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RE: DC Resonance Charging Advice Sought



Original poster: "Dave Kyle by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dave-at-kyleusa-dot-com>

Thanks for the feedback. Yours is the first advice I have seen that suggests
the sizing of the smoothing caps. I admit the smoothing caps value was
pretty much determined by finding a good deal on eBay and you may be right
that it is over kill (pun intended) in this application.

To be honest the DC supply scares me to death which is probably a good
thing. Obviously it is certain death to contact almost any part of it while
it is on with or without the caps. My main concern is to safe the caps after
operation to ensure inadvertent contact does not result in tragedy.

I have bleeder resisters (two 100 megaohm 3 watt -at- 15KV in parallel) in
place on each cap that take the smoothing caps with a full charge to safe
values in about 35 minutes.

R*C=T  50,000,000 * .000,007 = 350
Estimated full discharge =6*T    6 * 350 = 2100 seconds
2100 seconds / 60 = 35 minutes

I made the resistors redundant to get the value down and should one fail
ensure discharge will still occur, albeit more slowly. This was the one of
the critical elements I checked during my initial testing this weekend.

I can easily reduce the capacitance by half should testing show it is
unnecessary but I think this will only be a false sense of security since
the two remaining caps will still present nearly the same danger as four.
The key point is to ensure they are always safely discharged after use which
I think I have done.

=========================================
Dave Kyle
Austin, TX USA
Email: dave-at-kyleusa-dot-com


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, August 11, 2003 10:39 PM
To: tesla-at-pupman-dot-com
Subject: Re: DC Resonance Charging Advice Sought

Original poster: "S & J Young by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>

Dave,

I will comment on the need for PFCs.  I found they did not help at all with
my DC supply.  The reason I believe is because the filtering capacitance
gets reflected back as a much higher value across the primary, and so PFC is
already in place.

By the way, the 7 uF smoothing capacitor is highly dangerous and much more
than you need.  The smoothing cap need only be about ten times your tank
capacitance.
--Steve Y.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, August 11, 2003 12:12 AM
Subject: DC Resonance Charging Advice Sought


  > Original poster: "Dave Kyle by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<dave-at-kyleusa-dot-com>
  >
  > Several months ago after being inspired by Steve Conner's very impressive
DC
  > coil http://www.scopeboy-dot-com/tesla/index.html I started my own DC coil
  > project. I was drawn to the very elegant power control permitted by DC
  > resonance charging. Richie Burnett's site offers an excellent explanation
  > and provided the designs rules that I have followed
  > http://www.richieburnett.co.uk/dcreschg.html#resonant. Of course for the
  > ultimate expression of DC resonance charging one only needs to look at
Greg
  > Leyh's incredible Electrum http://www.lod-dot-org/index.html.
  >
  > I have now completed and tested to 8KVDC (without load) the DC power
supply
  > which can be seen here:
  > http://home.austin.rr-dot-com/dkyle/images/temp/dc_tesla_ps.jpg. For scale
the
  > base disk is two feet across. You will note the very large black power
  > transformer, full wave rectifier and de-Qing circuit, smoothing
capacitors
  > with safety bleeders and grey charging inductor.
  >
  > Specifications are as follows:
  > 4.700KVAC 775VA transformer (6.65KVDC rectified)
  > 7uf -at- 10KVDC of smoothing capacitors
  > 20Henry -at- 15KVDC inductor
  >
  > Under construction:
  > ..02uf -at- 20KVDC cap
  > 0 to 500bps RSG
  > 4 inch x 25 inch secondary with 1400 turns of #26 gauge wire
  > 6x24 inch toroid
  > 15 turn primary (tuned at 11 turns)
  >
  > Advice needed on the following:
  >
  > 1.) I have yet to resolve the system grounding. Is it advisable to ground
  > the center point of the main transformer for safety (like an NST)? Or
would
  > it be better to simply ground the negative side of the DC power supply?
Or
  > let it all float and just ground the secondary?
  >
  > 2.) I am assuming this transformer is not shunted (current limited) but
  > short of dismantling it how can I tell? DC resonance charging is self
  > current limiting so that will not be an issue but I would like pull
current
  > slightly higher than the transformer's rating.
  >
  > 3.) Assuming the transformer is not shunted would there be any benefit to
  > adding PFC caps?
  >
  > 4.) I have noticed in some of the very few DC coils documented on the net
  > that a clamp diode and air inductor are sometimes added to the charging
  > circuit presumably to protect the supply and caps from over voltage and
  > transients. Can anyone comment on the need for this?
  >
  > Dave
  >
  > =========================================
  > Dave Kyle
  > Austin, TX USA
  > Email: dave-at-kyleusa-dot-com
  >
  >
  >