Re: [TCML] Voltage Question

["Udo Lenz" <udo_lenz@xxxxxxxxxxxxxx>]

Thank you for the explanation. I wasn't aware of what Les means.

In another post you wrote:

> To produce long streamers, really the coil just needs to
> develop enough voltage to start the breakout, and then be
> able to back that up with plenty of charge (ie a big toroid)
> and enough power to keep the streamers hot and low resistance.
> Therefore you're more likely to find a simple relationship
> from input power * efficiency to arc length.

I find this an intrigueing thought, although it seems a bit extreme.
I can't imagine an endlessly growing streamer given infinte power
but just a certain voltage. I've done some measurement with my drsstc
on the secondary load and preliminary results indicate, that even though
the voltage seems to be there, the load doesn't increase beyond
some level.. What also was interesting to see, that it takes some time
for the load to develop.

Udo

----- Original Message ----- 
From: "Paul Nicholson" <tcml88@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, January 26, 2012 3:19 PM
Subject: Re: [TCML] Voltage Question


> Udo Lenz wrote:
> > I can't resist another nitpick
>
> Please nitpick - devils always lurk in the details...
>
> > For a neglectable top capacitance, you would over estimate
> > the voltage by a factor of pi/2 (i.e. a quarter wave along
> > the secondary).
>
> This is so.    Hence the use of an effective inductance 'Les'
> in the calculation,
>
>   V_top = 2 * pi * F * Les * I_base.
>
> The value of Les is smaller (in a normal coil) than the low
> frequency inductance 'Ldc' to take account of this effect.
>
> Because of the coil's distributed self capacitance, not all
> the current entering the base reaches the top.  Therefore the
> total voltage induced is less than would occur if the current
> was uniform all the way up.
>
> With a large topload, the coil current is nearly uniform and
> Les ~= Ldc.    With very short coils, the 'internal' capacitance
> (between one part of the coil and another) creates circulating
> currents and Les can be larger than Ldc.
>
> JavaTC calculates Les correctly by working out the capacitance
> distribution of the system, then the current distribution at
> the operating frequency, and from that the effective inductance.
>
> I should remark that Les is an attribute of the system as
> a whole (coil + topload + any other sources of capacitive
> loading), not an attribute of the coil itself.
>
> > Why do you think the current measurement approach holds only
> > below breakout?
>
> Because then the loading on the top of the coil (and therefore
> the current distribution) are no longer constants but vary
> with the amount of breakout.
>
> --
> Paul Nicholson
> --
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