Re: Top-load altering Q-factor of secondary cct

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Gavin,

On 25 Oct 2005, at 23:03, Tesla list wrote:

> Original poster: Gav D <gdingley@xxxxxxxxx>
>
> Hi Malcolm,
> if I've got this right the top load can increase current flow in the
> top part of the secondary coil, resulting in a higher voltage and
> giving the appearance of a higher Q, but it's just that more current
> is flowing?

 A tricky point since you are adding to the overall capacitance of
the secondary. Q is a measure of the energy loss per cycle/total
energy and it measures the same whichever way you look at it. Note
that in practice, the shape of topload is going to be a major
determinant of just how high a voltage is produced before energy is
bled off by corona. I haven't actually measured the voltages in
disruptive operation so can only conduct thought experiments in that
realm. Marco's research might better enlighten us.
     The measured Q in the case of _some_ secondaries with the
addition of a moderate amount of topload definitely measures higher
than with no topload but adding more beyond a certain point makes it
go back down.

 Would this increased current effect manifest as a measure
> Q based on bandwidth and resonant frequency (Q = f / BW)?

It does exactly that. I am not presently in a position to be able to
quantify the exact causes (e.g. as Gerry suggests I'm sure the change
in frequency and skin and/or proximity effect is a factor also).

I thought
> there may be a trade-off due to the basic Q-factor equation.

Can you explain further please?

Malcolm