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Re: Optimal Quenching Tests
Tesla List wrote:
>
> Subscriber: bert.hickman-at-aquila-dot-com Sat Jan 4 21:54:49 1997
> Date: Sat, 04 Jan 1997 19:34:26 -0800
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Optimal Quenching Tests
>
> Hi all!
>
> I had a few more thoughts on quenching after answering John Freau's post
> today.
>
> The bottom line:
> Existing methods for estimating proper quenching time predict
> excessively long quench times.
>
> Why:
> We can define "ideal quench" as the point at which we have transferred
> all the energy we can from the primary to the secondary. We let the
> one-way primary->secondary transfer go to completion, but prevent the
> reverse from happening. However, quenching too early leaves some energy
> stranded in the primary.
Actually, by quenching too early there is no energy actually in the
primary circuit at all, it is open. The magnetic energy collapsing back
in on the primary is just lost in space. It never goes back to ES energy
in the resonant capacitor. The energy collapsing back into the resonator
does indeed find use and rings up the secondary quite normally, but with
less energy than if the collapsing magnetic energy had been regenerated
in the primary system. As a matter of fact, the energy for this single
first arc is the most magnetic energy that the system will ever see in a
single sweep even if allowed to ring for the proper quench period. All
other primary magnetic sweeps would be of lesser energy. It is the
secondary which can't fully utilize this inital huge magnetic energy
pulse, requiring a "fill time" to achieve maximum output. A sort of
inductive inertia, if you will.
Richard Hull, TCBOR
Quench time, k, and Fo are inextricably
> intertwined.
>
> The current method uses k and Fo to compute optimal "dwell":
>
> Toptimum = 1/(2*Fo*k)
>
> However, this does not take into consideration the impact of gap losses.
> During the time the primary-to-secondary energy transfer is taking
> place, we are also losing significant energy through gap dissipation.
>
> This means that the first notch of minimal primary energy actually
> occurs significantly earlier than predicted by the above calculation.
> After some further analysis, I conclude that the actual quenchtimes
> should be adjusted by a factored of 80% [for k <= 0.18] or 85% [for k =
> 0.22 - 0.28]. This reconciles certain quenchtime measurements I'd made
> on both my 6" and 10" coils which showed earlier than predicted times
> for minimum primary energy.
>
> Example (for 10" coil):
> Fo = 90.4 kHz
> k=0.209
> Predicted Toptimum = 1/(2*90400*0.209) = 26.5 uSec
> Adjusted Toptimum = 0.85*Predicted Toptimum = 22.5 uSec.
>
> FWIW.
>
> Safe coiling to you!
>
> -- Bert --
Bert,
As I get the H2 Thyratron on line for variable dwell, I should be able
to tell whether attempts to calculate the dwell time are close or not for
the production of longest spark. I am assuming you are probably in the
ball park, though.
Richard Hull, TCBOR