Re: alternate spark gap design (fwd)

---------- Forwarded message ----------
Date: Tue, 7 Jul 1998 09:10:07 EDT
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: alternate spark gap design (fwd)

>In a message dated 98-07-07 02:18:44 EDT, you write:

<< ---------- Forwarded message ----------
> Date: Sun, 5 Jul 1998 20:30:46 -0600
> From: David Dean <deano-at-corridor-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: alternate spark gap design
> Let me bounce this off you-
> Sec. of HV trans      RSG1     RSG2     primary of TC
> (--------------------------> <--------> <-------------)
> (                                    l                     )
> (                                    l                      )
> (                                 ===                    )
> (                  tank Cap.     l                       )
 >(                                     l                       )
> (______________________l_____________)
> [NOTE: I tried to straighten the diagram out, as it suffered from 
>  tab to space translation problems -- Chip ]
> Assuming RSG1 and RSG2 disks are coaxially mounted
> on a single shaft, have eight electrodes each(45deg. apart),
> and disks are offset 22.5deg. so that they fire alternately-
> Possible advantages-
>Reduced power consumption due to elimination of short circuit
> conditions across HV trans while cap discharges
> Improved quenching of RSG2 as no tendency to power arc (no ac applied
> during this phase)
> Less noise getting back into power supply due to better isolation
> Any thoughts?
  >> snip


I considered this idea at one time also. You want to disconnect
the transformer just before the gap fires, then re-connect it after the
firing to begin charging for the next gap firing?  This "isolating-gap"
would have to be of a special design to give a long *on* time, and
a short *off* time, and may be difficult to constuct, although I didn't
really think through the design too much.

This extra gap introduces extra losses,
and the necessary time interval during disconnecting and re-connecting
the transformer will reduce the available power to the system.

However, in a resonant charging system, the phase shift between the
current and voltage causes the current to be low at the time the gap
fires, so the transformer effectively isn't *fully* shorted when the gap

Even in a non-resonant charging system in which the phase shift
may not be optimal, the input inductive ballast limits the current
during the gap firing, minimizing the losses.  In addition, the
duration of the transformer short is very short, further reducing
the losses.  I once calculated the transformer losses that occur
during gap shorting, and it was quite low, something like 1% or so,
and will vary with the TC design, I don't really remember the exact
figure.  In any case the losses seem low enough that it probably 
wouldn't pay to build the isolating gap.  But if you do build it, it will
be an interesting challenge.

Objectional power arcing does not occur in a properly designed Tesla 
coil. The RF anti-kickback feature would be nice, but typical filters
can do the job.

Good luck with your gap project.  I'm glad to see you're searching
for new ways of doing things.  It is that spirit that will advance the
coiling art.

John Freau