[Prev][Next][Index][Thread]

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
> 
>