Re: synch gap question (fwd)

---------- Forwarded message ----------
Date: Fri, 16 Jan 1998 16:13:23 +0000
From: wysock-at-ttr-dot-com
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: synch gap question (fwd)

> Date:          Fri, 16 Jan 1998 16:01:32 -0700 (MST)
> To:            tesla-at-pupman-dot-com
> Subject:       synch gap question (fwd)
> From:          Tesla List <tesla-at-pupman-dot-com>

> ---------- Forwarded message ----------
> Date: Fri, 16 Jan 1998 08:55:41 PST
> From: Mad Coiler <tesla_coiler-at-hotmail-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: synch gap question
> List members,
>  I have been trying to build a synch gap for my NST coil. My first 
> attempt proved unsucsesful. I couldnt get the synch gap to outperform my 
> static gap.  <snip>
>  One question first: I was following the idea of 120bps, firing once 
> every half cycle (on the peak?). I recently watched a video - I believe 
> it was the 1991 Tesla Symposium (I dont exactly remember what year it 
> was) and Bill Wysock (hope I didnt spell it wrong) gave a lecture on 
> spark gap technology. I remember he said using a synch gap it is 
> important that you not fire on the peak, but instead fire at the 
> 'skirts'. I dont believe there was any explanation givin on the segment 
> I have recorded. So is this why my synch gap isnt working properly? That 
> would mean 240bps, and seems contrary to what others have said to me.
>  To describe the problems I was having.    <snip>   My 
> contacts are small brass acorn nuts - both on the disk and stationary. I 
> think the disk is 8" diameter. I tried putting series static gaps in the 
> circuit too but that made things worse. Maximum output was probably 75% 
> that of with the static gaps. <snip>
> Tristan Stewart

Dear Tristan, all

The paper I gave before ITS was 1991.  Others on the list have 
made many comments about what is the appropriate level of
a.c. power input where a coiler should consider a sync. rot. gap
in place of any kind of series static gap.  I have always liked the
idea of using static gaps with NST's as opposed to a rotary.  In
your post, you did not mention the amount of operating current,
so I have no idea if you are using a single 60 ma. unit or a number
of parallel connected NST's.  I have found, (from personal 
experience,) that I always obtained superior performance from a
sync. rot. gap when I was using a non-saturable core transformer
where the load current was >200 ma.  This implies however, that
a series variable inductance (autotransformer as a series-
connected inductance,) along with an additional autotransformer
(connected as an autotransformer for variable voltage control to
the H.V. transformer input,) be utilized.  There is a symbiotic
relationship here; the two autotransformers, the non-current
limited H.V. transformer, and the DWELL angle of the RSG.  And
this relationship varies from one experimenter's setup and group
of components, to another.

You did not state why you wanted to go from your successful
static gap to a RSG, using a NST (one or more.)   I believe part of
the problem you are seeing is that since the NST(s) have a current
limiting shunt, and since they were designed to work into (more
or less) what you might call a "steady state" non-inductive load
(neon tubing,)  that when you try to use any form of "forced"
timed gap for the tank circuit, the NST(s) (to personify the
situation,) "Don't know how to handle that condition."  

If you are really enamoured with the idea of using an RSG,
make it a high speed non-synchronous-type (where you are using
NST's for the power source.)  You won't exceed the efficiency of a
good static gap design, but you will have the "beauty" of an RSG
running your system.

As for my statements about a sync. rot. gap not firing on the peaks
of each 1/2 sine wave, that comment applies only to the non-
saturable core class of power supply transformers, supplying the
tank circuit with a.c. power.  For example, if you had a pole pig,
rated at 20 Kva, and you current limited its input to say, 12 Kva,
and you "fired" only on the peaks with your sync. rot. gap, you 
would have a lot of wasted input power, and have lost a lot of
"time" not spent charging the tank caps to the highest usable 
coulomb level for any instant of time.  If however, you rotate the
index (dwell) of the firing times of your gap in this instance, to
not fire directly on the sine wave peaks, but only along the rising 
or falling skirts of the sine wave, then you will see more efficient
"power processing" i.e. more a.c. 60 Hz POWER in: more r.f.
current and higher r.f. voltage out.

Bill Wysock
Tesla Technology Research