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Re: Continued Problems (fwd)
---------- Forwarded message ----------
Date: Fri, 1 May 1998 04:08:42 -0600
From: "D.C. Cox" <DR.RESONANCE-at-next-wave-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Continued Problems (fwd)
to: Ed
First, try replacing the entire primary with some scrap wire like #10 AWG
-- keep it in a flat spiral -- no inverted V's. I think you are
overcoupling and this can really produce some very destructive standing
waves the reflect back into your primary system. Second, for a test,
disconnect your entire primary oscillator from your HV transformer and hook
up a simple climbing arc with some scrap #12 AWG in the form of a 24 inch
high V. Now test your power supply with the climbing arc to be sure you
are getting the correct current control -- note and record carefully your
primary current readings. Reconnect your oscillator and run the system and
also record your primary current readings. Any major differences here
would indicate a destructive resonance pattern. The destructive popping
sound you are hearing might be a failure of your current limiting system to
properly limit the peak recharge current -- it could be as high as 300 peak
amps for short time periods and your spark gap begins to look like a short
circuit that will not quench properly. It is important to verify you
actually have proper current control (1) and (2) you are not overcoupled.
Never, ever use coax as a hot to ground normal transmission line for 60 Hz
HV currents from a pole xmfr. Eliminate the coax for a short time and just
use some 12 or 14 AWG suspended on a few glass soda bottles for these
tests. This will eliminate the possibly of blum line resonance as the
contributing culprit. Last, and I'm sure you know this by now but it bears
repeating -- be sure you have a very good ground on the bottom of your
secondary coil -- with these values you should have no less and 2 ought
welding cable from the base of your sec coil to your dedicated ground. Any
HV resonant rise here will produce hundreds of kilovolts and blow the caps
in your primary very easily.
Hope this information is of assistance.
DR.RESONANCE-at-next-wave-dot-net
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Continued Problems (fwd)
> Date: Wednesday, April 29, 1998 12:39 PM
>
>
>
> ---------- Forwarded message ----------
> Date: Wed, 29 Apr 1998 12:52:12 EDT
> From: Esondrmn <Esondrmn-at-aol-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Continued Problems
>
> Sorry, this is going to be a long one.
>
> I fired up my 6" coil last night for the first time this year. I am
still
> having problems.
>
> Quick overview: Secondary 6" dia, 991 turns of #22 awg, 29.1 mh. Primary
3/8"
> copper tubing wound in a 30 degree saucer shape, 3/8" spacing between
turns,
> I.D. 8", O.D. 26", 5.25" tall, 14 turns total, 88 uh. Secondary is
mounted
> so the lowest turn is 3.5" up from the first turn of the primary - right
at
> about turn 7 or 8. Mark Rzeszotarski (sure hope I got that right Mark)
> calculated the coupling to be about .167, so I wouldn't think it is
coupled
> too tightly. Best tune is at turn 11.75 with a 5" x 40" toroid.
>
> Capacitor is a .025 uf, 15 kv Condenser Products unit with a spark gap
mounted
> directly across it made of #10 solid copper wire with 1.0" dia loops on
the
> ends. Gap is set to 5/8". Power is from a 5 kva 14.4 kv pole pig and is
> supplied across the spark gap which consists of a rotary with a static
gap in
> series with it. Current is limited to the pole pig via a Miller
Thunderbolt
> welder with an adjustable resistor stack in series with the welder.
>
> I built this coil about two years ago and scaled things up gradually from
neon
> sign transformer to the pole pig. I was quite happy with the
performance,
> getting nice white hot bolts up to 80" long at about 8 kva input. Then
the
> first C. P. cap blew up. I replaced it and within not too long, lost the
> second one. Several folks on this list suggested I install a spark gap
across
> the cap unless I have lots of money - which I don't so I did. Now, I
can't
> input much power without firing the cap safety gap. Last fall, last time
I
> had this coil fired up, Malcolm, Dr. Cox and a few other helpful folks
> suggested I had a bad case of 60 hz resonance. I have to ask a question
here
> - are there systems out there that can be run at say 10 kva with 15 kv in
and
> not fire a .25" safety gap across the cap?
>
> For this run, I made a few modifications in the primary set up. I use
RG-213
> for H.V. feed lines to the coil and I stripped all the shields off these
leads
> - at the suggestion of Dr. Cox. I also moved the welder and resistive
ballast
> from the input side of the variac to the output (between the variac and
the
> pole pig primary). I didn't expect this to fix the problem but thought
it
> might be worth a try. The primary H.V. comes from the pig, goes to a
safety
> gap, each lead goes to two 300 ohm 100 watt resistors in series ( total
of 600
> ohms in each leg) then out to the coil via about 20 feet of RG - 213,
again
> with the copper braid stripped off. The net result of these changes is
> basically zero. The coil still performs as it did before. Maybe someone
can
> give me some advice based on the symptoms here.
>
> With the welder set at minimum current (maximum inductance I would guess)
and
> the series resistance at 4.8 ohms, I can only open up the variac to about
75%
> and the cap safety gap fires. Primary pole pig current is only 8 amps.
Wife
> with her ear to the welder says it growls. In all these tests the asynch
> rotory is running at about 400 to 500 bps.
>
> Changing the welder setting to maximum current works much better. I can
now
> decrease the series resistance to 4.0 ohms, open the variac to full
voltage,
> primary current is now 16 amps and the cap safety gap does not fire.
From
> this set up, decreasing the series resistance any further or increasing
the
> rotary speed causes the safety gap to fire.
>
> I tried running with resistive ballast only and can get the primary
current up
> to 16 amps but I get a real nasty popping sound from the rotary - sounds
like
> something is getting hurt and makes you want to turn it down quickly.
>
> So, where do I go from here? Do I still have 60 hz resonance? Is this
> caused by the welder, and if so how do I fix it? The primary
interconnections
> are made with 3/8" copper tubing. Malcolm suggested maybe the Q of the
> primary is too high. I could try replacing the copper tubing
interconnections
> with wire as the coil was originally built - which should add resistance
and
> reduce the Q.
>
> What if I use resistive ballast only - what is the destructive sounding
> popping noises coming from the rotary? The rotary consists of 8
electrodes on
> a .50" thick lexan disc, 10" diameter (I think) with one set of
stationary
> electrodes and a R.Q. static gap in series that is electrically folder in
half
> which would be three .028 gaps in series and in parallel with three more.
>
> Ideas and suggestions would be most welcome.
>
> Ed Sonderman