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Re: DC Resonance Charging Advice Sought



Original poster: "Crow Leader by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, August 12, 2003 9:52 AM
Subject: 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.

This seems like a long time. Pretend your tesla coil was completely
harmless. When making adjustments, you'd probably want to wait less than 35
minutes after powering it off to make changes. Unless you're amazingly
patient, it sounds like you might eventually get tired of waiting 35 minutes
and start shorting the caps out yourself. The whole "safety" is then
defeated. Utility company caps are designed to drop to 50 volts or less in 5
minutes. I'm not sure if it's some NEMA standard, or who else uses it, but
it sounds reasonable. Microwave ovens drop to safe voltages in just a few
minutes as well.

KEN

 > 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
 >   >
 >   >
 >   >
 >
 >
 >