Re: DC power

["Tesla list" <tesla-at-pupman-dot-com>]

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

Chris,

Good for you - DC is fun to experiment with!  One suggestion.  Do NOT charge
your tank cap directly from your DC supply.  This is very hard on the tank
cap and the DC filter caps.  Roughly half the charging energy gets
dissipated in the resistance of the circuit, i.e. the wiring and the caps
themselves.  Adding resistors between the filter and tank cap reduces
stress, but again, you end up wasting half the energy in that resistor.

Instead, charge your tank cap through your primary, then discharge it to
ground through your primary.  This is much more efficient.  Might as well
put the charging energy into your coil instead of heating and stressing
components.

As far as resonant charging, you only need 20 Henry or so to do the job, as
long as you keep the BPS above about 300 BPS.  Below that, it will power-arc
when the reactor saturates.  A couple of MOT secondaries in series will
work.
--Steve

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, February 28, 2002 12:09 PM
Subject: DC power


> Original poster: "Chris Swinson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <exxos-at-cps-games.co.uk>
>
> Hi all,
>
> I've been trying to work out a normal Tesla system but converting AC from
> the NST to DC. This basically works but with some problems which have left
> me a bit clueless.
>
> The first tests were done with a "out of sync" spark gap. To explain
better
> this spark gap is like a double throw switch. First the DC supply arc
across
> a gap to the tank cap. then that arc stops and the gap moves on and
connects
> the tank cap to the primary ( as normal ).  Then as the gaps move around
the
> DC supply is then connected back to the tank cap and so on...
>
> That basically works but where as before I could gain almost 20" with AC I
> can only hit about 4" with this set-up. I made the "charging" gaps as
close
> as possible to make sure there was as little loss as possible across the
> gaps. Which does seem to help. I did try a fixed contact to short the
supply
> to the tank gap but building this proved to be a lot harder so I had to
keep
> a spark gap here.
>
> I have talked to a few people and I was put onto DC resonate charging from
> richie B's website. This looked good but the large inductor needed is a
bit
> impossible as I worked it out to 1600H, or 200H at probable best. I read
> this as apparently you can't short 2 capacitors out and get them to
charge.
> This seems a little strange since the DC smoothing cap is 2MFD so it
should
> charge the small tank cap easily. But so it seems I was wrong to think
> this...
>
> Today I soldered a bucket load of resistors between the 2 capacitors as
this
> seemed to be plan B.  Its hard to say if it helped or not but with a lot
of
> messing around I could maybe hit 6". It seems best to leave the charging
> gaps across the resistors, though the resistors don't really seem to help
> that much. I have 200K between them, which according to calculation they
> should be 660K.  I am not sure if adding more resistance will help matters
> much. my thinking is that 200K will give about 50ma at 15KV or so which is
> what my NST was giving out.
>
> I now am a little lost to what to try next.  my only ideas which probably
> wont help much but...
>
> 1) use actual contacting gaps to short the DC supply to the tank cap.
> 2) the voltage might be lower due to the load of the smoothing cap.
> 3) try lower and higher resistors.
> 4) change tank cap value.
>
> I did try half size tank cap but that worked very bad, only about 1" spark
> then.  I might try a higher value tank cap, double value, but it worked
fine
> with that value on AC so it should be about right for DC power also. The
odd
> thing is that the primary tap has moved inwards half since running from
DC.
> Rotary speeds are a nightmare with DC.
>
> One good thing which has come out of it is the spark can go really high
> pitch and starts to become more flame like than sparks. I noticed this
with
> a car ignition coil driver that it sparks all over the place at one
> frequency but as it was turned up it turned into 1 flame like arc. Very
> interesting and when the Tesla coil rotary gap runs at a high speed I see
> this happening also. It also looks like it gains a extra inch or 2 in
> length. It does however start to pulse the sparks on and off rather than a
> constant arc.  I would love to push the gap further but it will probably
fly
> apart as my construction skills are not to great. But at least I have had
> something new to watch despite the lower power....... anyone got any
> suggestions apart from go back to AC :-) ?
>
>
> Chris
>
>
>
>
>
>