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Re: Chokes too close to primary?
From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Tuesday, September 16, 1997 6:32 PM
To: Tesla List
Subject: Re: Chokes too close to primary?
To: Gary
No -- the only reason we put the power supply (w/chokes) 15 feet away is so
the sparks off the toroid sec dont strike the power supply. I have also
noted sometimes especially with pole xmfrs that too much inductance will
cause a resonant rise as well. We usually just use a 500 turn air core
choke with pole xmfrs and avoid any toroids with 10 turns, etc. We always
put a test gap (with jumper clips) on both sides of the choke especially
during tuning to make sure any harmful transients like your 3 inch long
sparks dont exist.
>
> From: Gary Lau 16-Sep-1997 0936[SMTP:lau-at-hdecad.ENET.dec-dot-com]
> Sent: Tuesday, September 16, 1997 8:46 AM
> To: tesla-at-pupman-dot-com
> Cc: lau-at-hdecad.ENET.dec-dot-com
> Subject: Chokes too close to primary?
>
> Dear Dr. Resonance,
>
> Your recent post reminds me of the unresolved tank-to-gnd arcing problem
> I'm facing and posted several weeks ago. Summarizing, since installing
> a pair of 9mH (30AWG x 2.38"D x 6.75"L air core) chokes, my tank circuit
> wants to arc to any grounded point 3" or less away. Initially the chokes
> were vertically mounted, top end about 5" below my primary. I also
> suspected that the primary could be exciting the chokes (like little
> secondaries) so I moved the xfmr(15K/30mA), bypass caps (600pF), chokes,
> and series R's (3K/50W & damn hot!), 3-4 ft below the primary, orienting
> the chokes horizontally, off axis from primary, and 90 deg from each
> other. No Joy.
>
> I had concluded that having a really effective pair of chokes has
> essentially completely decoupled my tank from the ground reference and
> that voltages like I'm seeing are all a part of the tank's resonant rise.
> My solution has been to simply move things around to keep grounded points
> away from the tank!
>
> Back to the theory that the primary is coupling into the chokes, do you
> really think that they need to be 10-15' distant to avoid coupling?
> Yikes! If so, maybe this is a good reason to consider (well insulated!)
> ferrite torroid chokes, they being less inclined to couple than
solenoids?
>
> How close can you bring a grounded surface to your tank before it arcs?
>
> Regards, Gary Lau
> Waltham, MA
>
> >From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
> >Sent: Monday, September 15, 1997 7:29 PM
> >To: Tesla List
> >Subject: Re: New Testing
> >
> >To: Ed
> >
> >Another possible consideration --- are your high freq RF filter chokes
> >mounted under your primary coil (or within a few feet)? If so they will
> >pick up a high potential RF signal that could blow some components. We
> >also learned this lesson the hard way many years ago. Now we mount all
of
> >our "filter" components in a separate HV power supply box that is
usually
> >10-15 feet away from the oscillator base itself.
> >
> >DR.RESONANCE-at-next-wave-dot-net
>
>
>
> >
> > From: Esondrmn-at-aol-dot-com[SMTP:Esondrmn-at-aol-dot-com]
> > Sent: Monday, September 15, 1997 12:36 PM
> > To: tesla-at-pupman-dot-com
> > Subject: Re: New Testing
> >
> > In a message dated 97-09-13 09:03:10 EDT, you write:
> >
> > << 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. --
> >
> > >>
> > Bert,
> >
> > I now have the static gaps out of the circuit. Thanks for the tip, I
> will
> > reduce the safety gap across the cap to maybe .50 to .75". All I need
> now is
> > some decent weather.
> >
> > Ed Sonderman
>
>