# Re: Vortex gap loss measurements

```Hi Antonio,

On 4 Sep 00, at 12:35, Tesla list wrote:

> Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>
>
> Tesla list wrote:
>
> > Original poster: "Malcolm Watts" <M.J.Watts-at-massey.ac.nz>
>
> > The linear decrement of a ringing RLC circuit which has a gap
> > in series with it was discovered by Stone circa 1914. The
> > Corums mention it in their literature but unfortunately never
> > went on to use the information in their modelling. The linear
> > decrement is entirely due to the gap characteristics. An RLC
> > circuit by itself produces only a logarithmic decrement. This
> > clearly shows that modelling the gap as a resistancwe does not
> > work. You cannot apply the classic time constant equations to
> > this situation. The gap is dissipative but that is where the
> > similarities with resistance end. I analysed this and wrote a
> > note on it several years ago. It is important to note
> > (ultimate pedantry) that you *cannot* ascribe a value for Q to
> > the primary if the primary includes a gap. You can compare
> > various primaries with each other by comparing the ringdown
> > slope (gentler is obviously better).
>
> Note that unless the primary losses are very high, you can
> approximate exp(-a*t) as 1-a*t with great precision for the
> time used for complete energy transfer to the secondary (the
> intial value and the first derivative fot t=0 are identical).
> The transfer takes just a few cycles, and modeling the gap as a linear
> resistor during this time, if the main difference is that the decay
> is linear and not exponential, doesn't make significant difference.
> ("a" would be Rgap/(2*Lprimary) if you consider only the primary
> circuit. Considering the secondary, there are two time constants
> in the system, a compliated function of the element values and
> losses in the entire circuit.)
>
> Antonio Carlos M. de Queiroz

A couple of years ago I mocked up a couple of bench circuits,
one using a pair of diodes to simulate the gap and another
using pure resistance tailored so that the ringdown amplitudes
started identically. Some tailoring of values in the diode
circuit was needed to obtain a linear ringdown as observed
using a real gap (I obtained both log and antilog with various
other values). I found a clear deviation occurring by the
second peak of ring. While it wasn't much in voltage terms it
is worth noting that primary energy is proportional to V^2
rather than V so energy differences were significant. I think
John Freau's results are at least indicative and point in a
definite direction.

In my most humble opinion.
Malcolm

```