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magnifier tests/comparisons (magnifier modeling)


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From:  FutureT [SMTP:FutureT-at-aol-dot-com]
Sent:  Friday, March 13, 1998 11:40 AM
To:  tesla-at-pupman-dot-com
Subject:  magnifier tests/comparisons (magnifier modeling)

Malcolm, Antonio, all,

I measured the "effective" coupling of a magnifier today, and contrary
to my previous findings, I now find the coupling, from a beat period
point of view, to be loose, rather than tight.  This agrees with Antonio's,
and some other folk's views, and with Malcolm's recent findings.  My
apologies.

Tests:

First I set up a small classic TC using k ~ .18, I observed the beat
period to be about 11uS which is about right for the 510kHz coil.  Max
spark length was about 3" - 4".  Pri L ~ 85uH, sec L = 13mH, C = .0015uF,
4 gap series quench sync rotary, powered by 10kV, 23ma OBIT.  Pri 
tapped at 19 turns.  Quenching was poor at around the 3rd or 4th beat
notch.

Next the secondary was moved off to the side to form an extra coil,
and a new 1.5mH secondary was installed at k = .34. The magnifier
primary tap point was left at 19 turns, and the beat period was 
observed to be 17uS, which equates to an effective k of around .11.  
Ringdown freq was about 500kHz.  Quenching was much better at
around the 2nd or 3rd beat notch in magnifier mode.  Spark length
was about the same.

Next the system was set up again as a classic coil at k = .11.  The
beat period was about 17uS, and the quenching was greatly improved,
(2nd notch), perhaps better than the magnifier.  Spark length was still
the same.

Conclusions:

1.  The effective coupling of a magnifier is relatively loose, and is 
is much lower than the measured k of the driver alone.

2.  This loose coupling makes a magnifier relatively easy to quench,
but it may be a little harder to quench for the same "effective k" 
compared with a classic coil (more tests needed here).  In any case,
the magnifier with a k = .34 driver, was much easier to quench than
the classic TC at k = .18. 

3.  The above results explain why spark gaps can quench a maggy
that uses a k = .4 to k = .6 driver, whereas a classic coil with such
a tight coupling cannot be quenched adequately.

4.  Spark output was about the same, classic TC vs, magnifier.

I intend to increase the coupling of the driver to k = .4 to .6 and 
measure the resulting effective coupling based on the observed
beat period.

John Freau