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Re: New Testing




From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Saturday, September 13, 1997 2:08 AM
To: 	Tesla List
Subject: 	Re: New Testing

Tesla List wrote:
> 
> From:   Esondrmn-at-aol-dot-com[SMTP:Esondrmn-at-aol-dot-com]
> Sent:   Wednesday, September 10, 1997 7:55 PM
> To:     tesla-at-poodle.pupman-dot-com
> Subject:        New Testing
> 
> Well, I fired up my coil again tonight after a few months of waiting for the
> replacement Condenser products capacitor.  It arrived a few days ago and was
> installed with a spark gap across it set at about 1.0".  I also recently
> rebuilt my ground system using solid copper flashing to interconnect all the
> ground rods and to the base of the secondary - only maybe 4.0 feet from the
> base of the secondary to the ground system.
> 
> Using a 14.4 kv, 5kva pole pig and a 220 amp lincoln welder with superior
> powerstat for primary power.  I have a switch system set up to switch in
> resistor elements in parallel with the welder.  All switches off is 22 ohms
> in parallel with the welder and all switches on is 3.3 ohms in parallel with
> the welder.  I set the welder on low and the rotary on low speed.
> 
> When I first powered it up, the primary current in to the pole pig was about
> 12 amps.  The gaps would only fire erratically even at full variac voltage.
>  I tried switching in more resistive load in parallel with the welder and the
> gaps almost quit firing altogether with all elements on - about 3.3 ohms.  I
> unplugged the resistive element bank so the welder was on it's own.  As I
> increased the variac voltage, the gaps started firing erratically again and
> the spark gap across the main (.025 mfd) cap started firing.  Someone said
> this would be very loud and they are right, no mistaking if it is firing or
> not.
> 
> I tried different tap settings on the primary and did not have much luck.
>  Still can't get the gaps to fire smoothly.  The coil is trying to tell me
> something and I just don't seem to get it.  I have been having problems with
> this system for the last year, every since I rewired all the primary
> interconnects by replacing the wire (two pieces of RG213 in parallel) with
> 3/8" copper tubing.  This coil used to run very well and has produced 80"
> discharges.
> 
> I thought maybe the RG213 high voltage feed lines to the coil maybe shorting
> internally but I should see high primary current draw if that is the case.  I
> have checked all the primary wiring probably a dozen times and can't find a
> problem.  I am ready to take all the copper tubing back out and rewire all
> the primary interconnects with wire again.  I have three static gaps in
> series with the rotary gap.  The coil originally ran fine with these in the
> circuit and I thought it would help quenching - should I pull them out?  They
> are set at .030" each.
> 
> After I shut the system down for the night, I checked the rotary gap
> carefully and found the gap between the stainless steel acorn nuts on the
> polycarb disc and the fixed (2) tungsten electrodes to be a bit wider than I
> would like.  The disc doesn't run perfectly true so I need a bit more gap
> than I would like.  The total was probably about .150 to .200".  I closed it
> down as close as possible without it hitting.  The total gap now is probably
> .100" plus the three .030 static gaps for maybe .190" total.  Will the system
> be this sensitive to gap distance setting?
> 
> Anyone have any ideas?
> 
> Thanks,  Ed Sonderman


Ed,

If the rotary is firing only erratically, this isn't a symptom of 
improper primary tuning. If the protection gap across the cap is firing
at a 1" setting, you have a significant problem with gap firing. Until
you identify the problem, you may want to reduce your safety gap setting
a bit, since breakdown of a 1" gap represents considerably more than 25
KV AC. The combination of the rotary and the static gaps is apparently
resulting on too high an effective breakdown voltage. In effect, you're
"missing" more presentations than "hitting". Because of the high speed
air-flow around the rotary electrodes, a rotary gap's breakdown voltage
will be significantly higher than for an equivalent static gap. 

Now that you've tightenned up the gap spacing on your rotary, also try
temporarily removing the series gaps and run only off the rotary, and
try running at a mechanical breakrate of at least 360 - 480 BPS so that
you get at least 3 - 4 presentations per half cycle. By reducing the gap
spacing, you should arrive at a point where your system runs smoothly
without the safety gaps firing. You can then gradually increase the
setting via the series gaps until you're just below the point where
erratic firing (or safety gap firing) begins.  Depending on ballast
settings (particularly with no damping resistors across your welder) you
can get really horrendous transient conditions (4 - 6X the incoming 14.4
KV) which won't take out your pig, but can take out your cap.  

See if this helps at all, and the best of luck to you Ed!

- Bert H. --