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series RSG gaps (fwd)




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From:  Edward J. Wingate [SMTP:ewing7-at-frontiernet-dot-net]
Sent:  Monday, February 16, 1998 4:15 PM
To:  Tesla List
Subject:  Re: series RSG gaps (fwd)

Tesla List wrote:
> 
> ---------- Forwarded message ----------
> Date: Fri, 13 Feb 1998 13:47:44 -0700
> From: Bill Lemieux <gomez-at-netherworld-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: series RSG gaps

> My desire for many series gaps was to reduce the average power
> dissipated in each gap and thus reduce electrode erosion.  Electrode
> replacement on this device will be non-trivial, as they are being
> pressed into place with an interference fit for safety.
> 
> Any thoughts?  Has anyone every used more than eight gaps in series on a
> rotary series gap?  I know that many folks here have used 4 - 8 gaps in
> series on RSG's on their larger machines.
> 
> System info:
> 
> (this is what I'd class as a medium-large coil, running at ~10kVA,
> generating strikes of 12+ ft)
> 
> supply is ~15KV under full "charging" load, and we are avoiding
> resonant rise charging for the moment.  Gap is across transformer.
> 
> tranny is custom-built, 12kVA, 15kV -at- 800mA, 220v pri., internally
> current limited, built-in toroidal RF choke, single bushing.
> 
> cap is 0.1uF
> 
> electrodes are 0.5" W/Cu "alloy".
> 
> rotor speed is (will be) 3600 RPM.
> 
> electrode circle is about 10", thus the surface or "passing" speed is
> about 160 feet/sec.
> 
> Spacing can probably be maintained safely down to .005" - .01", but I
> wouldn't care to try it much smaller than that, given the cost of
> replacing the parts if it crashes.
> 
> -Gomez

Gomez,

I am currently running a 12 gap series rotary on my magnifier system and
plan to build a 24 gap sometime in the not too distant future, in fact
my current gap has the necessary mounting holes to mount the extra
stationary electrodes for a 24 gap system. Both the stationary
electrodes and the rotor studs are 1/4" pure tungsten. The standard gap
spacing is .020" with a 14400 volt pole transformer. I used a 1/2 HP,
10,000 RPM universal (AC/DC) motor and run this gap at 7000 to 8000 RPM
in service on my magnifier. Regular runs of 4 minutes at 10 KW are no
problem with this system.

BTW, if the copper/tungsten electrodes you are using are of the "alloy"
used for conventional EDM, you'll find that the material erodes rather
quickly and leaves black deposits on the electrode surfaces in the
process. I have used EDM rod in the past and was very disappointed with
the wear resistance compared to pure tungsten rod.

Safe Coiling to You,

Ed Wingate