David and Roger,
Congrats on building DC powered Tesla Coils! Although a bit more complex,
they are a decided improvement over their AC powered cousins, and are more
fun to play with.
But wait - there's more! If you want to further improve your DC coils, I
recommend you make one further addition to your setups. Namely, add another
pair of gaps to your rotary spark gap (RSG). This allows you to DC resonant
charge your tank cap, then completely disconnect your power supply when your
tank cap discharges into your primary winding.
Picture resonant charging your tank cap to about 2x the DC power supply
voltage. Then carefully disconnect the tank cap from the power supply and
connect it to your primary. Then disconnect the cap from the primary and
reconnect it to the charging circuit. Repeat this cycle indefinitely.
Of course, the rotary spark gaps do the connecting and disconnecting. You
can see that when the tank cap discharges into primary, the DC supply is
completely disconnected and totally unaffected by the discharge. This is
very good.
The second set of gaps allows you to automatically do the power supply
connects and disconnects. These gaps on your RSG should be spaced so they
are aligned half way between first gap alignments. For example, if you have
12 rotary electrodes, they will be spaced 30 degrees apart. Tank cap
charging will occur at rotor angles of 0, 30, 60, 90, 120 etc degrees. Tank
cap discharge into the primary will occur at 15, 45, 75, 105, 135 etc
degrees.
With this arrangement, you can slow your RSG down as much as you want, even
to 1 RPM! If you try this with just a single gap RSG, once the rotor slows
down enough for your charging reactor to saturate, you will get ugly flaming
trailing arcs in your RSG and huge current draws from your power supply -
very bad!
The other big advantage is that your charging reactor only needs to be about
a tenth of a Henry. So it can be air core and easily constructed.
Does this really work? Absolutely! Using 6 MOTS to power a twin 6 inch
diameter Tesla Coil, I got eight foot streamers and the power supply and
de-Qing diodes really appreciated not being shorted every "bang".
I got out of the TC hobby, but I still have the documentation. If you want
more details (diagrams, spread sheet calculations, etc.), send me an email.
I would really like to hear of others trying this scheme.
Steve Young
-----Original Message-----
From: Tesla [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of David Rieben
Sent: Wednesday, August 10, 2016 6:45 AM
To: tesla Coil Mailing List
Subject: [TCML] DC Resonant Coil Questions
Hi all,
I (along with my daughter and her husband) had a chance to visit Roger Smith
(in Ohio) and get the personalized grand tour of his nice sized pole barn
high voltage lab this past Saturday, August 6. Of course, the highlight of
the visit was his huge, pole pig powered DC resonant Tesla coil! Of course
looking at Roger's DC res setup got the wheels to turning in my head about
how I could possibly convert my Green Monster to run DC res instead of
asynch with raw and unfiltered AC strait from my pole pig.
<SNIP)
Thanks,
David
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