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Re: Rotaries and Neons (fwd)
---------- Forwarded message ----------
Date: Fri, 7 Aug 98 10:48:15 EDT
From: Gary Lau 07-Aug-1998 1012 <lau-at-hdecad.ENET.dec-dot-com>
To: tesla-at-pupman-dot-com
Subject: Re: Rotaries and Neons (fwd)
From: "Robert W. Stephens" <rwstephens-at-headwaters-dot-com>
...<snip>...
>
>John, Malcolm, All,
>
>OBIT's and the 30 mA type NST's seem to be very fragile and
>intolerant of even the slightest electrical abuse. FYI, I once
>connected a 10 kV -at- 23 mA OBIT to a non-sync, variable speed rotary break
>with no other components involved except the necessary spans of about 12
>inches of HV wiring between the two devices. The OBIT died a rapid
>death, not even surviving a full 30 seconds!
>
>If OBIT's and NST's seem to die just lookin' at 'em, perhaps the best
>protection device might be a black bag to put over them so you can't
>look at 'em.
>
>Just thinking aloud now FWIW, perhaps one could try interconnecting the
>power supply transformer to the rest of the system with that special
>suppression core spark plug wire that is now commonly used in almost
>all high-energy automotive ignition systems. It might provide enough
>damping of what must be very HF voltage spikes occuring in the
>OBIT/NST circuit. Perhaps if that proves effective, a length of such
>wire could be wound around a PVC former ala an air cored choke.
>Comments welcomed.
>Robert W. Stephens
Robert,
Your obvervation of the death (aka obit.;-) of your OBIT seems timely,
as my previous post suggested NST's may not like being run without a neon
tube load to limit their Vout. (I'm just repeating this from other
posts, I've not actually researched the V-I characteristics of neon tubes.)
Perhaps this is the mechanism that killed your OBIT, since they are
intended to operate strictly with a continuous spark load, not open
circuited. Not much we can do about it beyond the black bag if this is
the case!
As to using resistive spark plug wire, I doubt this has any advantage
over using discrete series resistors. IMO, an RC filter is most
effective, and the use of any inductors (like coiling the resistive spark
plug wire on a PVC former) just creates additional, unwanted resonances.
There is recent speculation that just the inductance of long wires between
the xfmr and main gap may be harmful.
Regards,
Gary Lau
Waltham, MA USA