings up to peak
>voltage, most of the energy that originated in the primary tank cap (bang
>size = 0.5*Cp*(V^2)) is transferred to the topload and secondary
>self-capacitance. In an efficiently designed system, the peak secondary
>energy can be more than 85% of the initial primary bang size. If the
>topload is then suddenly discharged to ground, virtually all of the
>secondary's stored energy may be dissipated within a high current spark in
>only a few hundred nanoseconds.
>
>For example, let's take a coil that delivers a peak output voltage of 350
>kV into an "effective" secondary/toroid capacitance of 40 pF. I've measured
>actual discharge times of power arcs to ground of ~500 nSec or less for a
>10" coil - let's use a 500 nSec discharge time for this example. At peak
>voltage, the charge in the secondary/toroid system will be Q = CV or 14
>microcoulombs, and the overall secondary electrostatic energy will be ~2.5
>joules. When this charge is removed by a power arc to ground that lasts
>~500 nSec, the resulting "average peak" current will be dQ/dt or about 28
>amperes. Since the waveform is actually a high frequency oscillation with a
>damped exponential envelope, the peak current is considerably higher.
>
>Although YMMV, you can see how the peak currents available from even a
>moderately sized system can be much greater than 10's of milliamperes. You
>can also begin to see why you don't want to be in the path ! of a power
>arc... and why there are significant risks associated with doing "sparks to
>the fingers" tricks. :^)
>
>Best regards,
>
>-- Bert --
>--
>--------------------------------------------------------------------
>We specialize in UNIQUE items! Coins shrunk by Ultrastrong Fields,
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>
>
>
>Tesla list wrote:
>
> >Original poster: John
> >Hi Paul,
> >So a good guess for my ,almost, 3 inch coil would be at least 500uA
> >Cheers,
> >John
> >Tesla list wrote:
> >Original poster: "Paul Marshall"
> >This is going to sound very ambiguous but TESLA coils are totally
> >different animals. They seem to have a minimum required current and a max
> >limit as far a! s what a particular diameter coil will process. For instance
> >my 4" coil would take a maximum of 6 kW. Anything above that and I arced
> >out or flashed over. Below 800 w it was a poor performer. Coupling also
> >seems to be a big part of the equation. I have found also that a coil with
> >an aspect ratio of 3.5 to 1 seems to be the most effiiciant. My 4" coil
> >would step up the primary voltage about 22.5 times (Determined through
> >experimentation). I figure I was getting about 450,000v off the secondary
> >at 250kHz. I got 60" streamers at 6kW. If my coupling was tight I would
> >guess with the losses I probably was getting close to 10 mA.
> >
> >Paul S. Marshall
> >
> >
> > >From: "Tesla list"
> > >To: tesla-at-pupman-dot-com
> >Subject: tesla coil current
> >Date: Tue, 04 Nov 2003 08:07:33 -0700
> >Original poster: John
> >
> >Hello all,
> >I was wondering if any one could give a reasonable appro! ximation on how
> >much current a 3" medium 2kw TC can deliver.
> >Cheers,
> >John
> >
> >.
>
>