Re: Limiting Safety Gap Current

To: tesla-at-pupman-dot-com
Subject: Re: Limiting Safety Gap Current
From: Gary Lau 08-Feb-1999 2148 <lau-at-hdecad.ENET.dec-dot-com> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Tue, 09 Feb 1999 07:06:01 -0700
Approved: twf-at-verinet-dot-com

>Original Poster: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com> 
>
>Malcolm,
>Yes, a perfect inductor doesn't dissipate any power,
>but if you look closesly at my posting you will see
>that I explicitly remarked that with an iron core the
>sucker is now an induction heater. Induction heaters
>DO dissipate power. Lots of it! In the form of heat!
>>
>Fr. Tom McGahee

With the gazillion Amps that would flow through a firing capacitor safety
gap, I believe any iron or ferrite core would saturate.  Or is that the
desired effect?  I'm not clear on how induction heating works.

Even with no added inductor, any cap has some self inductance and a
self-resonant frequency.  It would be good to de-Q that resonance with
some external series resistance.  Better to burn that power off in a
resistor than in dielectric heating.

I'm also not sure I can see any need for a cap safety gap, so long as the
main gap is not set too wide (static) or misses presentations (rotary),
in which case a shunt gap would solve the problem.  I can see no
mechanism for the cap voltage to exceed the main gap voltage, even
considering all sorts of parasitic L's and C's.

Even in the event of a secondary strike to the primary, I would think
that the primary cap impedance would be tiny compared to the secondary
impedance, and not pose any sort of hazard to the cap.  The NST is
another matter however...

Regards,
Gary Lau
Waltham, MA USA