Optimal Quenching Tests

To: tesla-at-pupman-dot-com
Subject: Optimal Quenching Tests
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
Date: Sat, 04 Jan 1997 19:34:26 -0800
Subscriber: bert.hickman-at-aquila-dot-com Sat Jan 4 21:54:49 1997

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. 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 --